Photoconductive emitter device with plasmonic electrodes
AssigneeThe Regents of the University of Michigan
InventorsMona Jarrahi, Christopher W. Berry, Shang-Hua Yang
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Abstract
A photoconductive device that includes a semiconductor substrate, an antenna assembly, and a photoconductive assembly with one or more plasmonic contact electrodes. The photoconductive assembly can be provided with plasmonic contact electrodes that are arranged on the semiconductor substrate in a manner that improves the quantum efficiency of the photoconductive device by plasmonically enhancing the pump absorption into the photo-absorbing regions of semiconductor substrate. In one exemplary embodiment, the photoconductive device is arranged as a photoconductive source and is pumped at telecom pump wavelengths (e.g., 1.0-1.6 μm) and produces milliwatt-range power levels in the terahertz (THz) frequency range.
Claims22
A photoconductive device for emitting terahertz (THz) radiation, comprising:
- a semiconductor substrate;
- an antenna assembly fabricated on the semiconductor substrate;
- and
- a photoconductor assembly fabricated on the semiconductor substrate and coupled to the antenna assembly, wherein the photoconductor assembly includes a plurality of plasmonic contact electrodes and wherein the photoconductive device is configured to receive optical input that impinges upon the photoconductor assembly and the plasmonic contact electrodes such that charge carriers are generated in the semiconductor substrate adjacent the plasmonic contact electrodes in response to the impinging optical input;
- wherein the plasmonic contact electrodes have sub-wavelength electrode spacing compared to at least one wavelength of the optical input, and wherein the plasmonic contact electrodes are configured to collect the generated charge carriers and are electrically connected to the antenna assembly such that collected charge carriers are conducted to the antenna assembly, whereby the plasmonic contact electrodes provide improved quantum efficiency of the photoconductive device when receiving the optical input.
A method of operating a photoconductive device having a semiconductor substrate that supports both an antenna assembly and a plurality of plasmonic contact electrodes, comprising the steps of:
- (a) receiving optical input at the semiconductor substrate;
- (b) promoting the excitation of surface plasmon waves or surface waves with the plasmonic contact electrodes, wherein the surface plasmon waves or surface waves influence the optical input so that a greater amount of optical input is absorbed by the semiconductor substrate and results in photocurrent in the semiconductor substrate;
- (c) applying a voltage to the antenna assembly so that a first portion of the photocurrent in the semiconductor substrate drifts toward a first antenna terminal and is conducted by at least some of the plasmonic contact electrodes to the first antenna terminal, and so that a second portion of the photocurrent in the semiconductor substrate drifts toward a second antenna terminal and is conducted by at least others of the plasmonic contact electrodes to the second antenna terminal;
- and
- (d) emitting terahertz (THz) radiation from the photoconductive device in response to the first and second antenna terminals being supplied with the first and second portions of photocurrent.
Dependencies are inferred from the claim text.