Where can I get IR diodes, and how powerful of one should I get?

[Bearded_Galaxy]

I'm looking to make a greenie at least 100mW in power. Based on a *slightly* conservative estimate of the probable efficiency of decent- to good-quality crystals, about how powerful of an IR diode am I looking for, and where could I find one?

 

[HIMNL9]

If you find a decent crystal (say, 20% of efficency, with a good coupling), probably any 808nm diode from 500mW or more, can be good. (better something more, for take care about losses and misalignments)

But, i suppose you know, it's not easy to build a DPSS .....

 

[Bearded_Galaxy]

Wow, 20% is decent? I was pretty sure I read somewhere that there were 80% efficient crystals available, but I don't actually know if I did, or where I even would've seen that. You'd think, at such low efficiency, companies might just invest in actually green LDs, but apparently not. Do you know where I could get an IR LD around that power, and how much for? Man, that sure would need a LOT of driving current...

 

[photonaholic]

IR laser diodes - Google Search

KTP Crystal, KTP, KTP laser, Anti gray tracking KTP crystal, Potassium Titanium Oxide Phosphate

KTP conversion efficiency - Google Search

 

[Bearded_Galaxy]

One of the links mentioned 10-11% conversion efficiency.

My plan, right now, is to use the optics from the 50mW module I got from DX and just replace the LD.

And I tried searching Google for IR diodes, but I didn't really find quite what I was looking for, at least not in the way I wanted it. So, I was asking in an effort to get a specific recommendation from people here. If memory serves (and so far, it hasn't done too good of a job), I remember seeing 1W 808nm diodes on StoneTek, or HighTeckDealz, or one of those websites like them a while ago.

EDIT: Or at least you'd think companies might look into 1064 LDs, and eliminate the Nd:YVO4 crystals.

EDIT2: I really want a 5.6mm diode. And by, "really want," I mean, "I won't buy it unless it's."

 

[HIMNL9]

Well, no, 20% of efficency in conversion is considered good, for DPSS lasers ..... i'm not sure if the maximum actually obtained from ambient temperature assemblies is still 25%, or if someone have finally reached 30% ..... anyway, as basical principle, if you double the energy of the outcoming photons, you can never expect an efficency more high than 50% ..... then ofcourse you must considerate the loss from coupling, alignment, polarity rotation, faces reflection, the part of the energy dispersed from the crystal in form of heat, and so on .....

The maximum theorical efficency is obtained using a collimated IR diode with FAC lens, that can collimate all (or the maximum possible) of the IR in a point inside the crystal, typically from the middle to 3/4 of the lenght of it, with the crystal perfectly aligned and the polarization planes from the diode and the crystal axis in the range of one degree from the optimal one .....

Usually, instead, the normal green modules, uses an open can diode, with the face of the emitting chip the more close possible (half millimeter, usually) to the input face of the crystal ..... less cost, but also less efficency .....

If you're planning to use the crystal of a 50mW unit, probably you can get from it 100 or 150mW without too much problem, but over this, the heat generated start to be too much, and the crystal can become damaged ..... considering the better alignment and polarization that you can get from these assemblies, can be possible to obtain 100mW from a 600/650mW of IR, and maybe 150 from a 900mW of IR, but can be difficult to find 5,6mm IR diodes that emits 900/1000mW ..... open can units, ofcourse ..... and also, you need to heatsink your unit very well, or your crystal will become soon a cooked ex-crystal ..... (also, all the modules rated 200mW that i've seen til now, that effectively emits over 170/180mW, uses 9mm IR diodes, not the 5,6mm ones)

 

[Bearded_Galaxy]

What I have is a DX 50mW green module (if I didn't say that explicitly) and it uses a 5.6mm diode, and I've no idea the probable repercussions of drilling it out for a 9mm.

 

[Cenobite9]

Kind of a dumb question but what actually determines the final output power of a green laser? Is it the power of the 808nm IR or the driver or both? The reason I ask is because I have an old 5mW green that died some time ago and I suspect the 808nm diode is what died. If Ireplace the old IR diode with a more powerful one will it still be a 5mW laser because of the pump driver?

 

[HIMNL9]

@ Bearded-Galazy: no, it's not a good idea, that can destroy the crystal ..... and also in case you unglue the crystal holder, still you need to do too much work (the 9mm open can diodes have the chip at different distances (quotes) that 5,6mm, from the base, so you need to recalculate all the quotes ..... i guess it's more easy to build it from new, than just modifying an existing one, sorry.



@ Cenobite9: as i've said, there's a lot of factors that influence the output power ..... the power of the diode is just the first one ..... then there's coupling crystal/diode, alignment, polarization, crystal type and quality, and so on .....

I guess that, if you get one of these 300mW 808nm diodes from ebay or similar, and reach to realign it correctly in your old module (ofcourse, if is the diode that is dead, and not the crystal), you can end getting 40 or 50 mW of green from it ..... but probably you need to decan the diode, cause in these cheap modules, the coupling from diode and crystal is usually obtained just placing the diode the more near possible to the crystal, like, half millimeter from the face of the crystal and the face of the emitting chip, so an open can is needed for this.

 

[Cenobite9]

Gotcha... these dpss lasers are definitely a lot more complex than the standard diode lasers I'm used to. It's hard to say what part actually died because the laser just got really dim then quit working all together.