Contents
3 Issue (s), 23 Article (s)
Vol. 7, Iss.3—May.1, 2025 • pp: 036001-036001 Spec. pp:
Vol. 7, Iss.2—Mar.1, 2025 • pp: 025001-026006 Spec. pp:
Vol. 7, Iss.1—Jan.1, 2025 • pp: 010101-019901 Spec. pp:
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Vol. 7, Iss.3-May..1,2025
Research Articles
Exploring uncharted multiband hyperbolic dispersion in conjugated polymers: a first-principles studySuim Lim, Dong Hee Park, Bin Chan Joo, Yeon Ui Lee, and Kanghoon Yim
Hyperbolic materials are highly anisotropic optical media that provide valuable assistance in emission engineering, nanoscale light focusing, and scattering enhancement. Recently discovered organic hyperbolic materials (OHMs) with exceptional biocompatibility and tunability offer promising prospects as next-generation optical media for nanoscopy, enabling superresolution bioimaging capabilities. Nonetheless, an OHM is still less accessible to many researchers because of its rarity and narrow operating wavelength range. Here, we employ first-principles calculations to expand the number of known OHMs, including conjugated polymers with multiple assembly units. Through the systematic investigation of structural and optical properties of the target copolymers, we discover extraordinary multiband hyperbolic dispersions from candidate OHMs. This approach provides a new perspective on the molecular-scale design of broadband, low-loss OHMs. It aids in identifying potential hyperbolic material candidates applicable to optical engineering and super-resolution bioimaging, offering new insights into nanoscale light–matter interactions.Hyperbolic materials are highly anisotropic optical media that provide valuable assistance in emission engineering, nanoscale light focusing, and scattering enhancement. Recently discovered organic hyperbolic materials (OHMs) with exceptional biocompatibility and tunability offer promising prospects as next-generation optical media for nanoscopy, enabling superresolution bioimaging capabilities. Nonetheless, an OHM is still less accessible to many researchers because of its rarity and narrow operating wavelength range. Here, we employ first-principles calculations to expand the number of known OHMs, including conjugated polymers with multiple assembly units. Through the systematic investigation of structural and optical properties of the target copolymers, we discover extraordinary multiband hyperbolic dispersions from candidate OHMs. This approach provides a new perspective on the molecular-scale design of broadband, low-loss OHMs. It aids in identifying potential hyperbolic material candidates applicable to optical engineering and super-resolution bioimaging, offering new insights into nanoscale light–matter interactions.
Advanced Photonics
- Publication Date: Mar. 13, 2025
- Vol. 7, Issue 3, 036001 (2025)
Vol. 7, Iss.2-Mar..1,2025
Letters
Optical analog of black and white gravitational holesEric Plum, Anton N. Vetlugin, Baurzhan Salimzhanov, Nikolay I. Zheludev, and Nina Vaidya
In general relativity, a gravitational “white hole” is a hypothetical region of space that cannot be entered from outside. It is the reverse of a “black hole” from which light and information cannot escape. We report an optical device exhibiting intriguing similarities to these objects. It will either totally absorb (optical black hole) or totally reject (optical white hole) light of any wavelength, depending on its polarization. The device’s functionality is based on the formation of a standing wave from the wavefront of spatially coherent incident radiation. Interaction of the standing wave with a thin absorber enables coherent perfect absorption and transmission, whereas polarization sensitivity arises from the geometrical phase of the interfering beams. We provide experimental proof-of-principle demonstrations and show that the device operates as a black and white hole for orthogonal polarizations of the incident light. From a remote point, it will look similar to a gravitational black or white hole depending on the polarization of light. In principle, the optical black and white hole device can operate as a deterministic absorber or rejector throughout the entire electromagnetic spectrum. Broadband absorbers and rejectors can be useful for energy harvesting, detection, stealth technologies, and redistribution of light.In general relativity, a gravitational “white hole” is a hypothetical region of space that cannot be entered from outside. It is the reverse of a “black hole” from which light and information cannot escape. We report an optical device exhibiting intriguing similarities to these objects. It will either totally absorb (optical black hole) or totally reject (optical white hole) light of any wavelength, depending on its polarization. The device’s functionality is based on the formation of a standing wave from the wavefront of spatially coherent incident radiation. Interaction of the standing wave with a thin absorber enables coherent perfect absorption and transmission, whereas polarization sensitivity arises from the geometrical phase of the interfering beams. We provide experimental proof-of-principle demonstrations and show that the device operates as a black and white hole for orthogonal polarizations of the incident light. From a remote point, it will look similar to a gravitational black or white hole depending on the polarization of light. In principle, the optical black and white hole device can operate as a deterministic absorber or rejector throughout the entire electromagnetic spectrum. Broadband absorbers and rejectors can be useful for energy harvesting, detection, stealth technologies, and redistribution of light.
