Accurate Wavelength Calibration of an Etalon-Tuned Dye Laser

Abstract

A method to set accurately an etalon-tuned dye laser to any preselected wavelength within its lasing region is presented. The method involves a unique procedure to determine accurately the etalon thickness, so that the correct etalon order can be found for each wavelength and corresponding etalon setting. An equation relating the dial reading on the optical mount of the intracavity etalon to lasing wavelength is derived and evaluated for the Chromatix CMX-4 pulsed tunable dye laser. The procedure used to evaluate the equation parameters is described in detail. After establishing the value of all the equation parameters, a comparison is made between lasing wavelengths as predicted by the equation and as experimentally determined using laser-induced impedance changes to detect spectral lines in hollow cathode lamps. Agreement is found to be better than ±0.05 Å for all spectral lines used, with 68% of the predicted wavelengths within ±0.02 Å of their actual values. The micrometer drive for the birefringent filter, used in the CMX-4 to select an etalon order, is also calibrated using a quadratic polynominal equation, which gives predictions better than ±0.25 Å for all wavelengths tried in the regions of 5890 Å to 6050 Å and 6350 Å to 6720 Å, corresponding to the dyes R6G and R640, respectively.