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1 Issue (s), 10 Article (s)
Vol. 13, Iss.5—May.1, 2025 • pp: 1106-1199 Spec. pp:
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Research ArticlesVol. 13, Iss.5-May..1,2025
Holography, Gratings, and Diffraction
Intelligent tailoring of a broadband orbital angular momentum comb towards efficient optical convolutionShiyun Zhou, Lang Li, Yishu Wang, Liliang Gao, Zhichao Zhang, Chunqing Gao, and Shiyao Fu
Due to the high-dimensional characteristics of photon orbital angular momentum (OAM), a beam can carry multiple OAMs simultaneously thus forming an OAM comb, which has been proved to show significant potential in both classical and quantum photonics. Tailoring broadband OAM combs on demand in a fast and accurate manner is a crucial basis for their application in advanced scenarios. However, obtaining phase-only gratings for the generation of arbitrary desired OAM combs still poses challenges. In this paper, we propose a multi-scale fusion learning U-shaped neural network that encodes a phase-only hologram for tailoring broadband OAM combs on-demand. Proof-of-principle experiments demonstrate that our scheme achieves fast computational speed, high modulation precision, and high manipulation dimensionality, with a mode range of
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1148 (2025)
Instrumentation and Measurements
Ultrafast ranging using a dispersion-controlled dual-swept laserWei Du, Lei Chen, Yujia Li, Jindong Wang, Yulong Cao, Ligang Huang, Leilei Shi, Lei Gao, Lei Wei, and Tao Zhu
Ranging is indispensable in a variety of fields, encompassing basic science, manufacturing, production, and daily life. Although traditional methods based on the dispersive interferometry (DPI) in the frequency domain provide high precision, their measurement speed is slow, preventing the capture and measurement of dynamic displacements. Here, we propose a fast and precise ranging method based on the dispersion-controlled dual-swept laser (DCDSL), which allows the dynamical displacement measurement of the target under test. Due to the slight frequency sweeping speed difference between the signal and reference lights, there is a zero-frequency point of the oscillation (ZPO) generated in the interference signal, whose position in the time domain is linearly related to the relative delay between the signal and reference lights. Utilizing phase demodulation of the interference signal from the DCDSL and the fitting algorithm, the time-domain position of ZPO is accurately found, which precisely maps to the displacement of the target in real time without direction ambiguity. The fast frequency sweeping rate ensures fast ranging with the MHz order refresh frame. We have experimentally demonstrated its capabilities for precise measurement of static distances and the capture of dynamic displacement processes through simulations and experiments, with the measurement range encompassing the entire interference period (56 mm). Compared to a calibrated motorized displacement platform, the residual error for full-range distance measurements is within 10 μm, and the error in average speed during dynamic processes is 0.46%. Additionally, the system exhibits excellent stability, achieving a minimum Allan deviation of 4.25 nm over an average duration of approximately 4 ms. This method ensures high precision while maintaining a simple system, thereby advancing the practical implementation of ultrafast length metrology.Ranging is indispensable in a variety of fields, encompassing basic science, manufacturing, production, and daily life. Although traditional methods based on the dispersive interferometry (DPI) in the frequency domain provide high precision, their measurement speed is slow, preventing the capture and measurement of dynamic displacements. Here, we propose a fast and precise ranging method based on the dispersion-controlled dual-swept laser (DCDSL), which allows the dynamical displacement measurement of the target under test. Due to the slight frequency sweeping speed difference between the signal and reference lights, there is a zero-frequency point of the oscillation (ZPO) generated in the interference signal, whose position in the time domain is linearly related to the relative delay between the signal and reference lights. Utilizing phase demodulation of the interference signal from the DCDSL and the fitting algorithm, the time-domain position of ZPO is accurately found, which precisely maps to the displacement of the target in real time without direction ambiguity. The fast frequency sweeping rate ensures fast ranging with the MHz order refresh frame. We have experimentally demonstrated its capabilities for precise measurement of static distances and the capture of dynamic displacement processes through simulations and experiments, with the measurement range encompassing the entire interference period (56 mm). Compared to a calibrated motorized displacement platform, the residual error for full-range distance measurements is within 10 μm, and the error in average speed during dynamic processes is 0.46%. Additionally, the system exhibits excellent stability, achieving a minimum Allan deviation of 4.25 nm over an average duration of approximately 4 ms. This method ensures high precision while maintaining a simple system, thereby advancing the practical implementation of ultrafast length metrology.
