[1] [1] SMITH P R, AUSTON D H, NUSS M C. Subpicosecond photoconducting dipole antennas[J]. IEEE Journal of Quantum Electronics, 1988, 24(2): 255-260. DOI: 10.1109/3.121.

[2] [2] FATTINGER C, GRISCHKOWSKY D. Terahertz beams[J]. Applied Physics Letters, 1989, 54(6): 490-492. DOI: 10.1063/1.100958.

[3] [3] HU B B, NUSS M C. Imaging with terahertz waves[J]. Optics Letters, 1995, 20(16): 1716-1718. DOI: 10.1364/OL.20.001716.

[4] [4] ZIMDARS D, WHITE J S. Terahertz reflection imaging for package and personnel inspection[C]//Terahertz for Military and Security Applications II. Orlando, Florida, US: Defense and Security, 2004: 78-83. DOI: 10.1117/12.562216.

[5] [5] ZHONG Hua, XU Jingzhou, XIE Xu, et al. Nondestructive defect identification with terahertz time-of-flight tomography[J]. IEEE Sensors Journal, 2005, 5(2): 203-208. DOI: 10.1109/JSEN.2004.841341.

[6] [6] KATLETZ S, PFLEGER M, PHRINGER H, et al. Efficient terahertz en-face imaging[J]. Optics Express, 2011, 19(23): 23042-23053. DOI: 10.1364/OE.19.023042.

[7] [7] YEE D S, JIN K H, YAHNG J S, et al. High-speed terahertz reflection three-dimensional imaging using beam steering[J]. Optics Express, 2015, 23(4): 5027-5034. DOI: 10.1364/OE.23.005027.

[8] [8] HARRIS Z B, VIRK A, KHANI M E, et al. Terahertz time-domain spectral imaging using telecentric beam steering and anf-scanning lens: distortion compensation and determination of resolution limits[J]. Optics Express, 2020, 28(18): 26612-26622. DOI: 10.1364/OE.398706.

[9] [9] YASUI T, SAWANAKA K I, IHARA A, et al. Real-time terahertz color scanner for moving objects[J]. Optics Express, 2008, 16(2): 1208-1221. DOI: 10.1364/OE.16.001208.

[10] [10] BLANCHARD F, DOI A, TANAKA T, et al. Real-time terahertz near-field microscope[J]. Optics Express, 2011, 19(9): 8277-8284. DOI: 10.1364/OE.19.008277.

[12] [12] DUVILLARET L, GARET F, COUTAZ J L. A reliable method for extraction of material parameters in terahertz time-domain spectroscopy[J]. IEEE Journal of Selected Topics in Quantum Electronics, 1996, 2(3): 739-746. DOI: 10.1109/2944.571775.

[13] [13] DORNEY T D, BARANIUK R G, MITTLEMAN D M. Material parameter estimation with terahertz time-domain spectroscopy[J]. Journal of the Optical Society of America. A, Optics, Image Science, and Vision, 2001, 18(7): 1562-1571. DOI: 10.1364/josaa.18.001562.

[14] [14] BOLIVAR P H, BRUCHERSEIFER M, RIVAS J G, et al. Measurement of the dielectric constant and loss tangent of high dielectric-constant materials at terahertz frequencies[J]. IEEE Transactions on Microwave Theory and Techniques, 2003, 51(4): 1062-1066. DOI: 10.1109/TMTT.2003.809693.

[15] [15] WITHAYACHUMNANKUL W, FERGUSON B, RAINSFORD T, et al. Simple material parameter estimation via terahertz time-domain spectroscopy[J]. Electronics Letters, 2005, 41(14): 800-801. DOI: 10.1049/el:20051467.

[16] [16] PUPEZA I, WILK R, KOCH M. Highly accurate optical material parameter determination with THz time-domain spectroscopy[J]. Optics Express, 2007, 15(7): 4335-4350. DOI: 10.1364/OE.15.004335.

[17] [17] TOMAINO J L, JAMESON A D, KEVEK J W, et al. Terahertz imaging and spectroscopy of large-area single-layer graphene[J]. Optics Express, 2011, 19(1): 141-146. DOI: 10.1364/OE.19.000141.

[18] [18] TOMAINO J L, JAMESON A D, PAUL M J, et al. High-contrast imaging of graphene via time-domain terahertz spectroscopy[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2012, 33(8): 839-845. DOI: 10.1007/s10762-012-9889-7.

[19] [19] BGGILD P, MACKENZIE D M A, WHELAN P R, et al. Mapping the electrical properties of large-area graphene[J]. 2D Materials, 2017, 4(4): 042003. DOI: 10.1088/2053-1583/aa8683.

[20] [20] SPIES J A, NEU J, TAYVAH U T, et al. Terahertz spectroscopy of emerging materials[J]. The Journal of Physical Chemistry C, 2020, 124(41): 22335-22346. DOI: 10.1021/acs.jpcc.0c06344.

[21] [21] OZAKI Y. Infrared spectroscopy-mid-infrared, near-infrared, and far-infrared/terahertz spectroscopy[J]. Analytical Sciences, 2021, 37(9): 1193-1212. DOI: 10.2116/analsci.20R008.

[22] [22] FU Xiaojian, LIU Yujie, CHEN Qi, et al. Applications of terahertz spectroscopy in the detection and recognition of substances[J]. Frontiers in Physics, 2022(10): 3389. DOI: 10.3389/fphy.2022.869537.

[23] [23] AUSTON D H, CHEUNG K P, SMITH P R. Picosecond photoconducting Hertzian dipoles[J]. Applied Physics Letters, 1984, 45(3): 284-286. DOI: 10.1063/1.95174.

[24] [24] ZHANG X C, AUSTON D H. Optoelectronic measurement of semiconductor surfaces and interfaces with femtosecond optics[J]. Journal of Applied Physics, 1992, 71(1): 326-338. DOI: 10.1063/1.350710.

[25] [25] ZHANG X C, AUSTON D H. Optically induced THz electromagnetic radiation from planar photoconducting structures[J]. Journal of Electromagnetic Waves and Applications, 1992, 6(1/4): 85-106. DOI: 10.1163/156939392X01039.

[26] [26] JEPSEN P U, JACOBSEN R H, KEIDING S R. Generation and detection of terahertz pulses from biased semiconductor antennas[J]. Journal of the Optical Society of America B, 1996, 13(11): 2424-2436. DOI: 10.1364/JOSAB.13.002424.

[27] [27] SHEN Y C, UPADHYA P C, LINFIELD E H, et al. Ultrabroadband terahertz radiation from low-temperature-grown GaAs photoconductive emitters[J]. Applied Physics Letters, 2003, 83(15): 3117-3119. DOI: 10.1063/1.1619223.

[28] [28] SCHNEIDER A, NEIS M, STILLHART M, et al. Generation of terahertz pulses through optical rectification in organic DAST crystals: theory and experiment[J]. Journal of the Optical Society of America B, 2006, 23(9): 1822-1835. DOI: 10.1364/JOSAB.23.001822.

