Circular and deformed microdisks quantum cascade lasers with surface plasmon waveguides at wavelengths from 19 micron

We report the fabrication and characterization of microdisk Quantum Cascade (QC) lasers with surface plasmon waveguides. Previously realized microdisk QC lasers employed fully dielectric waveguides, and therefore did not need the top contact to cover all the surface of the disk. Since the metal contact is however an integral part of the surface plasmon waveguide, the metallization must extend to the very edge of the disk in order to overlap with the most favorable whispering gallery modes. We developed a new processing recipe to obtain the desired result without abandoning the wet-etching processing, that produces very smooth sidewalls.