Design and fabrication of vertical external cavity surface-emitting lasers

Ragunathan, Gautham

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Description

Title

Design and fabrication of vertical external cavity surface-emitting lasers

Author(s)

Ragunathan, Gautham

Issue Date

2014-09-16

Director of Research (if dissertation) or Advisor (if thesis)

Choquette, Kent D.

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Lasers
• Vertical-Cavity Surface-Emitting Lasers (VCSEL)
• Photonics
• Fabrication
• Characterization
• Design

Abstract

This thesis examines the design and fabrication of a high output power, surface-emitting laser, known as a vertical external cavity surface-emitting laser (VECSEL). A VECSEL utilizes a free space cavity along with larger transverse cavity dimensions, to extract higher output power. To aid the design of the VECSEL, the thesis begins with fabrication and experimental characterization of vertical-cavity surface-emitting lasers (VCSELs). After the structure and operation of a VCSEL is overviewed, the fabrication of an oxide-confined VCSEL will be detailed. The VCSEL wafers’ epitaxial structures have a variation in their doping concentration profile in the p-type distributed Bragg reflector mirrors, to examine the tradeoff in their electrical and optical properties. This tradeoff is integral to both the VCSEL and VECSEL designs. A simulation of the VCSEL devices is performed and compared to experimental characterization. Based on these results, VECSEL devices are then designed for fabrication. Two sets of VECSEL structures are overviewed: one set is designed for optical pumping and one set is designed for electrical injection. The fabrication process for the optically pumped lasers is described and the devices are then characterized. Optically pumped VECSELs demonstrate lasing action and show similar trends with regard to the simulated doping concentration. Next, a design of a mask layout for electrically pumped VECSELs, composed of a top metal, a mesa layer to provide current isolation, and an implant aperture, is overviewed. Electrically injected VECSELs are fabricated through the use of ion implantation, backside infrared alignment, chemical mechanical polishing, bonding to Cu substrates for use as a heatsink, and wet etching for electrical isolation. Free space cavity design and characterization methodology for the VECSELs are described. While lasing action of electrically injected VECSELs is not observed, future modifications to design and processing are suggested.

Graduation Semester

2014-08

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http://hdl.handle.net/2142/50518

Copyright and License Information

Copyright 2014 Gautham Ragunathan

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