Manual for the Coherent Sapphire 532-300

[andisor]

Hi guys,

i'm looking for a manual for the new Coherent Sapphire models. On the Coherent support page i couldn't find any and the support doesn't answer my emails.

I was able to get my hands on a used Sapphire 532-300 FPT FT, but it does not come with a manual and the driver is completely different from the one i have on my old Sapphire 488-100. I need at least the description of the power plug of the driver and of the analog interface. The laser is with an fiber optic termination and I'm curious if i'm lucky and works also in slm mode.

Did someone tried such a laser for holografy yet?

Best regards

Andrei

[Joe Farina]

I can't help with the manual, but I recently bought a similar Sapphire 532-300 (formerly fiber-coupled) from Dave on Facebook. Dave said it worked for holograms, and that was good enough for me. I haven't tried it yet. By the way, my Sapphire 488-200 does appear to mode-hop once in a while (at certain power settings), but I don't think it's a big deal, because it doesn't happen very often.

I'm wondering if anyone has tried the microscope-slide method (projecting interference fringes on the wall) to find a good operating point for Sapphire lasers?

An optical spectrum analyzer is on my wish list, but unfortunately these are big $$$$$.

[andisor]

Hi Joe,

the microscope slide does not work as good as a home built Michelson interferometer. With it you can also check the range of the coherence length.

I did not see on my Sapphire 488 yet mode hops, but i'm sure it is having them. I'm using all my lasers only with pasive cooling and after 1-2 hours of operation the heat sinks are geting warm and at some point you will have them. I saw also my Coherent 532-200 making them when to warm from time to time despite its ring cavity. I think i have to implement on all my lasers the stand-by input to avoid the warming and to save some of the ld life span.

What do you mean with 'formely fiber coupled'? Is the laser, without the fiber optic construct, properly colimated or did Dave exchange the fiber with a colimating lens? My saphire 532-300 FPT is still on the way to me .

Best regards

Andrei

[Joe Farina]

Hi Andrei,

Thanks for the tip about the Michelson! Sounds like a very good idea. That's fascinating that a ring cavity (Coherent 532) has mode hops. I think that for many types of lasers, this is something that can be accepted and dealt with.

I could be mistaken, but I thought FPT FT means fiber-coupled. I don't have the laser in front of me now, but previously I looked up the Coherent model number, and I'm fairly certain it indicated that this was originally supplied as a fiber-coupled laser. So, I'm guessing that the fiber on my laser was removed at some point. I haven't powered it up yet, but based on Dave's photo of the beam, it is reasonably collimated. (But divergence looked rather substantial.)

Joe

P.S. (Edit): I just noticed that two posts down in this section, Dave showed the laser I bought (and which you inquired about). He also listed this laser for sale on Facebook, and had more photos there, including the one with the beam. If you're on Facebook, you can scroll down to the same approximate time period (he posted both at about the same time), and maybe find those photos (or maybe use the search feature). I'm not too good with Facebook.

[Din]

... it is reasonably collimated. (But divergence looked rather substantial.)

Joe

Joe
a laser cannot be collimated and have a divergence. The beam exiting the laser is always diverging because it's in the nature of the Gaussian profile (I can give you the mathematics of it if interested). There is a parameter known as M² which determines the degree of divergence, ie the deviation from Gaussian, of the beam. The M² parameter also determines the mode structure of the beam and the ability to couple to a fibre. Ideally, M² = 1, but no actual laser can achieve this.

[Joe Farina]

What I tried to convey with "reasonably" collimated (a poor choice of words, I admit) was that it's not wildly diverging coming out of the aperture (and that it could be "tamed" with lenses).

[BobH]

A collimated beam has a divergence. It's 0.

[Din]

There's no such thing as a zero divergence beam. Any plane wavefront would have to be infinite in extent to have zero divergence. Diffraction causes any finite plane wavefront to diverge:

"Diffraction causes light waves to spread transversely as they propagate, and it is therefore impossible to have a perfectly collimated
beam."*

*"Introduction to Laser Technology". Melles Griot Catalog (PDF). Melles Griot. n.d. p. 36.6. Retrieved 25 August 2018, p 36.6 (Equations 36.7 and 36.8. )(http://file.lasersaur.com/docs-thirdparty/Lasers.pdf)