Best collimated laser you've ever seen / owned

[jupiter8]

I remember reading that NASA was using a laser to measure fluctuations in the orbit of the moon, bouncing a high powered laser off a mirror array left on the moon during one of the Apollo missions. I was considering the divergence problem over the distance (~380,000km), it's amazing they can do this at all!

What's the best collimated laser you own or have owned?
What's the best collimated laser you've ever seen?

Has anyone played around much with trying to minimise divergence and got it down to values well under 1mrad? It'd be fun to try this kind of thing if one had the money to put into the pricey optics undoubtedly needed...

 

[aryntha]

My PGL-III-A 473 (AqPro) .. I don't know if it's just by chance or what, but the thing just does not want to diverge. Still almost a pinpoint at 40 feet. My PGL-III-C 473 doesn't perform as well, even though 473's are pretty good for divergence. I guess I just got lucky. I should measure it sometime, but the divergence is so low it may be difficult to measure properly

 

[lasersbee]

From what I had read... they use a corner mirror on the Moon
and only a few photons make the round trip...

Jerry

 

[Benm]

Going for under 1 mrad is, imo, best achieved with beam expanders (telescopes). It will still help if the beam being expanded has a good divergence/diameter ratio, which is essentially key since beam expanders allow you to trade one for the other.

I suppose the best divergence/diameter ratio i own is a plain and simple red laser diode collimated by an aixiz lens... though well adjusted dpss greens arent much worse.

 

[phoenix77]

The BEST laser for divergence that I've ever owned/seen is the "STEALTH" Model laser from "BLUESKY LASERS" @ 109mW's

 

[Benm]

What makes that laser stand out from the others?

I've seen my fair share of lasers, but i havent seen much extraordinary on the positive side. I suppose its fundamentally limited by diode output area and dpss crystal size for common laser types.

Much better divergence/diameter performace is available from gas lasers - even the simplest HeNe will probably outperform any diode based red easily when it comes to optical specs. On the other hand, a 200 mW HeNe would probably fill most of a room including power supply and such, so its not very practical to build one.

 

[Eidetic]

From what I had read... they use a corner mirror on the Moon
and only a few photons make the round trip...

Jerry

The first bouncing of laser light off the moon was called Project Luna See in 1964. It was a Raytheon model LHM-4 pulsed ruby laser giving 50 Joules output at 694nm. The head was four elliptical cavities around a single big rod, cooled by liquid nitrogen. There were no retroreflectors on the moon until '69, so they were looking for a very small return indeed!

I think it's GREAT to compare collimation of handheld lasers! Especially those homebuilt. It's a challenge. It requires thinking about the optics you're using beyond who makes them. It takes skill in making accurate focusing mechanisms. There should be a contest, classed by diode. Who has the best beam? Who's The Man?

 

[jupiter8]

Great stuff guys, I'm inspired myself to learn more about optics and try to achieve some really outstanding beam quality. I agree with Benm, my open long can red laser diode with an aixiz glass lens is the lowest divergence I own. I'm going to measure it this weekend. I'm hunting around for a green module at the moment and don't want to commit to the purchase until I'm sure I can focus the thing properly...

 

[kevinmassey]

I have a 10x beam expander, and a laser that already has divergence of .8mrad. .08mrad is pretty awesome, and the slow axis on my 445s is under .2mrad focused correctly .