Mode control in vertical cavity surface emitting laser diodes
FacultiesFakultät für Ingenieurwissenschaften
LicenseStandard (Fassung vom 03.05.2003)
The control of the transverse modes in Vertical-Cavity Surface-Emitting Lasers (VCSELs) is of great importance for many applications in order to optimize characteristics such as optical power density, beam quality, and modulation speed. In this thesis, a comprehensive introduction to monolithic mode control methods and techniques in VCSELs is provided. Several approaches are introduced, compared to literature, and the underlying mechanisms are explained in an intuitive manner. The main mode control techniques realized experimentally are: 1) self-aligned shallow surface etching, 2) monolithically extended cavities, 3) photonic crystal structures. While the first two approaches have yielded international single-mode power records at the time, the third approach represents the first demonstration of incorporating photonic crystals monolithically into a full VCSEL structure. A strong emphasis is put on the manufacturability of all the approaches considered; a novel self-aligned process is introduced which allows to realize patterned VCSELs (e.g. by surface etching or photonic crystals) with only one additional lithography step and guarantees optimum alignment to the oxide aperture. The dependence of single-mode performance on various fabrication parameters and operating conditions is obtained by presenting a large number of experimental results. Novel effects observed in these devices are documented in detail (e.g. power-current hysteresis and diffraction in surface-etched devices and reduced thermal resistance and longitudinal mode switching in long cavity VCSELs). Complete mode control in VCSELs, however, also includes stabilizing the polarization of the emitted light. A first demonstration of combined mode and polarization control in a monolithic device is given in this thesis by elliptically surface-etched VCSELs. The polarization control is shown to be reproducible, current and temperature insensitive, and first modulation experiments at 10 Gbit/s are presented.
Subject HeadingsVCSEL-Laser [GND]
Data transmission [LCSH]
Semiconductor lasers [LCSH]