Laser-power fluctuations: An analog signal-correction technique

Abstract

A simple and inexpensive analog technique which corrects spectroscopic signals for pulse-to-pulse fluctuations in the output power of an excitation laser is described. The technique is applicable to both linear and nonlinear spectroscopy and, in the latter case, requires no fast electronic function generator. This design yields an improved time-constant characteristic which parallels the approach of the effective time constant toward RC. Furthermore, since this improvement does not require any preintegration, pulse shape information is preserved. A description of a photoacoustic (PA) spectrometer which incorporates the signal-correction device and which relies on the photogalvanic effect for wavelength calibration is presented as an example. Finally, signal-corrected PA spectra of the S1←S0 transition in azulene are presented.