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ABSTRACT: We report terahertz quantum cascade lasers operating in pulsed mode at an emission frequency of 3 THz and up to a maximum temperature of 178 K. The improvement in the maximum operating temperature is achieved by using a three-quantum-well active region design with resonant-phonon depopulation and by utilizing copper, instead of gold, for the cladding material in the metal-metal waveguides.
Optics Express 04/2008; 16(5):3242-8. · 3.59 Impact Factor
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ABSTRACT: We investigate the implementation of surface emission via a second order grating in terahertz quantum cascade lasers with double-metal waveguides. Absorbing edge structures are designed to enforce anti-reflecting boundary conditions, which ensure distributed feedback in the cavity. The grating duty cycle is chosen in order to maximize slope efficiency. Fabricated devices demonstrate surface emission output powers that are comparable to those measured from edge-emitting double metal waveguide structures without gratings. The slope efficiency of surface emitting lasers is twice that of double-metal edge emitting structures. Surface emitting lasers show single mode behavior, with a beam divergence of approximately six degrees.
Optics Express 12/2006; 14(24):11672-80. · 3.59 Impact Factor
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ABSTRACT: Results are presented for two GaAs/AlGaAs quantum cascade laser (QCL) structures that emit at frequencies of 2.59 and 2.75 THz. Both structures have a nominally identical, bound-to-continuum active region design, and the difference between their emission frequencies is interpreted as resulting from small differences in the gallium and aluminium growth rates, which were measured both before and after laser growth using a pyrometric spectrometry technique. The same technique allows the QCL growth itself to be monitored real-time, and drifts in growth rates identified.
Physica E Low-dimensional Systems and Nanostructures 40(6):1859-1861. · 1.53 Impact Factor
