Contents
2023
Volume: 11 Issue 6
24 Article(s)
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Research Articles
Fiber Optics and Optical Communications
Chaos synchronization of semiconductor lasers over 1040-km fiber relay transmission with hybrid amplification
Longsheng Wang, Junli Wang, Yushan Wu, Yuehui Sun, Songsui Li, Lianshan Yan, Yuncai Wang, and Anbang Wang
Optical chaos communication and key distribution have been extensively demonstrated with high-speed advantage but only within the metropolitan-area network range of which the transmission distance is restricted to around 300 km. For secure-transmission requirement of the backbone fiber link, the critical threshold is to realize long-reach chaos synchronization. Here, we propose and demonstrate a scheme of long-reach chaos synchronization using fiber relay transmission with hybrid amplification of an erbium-doped fiber amplifier (EDFA) and a distributed fiber Raman amplifier (DFRA). Experiments and simulations show that the hybrid amplification extends the chaos-fidelity transmission distance thanks to that the low-noise DFRA suppresses the amplified spontaneous emission noise and self-phase modulation. Optimizations of the hybrid-relay conditions are studied, including launching power, gain ratio of DFRA to EDFA, single-span fiber length, and number of fiber span. A 1040-km chaos synchronization with a synchronization coefficient beyond 0.90 is experimentally achieved, which underlies the backbone network-oriented optical chaos communication and key distribution.Optical chaos communication and key distribution have been extensively demonstrated with high-speed advantage but only within the metropolitan-area network range of which the transmission distance is restricted to around 300 km. For secure-transmission requirement of the backbone fiber link, the critical threshold is to realize long-reach chaos synchronization. Here, we propose and demonstrate a scheme of long-reach chaos synchronization using fiber relay transmission with hybrid amplification of an erbium-doped fiber amplifier (EDFA) and a distributed fiber Raman amplifier (DFRA). Experiments and simulations show that the hybrid amplification extends the chaos-fidelity transmission distance thanks to that the low-noise DFRA suppresses the amplified spontaneous emission noise and self-phase modulation. Optimizations of the hybrid-relay conditions are studied, including launching power, gain ratio of DFRA to EDFA, single-span fiber length, and number of fiber span. A 1040-km chaos synchronization with a synchronization coefficient beyond 0.90 is experimentally achieved, which underlies the backbone network-oriented optical chaos communication and key distribution..
Photonics Research
- Publication Date: May. 16, 2023
- Vol. 11, Issue 6, 953 (2023)
300 km ultralong fiber optic DAS system based on optimally designed bidirectional EDFA relays
Cunzheng Fan, Hao Li, Keqing Zhang, Huanhuan Liu, Yixiang Sun, Haoguang Liu, Baoqiang Yan, Zhijun Yan, Deming Liu, Perry Ping Shum, and Qizhen Sun
Optical fiber distributed acoustic sensing (DAS) based on phase-sensitive optical time domain reflectometry (φ-OTDR) is in great demand in many long-distance application fields, such as railway and pipeline safety monitoring. However, the DAS measurement distance is limited by the transmission loss of optical fiber and ultralow backscattering power. In this paper, a DAS system based on multispan relay amplification is proposed, where the bidirectional erbium-doped fiber amplifier (EDFA) is designed as a relay module to amplify both the probe light and the backscattering light. In the theoretical noise model, the parameters of our system are carefully analyzed and optimized for a longer sensing distance, including the extinction ratio (ER), span number, span length, and gain of erbium-doped fiber amplifiers. The numerical simulation shows that a bidirectional EDFA relay DAS system can detect signals over 2500 km, as long as the span number is set to be more than 100. To verify the effectiveness of the scheme, a six-span coherent-detection-based DAS system with an optimal design was established, where the cascaded acoustic-optic modulators (AOMs) were used for a high ER of 104 dB. The results demonstrate that the signal at the far end of 300.2 km can be detected and recovered, achieving a high signal-to-noise ratio of 59.6 dB and a high strain resolution of 51.8pε/Hz at 50 Hz with a 20 m spatial resolution. This is, to the best of our knowledge, a superior DAS sensing distance with such a high strain resolution.Optical fiber distributed acoustic sensing (DAS) based on phase-sensitive optical time domain reflectometry (φ-OTDR) is in great demand in many long-distance application fields, such as railway and pipeline safety monitoring. However, the DAS measurement distance is limited by the transmission loss of optical fiber and ultralow backscattering power. In this paper, a DAS system based on multispan relay amplification is proposed, where the bidirectional erbium-doped fiber amplifier (EDFA) is designed as a relay module to amplify both the probe light and the backscattering light. In the theoretical noise model, the parameters of our system are carefully analyzed and optimized for a longer sensing distance, including the extinction ratio (ER), span number, span length, and gain of erbium-doped fiber amplifiers. The numerical simulation shows that a bidirectional EDFA relay DAS system can detect signals over 2500 km, as long as the span number is set to be more than 100. To verify the effectiveness of the scheme, a six-span coherent-detection-based DAS system with an optimal design was established, where the cascaded acoustic-optic modulators (AOMs) were used for a high ER of 104 dB. The results demonstrate that the signal at the far end of 300.2 km can be detected and recovered, achieving a high signal-to-noise ratio of 59.6 dB and a high strain resolution of
Photonics Research
- Publication Date: May. 18, 2023
- Vol. 11, Issue 6, 968 (2023)
Imaging Systems, Microscopy, and Displays
Real-time noise-free inline self-interference incoherent digital holography with temporal geometric phase multiplexing
Kihong Choi, Jae-Won Lee, Jungyeop Shin, Keehoon Hong, Joongki Park, and Hak-Rin Kim
In this paper, we propose a real-time incoherent digital holographic (IDH) recording system free from bias and twin-image noises. A motionless three-step polarization-encoded phase-shifter operating at 99 Hz is realized with two electrically controllable birefringence-mode liquid crystal cells operating in tandem with a geometric phase lens and polarizers. Based on the proposed optical configuration, a coaxial straight-line self-interference IDH recording system is devised. Notably, the elimination of bias and twin-image noise from three phase-shifted images is demonstrated as a proof of concept. Moreover, complex-valued holographic video acquisitions with a resolution greater than 20 megapixels are demonstrated, with an effective acquisition frequency of 33 Hz.In this paper, we propose a real-time incoherent digital holographic (IDH) recording system free from bias and twin-image noises. A motionless three-step polarization-encoded phase-shifter operating at 99 Hz is realized with two electrically controllable birefringence-mode liquid crystal cells operating in tandem with a geometric phase lens and polarizers. Based on the proposed optical configuration, a coaxial straight-line self-interference IDH recording system is devised. Notably, the elimination of bias and twin-image noise from three phase-shifted images is demonstrated as a proof of concept. Moreover, complex-valued holographic video acquisitions with a resolution greater than 20 megapixels are demonstrated, with an effective acquisition frequency of 33 Hz..
