Transverse mode control in high-contrast grating VCSELs.

Marcin Gębski,Michał Wasiak,Maciej Dems,Z.J Xu,Y.Y Xie,Qi Jie Wang,Dao Hua Zhang,Tomasz Czyszanowski,Olga Kuzior

doi:10.1364/oe.22.020954

Abstract

This paper presents an extensive numerical analysis of a high-contrast grating VCSEL emitting at 0.98 μm. Using a three-dimensional, fully vectorial optical model, we investigate the influence of a non-uniform grating with a broad range of geometrical parameters on the modal behavior of the VCSEL. Properly designed and optimized, the high-contrast grating confines the fundamental mode selectively in all three dimensions and discriminates all higher order modes by expelling them from its central region. This mechanism makes single mode operation possible under a broad range of currents and could potentially enhance the single-mode output power of such devices. The high-contrast grating design proposed here is the only design for a VCSEL with three-dimensional, selective, optical confinement that requires relatively simple fabrication.

Highlights

Vertical-cavity surface-emitting lasers (VCSELs) serve as coherent optical sources and can be smoothly tuned by varying the current and temperature
VCSELs inherently emit in single longitudinal mode thanks to their very short cavities which are sandwiched between two distributed Bragg reflectors (DBR) and control the mode in the vertical direction
We aim to provide an extensive numerical analysis of high-contrast grating VCSEL, through the use of a three-dimensional fully vectorial optical model, to investigate the influence of a non-uniform grating with a broad range of geometrical parameters on the modal behavior of the VCSEL

Summary

Introduction

Vertical-cavity surface-emitting lasers (VCSELs) serve as coherent optical sources and can be smoothly tuned by varying the current and temperature. In shorter- and longerwavelength VCSELs, other methods of transverse mode confinement may be used which provide higher threshold currents but can require more expensive technology. Sub-wavelength high-contrast gratings (HCGs) offer new possibilities for three dimensional mode confinement through a single structure localized on top of the device. We aim to provide an extensive numerical analysis of high-contrast grating VCSEL, through the use of a three-dimensional fully vectorial optical model, to investigate the influence of a non-uniform grating with a broad range of geometrical parameters on the modal behavior of the VCSEL. It is found that properly optimized high-contrast grating makes single mode operation possible under a broad range of currents

Structure and numerical model

35 DBR pairs

Uniform HCG

Influence of the aperture

Findings

Conclusion