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1182 (2025)
Lasers and Laser Optics
Unveiling intracavity soliton evolution dynamics of a mode-locked fiber laser along the dispersion mapJiarun Zhang, Tianchang Lu, Xiankun Yao, Yusheng Zhang, Dong Mao, Chao Zeng, Xiang Hao, Longhua Tang, Yudong Cui, Cuifang Kuang, and Xu Liu
Mode-locked fiber lasers are excellent platforms for soliton generation. Solitons exhibit distinct distribution and evolution characteristics depending on the net dispersion of the laser cavity. Here we propose an experimental scheme to reconstruct the intracavity dynamics of solitons within a mode-locked fiber laser. The proposed scheme is facilitated by disposing multiple output ports at different positions throughout the cavity, thereby enabling in-depth observation and manipulation of soliton evolution along the dispersion map. The experimental results verify corresponding simulations and explain some phenomena from the perspective of soliton evolution. Our results offer a pathway for comprehensive analyses of intracavity pulse dynamics, fostering advancements in nonlinear and ultrafast optics.Mode-locked fiber lasers are excellent platforms for soliton generation. Solitons exhibit distinct distribution and evolution characteristics depending on the net dispersion of the laser cavity. Here we propose an experimental scheme to reconstruct the intracavity dynamics of solitons within a mode-locked fiber laser. The proposed scheme is facilitated by disposing multiple output ports at different positions throughout the cavity, thereby enabling in-depth observation and manipulation of soliton evolution along the dispersion map. The experimental results verify corresponding simulations and explain some phenomena from the perspective of soliton evolution. Our results offer a pathway for comprehensive analyses of intracavity pulse dynamics, fostering advancements in nonlinear and ultrafast optics.
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1130 (2025)
Lasers and Laser Optics
All-fiber-structure high-power mid-infrared gas-filled hollow-core-fiber amplified spontaneous emission sourceWeihua Song, Yu Wen, Qian Zhang, Xin Zhang, and Pu Wang
Hollow-core-fiber (HCF) gas lasers (GLs) have garnered significant interest as a novel approach for generating mid-infrared lasers, owing to their inherent benefits of rich emission wavelength, high beam quality, and high output power potential. However, they are mostly achieved by a free-space coupling structure, which has a major drawback of being prone to vibrations and other environmental variations. Here, we devise and implement an all-fiber-structure gas-filled HCF amplified spontaneous emission (ASE) source at 3.1 μm based on the reverse tapering and angle-cleaved fusion splicing techniques. By optimizing the
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1137 (2025)
Nonlinear Optics
Towards high-power and ultra-broadband mid-infrared supercontinuum generation using tapered multimode glass rodsEsteban Serrano, Damien Bailleul, Frédéric Désévédavy, Pierre Béjot, Grégory Gadret, Pierre Mathey, Frédéric Smektala, and Bertrand Kibler
Simultaneously increasing the spectral bandwidth and average output power of mid-infrared supercontinuum sources remains a major challenge for their practical application. We particularly address this issue for the long mid-infrared spectral region through experimental developments of short tapered rods made from selenide glass by means of supercontinuum generation in the femtosecond regime. Our simple post-processing of glass rods unlocks potentially higher-power and coherent fiber-based supercontinuum sources beyond the 10-μm waveband. By using a 5-cm-long tapered Ge-Se-Te rod pumped at 6 μm, a supercontinuum spanning from 2 to 15 μm (3–14 μm) with an average output power of 93 mW (170 mW) is obtained for 500-kHz (1-MHz) repetition rate. Additional experiments on other glass families (silica and tellurite) covering distinct spectral regions are also reported to develop and support our analyses. We demonstrate that ultra-broadband spectral broadenings over entire glass transmission windows can be achieved in few-cm-long segments of tapered rods by a fine adjustment of input modal excitation. Numerical simulations are used to confirm the main contribution of the fundamental mode in the ultrafast nonlinear dynamics, as well as the possible preservation of coherence features. Our study opens a new route, to our knowledge, towards the power scaling of high-repetition-rate fiber supercontinuum sources over the full molecular fingerprint region.Simultaneously increasing the spectral bandwidth and average output power of mid-infrared supercontinuum sources remains a major challenge for their practical application. We particularly address this issue for the long mid-infrared spectral region through experimental developments of short tapered rods made from selenide glass by means of supercontinuum generation in the femtosecond regime. Our simple post-processing of glass rods unlocks potentially higher-power and coherent fiber-based supercontinuum sources beyond the 10-μm waveband. By using a 5-cm-long tapered Ge-Se-Te rod pumped at 6 μm, a supercontinuum spanning from 2 to 15 μm (3–14 μm) with an average output power of 93 mW (170 mW) is obtained for 500-kHz (1-MHz) repetition rate. Additional experiments on other glass families (silica and tellurite) covering distinct spectral regions are also reported to develop and support our analyses. We demonstrate that ultra-broadband spectral broadenings over entire glass transmission windows can be achieved in few-cm-long segments of tapered rods by a fine adjustment of input modal excitation. Numerical simulations are used to confirm the main contribution of the fundamental mode in the ultrafast nonlinear dynamics, as well as the possible preservation of coherence features. Our study opens a new route, to our knowledge, towards the power scaling of high-repetition-rate fiber supercontinuum sources over the full molecular fingerprint region.
