Sub-diffractional confinement of light has led to advancements in imaging, metamaterials, nano-manufacturing, plasmonics, and other fields. One potential route to sub-diffractional confinement is via stimulated surface phonon polaritons (SPhPs). SPhPs couple infrared photons with optical phonons and consequently their lifetimes can be longer than surface plasmon polaritons (SPPs), whose lifetimes are dominated by electron scattering events. Thus, materials capable of generating SPhPs are of general interest to study. SPhPs are activated by photons with energies near the Reststrahlen band of semiconductors such as SiC. In this work we examine aspects of carrier dynamics by photo-injecting electrons into the SiC conduction band using a pulsed 355 nm laser and probe the resulting dynamics near the Reststrahlen band using a tunable CO2 laser. The fluence of the pump laser was varied to provide photo-injection levels ranging from ~1x10^17 to 1x10^19 free carriers. Probing the excited-state dynamics near the blue-edge of the Reststrahlen band resulted in complex transient behavior, showing both positive and negative changes in transient reflectance depending on the level of photo-injected carriers and probe energy. Numerical calculations of the SiC reflectance spectra with different doping levels were done to simulate the initial photo-injection level provided by the transient experiment. The computed spectra and the experimentally measured excited spectra for different photo-injection levels were compared and resulted in qualitative agreement.
Bryan T. Spann, Ryan Compton, Adam D. Dunkelberger, James P. Long, Paul Klein, Daniel Ratchford, Josh D. Caldwell, and Jeff Owrutsky, "Understanding carrier injection effects upon the Reststrahlen band of SiC using transient infrared spectroscopy (Presentation Recording)," Proc. SPIE 9546, Active Photonic Materials VII, 95460M (Presented at SPIE Nanoscience + Engineering: August 10, 2015; Published: 5 October 2015); https://doi.org/10.1117/12.2187111.4519370249001.
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