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Infrared and Terahertz Photonics|16 Article(s)
Single dielectric layer terahertz tube fiber with negative curvature
Xuan Yu, Fei Yu, Sheng Liu, Cheng Lei, and Du Wang
Aiming at low-loss terahertz (THz) fiber fabrication, we propose a negative curvature terahertz tube fiber (NC-TF). Simulation results show that the NC-TF has similar transmission losses (TLs) to the recognized half-ring fiber but with a significantly simpler fabrication structure. NC-TF samples are fabricated by extruding polymers from a specially designed mold, presenting a novel approach for obtaining fibers with shaped boundaries. Experimental data demonstrate that the NC-TF exhibits TLs below 3 dB/m in transmission bands, with a minimum TL of 0.2 dB/m at 0.6 THz. The simplicity and practicality of the NC-TF enable its application in various THz transmission or sensing scenarios. Aiming at low-loss terahertz (THz) fiber fabrication, we propose a negative curvature terahertz tube fiber (NC-TF). Simulation results show that the NC-TF has similar transmission losses (TLs) to the recognized half-ring fiber but with a significantly simpler fabrication structure. NC-TF samples are fabricated by extruding polymers from a specially designed mold, presenting a novel approach for obtaining fibers with shaped boundaries. Experimental data demonstrate that the NC-TF exhibits TLs below 3 dB/m in transmission bands, with a minimum TL of 0.2 dB/m at 0.6 THz. The simplicity and practicality of the NC-TF enable its application in various THz transmission or sensing scenarios.
Chinese Optics Letters
- Publication Date: Mar. 20, 2025
- Vol. 23, Issue 3, 033701 (2025)
Very long wave infrared quantum cascade detector based on modular band structure
Kai Guo, Yu Chen, Yixuan Zhu, Kun Li, Shenqiang Zhai, Fengqi Liu, Jilong Tang, Xiaohua Wang, Zhipeng Wei, and Junqi Liu
The optoelectronic performance of quantum cascade detectors (QCDs) is highly sensitive to the design of the energy level structure, leading to the inability of a single structure to achieve broad wavelength tuning. To address this issue, we propose and demonstrate a modular concept for very long wave infrared (VLWIR) QCDs based on a miniband diagonal transition scheme. The modular design makes the wavelength tuning only need to be adjusted for the absorption quantum well module rather than for the whole active region. Theoretical simulation shows that the wavelength tuning range is 39.6 meV (∼14–30 μm). To prove the feasibility of the scheme, three samples with different absorption well widths were fabricated and characterized. At 10 K, the response wavelengths of the three QCDs are 14, 16, and 18 μm, respectively, corresponding to responsivities and detectivities exceeding 2 mA/W and 1 × 1010 Jones. The optoelectronic performance of quantum cascade detectors (QCDs) is highly sensitive to the design of the energy level structure, leading to the inability of a single structure to achieve broad wavelength tuning. To address this issue, we propose and demonstrate a modular concept for very long wave infrared (VLWIR) QCDs based on a miniband diagonal transition scheme. The modular design makes the wavelength tuning only need to be adjusted for the absorption quantum well module rather than for the whole active region. Theoretical simulation shows that the wavelength tuning range is 39.6 meV (∼14–30 μm). To prove the feasibility of the scheme, three samples with different absorption well widths were fabricated and characterized. At 10 K, the response wavelengths of the three QCDs are 14, 16, and 18 μm, respectively, corresponding to responsivities and detectivities exceeding 2 mA/W and 1 × 1010 Jones.
Chinese Optics Letters
- Publication Date: Aug. 13, 2024
- Vol. 22, Issue 8, 083701 (2024)
Coherent terahertz wave emission from laser-induced plasma in isotropic transparent solid dielectrics
Yuxuan Chen, Yuhang He, Chenyin Dai, Xiangyu La, Zhen Tian, and Jianming Dai
In this Letter, we employ fused silica and two types of optical glass as examples to investigate the coherent terahertz (THz) wave emission from laser-ionized isotropic transparent dielectrics. Based on the laser energy and incident angle dependences, we ascribe the THz emission to the ponderomotive force-induced dipole oscillation. Additionally, our investigation on the dependence of THz amplitude on the laser pulse duration confirms the dominant role of avalanche ionization in solid dielectrics. The THz emission can be utilized to indirectly monitor the ultrafast dynamics of carrier generation and motion during the laser ionization process of solid dielectrics. In this Letter, we employ fused silica and two types of optical glass as examples to investigate the coherent terahertz (THz) wave emission from laser-ionized isotropic transparent dielectrics. Based on the laser energy and incident angle dependences, we ascribe the THz emission to the ponderomotive force-induced dipole oscillation. Additionally, our investigation on the dependence of THz amplitude on the laser pulse duration confirms the dominant role of avalanche ionization in solid dielectrics. The THz emission can be utilized to indirectly monitor the ultrafast dynamics of carrier generation and motion during the laser ionization process of solid dielectrics.
