High-Power and High-Efficiency Operation of Terahertz Quantum Cascade Lasers at 3.3 THz

A high-power and high-effciency GaAs/A1GaAs-based terahertz （THz） quantum cascade laser structure emitting at 3.3 THz is presented. The structure is based on a hybrid bound-to-continuum transition and resonant-phonon extraction active region combined with a semi-insulating surface-plasmon waveguide. By optimizing material structure and device processing, the peak optical output power of 758mW with a threshold current density of 120 A/cm2 and a wall-plug effciency of 0.92% at 10K and 404mW at 77K are obtained in pulsed operation. The maximum operating temperature is as high as llS K. In the cw mode, a record optical output power of 160roW with a threshold current density of 178A/cm2 and a wall-plug efficiency of 1.32% is achieved at 1OK.

Quantum cascade lasers operating from 1.4 to 4 THz

The development of teranertz （THz） quantum cascade lasers （QCLs） has progressed considerably since their advent almost a decade ago.THz QCLs operating in a frequency range from 1.4 to 4 THz with electron-phonon scattering mediated depopulation schemes are described.Several different types of GaAs/AlGaAs superlattice designs are reviewed.Some of the best temperature performances are obtained by the so-called resonant-phonon designs that are described.Operation above a temperature of 160 K has been obtained across the spectrum for THz QCLs operating at ν 〉 1.8 THz.The maximum operating temperature of previously reported THz QCLs has empirically been limited to a value of ～ω/k B.A new design scheme for THz QCLs with scattering-assisted injection is shown to surpass this empirical temperature barrier,and is promising to improve the maximum operating temperatures of THz QCLs even further.

Review of terahertz semiconductor sources

Terahertz（THz） technology can be used in information science,biology,medicine,astronomy,and environmental science.THz sources are the key devices in THz applications.The author gives a brief review of THz semiconductor sources,such as GaAs_（1-x）N_x Gunn-like diodes,quantum wells（QWs） negative-effective-mass （NEM） THz oscillators,and the THz quantum cascade lasers（QCLs）.THz current self-oscillation in doped GaAs_（1-x）N_x diodes driven by a DC electric field was investigated.The current self-oscillation is associated with the negative differential velocity effect in the highly nonparabolic conduction band of this unique material system. The current self-oscillations and spatiotemporal current patterns in QW NEM p~＋pp~＋ diodes was studied by considering scattering contributions from impurities,acoustic phonons,and optic phonons.It is indicated that both the applied bias and the doping concentration strongly influence the patterns and self-oscillating frequencies.The NEM p~＋pp~＋ diode may be used as an electrically tunable THz source.Meanwhile,by using the Monte Carlo method, the device parameters of resonant-phonon THz QCLs were optimized.The results show that the calculated gain is more sensitive to the injection barrier width,the doping concentration,and the phonon extraction level separation, which is consistent with the experiments.