testing a Coherent DPY315M-100

I recently bought a Coherent DPY315M-100 on ebay, but it seems I got myself an expensive doorstop. I do not have the Coherent analog controller, so testing is a little difficult, but as the head is physically damaged, I don't expect much.

I grabbed the pinout of the head from sam's laserfaq (pin 3 +, pin 4 -), the coherent compas 315m is the same thing. I don't have fancy TEC controllers, so I just ran for a short time about 1A though the laser diode, but no output whatsoever. Is this normal around 1A or should I go higher to determine if it really is broken?

For those of us who can't recall, what IS a DPY315M-100?

It's identical to the coherent compass C315M, a pretty epic green laser for holography. See here for the history.
I just tested it at 1.5 amps, and a few mw of green came out, so that works. But if I test again, the output is slightly lower. How strongly does the output depend on the temperature of all the components, and how high is the threshold for green output normally?
Anyone here actually familiar with this laser?

As a TEM00 green module for holography, it's very dependent from the correct temperature of the crystal set ..... usually these units are sold with their own driver/TEC controller PCB ..... your one had not it ?

If not, you need to find one, or at least the schematic of one of them for DIY it ..... i don't have the schematic of this unit, sorry .....

I don't have the coherent analog controller, but it can be powered with 3 TEC driver and a LD driver. I just shortly power the LD to see if it's working. Even at higher currents, the output is still only about a milliwat. How critical is the temperature of all the component? My guess would be that it doens't make the difference between 1mw or 100mw.

The temperature is extremely critical. I believe those use LBO for doubling, in which case one degree C can mean the difference between light and no light. It's good you're seeing some output, though, even if it's not close to what it's rated for.

It's not too uncommon to run across PSUs for those on ebay.. I'd keep a lookout for one since building a driver and temp tuning that system yourself will take some time.

No, it's very critical ..... few degrees, also just a pair more or less, can affect the output greatly.


EDIT: EF beatened me in speed :beer:

EF: it uses a 2x2x5mm KTP crystal, the Coherent Verdi uses LBO, but that's a completely different class of lasers. I look regularly for coherent stuff, but those controllers only rarely are on ebay. This laser uses normal Nd:YAG and KTP crystals, is this stuff also very temperature critical in this configuration? The average green pointers uses the same type of crystals but don't have any temperature regulation.

The "normal" assemblies don't have temperature regulation, but are usually glued crystals pre-matched, non critical, and multimode (and, also, they have a temperature range ..... if you cool or heat too much them, beam fade away ..... only, the tolerance is much bigger)

For single-mode crystals assemblies, the thing is different ..... there are so much types .....

Single mode crystals are much more critical in temperature also if are KTP ..... maybe not all as LBO, that are 1 or 2 degrees criticals, but also them have their own working temperature ..... well, yes, there is a particular type that have a 0,2/0,3C tolerance, for the peak working zone, but i think is a very expensive one, like, the 4x4x10mm units with around 50% of efficency ..... and for a worse possibility p), some single-mode second-harmonic KTP crystals have a working temperature that is around 70C (yes, they need to be heated, not cooled) ..... And the worse is not finished, there is a type of KTP crystal that rotate AND change the type of the polarization of the beam changing the work temperature, so it's linear around 31C, circular around 40C, linear but shifted by 90 degrees around 49C, circular again around 57C, and linear rotated 180 degrees around 63C , all from the same crystal (i don't remember all the other types, but i remember i've read in the past about other different types of KTP ..... sorry, but is practically impossible to keep in mind all of these types)

So, without know exactly what type of crystal is in your unit, is hard to say you what is the needed temperature that you have to give it, and the required tolerance, sorry .....


EDIT: just thinking at your crystal size ..... it don't look as a "standard" crystal, with 5mm of lenght, it look as a more efficent that "standard" ones ..... or, at least, all the standard ones that i've seen til now in 2x2mm, was around 3mm of lenght, not more .....

The supply you are looking for is named:
COMPASS315M you probably know it.

Let me know where i can find the cable from Power unit to laser box....

i have 315M cables with a 4-5 foot length.........

send me a PM if interested, Dave