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Wang W, Lu PK, Vinod AK, Turan D, McMillan JF, Liu H, Yu M, Kwong DL, Jarrahi M, Wong CW. Coherent terahertz radiation with 2.8-octave tunability through chip-scale photomixed microresonator optical parametric oscillation. Nat Commun 2022; 13:5123. [PMID: 36045124 PMCID: PMC9433451 DOI: 10.1038/s41467-022-32739-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 08/12/2022] [Indexed: 12/03/2022] Open
Abstract
High-spectral-purity frequency-agile room-temperature sources in the terahertz spectrum are foundational elements for imaging, sensing, metrology, and communications. Here we present a chip-scale optical parametric oscillator based on an integrated nonlinear microresonator that provides broadly tunable single-frequency and multi-frequency oscillators in the terahertz regime. Through optical-to-terahertz down-conversion using a plasmonic nanoantenna array, coherent terahertz radiation spanning 2.8-octaves is achieved from 330 GHz to 2.3 THz, with ≈20 GHz cavity-mode-limited frequency tuning step and ≈10 MHz intracavity-mode continuous frequency tuning range at each step. By controlling the microresonator intracavity power and pump-resonance detuning, tunable multi-frequency terahertz oscillators are also realized. Furthermore, by stabilizing the microresonator pump power and wavelength, sub-100 Hz linewidth of the terahertz radiation with 10-15 residual frequency instability is demonstrated. The room-temperature generation of both single-frequency, frequency-agile terahertz radiation and multi-frequency terahertz oscillators in the chip-scale platform offers unique capabilities in metrology, sensing, imaging and communications.
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Affiliation(s)
- Wenting Wang
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA.
| | - Ping-Keng Lu
- Terahertz Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - Abhinav Kumar Vinod
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - Deniz Turan
- Terahertz Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - James F McMillan
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - Hao Liu
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA
| | - Mingbin Yu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Shanghai, China
- Institute of Microelectronics, A*STAR, Singapore, 117865, Singapore
| | - Dim-Lee Kwong
- Institute of Microelectronics, A*STAR, Singapore, 117865, Singapore
| | - Mona Jarrahi
- Terahertz Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA.
| | - Chee Wei Wong
- Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles, CA, 90095, USA.
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2
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Chen WC, Yang SH. Thermal evaporated group IV Ge(Sn)-on-Si terahertz photoconductive antenna. OPTICS EXPRESS 2022; 30:31742-31751. [PMID: 36242250 DOI: 10.1364/oe.466108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 08/03/2022] [Indexed: 06/16/2023]
Abstract
We have experimentally demonstrated thermal evaporated group IV Ge1-xSnx-on-Si terahertz (THz) photoconductive antennas (PCA) pumped by an Er-doped femtosecond laser for broadband THz generation. The Ge1-xSnx THz PCAs, free from material epitaxial growth methods, can offer comparable material properties in photocarrier generation, transportation, recombination, and the collection as group III-V THz PCAs. At the optical pumping power of 90 mW and a bias voltage of 40V, the Ge1-xSnx THz PCAs have achieved a broadband spectrum over 1.5 THz with a 40 dB signal-to-noise ratio (SNR). This CMOS-compatible group IV THz source can be monolithically integrated on the Si photonic platform, paving the way toward THz system-on-chip (SoC) for many on-site applications in the non-destructive evaluation, biomedical imaging, and industrial inspections.
