{'fraction_non_alphanumeric': 0.02037351443123939, 'fraction_numerical': 0.001697792869269949, 'mean_word_length': 5.775862068965517, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Electromagnetic waves in multilayer corrugated waveguides with space-modulated coupling coefficient: application to the design of single-frequency semiconductor lasers

The analysis of light propagation, diffraction and amplification in active multilayer corrugated waveguides with incorporated nonharmonic relief gratings, carried out by Rayleigh-Fourier formalism, is presented. On the base of this theoretical analysis the new possibilities of biharmonic grating for the design of single-frequency DFB lasers are discussed. The lasing characteristics of DFB heterolasers with biharmonic resonator are determined. It is shown that the biharmonic resonator with phase shift pi and space-modulated coupling coefficiency is capable of providing stable single-frequency oscillation at Bragg wavelength. The three-beam maskless holographic method for the fabrication of submicron biharmonic relief structures on the surface of n- AIIIBV semiconductors is developed. The biharmonic structure of period d equals 0.5 micrometer, possessing phase shift pi, is fabricated on n-InP in the process of laser-induced maskless wet photochemical etching under action of three Ar+ laser beams.