What's up guys, Rouge-9 here and I'm back with some more Rainbow 6 siege. As you know, I prioritize my videos based on viewer demand and up this time, the bain of Thatcher's existence "Fookin' laser sights" Exactly. And apparently he doesn't think too much of them at all. So yes, we'll be looking at Light Amplification by Stimulated Emission of Radiation and yes, that's what LASER actually stands for, look, you've learned something already.
So, laser sights in Rainbow 6 Siege, "are they any good?" You ask Well, in order to be able to answer that we need to get a precise understanding of the benefits they deliver, as well as any potential drawbacks As always guys, if you trust me implicitly and you really don't care how I came to my conclusions skip forward to 4:23 now. Otherwise, stick around for a quick insight into the tests I conducted As we know from the in game description, the purpose of the laser sight is to increase your hipfire accuracy. So I suppose the best way to test this is to take a variety of different weapons and shoot them at a blank wall with both the laser sight attached and without it and see what difference it makes. And as you can see by this example here it definitely does make a difference, but more importantly notice how all of the shots without exception fall perfectly within the targeting reticle on screen and this is great news for me, because it might just mean that I don't have to stand here for five minutes with every gun, twice over shooting at a blank wall to gather my data I can just use the targeting reticle as a reliable indicator for hipfire accuracy instead.
But experience experimenting in Rainbow 6 Siege has shown me we shouldn't always rely on the results from individual samples so I went ahead and expanded this test to also a sub-machine gun, a shotgun and a pistol. And good news everyone. In all cases the targeting reticle did in fact prove to be a reliable indicator for hipfire accuracy. Excellent, and with this knowledge it now becomes a simple task to take screenshots of various weapons in various different states, standing still, walking shooting, and walking and shooting at the same time In order to be able to determine hipfire accuracy Running these tests, it quickly became clear to me that attaching the laser sight will always reduce your hip fire spread by 25%, no matter what gun you're using or what state you're in and while I was at it I
thought I might as well take these tests one step further and try to figure out
the movement and shooting accuracy penalty for each gun is there a fixed
multiplier that applies to all guns to increase the spread when walking or
shooting? Of course there isn't even though some weapons of the same
type, handle in the same way, like for example the C8, type 89, and 552 commando
others like the M249 and the 6P41 don't The general rule of thumb is that
smaller weapons like SMGs and pistols have tighter spreads, while larger guns
machine guns, shotguns, DMR's have larger spreads with the gap in
between filled by the assault rifles.
But as for the multipliers, in the 21 cases I
examined the walking multiplier range between 1.88 And 3.17 Times the standing still spread. Shooting multipliers were between
2.7 And 7.3 And the shooting plus walking multiplier ranged from 4.6 To 10.05. And to complicate things even more for some
weapons the walking spread was smaller than the full auto shooting spread, while
for others it was reversed. The bottom line here is that these spread
multipliers can vary widely from gun to gun but you can trust the targeting
reticle and that's at least something and now back to the benefit of the laser
sight 25% in spread reduction that's pretty good, and with the laser side it's
different than the grips or the muzzle adaptors.
I mean for those you always
have to make a choice do you want one type of benefit or another there is
always an opportunity cost. For the laser sight, there is no such thing it's either
you pick it, or you don't. Okay yes there's the cost of unlocking
it the first time, but come on you play one game and you've got that. So the only
reason that someone might not pick the laser sight is that it makes you more
visible to the enemy.
But does it though? Let's explore, and actually I might as
well make this discussion a part of conclusion, so welcome back if you're
rejoining us here the benefit of the laser sight is a 25% reduction in
hipfire spread and I will now take a closer look at the reason why players
might not choose to run a laser sight. The laser sight can potentially give
your position away in two different ways: number one the enemy might spot the
reflection of your sight, and number two if you shine the laser straight into
their eyes they will see a red glow, who would have thought? Going by the number
of comments I've seen on forums as well as in the comments section of my channel,
there are a significant number of players who are worried by these factors,
but there are a few reasons why I think that this disadvantage is actually much
smaller than you think first off as I already mentioned in my
video on suppressors Rainbow six siege is a game where in most matches stealth
is not really a viable tactic for very long the noise you make while moving can
easily give you away both the attackers and defenders have access to remote
cameras, plus there are kill cams and players on either team can talk to each
other, so keeping your position hidden becomes increasingly difficult as a
match progresses. With these factors in mind I think that any worries about
whether or not your laser pointer will get you spotted are already somewhat
misplaced. But before I wrap up let's also consider the two different ways in
which the laser can be seen by the enemy.
I mean, number two they can see the red
glow if they're looking at you and you're aiming at their head this
"disadvantage" and I'm making air-quote gestures here is completely irrelevant
since by the time they realize that you're aiming a laser sight at their
head the killcam replay will already be starting for them. That is unless you go
full potato just as you're pulling the trigger. And what about number one
spotting the reflection of your laser sure, I guess this could potentially
happen but how likely is it really that in the heat of battle with explosions
and gunfire going off all around the place, someone is going to spot a tiny
red dot zipping across the wall in front of them and not only do they need to see
the dot, they then need to realize that it belongs to an enemy as opposed to a
friend and then they need to guess your location based on that information and
then take you out. Given all the other much more
reliable methods of detecting enemies in this game I believe that the chance of
you dying because the enemy spotted your laser sight is negligibly low you need a
lot of bad luck for that to happen.
So bottom line, my recommendation is use the
laser sight there's really no reason not to and 25% improvement in hipfire spread
can be a real help and that's it thanks for watching and as always leave a
comment below with your thoughts on the "Fookin' laser sights" and if you have a
story of ever detecting an enemy or being detected because of the laser feel
free to share I'd love to hear it. As always guys I hope you enjoyed the video
and I'll see you in the next episode!.
New channel plan gaming subscribe now link in the description below Why pee be yourself I am Matthias welcome to 10 strange or ridiculous or crazy tech items that may waste your money today I'm joined by Sam From battling universe see that info card right there quick and you're gonna see videos a little something like this I'm gonna use the spell of icy grasp gala. Let's coordinate this right because I was your favorite when you're alive Oh were you though, I did try to save you I did guy I. Shot for you remember that I took a shot be you Cool this is dope check it check it yo, but today. She's picked out 10 tech items that she thinks well I don't know what she thinks about him.
Yeah, we're gonna find out. Yeah, yeah Bhavana let you know whether they're tasteful or wasteful now It's time to click the bell icon If you still have hearing listen to me now it's time to click that Bell icon so get notified when I upload videos So you can be there when I come back within the first 30 minutes, so thank you For em soda can robe ugh robe ugh, what's up wait Star Wars. What's this? That's Cool Wait what bb-8 you can make in Lagos yeah, they released a lot of new service products this past Friday. What? Voice fighting dude yeah.
Oh really I saw it cuz I was at the mall and Before it opened there was like a line outside of Hot Topic No these are dope dude guys. Let me know down in the comments below Would you like to see like a Star Wars themed video I would You know or maybe just like a Star Wars theme channel or something like that or maybe let's just all go watch Star Wars together either or oh Yes soda can robot Is not as cool now, dude I want bb-8 What batkid what you're holding is so weird let's watch this video. Is that a TIE fighter? What is that? Oh? No, that's just I got Star Wars on the brain All right We can move on now. I got that out of my system.