Chinese Optics Letters
- Publication Date: Jul. 25, 2024
- Vol. 22, Issue 7, 073701 (2024)
Mechanically reconfigurable terahertz polarization converter by coupling-mediated metasurfaces
Zhibo Yao, Zhaohua Xu, Xiaoyuan Hao, Jiajun He, Yanfeng Zhao, Xiangyu Liu, Yanfeng Li, Xueqian Zhang, Quan Xu, Su Xu, and Jiaguang Han
Free manipulation of electromagnetic waves in the terahertz (THz) band based on metasurface functional devices has been the focus of research in recent years. Among these devices, active metasurfaces have generated extensive research interest due to their reconfigurability. In this work, we demonstrate a mechanically reconfigurable THz polarization converter that consists of two parallel transmissive metasurfaces with a tunable spacing. By mechanically adjusting the coupling strength between the metasurfaces, the orthogonal polarization conversion of the incident linearly polarized THz waves can be tuned. Specifically, the device can be tuned from efficient dual-frequency orthogonal polarization conversion to efficient single-frequency orthogonal polarization conversion. After a gradual decrease in efficiency, it is finally changed to a low transmission state as the gap distance increases from 150 to 800 µm. We theoretically analyze the tuning process under different spacings and experimentally verify it using a vector network analyzer. Our proposed design is straightforward and robust, with the potential to find wide applications in THz science and technology. Free manipulation of electromagnetic waves in the terahertz (THz) band based on metasurface functional devices has been the focus of research in recent years. Among these devices, active metasurfaces have generated extensive research interest due to their reconfigurability. In this work, we demonstrate a mechanically reconfigurable THz polarization converter that consists of two parallel transmissive metasurfaces with a tunable spacing. By mechanically adjusting the coupling strength between the metasurfaces, the orthogonal polarization conversion of the incident linearly polarized THz waves can be tuned. Specifically, the device can be tuned from efficient dual-frequency orthogonal polarization conversion to efficient single-frequency orthogonal polarization conversion. After a gradual decrease in efficiency, it is finally changed to a low transmission state as the gap distance increases from 150 to 800 µm. We theoretically analyze the tuning process under different spacings and experimentally verify it using a vector network analyzer. Our proposed design is straightforward and robust, with the potential to find wide applications in THz science and technology.
Chinese Optics Letters
- Publication Date: Dec. 24, 2024
- Vol. 22, Issue 12, 123701 (2024)
High-resolution temporal overlap with proper dispersion compensation for a coherent photocurrent experiment revealed by terahertz time-domain emission spectroscopy
Xueqin Cao, Fan Wang, Leidong Xing, Zeyun Wang, Yuanyuan Huang, and Xinlong Xu
Coherent control of terahertz (THz) wave radiation with two-color laser excitation requires good temporal overlap with good dispersion control of both the fundamental (ω) and the second harmonic (2ω). Herein, we experimentally determined the temporal overlap of the ω and 2ω pulses in the time-domain, which was corroborated by theoretical calculations. Furthermore, the coherent control of THz radiation of ZnSe also proves the good temporal overlap of two-color femtosecond lasers. This work provides an experimental tool for finding temporal overlap and realizing the dispersion control of two femtosecond lasers. Coherent control of terahertz (THz) wave radiation with two-color laser excitation requires good temporal overlap with good dispersion control of both the fundamental (ω) and the second harmonic (2ω). Herein, we experimentally determined the temporal overlap of the ω and 2ω pulses in the time-domain, which was corroborated by theoretical calculations. Furthermore, the coherent control of THz radiation of ZnSe also proves the good temporal overlap of two-color femtosecond lasers. This work provides an experimental tool for finding temporal overlap and realizing the dispersion control of two femtosecond lasers.
