Surface-emitting circular DFB, disk-, and ring-Bragg resonator lasers with chirped gratings II: nonuniform pumping and far-field patterns

Xiankai Sun,Amnon Yariv

doi:10.1364/oe.17.000001

Abstract

This is a continuation of our previous work [Opt. Express 16, 9155 (2008)]. In this paper we investigate the effect of nonuniform pumping on the modal properties of surface-emitting chirped circular grating lasers. By numerically solving the coupled-mode equations and matching the boundaries we compare and discuss the threshold pump levels and frequency detuning factors for three pumping profiles: uniform, Gaussian, and annular. Depending on the overlap of the pumping and modal profiles, Gaussian pumping results in the lowest threshold pump levels except for the fundamental mode of ring Bragg resonator laser, and annular pumping provides larger threshold discrimination between the fundamental and first-order modes of circular DFB and ring Bragg resonator lasers, which is favorable for single-mode operation in these lasers. We also study the far-field patterns of the fundamental modes of circular DFB, disk-, and ring- Bragg resonator lasers. Circular DFB and ring Bragg resonator lasers have the first-order dominating peak, while disk Bragg resonator laser exhibits the zeroth-order dominating peak.

Highlights

Circular grating coupled surface emitting lasers are able to produce circularly-symmetric, large-emission-aperture, narrow-divergence laser beams, which makes them excellent light emitters with efficient coupling to optical fibers and superior elements for on-chip 2D laser array integration for coherent beam combination
Annular pumping provides larger threshold discrimination between the fundamental (Mode 1) and first-order (Mode 2) modes of circular DFB and ring Bragg resonator lasers, which is favorable for single-mode operation in these lasers; 4
Disk Bragg resonator laser still possesses the lowest threshold pump levels among the three types of circular grating lasers [3], while more impressively, Gaussian pumping for this type of laser is much more effective in reducing the threshold pump levels, making them ~3 times lower than those by uniform and annular pumpings

Summary

Introduction

Circular grating coupled surface emitting lasers are able to produce circularly-symmetric, large-emission-aperture, narrow-divergence laser beams, which makes them excellent light emitters with efficient coupling to optical fibers and superior elements for on-chip 2D laser array integration for coherent beam combination. The inner grating extends from the center to xL while the outer from xR to xb In these lasers, the gratings serve two purposes − providing feedback for the in-plane fields to form a radial resonator, and coupling the vertical laser radiation out of the plane as an output coupler. In this paper by solving the coupled-mode equations and matching boundaries in a numerical way we present a comprehensive study of the nonuniform pumping, especially the effects on the threshold pump levels and frequency detuning factors, for those three types of circular grating lasers. Their far-field patterns will be calculated, compared, and discussed, which is followed by the conclusions.

Nonuniform pumping

Far-field patterns

Conclusions