Yeah, okay, let's buy it whatever at the Carter ICU he's trying to start slamming things I don't think this comes with a can So where do I get a cam especially one that looks like that we have one prepared for you really? Build recycle create okay, is this recycling though because recycling means like you're reusing it for a purpose I don't think this is a purpose fun fun is not real Because I'm dead inside Made it for you someone robbed me oh it's already been made. Oh, thank you. I don't have to make Yes Look at this thing how weird I mean? Here's what here? I'm gonna. Give it a fighting chance here All right stick the thing in there like that And then turn it on and then you turn it on right Why does why does there need to be a can in there at all I don't know So why not just shape I think yeah, it just gives it a buggy shape right Here's the thing right when I was a kid And I would build things with my hands way back way back when way back when dude stop we would make things with like all these DC motors and electronics or boxes or Welding or cutting saws and all that good stuff But what we made was usable it wasn't pointless to turn it on with the can in it It's like once you turn it on you immediately want to turn it off.
Hey you're mean you're like Oh, I'm done with it for that reason. I'm gonna say wasteful for a couple other reasons, too RC micro blimp UFO flying saucer see if this thing had like a star warship under Oh, man Yeah, I liked you better Dude, okay. Oh, it's an iPhone connected remote control blimp. That's kind of cool.
That's actually kind of cool You know you can fly it around a noise and people everyone's like a drone and you like no It's not it's a slow-moving blip suck it. I'm allowed to fly this over your house blimp in basics. I. Can't wait dude going to basics man.
Yeah, I don't know the blimp in basics though I have to read that add to cart' microbe one oh It's small I want a bigger That's actually kind of cool-looking Look at that dude. This actually looks like it's made with precision all right So then you just like glue it or something all right, so let's blow this puppy up the idea here Yep, he's raising we use all these tiny little magnets to the counterbalance There we go Okay, so now we connect it to the phone and we flying around Whoa now it's now there's too much weight oh There we go okay. I see it oh I have altitude control Go forward Whoa we're backwards that's backwards. Okay.
That's for me Dude this thing is difficult to steer There we go, okay, so it's really difficult to steer let's see the issue is it's not working right to left yeah, the opposite of how it drum controls all the controls are walking so I'm holding it upside down and now I move up and down beats now This is some control No no no absolutely not this is very very difficult to control I feel like I could get the hang of it I absolutely could because is definitely one of those things where like you have to use it inside this thing? Really crazy dude the slightest gust would just take it away I say that's tasteful because I feel like you know That would have been better than a dope toy um to have like when I was like 10 or 30. Yeah something like that Space scooter right on black what is a space scooter? What is the space scooter? So you just pump it, and it goes oh dang this guy's like I. Feel like that makes things real dangerous, and that's what powers me to that's gonna give your calves ah yeah, okay? I get it dual mode super silent drive system awesome. Dude 149 dollars guys 150,000 mics we buy it we test it we let you guys know whether it's tasteful wasteful I don't know yet But I want to try it out See if you guys are like me and you want to try it out in the seat well give this video a like Okay You Vishu sanitize through ultraviolet light sterilization 15 minutes 99.9 Kill shoe sanitizer, okay, I get it you throw those in your shoes and It sanitizes them.
It's just so funny. I mean if you're at the point where you need to like sanitize your shoes Maybe you should get some new shoes You should get some new shoes. You know I mean, maybe they're talking about only these dress shoes Yeah, I mean where it's like. Uh you know they're like $150 you don't want to like but then again You don't really use them that much gotta sanitize my shoes don't put that nasty bacteria in my toes Toejam is contagious It's a scientific fact.
It's contagious. Dude isn't it Sam? I? Wouldn't know I thought you were telling me about your problem I'm just kidding guys. She doesn't have a toe jam problem. Don't have a toad um problem Actually, I've never seen her toes so it's possible trust me I know Possible anything's possible if you put your mind to it Sam Add to Cart all right here we go shoes Ultraviolet sterilizer do you want to give it a first try on your shoes? I? Mean sure you know what doesn't look like you have socks on so we'll just leave we'll leave the shoes off What oh these are the pole? So weird though Yeah Okay, guys here.
We go watch out. This is UV light. Oh wait. What something's have oh, they're on That is bizarre looking.
Do you smell that all of a sudden? Oh my gosh? I smelled it instantly Right when I turned on just like a burning smell like the bulbs are slightly burnt now - well You don't smell that really bad. Oh, I have a really good. Sense of smoke a smell Smell it wait oh Wait wait till I turn it on like Glass okay, you guys smell that that can't be good instantly right. I told you Yeah, it smells like when you leave like your hair straightener on yeah, or you just left the toe fungus them too much Look look at this up close it looks really cool It looks cool, but that's melons concerning yeah Stinky stinky I'm not putting them on my shoes.
I don't my shoes to catch fire I mean I know UV light kills stuff, but I'd have to read up more on it But it's just it's one of those things where you're just like shine a light on your problems will go away Because I don't really know I mean I'm on the fence you guys decide there's a pole right there Would you use this yes or net yes or no yes or net yes or net all right? Yes, or net full right there. You know you know what to do Ah Yes, the insta 360. We've looked at an insta before on this channel because they sent us one I think they sent us another one Which is pretty cool so $2.99? This is a 360? Camera, and this is I believe one of their new ones alright so this video full disclosure It's not sponsored, but they did send me one But I did really really really like the last one because it was just like Fluid simple it just worked, so let's hope they continue on With that fluidity that simplicity you know we got 4k video. That's cool.
Cuz it's so small 360 photos and videos time-lapse Bluetooth dopes exactly a six axis stabilization bullet time I don't know what that is Whoa? Wait what? That's a bullet time. I guess so you swing it around yourself Dude, that is so cool Alright, let's take a look at this puppy You didn't want to slam it I want to be really careful And I respect that because because she expensive so let's figure out how to do this bullet time thing Sam Cuz that looks really dope look at this camera That is pretty cool. I have slight hesitations about swinging a camera over my head. This is made nice I feel Aluminum here, this is aluminum It feels like aluminum and glass if I'm not mistaken 4k Ultra HD sensor get the heck off of this There we go what's interesting to note here is that the the cameras are not perfectly aligned? So look at this whoa you see that That is so cool And you just swipe it back in there when you'll need it boom and then it's an accessory to your iPhone So let's see what else comes in here ooh.
Look capturing bullet time, okay? Capturing bullet time shots on your insta 361 find the string in connector. Oh sweet here. It is okay I'm assuming yeah, put your finger through the loop at the end of the string grip firmly and swing there We go this is it guys. Oh that thing's not going.
I mean that thing's Not going anywhere, so press it three times in quick succession one two three something's happening And then I think it starts and then it just starts probably right. Yeah, oh It made a noise, okay cool There we go I'm doing it, okay Did it it made it it made a noise pretty sure that's it so we've downloaded the app Plug it in like that There we go sixteen seconds, let's see what we got here guys Dude that's trippy bro see right here I can play different speeds right so I'm gonna do one time speed We're gonna see what that looks like See starts plan or it starts spinning obviously, I'm spinning faster than that, but that's crazy isn't that? That's really cruel cruel, dude. That's so cruel. That's pretty cool.
Just for that feature alone. That's really awesome I say case four Oh heck yeah, dude, I knew there's gonna be something Star Wars related it had to have been that way 6.5 Inch tall stormtrooper mister why I am mister creates an eerie mist of with tap water This is an officially licensed Star Wars product it in case there's any doubt haters This is official alright take a because It looks like someone just cut the top of the head off, that's true, and that's all that's in there just the robot Robot in mists you know the mist is looks like the missus lloyd smoke From when you go to head corals that is big Big as my head Luckily my dick cut off talking about talking weird dude knock man Talking like today strobe sack so now we put Water in so we want to do more than the minimum well look at this It's sputtering Whoa It's misting that's for sure yeah what this is supposed to do is literally supposed to just stop the sputtering But it's not really working is it Probably not. I feel like that could kind of be cool for like Halloween yeah You pee yourself That's better do it oh? All right, I'm over a dude, maybe have wet pants kill it kill it with fire Boon glow nightlight with portable balls, but I don't understand Why is this alien thing a thing? Come on you're gonna sleep on a bunch of balls that seems like the most uncountable thing Okay, I get it I get it. It's a glow-in-the-dark ball You sleep with it to keep away the bad monsters and the bad juju he's into it, though He's like give me at that ball.