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3
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A Novel System for Quasi-Continuous THz Signal Transmission and Reception. SENSORS 2022; 22:s22124448. [PMID: 35746230 PMCID: PMC9227974 DOI: 10.3390/s22124448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/02/2022] [Accepted: 06/10/2022] [Indexed: 12/10/2022]
Abstract
This paper presents a novel system for generating and receiving quasi-continuous (QC) TeraHertz (THz) waves. A system design and theoretical foundation for QC-THz signal generation are presented. The proposed QC-THz system consists of commercially available photo-conductive antennas used for transmission and reception of THz waves and a custom-designed QC optical signal generator, which is based on a fast optical frequency sweep of a single telecom distributed-feedback laser diode and unbalanced optical fiber Michelson interferometer used for a high-frequency modulation. The theoretical model for the proposed system is presented and experimentally evaluated. The experimental results were compared to the state-of-the-art continuous-wave THz system. The comparison between the continuous-wave THz system and the proposed QC-THz system showed the ability to transmit and receive QC-THz waves up to 300 GHz. The upper-frequency limit is bounded by the length of the used Michelson interferometer. The presented design of THz signal generation has a potential for industrial application because it is cost-efficient and can be built using commercially available components.
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Optical Injection Locking for Generation of Tunable Low-Noise Millimeter Wave and THz Signals. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app112110185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This article presents the experimental demonstration of synchronization of two integrated semiconductor distributed Bragg reflector lasers, fabricated with a generic multiproject wafer platform, by means of injection locking. Substantial linewidth reduction and frequency stabilization of the lasers were shown during locking of the lasers to an optical frequency comb. Phase noise was measured for different injected powers and different laser cavities. For a generation of millimeter-wave signals up to 80 GHz, two lasers were simultaneously locked to the comb. Fine-tuning was performed by tuning the repetition rate of the comb and coarse-tuning was carried out by switching to another comb line. A suppression ratio of 37 dB was achieved for unwanted comb lines. The achieved signal purity, phase noise, and suppression of unwanted components demonstrate the viability of injection locking for the generation of high-quality signals at sub-THz and THz frequencies and with substantial tunability.
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Xie J, Ye W, Zhou L, Guo X, Zang X, Chen L, Zhu Y. A Review on Terahertz Technologies Accelerated by Silicon Photonics. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:1646. [PMID: 34201551 PMCID: PMC8306943 DOI: 10.3390/nano11071646] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/18/2021] [Accepted: 06/19/2021] [Indexed: 11/17/2022]
Abstract
In the last couple of decades, terahertz (THz) technologies, which lie in the frequency gap between the infrared and microwaves, have been greatly enhanced and investigated due to possible opportunities in a plethora of THz applications, such as imaging, security, and wireless communications. Photonics has led the way to the generation, modulation, and detection of THz waves such as the photomixing technique. In tandem with these investigations, researchers have been exploring ways to use silicon photonics technologies for THz applications to leverage the cost-effective large-scale fabrication and integration opportunities that it would enable. Although silicon photonics has enabled the implementation of a large number of optical components for practical use, for THz integrated systems, we still face several challenges associated with high-quality hybrid silicon lasers, conversion efficiency, device integration, and fabrication. This paper provides an overview of recent progress in THz technologies based on silicon photonics or hybrid silicon photonics, including THz generation, detection, phase modulation, intensity modulation, and passive components. As silicon-based electronic and photonic circuits are further approaching THz frequencies, one single chip with electronics, photonics, and THz functions seems inevitable, resulting in the ultimate dream of a THz electronic-photonic integrated circuit.
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Affiliation(s)
- Jingya Xie
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of shanghai for Science and Technology, Shanghai 200093, China; (J.X.); (W.Y.); (X.G.); (X.Z.); (L.C.)
| | - Wangcheng Ye
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of shanghai for Science and Technology, Shanghai 200093, China; (J.X.); (W.Y.); (X.G.); (X.Z.); (L.C.)
| | - Linjie Zhou
- State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
- SJTU-Pinghu Institute of Intelligent Optoelectronics, Pinghu 314200, China
| | - Xuguang Guo
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of shanghai for Science and Technology, Shanghai 200093, China; (J.X.); (W.Y.); (X.G.); (X.Z.); (L.C.)
| | - Xiaofei Zang
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of shanghai for Science and Technology, Shanghai 200093, China; (J.X.); (W.Y.); (X.G.); (X.Z.); (L.C.)
| | - Lin Chen
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of shanghai for Science and Technology, Shanghai 200093, China; (J.X.); (W.Y.); (X.G.); (X.Z.); (L.C.)
| | - Yiming Zhu
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of shanghai for Science and Technology, Shanghai 200093, China; (J.X.); (W.Y.); (X.G.); (X.Z.); (L.C.)
