Ultra-broadband and nonlinear THz spectroscopy

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The terahertz region of the light spectrum lies between microwave (frequencies < 100 GHz) and the optical (frequencies > 15 THz), and is the last part of the electromagnetic spectrum to be exploited for the benefit of society. Today, massive progress is being made to control light in this region, driven by a better understanding of the interactions of THz frequency light with novel materials. The potential benefits range from new imaging systems to ultra-high speed wireless communication. The proposed research is to investigate the ultrafast interactions of solid-state materials with extremely short pulses of THz frequency light, called THz pulses. Using recently developed methods, pulses with bandwidth covering the entire THz region and reaching into the mid-infrared can be generated, with over 10 times the bandwidth of conventional systems. This system will be the first of its kind in Canada. These 'ultrabroadband' THz pulses will be used to probe the motion of charges in novel materials such as semiconducting plastics and quantum dot arrays, on time scales shorter than 100 femtoseconds. This is important for determining crucial loss mechanisms that deteriorate the efficiency of next generation solar cells and other optoelectronic devices based on solution processable polymers and nanomaterials. By understanding these ultrafast processes, new materials can be synthesized to push the efficiency of these cheaply made solar cells to the point where they can be a significant source of renewable energy. In addition, new types of nonlinear interactions at THz frequencies will be investigated, now made possible for the first time by high intensity THz pulses from a table-top laser system. These experiments provide a glimpse into the coherent dynamics of charges in quantum-confined systems, and hold intriguing possibilities for future THz technologies and devices.