Abstract

A nonstationary theory has been developed of phase self-conjugation on the basis of four-wave mixing (FWM) induced in an absorbing medium placed in the cavity due to stimulated temperature scattering (STS) at orthogonal pumping. In the system under consideration the powerful pump wave E₀(k₀, ω₀) to be conjugated is directed onto the absorbing medium along the X-coordinate at right angle to the Z-axis of the cavity. At a pump power exceeding the threshold power in such a system counter-propagating waves E_±(_±k,_ω) of STS-radiation are generated, i. e. an STS-laser is realized which is investigated experimentally in Ref.¹. Since the STS-amplification coefficient depends on the angle of convergence of the interacting waves, in the orthogonal-pump system both generated waves have equal amplification coefficients are optimally matched to the corresponding thermal gratings having equal periods${\Lambda }_{+}\left({\text{E}}_{\text{0}}:{\text{E}}_{\text{+}}\right)={\Lambda }_{-}\left(\text{E}:{\text{E}}_{-}\right)\cong \sqrt{2}{\text{π/k}}_{\text{0}}$. In the system with longitudinal pump,^[1]the optimum amplification for each wave is realized in one of the directions of the round trip in the cavity due to the difference in the periods of the gratings Λ₊≫Λ_–). In the steady-state regime of operation, the system with longitudinal pump is much more effective (by about 10⁴times; the grating amplitudes$\sim {\Lambda }_{\pm }^2$) than the orthogonalpump system under consideration. However, in the nonstationary regime of generation when the grating amplitudes are practically independent of the grating periods and are comparable in value, the orthogonal system can be more effective than the system with longitudinal pump.^[1]

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