[29] [29] YEH K L, HOFFMANN M C, HEBLING J, et al. Generation of 10 J ultrashort terahertz pulses by optical rectification[J]. Applied Physics Letters, 2007, 90(17): 171121. DOI: 10.1063/1.2734374.

[30] [30] HAURI C P, RUCHERT C, VICARIO C, et al. Strong-field single-cycle THz pulses generated in an organic crystal[J]. Applied Physics Letters, 2011, 99(16): 161116. DOI: 10.1063/1.3655331.

[31] [31] VICARIO C, JAZBINSEK M, OVCHINNIKOV A V, et al. High efficiency THz generation in DSTMS, DAST and OH1 pumped by Cr: forsterite laser[J]. Optics Express, 2015, 23(4): 4573-4580. DOI: 10.1364/OE.23.004573.

[32] [32] D'ARCO A, TOMARCHIO L, DOLCI V, et al. Broadband anisotropic optical properties of the terahertz generator HMQ-TMS organic crystal[J]. Condensed Matter, 2020, 5(3): 47. DOI: 10.3390/condmat5030047.

[33] [33] KRESS M, LFFLER T, EDEN S, et al. Terahertz-pulse generation by photoionization of air with laser pulses composed of both fundamental and second-harmonic waves[J]. Optics Letters, 2004, 29(10): 1120-1122. DOI: 10.1364/OL.29.001120.

[34] [34] ROEHLE H, DIETZ R J B, HENSEL H J, et al. Next generation 1.5 microm terahertz antennas: mesa-structuring of InGaAs/InAlAs photoconductive layers[J]. Optics Express, 2010, 18(3): 2296-2301. DOI: 10.1364/OE.18.002296.

[35] [35] DIETZ R J B, BRAHM A, VELAUTHAPILLAI A, et al. Low temperature grown photoconductive antennas for pulsed 1 060 nm excitation: influence of excess energy on the electron relaxation[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2015, 36(1): 60-71. DOI: 10.1007/s10762-014-0119-3.

[36] [36] PAEBUTAS V, BII，NA A, BERTULIS K, et al. Optoelectronic terahertz radiation system based on femtosecond 1 m laser pulses and GaBiAs detector[J]. Electronics Letters, 2008, 44(19): 1154-1155. DOI: 10.1049/el:20081630.

[37] [37] PAEBUTAS V, BIINAS A, BALAKAUSKAS S, et al. Terahertz time-domain-spectroscopy system based on femtosecond Yb: fiber laser and GaBiAs photoconducting components[J]. Applied Physics Letters, 2010, 97(3): 031111. DOI: 10.1063/1.3458826.

[38] [38] KOHLHAAS R B, BREUER S, LIEBERMEISTER L, et al. Novel photoconductive antennas based on rhodium doped InGaAs with 637 W emitted THz power[C]//Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XIV. Bellingham: SPIE, 2021: 11685. DOI: 10.1117/12.2582964.

[39] [39] NIKOO M S, JAFARI A, PERERA N, et al. Nanoplasma-enabled picosecond switches for ultrafast electronics[J]. Nature, 2020, 579(7800): 534-539. DOI: 10.1038/s41586-020-2118-y.

[40] [40] PAEBUTAS V, STANIONYT S, NORKUS R, et al. Terahertz pulse emission from GaInAsBi[J]. Journal of Applied Physics, 2019, 125(17): 174507. DOI: 10.1063/1.5089855.

[41] [41] KLEINE-OSTMANN T, KNOBLOCH P, KOCH M, et al. Continuous-wave THz imaging[J]. Electronics Letters, 2001, 37(24): 1167-1462. DOI: 10.1049/el:20011003.

[42] [42] QIN Hua, LI Xiang, SUN Jiandong, et al. Detection of incoherent terahertz light using antenna-coupled high-electron-mobility field-effect transistors[J]. Applied Physics Letters, 2017, 110(17): 171109. DOI: 10.1063/1.4982604.

[43] [43] SHI Jia, WANG Yuye, XU Degang, et al. Terahertz imaging based on morphological reconstruction[J]. IEEE Journal of Selected Topics in Quantum Electronics, 2017, 23(4): 1-7. DOI: 10.1109/JSTQE.2017.2649461.

[44] [44] YANG Xiang, SHI Jia, WANG Yuye, et al. Label-free bacterial colony detection and viability assessment by continuous-wave terahertz transmission imaging[J]. Journal of Biophotonics, 2018, 11(8): e201700386. DOI: 10.1002/jbio.201700386.

[45] [45] OK G, PARK K, KIM H J, et al. High-speed terahertz imaging toward food quality inspection[J]. Applied Optics, 2014, 53(7): 1406-1412. DOI: 10.1364/AO.53.001406.

[46] [46] WANG Yuye, SUN Zhongcheng, XU Degang, et al. A hybrid method based region of interest segmentation for continuous wave terahertz imaging[J]. Journal of Physics D: Applied Physics, 2019, 53(9): 095403. DOI: 10.1088/1361-6463/ab58b6.

[47] [47] SALHI M A, PUPEZA I, KOCH M. Confocal THz laser microscope[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2010, 31(3): 358-366. DOI: 10.1007/s10762-009-9590-7.

[48] [48] KIM G J, KIM J I, JEON S G, et al. Enhanced continuous-wave terahertz imaging with a horn antenna for food inspection[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2012, 33(6): 657-664. DOI: 10.1007/s10762-012-9902-1.

[49] [49] DE CUMIS U S, XU J H, MASINI L, et al. Terahertz confocal microscopy with a quantum cascade laser source[J]. Optics Express, 2012, 20(20): 21924-21931. DOI: 10.1364/OE.20.021924.

[50] [50] MAESTRINI A, THOMAS B, WANG H, et al. Schottky diode-based terahertz frequency multipliers and mixers[J]. Comptes Rendus Physique, 2010, 11(7-8): 480-495. DOI: 10.1016/j.crhy.2010.05.002.

[51] [51] DOBROIU A, YAMASHITA M, OHSHIMA Y N, et al. Terahertz imaging system based on a backward-wave oscillator[J]. Applied Optics, 2004, 43(30): 5637-5646. DOI: 10.1364/AO.43.005637.

[52] [52] MINEO M, PAOLONI C. Corrugated rectangular waveguide tunable backward wave oscillator for terahertz applications[J]. IEEE Transactions on Electron Devices, 2010, 57(6): 1481-1484. DOI: 10.1109/TED.2010.2045678.

[53] [53] HE W, ZHANG L, BOWES D, et al. Generation of broadband terahertz radiation using a backward wave oscillator and pseudospark-sourced electron beam[J]. Applied Physics Letters, 2015, 107(13): 133501. DOI: 10.1063/1.4932099.

