TEC's as heaters @ 60 - 70 C

George Herold · 2014-12-02T00:46:32+00:00

I got around to testing a whole bunch of laser diodes, which we tune to the 780 nm line of Rubidium. A number of them (~10-20%) have a long wavelength, and I'll have to cool them to T < 10 C*. I'm a bit worried about condensation. (I just have to get below the local dew point.. is that correct?) So I could hold these diodes back, we've got plenty. I then thought that I could run 'em up at 795 nm**. It seems a bit of a stretch, ~11 nm, +44 K to ~70C. but with a grating external cavity you can pull the diodes fairly far.. +/- 2.5 nm, 10K. And I can get'em to output 795 at 60 C without much trouble. (Well tweaking the pieces at 60 C is hot work...) So is it crazy to think about running the laser head up at 60-70 C? It's not stressing the TEC (less than 1/2 max current at 60C), and I was thinking I could make a little "tea cozy" to go over the laser head. A picture of the laser head can be found if you scroll down here, *diodes have a wavelength ~ 784 nm at 25C and tune at ~0.25nm/C ** 795 nm is the other "D line" of Rb. Physics-wise the 795 line is nicer because it's the P-1/2 state and is simpler magnetically. (fewer magnetic states.)

Dec 02, 2014 24 Replies

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George Herold 11 years ago

Ouch, I hope they weren't all bought on your dime.

I'm afraid my optics is fairly crude by your standards. The TEC controls the entire mirror mount/ grating/ lens tube assembly. Yeah, TO-18 a 5.6 mm package (Sanyo DL-7140-201S) I've got it stuck in a Thor labs lens tube. (Which is the tweaky part.) I cycled it up and down 0 - 60 C, three times while I was doing other things. The lens tube seems fine, but the mirror mount adjustment screws moved by ~1/10 of a turn. That's not a show stopper, but it is inconvenient. (OK I don't really know that the adjustment screws moved... but they both had to be re-aligned.)

More cycling torture.. (cue maniacal laughter.)

George H.

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Bill Sloman 11 years ago

Joerg wouldn't see it that way. He sees cycling as a pleasure.

Bill Sloman, Sydney

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Bill Sloman 11 years ago

ser head.

(maybe a bag of silica gel to absorb the water?) It's already has a plex iglass cover (with a hole for the light.) I have taped a microscope cover slip over the hole, but as you say one then has to be aware of etalon fring y things... and reflections back into the laser.

If you get your cold gas by boiling it off liquid nitrogen, it is very dry indeed. It would dry the silica gel. Which was presumably what Martin Brown meant by "dry nitrogen".

Bill Sloman, Sydney

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Lasse Langwadt Christensen 11 years ago

laser head.

t. (maybe a bag of silica gel to absorb the water?) It's already has a pl exiglass cover (with a hole for the light.) I have taped a microscope cove r slip over the hole, but as you say one then has to be aware of etalon fri ngy things... and reflections back into the laser.

y indeed. It would dry the silica gel. Which was presumably what Martin Bro wn meant by "dry nitrogen".

I wonder if leading the air past a peltier that is colder would dry it suff iciently

-Lasse

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whit3rd 11 years ago

That suggests that you could conceivably put the whole cold/hot assembly into a quiet, dust-free, moisture-absent container by sealing it into a vacuum. Absolute pressure sensors routinely hold a vacuum for years of operation... it can be a pretty soft vacuum, for this application.

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