Top-down Cross-Section Controlled III-Nitride Nanowire Lasers

<p>III-nitride nanowire lasers have drawn significant attention as potential compact coherent light sources for a wide range of applications such as on-chip communication, optical sensing, and solid-state lighting. For practical applications, control over the lasing properties is needed. For example, a single mode lasing is beneficial for reducing the pulse broadening and the signal errors during the optical communications. An annular-shaped beam could be potentially used for the atom trapping or the stimulated emission depletion spectroscopy. The polarization-sensitive on-chip optical components also require linear polarization. However, due to the compact size of nanowire lasers and the cross-sectional symmetry of the traditional nanowire lasers, controlling the lasing properties still remains challenging. A top-down two-step etch process developed for vertical GaN nanowires offers the ability to precisely control the cross-section of the nanowire lasers. Consequently, the lasing properties can potentially be tailored by controlling the cross-section. In this dissertation, annular-shaped emission was demonstrated from GaN nanotube lasers with optical pumping at room temperature, consistent with finite-difference time-domain simulation results. Linearly polarized lasing emission was also realized from rectangular cross-sectioned GaN nanowire lasers. When the shorter y-dimension is ~120 nm, the rectangular cross-section creates a large contrast of the effective index of refraction, resulting in higher transverse confinement factors for the y-polarized modes than for the x-polarized modes. In order to pursue electrically injected single III-nitride nanowire lasers, non-polar InGaN/GaN multi-quantum-wells core-shell nanowires were fabricated by a combination of the top-down two-step etch process and a regrowth process. Lasing was observed from the core-shell nanowires by optical pumping at room temperature. A Hakki-Paoli measurement shows high modal gains of the non-polar core-shell nanowire lasers and the non-uniform gains resulting from the inhomogeneous regrowth. As a step towards electrical pumping, a Ti ohmic like' contact to the n-GaN core was fabricated. However, because of the lack of the ohmic contact to the p-GaN shell, the injection efficiency was extremely limited. As a result, instead of electrically-driven lasing, only weak spontaneous emission was observed in the electroluminescence measurement.'</p>

Name thesis:degree_name

Optical Science and Engineering

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Optical Science and Engineering

Year dc:date.available

2016

Author dc:creator

• Li, Changyi

Contributors dc:contributor

• Brueck, Steven
• Wang, George
• Feezell, Daniel
• Dawson, Ralph

• Other Engineering

Language dc:language

English

Identifier

https://digitalrepository.unm.edu/ose_etds/15

OAI identifier oai:identifier

oai:digitalrepository.unm.edu:ose_etds-1014