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Kuwashima F, Jarrahi M, Cakmakyapan S, Morikawa O, Shirao T, Iwao K, Kurihara K, Kitahara H, Furuya T, Wada K, Nakajima M, Tani M. Evaluation of high-stability optical beats in laser chaos by plasmonic photomixing. OPTICS EXPRESS 2020; 28:24833-24844. [PMID: 32907015 DOI: 10.1364/oe.399743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 07/21/2020] [Indexed: 06/11/2023]
Abstract
The stability of optical beats in a chaotically oscillating laser is compared to that of a free-running continuous-wave laser using a highly efficient plasmonic photomixer. Using a chaotically oscillating laser diode, stable optical beats are observed over an operation current range of 60-90 mA. The optical spectra are stable even with frequent mode hopping. In contrast, optical beats in a free-running continuous-wave laser are not stable compared to those of a chaotically oscillating laser, because of intermittent hopping of the laser modes. The high stability of chaotically oscillating lasers makes these lasers promising candidates for optical pump sources in terahertz time-domain spectroscopy systems.
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Lin YJ, Jarrahi M. Heterodyne terahertz detection through electronic and optoelectronic mixers. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2020; 83:066101. [PMID: 32208378 DOI: 10.1088/1361-6633/ab82f6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The high sensitivity detection of terahertz radiation is crucial for many chemical sensing, biomedical imaging, security screening, nondestructive quality control, high-data-rate communication, atmospheric, and astrophysics sensing applications. Among various terahertz detection techniques, heterodyne detection is of great interest for applications that require high spectral resolution. Heterodyne detection involves mixing the received terahertz radiation with a reference terahertz signal provided by a local oscillator and then down-converting it to an intermediate frequency for detection. The frequency of the intermediate frequency signal is usually chosen to be in the radio frequency regime, so that it can be accurately analyzed by well-developed radio frequency electronics, including amplifiers, filters, and spectrometers, for further processing. Heterodyne terahertz detection offers two major advantages over direct terahertz detection. First, the detected terahertz radiation is effectively enhanced by the reference local oscillator signal through the mixing process, thereby enabling the detection of very weak terahertz signals. Second, the detected noise power is effectively reduced by limiting the detected spectral bandwidth to the bandwidth of the intermediate frequency electronics. In this article, we present a broad overview of various types of heterodyne terahertz receivers, which utilize different electronic and optoelectronic techniques to down-convert the received terahertz signal to a radio frequency signal. We describe how the inherent nonlinearity of a Schottky diode, superconductor-insulator-superconductor junction, hot electron bolometer, and field-effect transistor can be utilized to mix the received terahertz radiation with a reference local oscillator signal from a gas laser, quantum cascade laser, photomixer, Gunn diode, IMPATT diode, and frequency multiplier and then down-convert it to a radio frequency signal. The down-converted radio frequency signal can be subsequently detected and analyzed by various backend spectrometers, including filter bank, acousto-optical, autocorrelator, fast Fourier transform, and chirp transform spectrometers. We also discuss how a photomixer pumped by a heterodyning optical beam can be used to down-convert the received terahertz radiation to a radio frequency signal with far fewer bandwidth constraints than conventional techniques. The advantages and disadvantages of different heterodyne receivers in terms of their noise performance, operation frequency, operation bandwidth, and operation temperature are discussed in detail.
