Far-Infrared Emission from Electrically Injected Phonon-Polariton Lasers

This dissertation aims to advance the fundamental optical toolkit by designing, fabricating, and characterizing novel FIR light sources that drastically exceed the state-of-the-art. These new devices will engineer interactions between lattice vibrations and quantum structures to generate FIR electromagnetic radiation that exceeds the emission from blackbody sources. In particular, we develop traditional III-V semiconductor materials and opto-phononic-electronic (OPE) devices by engineering electronic transport and optical modes, and the interaction between photons and phonons.

This work has shown two structures of FIR emitters, including the surface cascaded phonon-polariton emitters, and metal-metal waveguide phonon-polariton emitters. The work demonstrated both the photonic and phononic characterization of each of these devices. First, surface cascade devices exhibit strong emission close to the GaAs LO phonon energy. The emission is compared directly to thermal emission. Second, we show the modeling and experimental results for phonon-polariton edge emitters, including the quantum model of gain, quantum well heterostructure design, polariton dispersion, fabrication, and electrical characterization. Finally, to investigate the photon-electron-phonon tripartite coupling mechanism and thermal characteristics of such complex infrared emitters, we use Raman spectroscopy-based techniques to determine the temperature distribution and thermal conductivity from a continuous wave (CW) mode quantum cascade laser (QCL) at room temperature. The work has shown the Raman peak shift of both the InAs transverse optical (TO) and GaAs TO phonons provide a robust way to cross-check the extracted output facet temperature and anisotropic thermal conductivity. The techniques provide a valuable toolkit to characterize the thermal emission and optical emission in the OPE devices in the FIR range. This work is important for the design of the QCL-based photonic integrated circuits in the infrared wavelengths, improving the accuracy of device selection, failure analysis, and thermal management in manufacturing.