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Shi W, Zhang Y, Wang Z, Yang L, Hou L, Cao J. Detection of optical properties of chiral substances by a photoconductive THz polarization detector. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 319:124490. [PMID: 38820816 DOI: 10.1016/j.saa.2024.124490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 12/21/2023] [Accepted: 05/19/2024] [Indexed: 06/02/2024]
Abstract
Chiral enantiomers have significant differences in biochemical functions. The use of THz wave polarization detection to characterize the optical properties of chiral substances is of great significance to the development of life science and the identification and application of chiral substances. However, the traditional polarization detection procedures of THz waves are complex, which limits the study of chiral substances. Herein, we proposed a high-sensitivity THz polarization detector, which can simultaneously obtain the change information of amplitude, phase, and polarization state through a single measurement. The optical rotation and elliptical angle of solid and liquid D/L-Glutamic acid 5-methyl ester in the THz band are studied. Then it is verified that anisotropic interference may occur in the preparation of solid samples. Finally, the effects of sample content and thickness on polarization are obtained. The experimental results show that different chirality has the opposite effect on the state of polarization, and the difference between chiral enantiomers can be detected by this method. This work is of great significance for understanding the optical properties of chiral substances and promoting the development of chiral recognition.
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Affiliation(s)
- Wei Shi
- Key Laboratory of Ultrafast Photoelectric Technology and Terahertz Science in Shaanxi, Xi'an University of Technology, Xi'an 710048, China.
| | - Yusong Zhang
- Key Laboratory of Ultrafast Photoelectric Technology and Terahertz Science in Shaanxi, Xi'an University of Technology, Xi'an 710048, China
| | - Zhiquan Wang
- Key Laboratory of Ultrafast Photoelectric Technology and Terahertz Science in Shaanxi, Xi'an University of Technology, Xi'an 710048, China; Weinan Normal University, Weinan 714000, China
| | - Lei Yang
- Key Laboratory of Ultrafast Photoelectric Technology and Terahertz Science in Shaanxi, Xi'an University of Technology, Xi'an 710048, China
| | - Lei Hou
- Key Laboratory of Ultrafast Photoelectric Technology and Terahertz Science in Shaanxi, Xi'an University of Technology, Xi'an 710048, China
| | - Juncheng Cao
- The Key Laboratory of Terahertz Solid-State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
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Harris ZB, Xu K, Arbab MH. A handheld polarimetric imaging device and calibration technique for accurate mapping of terahertz Stokes vectors. Sci Rep 2024; 14:17714. [PMID: 39085453 PMCID: PMC11292021 DOI: 10.1038/s41598-024-68530-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 07/24/2024] [Indexed: 08/02/2024] Open
Abstract
In recent years, handheld and portable terahertz instruments have been in rapid development for various applications ranging from non-destructive testing to biomedical imaging and sensing. For instance, we have deployed our Portable Handheld Spectral Reflection (PHASR) Scanners for in vivo full-spectroscopic imaging of skin burns in large animal models in operating room settings. In this paper, we debut the polarimetric version of the PHASR Scanner, and describe a generalized calibration technique to map the spatial and spectral dependence of the Jones matrix of an imaging scanner across its field of view. Our design is based on placement of two orthogonal photoconductive antenna (PCA) detectors separated by a polarizing beam splitter in the PHASR Scanner housing. We show that as few as three independent measurements of a well-characterized polarimetric calibration target are sufficient to determine the polarization state of the incident beam at the sample location, as well as to extract the Jones propagation matrix from the sample location to the detectors. We have tested the accuracy of our scanner by validating polarimetric measurements obtained from a birefringent crystal rotated to various angles, as compared to the theoretically predicted response of the sample. This new version of our PHASR scanner can be used for high-speed imaging and investigation of heterogeneity of polarization-sensitive samples in the field.
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Affiliation(s)
- Zachery B Harris
- Biomedical Engineering Department, Stony Brook University, Stony Brook, NY, USA
| | - Kuangyi Xu
- Biomedical Engineering Department, Stony Brook University, Stony Brook, NY, USA
| | - M Hassan Arbab
- Biomedical Engineering Department, Stony Brook University, Stony Brook, NY, USA.
