Investigation of Operational Possibility of Laser Radiation in Partial Coherence Region

摘要

An on-line real time digital data acquisition system has been developed and used to study the higher order statistics of superradiant radiation. Measurements of the statistical moments through the 8th and power spectral measurements to 1.5 MHz are operational. A method of determining the natural and doppler linewidths from a plane parallel Fabry Perot interferometer has been extended to a confocal instrument. The confocal interferometer is shown to have certain advantages over the plane parallel instrument and a graphical method is presented for easy calculation of the pertinent quantities from the interferometer response curve. The above instrumentation has been used to measure the properties of superradiant radiation of the HeXe 3.5 micron line under both linear and saturated amplification. The variance, skew and excess of the intensity fluctuations with statistically reliable data have been measured. Measurements confirm the basic intensity squared dependence of the variance of linearly amplified spontaneous emission (superradiance). Under saturated conditions, however, the variance tends to increase more rapidly than for the linear case. The excess, representing the departure of the intensity fluctuations from the Gaussian, is shown to exhibit considerable structure. The tendency is for the excess to rise with additional amplification and then fall, eventually changing sign. (Author)