Abstract-Two-phonon-resonance terahertz quantum cascade laser based on GaN/AlGaN material system

Jinfeng Li, Ting Wan, Changshui Chen

https://iopscience.iop.org/article/10.1088/1361-6641/ab1401/pdf

In this paper, a two-phonon-resonance terahertz quantum cascade laser based on GaN/AlGaN material system is proposed. GaN/AlGaN material system is first studied in two-phonon-resonance active region structure by using rate equations. The active region adds an energy state above the upper laser state. The energy state difference between additional state and the upper laser state is equal to the longitudinal optical phonon energy which has a large magnitude (~90 meV). The simulation results show that the proposed terahertz quantum cascade can get better optical properties compared with the traditional three-level active region building in the same material system and has the superiority in improving electronic utilization. The results also show that two-phonon-resonance terahertz quantum cascade laser based on GaN/AlGaN material system can gain the peak output power of 8 mW at the temperature of 230 K.

Abstract-Broadband impedance match to two-dimensional materials in the terahertz domain

Phi H. Q. Pham, Weidong Zhang, Nhi V. Quach, Jinfeng Li, Weiwei Zhou, Dominic Scarmardo, Elliott R. Brown & Peter J. Burke,

https://www.nature.com/articles/s41467-017-02336-z

The coupling of an electromagnetic plane wave to a thin conductor depends on the sheet conductance of the material: a poor conductor interacts weakly with the incoming light, allowing the majority of the radiation to pass; a good conductor also does not absorb, reflecting the wave almost entirely. For suspended films, the transition from transmitter to reflector occurs when the sheet resistance is approximately the characteristic impedance of free space (Z0 = 377 Ω). Near this point, the interaction is maximized, and the conductor absorbs strongly. Here we show that monolayer graphene, a tunable conductor, can be electrically modified to reach this transition, thereby achieving the maximum absorptive coupling across a broad range of frequencies in terahertz (THz) band. This property to be transparent or absorbing of an electromagnetic wave based on tunable electronic properties (rather than geometric structure) is expected to have numerous applications in mm wave and THz components and systems.