Advanced Photonics
- Publication Date: Feb. 27, 2025
- Vol. 7, Issue 2, 025001 (2025)
Research Articles
Single-shot volumetric fluorescence imaging with neural fieldsOumeng Zhang, Haowen Zhou, Brandon Y. Feng, Elin M. Larsson... and Changhuei Yang|Show fewer author(s)
Single-shot volumetric fluorescence (SVF) imaging offers a significant advantage over traditional imaging methods that require scanning across multiple axial planes, as it can capture biological processes with high temporal resolution. The key challenges in SVF imaging include requiring sparsity constraints, eliminating depth ambiguity in the reconstruction, and maintaining high resolution across a large field of view. We introduce the QuadraPol point spread function (PSF) combined with neural fields, an approach for SVF imaging. This method utilizes a custom polarizer at the back focal plane and a polarization camera to detect fluorescence, effectively encoding the three-dimensional scene within a compact PSF without depth ambiguity. In addition, we propose a reconstruction algorithm based on the neural field technique that provides improved reconstruction quality compared with classical deconvolution methods. QuadraPol PSF, combined with neural fields, significantly reduces the acquisition time of a conventional fluorescence microscope by ∼20 times and captures a 100-mm3 cubic volume in one shot. We validate the effectiveness of both our hardware and algorithm through all-in-focus imaging of bacterial colonies on sand surfaces and visualization of plant root morphology. Our approach offers a powerful tool for advancing biological research and ecological studies.Single-shot volumetric fluorescence (SVF) imaging offers a significant advantage over traditional imaging methods that require scanning across multiple axial planes, as it can capture biological processes with high temporal resolution. The key challenges in SVF imaging include requiring sparsity constraints, eliminating depth ambiguity in the reconstruction, and maintaining high resolution across a large field of view. We introduce the QuadraPol point spread function (PSF) combined with neural fields, an approach for SVF imaging. This method utilizes a custom polarizer at the back focal plane and a polarization camera to detect fluorescence, effectively encoding the three-dimensional scene within a compact PSF without depth ambiguity. In addition, we propose a reconstruction algorithm based on the neural field technique that provides improved reconstruction quality compared with classical deconvolution methods. QuadraPol PSF, combined with neural fields, significantly reduces the acquisition time of a conventional fluorescence microscope by ∼20 times and captures a 100-mm3 cubic volume in one shot. We validate the effectiveness of both our hardware and algorithm through all-in-focus imaging of bacterial colonies on sand surfaces and visualization of plant root morphology. Our approach offers a powerful tool for advancing biological research and ecological studies.
Advanced Photonics
- Publication Date: Feb. 25, 2025
- Vol. 7, Issue 2, 026001 (2025)
Research Articles
Attosecond time-resolved measurements of electron and photon beams with a variable polarization X-band radiofrequency deflector at an X-ray free-electron laserEduard Prat, Zheqiao Geng, Christoph Kittel, Alexander Malyzhenkov... and Paolo Craievich|Show fewer author(s)
X-ray free-electron lasers (FELs) are cutting-edge research instruments employed in multiple scientific fields capable of analyzing matter with unprecedented time and spatial resolutions. Time-resolved measurements of electron and photon beams are essential in X-ray FELs. Radiofrequency (RF) transverse deflecting structures (TDSs) with a fixed streaking direction are standard diagnostics to measure the temporal properties of the electron beams. If placed after the undulator of the FEL facility, TDSs can also be employed to reconstruct the power profile of the FEL pulses. We present measurements of an X-band RF TDS system with variable polarization with a resolution below one femtosecond. We show FEL power profile measurements with associated root mean square pulse durations as short as 300 attoseconds. The measurements have been carried out at Athos, the soft X-ray beamline of SwissFEL. Measurements with variable polarization and attosecond resolution are essential to characterize and optimize the electron beams in all its dimensions for all types of X-ray FEL experiments, in particular for ultrafast X-ray applications.X-ray free-electron lasers (FELs) are cutting-edge research instruments employed in multiple scientific fields capable of analyzing matter with unprecedented time and spatial resolutions. Time-resolved measurements of electron and photon beams are essential in X-ray FELs. Radiofrequency (RF) transverse deflecting structures (TDSs) with a fixed streaking direction are standard diagnostics to measure the temporal properties of the electron beams. If placed after the undulator of the FEL facility, TDSs can also be employed to reconstruct the power profile of the FEL pulses. We present measurements of an X-band RF TDS system with variable polarization with a resolution below one femtosecond. We show FEL power profile measurements with associated root mean square pulse durations as short as 300 attoseconds. The measurements have been carried out at Athos, the soft X-ray beamline of SwissFEL. Measurements with variable polarization and attosecond resolution are essential to characterize and optimize the electron beams in all its dimensions for all types of X-ray FEL experiments, in particular for ultrafast X-ray applications.
