Electrically Injected GaN-Based Vertical-Cavity Surface-Emitting Lasers with TiO2 High-Index-Contrast Grating Reflectors
Journal article, 2020

We demonstrate the first electrically injected GaN-based vertical-cavity surface-emitting lasers (VCSELs) with a TiO2 high-index-contrast grating (HCG) as the top mirror. Replacing the top distributed Bragg reflector (DBR) with an HCG offers substantial thickness reduction, polarization-pinning, and setting of the resonance wavelength by the grating parameters. Conventional HCGs are usually suspended in the low refractive index material, such as air, in order to create the largest refractive index contrast. However, the mechanical stability of such structures can be questioned and creating free-hanging GaN-membrane on top of GaN is problematic. We have therefore fabricated TiO2-HCGs resting directly on GaN without an air-gap. No DBR layers are used below the HCG to boost the reflectivity. A VCSEL with an aperture diameter of 10 μm shows a threshold current of 25 mA under pulsed operation at room temperature. The lasing modes locate around 400 nm and are transversely electrically -polarized with a line width of 0.5 nm. The full-width half-maximum beam divergence is 10°. This demonstration of a TiO2-HCG VCSEL offers a new route to achieve polarization pinning and could also allow additional benefits such as postgrowth setting of the resonance wavelength.

TiO 2

polarization selectivity

vertical-cavity surface-emitting laser



electrically driven device


high-index-contrast grating



Tsu Chi Chang

National Chiao Tung University

Seyed Ehsan Hashemi

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Kuo Bin Hong

National Chiao Tung University

Jörgen Bengtsson

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Johan Gustavsson

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Åsa Haglund

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Tien Chang Lu

National Chiao Tung University

ACS Photonics

2330-4022 (eISSN)

Vol. 7 4 861-866

Subject Categories

Atom and Molecular Physics and Optics

Other Physics Topics

Condensed Matter Physics



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