High-Power GaN-Based Vertical-Cavity Surface-Emitting Lasers with AlInN/GaN Distributed Bragg Reflectors

Masaru Kuramoto,Komei Tazawa,Tetsuya Takeuchi,Tatsuma Saito,Takanobu Akagi,Kazufumi Tanaka,Seiichiro Kobayashi

doi:10.3390/app9030416

Abstract

High-efficiency and high-power operation have been demonstrated for blue GaN-based vertical-cavity surface-emitting lasers (VCSELs) with AlInN/GaN distributed Bragg reflectors. The high-efficiency performance was achieved by introducing a novel SiO2-buried lateral index guide and adjusting the front mirror reflectivity. Lateral optical confinement has been shown to greatly lower the otherwise significant loss of transverse radiation exhibited by typical VCSELs based on GaN. Employing a long (10λ) cavity can also enhance the output power, by lowering the thermal resistance of the VCSEL and increasing the operating current associated with thermal rollover. This modification, in conjunction with optimized front mirror reflectivity and a buried SiO2 lateral index guide, results in a blue VCSEL (in the continuous wave mode with an 8 μm aperture at 20 °C) having a superior differential quantum efficiency value of 31% and an enhanced 15.7 mW output power. This unit also exhibits a relatively high output power of 2.7 mW at temperatures as high as 110 °C. Finally, a 5.5 μm aperture VCSEL was found to generate a narrow divergence (5.1°) single-lobe far field pattern when operating at an output power of approximately 5 mW.

Highlights

GaN-based vertical-cavity surface-emitting lasers (VCSELs) are important in numerous applications, including adaptive laser headlamps [1,2,3], retinal scanning displays and visible light communication systems
Further improvements in GaN-based VCSELs are required for applications such as laser headlamps
The η d F value obtained from the frontEfficiency side mirror for a VCSEL can be expressed as: The ηdF value obtained from the front side mirrorαfor

Summary

Introduction

GaN-based vertical-cavity surface-emitting lasers (VCSELs) are important in numerous applications, including adaptive laser headlamps [1,2,3], retinal scanning displays and visible light communication systems. It is especially important to avoid COD in automotive headlamp laser diodes to ensure safety, and it is helpful if the lasing wavelength is not affected by temperature so that a stable beam color is obtained Based on these requirements, a combination of blue VCSELs and phosphors are the most attractive light source for next-generation laser headlamps. Our own group has recently reported an Improving the output power of such devices requiresF that the η d F value be increased. Our own group has recently reported an enhanced output power of 6 mW, as a result of increasing improvements in the thermal resistance of these units [21] in conjunction with CW operation, η d F [20].

Enhancement of Differential

Findings

High-Power andand