[54] [54] KHLER R, TREDICUCCI A, BELTRAM F, et al. Terahertz semiconductor-heterostructure laser[J]. Nature, 2002, 417(6885): 156-159. DOI: 10.1038/417156a.

[55] [55] BOSCO L, FRANCKI M, SCALARI G, et al. Thermoelectrically cooled THz quantum cascade laser operating up to 210 K[J]. Applied Physics Letters, 2019, 115(1): 010601. DOI: 10.1063/1.5110305.

[56] [56] KHALATPOUR A, PAULSEN A K, DEIMERT C, et al. High-power portable terahertz laser systems[J]. Nature Photonics, 2021, 15(1): 16-20. DOI: 10.1038/s41566-020-00707-5.

[57] [57] KHALATPOUR A, TAM M C, ADDAMANE S J, et al. Enhanced operating temperature in terahertz quantum cascade lasers based on direct phonon depopulation[J]. Applied Physics Letters, 2023, 122(16): 161101. DOI: 10.1063/5.0144705.

[58] [58] BELKIN M A, CAPASSO F, BELYANIN A, et al. Terahertz quantum-cascade-laser source based on intracavity difference-frequency generation[J]. Nature Photonics, 2007, 1(5): 288-292. DOI: 10.1038/nphoton.2007.70.

[59] [59] LU Q Y, SLIVKEN S, BANDYOPADHYAY N, et al. Widely tunable room temperature semiconductor terahertz source[J]. Applied Physics Letters, 2014, 105(20): 4902245. DOI: 10.1063/1.4902245.

[60] [60] LU Q Y, BANDYOPADHYAY N, SLIVKEN S, et al. Continuous operation of a monolithic semiconductor terahertz source at room temperature[J]. Applied Physics Letters, 2014, 104(22): 221105. DOI: 10.1063/1.4881182.

[61] [61] KIM J H, JUNG S, JIANG Y F, et al. Double-metal waveguide terahertz difference-frequency generation quantum cascade lasers with surface grating outcouplers[J]. Applied Physics Letters, 2018, 113(16): 161102. DOI: 10.1063/1.5043095.

[62] [62] DARMO J, TAMOSIUNAS V, FASCHING G, et al. Imaging with a terahertz quantum cascade laser[J]. Optics Express, 2004, 12(9): 1879-1884. DOI: 10.1364/OPEX.12.001879.

[63] [63] NGUYEN K L, JOHNS M L, GLADDEN L, et al. Three-dimensional imaging with a terahertz quantum cascade laser[J]. Optics Express, 2006, 14(6): 2123-2129. DOI: 10.1364/OE.14.002123.

[64] [64] DEAN P, SHAUKAT M U, KHANNA S P, et al. Absorption-sensitive diffuse reflection imaging of concealed powders using a terahertz quantum cascade laser[J]. Optics Express, 2008, 16(9): 5997-6007. DOI: 10.1364/OE.16.005997.

[65] [65] RAVARO M, LOCATELLI M, VITI L, et al. Detection of a 2.8 THz quantum cascade laser with a semiconductor nanowire field-effect transistor coupled to a bow-tie antenna[J]. Applied Physics Letters, 2014, 104(8): 083116. DOI: 10.1063/1.4867074.

[66] [66] RAVARO M, JAGTAP V, SANTARELLI G, et al. Continuous-wave coherent imaging with terahertz quantum cascade lasers using electro-optic harmonic sampling[J]. Applied Physics Letters, 2013, 102(9): 091107. DOI: 10.1063/1.4793424.

[67] [67] DEAN P, VALAVANIS A, KEELEY J, et al. Coherent three-dimensional terahertz imaging through self-mixing in a quantum cascade laser[J]. Applied Physics Letters, 2013, 103(18): 181112. DOI: 10.1063/1.4827886.

[68] [68] VALAVANIS A, DEAN P, LIM Y L, et al. Self-mixing interferometry with terahertz quantum cascade lasers[J]. IEEE Sensors Journal, 2013, 13(1): 37-43. DOI: 10.1109/JSEN.2012.2218594.

[69] [69] ZHOU Zhitao, ZHOU Tao, ZHANG Shaoqing, et al. Multicolor T-ray imaging using multispectral metamaterials[J]. Advanced Science (Weinheim, Baden-Wrttemberg, Germany), 2018, 5(7): 1700982. DOI: 10.1002/advs.201700982.

[70] [70] DESTIC F, PETITJEAN Y, MASSENOT S, et al. THz QCL-based active imaging applied to composite materials diagnostic[C]//The 35th International Conference on Infrared, Millimeter, and Terahertz Waves. Rome, Italy: IEEE, 2010: 1-2. DOI: 10.1109/ICIMW.2010.5612792.

[71] [71] BROWN E R, SOLLNER T C L G, PARKER C D, et al. Oscillations up to 420 GHz in GaAs/AlAs resonant tunneling diodes[J]. Applied Physics Letters, 1989, 55(17): 1777-1779. DOI: 10.1063/1.102190.

[72] [72] BROWN E R, SDERSTRM J R, PARKER C D, et al. Oscillations up to 712 GHz in InAs/AlSb resonant-tunneling diodes[J]. Applied Physics Letters, 1991, 58(20): 2291-2293. DOI: 10.1063/1.104902.

[73] [73] RODWELL M J W, ALLEN S T, YU R Y, et al. Active and nonlinear wave propagation devices in ultrafast electronics and optoelectronics[J]. Proceedings of the IEEE, 1994, 82(7): 1037-1059. DOI: 10.1109/5.293161.

[74] [74] SUZUKI S, ASADA M, TERANISHI A, et al. Fundamental oscillation of resonant tunneling diodes above 1 THz at room temperature[J]. Applied Physics Letters, 2010, 97(24): 242102. DOI: 10.1063/1.3525834.

[75] [75] FEIGINOV M, SYDLO C, COJOCARI O, et al. Resonant-tunnelling-diode oscillators operating at frequencies above 1.1 THz[J]. Applied Physics Letters, 2011, 99(23): 233506. DOI: 10.1063/1.3667191.

[76] [76] FEIGINOV M N. Displacement currents and the real part of high-frequency conductance of the resonant-tunneling diode[J]. Applied Physics Letters, 2001, 78(21): 3301-3303. DOI: 10.1063/1.1372357.

[77] [77] IZUMI R, SUZUKI S, ASADA M. 1.98 THz resonant-tunneling-diode oscillator with reduced conduction loss by thick antenna electrode[C]//2017 the 42nd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz). Cancun, Mexico: IEEE, 2017: 1-2. DOI: 10.1109/IRMMW-THz.2017.8066877.

[78] [78] MAEKAWA T, KANAYA H, SUZUKI S, et al. Oscillation up to 1.92 THz in resonant tunneling diode by reduced conduction loss[J]. Applied Physics Express, 2016, 9(2): 024101. DOI: 10.7567/APEX.9.024101.

