Abstract

To the contrary to well-known superradiance problem, we analyse collective spontaneous generation of nonpropagating, nonradiating fields, both transverse and longitudinal. In spite of the resonance with two-level transition ω₀, they have long wavelengths as compared with the vacuum value 2πc/ω₀ because of specific dielectric dispertion of an active medium. The corresponding polarization waves cannot escape a sample effectively, as usual electromagnetic waves do. This is the reason for the self-excitation of a quasihomogeneous HF electric field in an active sample even without resonator. Such a field is created by HF dipole oscillators, e.g. molecular or electron-hole ones, and display spontaneous growth, like superradiance, if oscillators are prepared by pump in an unstable, inverted state and their density is high enough.^[1]

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