Generation of THz transients by photoexcited single-crystal GaAs meso-structures |
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Authors: | Jie Zhang Martin Mikulics Roman Adam Detlev Grützmacher Roman Sobolewski |
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Affiliation: | 1. Department of Electrical and Computer Engineering and Laboratory for Laser Energetics, University of Rochester, Rochester, NY, 14627-0231, USA 7. Center for Visual Science, University of Rochester, Rochester, NY, 14642, USA 2. Peter Grünberg Institut (PGI-9), Research Centre Jülich, Jülich, 52425, Germany 3. Jülich-Aachen Research Alliance (JARA)-Fundamentals of Future Information Technology, 52425, Jülich, Germany 4. Peter Grünberg Institut (PGI-6), Research Centre Jülich, Jülich, 52425, Germany 5. Department of Physics and Astronomy and the Materials Science Program, University of Rochester, Rochester, NY, 14627, USA 6. Institute of Electron Technology, 02668, Warszawa, Poland
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Abstract: | We report a sub-picosecond photoresponse and THz transient generation of GaAs single-crystal mesoscopic platelets excited by femtosecond optical pulses. Our structures were fabricated by a top-down technique, by patterning an epitaxial, 500-nm-thick GaAs film grown on top of an AlAs sacrificial layer and then transferring the resulting etched away 10 × 20-μm2 platelets onto an MgO substrate using a micropipette. The freestanding GaAs devices, incorporated into an Au coplanar strip line, exhibited extremely low dark currents and ~0.4 % detection efficiency at 10 V bias. The all-optical, pump–probe carrier dynamics analysis showed that, for 800-nm-wavelength excitation, the intrinsic relaxation of photocarriers featured a 310-fs-wide transient with a 290 fs fall time. We have also carried out a femtosecond, time-resolved electro-optic characterization of our devices and recorded along the transmission line the electrical transients as short as ~600 fs, when the platelet was excited by a train of 100-fs-wide, 800-nm-wavelength optical laser pulses. The platelets have been also demonstrated to be very efficient generators of free-space propagating THz transients with the spectral bandwidth exceeding 2 THz. The presented performance of the epitaxial, freestanding GaAs meso-structured photodevices makes them uniquely suitable for THz-frequency optoelectronic applications, ranging from ultrafast photodetectors to THz-bandwidth optical-to-electrical transducers and photomixers. |
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