[dorkbotpdx-blabber] Lazerz

[Jerry Biehler]

I thought I would share some of my photos of my new lasers since I can't bring them to the meeting because of safety issues.

I got two new lasers. Both made by Lightwave Electronics, now a part of JDS Uniphase. They are both Q-swiched diode pumped solid state lasers. They use 808nm (near IR) laser diodes (120 watts worth on the big one) to pump a Nd:YVO4 crystal. This will create a laser beam at 1064nm (IR). In one of the heads this is doubled though a KTP crystal to 532nm (Green), just like in a generic green laser pointer. Only this one puts out 6.6 watts, 1320 times the power of a generic green laser pointer.

The second laser is a little different. The 1064nm light is mixed with the 532 in another non-linear crystal (I believe a LBO) and the wavelengths are summed to 355nm which is just out of the visible spectrum in the ultraviolet range. This laser is putting out about 6 watts.

Both are q-switched. This is a device that is put in the Nd:YVO4 crystal's beam path and basically allows you to block the beam storing energy in the Nd:YVO4 crystal. When the path is restored the energy is dumped from the crystal creating a large spike of energy. This allows you to have a very high peak energy output. With either of these lasers I have managed to cut thin metals. With the green one I managed to get through .013 steel which we can't even do with the 150w laser at work. One advantage of these lasers is materials that tend to reflect the 10,600nm light from a CO2 laser absorb these shorter wavelengths. Also with the shorter wavelength you have a much smaller focus spot, about 20 to 30 times smaller. This means I higher power density and also higher resolution in the engraving or marking. These lasers are most often used in trimming applications for things like SMD resistors.

Some pics are in the links below. The UV laser is not much to look at since it is invisible. It does react nicely to fluorescent dyes in water. In the pics I used Rhodamine 6G. The green is incredibly bright. I shot it outside at night onto a piece of graphite I have been using as a beam stop. The reflected light off the black surface was still enough to light up the entire back yard. I let the beam hit my back fence to see how big it gets at a distance. After a minute or two on the same spot the fence started smoking and left a nice charred spot. Ooops!

http://www.flickr.com/photos/67292116@N00/sets/72157630308769936/

http://www.flickr.com/photos/67292116@N00/sets/72157630262276700/
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[Rob Nero]

Interesting. What are you plans for them?

[Jerry Biehler]

Probably going to tie them into the laser cutter I have been building. Thought about using fibers to deliver the beam but there is a pretty big loss when you launch a beam into a fiber. I does cut kapton pretty nice for solder masks. The 335nm one might do clear mylar.

Then there is always stuff like pumping dye lasers. A friend was mentioning about exposing photoresists with them. And I know they used these for stereolithography.

I am looking at galvos to drive these. You can do X-Y with two galvos (Basically limited angle motors with position feedback) and pass that through a f-theta lens which maintains the focal point at an angle. Though control of a galvo like that could be a little daunting.

-Jerry

[David Turnbull]

Sharks! DUH!

[Monty Goodson]

Those lasers look pretty awesome. Thanks for sharing!
I noticed the UV laser has almost 1500 hours on it -- how long do these high power diodes last?

Monty

[Jerry Biehler]

Actually, the UV one I have has 30,000 on hours and 20,000 UV hours. The green has 1500 hrs and about 800 green hours.

The lasers can last quite a while. From the guy that works on these, he says he has seen these Coherent diodes running for 60,000 hours. They do get weaker with age and also their frequency shifts. You can adjust the diode current for power and adjust the temp of the diode to get the diode's center frequency back to the optimal spot for the crystal. Also the THG crystal may need it's temp adjusted over time.

The diodes in the UV laser are specially matched at current wavelength, and temperature by Coherent. They are $4,000 a piece.

When it comes to optics everything gets more expensive the shorter the wavelength.

I am also working on another Spectra Physics head. This is a straight diode pumped yag head. It is pumped externally by two 40 watt fiber couple laser diodes. Should be able to get up to 20w average if I am lucky at 1064nm.

-Jerry

[Mark Allyn]

Folks:

I know that some of you have asked me why I don't use flashing, changing,
flickering and so on on my lighted clothing and jewelry.

This article, which I found on line, is a year old, but quite clear in
explaining about the problems with blinking and flashing light art.

http://www.straight.com/article-469716/vancouver/public-art-light-installation-angers-nearby-residents

They had light art at the Vancouver Olympics and the neighbors were very
unhappy.

Truly,

Mark Allyn
Portland, Oregon
www.allyn.com
971-563-7588

[Jerry Biehler]

I got most of the optics done on the laser cutter last night. I decided to see what I could do with it by moving the gantry by hand. These linked pics show the cuts in EDM graphite. The wire like thing in the pictures is a hair:

http://www.flickr.com/photos/67292116@N00/7674943716/in/photostream/

http://www.flickr.com/photos/67292116@N00/7674945728/in/photostream/

I have updated the build log with my recent work here:

http://www.buildlog.net/forum/viewtopic.php?f=16&t=264

-Jerry