Photonics Research
- Publication Date: May. 04, 2023
- Vol. 11, Issue 6, 906 (2023)
Direct observation of longitudinal aberrated wavefields
J. P. Trevino, V. Coello, A. Jaimes-Nájera, C. E. Garcia-Ortiz, S. Chávez-Cerda, and J. E. Gómez-Correa
Rather than focusing on a focal spot, aberrated wavefields spread out over a region. As a wave phenomenon, optical aberrations are analyzed in terms of waves propagating in the 3D space. In this work, we report the observation of 2D longitudinal aberrated wavefields. This observation can be visualized by mapping the intensity distributions of surface plasmon polaritons (SPPs) that propagate on a metal/air interface using leakage radiation microscopy. The orientation of the SPP beam is tweaked by tilting and translating the system to mimic aberrated beams, presenting known Seidel terms: defocus, spherical, coma, and tilt aberration. This approach allows the examination of the longitudinal evolution of aberrated beams in a visual and rapid manner, in contrast to more complicated post-processing reconstructions.Rather than focusing on a focal spot, aberrated wavefields spread out over a region. As a wave phenomenon, optical aberrations are analyzed in terms of waves propagating in the 3D space. In this work, we report the observation of 2D longitudinal aberrated wavefields. This observation can be visualized by mapping the intensity distributions of surface plasmon polaritons (SPPs) that propagate on a metal/air interface using leakage radiation microscopy. The orientation of the SPP beam is tweaked by tilting and translating the system to mimic aberrated beams, presenting known Seidel terms: defocus, spherical, coma, and tilt aberration. This approach allows the examination of the longitudinal evolution of aberrated beams in a visual and rapid manner, in contrast to more complicated post-processing reconstructions..
Photonics Research
- Publication Date: May. 26, 2023
- Vol. 11, Issue 6, 1015 (2023)
Physical origin and boundary of scalable imaging through scattering media: a deep learning-based exploration | Editors' Pick
Xuyu Zhang, Shengfu Cheng, Jingjing Gao, Yu Gan, Chunyuan Song, Dawei Zhang, Songlin Zhuang, Shensheng Han, Puxiang Lai, and Honglin Liu
Imaging through scattering media is valuable for many areas, such as biomedicine and communication. Recent progress enabled by deep learning (DL) has shown superiority especially in the model generalization. However, there is a lack of research to physically reveal the origin or define the boundary for such model scalability, which is important for utilizing DL approaches for scalable imaging despite scattering with high confidence. In this paper, we find the amount of the ballistic light component in the output field is the prerequisite for endowing a DL model with generalization capability by using a “one-to-all” training strategy, which offers a physical meaning invariance among the multisource data. The findings are supported by both experimental and simulated tests in which the roles of scattered and ballistic components are revealed in contributing to the origin and physical boundary of the model scalability. Experimentally, the generalization performance of the network is enhanced by increasing the portion of ballistic photons in detection. The mechanism understanding and practical guidance by our research are beneficial for developing DL methods for descattering with high adaptivity.Imaging through scattering media is valuable for many areas, such as biomedicine and communication. Recent progress enabled by deep learning (DL) has shown superiority especially in the model generalization. However, there is a lack of research to physically reveal the origin or define the boundary for such model scalability, which is important for utilizing DL approaches for scalable imaging despite scattering with high confidence. In this paper, we find the amount of the ballistic light component in the output field is the prerequisite for endowing a DL model with generalization capability by using a “one-to-all” training strategy, which offers a physical meaning invariance among the multisource data. The findings are supported by both experimental and simulated tests in which the roles of scattered and ballistic components are revealed in contributing to the origin and physical boundary of the model scalability. Experimentally, the generalization performance of the network is enhanced by increasing the portion of ballistic photons in detection. The mechanism understanding and practical guidance by our research are beneficial for developing DL methods for descattering with high adaptivity..
Photonics Research
- Publication Date: May. 26, 2023
- Vol. 11, Issue 6, 1038 (2023)
Instrumentation and Measurements
Free-space interferometer design for optical frequency dissemination and out-of-loop characterization below the 10−21-level
Thomas Jürss, Gesine Grosche, and Sebastian Koke
For improving the performance of optical frequency dissemination and the resolution of its out-of-loop (OOL) characterization, we investigate a compact free-space interferometer design in which a monolithic assembly forms the reference arm. Two interferometer designs are realized, and their environmental sensitivity is analyzed based on the properties of the materials involved. We elucidate that in these designs the temperature sensitivities of the out-of-loop signal paths are greater than for the reference arm. As the estimated temperature-variation-induced frequency transfer errors are observed to be the relevant limitation, the out-of-loop characterization signal can be regarded as a trustworthy upper limit of the frequency transfer error to a remote place. We demonstrate a fractional frequency transfer uncertainty and OOL characterization resolution of ≤2.7×10-21 over many measurement runs. With a value of (0.23±1.07)×10-22 the weighted mean offset is significantly below the best reported results so far.For improving the performance of optical frequency dissemination and the resolution of its out-of-loop (OOL) characterization, we investigate a compact free-space interferometer design in which a monolithic assembly forms the reference arm. Two interferometer designs are realized, and their environmental sensitivity is analyzed based on the properties of the materials involved. We elucidate that in these designs the temperature sensitivities of the out-of-loop signal paths are greater than for the reference arm. As the estimated temperature-variation-induced frequency transfer errors are observed to be the relevant limitation, the out-of-loop characterization signal can be regarded as a trustworthy upper limit of the frequency transfer error to a remote place. We demonstrate a fractional frequency transfer uncertainty and OOL characterization resolution of
Photonics Research
- Publication Date: Jun. 01, 2023
- Vol. 11, Issue 6, 1113 (2023)
Integrated Optics
408 Gbit/s PAM-8 sidewall-doped germanium–silicon photodetector
Xiao Hu, Dingyi Wu, Ye Liu, Daigao Chen, Lei Wang, Xi Xiao, and Shaohua Yu
