LASER POWER FLUCTUATION: AN ANALOG CORRECTION TECHNIQUE FOR SPECTROSCOPIC SIGNALS
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Date
1982
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Publisher
Ohio State University
Abstract
A pulse-by-pulse, analog, signal-correction technique is described in which spectroscopic signals are corrected for power fluctuations in the excitation laser. Pulse-to-pulse power fluctuations in pulsed dye-lasers can pose serious signal-correction problems, especially in non-linear spectroscopy where the signals must be normalized before they can be averaged. Pulse-to-pulse normalization is achieved by using a dual-pulse (Reset and Trigger) generator; a ``Peak-Detect and Hold'' circuit; a Box-Car integrator, slightly modified to incorporate an electronic reset provision; and a high-precision, low-bandwidth analog divider. The system results in improved Time-Constant characteristics; can easily be used for short duration (nano-second range) pulsed lasers and for non-linear spectroscopic studies; and incorporates a provision for rejecting data from too-weak or too-strong pulses. A photoacoustic spectrometer incorporating this correction technique is described and system effectiveness is illustrated by presentation of the high-resolution, gas-phase, photoacoustic spectrum of Azulene $S_{1}$.