All right. I get it Add to Cart I Just don't understand sleeping yeah I Mean sleeping with them. I can see how they can sell it to kids as a Mike Yeah as a nightlight like they last for 30 minutes. So hopefully that's enough time for you to fall for you Yeah, I get that I totally get that however.
I mean. Oh, they're really light They'll move around okay. My thing is like it's gonna be difficult to sleep on a bunch of balls Okay, thank you sleep on this keyword like next to you, okay Yeah, you put it next to you have you ever like put something next to you and then fell asleep You end up rolling over it Every time every time let's see these puppies blow. Oh there you go Okay, okay, so the sliding lever on the bottom allows me to change colors of the balls How long I have to let it sit I must have to absorb the light a lot bit yeah important dead wrong side Important to make the balls glow the glow balls are Two minutes so we need these balls on their pedestals for two minutes, so here's the deal.
They're only gonna ever glow green Because that's the glow-in-the-dark color. I know doesn't it shake you up yeah Yeah, do you want me to prove to ya wait? It's been two minutes. It's for sure been two minutes ready watch They're only green and if I even turn off this light you will see They're green that's the issue with this product you stink of poo poo I. Mean it looks kind of cool.
I wish I really I think that would have been really really cool. Had they glowed like Intensely, I'm gonna have to say wasteful. Sorry guys Tactical laser-guided pizza cutter, you know what that means Sam It looks like whoever took this picture though, it's like slightly blurry and like motion blur they're like a little too much pizza Maybe maybe a little west beats the next time before you market your product huh where's my grandson's favorite Christmas gift, okay Add to Cart I'm sold Oh magic Okay, obviously. This is crazy unnecessary class to laser.
Why though I would have I would assume That it's only for like you know how like a level works against the wall and like gosh. Yeah guidance. Yeah, that's the word yeah But now I'm starting to get a different impression with the intensity of this laser What you know what that is? This is like for a gun? Yeah, the railings. That's what that is wailing.
Thank you, Sam See this right here if we zoom in we can see this little riveted piece what that's going to do I assume is going to disperse the laser in a wine right because otherwise it would just be a dot. Oh, okay Yeah, right assume I assume. It's film. Yes.
Oh Yep, I'm right. Oh Also, if it's in the dark you know, but true this darkness situation if you're in a darkness situation where you're like I need pizza Okay, so yeah this is for. This is for guidance and what's cool is that pretty much any any way you slice it? Ya? Still gonna be there alright, let's put this puppy to the test am I right yeah, alright, Sam Look at that this pizza looks like it's been uncut so let's see how straight. I can do this alright Let's turn off the lights here Or let's push this back a little and turn off the lights here to get that sweet sweet laser my laser.
I'm gonna I'm gonna I'm gonna put it on this pepperoni. I'm gonna try and keep it on this pepperoni I'm doing it, dude All the way through Dude that I don't know that's a pretty straight, that's a solid cut though, that's a solid cut Okay, let's see how straight I can get it. I'm gonna go this half pepperoni imma stay on that See my angle is a little off It's okay now I know yeah, I've learned my lesson so clearly that's your slice, okay Look at that clean cut though that ain't no joke does Dave a fan guys Dave we're all Eight bytes before you can swallow my word do you want the rest hair sample here? I? Feel like I feel like you'll be good now does your mom feed you I? Hear if you don't eat enough you get toe jam Guys before we get into that next product make sure you give that big ole Subscribe button down below a big ol kiss for me right looks like this now when you kiss. It'll look like that right boom Netherland DC 12-volt car LED prager programmable showcase message sign scrollable display lighting board with mow Cheese you're gonna.
Give me an aneurysm with that title What happened wait I guess we can program it to be whatever we want Message lack of creativity right there Let's try it out Add to Cart All right, yeah, don't worry. I'll handle this No door you just eat your pizza, Sam. Oh, this is thinner than I thought it was gonna be so I guess What are the suction cups for maybe like a storefront? Yeah, or your car? Screw what look it came with a car charger thing It literally wants you to do it a car in a car first because I have to do this To plug it into the wall wow That's one way to do it Honestly how I wish I could eat pizza. You know if your mother were here right now She would tell you to cut it and slice it and dice it.
She'd be ashamed How do I do this Oh Insert delete Where's space I was gonna spell out. I don't have time for this honestly. That would've taken so long But I don't have time for it uh Alright, if you have road rage. This is gonna be a great product for you.
It clearly works because they got it to work but it's Taking me up cuz I can't figure it out in two seconds to show you But it clearly worked, so I'm gonna say tasteful if you need to put out your aggression into the world I don't recommend it cuz you can probably get in some fights You know fault people might follow you to your house and beat you up but Whatever you want to do. That's up to you. Yeh? Sleep tailor Yodo comfortable contoured, I'm asked HiFi stereo Headphone embedded sleep mask. I actually have one of these you do Yes, I mean It's a little bit more rudimentary than this this guy looks like he's from the future which would complete my own sambal yeah Right, but I actually had one Well this one looks more padded see the only issue with these types of things is that the speaker's Sometimes are like too thick and when you want to lay on your side, and you got big ears like these honkers It presses him down and it hurts, but this looks good.
Let's try it Add to Cart All right, this is the test oh Oh, I just pressed in on this just to be Helen. I think I broke something in it Do I look like I'm from the future? It's not bad The only issue I have with it is the fact that my ears really stick out so They get sore if they're pressed too much. I mean I make them. Let me see your ears Yeah, you're use are pretty far in yeah So it's not gonna be a big issue for you with like this kind of thing.
You know look my ears They stick out like crazy dude, so these kind of things are really sore alright. Let's let's hear To myself right now This definitely helped me fall asleep Wow not great speakers Really really not great speakers like they have no mids or lows in them whatsoever so for that reason I'm gonna say wasteful Just because it's like I don't know if you listen if you want to listen to music before you go to bed You don't want tinny you know that tinny sound You know you gotta like get deep into that music you know have some of that soulful bass in there. No Sam get moved into sleep See that video right there that is five tech items under $10 And I show you guys some links because they're pretty Weird or crazy tech gadgets you decide let me know by clicking it, and I'll see you over there high-five.
Is it hitting the brick wall? (Johan) It's hitting the brick wall.
(Destin) We're not gonna set your house on fire this time? -No -I'm not gonna get through a brick wall, definitely not.
(Destin) Hey it's me Destin. We have a class 4 laser. We're in Holland, and this is Johan, and he's a laser expert, guru, whatever you want to call it. Alright so, we're going to do a lesson on colours in Dutch, because I don't know them.
You ready? -I'm ready
Alright, so. We're gonna turn the laser on high power first. -Ready?
Yep -OK there we go.
OK, so what colour is this laser Johan? This is blue in english. -Blauw
Blauw? -Blauw
Blauw.
OK so what colour is the first balloon? -Rood
Rood, which is red? - Ahuh Did I say it right? [R-rolling attempts]
Rood. OK. Red balloon vs blue laser. [Pop] Easy.
Next colour -Orange, or.. Oranje [pop] Easy.
-Yellow, or Geel Geel? -Geel
OK like hell? [Pop] -Geel That's a weird one. -Green or Groen.
Groen? OK. [Pop] Alright.
Hm. -Turquoise was it?
Turquoise, yep. -Turkoois, in dutch.
OK. [Pop] Woah.
Turquoise balloons are louder. -We have blue, or Blauw. -Let's see.
Aaah! [Pop] -Then we have Here's one for you. What colour is this?