Based on the 90 nm silicon photonics commercial foundry, sidewall-doped germanium–silicon photodetectors (PDs) are designed and fabricated. The large designed overlap between the optical field and electric field achieves high responsivity while retaining high-speed performance. Even including the loss due to optical fiber coupling, the PD demonstrates an external responsivity greater than 0.55 A/W for transverse magnetic (TM) polarization and 0.65 A/W for transverse electric (TE) polarization at 1530 nm. A flat responsivity spectrum of >0.5 A/W is achieved up to 1580 nm for both polarizations. Their internal responsivities can exceed 1 A/W in the C+L optical communication bands. Furthermore, with the aid of a 200 mm wafer-level test and analysis, the overall PDs of 26 reticles have a 3 dB optoelectrical bandwidth >50 GHz and a dark current <10 nA at a -3 V bias voltage. Finally, the eye diagram performances under TE and TM polarizations, various modulation formats, and different input wavelengths are comprehensively investigated. The clear open electrical eye diagrams up to 120, 130, 140, and 150 Gbit/s nonreturn-to-zero are experimentally attained at a photocurrent of 1 mA. To the best of our knowledge, this is the first time that single-lane direct detection of record-high-speed 200, 224, 256, and 290 Gbit/s four-level pulse amplitude modulation (PAM) and 300, 336, 384, and 408 Gbit/s eight-level PAM optical signals has been experimentally achieved.Based on the 90 nm silicon photonics commercial foundry, sidewall-doped germanium–silicon photodetectors (PDs) are designed and fabricated. The large designed overlap between the optical field and electric field achieves high responsivity while retaining high-speed performance. Even including the loss due to optical fiber coupling, the PD demonstrates an external responsivity greater than 0.55 A/W for transverse magnetic (TM) polarization and 0.65 A/W for transverse electric (TE) polarization at 1530 nm. A flat responsivity spectrum of
Photonics Research
- Publication Date: May. 16, 2023
- Vol. 11, Issue 6, 961 (2023)
Sophisticated deep learning with on-chip optical diffractive tensor processing
Yuyao Huang, Tingzhao Fu, Honghao Huang, Sigang Yang, and Hongwei Chen
Ever-growing deep-learning technologies are making revolutionary changes for modern life. However, conventional computing architectures are designed to process sequential and digital programs but are burdened with performing massive parallel and adaptive deep-learning applications. Photonic integrated circuits provide an efficient approach to mitigate bandwidth limitations and the power-wall brought on by its electronic counterparts, showing great potential in ultrafast and energy-free high-performance computation. Here, we propose an optical computing architecture enabled by on-chip diffraction to implement convolutional acceleration, termed “optical convolution unit” (OCU). We demonstrate that any real-valued convolution kernels can be exploited by the OCU with a prominent computational throughput boosting via the concept of structral reparameterization. With the OCU as the fundamental unit, we build an optical convolutional neural network (oCNN) to implement two popular deep learning tasks: classification and regression. For classification, Fashion Modified National Institute of Standards and Technology (Fashion-MNIST) and Canadian Institute for Advanced Research (CIFAR-4) data sets are tested with accuracies of 91.63% and 86.25%, respectively. For regression, we build an optical denoising convolutional neural network to handle Gaussian noise in gray-scale images with noise level σ=10, 15, and 20, resulting in clean images with an average peak signal-to-noise ratio (PSNR) of 31.70, 29.39, and 27.72 dB, respectively. The proposed OCU presents remarkable performance of low energy consumption and high information density due to its fully passive nature and compact footprint, providing a parallel while lightweight solution for future compute-in-memory architecture to handle high dimensional tensors in deep learning.Ever-growing deep-learning technologies are making revolutionary changes for modern life. However, conventional computing architectures are designed to process sequential and digital programs but are burdened with performing massive parallel and adaptive deep-learning applications. Photonic integrated circuits provide an efficient approach to mitigate bandwidth limitations and the power-wall brought on by its electronic counterparts, showing great potential in ultrafast and energy-free high-performance computation. Here, we propose an optical computing architecture enabled by on-chip diffraction to implement convolutional acceleration, termed “optical convolution unit” (OCU). We demonstrate that any real-valued convolution kernels can be exploited by the OCU with a prominent computational throughput boosting via the concept of structral reparameterization. With the OCU as the fundamental unit, we build an optical convolutional neural network (oCNN) to implement two popular deep learning tasks: classification and regression. For classification, Fashion Modified National Institute of Standards and Technology (Fashion-MNIST) and Canadian Institute for Advanced Research (CIFAR-4) data sets are tested with accuracies of 91.63% and 86.25%, respectively. For regression, we build an optical denoising convolutional neural network to handle Gaussian noise in gray-scale images with noise level
Photonics Research
- Publication Date: Jun. 01, 2023
- Vol. 11, Issue 6, 1125 (2023)
Lasers and Laser Optics
Hundredfold increase of stimulated Brillouin-scattering bandwidth in whispering-gallery mode resonators | Editors' Pick
Guoping Lin, Jingyi Tian, Tang Sun, Qinghai Song, and Yanne K. Chembo
Backward stimulated Brillouin scattering (SBS) is widely exploited for various applications in optics and optoelectronics. It typically features a narrow gain bandwidth of a few tens of megahertz in fluoride crystals. Here we report a hundredfold increase of SBS bandwidth in whispering-gallery mode resonators. The crystalline orientation results in a large variation of the acoustic phase velocity upon propagation along the periphery, from which a broad Brillouin gain is formed. Over 2.5 GHz wide Brillouin gain profile is theoretically found and experimentally validated. SBS phenomena with Brillouin shift frequencies ranging from 11.73 to 14.47 GHz in ultrahigh QZ-cut magnesium fluoride cavities pumped at the telecommunication wavelength are demonstrated. Furthermore, the Brillouin–Kerr comb in this device is demonstrated. Over 400 comb lines spanning across a spectral window of 120 nm are observed. Our finding paves a new way for tailoring and harnessing the Brillouin gain in crystals.Backward stimulated Brillouin scattering (SBS) is widely exploited for various applications in optics and optoelectronics. It typically features a narrow gain bandwidth of a few tens of megahertz in fluoride crystals. Here we report a hundredfold increase of SBS bandwidth in whispering-gallery mode resonators. The crystalline orientation results in a large variation of the acoustic phase velocity upon propagation along the periphery, from which a broad Brillouin gain is formed. Over 2.5 GHz wide Brillouin gain profile is theoretically found and experimentally validated. SBS phenomena with Brillouin shift frequencies ranging from 11.73 to 14.47 GHz in ultrahigh QZ-cut magnesium fluoride cavities pumped at the telecommunication wavelength are demonstrated. Furthermore, the Brillouin–Kerr comb in this device is demonstrated. Over 400 comb lines spanning across a spectral window of 120 nm are observed. Our finding paves a new way for tailoring and harnessing the Brillouin gain in crystals..