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1106 (2025)
Optical Devices
QBIC-based terahertz metasurface used for the detection of chlorpyrifos in teaTianqing Zhou, Binggang Xiao, Yong Du, and Jianyuan Qin
Pesticide residues in tea are an important problem affecting the sustainable development of the tea industry; thus, pesticide detection is the key to ensuring the quality and safety of tea. Here, a terahertz metasurface structure based on the quasi-bound state in the continuum is proposed, which consists of two copper microrods arranged periodically. This design in the metasurface provides strong local enhancement near the surface of the microstructure, significantly improving the interaction of light with the analyte, resulting in increased sensitivity. The simulated and experimental results show that the metasurface structure can be used to detect the refractive index of trace analytes with a high sensitivity and successfully detect low concentrations of chlorpyrifos in tea. This study provides a new idea for the detection of pesticide residues in tea.Pesticide residues in tea are an important problem affecting the sustainable development of the tea industry; thus, pesticide detection is the key to ensuring the quality and safety of tea. Here, a terahertz metasurface structure based on the quasi-bound state in the continuum is proposed, which consists of two copper microrods arranged periodically. This design in the metasurface provides strong local enhancement near the surface of the microstructure, significantly improving the interaction of light with the analyte, resulting in increased sensitivity. The simulated and experimental results show that the metasurface structure can be used to detect the refractive index of trace analytes with a high sensitivity and successfully detect low concentrations of chlorpyrifos in tea. This study provides a new idea for the detection of pesticide residues in tea.
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1158 (2025)
Optical Devices
Efficient inverse design for tailoring a terahertz metagratingJia Shi, Guanlong Wang, Shaona Wang, Wenjing Yu, Ling Liang, Weiling Fu, Pingjuan Niu, Jianquan Yao, and Xiang Yang
The fast and accurate design of terahertz devices for specific applications remains challenging, especially for tailoring metadevices, owing to the complex electromagnetic characteristics of these devices and their large structural parameter space. The unique functionalities achieved by metadevices come at the cost of structural complexity, resulting in a time-consuming parameter sweep for conventional metadevice design. Here, we propose a general solution to achieve efficient inverse design for a terahertz metagrating via machine learning. Metagratings with different structural parameters were selected as illustrations to verify the effectiveness of this method. As proof-of-principle examples, the metagratings predicted via the inverse design model are numerically calculated and experimentally demonstrated. Initially, the physical modeling of a metagrating is performed via the finite element method (FEM). A spectrum dataset obtained from FEM simulation is prepared for the training of machine learning models. Then, trained machine learning models, including the Elman neural network (Elman), support vector machine (SVM), and general regression neutral network (GRNN), are used to predict probable structural parameters. The results of these models are compared and analyzed comprehensively, which verifies the effectiveness of the inverse design method. Compared with conventional methods, the inverse design method is much faster and can encompass a high degree of freedom to generate metadevice structures, which can ensure that the spectra of generated structures resemble the desired ones and can provide accurate data support for metadevice modeling. Furthermore, a metagrating tailored by an inverse design is used as a biological sensor to distinguish different microorganisms. The proposed data-driven inverse design method realizes fast and accurate design of the metagrating, which is expected to have great potential in metadevice design and tailoring for specific applications.The fast and accurate design of terahertz devices for specific applications remains challenging, especially for tailoring metadevices, owing to the complex electromagnetic characteristics of these devices and their large structural parameter space. The unique functionalities achieved by metadevices come at the cost of structural complexity, resulting in a time-consuming parameter sweep for conventional metadevice design. Here, we propose a general solution to achieve efficient inverse design for a terahertz metagrating via machine learning. Metagratings with different structural parameters were selected as illustrations to verify the effectiveness of this method. As proof-of-principle examples, the metagratings predicted via the inverse design model are numerically calculated and experimentally demonstrated. Initially, the physical modeling of a metagrating is performed via the finite element method (FEM). A spectrum dataset obtained from FEM simulation is prepared for the training of machine learning models. Then, trained machine learning models, including the Elman neural network (Elman), support vector machine (SVM), and general regression neutral network (GRNN), are used to predict probable structural parameters. The results of these models are compared and analyzed comprehensively, which verifies the effectiveness of the inverse design method. Compared with conventional methods, the inverse design method is much faster and can encompass a high degree of freedom to generate metadevice structures, which can ensure that the spectra of generated structures resemble the desired ones and can provide accurate data support for metadevice modeling. Furthermore, a metagrating tailored by an inverse design is used as a biological sensor to distinguish different microorganisms. The proposed data-driven inverse design method realizes fast and accurate design of the metagrating, which is expected to have great potential in metadevice design and tailoring for specific applications.