-Black, or swart.
[Pop] Woo!
-And finally, white, -or, wit. OK.. What's going on here? We have a white balloon that's not popping in the laser that popped every other colour.
Would you like to explain laser guru? -The white one scatters all the light, so it doesn't absorb the light, and -doesn't heat, and doesn't pop.
There you go.
You're getting Smarter Every Day.
Please subscribe. Thanks Johan. -You're welcome. If you want to see his website, it's bluefan.Nl.
Thanks. -Let's pop the rest of the balloons with the laser, because we can.
Yes [popping of balloons] huh?!
-This is a white one! [Laugh] This is too. I can't see with my laser goggle on. [Music] Hope you're getting Smarter Every Day.
[Pop]
What colour was it?! - [Laughs] -I squeezed it.
Oh did you? Alright, so if you have any good ideas for Smarter Every Day go check out the Facebook page and tell us your idea. Bing! [Laugh] Get it? Light bulb. Alright. Later.
Have a good one. You've heard of sharks with laser beams on their heads, but ah, come on down. The cool thing about that is the laser beam, not necessarily the shark, and even though there's shark week, we're gonna have laser month, because that's way cool. Johan here has built this laser It's a 445 nanometer, 3 watt, 3 diode laser, and it is capable of burning about anything you put in it's way, depending on it's colour.
And, we are going to do laser month. [ Captions by Andrew Jackson ] Captioning in different languages welcome.
Please contact Destin if you can help..
So I would use 1064 long pulse wavelength in the treatment of dark skin hair
removal. You know if your gonna do a good
job in hair removal now you need to be able to treat all skin types well and many times
people try to get one system and make it work but 1064 is really the best wavelength for skin
type 4, 5 and 6. I also would use it in a fair skinned
person with course dark hair. So in your laser manual there are
setting hair removal for thick hair or thin hair
and brown hair versus black hair.
Usually with a person's first laser
treatment for hair removal you wanna start with the settings for thick hair and as you move on to
subsequent treatments the hairs that you'll be treating get thinner and thinner so
you'll change your settings to the thinner hair settings. With the thick hair
settings because the thick hair has a larger diameter you want to use a longer pulse duration
so that the energy is delivered over a longer period of time versus a short energy or short pulsteration where you're delivering the
energy too quickly. With laser hair removal treatments you
always wanna use some kinda cooling so we have the Zimmer cold air blower
connected to our hand piece here so that the same time of the treatment
there's also cold air blowing onto the skin and the cooling is for two reasons one
for patient comfort but two more importantly is to protect
the surrounding tissue in other words the skin or the epidermis that surrounds the hair follicles that
we're treating. So as we do the treatment I'm gonna
cover the entire surface area of the skin that we want to treat a
little bit of overlapping is OK.
But generally speaking overlapping is
not necessary The clinical endpoint to look for with
laser hair removal is a little bit aerothema which we see here as well as some
parry folicular edema which is just a little bit of swelling
directly around the hair follicles and thats very normal and actually shows
a great result. Also laser hair removal for Fitzpatrick types four five and six can actually be
more painful than laser hair removal for Fitzpatrick types 1, 2 or 3 and that's just due to the
amount of pigment that in darker skin colors and that's very
normal as well. So Grant how does your skin feel after
the treatment? It feels good. Does it feel warm at all? A little bit
but not too bad.
Okay so a little bit of heat sensation
like a mild sunburn is natural and normal that usually last about two to three
hours and then it should dissipate. If it bothersome or uncomfortable you can take some Tylenol or some ibuprofen to help with that you can also put ice packs on your skin
to help with that as well. Your next treatment should be in roughly six weeks or so and then you can also use any of your regular products for instance when you shower
wash your face with soap that's fine and any aftershaves or lotions
that you normally put on your face is totally okay to use as well but you do want to use a good spf on
your skin for any time you're in the Sun for good
sun protection after having a laser treatment. Okay thanks so much for coming in.
In the next couple of lectures, we will discuss
about the semi conductor lasers. So, today I will discuss basics of laser or laser fundamentals.
Some of you would have done a course on lasers, but some of you would not have done. So, this
is basically reviewing laser physics and recalling the fundamentals of lasers. So, let me start
with the basic question what is the laser? And we all know, what is the laser? Laser
is a source of coherent monochromatic radiation, in the optical region of electromagnetic spectrum.
So, laser is the source important point here is it is the source, it is the source of coherent
monochromatic radiation.
Radiation in the optical region, so in typically optical region
means approximately 0.2 Micrometer to 20 micrometer approximately.
There is no in this region, it is the source on monochromatic radiation and it works on
the principles of laser that is light amplification by simulated emission of radiation. When it
is a source it is a analogous, it is analogous to an electronic oscillator to an oscillator.
So, it is analogous to oscillator an electronic oscillator is a source of RS and we know that
an oscillator is comprises of an oscillator is basically an amplifier and a feedback amplifier
plus feedback. An amplifier followed by a feedback circuit
gives you an oscillator. So, typically you could show the oscillator by an amplifier
A here, with as an output and with feedback circuit, feedback.
It general oscillator has
an amplifier, it is an active device an active device and a feedback circuit. The active
device is able to provide amplification and when you power it for example, you have supply
plus minus. So, this forms the general oscillator, the
feedback circuit may have RC or may have inductor, may have capacitor and so on. But therefore,
laser is the source of radiation in the optical region of wavelengths and it is analogous
to an oscillator, therefore it has an amplifier and a feedback circuit.
Amplifier in general
consists of an active medium or active device which is pumped which is powered by a power
supply. Therefore, in general the 3 important components of a laser the three components
of the laser. In general this is not necessary semi conductor
laser, any laser has 3 components. First the gain medium the gain medium or the active
medium which provides gain when pumped.
And therefore, you need pumped pump or power supply
and an optical feedback optical feedback unit. These are the 3 components, this could be
an active device which provides amplification when powered properly or when pumped properly.
And then optical feedback unit this is optical resonator optical resonator optical feedback
unit this is nothing, but optical resonator. These are the 3 components of laser. So, when
the active medium is pumped it provide gain and the resonator has a certain loss associated
with it.
Whenever gain exceeds loss you have net amplification at the laser can start oscillating.
So, let me show a general schematic of the laser both for bulk and semi conductor. So,
let me and then have a comparison, in general if you take bulk laser say Nd-Yag laser. There
is an active medium
the active medium which is pump externally may be by flash lamp, may be by another divert
laser external pumped. And the amplifying medium is placed inside
an optical resonator between to media.
Let us say of reflectivity R 1 and R 2 and this
forms the basic schematic of a laser the bulk laser. The semi conductor laser also have
almost similar structure, so we have the schematic, the active medium here I am not drawing all
the layers. So, these are the electrodes, this is the longitudinal cross section longitudinal
cross section of our laser and this is our active medium. And current flow through this
forward bias PN junction is a current I, this is p, this is n and there is the electrode.
We know that if it is pumped properly, when the injection of current is sufficiently large.
We can have the separation between Fermi levels, please recall that delta n is equal to I by
e into tau divided by l into w into d where, d is the thickness of the active region, w
is the width for the front side if you see, and l is this is l.
So, depending on the current
through the device, delta n can be large and if delta l is large, the Fermi level the separation
between the Fermi level can be large enough. So, that we have the situation, where E f
c minus E f v is greater than E g or greater than h nu. So, in this situation you can have
gain in the medium. So, the gain medium here, the active forms gain medium, when you pump
it sufficiently, strongly to reach such a situation.
In this case we should an atomic
system, so gain is for simple terms. So, if you are with familiar with laser physics.
It is a if you have N 1 and N 2 as the number of atom per unit volume in the energy level
E 1 and E 2. If you pump sufficiently hard that is raise
atoms from the ground state to the higher state through mechanism in a 2 integral normally.