Photonics Research
- Publication Date: May. 16, 2023
- Vol. 11, Issue 6, 917 (2023)
Dynamics of a dispersion-tuned swept-fiber laser
Duidui Li, Guolu Yin, Ligang Huang, Lei Gao, Laiyang Dang, Zeheng Zhang, Jingsheng Huang, Huafeng Lu, and Tao Zhu
In this paper, we studied the dynamics of a dispersion-tuned swept-fiber laser both experimentally and theoretically. By adding a dispersion compensation fiber and an electro-optic modulator in the laser cavity, an actively mode-locked laser was obtained by using intensity modulation, and wavelength sweeping was realized by changing the modulation frequency. Using a high-speed real-time oscilloscope, the dynamic behaviors of the swept laser were investigated during wavelength switching, static-sweeping cycle, and continuous sweeping, respectively. It was found that the laser generates relaxation oscillation at the start of the sweeping mode. The relaxation oscillation process lasted for about 0.7 ms, and then the laser started to operate stably. Due to the nonlinear effect, new wavelengths were generated in the relaxation oscillation process, which is not beneficial for applications. Fortunately, relaxation oscillation disappears if the laser starts up and operates in the continuous sweeping mode, and the good sweeping symmetry between the positive sweep and negative sweep increases the application potential of the laser. In addition, the instantaneous linewidth is almost the same as that in the static state. These results describe the characteristics of the laser from a new perspective and reveal, to the best our knowledge, the intensity dynamics of such lasers for the first time. This paper provides some new research basis for understanding the establishment process of dispersion-tuned swept-fiber lasers and their potential application in the future.In this paper, we studied the dynamics of a dispersion-tuned swept-fiber laser both experimentally and theoretically. By adding a dispersion compensation fiber and an electro-optic modulator in the laser cavity, an actively mode-locked laser was obtained by using intensity modulation, and wavelength sweeping was realized by changing the modulation frequency. Using a high-speed real-time oscilloscope, the dynamic behaviors of the swept laser were investigated during wavelength switching, static-sweeping cycle, and continuous sweeping, respectively. It was found that the laser generates relaxation oscillation at the start of the sweeping mode. The relaxation oscillation process lasted for about 0.7 ms, and then the laser started to operate stably. Due to the nonlinear effect, new wavelengths were generated in the relaxation oscillation process, which is not beneficial for applications. Fortunately, relaxation oscillation disappears if the laser starts up and operates in the continuous sweeping mode, and the good sweeping symmetry between the positive sweep and negative sweep increases the application potential of the laser. In addition, the instantaneous linewidth is almost the same as that in the static state. These results describe the characteristics of the laser from a new perspective and reveal, to the best our knowledge, the intensity dynamics of such lasers for the first time. This paper provides some new research basis for understanding the establishment process of dispersion-tuned swept-fiber lasers and their potential application in the future..
Photonics Research
- Publication Date: May. 19, 2023
- Vol. 11, Issue 6, 999 (2023)
Nanophotonics and Photonic Crystals
Transport of a topologically protected photonic waveguide on-chip
Sai Yan, Jingnan Yang, Shushu Shi, Zhanchun Zuo, Can Wang, and Xiulai Xu
We propose a design on integrated optical devices on-chip with an extra width degree of freedom by using a photonic crystal waveguide with Dirac points between two photonic crystals with opposite valley Chern numbers. With such an extra waveguide, we demonstrate numerically that the topologically protected photonic waveguide retains properties of valley-locking and immunity to defects. Due to the design flexibility of the width-tunable topologically protected photonic waveguide, many unique on-chip integrated devices have been proposed, such as energy concentrators with a concentration efficiency improvement of more than one order of magnitude, and a topological photonic power splitter with an arbitrary power splitting ratio. The topologically protected photonic waveguide with the width degree of freedom could be beneficial for scaling up photonic devices, and provides a flexible platform to implement integrated photonic networks on-chip.We propose a design on integrated optical devices on-chip with an extra width degree of freedom by using a photonic crystal waveguide with Dirac points between two photonic crystals with opposite valley Chern numbers. With such an extra waveguide, we demonstrate numerically that the topologically protected photonic waveguide retains properties of valley-locking and immunity to defects. Due to the design flexibility of the width-tunable topologically protected photonic waveguide, many unique on-chip integrated devices have been proposed, such as energy concentrators with a concentration efficiency improvement of more than one order of magnitude, and a topological photonic power splitter with an arbitrary power splitting ratio. The topologically protected photonic waveguide with the width degree of freedom could be beneficial for scaling up photonic devices, and provides a flexible platform to implement integrated photonic networks on-chip..
