The effect of induced light scattering due to absorption on the angular spectrum of laser emission in air

It is shown analytically that thermally induced light scattering due to absorption can cause a significant degradation of the laser radiation pattern in air. It is further shown that the negative effect of nonlinear processes on the divergence of laser emission can be sharply reduced and practically suppressed through lasing at many of the longitudinal modes and by selecting the lasing frequency. The analytical expression obtained can be readily generalized to the case where the initial divergence of laser emission exceeds the divergence due to diffraction.