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Proceedings Paper

Loss characterization of high-index-contrast ridge waveguide oxide-confined InAlGaAs quantum well racetrack ring-resonator lasers
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Paper Abstract

The use of the non-selective, O2-enhanced wet thermal oxidation of deep-etched sidewalls in GaAs-based heterostructures has enabled the fabrication of low-loss, high-index-contrast ridge waveguides suitable for ring resonator laser devices. In a self-aligned process, the grown native oxide simultaneously provides excellent electrical insulation, passivation of the etch-exposed bipolar active region, and smoothing of etch roughness. The resulting strong lateral optical confinement at the semiconductor/oxide interface has enabled half-racetrack ring resonator (R3) lasers with bend radii r as small as 6 μm. In this work we have experimentally characterized the loss due to the mode mismatch at the straight to curved waveguide transition from analysis of efficiency data of half-R3 lasers with multiple cavity lengths. Using an 808 nm InAlGaAs graded-index separate confinement heterostructure, the transition losses are extracted from an inverse efficiency 1/ηd vs. length L plot for half-R3 lasers with r=150, 100, 50, 25 and 10 μm and 3 different ridge widths, w. The round trip transition loss ranges from 11.5 to 37.0 dB (for w=7.3 μm), 6.7 to 27.0 dB (w=4.2 μm), and 1.8 to 16.2 dB (w=2.1 μm) with decreasing radii, showing a clear decrease with width and corresponding improved mode overlap in the transition region. Simulation results elucidate the role of mode mismatch vs. radiative bend loss in high-index-contrast racetrack ring resonator lasers. We demonstrate a full-ring laser having a tangential stripe output coupler guide fabricated via e-beam lithography and non-selective oxidation with a threshold current density of 719 A/cm2 for an r=150 μm, w=6 μm ring.

Paper Details

Date Published: 3 February 2009
PDF: 12 pages
Proc. SPIE 7230, Novel In-Plane Semiconductor Lasers VIII, 72300J (3 February 2009); doi: 10.1117/12.807871
Show Author Affiliations
Jusong Wang, Univ. of Notre Dame (United States)
Wangqing Yuan, Univ. of Notre Dame (United States)
Christopher S. Seibert, Univ. of Notre Dame (United States)
Douglas C. Hall, Univ. of Notre Dame (United States)

Published in SPIE Proceedings Vol. 7230:
Novel In-Plane Semiconductor Lasers VIII
Alexey A. Belyanin; Peter M. Smowton, Editor(s)

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