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Affiliation(s)
- Yen-Ju Lin
- University of California, Los Angeles, CA 90095, United States of America
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Lin YJ, Cakmakyapan S, Wang N, Lee D, Spearrin M, Jarrahi M. Plasmonic heterodyne spectrometry for resolving the spectral signatures of ammonia over a 1-4.5 THz frequency range. OPTICS EXPRESS 2019; 27:36838-36845. [PMID: 31873455 DOI: 10.1364/oe.27.036838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 11/20/2019] [Indexed: 06/10/2023]
Abstract
We present a heterodyne terahertz spectrometry platform based on plasmonic photomixing, which enables the resolution of narrow spectral signatures of gases over a broad terahertz frequency range. This plasmonic heterodyne spectrometer replaces the terahertz mixer and local oscillator of conventional heterodyne spectrometers with a plasmonic photomixer and a heterodyning optical pump beam, respectively. The heterodyning optical pump beam is formed by two continuous-wave, wavelength-tunable lasers with a broadly tunable terahertz beat frequency. This broadly tunable terahertz beat frequency enables spectrometry over a broad bandwidth, which is not restricted by the bandwidth limitations of conventional terahertz mixers and local oscillators. We use this plasmonic heterodyne spectrometry platform to resolve the spectral signatures of ammonia over a 1-4.5 THz frequency range.
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Yardimci NT, Jarrahi M. Nanostructure-Enhanced Photoconductive Terahertz Emission and Detection. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1802437. [PMID: 30156383 DOI: 10.1002/smll.201802437] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 07/29/2018] [Indexed: 06/08/2023]
Abstract
Photoconductive antennas are commonly used for terahertz wave generation and detection. However, their relatively low radiation power and detection sensitivity often place limitations on the signal-to-noise ratio and operation bandwidth of terahertz imaging and spectroscopy systems. Several different techniques are attempted to address these limitations. The most promising ones take advantage of the unique tools provided by nanotechnology. In this review, the recent nanotechnology-enabled advances in photoconductive antennas, which use nanostructures, such as optical nanoantennas, plasmonic structures, and optical nanocavities, to increase the interaction of the optical pump beam with the photoconductive semiconductor, are discussed. All of these techniques are experimentally demonstrated to be efficient tools for enhancing the performance of photoconductive antennas for terahertz wave generation and detection.
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Affiliation(s)
- Nezih Tolga Yardimci
- Electrical and Computer Engineering Department, University of California - Los Angeles, Los Angeles, CA, 90046, USA
| | - Mona Jarrahi
- Electrical and Computer Engineering Department, University of California - Los Angeles, Los Angeles, CA, 90046, USA
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10
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Ghobadi A, Khan TM, Celik OO, Biyikli N, Okyay AK, Topalli K. A performance-enhanced planar Schottky diode for Terahertz applications: an electromagnetic modeling approach. INTERNATIONAL JOURNAL OF MICROWAVE AND WIRELESS TECHNOLOGIES 2017; 9:1905-1913. [DOI: 10.1017/s1759078717000940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
In this paper, we present the electromagnetic modeling of a performance-enhanced planar Schottky diode for applications in terahertz (THz) frequencies. We provide a systematic simulation approach for analyzing our Schottky diode based on finite element method and lumped equivalent circuit parameter extraction. Afterward, we use the developed model to investigate the effect of design parameters of the Schottky diode on parasitic capacitive and resistive elements. Based on this model, device design has been improved by deep-trench formation in the substrate and using a closed-loop junction to reduce the amount of parasitic capacitance and spreading resistance, respectively. The results indicate that cut-off frequency can be improved from 4.1 to 14.1 THz. Finally, a scaled version of the diode is designed, fabricated, and well characterized to verify the validity of this modeling approach.
