Observation of optical feedback dynamics in single-mode terahertz quantum cascade lasers: Transient instabilities

Lateral distributed-feedback gratings for single-mode, high-power terahertz quantum-cascade lasers.

We report on terahertz quantum-cascade lasers (THz QCLs) based on first-order lateral distributed-feedback (lDFB) gratings, which exhibit continuous-wave operation, high output powers (>8 mW), and single-mode emission at 3.3-3.4 THz. A general method is presented to determine the coupling coefficients of lateral gratings in terms of the coupled-mode theory, which demonstrates that large couplin...

Nanowire terahertz quantum cascade lasers

Ultrafast population dynamics in electrically modulated terahertz quantum cascade lasers

The ultrafast population dynamics in electrically modulated threewell terahertz quantum cascade lasers (QCLs) is studied by using the selfconsistent Bloch–Poisson equations. In the modulation process, the nonequilibrium oscillations of the population inversion are found before the population equilibrium recovers. The equilibrium formation time increases nonlinearly with the period number. This ...

Terahertz quantum cascade lasers based on intra-well optical transitions

The possibility to achieve laser action at different THz frequencies employing the so-called vertical transition will be discussed. The intra-well or vertical optical transition presents a number of features that makes it an ideal candidate for a systematic study of resonant tunnelling and dephasing in quantum cascade lasers. Laser action at 3.5 THz with very low threshold employing a single qu...

Low divergence single-mode surface-emitting concentric-circular-grating terahertz quantum cascade lasers.

We report the design, fabrication and experimental characterization of surface-emitting terahertz (THz) frequency quantum cascade lasers (QCLs) with distributed feedback concentric-circular-gratings. Single-mode operation is achieved at 3.73 THz with a side-mode suppression ratio as high as ~30 dB. The device emits ~5 times the power of a ridge laser of similar dimensions, with little degradati...