You do not have steady state oscillation, but through some mechanism if you pump and
create a situation where, n 2 is greater than n 1 which is called population inversion population
inversion. We have gain, so this medium become a gain medium this becomes a gain medium.
That is why you are pumping externally to the pump here, just taking the same role as
the current.
And the pumping leads to population inversion,
it is possible to have population inversion which means this becomes the gain medium this
becomes the gain medium. Here the gain medium is placed inside the resonator, so that there
is light which is travelling in this direction. Guess feedback light which goes in this direction
could come back which acts as an optical feedback. Because, the same light is spread into the
gain medium, the same thing happens here, if you cleaved ends, this is the cleaved ends.
So, cleaved ends both the ends are cleaved.
Cleaving is the initiating a break along epsilon
of plain. So, that it results in mirror light finish. It is not cutting it cleaning, so
you have to scribe and initiate cleavage, when crystal is cleaved along a crystallographic
plane. You have perfectly reflecting inner like surfaces.
So, if you have this medium
reflecting index n 1 and this medium reflecting index as n 2 which is outside air. Then the
reflectivity here, at this end light which is generated which reaches this end has the
reflectivity R which is equal to n 1 minus n 2 divided by n 1 plus n 2 whole square.
And if you put the numbers as we already discussed if you 3.6 Here, 1 here outside you get approximately
equal to 0.32 That is 32 percent reflectivity due to the cleaved ends. In normal laser do
not have any mirrors at the end and the feedback is obtained by the 32 percent reflection at
the feed at the 2 ends of the cavity. So, in this case the cavity is here, so the light
goes back and forth.
The optical resonator, the mirror the active medium placed inside
the mirror here forms the optical cavity or the resonator.
Where, as in this case the active medium with the 2 cleaved ends here this end here and
this end here. Cleaved ends form the optical resonator, it acts like the mirror. The reflectivity's
are just about 32 percent, but in a bulk laser normally you have 1 of the mirror almost 100
percent reflectivity, very high reflectivity. And the other 1 partial reflectivity of approximately
90 percent or 95 percent, because so that a part of the light goes out.
In every reflection
part of energy goes out which forms the useful light for you. For which I redraw the same
diagram again, if we redraw the schematic here. Therefore, the laser would look like this,
so you have the active medium and just again drawing the other than showing there. So,
you have the laser beam which is going back and forth, and the part of that coming out.
So, this is are the 2 mirrors and this is the beam which is formed here.
The rays which
are going back and forth, if you have spherical mirror, you can show that in a spherical mirror
resonator spherical mirror resonator. You can show that the most of the resonator
are hermite gauss fields or leger gauss fields hermite gause fields. Fundamental modes of
this family hermite gauss fields represents the whole family of the modes. The fundamental
mode of this is the Gaussian mode T E M 0 0 mode, those of few are familiar, this is
transpose electromagnetic mode.
The fundamental mode is T E M 0 0 and this is a feal profile
which is like this. So, what I am drawing here is the amplitude distribution and the
same mode is coming out here. So, the bulk laser is I have taken a spherical
mirror resonator typical, Nd-Yag lasers are of this form. You have the mirror radius of
curvature could be above 80 centimeters 100 centimeters is a radius of curvature.
It is
almost flat and the Gaussian beam forms the resonator mode and this is the active medium
which is placed which is pumped. If you see the semi conductor laser, let me draw a gain.
Here also there is a optical mode which is formed, the mode here is determined by the
optical wave guide. Recall that this active region has the higher
reflective index n 1 and the cladding regions have the reflective index n 2 which is less
than n 1. So, it is like an optical wave guide a simple slab wave guide, so this is n 1 and
this is n 2.
So, n 2 is less than n 1 and n 2 is less than n 1. The modes of this structure
are actually cosine and exponential, but they also look like this. Approximately, the feed
inside is cosine and outside it is exponentially decaying.
You can solve the Maxwell's equation for this with the boundary conditions and you will
see that they are cosine inside and they are exponentially decaying fields outside. So,
the mode fields will also look like a Gaussian, this is not a Gaussian, but almost look like
a Gaussian.
So, in this case the modes I am referring to modes transverse modes so the
transverse modes. We have one more mode which is for the longitudinal modes, transverse
modes transverse modes are determined by the reflecting unit n 1, n 2 and the thickness
t. And here is a Gaussian? Gaussian with a waste
width here which is again determined by the radius of the covertures of the mirrors here.
And the separation d, separation l, so this is l in this case this is l, I have shown
you here although, I have shown almost of the same size. A typical Nd-Yag laser l is
order of 1 meter big Nd-Yag lasers, there are compact lasers also divert pumped solid
state lasers or now quite compact, but still may be 10 centimeters, this l here is approximately
300 micrometers.
So, this is very small, very compact and this is big size, but I have shown
this together just to bring out a comparison. And those of you have studied laser physics
can immediately relate the 2. So, this is regarding the structure, so the basic structure
has an active medium which is pumped and there is the resonator. The resonator determines
the modes of the structure, the modes of the laser.
We will discuss the resonator a little
bit more, but let me first discuss about the gain. It is the gain medium play in an optical
resonator; let me first discuss little bit more about the gain. And then we come to the
modes. The simplest basic laser theory is very simple, basic laser theory is quiet simple
laser dynamics.
Laser dynamics or laser theory at steady state,
because there are transient analysis which is a more involved. At steady states the laser
theory is just this types gain equal to loss, I will simply write gain equals to loss. The
laser theory is very simple gain equal to loss, gain here refers to gain in the active
medium the gain in the active medium or laser loss here refers to loss of the resonator
or in the resonator. First let us discuss about gain we had seen for a semi conductor
laser.
So, let me draw for semi conductor laser and
just for comparison let me also draw the bulk laser. So, this is mu versus gain codification
gamma of mu, we had expressions for gamma of mu. So, this is gamma of mu and this is.
So, semi conductor laser if you pumped the laser, so that this condition is satisfied.
Then we had work down in detail that you have gain profile which goes like this. Then it
will becomes starts approximately around E.
G. So, this is for a particular current or
a particular delta n, some value of delta n.
If you had not pumped then the medium was absorbing recall that medium was absorbing.
And therefore, it had some curve like this or maybe it was doing like this. As I pump
started doing like this, see pc what I am showing is this is the here it is 0. Therefore,
this side it is loss coefficient and that side it is gain this side gain.
Hence when
gamma is greater than 0 is gain and gamma is less than 0 it is loss.
You have not pumped than the medium of absorbing, we are discussing this in detail and the absorption
coefficient is varying like this. Stating from E g and increasing energy, if you starting
pumping and you are able to maintain this, then gain will become positive, so this value
here correspond to this value mu. Then this is E g by h so e g by h and what was the value
here energy correspond to here E f c minus E f d. We therefore, 1 by h into E f c minus
E f b.
So, the bandwidth was this region, this region
called amplification band width. Amplifying the frequency range over which we can get
amplification and this is the p gain equation, this is gamma p. We pump harder, that means
if we inject more forward current, then this would go up. And this will also go up because
the separation is increasing I plot for that for another value.
So, what I have plotted
here is gamma as a function of delta n, different values of delta n. And recall the expression
here, so if you know what is the current. So, if you are sending 50 milliampere, 100
milliampere then you can immediately calculate what is the delta n? Because e is to know
this is the combination time. These are the dimensions, so d is this thickness, so l is
this one and w is width from front side.
So, recall that let me show briefly here, the
front side then you have, if I place the electrode width, if you replace the electro width blocking
layer here silica, then this is how the carrier still flow.
And therefore, this is the region where you can have gain in the front view front view.
