Terahertz Electro-Optics and Intersubband Micro-Plasmonics in Semiconductor Quantum Well Devices

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*****NON-TECHNICAL ABSTRACT**** This research program explores the response of semiconductor devices (designed and fabricated at UC Santa Barbara) in the "terahertz (THz) gap" of the electromagnetic spectrum between 0.1 and 10 THz. A frequency of 1 THz corresponds to 1 trillion (1012) cycles per second, 1000 times faster than the frequency at which cell phones broadcast, and 500 times lower than the frequency of green light. A new kind of detector for terahertz radiation will be explored, potentially useful for applications including security, medicine, and non-destructive materials testing. At the heart of this detector is a "gas" of electrons confined in a thin layer. The electrons will be forced perpendicular to the layer to search for the simultaneous existence of two stable operating states ("optical bistability," potentially useful as a terahertz-activated switch), spontaneous oscillation (a potential terahertz source) and a "chaotic" current induced by periodic driving (chaos is not normally observed in quantum mechanical systems). Strong terahertz radiation will also be used to enhance the functionalities of semiconductor optical devices, such as optical modulators used to transmit information over fiber-optic cables. Undergraduates, graduate students and post-doctoral researchers will receive broad experimental training. Along with the PI, they will bring novel outreach materials to local K-12 schools. *****TECHNICAL ABSTRACT**** This research program explores the response of semiconductor quantum devices, designed and fabricated at UC Santa Barbara, to electromagnetic fields in the region of the spectrum between 0.1 and 10 THz. A new kind of antenna-coupled detector for terahertz radiation, based on intersubband transitions in semiconductor quantum wells, will be used as a platform for investigating a wide range of nonlinear quantum phenomena which are predicted to occur when a 2-D electron gas is forced perpendicular to the plane in which it is confined. The nonlinearity arises in theories from the strong electron-electron interaction. Strong THz radiation will also be used to search for modifications of the near-IR transmission of quantum wells. Predictions include cross-modulation of arbitrarily weak NIR beams in the presence of strong THz driving. Undergraduates, graduate students and post-doctoral researchers will receive broad experimental training. They and the PI will also bring novel outreach materials to local K-12 schools.