eBay Nd:YVO4 + MgO:PPLN module.

[middlemunch]

The PPLN crystal will have been aligned very carefully to the Nd:YVO4 laser gain material - fabry-perot cavity. The epoxy CQ Laser use to make this assembly isn't great. With just a thin Cu cover over the unit the amount of mechanical protection is extremely limited - even the slightest bit of pressure will misalign the PPLN relative to the Nd:YVO4. Once this has happened all is lost.

To avoid this I would absolutely recommend the above suggestion of sticking the base of the unit down with epoxy. I wouldn't bother trying to conductively cool around the Cu cap as this is not in contact with either crystal. (Ok there is thermal paste around the inside, but this stuff still has such a low coefficient compared to the silicon base.

Good luck!!

[steve-o]

Welcome to the DIY Green club LS. Mine's on hold for a rainy day project for a little while ..

[planters]

The only reason to use pressure is to cause plastic deformation of the microscopic roughness on the surface. The module should already be pretty flat and smooth. Why not use an optical quality AR coated sapphire window and just enough pressure to retain the position. Keep the components exquisitely clean and the added benefit is the lack of a thermal bridge over the hottest region (the aperture). This has been done before.

[logsquared]

The problem is "just enough pressure". I have no idea how much pressure that is?? Just a bit "too much" and its $200 out the window. I'm going with the glue I think. If I put the thermistor on the top the temp differential across the glue joint shouldn't matter too much.... I hope.

The only reason to use pressure is to cause plastic deformation of the microscopic roughness on the surface. The module should already be pretty flat and smooth. Why not use an optical quality AR coated sapphire window and just enough pressure to retain the position. Keep the components exquisitely clean and the added benefit is the lack of a thermal bridge over the hottest region (the aperture). This has been done before.

[planters]

Actually, the pressure could be almost insignificant, but the glue sounds conservative and less scary.

[chad]

I had some questions for them. Here are the answers, something might come in handy.

Here are the answers from our technical support staff.


1) Do you have a reference design for a 1 watt green?
We have 1-w green laser.
2) Does the 1 watt green need an output mirror?
Our mGreen based green lasers do not need output mirror.
3) Do you have a graph of temperature vs green output?
Please find the attached one which indicates that the x axis is temp. (C) and the y axis is green output.
4) What is the optimum temperature for the module?
For the module, we have different design: in a range from 20 to 30 degree C.
5) How should the module be bonded to the heat sink?
By using Indium foil, glue and EPOXY.
6) Do you have STEP or IGES 3d cad files for the module?
Please find the attached application notes of mGreen module.
7) Can this be scaled beyond 1 Watt?
How about the exact value of Watt do you want? We have tested around 2-W output.
8) Do you have any modulation characteristic information? These will need to be analog modulated to ~30 Khz, or as close as we can get.
Actually, no. We do not have this kind of driver.
9) What is the diameter / divergence and M^2 typical of the beam.
On the outpu surface, the diameter is around 150 micro. 10-15 mrad for full angle. The M2 is 3-4.
10) What is the 1064 / 808 output in the green beam. Do I need an external IR filter?
We have a filter in our 1-W green laser. For mGreen module, the leakage is less than 100 mW. It is better for you to use a filter after mGreen module.
11) How tight does the pump diode thermal regulation need to be?
Sorry, I cannot understand your question.
12) Do you have any more detailed information other than: http://c2clink.com/productspecificat...e(English).pdf
What kind of information do you need?
13) What is the polarization of the green output?
linearly polarized.

They didn't send the attachments. I will ask again.

chad

[logsquared]

Thanks Chad. Can you PM me the email address you got through to them with? It seems they take a week or more to reply to eBay
messages.

I wonder if they meant they tested these chips to 2W or some other lab set-up?

[krazer]

In the initial thread about these modules at http://www.photonlexicon.com/forums/...act-Laser-Cube there is a paper posted which talks about getting 7w of green from 15w of pump power (400um fiber), using a similar size doubler crystal (2 mm × 2.5 mm x 0.5 mm) but a larger nd:yvo4 crystal (3x3x5mm, 0.5% doped). That said, their spot size was only 400um, which should be able to fit on the ebay modules, so the only fundamental difference between the ebay system and the one in the paper is the ebay laser is 1% doped vandate, so the pump is absorbed over a shorter length, which of course reduces the maximum pump power you can get away with, but with adequate cooling it seems like you should be able to get away with pumping these modules at 6-10w, which would give 2-5w watts out. Only time will tell...

[dsli_jon]

Here are the answers from our technical support staff.

..Wow - so much for "THAT'S SO, SO EASY!!"

Well, nothing great ever comes in a day.. We'll get there with multi-watt greens you can fit on a trisket, no-doubt..

keen thread..
j

[steve-o]

Can't you just bounce a 10,000 watt tungsten filament lightbulb between 2 mirrors, put a green filter in there somewhere and be done with it?