This is longitudinal the profession, so this is that light is coming like this in this
case light is coming to the sides light is coming here. So, I have than the field distribution
which is coming out. So, this width here is w, this is w typically 5 to 10 micro. So,
you can substitute the value and find out what is delta n if you take for typical materials
than this delta n is order of 10 to the power of 17 per cc.
Practical numbers you can put some numbers for laser amplifiers and that is of that order
delta n correspond to 10 to the power 17 per cc.
So, as you pump the gain available increases,
gain band width increases. Those of you done laser physics course you would know that this
case also when you have not pumped to the medium you would have a loss which is characterized
by this. And you start pumping than this increase, becomes smaller than beyond a certain pumping
is a you will have the gain curve showing this.
Usually symmetric in the case of atomic systems the same thing gamma of mu as a function of
nu. And these step normally they correspond to either Lorantzian which corresponds to
homogeneously broad and median and or Gaussian.
So, homogenously or in homogenously broad
and media give spent of. So, they are showing this because they are identical what are this
curves? This are gain curves for different pumping powers different pump powers, here
it is gain curve for different injection current and therefore, different delta.
They are identical if we study 1 laser system that is why I showed that comparison. There
is also mirrors here also you have mirrors, no separate bulk mirrors, but mirrors is formed
by curved ends of the semi conductor laser. So, gain equal to lose this is what we know,
what is the gain, What is the loss? The loss of the resonator, what kind of loses do we
have.
If I take this balk resonator here, so loss in the resonator the beam is going
back and forth, the mirror have finite reflectivity of R 1 and R 2 may be almost 1 or 0.98.
That means, 98 percent reflecting and this is 95 percent say I have to number just taken
example, R 1 and R 2. This is the separation may be 1 meter and this is the medium, the
beam is going back and forth in the medium. When it goes back in forth in the medium there
are 2 types of loses which you encounter. One is catering losses in the medium and medium
they can be catering because of homogenates they can be catering loses in the medium.
And second loses because it is a finite beam using there is the diffraction losses.
So, you have catering loses and diffraction loses and loses due to finite reflective of
the mirror.
It is 95 percent reflecting mean 5 percent is going out. This 5 percent is
your useful output power, but as far as a resonator is concert resonator is losing 5
percent from this side 2 percent from this side. So, mirror are also the loses and therefore,
you can show the loss qualification I will not go into the details of the derivations,
but the resonator losses comprises of alpha s to plus alpha m. This is primarily due to
scattering in the distraction and this is due to mirror.
So, this is equal to alpha s plus 1 over 2 l ln 1 over R 1 R 2.
You can show this I leave
this an exercise, it is simple derivation shows that the mirror loses 2l into you can
see that if the reflectivity is the 1 that is 100 percent reflecting R 1 equal to 1,
R 2 equal 1, ln 1 equal to 0. So, there is no loss due to mirrors, but reflectivity cannot
be 1 and we do not want it also 1 because we needs useful output coming. So, this is
the resonator loss, we have already derive the loss coefficient for expression for the
gain qualification. So, if you equate gain equal to loss that
is it you get the expression for gain coefficient and gain equal to loss gives you the laser
dynamics.
So, what is this gain equal to lost let me write and explain me again very quickly,
just recall it the basic laser physics. I. Am sure most of we have done those of done
it is just here revision and those who had not done please refer properly at book. If I plot now for example, let me give you
some number into the case of semi conductor into the case of semi conductors alpha s is
of the order of 10 to 50 centimeter inverse.
The scatting and diffractions losses is the
order of this actually there are no diffractions losses because this are guide structure. In
the case of bulk resonator there is no guiding without the beam is just going in free space
where as inside the resonator, but here it is guided wave guide does not have diffraction.
So, there is no diffractions losses, but there are losses due to the wave guide scatting
and imperfection at the boundaries and so on. So, that is typically in this range and
it is substitute this alpha m is equal to 1 over 2 into 300 micrometer in here into
ln. You substitute this 1 over 0.32 Into 0.32 And we will see that this is approximately
38 centimeter inverse.
You calculate and see that it is about 38 centimeters inverse, almost
similar order as it. And therefore, the total resonators loss alpha r is approximately by
38 and 22, let me take somewhere between in 22 just make it to the round figure.
It approximately 16 centimeter inverse, just get feel for the number of what types of number
that we have talking about alpha r. And we want gain equals to lost means what gamma
much be equal to are alpha r gamma of mu much be equal to alpha r, which means to have gain
equal to that mean you require a gain of about 60 centimeter inverse. If you want gain equal
to lost satisfied, now what is happening? If I plot this more of alpha r, this is actually
gamma and alpha r is actually negative minus gamma.
And but if I plot more of gamma here than 60 is here let us see this 60 centimeters
inverse.
So, this is shown we are plotting this as a function of frequency; the quantity
is here are generally independent of mu over the range of interest. The reflectivity and
the both alpha n and alpha s are almost independent of mu over the region of interest. What do
you mean by the reason of interest? We call that the amplification bandwidth that we had
calculated some number and I had said that we had calculated approximately into 10 to
the power of 12 to10 to the power of 18 hertz the band width for semi conductor laser.
So, this is we have also seen the this is very small compare to the light frequency
itself which is 10 to the power of 14 into 10 to the power of 15 hertz. And therefore,
over this small range of this frequencies this does not change and you normally see
looks that pro got at line like this and all this are loss line.
So, what is loss line?
Loss line is value of loss in the resonator if you start pumping the laser the gain is
here, gain is less than loss. So the laser cannot .
If you pumped harder than you could for another pump power you may have the gain curve exceeding
the loss curve with which means for these frequency is here. This frequency over band
width b you have gain more than the loss it is the condition for starting of oscillations.
You calls the electronic oscillations which have the criterion A beta equal to 1 when
oscillations of minus 1. A is the amplification beta is feedback ratio, so A beta is equal
1, but the time starting oscillations A beta should be greater than 1.
And then due to saturation non linear saturation this will come out be 1 at that steady state.
This is how the electronic oscillations work exactly, like this that you pump harder this
gain will exceed the loss lines, but due to gain saturation gain saturation this is the
dynamics.
Actually, the gain saturation is the dynamics, I would origin to understand
this clearly, but I do not wish to digest too much explain to you what is gain saturation.
But gain saturation simply means whenever the gain is larger this will be pulled down
by the dynamics, by the dynamics of the system this will be pulled down. What do I mean by
dynamics? I do not want to get into, alright let me
very briefly explain they cannot go so much into. We pump harder which mean create larger
population inversion it is easy to understand here that is why I am showing you. Therefore,
N 2 minus N 1 here, becomes larger which means gain becomes larger, when gain becomes larger
than more radiation laser radiation intensity increases, when lasers radiation intensity
increases here it will bring down more and N 2 downwards.
Therefore, N 2 minus N 1 decreases we see the gain coefficient gamma is proportional
to N 2 minus N 1.
If the laser intensity in the cavity increases it will bring down more
atoms downward and more stimulated emissions. When more stimulated emissions occurred the
N 2 decreases. And therefore, N 2 minus N. 1 Decreases, and therefore, the gain is pulled
down.
In others word at steady states equals to
what I have drawn here is if I independent show you the loss line and independently show
you the gain curve this is. But, when a laser is oscillating in steady
states the graph is this. This is the loss line and this is the gain curve that is when
laser is oscillating steady states gamma is equal to alpha r always. Irrespective of the
power output of the laser when a laser is oscillating in steady state, but gain coefficient
is equal to loss coefficient that is why I.
Written gain equal to loss.
There are you have to understand the more how this is, this is called gain clamping
and gain is always clamped at that value, depending up on homogenously broaden or inhomogeneous
broaden. There are what are called hole burning in the gain profile and so on. Let me not
a going to this. So, the main point is this when the laser
is oscillating, gain equals to loss or gain co efficient is equal to loss co efficient.
