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Li X, Li J, Li Y, Ozcan A, Jarrahi M. High-throughput terahertz imaging: progress and challenges. LIGHT, SCIENCE & APPLICATIONS 2023; 12:233. [PMID: 37714865 PMCID: PMC10504281 DOI: 10.1038/s41377-023-01278-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 08/04/2023] [Accepted: 08/28/2023] [Indexed: 09/17/2023]
Abstract
Many exciting terahertz imaging applications, such as non-destructive evaluation, biomedical diagnosis, and security screening, have been historically limited in practical usage due to the raster-scanning requirement of imaging systems, which impose very low imaging speeds. However, recent advancements in terahertz imaging systems have greatly increased the imaging throughput and brought the promising potential of terahertz radiation from research laboratories closer to real-world applications. Here, we review the development of terahertz imaging technologies from both hardware and computational imaging perspectives. We introduce and compare different types of hardware enabling frequency-domain and time-domain imaging using various thermal, photon, and field image sensor arrays. We discuss how different imaging hardware and computational imaging algorithms provide opportunities for capturing time-of-flight, spectroscopic, phase, and intensity image data at high throughputs. Furthermore, the new prospects and challenges for the development of future high-throughput terahertz imaging systems are briefly introduced.
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Affiliation(s)
- Xurong Li
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Jingxi Li
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- Department of Bioengineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Yuhang Li
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- Department of Bioengineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Aydogan Ozcan
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
- Department of Bioengineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Mona Jarrahi
- Department of Electrical & Computer Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA.
- California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), Los Angeles, CA, 90095, USA.
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Liu L, Liu K, Liu N, Zhu Z, Zhang J. Fano-Resonant Metasurface with 92% Reflectivity Based on Lithium Niobate on Insulator. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3849. [PMID: 36364625 PMCID: PMC9657633 DOI: 10.3390/nano12213849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 10/28/2022] [Accepted: 10/29/2022] [Indexed: 06/16/2023]
Abstract
Lithium niobate is an excellent optoelectronic and nonlinear material, which plays an important role in integrated optics. However, lithium niobate is difficult to etch due to its very stable chemical nature, and the microstructure of lithium niobate's metasurface is generally of subwavelength, which further increases its processing difficulty. Here, by using Ar+-based inductively coupled plasma etching and KOH wet etching, we improve the etching quality and fabricate a Fano-resonant metasurface based on lithium niobate on insulator, which has a very high reflectivity of 92% at near-infrared wavelength and the potential of becoming a high-reflectivity film. In addition, to evaluate the practical performance of the metasurface, we constructed a Fabry-Perot cavity by using it as a cavity mirror, whose reflection spectrum shows a finesse of 38. Our work paves the way for the development of functional metasurfaces and other advanced photonic devices based on lithium niobate on insulator.
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Ponomarev DS, Lavrukhin DV, Zenchenko NV, Frolov TV, Glinskiy IA, Khabibullin RA, Katyba GM, Kurlov VN, Otsuji T, Zaytsev KI. Boosting photoconductive large-area THz emitter via optical light confinement behind a highly refractive sapphire-fiber lens. OPTICS LETTERS 2022; 47:1899-1902. [PMID: 35363764 DOI: 10.1364/ol.452192] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 02/16/2022] [Indexed: 05/27/2023]
Abstract
We report on a sapphire-fiber-based lens that can be used to enhance the emitted THz power of a large-area photoconductive antenna (PCA). Using numerical simulations, we demonstrate that the lens provides a spatial redistribution of the photocarriers density in the PCA's gap. By optimizing the diameter of the sapphire-fiber, one could reach efficient confinement of the photocarriers in the vicinity of the PCA electrodes with a 10-μm gap size for a 220-μm-thick sapphire-fiber. This allows enhancing the coupling of the incident electromagnetic waves at the interface between the sapphire fiber and the semiconductor with the antenna terminals by ∼40 times for a single PCA element, as well as boosting the total efficiency of the large-area PCA-emitter up to ∼7-10 times. To validate our approach, we propose a step-by-step process that can be used for the precise and controllable placement of the sapphire-fiber on the surface of a single PCA.
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Wang N, Jarrahi M. High-precision millimeter-wave frequency determination through plasmonic photomixing. OPTICS EXPRESS 2020; 28:24900-24907. [PMID: 32907020 DOI: 10.1364/oe.400806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 07/30/2020] [Indexed: 06/11/2023]
Abstract
We present a technique for high-precision millimeter-wave frequency determination through plasmonic photomixing. Our technique utilizes a plasmonic photomixer pumped by an optical frequency comb with a high-stability millimeter-wave beat frequency. The plasmonic photomixer down-converts the millimeter-wave signal to the radio frequency regime at which high-accuracy frequency counters are available. The precision of this technique is determined by the frequency stability of the optical beat frequency, which can be directly characterized in the presented experimental setup. We demonstrate frequency measurement precision as low as 3.9×10-10 at 95 GHz through plasmonic photomixing without phase-locking the optical frequency comb.
