Optical and thermal dynamics of long wave quantum cascade lasers
Author
Gündoğdu, Sinan
Advisor
Gülseren, Oğuz
Date
2018-09Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Quantum Cascade Lasers (QCLs) are coherent light sources that make use of
intraband transitions of wavefunction engineered semiconductor quantum wells.
They have been designed to emit light in a wide spectral range; from mid-wave
infrared to terahertz. Long wave QCLs are a subject of interest for some applications
such as remote detection of harmful chemicals. These applications
demand higher optical powers at room temperature. In this thesis we demonstrate
simulation, design, fabrication and characterization of long-wave QCLs
that emit light around 9.2 m. To increase optical power and enhance thermal
performance, we explore the optical and thermal properties of QCLs. Thermal
characteristics of QCLs are analyzed by nite element methods. We developed a
spectral technique that relies on analysis of Fabry-Perot modes to measure cavity
temperatures experimentally. By combining the simulations and experimental
results we scrutinized the thermal properties of QCLs, and estimated the active
region thermal conductivity. To increase the optical power, we conducted optical
calculations and investigated the sources of loss. As a result of a search for alternative
electrical passivation materials, we fabricated HfO2 passivated lasers and
demonstrated about to two-fold reduction in optical loss and increase in optical
power.