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3
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Xu K, Arbab MH. Terahertz polarimetric imaging of biological tissue: Monte Carlo modeling of signal contrast mechanisms due to Mie scattering. BIOMEDICAL OPTICS EXPRESS 2024; 15:2328-2342. [PMID: 38633080 PMCID: PMC11019684 DOI: 10.1364/boe.515623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 02/16/2024] [Accepted: 02/27/2024] [Indexed: 04/19/2024]
Abstract
Many promising biomedical applications have been proposed for terahertz (THz) spectroscopy and diagnostic imaging techniques. Polarimetric imaging systems are generally useful for enhancing imaging contrasts, yet the interplay between THz polarization changes and the random discrete structures in biological samples is not well understood. In this work, we performed Monte Carlo simulations of the propagation of polarized THz waves in skin and adipose tissues based on the Mie scattering from intrinsic structures, such as hair follicles or sweat glands. We show that the polarimetric contrasts are distinctly affected by concentration, size and dielectric properties of the scatterers, as well as the frequency and polarization of the incident THz waves. We describe the experimental requirements for observing and extracting these polarimetric signals due to the low energy and small angular spread of the back-scattered THz radiation. We analyzed the spatially integrated Mueller matrices of samples in the normal-incidence back-scattering geometry. We show that the frequency-dependent degree of polarization (DOP) can be used to infer the concentrations and dielectric contents of the scattering structures. Our modeling approach can be used to inform the design of the imaging modalities and the interpretation of the spectroscopic data in future terahertz biomedical imaging applications.
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Affiliation(s)
- Kuangyi Xu
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
| | - M. Hassan Arbab
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
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Ou H, Stantchev RI, Chen X, Blu T, Semtsiv M, Masselink WT, Serrano AH, Costa G, Young J, Chopra N, Lloyd-Hughes J, MacPherson E. Simultaneous measurement of orthogonal terahertz fields via an emission multiplexing scheme. OPTICS EXPRESS 2024; 32:5567-5581. [PMID: 38439279 DOI: 10.1364/oe.505567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 11/10/2023] [Indexed: 03/06/2024]
Abstract
We propose a polarization sensitive terahertz time-domain spectrometer that can record orthogonally polarized terahertz fields simultaneously, using fibre-coupled photoconductive antennas and a scheme that modulated the emitter's polarization. The s and p channels of the multi-pixel terahertz emitter were modulated at different frequencies, thereby allowing orthogonal waveforms to be demultiplexed from the recorded signal in post-processing. The performance of the multi-pixel emitter used in this multiplexing scheme was comparable to that of a commercial single-polarization H-dipole antenna. The approach allowed two orthogonally polarized terahertz pulses to be recorded with good signal to noise (>1000:1) within half a second. We verified the capability of the spectrometer by characterizing a birefringent crystal and by imaging a polarization-sensitive metamaterial. This work has significant potential to improve the speed of terahertz polarization sensitive applications, such as ellipsometry and imaging.
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Xu K, Arbab MH. Terahertz polarimetric imaging of biological tissues: Monte Carlo modeling of signal contrast mechanisms due to Mie scattering. RESEARCH SQUARE 2023:rs.3.rs-3745690. [PMID: 38168438 PMCID: PMC10760297 DOI: 10.21203/rs.3.rs-3745690/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Many promising biomedical applications have been proposed for terahertz (THz) spectroscopy and diagnostic imaging techniques. Polarimetric imaging systems are generally useful for enhancing imaging contrasts, yet the interplay between THz polarization changes and the random discrete structures in biological samples are not well understood. In this work, we performed Monte Carlo simulations of the propagation of polarized THz waves in skin and adipose tissues based on the Mie scattering from intrinsic structures, such as hair follicles or sweat glands. We show that the polarimetric contrasts are distinctly affected by concentration, size and dielectric properties of the scatterers, as well as the frequency and polarization of the incident THz waves. We describe the experimental requirements for observing and extracting these polarimetric signals due to the low energy and small angular spread of the back-scattered THz radiation. We analyzed the spatially integrated Mueller matrices of samples in the normal-incidence back-scattering geometry. We show that the frequency-dependent degree of polarization (DOP) can be used to infer the concentrations and dielectric contents of the scattering structures. Our modeling approach can be used to inform the design of the imaging modalities and the interpretation of the spectroscopic data in future terahertz biomedical imaging applications.
