|Nelium-neon laser pointer. |
Sure, you've seen laser pointers before, what are they, maybe $3 at the corner gas station? But those are laser diode pointers, tiny solid state devices that run on a watch battery. This is something far more exotic, a relic of a time before the very existence of laser diodes. Gather 'round children and I will tell you a tale of those times.
Back in the stone age, I'm talking here about maybe 1990, lasers were big things made of glass tubes or ruby rods, fed by high voltage power supplies. There were definitively not things you held in your hand. Then one day I see this astounding device in a catalog for the bargain price of only about $300. Having no children or other responsibilities, it seemed like a reasonable thing to buy at the time, and I am now very glad that I did, because I cannot find any evidence of this product ever having existed, not even on eBay. But I have one, and it still works.
It is a hand-held helium neon gas discharge laser that runs on two 9V batteries, for about 15 minutes. What you're looking at is the laser tube in operation with the side cover taken off. Notice the bit of foam stuck between the battery and the circuit board with a round blue capacitor on it? I stuck that in there because otherwise the miniature high voltage power supply arcs over to the battery case.
You really need to watch the spin video of this sample (click the Spin link on the left) to see the tube from all directions: We shot the rotation with the device turned on, and when the laser beam points directly at the camera, it hits the CCD and creates a lovely diffraction pattern as it reflects back from the inside surfaces of the lens. (No, it didn't damage the CCD.)
One very interesting thing to note: The color of the glow you see inside the tube is different from the color of the light coming out of the laser end. The light coming out the end is the neon red emission line, while the color coming out the side of the tube is the helium lavender/pink glow. Think about it: This is a completely uniform, isotropic gas, yet it's glowing in two different colors depending on what direction you look at it from. How can this be? That is the magic of the laser: The cavity mirrors organize the light from the neon line and stimulate (the S in LASER) it to be emitted only in line with the beam. The helium emission occurs in all directions randomly.
I thought I had lost thing thin, and when it turned up in my office I was overjoyed, it is one of my favorite gadgets, quite a marvel of miniaturization even if it is a hundred times bigger and a hundred times more expensive than the current model.
Source: Theodore Gray
Contributor: Theodore Gray
Acquired: 28 February, 2009
Text Updated: 1 March, 2009