Photonics Research
- Publication Date: May. 26, 2023
- Vol. 11, Issue 6, 1021 (2023)
Manipulation of polarization topology using a Fabry–Pérot fiber cavity with a higher-order mode optical nanofiber
Maki Maeda, Jameesh Keloth, and Síle Nic Chormaic
Optical nanofiber cavity research has mainly focused on the fundamental mode. Here, a Fabry–Pérot fiber cavity with an optical nanofiber supporting the higher-order modes (TE01, TM01, HE21o, and HE21e) is demonstrated. Using cavity spectroscopy, with mode imaging and analysis, we observed cavity resonances that exhibited complex, inhomogeneous states of polarization with topological features containing Stokes singularities such as C-points, Poincaré vortices, and L-lines. In situ tuning of the intracavity birefringence enabled the desired profile and polarization of the cavity mode to be obtained. We believe these findings open new research possibilities for cold atom manipulation and multimode cavity quantum electrodynamics using the evanescent fields of higher-order mode optical nanofibers.Optical nanofiber cavity research has mainly focused on the fundamental mode. Here, a Fabry–Pérot fiber cavity with an optical nanofiber supporting the higher-order modes (
Photonics Research
- Publication Date: May. 26, 2023
- Vol. 11, Issue 6, 1029 (2023)
Leaky cavity modes in metasurfaces: a route to low-loss wideband anomalous dispersion
Xiaofeng Wang, Jiafu Wang, Yajuan Han, Mingbao Yan, Yongfeng Li, Tonghao Liu, Hua Ma, and Shaobo Qu
Metasurfaces have provided unprecedented degrees of freedom in manipulating electromagnetic waves upon interfaces. In this work, we first explore the condition of wide operating bandwidth in the view of reflective scheme, which indicates the necessity of anomalous dispersion. To this end, the leaky cavity modes (LCMs) in the meta-atom are analyzed and can make effective permittivity inversely proportional to frequency. Here we employ the longitudinal Fabry–Perot (F-P) resonances and transverse plasmonic resonances to improve the LCMs efficiency. It is shown that the order of F-P resonance can be customized by the plasmonic modes, that is, the F-P cavity propagation phase should match the phase delay of surface currents excited on the meta-atom. The nth order F-P resonance will multiply the permittivity by a factor of n, allowing larger phase accumulation with increasing frequencies and forming nonlinear phase distribution which can be applied in weak chromatic-aberration focusing design. As a proof-of-concept, we demonstrate a planar weak chromatic-aberration focusing reflector with a thickness of λ0/9 at 16.0–21.0 GHz. This work paves a robust way to advanced functional materials with anomalous dispersion and can be extended to higher frequencies such as terahertz, infrared, and optical frequencies.Metasurfaces have provided unprecedented degrees of freedom in manipulating electromagnetic waves upon interfaces. In this work, we first explore the condition of wide operating bandwidth in the view of reflective scheme, which indicates the necessity of anomalous dispersion. To this end, the leaky cavity modes (LCMs) in the meta-atom are analyzed and can make effective permittivity inversely proportional to frequency. Here we employ the longitudinal Fabry–Perot (F-P) resonances and transverse plasmonic resonances to improve the LCMs efficiency. It is shown that the order of F-P resonance can be customized by the plasmonic modes, that is, the F-P cavity propagation phase should match the phase delay of surface currents excited on the meta-atom. The
Photonics Research
- Publication Date: May. 30, 2023
- Vol. 11, Issue 6, 1085 (2023)
Topological large-area one-way transmission in pseudospin-field-dependent waveguides using magneto-optical photonic crystals | Editors' Pick
Xinyue Yu, Jianfeng Chen, Zhi-Yuan Li, and Wenyao Liang
We propose a pseudospin-field-dependent waveguide (PFDW) by constructing a sandwiched heterostructure consisting of three magneto-optical photonic crystals (MOPCs) with different geometric parameters. The upper expanded MOPC applied with an external magnetic field has broken time-reversal symmetry (TRS) and an analogous quantum spin Hall (QSH) effect, while the middle standard and the lower compressed ones are not magnetized and trivial. Attributed to the TRS-broken-QSH effect of the upper MOPC, the topological large-area one-way transmission that uniformly distributes over the middle domain is achieved and exhibits the characteristics of a pseudospin-field-momentum-locking; i.e., pseudospin-down (or pseudospin-up) leftward (or rightward) waveguide state when the positive (or negative) magnetic field is applied on the upper MOPC. We further demonstrate the strong robustness of the PFDW against backscattering from various kinds of defects. In addition, a topological beam modulator that can compress or expand the light beam, and a large-area pseudospin beam splitter have been designed. These results have potential in various applications such as sensing, signal processing, and optical communications.We propose a pseudospin-field-dependent waveguide (PFDW) by constructing a sandwiched heterostructure consisting of three magneto-optical photonic crystals (MOPCs) with different geometric parameters. The upper expanded MOPC applied with an external magnetic field has broken time-reversal symmetry (TRS) and an analogous quantum spin Hall (QSH) effect, while the middle standard and the lower compressed ones are not magnetized and trivial. Attributed to the TRS-broken-QSH effect of the upper MOPC, the topological large-area one-way transmission that uniformly distributes over the middle domain is achieved and exhibits the characteristics of a pseudospin-field-momentum-locking; i.e., pseudospin-down (or pseudospin-up) leftward (or rightward) waveguide state when the positive (or negative) magnetic field is applied on the upper MOPC. We further demonstrate the strong robustness of the PFDW against backscattering from various kinds of defects. In addition, a topological beam modulator that can compress or expand the light beam, and a large-area pseudospin beam splitter have been designed. These results have potential in various applications such as sensing, signal processing, and optical communications..
Photonics Research
- Publication Date: May. 30, 2023
- Vol. 11, Issue 6, 1105 (2023)
Nonlinear Optics
Hyperbolic resonant radiation of concomitant microcombs induced by cross-phase modulation
Yang Wang, Weiqiang Wang, Zhizhou Lu, Xinyu Wang, Long Huang, Brent E. Little, Sai T. Chu, Wei Zhao, and Wenfu Zhang
A high-quality optical microcavity can enhance optical nonlinear effects by resonant recirculation, which provides a reliable platform for nonlinear optics research. When a soliton microcomb and a probe optical field are coexisting in a micro-resonator, a concomitant microcomb (CMC) induced by cross-phase modulation (XPM) will be formed synchronously. Here, we characterize the CMC comprehensively in a micro-resonator through theory, numerical simulation, and experimental verification. It is found that the CMCs spectra are modulated due to resonant radiation (RR) resulting from the interaction of dispersion and XPM effects. The group velocity dispersion induces symmetric RRs on the CMC, which leads to a symmetric spectral envelope and a dual-peak pulse in frequency and temporal domains, respectively, while the group velocity mismatch breaks the symmetry of RRs and leads to asymmetric spectral and temporal profiles. When the group velocity is linearly varying with frequency, two RR frequencies are hyperbolically distributed about the pump, and the probe light acts as one of the asymptotic lines. Our results enrich the CMC dynamics and guide microcomb design and applications such as spectral extension and dark pulse generation.A high-quality optical microcavity can enhance optical nonlinear effects by resonant recirculation, which provides a reliable platform for nonlinear optics research. When a soliton microcomb and a probe optical field are coexisting in a micro-resonator, a concomitant microcomb (CMC) induced by cross-phase modulation (XPM) will be formed synchronously. Here, we characterize the CMC comprehensively in a micro-resonator through theory, numerical simulation, and experimental verification. It is found that the CMCs spectra are modulated due to resonant radiation (RR) resulting from the interaction of dispersion and XPM effects. The group velocity dispersion induces symmetric RRs on the CMC, which leads to a symmetric spectral envelope and a dual-peak pulse in frequency and temporal domains, respectively, while the group velocity mismatch breaks the symmetry of RRs and leads to asymmetric spectral and temporal profiles. When the group velocity is linearly varying with frequency, two RR frequencies are hyperbolically distributed about the pump, and the probe light acts as one of the asymptotic lines. Our results enrich the CMC dynamics and guide microcomb design and applications such as spectral extension and dark pulse generation..
