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The influence of nonlinear optical interaction in a semiconductor dual-wavelength vertical-external-cavity surface-emitting laser on the main parameters of dual-wavelength radiation and lasing in the long-wavelength part of the mid-IR range, obtained in this laser as a result of nonlinear wave mixing, is investigated. An increase in the pump power leads to saturation of the short-wavelength lasing intensity and to a more rapid rise in the long-wavelength lasing intensity in comparison with the linear increase in lasing intensity in these regions in the absence of nonlinear interaction. Under the conditions of nonlinear interaction, the carrier concentration in the active layers is not stabilised near the lasing threshold but changes with an increase in the pump intensity and provides the corresponding gain in the laser active region, thus maintaining steadystate lasing. Some ways for modifying the laser active region in order to obtain the most efficient lasing in the mid-IR range are proposed.

The parameters of middle-IR radiation (λ ∼ 17 μm) generated as a result of the intracavity nonlinear optical interaction in a semiconductor dual-wavelength vertical-external-cavity surface emitting laser operating in a pulsed regime have been numerically analyzed. The dependence of the peak output radiation power on the length of the nonlinear crystal has been studied for various values of the loss factor.

A mathematical model of a dual-wavelength vertical-external-cavity surface-emitting laser (VECSEL) is formulated with the distribution of optical pumping and generated fields over the beam cross sections taken into account. Dynamic regimes are mapped using the 'pump power — cavity round-trip time' plane. The map comprises regions of cw generation, periodic oscillation, quasiperiodic and chaotic oscillations of the radiation intensity and the carrier density in the active regions of the laser. It is shown that when the reflection coefficient of the external cavity is increased, the regions of complex dynamics in the maps become narrower. Using numerical methods the spatio-temporal dynamics of a dualwavelength VECSEL is analysed in the regime of quasi-periodic oscillations.

The stability of the stationary state and periodic oscillations of the radiation intensity of the dual-wavelength vertical external cavity surface-emitting laser is analyzed. It is demonstrated that the stationary state is always stable for the laser with independent active areas that contain quantum dots of different depths. A map of dynamic regimes with the values of parameters that correspond to the cw lasing, periodic oscillations of intensity, and complicated dynamics (quasi-periodic or chaotic regimes) is constructed for the laser with coupled active areas. The dynamics of the laser radiation in the quasi-periodic regime is numerically simulated. It is demonstrated that relatively slow variations in the amplitude with characteristic times of several or several tens of microseconds are typical of the short laser pulses that are formed at time intervals of tens of picoseconds. The period of the pulse train is approximately equal to the round-trip time of the external laser cavity.

The steady-state stability of a dual-wavelength vertical-external-cavity surface-emitting laser has been analyzed. It is shown that, in the laser with independent active regions containing quantum wells (QWs) of different depths, this state is always stable. The increment of growth and the frequency of oscillations of small deviations from the steady state are determined in the presence of coupling between the active regions, which is caused by the absorption of short-wavelength radiation in deep QWs. In the region of violation of the steady-state stability, the generation proceeds in the form of short pulses, with the almost simultaneous excitation of the optical fields at both frequencies.

The effect of pump wave reflections on the carrier generation rate and uniformity of carrier population in quantum wells (QWs) of a dual-wavelength vertical-cavity surface-emitting laser has been numerically analyzed. The laser’s active region has been described within a mathematical model allowing any number of QWs and arbitrary distribution of carrier generation rate. It is shown that the optimal arrangement of blocking layers in the active region of a dual-wavelength vertical-cavity surface-emitting laser allows one to obtain a very uniform QW population. It is established that pump wave reflections significantly affect the local carrier generation rate and, therefore, the distribution of excited carriers in the laser structure.

A nonlinear-optical conversion process in a dual-wavelength vertical-external-cavity surface-emitting laser that leads to the generation of difference-frequency radiation in the long-wavelength part of the mid-infrared range (∼17.7 μm) is analyzed numerically. The nonlinear crystal of GaAs is incorporated in the output-coupler mirror and, at the same time, is placed in a Fabry-Perot cavity tuned to the difference frequency. It is shown that the dependence of the nonlinear-conversion efficiency on the GaAs crystal thickness exhibits a pronounced resonance behavior and that the peak power of the radiation in the mid-infrared range can be as high as a few milliwatts with the parameters of the laser and the optical pump readily attainable experimentally.

The structure of the Bragg reflectors in a vertical-cavity laser in which three-wave nonlinear mixing is used to generate the emission in the mid-infrared spectral region is optimized. It is shown that the reflection band of the Bragg reflectors can be broadened appreciably in comparison with conventional quarter-wavelength reflectors formed of the same pair of materials. Using this approach, it becomes possible to produce a laser with nonlinear frequency conversion based on the lattice-related nonlinearity in a GaAs/AlGaAs system; this laser emits in the region of

A method for controlling the polarization characteristics of the radiation of a dual-wavelength vertical external cavity surface-emitting laser (VECSEL) is proposed. It is shown that a retarder of a special kind used as a part of the laser cavity allows the excitation of laser radiation with components in nearly mutually transverse polarization planes.

Parameters of mid-infrared pulsed radiation (∼17.1 µm) being emitted due to intracavity nonlinear optical frequency conversion in the dual-wavelength vertical external-cavity surface-emitting laser are analyzed. Nonlinear optical frequency conversion is supposed to be realized in the quasi-phase-matched crystal. The dependence of peak pulse power at the wavelength corresponding to the mid-infrared range on the nonlinear crystal length at various values of a loss factor is obtained.

The mathematical model of a dual-wavelength emission from a vertical external cavity surface-emitting laser taking into account the transverse distribution both of optical fields and pump carrier flux density is built. Spatio-temporal dynamics of charge carriers and photons is analyzed. It is shown that the most pronounced optical hole-burning can be observed near the optical axis of the laser.

The map of dynamic regimes of a dual-wavelength vertical external cavity surface-emitting laser is built. The areas of continuous wave operation as well as of time-periodic, quasi-periodic and chaotic operation can be marked out in the map. A possible explanation of quite different laser behavior in those area is given.