Investigation of lasing in the direction of a streamer channel in А2В6 semiconductors

An investigation was made of the generation of light in А₂В₆ semiconductors along a streamer channel. The establishment of a high gain amounting to (4–6)×10³ cm^–1 inside a channel resulted in lasing in resonators with mirrors formed by optical inhomogeneities of a crystal. The radiation emitted in the direction of the streamer emerged from the lasing region and propagated through the bulk of the crystal, whereas in the opposite direction it traveled along an optical waveguide formed by the streamer channel. The angular distribution of the radiation in the forward direction was influenced by the Franz–Keldysh effect at the head of the streamer and by distortions of the light wave in secondary streamer channels. A considerable increase in the radiation energy in the forward direction observed at streamer velocities of at least 4×10⁹ cm/sec was attributed to the attainment by the streamer head of a velocity higher than the group velocity of light at the wavelength of the emitted radiation.