Virtual open path diode laser spectrometer

摘要

A virtual, open-path diode laser spectrometer is implemented for use in design and modeling of openpath diode laser spectrometers. The virtual spectrometer is composed of eight modules: a diode laser source module, optical beam correction module, sample module, detection optics module, detector module, signal processing module, data handling module and display module. This modular approach increases the ease of modifying and updating the spectrometer. The virtual spectrometer allows for easy adjustment and visualization of parameters associated with real spectrometers of this design. The virtual spectrometer will be used to model behavior of a distributed, open-path, near-infrared diode laser spectrometer to be mounted on micro rover robots. The purpose of the spectrometer is to measure trace gas levels in hazardous or inaccessible places, such as the surface of Mars for water vapor or around chemical spills, in mines, or for use in covert operations in hostile areas. The virtual spectrometer will also be used to model behavior of an open-path, near-infrared diode laser for measuring chemical species produced in the exhaust plumes of hybrid rockets. Comparisons between actual and virtual spectra are made and discussed. * Graduate Student, Student Member AIAA f Undergraduate Student, Student Member AIAA | Professor, Associate Member AIAA § Professor, Associate Member AIAA Copyright © 2000 by Edmond W. Wilson, Jr. Published by the American Institute of Aeronautics, Inc. with permission. Introduction Until recently, the near infrared region of the electromagnetic spectrum, from approximately 0.7(J,m to 2 Jim, has been overlooked by spectroscopists. However, the rapid and extensive development of near infrared semiconductor diode lasers, driven by their use in fiber optic communications, compact disk audio players and laser printers, has led to a resurgence of interest in this spectral range. It is now possible to obtain diode lasers that operate at a variety of wavelengths in the near infrared portion of the spectrum. Diode lasers are being manufactured that have very attractive properties as sources for spectroscopic studies. They have the positive characteristics of lasers in general, i.e., the production of intense beams of nearly monochromatic radiation with low divergence. In addition, they are tunable over small wavelength ranges by varying their temperature or injection current. And they are quite small, with modest power requirements, making them ideal as probes in field applications or for space missions. Negative properties of diode lasers must be overcome to employ them successfully in spectroscopic applications. Particularly troublesome is the phenomenon called mode hoping. Instead of a linear