Radiation amplification in free-bound transitions through incoherent multiphoton pumping and stimulated recombination

Abstract

We present a theoretical analysis of radiation amplification in free-bound transitions through incoherent multiphoton pumping and stimulated recombination. A model of Laser Induced Continuum Structure (LICS) cast in terms of the fully time-dependent density matrix, incorporating an incoherent multiphoton pumping mechanism, is found to exhibit amplification without population inversion. For sufficiently high laser intensities the stimulated recombination process is shown to create inversion and an enhancement of the gain coefficient is achieved as well as a shift in the wavelength range in which amplification occurs. A quantitative discussion of a real system (Cs) is presented and the conditions favourable for amplification are examined in detail.