Topic: Proper way to setup a 532nm DPSS for Analog Modulation

[Alfa Romeo]

good thought,
one that has captured many hours of confusion. these are from Lasershow Parts.
45 degrees is the starting point yes i agree. I dont have a power meter but a photocell will show relative power.

waste beam thoughts, this could be either the pass color, not being passed or the reflect color not being reflected. bottom line, notice the color of the beam from the back of each dichro!

if the amount of red that is not reflected by the reflect red dichro is very little, the rest must be reflected. but if the amount of reflected green that is not passed through the reflect red is quite a bit does the angle affect this.

i have for the most part focused on the back side waste beams for adjustment of the dichros. i agree with hyena about reflect angle range being quite wide +-15 degrees confirmed.

its the reflecting the pass color that drives me nuts!! i think its too much.
ie. oops there goes more green, and more and more!!!!!


maybe mock it up on the bench one more time, using relative waste power levels.

I might post some pics of this.

any thoughts, experiences, results please share. all thoughts would be welcomed

WASTE BEAMS SUCK!!! USABLE POWER RULES!!!!!

Later
pat

[James]

It looks like you have overcome the green thermal problems.

Did the picture I drew for post #5 make any sense at all?

The idea is to use metal plates about the same thickness as the parts you want to temp control. Each plate is temp driven by it's own TEC (or just heated with a power resister).

The plates can be bolted together with thin fiber glass (circuit board material) between them and nylon bolts.

This way you can make a single, solid unit with some precision in the alignment and distance between the optics.

I like your solution but it looks very fragile and open for dust contaimination.

James. 

[Alfa Romeo]

yes james it made sense. thanks
I'll bring you up to date. 


1. controlled (tec) cool diode, diode housing and IR focusing lens's
2. controlled (10ohm res) warming of ND:YVO4 KTP crystal
3. thermally insulate the two.

i used .02 inch thick pcb (after stripping down to bare fiberglass) from dvd sled parts to put between brass crystal holder and diode housing. the thinnest i could find in the junk bin!

made up a heater assy to put on top of crystal holder. used 10 ohm resistor and a 10k ntc thermistor , thermally bonded to aluminum using Arctic silver epoxy (the best!). closed loop drive circuit, will hold 100 degrees (or whatever)with varying diode housing temp.

moved diode .02 closer to crystal.

confirmed focal point using red diode in place of ir diode. tried using camera to see ir and beam. easier to use white paper to find hotspot. this was not very accurate and still may be a problem. question: how to focus an ir beam?


adjusted crystal holder for maximum output with min ir diode current, while modulating and getting rid of the dreaded double beam. this was extremely difficult and since then have found an easier way to this.

mounted everything together and tested several temps looked promising but the dbl beam pissed me off and i took it all apart again.

need to find out what the dbl beam is and correct is.

Andrew mentions optical feedback controlled modulation. i will implement this, what did i do with that photo cell??? thinking out loud, photocell on plus input for reference,  modulation on minus with neg feedback adj. andrew?? this wont fix the double beam, but will be the fixall for linearity, correct?

just ordered my 2w 9mm pump diode. should have the modulation circuit ready asap.

a few pics for ya and more soon.

later
pat

[James]

"IN GOD WE TRUST" !!! 

James. 

[Lazerjock]

"confirmed focal point using red diode in place of ir diode."

Be careful using a red diode to set focal point. The red 650nm wavelength is significantly different than 808nm. This is something we deal with at work every day except we are using 1550nm. Even though we are only talking nanometers it makes a difference when setting optics. It may be close enough for what you are doing though.

LAazerjock