Abstract-Resonant-phonon depopulation terahertz quantum cascade lasers and their application in spectroscopic imaging

P Dean, M Salih, S P Khanna, L H Li, N K Saat, A Valavanis, A Burnett,
J E Cunningham, A G Davies and E H Linfield


The terahertz (THz) frequency quantum cascade laser (QCL) is a semiconductor
heterostructure laser that has attracted much research interest over the past decade. We report
on the high performance of THz QCLs based on a three-well resonant-phonon (RP)
depopulation active region (AR) and operating in the frequency range 2.7 THz to 4.0 THz.
Devices, processed into surface-plasmon waveguides, lased up to 116 K in pulsed mode with
threshold current densities as low as 840 Acm−2. The effects of the design frequency and laser
cavity length on performance are discussed. We also report on the operation of QCLs with
reduced AR thicknesses, and show, for the first time, that the AR thickness of RP QCLs
processed in a surface plasmon waveguide can be reduced to as little as 5 μm. Finally, we
demonstrate the use of an electrically tuneable THz QCL, based on a heterogeneous AR, for
spectroscopic imaging of the high-explosive pentaerythritol tetranitrate

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http://iopscience.iop.org/0268-1242/27/9/094004/pdf/0268-1242_27_9_094004.pdf