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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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Bashirpour M, Ghorbani S, Kolahdouz M, Neshat M, Masnadi-Shirazi M, Aghababa H. Significant performance improvement of a terahertz photoconductive antenna using a hybrid structure. RSC Adv 2017. [DOI: 10.1039/c7ra11398f] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Design of a photoconductive terahertz antenna based on a distributed Bragg reflector, recessed nanoplasmonic grating and recessed electrodes.
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Affiliation(s)
- M. Bashirpour
- School of Electrical and Computer Engineering
- Faculty of Engineering
- University of Tehran
- Tehran
- Iran
| | - S. Ghorbani
- School of Electrical and Computer Engineering
- Faculty of Engineering
- University of Tehran
- Tehran
- Iran
| | - M. Kolahdouz
- School of Electrical and Computer Engineering
- Faculty of Engineering
- University of Tehran
- Tehran
- Iran
| | - M. Neshat
- School of Electrical and Computer Engineering
- Faculty of Engineering
- University of Tehran
- Tehran
- Iran
| | - M. Masnadi-Shirazi
- School of Electrical and Computer Engineering
- Faculty of Engineering
- University of Tehran
- Tehran
- Iran
| | - H. Aghababa
- School of Electrical and Computer Engineering
- Faculty of Engineering
- University of Tehran
- Tehran
- Iran
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Yang SH, Watts R, Li X, Wang N, Cojocaru V, O'Gorman J, Barry LP, Jarrahi M. Tunable terahertz wave generation through a bimodal laser diode and plasmonic photomixer. OPTICS EXPRESS 2015; 23:31206-31215. [PMID: 26698749 DOI: 10.1364/oe.23.031206] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate a compact, robust, and stable terahertz source based on a novel two section digital distributed feedback laser diode and plasmonic photomixer. Terahertz wave generation is achieved through difference frequency generation by pumping the plasmonic photomixer with two output optical beams of the two section digital distributed feedback laser diode. The laser is designed to offer an adjustable terahertz frequency difference between the emitted wavelengths by varying the applied currents to the laser sections. The plasmonic photomixer is comprised of an ultrafast photoconductor with plasmonic contact electrodes integrated with a logarithmic spiral antenna. We demonstrate terahertz wave generation with 0.15-3 THz frequency tunability, 2 MHz linewidth, and less than 5 MHz frequency stability over 1 minute, at useful power levels for practical imaging and sensing applications.
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Yang SH, Jarrahi M. Spectral characteristics of terahertz radiation from plasmonic photomixers. OPTICS EXPRESS 2015; 23:28522-28530. [PMID: 26561122 DOI: 10.1364/oe.23.028522] [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
We present a comprehensive analysis of spectral characteristics of terahertz radiation from plasmonic photomixers. We fabricate plasmonic photomixer prototypes with plasmonic contact electrode gratings on a low temperature grown GaAs substrate and characterize the spectral properties of the generated terahertz radiation by use of a heterodyne detection scheme. Our analysis shows that linewidth, stability, and frequency tuning range of the generated terahertz radiation are directly determined by linewidth, stability, and wavelength tuning range of optical pump beam and not affected by device geometry, substrate properties, optical pump power level and other operational settings. Our study indicates the crucial role of optical sources in realizing high performance terahertz spectroscopy and wireless communication systems based on plasmonic photomixers.
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Berry CW, Hashemi MR, Preu S, Lu H, Gossard AC, Jarrahi M. Plasmonics enhanced photomixing for generating quasi-continuous-wave frequency-tunable terahertz radiation. OPTICS LETTERS 2014; 39:4522-4524. [PMID: 25078218 DOI: 10.1364/ol.39.004522] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We experimentally demonstrate an order of magnitude enhancement in the quasi-continuous-wave radiated power from a photomixer with plasmonic contact electrodes in comparison with an analogous conventional photomixer without plasmonic contact electrodes in the 0.25-2.5 THz frequency range when pumped at an optical wavelength of 1550 nm. The significant efficiency enhancement results from the unique capability of the plasmonic contact electrodes to reduce the average transport path of photocarriers to the device contact electrodes, increasing the ultrafast photocurrent that drives the terahertz antenna.
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