Supermode Si/III-V Lasers and Circular Bragg Lasers

Citation

Sun, Xiankai (2010) Supermode Si/III-V Lasers and Circular Bragg Lasers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/6797-0136. https://resolver.caltech.edu/CaltechTHESIS:05072010-002329705

Abstract

Semiconductor lasers are arguably the most important component in optical communications. This thesis investigates two types of semiconductor lasers that are useful in integrated optics. Part I focuses on supermode Si/III–V lasers and Part II discusses circular Bragg lasers for the application as surface-emitting lasers.

Just as optical fibers have largely replaced the traditional copper wires in long-distance applications, people started to consider incorporating optical communication onto chips, primarily because the increased ohmic heating and RC delay associated with the metal interconnection prevent further increase in the data-processing rate. Si is well known to be the integration platform for electronics, and III–V materials (GaAs, InP, etc.) are efficient light emitters. It is natural to bring them together to realize the on-chip optical communication. Among various Si/III–V integration schemes the most promising is the hybrid Si evanescent platform in which a wafer-bonding technique that is compatible with current CMOS processing is used to bring Si and III–V materials together. Part I of this thesis focuses on the application of a novel mode-control method to such hybrid waveguide system to enhance the modal gain, which makes for more efficient and, most importantly, shorter devices that may hold the key to the photonics/electronics integration. The supermode theory is derived, the shortest adiabatic mode transformer is theoretically and numerically studied, and the device design and fabrication are presented, followed by the experimental demonstration of the performance enhancement in the mode-controlled Si/InGaAsP laser devices.

Vertical cavity surface emitting lasers are a commercial light source for optical communications, but their single-modedness and good emission pattern are guaranteed only over a very small mode area (diameter of several microns) thus they have limitations in high-power applications. As an alternative, circular Bragg lasers can be designed as a superior surface emitting laser that produces high output power with good beam quality. Part II of this thesis presents a comprehensive and systematic theoretical study on the surface-emitting Hankel-phased circular Bragg lasers in various geometries. The analytical and numerical mode-solving methods will be described, followed by near- and above-threshold modal analyses.

Thesis Files