Photonics Research
- Publication Date: May. 30, 2023
- Vol. 11, Issue 6, 1075 (2023)
Optical and Photonic Materials
Blue perovskite single-mode lasing in a rubidium lead bromide microcubic cavity
Bo Li, Wangqi Mao, Shuang Liang, Yifeng Shi, Hongxing Dong, and Long Zhang
Lead halide perovskite microlasers have shown impressive performance in the green and red wavebands. However, there has been limited progress in achieving blue-emitting perovskite microlasers. Here, blue-emitting perovskite-phase rubidium lead bromide (RbPbBr3) microcubes were successfully prepared by using a one-step chemical vapor deposition process, which can be utilized to construct optically pumped whispering gallery mode microlasers. By regulating the growth temperature, we found that a high-temperature environment can facilitate the formation of the perovskite phase and microcubic morphology of RbPbBr3. Notably, blue single-mode lasing in a RbPbBr3 microcubic cavity with a narrow linewidth of 0.21 nm and a high-quality factor (∼2200) was achieved. The obtained lasing from RbPbBr3 microlasers also exhibited an excellent polarization state factor (∼0.77). By modulating the mixed-monovalent cation composition, the wavelength of the microlaser could be tuned from green (536 nm) to pure blue (468 nm). Additionally, the heat stability of the mix-cation perovskite was better than that of conventional CsPbBr3. The stable and high-performance blue single-mode microlasers may thus facilitate the application of perovskite lasers in blue laser fields.Lead halide perovskite microlasers have shown impressive performance in the green and red wavebands. However, there has been limited progress in achieving blue-emitting perovskite microlasers. Here, blue-emitting perovskite-phase rubidium lead bromide (
Photonics Research
- Publication Date: May. 30, 2023
- Vol. 11, Issue 6, 1067 (2023)
Physical Optics
Polarization singularities in planar electromagnetic resonators with rotation and mirror symmetries
Jie Yang, Xuezhi Zheng, Jiafu Wang, Anxue Zhang, Tie Jun Cui, and Guy A. E. Vandenbosch
In this work, we apply the group representation theory to systematically study polarization singularities in the in-plane components of the electric fields supported by a planar electromagnetic (EM) resonator with generic rotation and reflection symmetries. We reveal the intrinsic connections between the symmetries and the topological features, i.e., the spatial configuration of the in-plane fields and the associated polarization singularities. The connections are substantiated by a simple relation that links the topological charges of the singularities and the symmetries of the resonator. To verify, a microwave planar resonator with the D8 group symmetries is designed and numerically simulated, which demonstrates the theoretical findings well. Our discussions can be applied to generic EM resonators working in a wide EM spectrum, such as circular antenna arrays, microring resonators, and photonic quasi-crystals, and provide a unique symmetry perspective on many effects in singular optics and topological photonics.In this work, we apply the group representation theory to systematically study polarization singularities in the in-plane components of the electric fields supported by a planar electromagnetic (EM) resonator with generic rotation and reflection symmetries. We reveal the intrinsic connections between the symmetries and the topological features, i.e., the spatial configuration of the in-plane fields and the associated polarization singularities. The connections are substantiated by a simple relation that links the topological charges of the singularities and the symmetries of the resonator. To verify, a microwave planar resonator with the
Photonics Research
- Publication Date: May. 16, 2023
- Vol. 11, Issue 6, 936 (2023)
Quantum Optics
High-speed integrated QKD system
Rebecka Sax, Alberto Boaron, Gianluca Boso, Simone Atzeni, Andrea Crespi, Fadri Grünenfelder, Davide Rusca, Aws Al-Saadi, Danilo Bronzi, Sebastian Kupijai, Hanjo Rhee, Roberto Osellame, and Hugo Zbinden
Quantum key distribution (QKD) is nowadays a well-established method for generating secret keys at a distance in an information-theoretically secure way, as the secrecy of QKD relies on the laws of quantum physics and not on computational complexity. In order to industrialize QKD, low-cost, mass-manufactured, and practical QKD setups are required. Hence, photonic and electronic integration of the sender’s and receiver’s respective components is currently in the spotlight. Here we present a high-speed (2.5 GHz) integrated QKD setup featuring a transmitter chip in silicon photonics allowing for high-speed modulation and accurate state preparation, as well as a polarization-independent low-loss receiver chip in aluminum borosilicate glass fabricated by the femtosecond laser micromachining technique. Our system achieves raw bit error rates, quantum bit error rates, and secret key rates equivalent to a much more complex state-of-the-art setup based on discrete components [BoaronA.et al., Phys. Rev. Lett.121, 190502 (2018)].Quantum key distribution (QKD) is nowadays a well-established method for generating secret keys at a distance in an information-theoretically secure way, as the secrecy of QKD relies on the laws of quantum physics and not on computational complexity. In order to industrialize QKD, low-cost, mass-manufactured, and practical QKD setups are required. Hence, photonic and electronic integration of the sender’s and receiver’s respective components is currently in the spotlight. Here we present a high-speed (2.5 GHz) integrated QKD setup featuring a transmitter chip in silicon photonics allowing for high-speed modulation and accurate state preparation, as well as a polarization-independent low-loss receiver chip in aluminum borosilicate glass fabricated by the femtosecond laser micromachining technique. Our system achieves raw bit error rates, quantum bit error rates, and secret key rates equivalent to a much more complex state-of-the-art setup based on discrete components [Boaron A. et al. Phys. Rev. Lett. 121 , 190502 (2018 )
Photonics Research
- Publication Date: May. 25, 2023
- Vol. 11, Issue 6, 1007 (2023)
Surpassing the classical limit of the microwave photonic frequency fading effect by quantum microwave photonics
Yaqing Jin, Ye Yang, Huibo Hong, Xiao Xiang, Run'ai Quan, Tao Liu, Ninghua Zhu, Ming Li, Shougang Zhang, and Ruifang Dong
With energy–time entangled biphoton sources as the optical carrier and time-correlated single-photon detection for high-speed radio frequency (RF) signal recovery, the method of quantum microwave photonics (QMWP) has presented the unprecedented potential of nonlocal RF signal encoding and efficient RF signal distilling from the dispersion interference associated with ultrashort pulse carriers. In this paper, its capability in microwave signal processing and prospective superiority are further demonstrated. Both QMWP RF phase shifting and transversal filtering functionality, which are the fundamental building blocks of microwave signal processing, are realized. Besides good immunity to the dispersion-induced frequency fading effect associated with the broadband carrier in classical MWP, a native two-dimensional parallel microwave signal processor is provided. These results well demonstrate the superiority of QMWP over classical MWP and open the door to new application fields of MWP involving encrypted processing.With energy–time entangled biphoton sources as the optical carrier and time-correlated single-photon detection for high-speed radio frequency (RF) signal recovery, the method of quantum microwave photonics (QMWP) has presented the unprecedented potential of nonlocal RF signal encoding and efficient RF signal distilling from the dispersion interference associated with ultrashort pulse carriers. In this paper, its capability in microwave signal processing and prospective superiority are further demonstrated. Both QMWP RF phase shifting and transversal filtering functionality, which are the fundamental building blocks of microwave signal processing, are realized. Besides good immunity to the dispersion-induced frequency fading effect associated with the broadband carrier in classical MWP, a native two-dimensional parallel microwave signal processor is provided. These results well demonstrate the superiority of QMWP over classical MWP and open the door to new application fields of MWP involving encrypted processing..