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Affiliation(s)
- Kuangyi Xu
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
| | - M. Hassan Arbab
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
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Xu K, Harris ZB, Arbab MH. Polarimetric imaging of back-scattered terahertz speckle fields using a portable scanner. OPTICS EXPRESS 2023; 31:11308-11319. [PMID: 37155769 PMCID: PMC10316681 DOI: 10.1364/oe.482733] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 02/22/2023] [Accepted: 02/23/2023] [Indexed: 05/10/2023]
Abstract
Speckle patterns observed in coherent optical imaging reflect important characteristic information of the scattering object. To capture speckle patterns, angular resolved or oblique illumination geometries are usually employed in combination with Rayleigh statistical models. We present a portable and handheld 2-channel polarization-sensitive imaging instrument to directly resolve terahertz (THz) speckle fields in a collocated telecentric back-scattering geometry. The polarization state of the THz light is measured using two orthogonal photoconductive antennas and can be presented in the form of the Stokes vectors of the THz beam upon interaction with the sample. We report on the validation of the method in surface scattering from gold-coated sandpapers, demonstrating a strong dependence of the polarization state on the surface roughness and the frequency of the broadband THz illumination. We also demonstrate non-Rayleigh first-order and second-order statistical parameters, such as degree of polarization uniformity (DOPU) and phase difference, for quantifying the randomness of polarization. This technique provides a fast method for broadband THz polarimetric measurement in the field and has the potential for detecting light depolarization in applications ranging from biomedical imaging to non-destructive testing.
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Affiliation(s)
- Kuangyi Xu
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
| | - Zachery B. Harris
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
| | - M. Hassan Arbab
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
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Chen A, Harris ZB, Virk A, Abazari A, Varadaraj K, Honkanen R, Arbab MH. Assessing Corneal Endothelial Damage Using Terahertz Time-Domain Spectroscopy and Support Vector Machines. SENSORS (BASEL, SWITZERLAND) 2022; 22:9071. [PMID: 36501773 PMCID: PMC9735956 DOI: 10.3390/s22239071] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/16/2022] [Accepted: 11/19/2022] [Indexed: 06/17/2023]
Abstract
The endothelial layer of the cornea plays a critical role in regulating its hydration by actively controlling fluid intake in the tissue via transporting the excess fluid out to the aqueous humor. A damaged corneal endothelial layer leads to perturbations in tissue hydration and edema, which can impact corneal transparency and visual acuity. We utilized a non-contact terahertz (THz) scanner designed for imaging spherical targets to discriminate between ex vivo corneal samples with intact and damaged endothelial layers. To create varying grades of corneal edema, the intraocular pressures of the whole porcine eye globe samples (n = 19) were increased to either 25, 35 or 45 mmHg for 4 h before returning to normal pressure levels at 15 mmHg for the remaining 4 h. Changes in tissue hydration were assessed by differences in spectral slopes between 0.4 and 0.8 THz. Our results indicate that the THz response of the corneal samples can vary according to the differences in the endothelial cell density, as determined by SEM imaging. We show that this spectroscopic difference is statistically significant and can be used to assess the intactness of the endothelial layer. These results demonstrate that THz can noninvasively assess the corneal endothelium and provide valuable complimentary information for the study and diagnosis of corneal diseases that perturb the tissue hydration.
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Affiliation(s)
- Andrew Chen
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Zachery B. Harris
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Arjun Virk
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Azin Abazari
- Department of Ophthalmology, Renaissance School of Medicine, 101 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Kulandaiappan Varadaraj
- Department of Physiology and Biophysics, Renaissance School of Medicine, 101 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Robert Honkanen
- Department of Ophthalmology, Renaissance School of Medicine, 101 Nicolls Rd, Stony Brook, NY 11794, USA
| | - Mohammad Hassan Arbab
- Department of Biomedical Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA
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Khani ME, Osman OB, Harris ZB, Chen A, Zhou JW, Singer AJ, Arbab MH. Accurate and early prediction of the wound healing outcome of burn injuries using the wavelet Shannon entropy of terahertz time-domain waveforms. JOURNAL OF BIOMEDICAL OPTICS 2022; 27:JBO-220119GR. [PMID: 36348509 PMCID: PMC9641274 DOI: 10.1117/1.jbo.27.11.116001] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 10/14/2022] [Indexed: 05/06/2023]
Abstract
Significance Severe burn injuries cause significant hypermetabolic alterations that are highly dynamic, hard to predict, and require acute and critical care. The clinical assessments of the severity of burn injuries are highly subjective and have consistently been reported to be inaccurate. Therefore, the utilization of other imaging modalities is crucial to reaching an objective and accurate burn assessment modality. Aim We describe a non-invasive technique using terahertz time-domain spectroscopy (THz-TDS) and the wavelet packet Shannon entropy to automatically estimate the burn depth and predict the wound healing outcome of thermal burn injuries. Approach We created 40 burn injuries of different severity grades in two porcine models using scald and contact methods of infliction. We used our THz portable handheld spectral reflection (PHASR) scanner to obtain the in vivo THz-TDS images. We used the energy to Shannon entropy ratio of the wavelet packet coefficients of the THz-TDS waveforms on day 0 to create supervised support vector machine (SVM) classification models. Histological assessments of the burn biopsies serve as the ground truth. Results We achieved an accuracy rate of 94.7% in predicting the wound healing outcome, as determined by histological measurement of the re-epithelialization rate on day 28 post-burn induction, using the THz-TDS measurements obtained on day 0. Furthermore, we report the accuracy rates of 89%, 87.1%, and 87.6% in automatic diagnosis of the superficial partial-thickness, deep partial-thickness, and full-thickness burns, respectively, using a multiclass SVM model. Conclusions The THz PHASR scanner promises a robust, high-speed, and accurate diagnostic modality to improve the clinical triage of burns and their management.
