Natural laser-beam spatial coherence determined by spontaneous emission
Arakelyan S.M., Akhmanov S.A., Tunkin V.G., Chirkin A.S.
A high degree of spatial coherence was obtained in a single-mode He-Ne gas laser; the deviations of the normalized correlation function at the center of the beam from unity do not exceed several times 10"'. It is shown that what actually occurs is a limiting "natural" spatial coherence determined by the spontaneous noise. The experimental data are interpreted using two models of the spatial statistics of the laser radiation: the "signal-plus-noise" model and the model of an oscillation that undergoes amplitude and phase fluctuation. A laser with a high spatial coherence can greatly extend the possibilities of investigating the scattering of light at small angles.
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![](/ps/1779/article_27088_800_head.png "<b>A high degree of spatial coherence was obtained in a single-mode He-Ne gas laser; the deviations of the normalized correlation function at the center of the beam from unity do not exceed several times 10"'. It is shown that what actually occurs is a limiting "natural" spatial coherence determined by the spontaneous noise. The experimental data are interpreted using two models of the spatial statistics of the laser radiation: the "signal-plus-noise" model and the model of an oscillation that undergoes amplitude and phase fluctuation. A laser with a high spatial coherence can greatly extend the possibilities of investigating the scattering of light at small angles.</b>")