Realizing the full potential Inherent in optical heterodyne spectrometers requires the effective utilization of high-quality tunable local oscillators. One of the most attractive laser sources in the middle IR is the lead-salt tunable diode laser (TDL). Small size, simple operation, reasonable power, unrestricted wavelength access, and moderate support requirements all make for easy application of TDLs in heterodyne systems. Nevertheless, various attempts to develop optical heterodyne spectrometers with TDLs have yielded highly variable performance in demonstrated SNR. Much of the variability in system performance can be traced to the peculiarities of the TDL, particularly optical power instabilities (called excess noise) and multi-modedness.

© 1984 Optical Society of America

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