Photonic Majorana quantum cascade laser with polarization-winding emission.

Topological cavities, whose modes are protected against perturbations, are promising candidates for novel semiconductor laser devices. To date, there have been several demonstrations of topological lasers (TLs) exhibiting robust lasing modes. The possibility of achieving nontrivial beam profiles in TLs has recently been explored in the form of vortex wavefront emissions enabled by a structured optical pump or strong magnetic field, which are inconvenient for device applications.

Broadband and photovoltaic THz/IR response in the GaAs-based ratchet photodetector.

High-performance broadband infrared (IR)/terahertz (THz) detection is crucial in many optoelectronic applications. However, the spectral response range of semiconductor-based photodetectors is limited by the bandgaps. This paper proposes a ratchet structure based on the GaAs/AlGaAs heterojunction, where the quasi-stationary hot hole distribution and intravalence band absorption from light or heavy hole states to the split-off band overcome the bandgap limit, ensuring an ultrabroadband photoresponse from near-IR to THz region (4 to 300 THz).

Electrically pumped topological laser with valley edge modes.

Quantum cascade lasers are compact, electrically pumped light sources in the technologically important mid-infrared and terahertz region of the electromagnetic spectrum. Recently, the concept of topology has been expanded from condensed matter physics into photonics, giving rise to a new type of lasing using topologically protected photonic modes that can efficiently bypass corners and defects. Previous demonstrations of topological lasers have required an external laser source for optical pumping and have operated in the conventional optical frequency regime.