[79] [79] MIYAMOTO T, YAMAGUCHI A, MUKAI T. Terahertz imaging system with resonant tunneling diodes[J]. Japanese Journal of Applied Physics, 2016, 55(3): 032201. DOI: 10.7567/JJAP.55.032201.

[80] [80] LI Y, KANAME R, NISHIDA Y, et al. Imaging applications with a single resonant tunneling diode transceiver in 300 GHz band[C]//2020 International Topical Meeting on Microwave Photonics (MWP). Matsue, Japan: IEEE, 2020: 120-123. DOI: 10.23919/MWP48676.2020.9314482.

[81] [81] BROWN E R, MCINTOSH K A, NICHOLS K B, et al. Photomixing up to 3.8 THz in low-temperature-grown GaAs[J]. Applied Physics Letters, 1995, 66(3): 285-287. DOI: 10.1063/1.113519.

[82] [82] SONG H J, SHIMIZU N, FURUTA T, et al. Broadband-frequency-tunable sub-terahertz wave generation using an optical comb, AWGs, optical switches, and a uni-traveling carrier photodiode for spectroscopic applications[J]. Journal of Lightwave Technology, 2008, 26(15): 2521-2530. DOI: 10.1109/JLT.2008.927170.

[83] [83] ROUVALIS E, RENAUD C C, MOODIE D G, et al. Traveling-wave uni-traveling carrier photodiodes for continuous wave THz generation[J]. Optics Express, 2010, 18(11): 11105-11110. DOI: 10.1364/OE.18.011105.

[84] [84] PREU S, RENNER F H, MALZER S, et al. Efficient terahertz emission from ballistic transport enhanced nipnip superlattice photomixers[J]. Applied Physics Letters, 2007, 90(21): 212125. DOI: 10.1063/1.2743400.

[85] [85] ITO H, NAKAJIMA F, FURUTA T, et al. Continuous THz-wave generation using antenna-integrated uni-travelling-carrier photodiodes[J]. Semiconductor Science and Technology, 2005, 20(7): S191. DOI: 10.1088/0268-1242/20/7/008.

[86] [86] NELLEN S, ISHIBASHI T, DENINGER A, et al. Experimental comparison of UTC-and pin-photodiodes for continuous-wave terahertz generation[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2020, 41(4): 343-354. DOI: 10.1007/s10762-019-00638-5.

[87] [87] DING Yujie. Progress in terahertz sources based on difference-frequency generation[Invited][J]. Journal of the Optical Society of America B, 2014, 31(11): 2696-2711. DOI: 10.1364/JOSAB.31.002696.

[88] [88] SAFIAN R, GHAZI G, MOHAMMADIAN N. Review of photomixing continuous-wave terahertz systems and current application trends in terahertz domain[J]. Optical Engineering, 2019, 58(11): 110901. DOI: 10.1117/1.OE.58.11.110901.

[89] [89] VERGHESE S, MCINTOSH K A, CALAWA S, et al. Generation and detection of coherent terahertz waves using two photomixers[J]. Applied Physics Letters, 1998, 73(26): 3824-3826. DOI: 10.1063/1.122906.

[90] [90] MATSUURA S, BLAKE G A, WYSS R A, et al. A traveling-wave THz photomixer based on angle-tuned phase matching[J]. Applied Physics Letters, 1999, 74(19): 2872-2874. DOI: 10.1063/1.124042.

[91] [91] YAHYAPOUR M, VIEWEG N, ROGGENBUCK A, et al. A flexible phase-insensitive system for broadband CW-terahertz spectroscopy and imaging[J]. IEEE Transactions on Terahertz Science and Technology, 2016, 6(5): 670-673. DOI: 10.1109/TTHZ.2016.2589540.

[92] [92] SIEBERT K J, QUAST H, LEONHARDT R, et al. Continuous-wave all-optoelectronic terahertz imaging[J]. Applied Physics Letters, 2002, 80(16): 3003-3005. DOI: 10.1063/1.1469679.

[93] [93] KIM J Y, SONG H J, AJITO K, et al. Continuous-wave THz homodyne spectroscopy and imaging system with electro-optical phase modulation for high dynamic range[J]. IEEE Transactions on Terahertz Science and Technology, 2013, 3(2): 158-164. DOI: 10.1109/TTHZ.2012.2228896.

[94] [94] MOON K, KIM N, SHIN J H, et al. Continuous-wave terahertz system based on a dual-mode laser for real-time non-contact measurement of thickness and conductivity[J]. Optics Express, 2014, 22(3): 2259-2266. DOI: 10.1364/OE.22.002259.

[95] [95] SONG H, HWANG S, AN H, et al. Continuous-wave THz vector imaging system utilizing two-tone signal generation and self-mixing detection[J]. Optics Express, 2017, 25(17): 20718-20726. DOI: 10.1364/OE.25.020718.

[96] [96] DLME S, STEEG M, MOHAMMAD I, et al. Ultra-low phase-noise photonic terahertz imaging system based on two-tone square-law detection[J]. Optics Express, 2020, 28(20): 29631-29643. DOI: 10.1364/OE.400405.

[97] [97] YANG Zuomin, ZHANG Lu, LU Zijie, et al. Robust photonic terahertz vector imaging scheme using an optical frequency comb[J]. Journal of Lightwave Technology, 2022, 40(9): 2717-2723. DOI: 10.1109/JLT.2022.3146438.

[98] [98] LIEBERMEISTER L, NELLEN S, KOHLHAAS R B, et al. Optoelectronic frequency-modulated continuous-wave terahertz spectroscopy with 4 THz bandwidth[J]. Nature Communications, 2021, 12(1): 1071. DOI: 10.1038/s41467-021-21260-x.

[99] [99] KUTZ J, LIEBERMEISTER L, VIEWEG N, et al. A terahertz fast-sweep optoelectronic frequency-domain spectrometer: calibration, performance tests, and comparison with TDS and FDS[J]. Applied Sciences, 2022, 12(16): 8257. DOI: 10.3390/app12168257.

[100] [100] LIEBERMEISTER L, NELLEN S, KOHLHAAS R B, et al. Terahertz multilayer thickness measurements: comparison of optoelectronic time and frequency domain systems[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2021, 42(11): 1153-1167. DOI: 10.1007/s10762-021-00831-5.

[101] [101] HUNSCHE S, KOCH M, BRENER I, et al. THz near-field imaging[J]. Optics Communications, 1998, 150(1-6): 22-26. DOI: 10.1016/S0030-4018(98)00044-3.

[102] [102] MITROFANOV O, BRENER I, HAREL R, et al. Terahertz near-field microscopy based on a collection mode detector[J]. Applied Physics Letters, 2000, 77(22): 3496-3498. DOI: 10.1063/1.1328772.

