Low-voltage terahertz quantum-cascade lasers based on LO-phonon-assisted interminiband transitions

The MBE growth and optimization of high performance terahertz frequency quantum cascade lasers

“…Once the background is < 5 × 10 14 cm -3 (p-type in our case), a series of THz QCL active region designs were grown by solid-source MBE on semi-insulating GaAs substrates. These included: the bound-to-continuum active region design with a single-quantum-well phonon extraction/injection stage presented in [9] (denoted BTC-RP); the modified BTC-RP design presented in [6] (denoted M-BTC-RP); and, the multiple quantum well design with LO-phonon-assisted interminiband transitions presented in [8] ). Immediately prior to growth, the GaAs and AlAs growth rates were determined using BandiT spectrometry to calibrate the layer thicknesses and aluminum mole fractions [6,15].…”

“…The output power was then calculated from the measured average power and duty cycle. Unlike some earlier reports [7,8], neither a light-pipe nor a Winston core were used, despite a separation (d) of ~3.5 cm between the power meter and the device facet. Furthermore, no correction for collection efficiency is applied to any of the powers reported in this paper.…”

“…This rapid development has included implementation of novel waveguide schemes [3,7], continuous improvements in active region designs [2][3][4][5][6][7][8][9][10], and device realization in the mature GaAs/AlGaAs material system, with material grown by established technologies such as molecular beam epitaxy (MBE). The growth of THz QCLs does, however, remain extremely challenging, owing to the stringent demands for precise control of individual layer thicknesses and alloy compositions, which must be maintained over the, typically, 10 µm thick active regions.…”

THz quantum-cascade laser as a local oscillator for SOFIA

“…They are based on a two-miniband design and were developed for continuous-wave operation, high output powers, and low electrical pump powers [1]. Efficient carrier injection is achieved by resonant longitudinal-optical phonon scattering.…”

Feedhorn-integrated THz QCL local oscillators for the LOCUS atmospheric sounder

“…A 9-well hybrid QCL active region [3] was chosen, owing to its high THz output power and operating temperature range. The design was adapted for emission frequency at 3.5 THz and the resulting GaAs/Al 0.15 Ga 0.85 As heterostructure was grown using molecular-beam epitaxy on a semi-insulating GaAs substrate.…”