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1172 (2025)
Surface Optics and Plasmonics
Twisted bilayer meta-device for on-demand terahertz polarization filteringHui Li, Chenhui Zhao, Wenhui Xu, Jie Li, Chenglong Zheng, Qi Tan, Chunyu Song, Hang Xu, Yun Shen, and Jianquan Yao
Moiré meta-devices facilitate continuous and precise modulation of optical properties through the alteration of the relative alignment, such as twisting, sliding, or rotating of the metasurfaces. This capability renders them particularly suitable for dynamic applications, including zoom optics and adaptive imaging systems. Nevertheless, such designs often sacrifice more complex functionalities, such as polarization manipulation, in favor of simplicity and tunability. Here, we propose and experimentally validate a design strategy for a twisted bilayer metasurface that exhibits both varifocal capabilities and polarization filtering properties. By selecting silicon pillars with polarization-maintaining properties for Layer I and polarization-converting properties for Layer II, the designed Moiré metasurface can become sensitive to specific polarization states. Experimental results demonstrate that the proposed design can generate on-demand terahertz (THz) focused beams, achieving an average focusing efficiency exceeding 35% under
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1116 (2025)
Surface Optics and Plasmonics
Two-dimensional anomalous reflection with high efficiency and arbitrary direction based on a low-profile wideband metasurfaceHuanhuan Gao, Xiaojun Huang, Zhengjie Wang, Xiongwei Ma, Wentao Li, Hui Wang, and He-Xiu Xu
The finding of Snell’s law for anomalous reflection enables broad applications of metasurfaces in stealth, communication, radar technology, etc. However, some unavoidable high-order modes are inherently generated due to the super lattice of this local approach, which thus causes a decrease in efficiency and a limit in the reflected angle. Here, a novel, to our knowledge, low-profile wideband reflective meta-atom shaped like a four-leaf rose is proposed to achieve a phase coverage of full 360° by varying the length of the rose leaf. Then, the genetic algorithm is adopted for the first time to encode and optimize the topology of each meta-atom on the coding metasurface to achieve two-dimensional (2D) anomalous reflection with excellent performances through an inverse design. Numerical results show that our optimized coding metasurfaces achieve a high-efficiency (
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1165 (2025)
Surface Optics and Plasmonics
Light-switchable polarization conversion via an optical-fiber-controlled metasurfaceYuxi Li, Ruichao Zhu, Sai Sui, Yajuan Han, Yuxiang Jia, Chang Ding, Shaojie Wang, Cunqian Feng, Shaobo Qu, and Jiafu Wang
A reconfigurable metasurface based on optical control provides a control paradigm for integrating multiple functions at the same aperture, which effectively expands the freedom of control. However, the traditional light control method requires the light source to directly illuminate the photosensitive device, which forces the metasurface to be placed only according to the light emitter position, and even to need to be integrated on the light emitter, limiting the application scenarios of light-controlled reconfigurable metasurfaces. In this work, a light control method based on optical fiber is proposed, which guides and controls the light propagation path through optical fiber. The metasurface can be flexibly deployed, breaking through the limitation of physical space. As a verification, photoresistors are embedded in the metasurface, and the active device is directly excited by the light source as a driving signal to realize the switching of a polarization conversion function. The experimental results show that the optical-fiber-controlled metasurface can achieve linear-to-linear polarization conversion in the light environment and linear-to-circular polarization conversion in the dark environment. This work paves a new way, to our knowledge, to achieve a light-controlled metasurface, which enriches the family of intelligent metasurfaces and has great potential in many fields.A reconfigurable metasurface based on optical control provides a control paradigm for integrating multiple functions at the same aperture, which effectively expands the freedom of control. However, the traditional light control method requires the light source to directly illuminate the photosensitive device, which forces the metasurface to be placed only according to the light emitter position, and even to need to be integrated on the light emitter, limiting the application scenarios of light-controlled reconfigurable metasurfaces. In this work, a light control method based on optical fiber is proposed, which guides and controls the light propagation path through optical fiber. The metasurface can be flexibly deployed, breaking through the limitation of physical space. As a verification, photoresistors are embedded in the metasurface, and the active device is directly excited by the light source as a driving signal to realize the switching of a polarization conversion function. The experimental results show that the optical-fiber-controlled metasurface can achieve linear-to-linear polarization conversion in the light environment and linear-to-circular polarization conversion in the dark environment. This work paves a new way, to our knowledge, to achieve a light-controlled metasurface, which enriches the family of intelligent metasurfaces and has great potential in many fields.
Photonics Research
- Publication Date: Apr. 21, 2025
- Vol. 13, Issue 5, 1191 (2025)
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