Abstract

Between all the proposed schemes of laser without inversion, the double-Λ configuration, with two ground levels, |1>and |2>, both connected by dipole transitions to two different excited levels |3> and |4>, appears as the most promising one for application to short wavelength generation.^[1,3] We have investigated theoretically the nonlinear regime of amplification without inversion in double-Λ scheme, taking into account the nonlinearity connected to the saturation of the population difference n₃₄ between the upper levels., i.e. the quantity determining the amplification amplitude. Of course the nonlinearity connected with the ground-state low-frequency coherence, essential for the realization of amplification without inversion in that scheme is also taken into account. On the contrary the nonlinearities associated to the optical transitions take place at higher light intensities and are neglected in our analysis. Thus we generalize the treatment of ref.^[1] to a configuration of specific interest for future experiments.

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