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Estimation of conditions for manifestation of bistability in the resonance curves of the transmission of a layer of active atoms with inhomogeneous broadening has been made. It is shown that hysteresis in the frequency dependence of such a layer is possible only under the conditions of the Stark shift of the resonant transition levels.Keywords: frequency optical bistability, self-modulation broadening of a spectral line. Introduction.Investigation of the processes of formation of a resonant circuit of absorption of a layer of active atoms may be of interest for elucidating the conditions for observing bistable transmission properties [1][2][3][4]. The bistability or hysteresis property in optical systems excited by laser radiation is easily exhibited upon change in the excitation amplitude [5]. The study of the conditions of the frequency bistability of optical systems, including planar structures of reduced dimensionality, is worth applying when creating up-to-date devices for transmission, storing, and processing of information.Formulation of the Problem and Description of the Approach. We have carried out calculation of resonance curves of a nonlinear-absorption medium, which is represented by an ensemble of active atoms. The main task is to determine the role of the inhomogeneous broadening (of the Gaussian-form spread in the basic frequencies ω 0 of active particles about the line center Ω) in formation of the spectral dependence of absorption at a high level of saturation. Here, allowance for the Stark shift of the levels of the basic transition in an intense light field is also a matter of principle.We considered the case where a monochromatic signal was incident on an active-medium layer filling a cavity. The external signal corresponds to a plane light wave with carrier frequency ω and amplitude E i (t), which is normal to the layer surface and which relatively slowly changes in a time comparable with the period 2π/ω. Interaction of the light wave with the medium of the layer can be described on the basis of the semiclassical approach represented by the Maxwell-Bloch model that enables one to investigate the dynamic behavior of resonant systems under the conditions of exposure to optical fields. Such a system of the equations in the form presented in [3] is used to formulate the relationship given below. In this work, the expression for the polarization response of the medium is modified, first, with allowance for the generalized two-level scheme (similarly, for example, to [6]). Its use permits one to consider, in a certain approximation [7], the role of the self-modulation line broadening due to the Stark effect. Second, inhomogeneous broadening was taken into account in a traditional form, wherein single atoms are characterized by homogeneously broadened lines, which are narrower than the total spectral lines of the whole collection of atoms. Such narrow lines, each corresponding to an individual group of atoms with the same transition frequency ω 0 , are called the spin packets. The expression used f...

The conditions for realization of the regime of self-oscillations of the intensity of a continuously pumped solid-state laser have been qualitatively analyzed using a system of kinetic equations. It has been established that, in the case where a thin semiconductor layer absorbing light at frequencies close to the lasing frequency is placed into the cavity of such a laser, self-oscillations of its radiation intensity arise as a result of the amplitude-phase self-modulation of the laser light field.Keywords: relaxation dynamics of lasers, intracavity self-modulation of radiation, self-modulation broadening of the amplification line.Introduction. Lasers emitting a continuous sequence of short pulses are used in metrology and modern apparatus for transmission of information. Generation of stable trains of contrasting subpicosecond-and picosecond light pulses calls for top laser technologies. Currently, planar semiconductor structures have come into use as passive Q switches in solid-state lasers generating ultrashort pulses in the regime of mode locking [1][2][3]. It is also known [4] that certain solid-state lasers can generate a regular sequence of fairly short pulses on excitation of relaxation oscillations in them at a fairly low external modulation of the pumping level or the cavity Q factor [5]. The physical processes occurring in the cavities of cw solid-state lasers emitting ultrashort pulses were investigated in [6, 7] on the basis of simulation and comprehensive analysis of the operation of saturable Q switches based on semiconductor structures.Formulation of the Problem. The aim of the present work is to determine the range of parameters of a solid-state laser with a thin-film passive Q switch at which in it there arise self-oscillations of its light intensity. Such a laser begins to operate in the regime of intracavity self-Q-switching on excitation of relaxation oscillations in it as a result of the change in the effective transmission of its Q switch caused by the change in the radiation intensity. However, the transmission of a semiconductor Q switch can change not only as a result of the saturated absorption of light in its material, but also due to the high criticality of the very thin layer of this material to the variations in the frequency of oscillations in the cavity. Such variations in the frequency of oscillations can arise in active media characterized by a complex structure of amplification. In the case of a complex profile of the amplification band, even the detuning of the maximum lasing frequency from the fundamental frequency of the active transition can be nonzero. It has been established in [8,9] that the refractive index of semiconductors and activated crystals changes resonantly depending on the magnitude and sign of such a detuning. Under these conditions, the dynamics of laser radiation depends on the self-modulation broadening of the amplification line and on the relation between the amplitude and phase of the radiation pulses. In [10], it was established that self-modulation chan...

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