Chinese Optics Letters
- Publication Date: Nov. 14, 2024
- Vol. 22, Issue 11, 113701 (2024)
Terahertz chiral edge states enable inner-chip state transition and interchip communications over wireless terminals
Hong Chen, Hang Ren, Wenya Wang, Zhaohua Xu, Yanfeng Li, Quan Xu, Jiaguang Han, and Su Xu
Topological valley photonics has recently gained widespread interest owing to its robustness and backscattering immunity against disorders. Previous topological valley transport based on kink states required an interface between two topologically distinct domains, while recent studies have reported that chiral edge states (CESs) can be realized at the external boundary of topological insulators by changing the on-site edge potentials. However, current research on CESs is predominantly focused on the microwave frequency range, leaving challenges for emerging terahertz communications. Here, cladding-free CESs are demonstrated at the external boundary of terahertz all-silicon topological valley photonic crystals with gapless, single-mode, and linear dispersion. We show that CESs are immune to backscattering against sharp corners and support unidirectional propagation of chiral excitations. We also achieved smooth transition between kink states and CESs supported by an all-silicon platform, which could be used as the terahertz inner-chip connection. Finally, a terahertz wireless link between two disconnected CESs is verified for the near-field information interconnection between distinct mobile phones. Our work indicates CESs can improve the compactness of terahertz circuits and inspire advanced terahertz interchip communications. Topological valley photonics has recently gained widespread interest owing to its robustness and backscattering immunity against disorders. Previous topological valley transport based on kink states required an interface between two topologically distinct domains, while recent studies have reported that chiral edge states (CESs) can be realized at the external boundary of topological insulators by changing the on-site edge potentials. However, current research on CESs is predominantly focused on the microwave frequency range, leaving challenges for emerging terahertz communications. Here, cladding-free CESs are demonstrated at the external boundary of terahertz all-silicon topological valley photonic crystals with gapless, single-mode, and linear dispersion. We show that CESs are immune to backscattering against sharp corners and support unidirectional propagation of chiral excitations. We also achieved smooth transition between kink states and CESs supported by an all-silicon platform, which could be used as the terahertz inner-chip connection. Finally, a terahertz wireless link between two disconnected CESs is verified for the near-field information interconnection between distinct mobile phones. Our work indicates CESs can improve the compactness of terahertz circuits and inspire advanced terahertz interchip communications.
Chinese Optics Letters
- Publication Date: Oct. 15, 2024
- Vol. 22, Issue 10, 103701 (2024)
Terahertz wide-angle metalens with nearly ideal object-image relation
Yu Wang, Jierong Cheng, Yunyun Ji, Fei Fan, and Shengjiang Chang
Metalenses are essential components in terahertz imaging systems. However, without careful design, they show limited field of view and their practical applications are hindered. Here, a wide-angle metalens is proposed whose structure is optimized for focusing within the incident angles of ±25°. Simulation and experiment results show that the focusing efficiency, spot size, and modulation transfer function of this lens are not sensitive to the incident angle. More importantly, this wide-angle metalens follows the ideal Gaussian formula for the object-image relation, which ensures a wider field of view and better contrast in the imaging experiment. Metalenses are essential components in terahertz imaging systems. However, without careful design, they show limited field of view and their practical applications are hindered. Here, a wide-angle metalens is proposed whose structure is optimized for focusing within the incident angles of ±25°. Simulation and experiment results show that the focusing efficiency, spot size, and modulation transfer function of this lens are not sensitive to the incident angle. More importantly, this wide-angle metalens follows the ideal Gaussian formula for the object-image relation, which ensures a wider field of view and better contrast in the imaging experiment.
Chinese Optics Letters
- Publication Date: Jan. 08, 2024
- Vol. 22, Issue 1, 013701 (2024)
NH3 laser THz emission under optical pumping by “long” (∼100 µs) CO2 laser pulses
Andrey Alekseevich Ionin, Igor Olegovich Kinyaevskiy, Yuri Mikhailovich Klimachev, Andrey Yurievich Kozlov, Darya Ivanovna Kormashova, Andrey Alexandrovich Kotkov, Yury Alekseevich Mityagin, Sergey Alexandrovich Savinov, Adilya Maratovna Sagitova, Dmitry Vasilievich Sinitsyn, and Maxim Vladimirovich Ionin
Terahertz (THz) NH3 lasing with optical pumping by electron-beam-sustained discharge “long” (∼100 µs) CO2 laser pulses was obtained. The NH3 laser emission pulses and the “long” pulses of the CO2 pump laser were simultaneously measured with nanosecond response time. The NH3 lasing duration and its delay with respect to the pump pulse were measured for various CO2 laser pulse energies. For the CO2 laser pump line 9R(30), three wavelengths of 67.2, 83.8, and 88.9 µm were recorded. For the CO2 laser pump line 9R(16), only a single NH3 laser line with a wavelength of 90.4 µm was detected. Terahertz (THz) NH3 lasing with optical pumping by electron-beam-sustained discharge “long” (∼100 µs) CO2 laser pulses was obtained. The NH3 laser emission pulses and the “long” pulses of the CO2 pump laser were simultaneously measured with nanosecond response time. The NH3 lasing duration and its delay with respect to the pump pulse were measured for various CO2 laser pulse energies. For the CO2 laser pump line 9R(30), three wavelengths of 67.2, 83.8, and 88.9 µm were recorded. For the CO2 laser pump line 9R(16), only a single NH3 laser line with a wavelength of 90.4 µm was detected.
