The View Up Here

Random scribblings about kites, photography, machining, and anything else

A Tiny, Weird World

Posted by Tom Benedict on 28/02/2012

I just ordered four lasers off of Ebay. One was a 5mwgreen laser pointer. The other three came as a matched set of laser pointers, one each in red, green, and blue. The sum total for this science fiction excursion? Less than thirty bucks.

I gotta shake my head…

Years ago I worked at a really cool place called the Center for Nonlinear Dynamics. For an undergraduate who was trying to scrape by and pay for his degree without having to take out a loan, it was heaven. I remember very clearly when one of the researchers brought in a paper to show us. I think it dealt with instabilities in laser cavities. But the real reason we were all geeking out on it was that the laser cavity had been created using photolithography. It was the first time any of us had seen something like that before: a laser diode.

The guy who was bringing this around was almost bug-eyed at the possibilities. “Do you realize what this means?” he asked with an edge in his voice. “Lasers are going to become affordable! Who KNOWS what we might do?”

I ran the computers at CNLD. One of my jobs was to do backups and perform OS upgrades on all the machines. The OS came on quarter inch tape. It took about six hours per machine to do the upgrade. Three years later when I left CNLD, I was doing upgrades using CDROM. Upgrades took less than an hour. It was a brave new world.

After lunch today, one of my co-workers came in with a problem: We have a cross-dispersed echelle spectrograph that images the entire visible spectrum in a single shot on a CCD. He’s working on some changes to the CCD code that could speed up our readout times. But there’s a risk of cross-talk between the outputs of the chip that would cause ghost images if any of the pixels saturate. Saturated pixels are almost a given with spectroscopy, so he needs to be able to see if this is a problem. One way to test it is to shine laser light into the spectrograph and see if we get one line and only one line, or one bright line and one dim line (the ghost). Easy enough to do, but what if the line doesn’t fall in the right place on the chip for testing?

As we knocked ideas around, we realized we could shine several colors of light into the spectrograph at the same time. Hey, cool! We have red HeNe lasers, and we’re pretty sure we have a green HeNe laser at our summit location. That’s two colors. But more would be better. What about a red laser pointer? Turns out they emit at a different wavelength than a red HeNe. So that’s three wavelengths. What else could we use?

I searched Ebay and found a green laser pointer that would compliment the red one we already have. Then I scrolled down and found the three color set. Five minutes later I had four lasers ordered. They should show up just in time for testing.

So the lasers came full circle, in a manner of speaking, from research lab to consumer product, and back to research lab. What could have been a fairly involved test using a monochromator and a good bit of optics was solved using some stuff picked up off Ebay for a couple of bucks. Can’t beat it.

– Tom

P.S. They even run on AAA batteries! Rechargeable lasers!

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