MIOMD-XI Speakers    
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1.  Dr. Kamil Pierscinski, Institute of Electron Technology, POLAND
Late-Breaking Results: Thermal characteristics and power roll-over of GaAs/AlGaAs quantum cascade lasers
Speaker Biography: Kamil Pierściński received the M.Sc. & Eng. degree in physics from the Warsaw University of Technology in 2004 and the Ph.D. degree in semiconductor laser physics from the Institute of Electron Technology, Warsaw, Poland in 2009, where he is currently employed. His research interests focus on optical spectroscopy of semiconductor materials and devices. Current research topics include electrical, spectral and thermal characterization of semiconductor lasers with emphasis on QCLs and VECSELs. He is also involved in photoluminescence study of type-II GaSb-based superlattices for detector applications.

Summary: The GaAs/AlGaAs quantum cascade lasers (QCLs) are important infrared light sources with various applications in defense and civilian fields for environmental monitoring, medical diagnostics and other gas sensing applications. Their application is however limited by degradation of performance characteristics induced by the strong heating of their active regions. The large electrical power density required for operation, and the low thermal conductivity of complex multilayer heterostructures contribute to high temperature gradients in the devices. Elevated temperatures cause the leakage of electrons from the upper laser level into delocalized continuum states and backfilling of the lower laser level; both effects decreasing the population inversion. These are the main limiting factors of the high temperature operation of the devices. To expand the potential applications of QCLs, high power levels, high wall plug efficiency and duty cycle are required. Therefore the in depth experimental analysis of laser characteristics combined with numerical modeling is essential to understand the thermal processes and power rollover mechanisms in QCLs. The devices investigated in this paper were designed and fabricated at the Institute of Electron Technology. The number of experimental techniques has been used for the thermal characterization of QCLs: thermoreflectance spectroscopy, temperature dependent Light - Current-Voltage (L-I-V) characteristics and spectral characteristics. The experimental results are compared with thermal modeling of QC lasers performed by finite element analysis (FEA). The QCLs were placed in liquid nitrogen cryostat, allowing L-I-V measurements in temperature range from 77 K up to room temperature (300 K). Devices were driven with 200 ns pulses of 1 kHz frequency.
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