by 142laser » Mon Sep 30, 2013 7:59 am
The microscope slide interferometer does not have enough resolution to tell much if anything about longitudinal modes; it may work for checking a diode laser but not a crystal laser; I bet a stable HeNe looks great and has 5 or more modes with a 1GHz linewidth. I wish it was this easy to check SLM lasers. If theye were a second mode at say 30% of the main mode height you would get the stripes on the holograms but the image from the slide would look fine. You can only tell gross malfunctions I believe. Who do you know in CA with a scanning interferometer?
Fringes shift for other reasons...loose optic? Heat source added to table recently causing slow thermal expansion? Check everything else you can think of in case the problem is not the laser at all.
The microscope slide interferometer does not have enough resolution to tell much if anything about longitudinal modes; it may work for checking a diode laser but not a crystal laser; I bet a stable HeNe looks great and has 5 or more modes with a 1GHz linewidth. I wish it was this easy to check SLM lasers. If theye were a second mode at say 30% of the main mode height you would get the stripes on the holograms but the image from the slide would look fine. You can only tell gross malfunctions I believe. Who do you know in CA with a scanning interferometer?
Fringes shift for other reasons...loose optic? Heat source added to table recently causing slow thermal expansion? Check everything else you can think of in case the problem is not the laser at all.