Glued vs separate crystal

I know that there has been some discussion on glued vs separate crystals, but I haven't been able to find any definitive answers so far.

On a 50mW green laser, should i spend an extra 30% to get a separate crystal laser (see below link):
HL 532nm 50-300

I know that the separate crystal is supposed to cool better and thus provide a more stable beam, but... on a 50 mW green laser for star gazing is it really worth it?

Thanks for any with information!

CountThis said:

I know that there has been some discussion on glued vs separate crystals, but I haven't been able to find any definitive answers so far.

On a 50mW green laser, should i spend an extra 30% to get a separate crystal laser (see below link):
HL 532nm 50-300

I know that the separate crystal is supposed to cool better and thus provide a more stable beam, but... on a 50 mW green laser for star gazing is it really worth it?

Thanks for any with information!

Click to expand...

That's a tough decision, to spend more for seperate crystals on such a low powered laser. Well, the main issue with DPSS is temperature related. Crystal alignment is affected by heat. Sometimes this heat brings the crystals into a more optimum alignment, sometimes not. But higher efficiency means less wasted heat to be dissipated per mW of output power.

Let's say that laser really is 50mW. In order to get a true 50mW of output at 532nm with the common crystals used in DPSS, the 808nm IR pump laser diode is going to have to be running at a MINIMUM of about 150mW. And that is assuming that the crystal set is at optimum alignment to the IR pump AND one another. That is an awful big assumption at best. In real life conditions, that IR pump is probably being run at 250mW to 300mW, and crystal set alignment is not so optimal. With the typical glued crystal sets, typical efficiencies can vary wildly. It's very rare to find a set that hits 25% efficiency, let alone 30% or more. With seperate crystals and someone knowing what they are doing, you have a far better chance at getting more efficiency (more 532nm output per mW of IR input), and a more stable output. BUT, it all depends upon the experience of the assembler, and the time that assembler is willing to put into the build. Tweaking crystals can be a time consuming process. You would have to pay more for someones time to do it right, or at least better. Seperate crystal sets do tend to be more stable though because of the better cooling.

I've visited factories in China that make run-of-the-mill 532nm DPSS laser modules with glued crystal sets. The average worker there spends very little time on alignment. If it lases at all, it's good to go as far as they are concerned. It's someone elses problem on down the customer chain to decide if they want to put forth the effort to sort what they buy and bin them according to output power/efficiency. Most resellers do not do this, which is why you get the luck of the draw when buying lasers or laser modules from China.

Ultimately the decision is yours. If your seller is building these one-off for you, they may put forth the effort to do it right. The chances are more likely that they just bin the modules according to output power and pick you out a module that tests close to your build specs, albeit for a very quick power test. They will very likely not run it long term and graph stability of power over time unless you request that service. Whether or not they actually honor that request is iffy.

Bob

I would guess separate crystal is a better choice--better alignment and you don't have to worry about glue degrading with time and heat or crystal cracking from different rates of expansion of materials.

If you are prepared to spend for the separate crystal, I would go the little bit further and get the 100mw or 150mw. The beam will be very much more bright/visable.

MAybe buy ione in next lasersbtb group buy--in the most recent group buy an HL-532 150mw was $85--good buy at that price