Integrable semiconductor ring lasers and two-dimensional rectangular lattice distributed feedback lasers
Han, Haewook
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https://hdl.handle.net/2142/19089
Description
Title
Integrable semiconductor ring lasers and two-dimensional rectangular lattice distributed feedback lasers
Author(s)
Han, Haewook
Issue Date
1995
Doctoral Committee Chair(s)
Coleman, James J.
Department of Study
Electrical and Computer Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Physics, Condensed Matter
Physics, Optics
Language
eng
Abstract
Two types of integrable semiconductor lasers are investigated in this thesis. Semiconductor ring lasers with circular and square ring resonators are analyzed, and their fabrications and laser results are described. Two-dimensional rectangular lattice distributed feedback lasers are proposed and analyzed by a coupled mode theory.
Strained-layer InGaAs-AlGaAs-GaAs circular ring lasers with a single Y-junction output coupler are fabricated by SiCl$\sb4$ reactive ion etching. The bending loss calculated by a Wentzel-Kramers-Brilloin (WKB) analysis and the measured threshold currents suggest that the loss of the small radius lasers is mainly due to the nonradiative recombination and scattering at the deeply etched sidewall. A comparison between the estimated and measured longitudinal mode spacings indicates that the small radius ($<$76 $\mu$m) ring lasers operate in relatively low order whispering gallery modes.
Strained-layer InGaAs-AlGaAs-GaAs square ring lasers with total internal reflection (TIR) mirrors and narrow gap output couplers are described. The modal reflectivity of TIR mirrors is calculated by a plane wave expansion method. A new fabrication technique requiring a single SiO$\sb2$ mask layer is developed. The square ring lasers operate in a single longitudinal mode with a side mode suppression ratio of $\sim$20 dB. An asymmetry in the emission spectra indicates the traveling wave operation of the square ring lasers. A new self-aligned etch process is developed for TIR mirrors without additional lift-off and dielectric depositions, and is demonstrated to produce high quality TIR mirrors with a reflectivity of $\sim$0.93.
Two-dimensional rectangular lattice distributed feedback lasers are described by a coupled-mode analysis of the scalar wave equation derived from a TE vector field. Threshold conditions are presented with the optimum design conditions for minimum threshold gains. For a given area and periods of the grating, there is an optimum structural angle of the grating. If the normal incidence coupling constants of the two orthogonal gratings are the same, the optimum structural angle should be the same as the incidence angle which is determined by the Bragg condition. For the different normal incidence coupling constants, the optimum structural angles are obtained numerically.
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