Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 108: Poster: Ultra-fast phenomena / Optical properties / Semiconductor laser / Devices and device concepts

HL 108.22: Poster

Donnerstag, 3. April 2014, 17:00–20:00, P1

Characterization of Quantum Cascade Lasers in the Terahertz Regime — •Negar Hekmat1,2, Hanond Nong1, Shovon Pal1,2, Michael Kwiatek2, Arne Ludwig2, Paul Dean3, Edmund Linfield3, Andreas D. Wieck2, and Nathan Jukam11AG Terahertz-Spektroskopie und Technologie, Ruhr-Universität Bochum, Germany — 2Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Germany — 3School of Electrical Engineering, University of Leeds, UK

Quantum cascade lasers (QCLs) are powerful radiation sources in mid- and far-infrared regions with potential applications in imaging, sensing and spectroscopy. QCLs are unipolar semiconductor devices based on intersubband transitions. The active region of the QCL is a periodic sequence of modules made of multiple quantum wells. The electrons are transported in a 'cascading' scheme where several photons are generated by a single electron. QCLs are often fabricated by Molecular Beam Epitaxy (MBE), which precisely controls the thickness of the quantum wells and barriers. Terahertz time domain spectroscopy (THz-TDS) was used to characterise a THz QCL operating at 2.26 THz. The GaAs/AlGaAs QCL was cleaved and mounted on a cryostat sample holder. The Current-Voltage characteristic of the QCL was investigated in the range of 10-70 K. The gain of THz QCL was also studied with and without radio frequency (RF) pulses. Gain clamping was observed when the RF pulse was off and the QCL was biased above threshold. However, with the RF pulse on and the QCL biased below threshold, the THz pulse amplitude through the QCL increased.

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