Photonics Research
- Publication Date: May. 30, 2023
- Vol. 11, Issue 6, 1094 (2023)
Silicon Photonics
Inverse design of a Si-based high-performance vertical-emitting meta-grating coupler on a 220 nm silicon-on-insulator platform
Jinhyeong Yoon, Jae-Yong Kim, Junhyeong Kim, Hyeonho Yoon, Berkay Neşeli, Hyo-Hoon Park, and Hamza Kurt
Efficient extraction of light from a high refractive index silicon waveguide out of a chip is difficult to achieve. An inverse design approach was employed using the particle swarm optimization method to attain a vertical emitting meta-grating coupler with high coupling efficiency in a 220-nm-thick silicon-on-insulator platform. By carefully selecting the figure of merit and appropriately defining parameter space, unique L-shape and U-shape grating elements that boosted the out-of-plane radiation of light were obtained. In addition, a 65.7% (-1.82 dB) outcoupling efficiency and a 60.2% (-2.2 dB) fiber-to-chip vertical coupling efficiency with an 88 nm 3 dB bandwidth were demonstrated by numerical simulation. Considering fabrication constraints, the optimized complex meta-grating coupler was modified to correspond to two etching steps and was then fabricated with a complementary metal-oxide-semiconductor-compatible process. The modified meta-grating coupler exhibited a simulated coupling efficiency of 57.5% (-2.4 dB) with a 74 nm 3-dB bandwidth in the C-band and an experimentally measured coupling efficiency of 38% (-4.2 dB).Efficient extraction of light from a high refractive index silicon waveguide out of a chip is difficult to achieve. An inverse design approach was employed using the particle swarm optimization method to attain a vertical emitting meta-grating coupler with high coupling efficiency in a 220-nm-thick silicon-on-insulator platform. By carefully selecting the figure of merit and appropriately defining parameter space, unique L-shape and U-shape grating elements that boosted the out-of-plane radiation of light were obtained. In addition, a 65.7% (
Photonics Research
- Publication Date: May. 04, 2023
- Vol. 11, Issue 6, 897 (2023)
Surface Optics and Plasmonics
Complex-amplitude radiation-type metasurface enabling beamform-controlled energy allocation
Yongheng Mu, Cheng Pang, Yuzhong Wang, Qiming Wang, and Jiaran Qi
Fifth-generation (5G) communication requires spatial multiplexing multiple-input multiple-output systems with integrated hardware. With the increase in the number of users and emergence of the Internet of Things devices, complex beamforming devices have become particularly important in future wireless systems to meet different communication requirements, where independent amplitude and phase modulations are urgently required for integrated beamforming devices. Herein, by utilizing the constructive interference between multiple geometric-phase responses, the mathematical relation for decoupling amplitude and phase modulations in the radiation-type operational mode is derived. Based on this strategy, complex-amplitude radiation-type metasurfaces (RA-Ms) are implemented, with an integrated feeding network. Such metasurfaces exploit full 2π phase modulation and tailorable radiation amplitude in the circular polarization state. Meanwhile, a complex-amplitude retrieval method is developed to design the RA-Ms, enabling precise beamforming performances. On this basis, several functional devices based on the complex-amplitude RA-Ms, including energy-allocable multi-router, shape-editable beam generator, and complex beamformer, are demonstrated in the microwave region. The amplitude-phase decoupling mechanism with the retrieval method merges amplitude and phase modulations, and energy distribution into one compact and integrated electromagnetic component and may find applications in multi-target detection, 5G mobile communication, and short-range ground-to-sea radar.Fifth-generation (5G) communication requires spatial multiplexing multiple-input multiple-output systems with integrated hardware. With the increase in the number of users and emergence of the Internet of Things devices, complex beamforming devices have become particularly important in future wireless systems to meet different communication requirements, where independent amplitude and phase modulations are urgently required for integrated beamforming devices. Herein, by utilizing the constructive interference between multiple geometric-phase responses, the mathematical relation for decoupling amplitude and phase modulations in the radiation-type operational mode is derived. Based on this strategy, complex-amplitude radiation-type metasurfaces (RA-Ms) are implemented, with an integrated feeding network. Such metasurfaces exploit full
Photonics Research
- Publication Date: May. 18, 2023
- Vol. 11, Issue 6, 986 (2023)
Six-channel programmable coding metasurface simultaneously for orthogonal circular and linear polarizations
Tonghao Liu, Yueyu Meng, Jiafu Wang, Hua Ma, Ruichao Zhu, Chao Liu, Weihan Li, Zuntian Chu, Sai Sui, Tianshuo Qiu, Wenxuan Tang, and Shaobo Qu
Metasurfaces have intrigued long-standing research interests and developed multitudinous compelling applications owing to their unprecedented capability for manipulating electromagnetic waves, and the emerging programmable coding metasurfaces (PCMs) provide a real-time reconfigurable platform to dynamically implement customized functions. Nevertheless, most existing PCMs can only act on the single polarization state or perform in the limited polarization channel, which immensely restricts their practical application in multitask intelligent metadevices. Herein, an appealing strategy of the PCM is proposed to realize tunable functions in co-polarized reflection channels of orthogonal circularly polarized waves and in co-polarized and cross-polarized reflection channels of orthogonal linearly polarized waves from 9.0 to 10.5 GHz. In the above six channels, the spin-decoupled programmable meta-atom can achieve high-efficiency reflection and 1-bit digital phase modulation by selecting the specific ON/OFF states of two diodes, and the phase coding sequence of the PCM is dynamically regulated by the field-programmable gate array to generate the desired function. A proof-of-concept prototype is constructed to verify the feasibility of our methodology, and numerous simulation and experimental results are in excellent agreement with the theoretical predictions. This inspiring design opens a new avenue for constructing intelligent metasurfaces with higher serviceability and flexibility, and has tremendous application potential in communication, sensing, and other multifunctional smart metadevices.Metasurfaces have intrigued long-standing research interests and developed multitudinous compelling applications owing to their unprecedented capability for manipulating electromagnetic waves, and the emerging programmable coding metasurfaces (PCMs) provide a real-time reconfigurable platform to dynamically implement customized functions. Nevertheless, most existing PCMs can only act on the single polarization state or perform in the limited polarization channel, which immensely restricts their practical application in multitask intelligent metadevices. Herein, an appealing strategy of the PCM is proposed to realize tunable functions in co-polarized reflection channels of orthogonal circularly polarized waves and in co-polarized and cross-polarized reflection channels of orthogonal linearly polarized waves from 9.0 to 10.5 GHz. In the above six channels, the spin-decoupled programmable meta-atom can achieve high-efficiency reflection and 1-bit digital phase modulation by selecting the specific ON/OFF states of two diodes, and the phase coding sequence of the PCM is dynamically regulated by the field-programmable gate array to generate the desired function. A proof-of-concept prototype is constructed to verify the feasibility of our methodology, and numerous simulation and experimental results are in excellent agreement with the theoretical predictions. This inspiring design opens a new avenue for constructing intelligent metasurfaces with higher serviceability and flexibility, and has tremendous application potential in communication, sensing, and other multifunctional smart metadevices..