This is as far as the amplifying medium is concerned.
So, the amplifying medium is the
active medium which when pumped appropriately gives you gain.
Now, the second component is the optical resonate optical resonate the optical resonator determines
2 things that is the longitudinal modes, and the transverse modes longitudinal modes and
transverse modes Longitudinal modes refer to resonance frequencies I will explain it
in minute resonance frequencies, and transverse modes refer to field
distributions or the modes. First let me talk about the longitudinal modes
or resonance frequencies, of simplicity I. Will show the plain resonator this is l here.
When light go back in forth inside the resonator it is going back in forth only those frequencies
which satisfy. The round trip face equal to integral multiple of 2 pi will build up, because
any light which is coming back after 1 round trip if it add in face with light which is
generated.
Then it will start building up therefore,
the condition is round trip face is k naught into 2 l equal to 2 l because round trip must
be equal to integral multiple of 2 pie q times 2 pie. K naught is the if there is a medium
of refractive index of n. Then you have to write k naught into n, if there medium of
refractive index. So, 2 pi by lambda 0 into n into 2 l is equal to q into 2 pie.
This
lambda 0 I can write as C by nu. So, this is 2 pie into C into nu into n is the refractive
index, q is the integer, q equal to 1 2 3 integer nu into n into 2 l is equal q into
2 phi. 2 Pi 2 pie goes, so what you have left with this is nu q is equal to q times C divided
by twice n l. These are resonance frequencies, the resonance
frequencies are allowed frequencies which build up inside the resonator.
The resonator
supports certain discrete frequencies which build up inside the resonator and they are
given by the resonance frequencies I have added the suffix q to say that the q th order.
So, if q is equal 1 it is the new 1, so what is this what we are showing is if you we are
plotting on the new axis only the certain frequencies are allowed to build up.
These are called, so this the nu 1 or nu q nu q plus 1 nu q plus 2 nu q plus 3 and so
on. The resonator determines which are the frequencies which will build up inside the
resonator, because of the round trip face matching condition. These are the resonance
frequencies, now let me complete this discuss of resonance frequencies. I just now showed you that for if this the
gain, gain curve gamma of nu.
This is axis nu gamma of nu and this is gamma of nu and
if the loss line is here alpha r. Then all the frequencies which are in this range, they
have gain more than loss. However, this amplifying medium has been placed inside an optical resonator,
the resonator allows only certain frequencies. So, I just keep this graph here which means
resonator stays only this frequencies can build inside.
This says all the frequencies in this range have net gain; however, resonator says only
these frequencies are the 1 which can build up inside the resonator nu q plus 1 nu q plus
2 and so on.
And therefore, only these frequencies will be there in the laser output, if you
see the output of the laser. You will have if you see under the high resolution spectrometer,
spectroscope, optical spectrum analyzer then you will see an output which look like this.
This is the output of the optical spectrum analyzer, laser output you feed it when the
optical analyzer, which mean it is resolving and you will see the output like this. The
strength of the mode is proportional to the difference in gain. So, you can see if I take
it here it will intersect here, this is the additional gain over loss.
For this 1 all
this details I will not be able to cover here it is part of the laser course, but it is
proportional to this difference gain minus loss.
The strength of these modes in my diagram it should be bigger because I should have
been drawn like this. Let me correct it because this is bigger than the other 1 and so on.
All though there are other frequencies the resonator allows the other frequencies please
see this, resonator allows all frequencies which are discrete. However, these frequencies
for these frequencies gain is smaller than loss and therefore, they do not built up inside
the laser. Only those resonance frequencies for which
gain is greater than loss build up inside the resonator and in the laser output you
can see this.
What you see are called the longitudinal modes of a laser. So, these are
the longitudinal modes normally, if you take a laser there will be plenty of longitudinal
modes. Why I am bringing this concept is we are next going to see special laser structure
and divisor which will chose only 1 of them. To make it single longitudinal mode and that
is why we have to know? What is an longitudinal mode? Alright we quickly
come to the field distribution and then we will stop we have to take a small quiz.
The
transverse mode I have already mentioned about the transverse modes I have already talk about
this that our field distribution the transverse field profile. If you take a spherical measured
resonator you can show that hermite loss field distribution which means fundamental modes
looks like this. The second mode looks like this and the third
mode will have a field distribution approximately like this. So, this is T M 0 0.
This is T
E M 0 1 it depends on x direction I have shown 2 d. So, I can write 0 1. So, this is T E
M 0 2, because there is 2 0 crossing, there is 1 0 crossing. So, that is why 1 2 0 crossing
that is why 2 no 0 crossing.
This is not 0 this is actually infinity is a syntactically
going down, there is no 0 crossing. For a bulk laser in a semi conductor laser it is
a wave guide which determine what are the modes it can support.
So, this is n 2 as before and this is n 1 and this is n 2. The fundamental mode is this
here, so it is either T E or T M. There can be these are T E M this is Tem or Tm.
So,
T E 0 or T M 0. I do not want to again go into this model details, but you can find
out T E 0 or T M 0, T E 1 looks the same way. So, this is T E 1 or T M 1, T E 2 is almost
the same way and so on. The point is the mode field profile and how many modes will be there
is determine by the optical wave guide.
That is what is the different between n 1
and n 2 and what is the thickness d here? Those of few you studied the optical wave
guide you are familiar that there is a V parameter which is defined by the 2 phi by lambda into
d into square root of n 1 square minus n 2 square. It depends upon V value for V less
than pie it supports only 1 mode, V between pie and 2 pie supports 2 modes and so on.
What is important to recognize is transverse modes refer to field distribution by appropriate
choice of n 1 n 2 and d. It is possible to make this oscillating only
on a
single transverse mode by appropriate measures. We will see what are these appropriate measure
and it possible to make oscillate on 1 single transverse mode.
A laser that operates on
1 single transverse mode and 1 longitudinal mode is called a single frequency laser. So,
we will talk about single frequency laser also, single frequency single frequency laser
does not mean it has only 1 frequency there is no source which is a strictly mono chromatic
or 1 frequency, but single frequency laser means it operates on a single transverse mode
and a single longitudinal mode. Let me stop here and in the next class we
will directly start with semi conductor lasers we have covered almost all the basics everything
on the board. In the next class I will start the talk about PPT because we will now look
at structures and designs and characteristics.
There is no point in spending time on drawing
the structure, so we will go over to PPT. Alright we will come to the quiz a very simple
quiz very quick. Ready all of you are ready here is the quiz,
the frequency response of a particular led at 20 degree centigrade is shown below. That
is what is shown is a P a c, optical verses frequency that is the normal frequency response.
If the operating temperature is raised to 30 degree centigrade without any other change,
I have written those bracket you do not have to read.
Without any other change only temperature
has been raised, draw qualitatively the expected frequency response in the same plot.
First please draw this plot and then on the same plot qualitatively draw the expected
frequency response at a higher temperature which is 30 degree centigrade. What would
be the shape of the frequency response? Please draw the given curve and then on the same
plot, draw the expected frequency response variation. That is optical power ac optical
power, we have discussed in the last class verses frequency. As we know the cut of is
defined when P a c drops to half it is value, so this typical f c 1 is cut of shown.
So,
at a higher temperature please plot qualitatively what type of variation is expected no explanation
are required, just plot..
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Is it possible for the laser beam to reach the moon?
Let's test that! In 3, 2, 1... Go! Imagine bothering a neighbor with this laser... Guys, I'm gonna do a magic trick... Pick a card No, even better!...
