First, Clifford Johnson helped make the very cool video Shine a Light, teaching kids about how atoms emit light.
Now he’s done it again with Laser.
[Click the "HD" button to see it in better resolution.]
It’s pretty good. I like the way the actors work, and how they’re dressed. I’d like to have seen more about why laser light is all one energy, and how it gets collimated, but sometimes you can’t put everything you want in a short video without making it murky. Still, there’s a lot of good basic stuff there. I think this will do well in the classroom, so any physics teachers out there, take a look!
September 21st, 2009 at 12:26 pm
And I work on lasers day to day (1.064 micron mostly), and I found it entertaining! Thanks!
September 21st, 2009 at 12:27 pm
Very cool
And I love how they used red shirts and blue shirts because we all know that “Knowing is half the battle.” But do you know what makes up the other half?
25% Red Lasers
25% Blue Lasers
http://juliasherred.com/archive/Lasers-T.jpg
http://juliasherred.com/archive/The-Battle-Shirt.jpg
Go Joe!
September 21st, 2009 at 12:37 pm
That’s LASER – light not sound as nearly caught me out in a recent quiz. You have to read closley folks.
September 21st, 2009 at 12:39 pm
I’m not going to make any jokes about the boy-girl/boy-boy /girl-girl pairings getting excited – that would be puerile – just know that the puerile side of my brain came up with them.
Why are some lasers just pulse lasers while other lasers are continuous? Is that just a function of the light source or is that a function of the materials used to lase?
September 21st, 2009 at 12:42 pm
Psh… who uses CD players anymore.
Very informative. I’m not really good with physics, so I kinda just nodded my head and smiled at a few of these things… but I understood the general idea of what they’re talking about. So I guess it worked! Someone who knew nothing about lasers knows… something.
September 21st, 2009 at 12:42 pm
My slow WLAN kills me … do the redshirts finally die?
September 21st, 2009 at 12:44 pm
Your blog, your grammar, BA
However if you send a femtosecond laser pulse through a grating you would see lots of frequencies. Although granted it is still coherent.
PS: I tried to get Siemens to sample me a 1.5 watt laser diode. The request must have amused them. I later checked the list price: $650.
September 21st, 2009 at 1:58 pm
I like the fact that Einstein was both a successful researcher (QM, relativity) and an inventor (refrigerators), but it was in lasers the two got together. (Poetic license, IIRC Einstein discovered the mechanism behind absorption and emission but didn’t get around to lasers.)
Let me see if I remember this… Roughly, lasers work by populating the hell out of higher electron energy levels of a material by a “pump”. (Usually by a current or a light source.)
So much so that these levels becomes “inverted” (exhibits inversion, in the lingo) with respect to their natural thermally populated state, more electrons than “holes” that is. Then when an electron spontaneously depopulate the level and emit light, it will stimulate others to do the same in an avalanche process that overcomes natural reabsorption.
So mostly the pump mechanism decides how you operate. For example, semiconductor lasers are often continuously pumped by a current, while gas lasers are often intermittently pumped by light sources.
(Then there are some lasers that “top up” inversion by temporarily preventing the cavity from lasing, to be able to emit really intense pulses. But that is another story.)
September 21st, 2009 at 2:02 pm
Oh sheesh, you mean lasers use light, I thought they used sound (Sorry, couldn’t resist)
September 21st, 2009 at 2:04 pm
My high school physics teacher used to describe lasers as “light under the command of Nazis.” So, not a bad video, but needs more jackboots in my opinion.
September 21st, 2009 at 2:25 pm
That’s really cool. I don’t have the time or the brain power to get into physics so stuff like this that gives me a rough idea of how things work are great.
Thanks Phil.
September 21st, 2009 at 2:35 pm
I will be definitely using this video this year in class. Thanks for the feature.
September 21st, 2009 at 2:38 pm
I was waiting to see how the single student would split in half as s/he left the laser.
- Jack
September 21st, 2009 at 3:15 pm
That’s a neat video, I might use it in class.
To elaborate on Einstein’s role in working out the mechanism: he first realized that if a light pulse is likely to excite an atom, it is equally likely to knock an excited atom back to the ground state (and producing a photon). This is stimulated absorption and emission. He also realized that an excited atom will produce spontaneous emission, in which the atom decays to the ground state and emits a photon. Stimulated emission and absorption can be understood completely classically (i.e., without photon talk), but to understand spontaneous emission you need quantum mechanics.
Ironically, nowadays, laser light is regarded as the ultimate classical source of light (even more so than thermal light), as opposed to single photon sources, or even more exotic entangled photon sources.
September 21st, 2009 at 5:22 pm
Torbjörn Larsson said ‘Then there are some lasers that “top up” inversion by temporarily preventing the cavity from lasing, to be able to emit really intense pulses’ This can be accomplished in several ways, there is a crystal called a Q-Switch which, when energized by a high voltage will become transparent at the lasing frequency. These lasers emit very short very high energy pulses. The other type of pulsed emission can be from a fiber laser using a semiconductor ‘seed’ diode that energizes a doped piece of fiber optic cable then with another diode to excite the fiber you can get a large pulse out of the fiber.
September 22nd, 2009 at 7:57 am
IIRC, Einstein also didn’t think that lasers would work and that, if they did, they wouldn’t be very useful because of the small return on the huge investment of energy.
Having worked for years in entertainment laser shows, we would use the excuse “I guess Einstein was right” when we’d lose one during a show.