Chinese Optics Letters
- Publication Date: Oct. 08, 2022
- Vol. 21, Issue 2, 023701 (2023)
Role of the interlayer interactions in ultrafast terahertz thermal dynamics of bilayer graphene
Tingyuan Jia, Shaoming Xie, Zeyu Zhang, Qinxue Yin, Chunwei Wang, Chenjing Quan, Xiao Xing, Juan Du, and Yuxin Leng
Bilayer graphene, which is highly promising for electronic and optoelectronic applications because of its strong coupling of the Dirac–Fermions, has been studied extensively for the emergent correlated phenomena with magic-angle manipulation. Due to the low energy linear type band gap dispersion relationship, graphene has drawn an amount of optoelectronic devices applications in the terahertz region. However, the strong interlayer interactions modulated electron-electron and electron-phonon coupling, and their dynamics in bilayer graphene have been rarely studied by terahertz spectroscopy. In this study, the interlayer interaction influence on the electron-electron and the electron-phonon coupling has been assigned with the interaction between the two graphene layers. In the ultrafast cooling process in bilayer graphene, the interlayer interaction could boost the electron-phonon coupling process and oppositely reduce the electron-electron coupling process, which led to the less efficient thermalization process. Furthermore, the electron-electron coupling process is shown to be related with the electron momentum scattering time, which increased vividly in bilayer graphene. Our work could provide new insights into the ultrafast dynamics in bilayer graphene, which is of crucial importance for designing multi-layer graphene-based optoelectronic devices. Bilayer graphene, which is highly promising for electronic and optoelectronic applications because of its strong coupling of the Dirac–Fermions, has been studied extensively for the emergent correlated phenomena with magic-angle manipulation. Due to the low energy linear type band gap dispersion relationship, graphene has drawn an amount of optoelectronic devices applications in the terahertz region. However, the strong interlayer interactions modulated electron-electron and electron-phonon coupling, and their dynamics in bilayer graphene have been rarely studied by terahertz spectroscopy. In this study, the interlayer interaction influence on the electron-electron and the electron-phonon coupling has been assigned with the interaction between the two graphene layers. In the ultrafast cooling process in bilayer graphene, the interlayer interaction could boost the electron-phonon coupling process and oppositely reduce the electron-electron coupling process, which led to the less efficient thermalization process. Furthermore, the electron-electron coupling process is shown to be related with the electron momentum scattering time, which increased vividly in bilayer graphene. Our work could provide new insights into the ultrafast dynamics in bilayer graphene, which is of crucial importance for designing multi-layer graphene-based optoelectronic devices.
Chinese Optics Letters
- Publication Date: Jun. 15, 2022
- Vol. 20, Issue 9, 093701 (2022)
Tunable broadband terahertz absorber based on laser-induced graphene
Jingxuan Lan, Rongxuan Zhang, Hao Bai, Caidie Zhang, Xu Zhang, Wei Hu, Lei Wang, and Yanqing Lu
Terahertz (THz) absorbers for imaging, sensing, and detection are in high demand. However, such devices suffer from high manufacturing costs and limited absorption bandwidths. In this study, we presented a low-cost broadband tunable THz absorber based on one-step laser-induced graphene (LIG). The laser-machining-parameter-dependent morphology and performance of the absorbers were investigated. Coarse tuning of THz absorption was realized by changing the laser power, while it was fine-tuned by changing the scanning speed. The proposed structure can achieve over 90% absorption from 0.5 THz to 2 THz with optimized parameters. The LIG method can help in the development of various THz apparatuses. Terahertz (THz) absorbers for imaging, sensing, and detection are in high demand. However, such devices suffer from high manufacturing costs and limited absorption bandwidths. In this study, we presented a low-cost broadband tunable THz absorber based on one-step laser-induced graphene (LIG). The laser-machining-parameter-dependent morphology and performance of the absorbers were investigated. Coarse tuning of THz absorption was realized by changing the laser power, while it was fine-tuned by changing the scanning speed. The proposed structure can achieve over 90% absorption from 0.5 THz to 2 THz with optimized parameters. The LIG method can help in the development of various THz apparatuses.
Chinese Optics Letters
- Publication Date: May. 24, 2022
- Vol. 20, Issue 7, 073701 (2022)
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