Within the coupled waves method complemented by quasi-optical approach, we investigate a possibility of diffraction mode selection with respect to the transverse mode index in lasers with planar Bragg resonators. Allowable values of the Fresnel parameter are determined which provide for establishment of stationary single-mode oscillation regime with narrow angle spectrum due to diffraction losses from the edges of the Bragg structure. We show that at larger values of the Fresnel parameter, oscillation stability can be improved by shifting the operating transition frequency to the eigenfrequency of the highest-Q longitudinal mode of the Bragg resonator.
We investigate the dynamics of heterolasers with finite-length planar Bragg structures. Based on the analysis of the dispersion equation describing the eigenwaves propagation in a Bragg structure, we present a physical interpretation of selection of modes with frequencies higher than the stopband. We demonstrate the improvement of stability by using the Bragg structures with transverse dimensions lower than the width of the active area of DFB heterolasers. As a result, the single-mode oscillation regime is sustained over a wider range of pump levels, and, correspondingly, of the output radiation power.
Using analytical approaches and CST Microwave Studio 3D simulations, we have undertaken a theoretical analysis of electrodynamical characteristics of 2D Bragg structures based on planar oversized dielectric waveguides with double-periodical corrugation. Such structures are of significant interest for obtaining directed narrow-band radiation in heterolasers with large dimensions of an active area. Modeling electrodynamical experiments on 'cold' testing of such structures in millimeter wavelength band were conducted. Fine agreement between the experimental results and the simulation results was demonstrated
which includes the presence of the highest-quality mode inside the Bragg reflection band in absence of the periodicity defects.
Using the coupled-wave method supplemented by the quasi-optical approximation, we study the dynamics of wide-aperture distributed-feedback (DFB) heterolasers with planar resonators having a step of corrugation phase. In configurations where the width of the Bragg structure is several times smaller or equal to the width of the active zone, the diffraction transverse losses provide mode selection with respect to the transverse index and, simultaneously, suppress the excitation of the longitudinal modes with frequencies above the bandgap. Stable single-mode operation of the DFB-heterolaser is possible in the wide range of positions and values of the corrugation phase step, which determine the level and ratio of the values of power radiated from the opposite ends of the DFB heterolaser. Conditions are found that ensure almost unidirectional output of radiation.
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