[103] [103] KAWANO Y, ISHIBASHI K. An on-chip near-field terahertz probe and detector[J]. Nature Photonics, 2008, 2(10): 618-621. DOI: 10.1038/nphoton.2008.157.

[104] [104] MACFADEN A J, RENO J L, BRENER I, et al. 3 m aperture probes for near-field terahertz transmission microscopy[J]. Applied Physics Letters, 2014, 104(1): 011110. DOI: 10.1063/1.4861621.

[105] [105] CHEN Q, JIANG Z P, XU G X, et al. Near-field terahertz imaging with a dynamic aperture[J]. Optics Letters, 2000, 25(15): 1122-1124. DOI: 10.1364/OL.25.001122.

[106] [106] WANG Xinke, YE Jiasheng, SUN Wenfeng, et al. Terahertz near-field microscopy based on an air-plasma dynamic aperture[J]. Light, Science & Applications, 2022, 11(1): 129. DOI: 10.1038/s41377-022-00822-8.

[107] [107] VAN D V N C J. PLANKEN P C M. Electro-optic detection of subwavelength terahertz spot sizes in the near field of a metal tip[J]. Applied Physics Letters, 2002, 81(9): 1558-1560. DOI: 10.1063/1.1503404.

[108] [108] CHEN Houtong, KERSTING R, CHO G C. Terahertz imaging with nanometer resolution[J]. Applied Physics Letters, 2003, 83(15): 3009-3011. DOI: 10.1063/1.1616668.

[109] [109] COCKER T L, JELIC V, GUPTA M, et al. An ultrafast terahertz scanning tunnelling microscope[J]. Nature Photonics, 2013, 7(8): 620-625. DOI: 10.1038/nphoton.2013.151.

[110] [110] YOSHIDA S, ARASHIDA Y, HIRORI H, et al. Terahertz scanning tunneling microscopy for visualizing ultrafast electron motion in nanoscale potential variations[J]. ACS Photonics, 2021, 8(1): 315-323. DOI: 10.1021/acsphotonics.0c01572.

[111] [111] HUBER A J, KEILMANN F, WITTBORN J, et al. Terahertz near-field nanoscopy of mobile carriers in single semiconductor nanodevices[J]. Nano Letters, 2008, 8(11): 3766-3770. DOI: 10.1021/nl802086x.

[112] [112] MOON K, PARK H, KIM J, et al. Subsurface nanoimaging by broadband terahertz pulse near-field microscopy[J]. Nano Letters, 2015, 15(1): 549-552. DOI: 10.1021/nl503998v.

[113] [113] PENDRY J B. Negative refraction makes a perfect lens[J]. Physical Review Letters, 2000, 85(18): 3966-3969. DOI: 10.1103/PhysRevLett.85.3966.

[114] [114] GRBIC A, ELEFTHERIADES G V. Overcoming the diffraction limit with a planar left-handed transmission-line lens[J]. Physical Review Letters, 2004, 92(11): 117403. DOI: 10.1103/PhysRevLett.92.117403.

[115] [115] BELOV P A, SIMOVSKI C R, IKONEN P. Canalization of subwavelength images by electromagnetic crystals[J]. Physical Review B, Condensed Matter and Materials Physics, 2005, 71(19): 193105. DOI: 10.1103/PhysRevB.71.193105.

[116] [116] JUNG J, GARCIA-VIDAL F J, MARTIN-MORENO L, et al. Holey metal films make perfect endoscopes[J]. Physical Review B, Condensed Matter and Materials Physics, 2009, 79(15): 153407. DOI: 10.1103/PhysRevB.79.153407.

[117] [117] HUANG Tiejun, TANG Henghe, TAN Yunhua, et al. Terahertz super-resolution imaging based on subwavelength metallic grating[J]. IEEE Transactions on Antennas and Propagation, 2019, 67(5): 3358-3365. DOI: 10.1109/TAP.2019.2894260.

[118] [118] TUNIZ A, KALTENECKER K J, FISCHER B M, et al. Metamaterial fibres for subdiffraction imaging and focusing at terahertz frequencies over optically long distances[J]. Nature Communications, 2013, 4(1): 2706. DOI: 10.1038/ncomms3706.

[119] [119] ANDRYIEUSKI A, LAVRINENKO A V, CHIGRIN D N. Graphene hyperlens for terahertz radiation[J]. Physical Review B, Condensed Matter and Materials Physics, 2012, 86(12): 121108. DOI: 10.1103/PhysRevB.86.121108.

[120] [120] TANG Henghe, LIU Pukun. Long-distance super-resolution imaging assisted by enhanced spatial Fourier transform[J]. Optics Express, 2015, 23(18): 23613-23623. DOI: 10.1364/OE.23.023613.

[121] [121] TANG Henghe, HUANG Tiejun, LIU Jiangyu, et al. Tunable terahertz deep subwavelength imaging based on a graphene monolayer[J]. Scientific Reports, 2017, 7(1): 46283. DOI: 10.1038/srep46283.

[122] [122] JIANG Xue, CHEN Hao, LI Zeyu, et al. All-dielectric metalens for terahertz wave imaging[J]. Optics Express, 2018, 26(11): 14132-14142. DOI: 10.1364/OE.26.014132.

[123] [123] LI Xurong, LI Jiangxi, LI Yuhang, et al. High-throughput terahertz imaging: progress and challenges[J]. Light, Science & Applications, 2023, 12(1): 233. DOI: 10.1038/s41377-023-01278-0.

[124] [124] LEE A W M, HU Q. Real-time, continuous-wave terahertz imaging by use of a microbolometer focal-plane array[J]. Optics Letters, 2005, 30(19): 2563-2565. DOI: 10.1364/OL.30.002563.

[125] [125] LEE A W M, WILLIAMS B S, KUMAR S, et al. Real-time imaging using a 4.3 THz quantum cascade laser and a 320/spl times/240 microbolometer focal-plane array[J]. IEEE Photonics Technology Letters, 2006, 18(13): 1415-1417. DOI: 10.1109/LPT.2006.877220.

[126] [126] BEHNKEN B N, KARUNASIRI G, CHAMBERLIN D R, et al. Real-time imaging using a 2.8 THz quantum cascade laser and uncooled infrared microbolometer camera[J]. Optics Letters, 2008, 33(5): 440-442. DOI: 10.1364/OL.33.000440.

[127] [127] DEM'YANENKO M A, ESAEV D G, KNYAZEV B A, et al. Imaging with a 90 frames∕s microbolometer focal plane array and high-power terahertz free electron laser[J]. Applied Physics Letters, 2008, 92(13): 131116. DOI: 10.1063/1.2898138.

[128] [128] ODA N, KURASHINA S, MIYOSHI M, et al. Microbolometer terahertz focal plane array and camera with improved sensitivity in the sub-terahertz region[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2015, 36(10): 947-960. DOI: 10.1007/s10762-015-0184-2.

