Optical Gain Measurement Through A Medium With Both Temporal And Spatial Refractive Index Variations

Sandor Holly

doi:10.1117/12.953837

1 March 1974 Optical Gain Measurement Through A Medium With Both Temporal And Spatial Refractive Index Variations

Sandor Holly

Proceedings Volume 0041, Developments in Laser Technology II; (1974) https://doi.org/10.1117/12.953837
Event: Annual Technical Symposium, 1973, San Diego, United States

Abstract

Recent advances in high power lasers with their optically active media at supersonic flow conditions require experimental gain measurements to be performed under difficult conditions. The spatial inhomogeneities and their rapid temporal variations cannot be prescribed analytically; their effect on the accuracy of measured gain values can only be estimated. In the cases of media with low gain values (typically in the order of 0.1 to 1.0 percent per cm) inaccuracies resulting from time varying optical inhomogeneities may completely mask the data when conventional gain measuring techniques are used. The present paper describes a method that was developed at Atlantic Research Corporation with IR&D funds to eliminate the problem as described above. The system has several unique features: 1. By appropriate design of the optical train, the influence of rapid variations of inhomogeneities of the optically active medium on roundtrip gain measurements are effectively eliminated. This feature is maintained throughout a wide range of inhomogeneities such as is experienced in well-designed gas dynamic and chemical lasers. 2. A single detector sequentially monitors a ref-erence level, the signal itself, and an off condition. High frequency noise components of the probe laser are eliminated by a synchronous detector with variable RC constant; the low frequency noise components are elimi-nated by ratio taking. 3. A unique optical arrangement allows complete elimination of laser radiation feedback into the probe laser allowing quiet laser operation. The above system can be operated in any portion of the optical spectrum. It has been operating at Atlantic Research Corporation at 10 microns with a total resolution of roundtrip gain of better than 1 percent.

Citation Download Citation

Sandor Holly "Optical Gain Measurement Through A Medium With Both Temporal And Spatial Refractive Index Variations", Proc. SPIE 0041, Developments in Laser Technology II, (1 March 1974); https://doi.org/10.1117/12.953837

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Sensors

Laser beam diagnostics

Signal detection

Beam splitters

Mirrors

Germanium

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