to Smarter Every Day. So I'm in the Netherlands today and I'm hanging out with a buddy of mine
that I met through a research project. His name is Johan Kr...
- Reinink.
- That. So, anyway, Johan is a laser expert, and I've worked with him
on stuff on the Internet. So we're going to show you
how lasers work today. [Music] (Destin) So this is an
open cavity laser, and can you explain the main components
of an open cavity laser? - Here we have the laser tube, with a helium-neon gas
that amplifies the light, and we have at both ends mirrors that are
aligned to bounce the light back and forth.
- Should we fire it up?
- Definitely. [Click] (Johan) There's a 4 second delay.
It's a safety feature. - Alright. Sweet.
(Johan) Well a helium-neon laser
tube is just a glorified neon light. It's just... You have the electrical
discharge going through it, like a neon sign, And the special thing is you
have here two aperatures, and the light can bounce straight through. So at both sides of the laser tube we've
placed two high reflecting mirrors, and the light that goes through
the laser tube hits the mirror and bounces back in forth through the tube.
And each time it passes the
tube it gets amplified. You make this mirror slightly
transparent - it's 2% transparent - and each time the light passes, 2% moves out and you have,
like, a beam going on here. - Okay, so basically what comes
out the other end of the mirror is the imperfection in the mirror. If it was a perfect mirror we wouldn't
get any output from the laser, correct? - Correct.
- But because the mirrors are imperfect we do get a little lasing.
- Yep.
In this case, the laser is just
specifically made to reflect only 98%, and this is the 2% of the
light that comes out. (Destin) Alright, one thing I've
noticed is that inside the cavity the beam is much stronger. You can see the laser hitting
particles in the air. But downstream the photons that
are leaking out of the mirror...
It's not quite as strong. Is that correct?
- Yeah. The light circulating inside the
laser is far higher intensity. And if you hold your hand outside
of the laser and block the beam, you see that you catch the beam.
It looks pretty nice.
But if you hold your
hand inside the cavity, you'll block the laser from
amplifying all the light and the light won't circulate around,
and you don't have a laser anymore. (Destin) So it stops way on the other side. Even though we're stopping
it on this side of the tube, we don't get lasing on the other side. I'm waiting on photon torpedo
technology myself, so...
- I'm working on it.
- You're working on it? Excellent. But anyway, we want to
thank Johan for his time, and uh... Can you thank the
people who let us in, in Dutch? - Absolutely. (Destin) What...
Did you
just call me something? - Nee... Absolutely not.
[Both laugh] (Destin) Do you wanna get even smarter? Then check out this video by MinutePhysics. Henry explains what's going on
inside that helium-neon tube in one of his cool science videos. [Music] (Destin) We're going to do Laser Month.
Laser Month consists of a lot of videos
shot over here in Holland with Johan, Because he is a laser genius.
Can I call you a laser genius? - Definitely.
[Destin laughs] Alright, so now we're going
to play laser limbo, ready? - No.
- Why not? - It's dangerous.
- Aw, c'mon, laser limbo. Captioning in different languages welcome.
Please contact Destin if you can help..
No comments:
Post a Comment