Image courtesy of Sandia National Laboratories
Array of gallium nitride (GaN) nanowires fabricated by Sandia-developed top-down method. Right: Single GaN nanowire (top), sub-threshold UV emission from nanowire (middle), above-threshold UV lasing from nanowire end facets (bottom).
Single-frequency rather than the more typically-observed multiple-frequency laser output is induced in gallium nitride (GaN) nanowires by precisely controlling the geometry of the nanowire.
Single-frequency nanowire lasers based on gallium nitride (GaN) could enable ultracompact, low-power, and low-noise coherent light sources for a variety of applications including optoelectronic circuits and microdevices, and information storage, with reduced cost and improved function.
Gallium nitride (GaN) based nanowire lasers have potential to become ultra-compact, low-power, coherent ultraviolet and visible light sources, allowing these lasers to serve in a variety of applications including writing information at high densities onto microscale media storage devices. Yet, poor optical beam and spectral properties have hampered uses of these lasers. Many potential applications require operation of the laser at a single frequency, with low noise and an optimal spatial profile. GaN lasers, however, typically produce multiple frequencies simultaneously, meaning the laser emits light in multiple, tightly-spaced, wavelengths that often travel in different directions or spatial patterns and result in beam spread and poor focusing properties. Now, researchers at Sandia National Laboratories’ Solid-State Lighting Science EFRC achieved single-frequency laser output from GaN nanowires using a new method to fabricate high quality arrays of GaN nanowires with precisely controlled geometries. The top-down fabrication technique starts from a silicon-doped GaN layer, followed by tunable dry etch plus anisotropic wet etch for precise control of the nanowire dimensions. The researchers discovered several approaches to convert multiple-frequency nanowire lasers into single-frequency lasers by controlling nanowire size, producing a coupled nanowire cavity, or by placing the nanowires onto a gold substrate.
George T. Wang
Sandia National Laboratories
Michael E. Coltrin
Director, Solid-State Lighting Science (SSLS) EFRC
DOE Office of Science, Basic Energy Sciences program, Energy Frontier Research Centers (EFRC) program.
Li, Q., J. B. Wright, W. W. Chow, T. S. Luk, I. Brener, L. F. Lester, G. T. Wang, “Single-mode GaN nanowire lasers,” Optics Express, 20, 17873 (2012). [DOI: 10.1364/OE.20.017873]
Xu, H., J. B. Wright, L. Ting-Shan, J. J. Figiel, K. Cross, L. F. Lester, G. Balakrishnan, G. T. Wang, I. Brener, L. Qiming, "Single-mode lasing of GaN nanowire-pairs," Appl. Phys. Lett., 101, 113106 (2012) [DOI: 10.1063/1.4751862]
Xu, H., J. B. Wright, A. Hurtado, Q. Li, T-S. Luk, J. J. Figiel, K. Cross, G. Balakrishnan, L. F. Lester, I. Brener, G.T. Wang, "Gold substrate-induced single-mode lasing of GaN nanowires," 2012. Appl. Phys. Lett., 101, 113106 (2012) [DOI: 10.1063/1.4768300]
Solid-State Lighting Science EFRC