[129] [129] NEMOTO N, KANDA N, IMAI R, et al. High-sensitivity and broadband, real-time terahertz camera incorporating a micro-bolometer array with resonant cavity structure[J]. IEEE Transactions on Terahertz Science and Technology, 2016, 6(2): 175-182. DOI: 10.1109/TTHZ.2015.2508010.

[130] [130] LUOMAHAARA J, SIPOLA H, GRNBERG L, et al. A passive, fully staring THz video camera based on kinetic inductance bolometer arrays[J]. IEEE Transactions on Terahertz Science and Technology, 2021, 11(1): 101-108. DOI: 10.1109/TTHZ.2020.3029949.

[131] [131] SEEK A, KAALYNAS I, EMVA A, et al. Antenna-coupled Ti-microbolometers for high-sensitivity terahertz imaging[J]. Sensors and Actuators A: Physical, 2017(268): 133-140. DOI: 10.1016/j.sna.2017.11.029.

[132] [132] BLANCHARD F, NKECK J E, MATTE D, et al. A low-cost terahertz camera[J]. Applied Sciences, 2019, 9(12): 2531. DOI: 10.3390/app9122531.

[133] [133] LEE Y S. Continuous-wave terahertz sources and detectors[M]//LEE Y S. Principles of Terahertz Science and Technology. Boston, MA US: Springer, 2009: 1-41. DOI: 10.1007/978-0-387-09540-0_4.

[134] [134] YANG Jun, RUAN Shuangchen, ZHANG Min. Real-time, continuous-wave terahertz imaging by a pyroelectric camera[J]. Chinese Optics Letters, 2008, 6(1): 29-31.

[135] [135] LI Qi, DING Shenghui, YAO Rui, et al. Real-time terahertz scanning imaging by use of a pyroelectric array camera and image denoising[J]. Journal of the Optical Society of America. A, Optics, Image Science, and Vision, 2010, 27(11): 2381-2386. DOI: 10.1364/JOSAA.27.002381.

[136] [136] DING Shenghui, LI Qi, LI Yunda, et al. Continuous-wave terahertz digital holography by use of a pyroelectric array camera[J]. Optics Letters, 2011, 36(11): 1993-1995. DOI: 10.1364/OL.36.001993.

[137] [137] HUANG H C, QIU P Y, PANEZAI S, et al. Continuous-wave terahertz high-resolution imaging via synthetic hologram extrapolation method using pyroelectric detector[J]. Optics & Laser Technology, 2019, 120: 105683. DOI: 10.1016/j.optlastec.2019.105683.

[138] [138] DYAKONOV M, SHUR M. Detection, mixing, and frequency multiplication of terahertz radiation by two-dimensional electronic fluid[J]. IEEE Transactions on Electron Devices, 1996, 43(3): 380-387. DOI: 10.1109/16.485650.

[139] [139] KNAP W, DENG Y, RUMYANTSEV S, et al. Resonant detection of sub-terahertz and terahertz radiation by plasma waves in submicron field-effect transistors[J]. Applied Physics Letters, 2002, 81(24): 4637-4639. DOI: 10.1063/1.1525851.

[140] [140] KNAP W, KACHOROVSKII V, DENG Y, et al. Nonresonant detection of terahertz radiation in field effect transistors[J]. Journal of Applied Physics, 2002, 91(11): 9346-9353. DOI: 10.1063/1.1468257.

[141] [141] AL HADI R, SHERRY H, GRZYB J, et al. A 1 k-pixel video camera for 0.7～1.1 terahertz imaging applications in 65 nm CMOS[J]. IEEE Journal of Solid-State Circuits, 2012, 47(12): 2999-3012. DOI: 10.1109/JSSC.2012.2217851.

[142] [142] YOKOYAMA S, IKEBE M, KANAZAWA Y, et al. 5.8 A 32×32-pixel 0.9 THz imager with pixel-parallel 12b VCO-based ADC in 0.18 m CMOS[C]//2019 IEEE International Solid-State Circuits Conference (ISSCC). San Francisco, CA, USA: IEEE, 2019: 108-110. DOI: 10.1109/ISSCC.2019.8662483.

[143] [143] JAIN R, HILLGER P, GRZYB J, et al. 34.3 A 32×32 pixel 0.46-to-0.75 THz light-field camera SoC in 0.13 m CMOS[C]//2021 IEEE International Solid-State Circuits Conference (ISSCC). San Francisco, CA, USA: IEEE, 2021: 484-486. DOI: 10.1109/ISSCC42613.2021.9365832.

[144] [144] LIU Min, CAI Ziteng, ZHOU Shaohua, et al. A 16.4k pixel 3.08-to-3.86 THz digital real-time CMOS image sensor with 73 dB dynamic range[C]//2023 IEEE International Solid-State Circuits Conference (ISSCC). San Francisco, CA, USA: IEEE, 2023: 4-6. DOI: 10.1109/ISSCC42615.2023.10067620.

[145] [145] ALVES F, KEARNEY B, GRBOVIC D, et al. Strong terahertz absorption using SiO2/Al based metamaterial structures[J]. Applied Physics Letters, 2012, 100(11): 111104. DOI: 10.1063/1.3693407.

[146] [146] KEARNEY B, ALVES F, GRBOVIC D, et al. Al/SiOx/Al single and multiband metamaterial absorbers for terahertz sensor applications[J]. Optical Engineering, 2013, 52(1): 013801. DOI: 10.1117/1.OE.52.1.013801.

[147] [147] WITHAYACHUMNANKUL W, SHAH C M, FUMEAUX C, et al. Plasmonic resonance toward terahertz perfect absorbers[J]. ACS Photonics, 2014, 1(7): 625-630. DOI: 10.1021/ph500110t.

[148] [148] FAN K B, SUEN J Y, LIU X Y, et al. All-dielectric metasurface absorbers for uncooled terahertz imaging[J]. Optica, 2017, 4(6): 601-604. DOI: 10.1364/OPTICA.4.000601.

[149] [149] BROMBERG Y, KATZ O, SILBERBERG Y. Ghost imaging with a single detector[J]. Physical Review A―Atomic, Molecular, and Optical Physics, 2009, 79(5): 053840. DOI: 10.1103/PhysRevA.79.053840.

[150] [150] ZHANG Zibang, MA Xiao, ZHONG Jingang. Single-pixel imaging by means of Fourier spectrum acquisition[J]. Nature Communications, 2015(6): 6225. DOI: 10.1038/ncomms7225.

[151] [151] SUN M J, MENG L T, EDGAR M P, et al. A Russian dolls ordering of the Hadamard basis for compressive single-pixel imaging[J]. Scientific Reports, 2017, 7(1): 3464. DOI: 10.1038/s41598-017-03725-6.

[152] [152] GEADAH, CORINTHIOS. Natural, dyadic, and sequence order algorithms and processors for the Walsh-Hadamard transform[J]. IEEE Transactions on Computers, 1977, C-26(5): 435-442. DOI: 10.1109/TC.1977.1674860.