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Affiliation(s)
- Mahmoud E. Khani
- Stony Brook University, Department of Biomedical Engineering, Stony Brook, New York, United States
| | - Omar B. Osman
- Stony Brook University, Department of Biomedical Engineering, Stony Brook, New York, United States
| | - Zachery B. Harris
- Stony Brook University, Department of Biomedical Engineering, Stony Brook, New York, United States
| | - Andrew Chen
- Stony Brook University, Department of Biomedical Engineering, Stony Brook, New York, United States
| | - Juin W. Zhou
- Stony Brook University, Department of Biomedical Engineering, Stony Brook, New York, United States
| | - Adam J. Singer
- Renaissance School of Medicine at Stony Brook University, Department of Emergency Medicine, Stony Brook, New York, United States
| | - Mohammad Hassan Arbab
- Stony Brook University, Department of Biomedical Engineering, Stony Brook, New York, United States
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Harris ZB, Arbab MH. Terahertz PHASR Scanner with 2 kHz, 100 picosecond Time-Domain Trace Acquisition Rate and an Extended Field-of-View Based on a Heliostat Design. IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY 2022; 12:619-632. [PMID: 36531441 PMCID: PMC9757810 DOI: 10.1109/tthz.2022.3200210] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Recently, we introduced a Portable HAndheld Spectral Reflection (PHASR) Scanner to allow THz Time-Domain Spectroscopic (THz-TDS) imaging in clinical and industrial settings using a fiber-coupled and alignment-free telecentric beam steering design. The key limitations of the version 1.0 of the PHASR Scanner were its field-of-view and speed of time-domain trace acquisition. In this paper, we address these limitations by introducing a heliostat geometry for beam scanning to achieve an extended field-of-view, and by reconfiguring the Asynchronous OPtical Sampling (ASOPS) system to perform Electronically Controlled OPtical Sampling (ECOPS) measurements. The former change improved the deflection range of the beam, while also drastically reducing the coupling of the two scanning axes, the combination of which resulted in a larger than four-fold increase in the FOV area. The latter change significantly improves the acquisition speed and frequency domain performance simultaneously by improving measurement efficiency. To accomplish this, we characterized the non-linear time-axis sampling behavior of the electro-mechanical system in the ECOPS mode. We proposed methods to model and correct the non-linear time-axis distortions and tested the performance of the high-speed ECOPS trace acquisition. Therefore, here we introduce the PHASR Scanner version 2.0, which is capable of imaging a 40×27 mm2 FOV with 2000 traces per second over a 100 picosecond TDS range. This new scanner represents a significant leap towards translating the THz-TDS technology from the lab bench to the bedside for real-time clinical imaging applications.
