Terahertz Photonic Devices

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0245461KerstingCurrent communications technologies make use of either electronics operating in the low frequency region of the electro-magnetic spectrum or of photonic techniques in the optical spectrum. Between these regions, the terahertz (THz) frequency band extends from 100 GHz to 100 THz. Above few hundred GHz, no technology for signal processing is available, although many semiconductor-based THz emitters and detectors have been developed during the past decade. The PI proposes to develop photonic semiconductor heterostructure devices that will allow the manipulation of THz signals as well as logical processing of ultrafast THz pulses. The goals of this project are to deduce fundamental properties of THz intersubband devices and to demonstrate a proof of concept for photonic signal processing at THz frequencies. The strategic approach of the proposed work is to fabricate semiconductor heterostructure devices and to demonstrate their operation at THz frequencies. The devices will consist of modulation n-doped GaAs/AlGaAs heterostructures, which have intersubband resonances at THz frequencies. The devices will be characterized by THz techniques, which directly show the device performance in time-domain. In the first step the PI will investigate the linear properties of THz devices and will characterize them with respect to modulation frequency, efficiency, and operation temperature. Fundamental logical operations will be demonstrated in free-space geometry. In the second step we will focus on the nonlinear regime. Absorption saturation and negative differential behavior will be demonstrated. Finally, device integration will be investigated. Results on the required device dimensions will give insight into future integration densities.Terahertz photonics with semiconductor heterostructures is a novel concept for ultrafast signal processing and may allow switching rates beyond 1 THz. The expected results may impact optical fiber communications and high speed interconnects between chips. Besides the expected speed, two technological arguments make THz photonics attractive: The compatibility of THz photonics with standard semiconductor device fabrication technologies and the reduced heat dissipation due to low switching energies.Graduate and undergraduate students will participate in the proposed research. All students will gain a multidisciplinary education, which covers semiconductor device technology, THz technology, and photonics.