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Maussang K, Palomo J, Mangeney J, Dhillon SS, Tignon J. Large-area photoconductive switches as emitters of terahertz pulses with fully electrically controlled linear polarization. OPTICS EXPRESS 2019; 27:14784-14797. [PMID: 31163921 DOI: 10.1364/oe.27.014784] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 03/10/2019] [Indexed: 06/09/2023]
Abstract
Polarimetric measurements in the terahertz (THz) range have a wide range of applications in material science and physico-chemistry. Usually performed using mechanically controlled elements, such measurements are inherently limited in precision and acquisition rate. Here, we propose and realize an innovative concept of a THz pulse emitter, linearly polarized, which allows electrical continuous control of the polarization direction and modulation ability up to several tens of kHz. It consists in an interdigitated photoconductive switch with an intermixed sickle geometry, where the vertical and horizontal components of the electric field are intermixed at a subwavelength scale. We demonstrate that such an emitter permits control of the direction and amplitude emitted with an excellent degree of polarization up to 4 THz, which is estimated to be experimentally better than 98%. This work opens perspectives for sensitivity improvements in THz polarimetry with lock-in detection schemes.
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Wang Z, Kang K, Wang S, Li L, Xu N, Han J, He M, Wu L, Zhang W. Determination of plane stress state using terahertz time-domain spectroscopy. Sci Rep 2016; 6:36308. [PMID: 27824112 PMCID: PMC5099881 DOI: 10.1038/srep36308] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/13/2016] [Indexed: 11/09/2022] Open
Abstract
THz wave has been increasingly applied in engineering practice. One of its outstanding advantages is the penetrability through certain optically opaque materials, whose interior properties could be therefore obtained. In this report, we develop an experimental method to determine the plane stress state of optically opaque materials based on the stress-optical law using terahertz time-domain spectroscopy (THz-TDS). In this method, two polarizers are combined into the conventional THz-TDS system to sense and adjust the polarization state of THz waves and a theoretical model is established to describe the relationship between phase delay of the received THz wave and the plane stress applied on the specimen. Three stress parameters that represent the plane stress state are finally determined through an error function of THz wave phase-delay. Experiments were conducted on polytetrafluoroethylene (PTFE) specimen and a reasonably good agreement was found with measurement using traditional strain gauges. The presented results validate the effectiveness of the proposed method. The proposed method could be further used in nondestructive tests for a wide range of optically opaque materials.
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Affiliation(s)
- Zhiyong Wang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300072, China
| | - Kai Kang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300072, China
| | - Shibin Wang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300072, China
| | - Lin'an Li
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300072, China
| | - Ningning Xu
- School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma, 74078, USA
| | - Jiaguang Han
- Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China
| | - Mingxia He
- Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China
| | - Liang Wu
- Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China
| | - Weili Zhang
- School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma, 74078, USA.,Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China
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Schemmel P, Diederich G, Moore AJ. Direct stress optic coefficients for YTZP ceramic and PTFE at GHz frequencies. OPTICS EXPRESS 2016; 24:8110-8119. [PMID: 27137250 DOI: 10.1364/oe.24.008110] [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 report the first measurement of the direct stress optic coefficient for yttria-partially stabilized zirconia (YTZP) ceramic, using illumination between 260 and 380 GHz with applied stresses up to 27 MPa. YTZP exhibited a linear change in refractive index as a function of stress across the entire applied stress domain. A direct stress optic coefficient was also measured for polytetrafluoroethylene (PTFE). PTFE showed viscoelastic behavior at stress values above 4.5 MPa. These results open the way for quantitative sub-surface stress measurements in structural ceramics and ceramic coating systems at GHz and THz frequencies.
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Song W, Wang Z. Active modulation of refractive index by stress in the terahertz frequency range: erratum. APPLIED OPTICS 2016; 55:2223. [PMID: 27140555 DOI: 10.1364/ao.55.002223] [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 previous paper [Appl. Opt.52, 6364 (2013)APOPAI0003-693510.1364/AO.52.006364] presented experimental work on the stress-optical effect in the terahertz frequency range. Although the theoretical model of experimental measurement is correct, there are two errors in the original version. As a result, the presented experimentally measured value of the refractive index-stress coefficient A of polytetrafluoroethylene (PTFE) is erroneous. This erratum points out the errors in the original paper and reports the correct values.
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