Fabrication and performance of broad-area high power narrow linewidth semiconductor laser diodes

This thesis presents the theoretical and experimental examination of broad-area, high-order, distributed feedback (DFB) grating, semiconductor laser diodes for the goal of manufacturably attaining longitudinal mode reduction. Through coupled-mode theory, the coupling coefficient, the reflectivity, and the laser emission linewidth resulting from a refractive index grating are predicted. A comparison is made between lasers with coated and uncoated facets, demonstrating that the impact of DFB gratings is enhanced by facet coating. Both surface-etched and epitaxially buried DFB grating lasers emitting at 15xx nm using designs with varying grating order and fill factor, are fabricated at the Holonyak Micro and Nanotechnology Laboratory cleanroom using standard i-line optical lithography. Alternative lithography techniques are proposed without reliance on small feature definitions by electron-beam lithography. The buried grating lasers are characterized in terms of threshold current, emission wavelength, and spectral linewidth. Under pulsed operation, the threshold currents of lasers diodes 30 μm wide and 2 mm cavity length are found to moderately increase using the DFB gratings. The spectral linewidths measured for buried grating lasers are less than control lasers (lacking gratings), demonstrating a reduction of longitudinal modes with high-order gratings, compatible with optical lithography. The most successful grating designs have 50% fill factor and the measured emission linewidths are consistent with theoretical estimates. This work has demonstrated 1.5 µm laser diodes with spectral narrowing arising from longitudinal mode reduction via DFB gratings, fabricated using designs and techniques amenable with high volume production. While the grating designs demonstrated in this work have not been optimized with respect to optical loss, high-order gratings appear promising for future high-power laser applications.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2021

Author dc:creator

• Lakomy, Katherine Anne

Contributors dc:contributor

• Choquette, Kent D
• Eden, J. Gary
• Dallesasse, John
• Lee, Minjoo Lawrence

• semiconductor lasers
• linewidth
• high power
• InP

Statement dc:rights

• Copyright 2021 Katherine Anne Lakomy

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/110415

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/110415