Bidirectional amplification with nonsaturable absorption and amplified spontaneous emission

A theory of bidirectional amplification is developed and applied to single-pass and double-pass laser amplifier configurations. The effects of nonsaturable absorption, longitudinal amplified spontaneous emission (ASE) gain saturation, and ASE line narrowing are included in a self-consistent formulation. An estimate of aperture scaling limitations due to transverse ASE is included. Laser performance is discussed for some conditions typical of large aperture, multikilojoule, rare gas halide (RGH) fusion amplifiers. This formulation permits tradeoff studies to be performed rapidly by altering variables spanning an eight-parameter space.