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

Abstract

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.

Fabrication of Porous Anodic Alumina (PAA) by High-Temperature Pulse-Anodization: Tuning the Optical Characteristics of PAA-Based DBR in the NIR-MIR Region

“…As a consequence of constructive interference of the multiple reflections, DBR demonstrates high reflectance (or low transmittance) of light in a given part of the spectrum, which is called photonic stopband (PSB). DBRs are frequently used in LEDs [ 1 , 2 ], solar cells [ 3 , 4 ], or vertical-cavity surface-emitting lasers [ 5 , 6 ] as important optical components that enhance luminous or light trapping efficacy. Conventional DBRs are made of two different materials that require careful consideration of their optical and mechanical properties, as well as when choosing a reliable/reproducible method to grow the anticipated structure.…”

Design of GaN-Based PCSEL With Temperature-Insensitive Lasing Wavelength

“…The fabrication of freestanding structure on GaN-silicon platform is a mature technology which has been widely reported in LED radiation pattern [28], [29] and enhance light extraction [30], [31]. TiO2 micro-nano structure etching is compatible with GaN, it has been used as high contrast grating reflector in GaN-VCSELs [32]. After PhC fabrication and photoresist protection, the backside lithography aligned with the top PhC layer, is performed to guarantee the freestanding configuration.…”

Design and simulation of vertical cavity surface emitting laser based on all-inorganic perovskite

“…DFB lasing is more difficult to generate and requires a higher threshold current. While the VCSEL structure consisting of two layers of DBR has the advantages of small divergence angle, low threshold current, single longitudinal mode operation, high-speed modulation, etc [14][15][16][17][18] . VCSEL has been widely used in optical communication, optical storage, laser display, laser sensing and other fields [19][20][21][22][23] .…”