PDA

View Full Version : Yet another 4ch Neos PCAOM thread



platinum
02-13-2009, 20:38
Hey all,

I have a NEOS 4ch PCAOM driver and crystal that I'm looking into using for my 3 Watt Melles Griot DPSS.

I have a sneaking suspicion that this is going to either be a challenge or not even worth my time. It's ok though, in the end, as I plan on getting something like an SP168 which should pair up well with this.

The driver model is: 6404-75-.1-4CH-5M
The crystal model is: 48062-1.0-.55

-The PCAOM unit is mounted on an L-bracket with a little swivel-type adjustment possible.

-My DPSS is putting out 3.2 watts at 532nm and has beam divergence in the ballpark of 14mRads. (thanks to the collimated dual-beam)

I plan on going straight to my DT40 scanners with a shutter in there somewhere in a new enclosure I'm planning.

-Jonathan

mixedgas
02-13-2009, 21:56
if your DPSS is polarized, you can use the pcaom on the 514 setting and be close. It may not be the most thruput possible, but it will work.

Steve

platinum
02-13-2009, 22:04
if your DPSS is polarized, you can use the pcaom on the 514 setting and be close. It may not be the most thruput possible, but it will work.

Steve

I probably should've mentioned the driver has been tuned for use with a CuBr system so the wavelengths are 578.2nm, 476nm, 510.6nm and 647/676nm (switchable).

I figured the 510.6 would be my best bet, but that's getting a little low to be worthwhile.

How much trouble would it be to re-tune F3 (510.6) to something higher? I read that an o-scope and other things (like knowledge) are needed...

-Jonathan

mixedgas
02-13-2009, 22:34
if its a non synthesized driver, its a crystal oscillator in a can, desoldered and replaced with one on a different frequency.. NEOS stocks them, or they used to. Try 510 and 578, as your are working in AO mode, not slow shear, and you might find it works well enogh as is for a single wavelength. rotate the crystal about the beam axis so to try both polarizations! Use a wattmeter or solar cell or something, as your eyes lie!

MY book has the freqsfor 532 nm for generation I pcaoms, but I have a person sleeping in the guest room/library/storage room right now. Ask me in the morning.

If it has the 633/647 switch, its almost certainly a fixed frequency driver.

Avoid the temptation to turn CHANNEL LEVEL pots on the driver internals, you need a RF milliwattmeter to do that without risking popping the driver RF amp or the crystal.

Synthesized drivers come with some wierd options like yellow hene, both yellow krypton lines, orange hene,green hene, the krypton 530 and 520 greens, 532 dpss green, deep red diode, and 442 for hecad. All are switch programmable and fine tunable with 2 16 position rotary switches per channel.
So if you have a friend with a 8 channel around, borrow it.

It costs about 18$ to have digikey program a clock can these days, but making it fit can be interesting. I'm pretty sure NEOS uses sine wave out, not TTL,for their cystal cans, so its buyer beware. I have had 8 of them programed, but landed a synthed 8 channel driver before I finished the project, and my closest green crystal is 514, so that wont help when you have 510 as its only a megahertz or so away.

RED gets the most RF, and Violet the least, so if you have poor diffraction and poor power transfer, you may try the red or yellow as well. My data sheet says 125 mW max RF per channel. These are 40-80 mhz freqs for the older ones and higher for the newer ones, so you need VHF capable gear.

Steve

VJ AIWAZ
02-14-2009, 04:54
the other problem i can see besides the wavelength is the fact that its a dual beam
what that means is that its 2 beams that are going though a bps cube/plate
so the output would not be polarized in one direction
but you can have it converted to a single beam
i waiting on mine to come back from service very soon
it left as a 2.5w dual beam melles(laser power) and is coming back as a 5+w single beam

--
John
VJ AIWAZ

platinum
02-14-2009, 11:23
. . .waiting on mine to come back from service very soon
it left as a 2.5w dual beam melles(laser power) and is coming back as a 5+w single beam . . .

I remember MechEng3 telling me something about this process. He left me with the impression that it wasn't possible with my model, but I can be a bad listener sometimes so maybe he meant that it wasn't possible to do at SELEM without proper tools.

I'd be interested in modding mine if it doesn't cost too much. (I figure it *does* cost a chunk of change)

-Jonathan

dave
02-14-2009, 17:19
if its a non synthesized driver, its a crystal oscillator in a can, desoldered and replaced with one on a different frequency.. NEOS stocks them, or they used to.



NEOS supplied a oscillator module top suit the 457 line for the 4 channel pcaom we had, so I get the impression they still stock and supply them :)

LesioQ
02-14-2009, 23:40
John,
If You're not planning to use this with other gas laser wavelengths simultaneously, the difference between 510nm and 532 nm passed through the crystal is just a degree or so of crystal tilt. Definitely not worth dealing with crystal freq sources until You really need to.

Since Your laser will have 2 orthogonal polarizations at a time, one of them will be somewhat impaired by crystal. By rotating the crystal You will define which will be, or both if crystal is at 45 degree angle.

Piotr.K

platinum
02-15-2009, 17:14
Sounds like I should shelve this thing until I get a proper gas-laser to pair it with.

Thanks for the info guys.

-Jonathan