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Li X, Yardimci NT, Jarrahi M. A polarization-insensitive plasmonic photoconductive terahertz emitter. AIP ADVANCES 2017; 7:115113. [PMID: 29204311 PMCID: PMC5690658 DOI: 10.1063/1.5006273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2017] [Accepted: 11/03/2017] [Indexed: 06/01/2023]
Abstract
We present a polarization-insensitive plasmonic photoconductive terahertz emitter that uses a two-dimensional array of nanoscale cross-shaped apertures as the plasmonic contact electrodes. The geometry of the cross-shaped apertures is set to maximize optical pump absorption in close proximity to the contact electrodes. The two-dimensional symmetry of the cross-shaped apertures offers a polarization-insensitive interaction between the plasmonic contact electrodes and optical pump beam. We experimentally demonstrate a polarization-insensitive terahertz radiation from the presented emitter in response to a femtosecond optical pump beam and similar terahertz radiation powers compared to previously demonstrated polarization-sensitive photoconductive emitters with plasmonic contact electrode gratings at the optimum optical pump polarization.
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Affiliation(s)
- Xurong Li
- Electrical Engineering Department, University of California - Los Angeles, Los Angeles, California 90095, USA
| | - Nezih Tolga Yardimci
- Electrical Engineering Department, University of California - Los Angeles, Los Angeles, California 90095, USA
| | - Mona Jarrahi
- Electrical Engineering Department, University of California - Los Angeles, Los Angeles, California 90095, USA
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12
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Mohandas RA, Freeman JR, Natrella M, Rosamond MC, Ponnampalam L, Fice MJ, Seeds AJ, Cannard PJ, Robertson MJ, Moodie DG, Davies AG, Linfield EH, Dean P. Terahertz generation mechanism in nano-grating electrode photomixers on Fe-doped InGaAsP. OPTICS EXPRESS 2017; 25:10177-10188. [PMID: 28468392 DOI: 10.1364/oe.25.010177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the generation mechanism associated with nano-grating electrode photomixers fabricated on Fe-doped InGaAsP substrates. Two different emitter designs incorporating nano-gratings coupled to the same broadband antenna were characterized in a continuous-wave terahertz (THz) frequency system employing telecommunications wavelength lasers for generation and coherent detection. The current-voltage characteristics and THz emission bandwidth of the emitters is compared for different bias polarities and optical polarisations. The THz output from the emitters is also mapped as a function of the position of the laser excitation spot for both continuous-wave and pulsed excitation. This mapping, together with full-wave simulations of the structures, confirms the generation mechanism to be due to an enhanced optical electric field at the grating tips resulting in increased optical absorption, coinciding with a concentration of the electrostatic field.
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Yardimci NT, Lu H, Jarrahi M. High power telecommunication-compatible photoconductive terahertz emitters based on plasmonic nano-antenna arrays. APPLIED PHYSICS LETTERS 2016; 109:191103. [PMID: 27916999 PMCID: PMC5106429 DOI: 10.1063/1.4967440] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 10/28/2016] [Indexed: 05/23/2023]
Abstract
We present a high-power and broadband photoconductive terahertz emitter operating at telecommunication optical wavelengths, at which compact and high-performance fiber lasers are commercially available. The presented terahertz emitter utilizes an ErAs:InGaAs substrate to achieve high resistivity and short carrier lifetime characteristics required for robust operation at telecommunication optical wavelengths. It also uses a two-dimensional array of plasmonic nano-antennas to offer significantly higher optical-to-terahertz conversion efficiencies compared to the conventional photoconductive emitters, while maintaining broad operation bandwidths. We experimentally demonstrate pulsed terahertz radiation over 0.1-5 THz frequency range with the power levels as high as 300 μW. This is the highest-reported terahertz radiation power from a photoconductive emitter operating at telecommunication optical wavelengths.
