textVertical-cavity surface-emitting lasers (VCSELs) have created new opportunities
in optoelectronics. However, VCSELs have so far been commercialized mainly for
operation at 0.85 µm, despite their potential importance at other wavelengths, such as 1.3
µm and 1.55 µm. The limitations at these longer wavelengths come from material
characteristics, such as a low contrast ratio in mirror materials, lower mirror reflectivity,
and smaller optical gain for longer wavelength materials versus AlGaAs/GaAs quantum
wells. A similar situation, insufficient gain relative to the cavity loss, existed in the past
for shorter wavelength VCSELs before high quality epitaxial mirrors were developed.
Semiconductor/air-gap Distributed Bragg Reflectors (DBRs) are attractive due to their
high index contrast, which leads to a high reflectivity, wide stop band and low optical
loss mirror with a small number of pairs. This concept is ready to be integrated into
material systems other than AlGaAs/GaAs, which is studied in this work. Therefore, the
impact of these DBRs can be extended into both visible and longer infrared wavelengths
as a solution to the trade-off between DBR and active region materials. Air-gap DBRs
can also be used as basic building blocks of micro-opto-electro-mechanical systems
(MOEMS). The high Q microcavity formed by the air-gap DBRs also provide a good
platform for microcavity physics study.
Air-gap DBRs are modeled using the transmission matrix formulae of the Maxwell
equations. A comparison to existing DBR technology shows the great advantage and
potential that the air-gap DBR possesses. Two types of air-gap are proposed and
developed. The first one includes multiple GaAs/air pairs while the second one combines
a single air-gap with metal and dielectric mirrors. New device structures and processing
designs, especially an all-epitaxial lateral current and optical confinement technique, are
carried out to incorporate air-gap DBRs into VCSEL structures. The first VCSEL based
on a GaAs/air-gap DBR is successfully demonstrated. Low threshold continuous-wave
lasing is achieved at room temperature. The device characteristics and air-gap DBR loss
are analyzed based on experimental data.Electrical and Computer Engineerin