green lasers

[Mandy D]

4 minutes ago, PeterW said:

Diode pumped solid state lasers, most of the existing green ones are actually 880nm(ish) IR diode pumped… this causes an and containing crystal to lase at 1064bm, which is then doubled to 532nm. So you’ve got IR in there you don’t want/need that should be filtered out so that the end user only gets the green that want. Without a spectrometer you won’t know the balance of visible to invisible power. The “cold proof” ones that are emerging (seem to be 515-520nm) are direct diode ones that only emit the exact colour you want… no IR, no doubling etc. 

Peter

Ahh, so not a simple laser, then! Essentially, you have two sources of laser light; one at 1064 nm and the other, which you want, at 532 nm. Thank you for the clarification. I was unaware that commercially available lasers operated in that mode.

[Louis D]

23 minutes ago, Mandy D said:

Ahh, so not a simple laser, then! Essentially, you have two sources of laser light; one at 1064 nm and the other, which you want, at 532 nm. Thank you for the clarification. I was unaware that commercially available lasers operated in that mode.

Mostly just the 532nm green ones.  Beautiful green color, but nasty IR emissions which can easily exceed the 1mW or 5mW 532nm rating by 10x from what I've read due to low conversion efficiency.

[PeterW]

Yes, sort of “un finished” photons from earlier in the process contaminating the nice green ones you want. The whole process is temperature sensitive, hence these ones die in the cold, the new simple direct emission ones give you what you want immediately and should be less temperature sensitive. (I make an LED change between orange and green with the help of liquid nitrogen… expect a laser diode would behave similarly, but might just break it).

 

peter

[Louis D]

5 hours ago, PeterW said:

I make an LED change between orange and green with the help of liquid nitrogen

Cool!  I've never heard of that before.

[jjohnson3803]

On 01/01/2023 at 03:37, michael8554 said:

In the UK lasers are frowned upon because of the danger to air traffic, which we have a lot of, so more than1mW is illegal to sell.

Check out the  rules for SA.

Michael

Way too much air traffic near / over me to get a laser.  The Federales take an extremely dim view of lighting up cockpits, even by accident.  YMMV.

[Louis D]

31 minutes ago, jjohnson3803 said:

Way too much air traffic near / over me to get a laser.  The Federales take an extremely dim view of lighting up cockpits, even by accident.  YMMV.

Luckily for me, they fly into the local airport following a north to south route due east of me, which is completely obstructed by trees.  Thus, my laser would only cross paths with a few random "fly-over" planes at high altitude where the laser angle would be too far below horizontal and too diffuse to have much if any effect on a cockpit.

[RT65CB-SWL]

If you observe near any civil/military/emergency services aerodrome... forget it!

 

[Louis D]

Notice that in all cases, it was a deliberate attack on low altitude aircraft with active tracking by the perpetrator.  Pretty much none of these conditions apply to astro laser usage.