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Affiliation(s)
- Nezih Tolga Yardimci
- Electrical Engineering Department, University of California-Los Angeles , Los Angeles, California 90095, USA
| | - Hong Lu
- Department of Materials Science and Engineering, Nanjing University , Nanjing 210093, China
| | - Mona Jarrahi
- Electrical Engineering Department, University of California-Los Angeles , Los Angeles, California 90095, USA
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Xu J, Hou L, Deng Q, Han L, Liang S, Marsh JH, Zhu H. Fully integrated multi-optoelectronic synthesizer for THz pumping source in wireless communications with rich backup redundancy and wide tuning range. Sci Rep 2016; 6:29084. [PMID: 27381281 PMCID: PMC4933889 DOI: 10.1038/srep29084] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 06/09/2016] [Indexed: 11/09/2022] Open
Abstract
We report a monolithic photonic integrated circuit (PIC) for THz communication applications. The PIC generates up to 4 optical frequency lines which can be mixed in a separate device to generate THz radiation, and each of the optical lines can be modulated individually to encode data. Physically, the PIC comprises an array of wavelength tunable distributed feedback lasers each with its own electro-absorption modulator. The lasers are designed with a long cavity to operate with a narrow linewidth, typically <4 MHz. The light from the lasers is coupled via an multimode interference (MMI) coupler into a semiconductor optical amplifier (SOA). By appropriate selection and biasing of pairs of lasers, the optical beat signal can be tuned continuously over the range from 0.254 THz to 2.723 THz. The EAM of each channel enables signal leveling balanced between the lasers and realizing data encoding, currently at data rates up to 6.5 Gb/s. The PIC is fabricated using regrowth-free techniques, making it economic for volume applications, such for use in data centers. The PIC also has a degree of redundancy, making it suitable for applications, such as inter-satellite communications, where high reliability is mandatory.
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Affiliation(s)
- Junjie Xu
- Institute of Semiconductors, Chinese Academy of Sciences, No. A35, East Qinghua Road, Haidian District, Beijing 100083, P.R. China
| | - Lianping Hou
- School of Engineering, University of Glasgow, Glasgow, G12 8LT, UK
| | - Qiufang Deng
- Institute of Semiconductors, Chinese Academy of Sciences, No. A35, East Qinghua Road, Haidian District, Beijing 100083, P.R. China
| | - Liangshun Han
- Institute of Semiconductors, Chinese Academy of Sciences, No. A35, East Qinghua Road, Haidian District, Beijing 100083, P.R. China
| | - Song Liang
- Institute of Semiconductors, Chinese Academy of Sciences, No. A35, East Qinghua Road, Haidian District, Beijing 100083, P.R. China
| | - John H Marsh
- School of Engineering, University of Glasgow, Glasgow, G12 8LT, UK
| | - Hongliang Zhu
- Institute of Semiconductors, Chinese Academy of Sciences, No. A35, East Qinghua Road, Haidian District, Beijing 100083, P.R. China
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Mohammad-Zamani MJ, Neshat M, Moravvej-Farshi MK. Nanoslit cavity plasmonic modes and built-in fields enhance the CW THz radiation in an unbiased antennaless photomixers array. OPTICS LETTERS 2016; 41:420-423. [PMID: 26766729 DOI: 10.1364/ol.41.000420] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A new generation unbiased antennaless CW terahertz (THz) photomixer emitters array made of asymmetric metal-semiconductor-metal (MSM) gratings with a subwavelength pitch, operating in the optical near-field regime, is proposed. We take advantage of size effects in near-field optics and electrostatics to demonstrate the possibility of enhancing the THz power by 4 orders of magnitude, compared to a similar unbiased antennaless array of the same size that operates in the far-field regime. We show that, with the appropriate choice of grating parameters in such THz sources, the first plasmonic resonant cavity mode in the nanoslit between two adjacent MSMs can enhance the optical near-field absorption and, hence, the generation of photocarriers under the slit in the active medium. These photocarriers, on the other hand, are accelerated by the large built-in electric field sustained under the nanoslits by two dissimilar Schottky barriers to create the desired large THz power that is mainly radiated downward. The proposed structure can be tuned in a broadband frequency range of 0.1-3 THz, with output power increasing with frequency.
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