Photonics Research
- Publication Date: May. 26, 2023
- Vol. 11, Issue 6, 1047 (2023)
Ultrafast Optics
Impact of laser chirp on the polarization of terahertz from two-color plasma
Sen Mou, Luca Tomarchio, Annalisa D’Arco, Marta Di Fabrizio, Salvatore Macis, Alessandro Curcio, Luigi Palumbo, Stefano Lupi, and Massimo Petrarca
Two-color plasma, induced by two lasers of different colors, can radiate ultra-broadband and intense terahertz (THz) pulses, which is desirable in many technological and scientific applications. It was found that the polarization of the emitted THz depends on the phase difference between the fundamental laser wave and its second harmonic. Recent investigation suggests that chirp-induced change of pulse overlap plays an important role in the THz yield from two-color plasma. However, the effect of laser chirp on THz polarization remains unexplored. Hereby, we investigate the impact of laser chirp on THz polarization. It is unveiled that the chirp-induced phase difference affects THz polarization. Besides, positive and negative chirps have opposite effects on the variation of the THz polarization versus the phase difference. The polarization of THz generated by a positively chirped pump laser rotates clockwise with an increasing phase difference, while it rotates anticlockwise when generated by a negatively chirped pump laser.Two-color plasma, induced by two lasers of different colors, can radiate ultra-broadband and intense terahertz (THz) pulses, which is desirable in many technological and scientific applications. It was found that the polarization of the emitted THz depends on the phase difference between the fundamental laser wave and its second harmonic. Recent investigation suggests that chirp-induced change of pulse overlap plays an important role in the THz yield from two-color plasma. However, the effect of laser chirp on THz polarization remains unexplored. Hereby, we investigate the impact of laser chirp on THz polarization. It is unveiled that the chirp-induced phase difference affects THz polarization. Besides, positive and negative chirps have opposite effects on the variation of the THz polarization versus the phase difference. The polarization of THz generated by a positively chirped pump laser rotates clockwise with an increasing phase difference, while it rotates anticlockwise when generated by a negatively chirped pump laser..
Photonics Research
- Publication Date: May. 18, 2023
- Vol. 11, Issue 6, 978 (2023)
Promoting spintronic terahertz radiation via Tamm plasmon coupling | On the Cover
Yunqing Jiang, Hongqing Li, Xiaoqiang Zhang, Fan Zhang, Yong Xu, Yongguang Xiao, Fengguang Liu, Anting Wang, Qiwen Zhan, and Weisheng Zhao
Spectral fingerprint and terahertz (THz) field-induced carrier dynamics demands the exploration of broadband and intense THz signal sources. Spintronic THz emitters (STEs), with high stability, a low cost, and an ultrabroad bandwidth, have been a hot topic in the field of THz sources. One of the main barriers to their practical application is lack of an STE with strong radiation intensity. Here, through the combination of optical physics and ultrafast photonics, the Tamm plasmon coupling (TPC) facilitating THz radiation is realized between spin THz thin films and photonic crystal structures. Simulation results show that the spectral absorptance can be increased from 36.8% to 94.3% for spin THz thin films with TPC. This coupling with narrowband resonance not only improves the optical-to-spin conversion efficiency, but also guarantees THz transmission with a negligible loss (∼4%) for the photonic crystal structure. According to the simulation, we prepared this structure successfully and experimentally realized a 264% THz radiation enhancement. Furthermore, the spin THz thin films with TPC exhibited invariant absorptivity under different polarization modes of the pump beam and weakening confinement on an obliquely incident pump laser. This approach is easy to implement and offers possibilities to overcome compatibility issues between the optical structure design and low energy consumption for ultrafast THz opto-spintronics and other similar devices.Spectral fingerprint and terahertz (THz) field-induced carrier dynamics demands the exploration of broadband and intense THz signal sources. Spintronic THz emitters (STEs), with high stability, a low cost, and an ultrabroad bandwidth, have been a hot topic in the field of THz sources. One of the main barriers to their practical application is lack of an STE with strong radiation intensity. Here, through the combination of optical physics and ultrafast photonics, the Tamm plasmon coupling (TPC) facilitating THz radiation is realized between spin THz thin films and photonic crystal structures. Simulation results show that the spectral absorptance can be increased from 36.8% to 94.3% for spin THz thin films with TPC. This coupling with narrowband resonance not only improves the optical-to-spin conversion efficiency, but also guarantees THz transmission with a negligible loss (
Photonics Research
- Publication Date: May. 26, 2023
- Vol. 11, Issue 6, 1057 (2023)
About the Cover
By harnessing Tamm plasmon coupling, spintronics THz radiation not only achieved a 264% enhancement but guaranteed nearly lossless (~4%) THz transmission. This approach provides the compatible optical structure design and the low energy consumption for ultrafast opto-spintronics devices. See Yunqing Jiang et al., pp. 1057-1066.
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