Converting the OEM Lexel 88 argon laser head
for holography

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Shown are fringes of an interferometer where the path difference is almost 4 meters (folded back and forward several times) - this means the coherence length is at least of this order of magnitude.

Note added

I now have checked the longitudinal mode structure with my scanning Fabry-Perot interferometer, see the results here. In brief, there is clean single frequency operation at 514nm and 496nm, however things don't work so well at 488nm.

Finally here some power measurements with an Ophir thermistor head:

Pink means TEM00 all line, and the other colors refer to 514, 488, 476nm, resp, using the prism.) The plot on the right shows the single mode power when using the Lexel etalon, the power loss is not at all bad !

Tube voltage versus current:

I had ruined the magnet by inadvertedly powering it up without cooling - I had to get a surplus one, here are pics from the delicate operation, where the tube had to be removed and stripped down to its beryllium oxide core:

Some useful links for Lexel 88 data:

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