RESUMO
We report planar integration of tapered terahertz (THz) frequency quantum cascade lasers (QCLs) with metasurface waveguides that are designed to be spoof surface plasmon (SSP) out-couplers by introducing periodically arranged SSP scatterers. The resulting surface-emitting THz beam profile is highly collimated with a divergence as narrow as ~4° × 10°, which indicates a good waveguiding property of the metasurface waveguide. In addition, the low background THz power implies a high coupling efficiency for the THz radiation from the laser cavity to the metasurface structure. Furthermore, since all the structures are in-plane, this scheme provides a promising platform where well-established surface plasmon/metasurface techniques can be employed to engineer the emitted beam of THz QCLs controllably and flexibly. More importantly, an integrated active THz photonic circuit for sensing and communication applications could be constructed by incorporating other optoelectronic devices such as Schottky diode THz mixers, and graphene modulators and photodetectors.
RESUMO
Electrically pumped random lasers, operating in the mid-infrared regime at λ ≈ 10 µm, are realized for the first time. Randomly distributed air holes are patterned onto a quantum cascade wafer emitting in the transverse-magnetic (TM) polarization. The advantage of employing TM polarized gain medium is that TM modes are more effectively confined in the gain region, and thus improve lasing efficiency and vertical confinement compared to TE modes.