See these cards? I'll put them inside my pocket... Now I'll drink some water My God! Omg... This is the magic trick Hi guys! I'm D4rk! Welcome to another video!!! Today I bring you another laser video! Great laser! I'm not sure you can see this cause
there's a lotta light in the bedroom... But I can see a huge laser beam! I asked you people to comment your suggestions for this series The series "Is it possible...?" And you asked
"Is it possible for the laser to reach the moon?" I loved that suggestion! Loved it! We're gonna do that today, guys! Let's see if this laser beam can reach the moon What do you think, guys? Will it reach the moon? Yes or no? I think I know the answer but we're gonna try it anyway! If you're enjoying the laser series leave many likes on this video so I'll make more videos with laser I can hardly wait cause
I've got many ideas for this laser but I'm only gonna keep it up
if you really support this video It's really important! If you're not subscribed to the channel...
Guys, subscribe to this channel! And press the bell button so you won't miss a video! It's too hot in this room!... It's the spotlight! Hey spotlight! Can you stop with the heat? Let's go, guys! Let's try to answer the question Is is possible to reach the moon with a laser beam? It's 10 PM. The moon is high in the sky I saw the moon and it's almost full great for this experiment but before I point the laser to the moon we're gonna do other things in the house by night Imagine... Lighting up the pool with laser Using these laser heads by night Trying to bother a neighbor with this laser...
Like, very far away... He won't even know
where the laser came from! Or maybe he will cause this leaves a trace! But I'll try not to get caught! I'm gonna do some more cool things by night so leave your comments if you wanna see more things by night Yeah, I think it's gonna work! I'll grab the camera and let's go outside! Guys, I'm outside and
the moon is right up there! Very far up there... One of the first things I'm gonna test is lighting up the pool
Check it out... Come on 3, 2, 1...
Go - Look at this! It's all lit up!
- So cool!... It's totally blue, this pool, man! It lights up a lot! Guys, I'm gonna use this pattern that I love... It's a dotty pattern. Check it out!
Awesome! - I'm gonna point this out to the pool.
Ready?
- Yes 3, 2, 1, go! - Awesome, man!
- It lights up everything down there! Even the trees! It lights up everything! Guys, look! It lights up all the trees! Check it out! I'm gonna try another pattern What if I overlap them? It alters them, look at this! I found another great pattern I think this one will
light up everything as well Come on, guys! 3, 2, 1, Go! Check it out! It's so wide! It lights up the whole house! From down there up to here! This is great! This one doesn't light up
the pool that much... But it works! I'm gonna point it way down there! Let's go!
3, 2, 1, Go! Look! It reaches all the way down there! It's a beautiful effect! Look at this! So cool!... I'm really curious now because
this laser reaches really far... And I dunno if it reaches the moon...
Check it out 3, 2, 1, go! Look at this! It's very high! This laser reaches the sky! Looks like it's never ending! I'm gonna reach a star! Guys, can you see a star over there? I'm gonna try to touch it
3, 2, 1, go! Look! - Do you think it touched the star?
- Of course not, man!... It's too far... Man, I doubt it reaches
those houses over there! - What? Those houses?
- Yeah, those houses over there... It will reach them, it will! I'm gonna point to those houses in the background I dunno if it will get there but let's try! 3, 2, 1, Go! It actually reaches those houses! Check it out! Check it out! Don't bother your neighbors, OK? Those houses are much farther away.
And it reaches them! Guys, I'm gonna spread the beam If I open this up it will expand a lot more Let's see what happens 3, 2, 1, go ! Look at this! Check it out! It's beautiful, man! This lights up the stars! Look, Malacueca! All these particles passing through the laser! Man, is this dust in the air
or is it the laser? Guys, can you see this? - Is this in the air?
- I guess so, man, it's dirt... How is there this much dirt in the air? You can see it very well Come closer You can see the dust just perfectly! I burnt...! Just kidding! If I bring my hand closer
I can feel the heat immediately If I touch it I feel the heat right away It's a powerful laser! I'm gonna point it to the pool
to see if it still lights up 1, 2, 3! It lights up even more! This basically works as a lantern as well There's a tree even farther away... I'm gonna try to reach it 3, 2, 1, go Look at that!... It really works! I'm lighting up the tree from afar! This laser is very good! Look when I do this! - Little stars, man!
- Look at the particles! Looks like the universe
with all these stars!...
Do you think this is how stars are made?... Guys, I'm in Star Wars!... Check it out!... Picture this actually cutting, man...
I'd be one arm short... You'd be cut by now I'm curious to see that hitting the moon! Cool it, Malacueca... That's for last! Pi is in his bedroom...
I'm gonna hit him with the laser beam I'm gonna open up the laser... We're under attack, Pi! The aliens! Pi, watch out for the aliens! What's that?! It frightened me! It's a lion! Man, stop that! Pi, you can't drop that!...
This is awesome, kid! Touch that star over there! It's reaching the star! How's that?... What happens if I point this to the pool? It lights up! Wow! This is awesome! So cool! Slowly... This is dangerous... - Watch out, Pi!!! It's gonna burn!!!
- Careful, man!!! Guys, another interesting thing...
Because this is an ultraviolet light it will enhance anything that's fluorescent Check this out... I'm not sure you can see this I have a very fluorescent orange ball and I'm gonna point the laser to it 3, 2, 1, go! I'm not sure you can see this but there's an orange ball glowing down there I'm not sure it's showing on camera the ball's right here... It's quite fluorescent as we see it I guess you couldn't see it I'm gonna try to hit a person Maybe a neighbor or anyone with an open window I'm gonna try that But don't do that at home, guys It's dangerous! And it's not OK to bother your neighbors! But I'm gonna do it cause I'm the Scientist!!! And I must test my... My...
The laser! I'm searching for a house with an open window but... I can't cause it's very late Guys, there's an open window over there It's very far
I'm not sure you can see it But I'm gonna try to hit it 3, 2, 1, go! I think it reaches it! But there's no precision to it... It's too far for me to focus the laser there! I need another window, another neighbor! There's another window with the lights out
I'm pointing over there Guys, see this house? See this window?
That's where I'm gonna try to hit I hope I don't get in trouble... 3, 2, 1, Go! I hit it! What if someone's a sleep in there? Suddenly there's a laser beam in the room! Guys, there a constellation up there...
Yeah... D4rk also teaches, ya know? It's the Triangle constellation Here's one star... Another here
and another there, see? They make a triangle, huh? Triangle Constellation! I wanna find more constellations... But there aren't any It's a pity the guys went out Only Pi is home It would be great to scare the guys! But unfortunately they're not home But I'm still gonna light up the whole house! I'm gonna spread the beam some more so it will light up even more! It lights up everything, look at this! Great disco, guys!!! I'm dancing...
What am I doing, man?... Come closer... It's time to answer the question Is it possible to reach the moon with a laser beam? Let's test it! In 3, 2, 1... Go! Check it out! Is it reaching...? Do you think it touched it? No, man...
It's too far!... But looks like it did! Obviously I know the answer to this question The moon is over 380 000 km from Planet Earth So it's utterly impossible
for this laser beam to reach the moon! I believe this laser reaches up to 2 or 3 km That's very little! Now imagine 380 000 km! Do you know how much that is?
It's really far! It's like, farther away than going very far up to China... Like, millions of... What am I sayin'? I dunno! Man, it's really very far! So there's your answer, guys It's not possible to reach the moon with the laser beam Look! The laser is weakening...
The batteries are out... But even with almost no batteries
I'm gonna reach for the moon once more! Check it out! The laser is running outta batteries so it's time to end this video I hope you enjoyed it, guys! If you want to see more laser videos leave many likes on this video and subscribe to the channel Lots of new videos are coming up soon! Right here you can see a couple of
new and very funny videos! Go see them! Once more, you can subscribe below. That's it, guys! Be cool
and see you next time!!!.
