Thermal, 209 free spectral range

A Fabry-Perot LCTF having a spectral bandpass of better than 20 cm has been employed for Raman microscopy [25]. Although exhibiting excellent image quality, the Fabry-Perot device exhibited moderate spectral resolution, low out-of-band rejection, limited free spectral range, and a small acceptance angle. It also requires a temperature-stabilized housing to avoid thermal drift in the bandpass. 

In order to reduce the bandwidth still further it is first essential to provide high thermal and mechanical stability, for instance by mounting all the optical components on a massive invar base. Oscillation on a single cavity mode can then be achieved by employing a tilted intracavity talon and bandwidths as low as 5-5-0 MHz have been attained. With this etalon fixed, the dye laser output can be tuned over the free spectral range, c/2L 500 MHz, of the main cavity by mounting one of the mirrors on a piezo-... 

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