An Integrated Germanium-Based THz Impulse Radiator with an Optical Waveguide Coupled Photoconductive Switch in Silicon
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Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA
2
Department of Electrical and Computer Engineering, University of California at Los Angeles, Los Angeles, CA 90095, USA
*
Author to whom correspondence should be addressed.
Micromachines 2019, 10(6), 367; https://doi.org/10.3390/mi10060367
Received: 5 May 2019
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Revised: 14 May 2019
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Accepted: 16 May 2019
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Published: 31 May 2019
(This article belongs to the Special Issue Silicon Photonics Bloom)
This paper presents an integrated germanium (Ge)-based THz impulse radiator with an optical waveguide coupled photoconductive switch in a low-cost silicon-on-insulator (SOI) process. This process provides a Ge thin film, which is used as photoconductive material. To generate short THz impulses, N++ implant is added to the Ge thin film to reduce its photo-carrier lifetime to sub-picosecond for faster transient response. A bow-tie antenna is designed and connected to the photoconductive switch for radiation. To improve radiation efficiency, a silicon lens is attached to the substrate-side of the chip. This design features an optical-waveguide-enabled “horizontal” coupling mechanism between the optical excitation signal and the photoconductive switch. The THz emitter prototype works with 1550 nm femtosecond lasers. The radiated THz impulses achieve a full-width at half maximum (FWHM) of 1.14 ps and a bandwidth of 1.5 THz. The average radiated power is 0.337 W. Compared with conventional THz photoconductive antennas (PCAs), this design exhibits several advantages: First, it uses silicon-based technology, which reduces the fabrication cost; second, the excitation wavelength is 1550 nm, at which various low-cost laser sources operate; and third, in this design, the monolithic excitation mechanism between the excitation laser and the photoconductive switch enables on-chip programmable control of excitation signals for THz beam-steering.
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Keywords:
germanium; integrated optics; optoelectronics; photoconductivity; silicon photonics; terahertz
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MDPI and ACS Style
Chen, P.; Hosseini, M.; Babakhani, A. An Integrated Germanium-Based THz Impulse Radiator with an Optical Waveguide Coupled Photoconductive Switch in Silicon. Micromachines 2019, 10, 367. https://doi.org/10.3390/mi10060367
AMA Style
Chen P, Hosseini M, Babakhani A. An Integrated Germanium-Based THz Impulse Radiator with an Optical Waveguide Coupled Photoconductive Switch in Silicon. Micromachines. 2019; 10(6):367. https://doi.org/10.3390/mi10060367
Chicago/Turabian StyleChen, Peiyu, Mostafa Hosseini, and Aydin Babakhani. 2019. "An Integrated Germanium-Based THz Impulse Radiator with an Optical Waveguide Coupled Photoconductive Switch in Silicon" Micromachines 10, no. 6: 367. https://doi.org/10.3390/mi10060367
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