Intensity Fluctuation Correlations in Amplified Spontaneous Emission From a Cw-Excited High Gain Laser Amplifier
ASE sources, such as long, thin gas laser amplifiers whose only input is the distributed spontaneous emission from the excited atoms, emit radiation that shows a high degree of directionality and coherence. The intensity of the spontaneously emitted field in any mode, however, displays rapid and significant fluctuations about the average intensity due to interference effects between the emissions from the incoherently excited sources. Due to competition between different modes for the finite amount of energy stored by the excited medium, fluctuations are expected to persist in the output of an ASE source, even under conditions of heavy gain saturation [1–4]. In particular, due to this coupling of the different fields to the same atomic population, one observes significant anti-correlations between orthogonally polarized components of the emitted field for gain saturated ASE sources [3–5,13]. We have experimentally correlated the intensity fluctuations for the orthogonally polarized components of the output from one end of a high-gain, CW excited, 3.51 μm Xe-He laser amplifier for various values of the small signal gain of the medium and for different degrees of homogeneous broadening.
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