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Affiliation(s)
- Zachery B Harris
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794, USA
| | - M Hassan Arbab
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, New York 11794, USA
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Khani ME, Harris ZB, Liu M, Arbab MH. Multiresolution spectrally-encoded terahertz reflection imaging through a highly diffusive cloak. OPTICS EXPRESS 2022; 30:31550-31566. [PMID: 36242235 PMCID: PMC9576284 DOI: 10.1364/oe.463599] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 07/15/2022] [Accepted: 07/25/2022] [Indexed: 06/16/2023]
Abstract
Turbid media, made of wavelength-scale inhomogeneous particles, can give rise to many significant imaging and spectroscopy challenges. The random variation of the refractive index within such media distorts the spherical wavefronts, resulting in smeared and speckly images. The scattering-induced artifacts can obscure the characteristic spectral fingerprints of the chemicals in a sample. This in turn prevents accurate chemical imaging and characterization of the materials cloaked with a diffusive medium. In this work, we present a novel computational technique for creating spatially- and spectrally-resolved chemical maps through a diffusive cloak using terahertz time-domain spectroscopy. We use the maximal overlap discrete wavelet transform to obtain a multiresolution spectral decomposition of THz extinction coefficients. We define a new spectroscopic concept dubbed the "bimodality coefficient spectrum" using the skewness and kurtosis of the spectral images. We demonstrate that broadband wavelet-based reconstruction of the bimodality coefficient spectrum can resolve the signature resonant frequencies through the scattering layers. Additionally, we show that our approach can achieve spectral images with diffraction-limited resolution. This technique can be used for stand-off characterization of materials and spectral imaging in nondestructive testing and biological applications.
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Affiliation(s)
- Mahmoud E. Khani
- Department of Biomedical Engineering,
Stony Brook University, 100 Nicolls Rd., Stony Brook, New York 11794, USA
| | - Zachery B. Harris
- Department of Biomedical Engineering,
Stony Brook University, 100 Nicolls Rd., Stony Brook, New York 11794, USA
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, 100 Nicolls Rd., Stony Brook, New York 11794, USA
| | - M. Hassan Arbab
- Department of Biomedical Engineering,
Stony Brook University, 100 Nicolls Rd., Stony Brook, New York 11794, USA
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Nakagawa M, Okano M, Watanabe S. Polarization-sensitive terahertz time-domain spectroscopy system without mechanical moving parts. OPTICS EXPRESS 2022; 30:29421-29434. [PMID: 36299117 DOI: 10.1364/oe.460259] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 06/30/2022] [Indexed: 06/16/2023]
Abstract
We report on the measurement of terahertz electric-field vector waveforms by using a system that contains no mechanical moving parts. It is known that two phase-locked femtosecond lasers with different repetition rates can be used to perform time-domain spectroscopy without using a mechanical delay stage. Furthermore, an electro-optic modulator can be used to perform polarization measurements without rotating any polarizers or waveplates. We experimentally demonstrate the combination of these two methods and explain the analysis of data obtained by such a system. Such a system provides a robust platform that can promote the usage of polarization-sensitive terahertz time-domain spectroscopy in basic science and practical applications. For the experimental demonstration, we alter the polarization of a terahertz wave with a polarizer.
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Xu K, Liu M, Arbab MH. Broadband terahertz time-domain polarimetry based on air plasma filament emissions and spinning electro-optic sampling in GaP. APPLIED PHYSICS LETTERS 2022; 120:181107. [PMID: 35539361 PMCID: PMC9068238 DOI: 10.1063/5.0087127] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 04/19/2022] [Indexed: 05/25/2023]
Abstract
We report on a time-domain polarimetry (TDP) system for generating and detecting broadband terahertz (THz) waves of different polarization angles. We generate THz waves from two-color laser filaments and determine their polarization states with a detection bandwidth of up to 8 THz using a spinning gallium phosphide crystal. The polarization of THz emission can be controlled by adjusting the position and tilt angle of the β-barium borate crystal. We characterize the precision of this system for polarimetric measurements at fixed time delay to be 1.6 ° and 1.9 ° for complete time-domain waveforms. We also demonstrate the feasibility of our TDP system by measuring broadband optical properties of anisotropic samples in both transmission and reflection geometries. The THz-TDP technique can be easily integrated in conventional THz time-domain spectroscopy setups using nonlinear crystal detectors.
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Affiliation(s)
- Kuangyi Xu
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
| | - Mengkun Liu
- Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
| | - M. Hassan Arbab
- Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
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Terahertz Time-Domain Polarimetry for Principal Optical Axes of Anisotropic Crystals. PHOTONICS 2021. [DOI: 10.3390/photonics8060213] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We propose a method for measuring the terahertz properties for two principal optical axes of anisotropic crystals without optical activity using terahertz time-domain spectroscopy (THz-TDS). The method put forward in this paper utilizes the inherent polarization sensitivity of the THz-TDS electro-optic detection system. We demonstrate the practical application of the method by measuring the temperature dependence of the refractive index and the absorption coefficient of a lithium triborate crystal for three optical axes.
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