[153] [153] YU Wenkai. Super sub-Nyquist single-pixel imaging by means of cake-cutting Hadamard basis sort[J]. Sensors, 2019, 19(19): 4122. DOI: 10.3390/s19194122.

[154] [154] CHAN W L, CHARAN K, TAKHAR D, et al. A single-pixel terahertz imaging system based on compressed sensing[J]. Applied Physics Letters, 2008, 93(12): 121105. DOI: 10.1063/1.2989126.

[155] [155] SHEN H, GAN L, NEWMAN N, et al. Spinning disk for compressive imaging[J]. Optics Letters, 2012, 37(1): 46-48. DOI: 10.1364/OL.37.000046.

[156] [156] DUAN Pan, WANG Yuye, XU Degang, et al. Single pixel imaging with tunable terahertz parametric oscillator[J]. Applied Optics, 2016, 55(13): 3670-3675. DOI: 10.1364/AO.55.003670.

[157] [157] STANTCHEV R I, SUN B Q, HORNETT S M, et al. Noninvasive, near-field terahertz imaging of hidden objects using a single-pixel detector[J]. Science Advances, 2016, 2(6): e1600190. DOI: 10.1126/sciadv.1600190.

[158] [158] SHREKENHAMER D, WATTS C M, PADILLA W J. Terahertz single pixel imaging with an optically controlled dynamic spatial light modulator[J]. Optics Express, 2013, 21(10): 12507-12518. DOI: 10.1364/OE.21.012507.

[159] [159] AUGUSTIN S, HIERONYMUS J, JUNG P, et al. Compressed sensing in a fully non-mechanical 350 GHz imaging setting[J]. Journal of Infrared, Millimeter, and Terahertz Waves, 2015, 36(5): 496-512. DOI: 10.1007/s10762-014-0141-5.

[160] [160] SHANG Yingjie, WANG Xinke, SUN Wenfeng, et al. Terahertz image reconstruction based on compressed sensing and inverse Fresnel diffraction[J]. Optics Express, 2019, 27(10): 14725-14735. DOI: 10.1364/OE.27.014725.

[161] [161] STANTCHEV R I, YU Xiao, BLU T, et al. Real-time terahertz imaging with a single-pixel detector[J]. Nature Communications, 2020, 11(1): 2535. DOI: 10.1038/s41467-020-16370-x.

[162] [162] LI Tianyu, FANG Xing, ZHANG Lu, et al. Photonic continuous-wave single-pixel terahertz imaging based on compressive sensing[C]//2024 Asia Communications and Photonics Conference (ACP) and International Conference on Information Photonics and Optical Communications (IPOC). Beijing, China: IEEE, 2024: 1-3. DOI: 10.1109/ACP/IPOC63121.2024.10810027.

[163] [163] WATTS C M, SHREKENHAMER D, MONTOYA J, et al. Terahertz compressive imaging with metamaterial spatial light modulators[J]. Nature Photonics, 2014, 8(8): 605-609. DOI: 10.1038/nphoton.2014.139.

[164] [164] LI Weili, HU Xuemei, WU Jingbo, et al. Dual-color terahertz spatial light modulator for single-pixel imaging[J]. Light: Science & Applications, 2022, 11(1): 191. DOI: 10.1038/s41377-022-00879-5.

[165] [165] SAQUEB S A N, SERTEL K. Phase-sensitive single-pixel THz imaging using intensity-only measurements[J]. IEEE Transactions on Terahertz Science and Technology, 2016, 6(6): 810-816. DOI: 10.1109/TTHZ.2016.2610760.

[166] [166] SHEN Y, GAN L, STRINGER M, et al. Terahertz pulsed spectroscopic imaging using optimized binary masks[J]. Applied Physics Letters, 2009, 95(23): 231112. DOI: 10.1063/1.3271030.

[167] [167] ZANOTTO L, PICCOLI R, DONG J, et al. Time-domain terahertz compressive imaging[J]. Optics Express, 2020, 28(3): 3795-3802. DOI: 10.1364/OE.384134.

[168] [168] STANTCHEV R I, PHILLIPS D B, HOBSON P, et al. Compressed sensing with near-field THz radiation[J]. Optica, 2017, 4(8): 989-992. DOI: 10.1364/OPTICA.4.000989.

[169] [169] CHEN Sichao, DU Lianghui, MENG Kun, et al. Terahertz wave near-field compressive imaging with a spatial resolution of over /100[J]. Optics Letters, 2019, 44(1): 21-24. DOI: 10.1364/OL.44.000021.

[170] [170] HORNETT S M, STANTCHEV R I, VARDAKI M Z, et al. Subwavelength terahertz imaging of graphene photoconductivity[J]. Nano Letters, 2016, 16(11): 7019-7024. DOI: 10.1021/acs.nanolett.6b03168.

[171] [171] MOHR T, HERDT A, ELSSSER W. 2D tomographic terahertz imaging using a single pixel detector[J]. Optics Express, 2018, 26(3): 3353-3367. DOI: 10.1364/OE.26.003353.

[172] [172] SAQUEB S A N, SERTEL K. Multisensor compressive sensing for high frame-rate imaging system in the THz band[J]. IEEE Transactions on Terahertz Science and Technology, 2019, 9(5): 520-523. DOI: 10.1109/TTHZ.2019.2926618.

[173] [173] KANNEGULLA A, SHAMS M I B, LIU L, et al. Photo-induced spatial modulation of THz waves: opportunities and limitations[J]. Optics Express, 2015, 23(25): 32098-32112. DOI: 10.1364/OE.23.032098.

[174] [174] ZANOTTO L, PICCOLI R, DONG Junliang, et al. Single-pixel terahertz imaging: a review[J]. Opto-Electronic Advances, 2020, 3(9): 09200012. DOI: 10.29026/oea.2020.200012.

[176] [176] LYU Meng, WANG Wei, WANG Hao, et al. Deep-learning-based ghost imaging[J]. Scientific Reports, 2017, 7(1): 17865. DOI: 10.1038/s41598-017-18171-7.

[177] [177] SHIMOBABA T, ENDO Y, NISHITSUJI T, et al. Computational ghost imaging using deep learning[J]. Optics Communications, 2018(413): 147-151. DOI: 10.1016/j.optcom.2017.12.041.

[178] [178] MITTLEMAN D M, HUNSCHE S, BOIVIN L, et al. T-ray tomography[J]. Optics Letters, 1997, 22(12): 904-906. DOI: 10.1364/OL.22.000904.

[179] [179] ZEITLER J A, TADAY P F, NEWNHAM D A, et al. Terahertz pulsed spectroscopy and imaging in the pharmaceutical setting: a review[J]. The Journal of Pharmacy and Pharmacology, 2007, 59(2): 209-223. DOI: 10.1211/jpp.59.2.0008.

[180] [180] FITZGERALD A J, COLE B E, TADAY P F. Nondestructive analysis of tablet coating thicknesses using terahertz pulsed imaging[J]. Journal of Pharmaceutical Sciences, 2005, 94(1): 177-183. DOI: 10.1002/jps.20225.

[181] [181] SHEN Yaochun. Terahertz pulsed spectroscopy and imaging for pharmaceutical applications: a review[J]. International Journal of Pharmaceutics, 2011, 417(1/2): 48-60. DOI: 10.1016/j.ijpharm.2011.01.012.

[182] [182] HAASER M, GORDON K C, STRACHAN C J, et al. Terahertz pulsed imaging as an advanced characterisation tool for film coatings: a review[J]. International Journal of Pharmaceutics, 2013, 457(2): 510-520. DOI: 10.1016/j.ijpharm.2013.03.053.

[183] [183] HO L, MLLER R, RMER M, et al. Analysis of sustained-release tablet film coats using terahertz pulsed imaging[J]. Journal of Controlled Release, 2007, 119(3): 253-261. DOI: 10.1016/j.jconrel.2007.03.011.

[184] [184] MAY R K, EVANS M J, ZHONG S C, et al. Terahertz in-line sensor for direct coating thickness measurement of individual tablets during film coating in real-time[J]. Journal of Pharmaceutical Sciences, 2011, 100(4): 1535-1544. DOI: 10.1002/jps.22359.

[185] [185] FUKUNAGA K, PICOLLO M. Terahertz spectroscopy applied to the analysis of artists' materials[J]. Applied Physics A, 2010, 100(3): 591-597. DOI: 10.1007/s00339-010-5643-y.

[186] [186] ABRAHAM E, FUKUNAGA K. Terahertz imaging applied to the examination of artistic objects[J]. Studies in Conservation, 2015, 60(6): 343-352. DOI: 10.1179/2047058414Y.0000000146.

[187] [187] SECO-MARTORELL C, LPEZ-DOMNGUEZ V, ARAUZ-GAROFALO G, et al. Goya's artwork imaging with terahertz waves[J]. Optics Express, 2013, 21(15): 17800-17805. DOI: 10.1364/OE.21.017800.

[188] [188] ADAM A J L, PLANKEN P C M, MELONI S, et al. Terahertz imaging of hidden paint layers on canvas[J]. Optics Express, 2009, 17(5): 3407-3416. DOI: 10.1364/OE.17.003407.

[189] [189] KOCH-DANDOLO C L, FILTENBORG T, FUKUNAGA K, et al. Reflection terahertz time-domain imaging for analysis of an 18th century neoclassical easel painting[J]. Applied Optics, 2015, 54(16): 5123-5129. DOI: 10.1364/AO.54.005123.

[190] [190] SU K, SHEN Y C, ZEITLER J A. Terahertz sensor for non-contact thickness and quality measurement of automobile paints of varying complexity[J]. IEEE Transactions on Terahertz Science and Technology, 2014, 4(4): 432-439. DOI: 10.1109/TTHZ.2014.2325393.

[191] [191] VAN MECHELEN J L M, FRANK A, MAAS D J H C. Thickness sensor for drying paints using THz spectroscopy[J]. Optics Express, 2021, 29(5): 7514-7525. DOI: 10.1364/OE.418809.

[192] [192] FERGUSON B, WANG S H, GRAY D, et al. T-ray computed tomography[J]. Optics Letters, 2002, 27(15): 1312-1314. DOI: 10.1364/OL.27.001312.

[193] [193] BRAHM A, KUNZ M, RIEHEMANN S, et al. Volumetric spectral analysis of materials using terahertz-tomography techniques[J]. Applied Physics B, 2010, 100(1): 151-158. DOI: 10.1007/s00340-010-3945-6.

[194] [194] BRAHM A, TYMOSHCHUK M, WICHMANN F, et al. Wavelet based identification of substances in terahertz tomography measurements[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2014, 35(11): 974-986. DOI: 10.1007/s10762-014-0106-8.

[195] [195] RECUR B, GUILLET J P, MANEK-HNNINGER I, et al. Propagation beam consideration for 3D THz computed tomography[J]. Optics Express, 2012, 20(6): 5817-5829. DOI: 10.1364/OE.20.005817.

[196] [196] RECUR B, BALACEY H, SLEIMAN J B, et al. Ordered subsets convex algorithm for 3D terahertz transmission tomography[J]. Optics Express, 2014, 22(19): 23299-23309. DOI: 10.1364/OE.22.023299.

[197] [197] BITMAN A, GOLDRING S, MOSHE I, et al. Computed tomography using broadband Bessel THz beams and phase contrast[J]. Optics Letters, 2014, 39(7): 1925-1928. DOI: 10.1364/OL.39.001925.

[198] [198] WANG Dayong, LI Bin, RONG Lu, et al. Extended depth of field in continuous-wave terahertz computed tomography based on Bessel beam[J]. Optics Communications, 2019(432): 20-26. DOI: 10.1016/j.optcom.2018.09.031.

[199] [199] SHEN Sishi, HAO Congjing, LIANG Bin, et al. Terahertz fan-beam computed tomography[J]. Optics Letters, 2024, 49(9): 2481-2484. DOI: 10.1364/OL.523116.

[200] [200] CHEN Linyu, WANG Yuye, XU Degang, et al. Terahertz computed tomography of high-refractive-index objects based on refractive index matching[J]. IEEE Photonics Journal, 2018, 10(6): 1-13. DOI: 10.1109/JPHOT.2018.2877657.

[201] [201] FOSODEDER P, HUBMER S, PLOIER A, et al. Phase-contrast THz-CT for non-destructive testing[J]. Optics Express, 2021, 29(10): 15711-15723. DOI: 10.1364/OE.422961.

[202] [202] FOSODEDER P, VAN FRANK S, RANKL C. Highly accurate THz-CT including refraction effects[J]. Optics Express, 2022, 30(3): 3684-3699. DOI: 10.1364/OE.444151.

[203] [203] DUHANT A, TRIKI M, STRAUSS O. Terahertz differential computed tomography: a relevant nondestructive inspection application[J]. Journal of Infrared, Millimeter and Terahertz Waves, 2019, 40(2): 178-199. DOI: 10.1007/s10762-018-0564-5.

[204] [204] WANG Dayong, NING Ran, LI Gaochao, et al. 3D image reconstruction of terahertz computed tomography at sparse angles by total variation minimization[J]. Applied Optics, 2022, 61(5): B1-B7. DOI: 10.1364/AO.440847.

[206] [206] LI Nan, ZHENG Shilie, HE Tong, et al. Metasurface-based dual-mode bright-field and spiral phase contrast THz imaging with enhanced focal depth[J]. Journal of Lightwave Technology, 2024, 43(9): 1-9. DOI: 10.1109/JLT.2024.3521973.