Advanced Photonics
- Publication Date: Feb. 27, 2025
- Vol. 7, Issue 2, 026002 (2025)
Research Articles
3D-printed micro-axicon enables extended depth-of-focus intravascular optical coherence tomography in vivoPavel Ruchka, Alok Kushwaha, Jessica A. Marathe, Lei Xiang... and Jiawen Li|Show fewer author(s)
A fundamental challenge in endoscopy is how to fabricate a small fiber-optic probe that can achieve comparable function to devices with large, complicated optics. To achieve high resolution over an extended depth of focus (DOF), the application of needle-like beams has been proposed. However, existing methods for miniaturized needle-beam designs fail to adequately correct astigmatism and other monochromatic aberrations, limiting the resolution of at least one axis. Here, we describe an approach to realize freeform beam-shaping endoscopic probes via two-photon polymerization three-dimensional (3D) printing. We present a design achieving <8μm lateral resolution with a DOF of ∼800 μm. The probe has a diameter of <260 μm (without the torque coil and catheters) and is fabricated using a single printing step directly on the optical fiber. The probe was successfully utilized for intravascular imaging in living diabetic swine at multiple time points, as well as human atherosclerotic plaques ex vivo. To the best of our knowledge, this is the first report of a 3D-printed micro-optic for in vivo imaging of the coronary arteries. These results are a substantial step to enable the clinical adoption of both 3D-printed micro-optics and beam-tailoring devices.A fundamental challenge in endoscopy is how to fabricate a small fiber-optic probe that can achieve comparable function to devices with large, complicated optics. To achieve high resolution over an extended depth of focus (DOF), the application of needle-like beams has been proposed. However, existing methods for miniaturized needle-beam designs fail to adequately correct astigmatism and other monochromatic aberrations, limiting the resolution of at least one axis. Here, we describe an approach to realize freeform beam-shaping endoscopic probes via two-photon polymerization three-dimensional (3D) printing. We present a design achieving <8μm lateral resolution with a DOF of ∼800 μm. The probe has a diameter of <260 μm (without the torque coil and catheters) and is fabricated using a single printing step directly on the optical fiber. The probe was successfully utilized for intravascular imaging in living diabetic swine at multiple time points, as well as human atherosclerotic plaques ex vivo. To the best of our knowledge, this is the first report of a 3D-printed micro-optic for in vivo imaging of the coronary arteries. These results are a substantial step to enable the clinical adoption of both 3D-printed micro-optics and beam-tailoring devices.
Advanced Photonics
- Publication Date: Mar. 03, 2025
- Vol. 7, Issue 2, 026003 (2025)
Research Articles
Single-shot spatial-temporal-spectral complex amplitude imaging via wavelength-time multiplexingYingming Xu, Chengzhi Jin, Liangze Pan, Yu He... and Jianqiang Zhu|Show fewer author(s)
Single-shot ultrafast multidimensional optical imaging (UMOI) combines ultrahigh temporal resolution with multidimensional imaging capabilities in a snapshot, making it an essential tool for real-time detection and analysis of ultrafast scenes. However, current single-shot UMOI techniques cannot simultaneously capture the spatial-temporal-spectral complex amplitude information, hampering it from complete analyses of ultrafast scenes. To address this issue, we propose a single-shot spatial-temporal-spectral complex amplitude imaging (STS-CAI) technique using wavelength and time multiplexing. By employing precise modulation of a broadband pulse via an encoding plate in coherent diffraction imaging and spatial-temporal shearing through a wide-open-slit streak camera, dual-mode multiplexing image reconstruction of wavelength and time is achieved, which significantly enhances the efficiency of information acquisition. Experimentally, a custom-built STS-CAI apparatus precisely measures the spatiotemporal characteristics of picosecond spatiotemporally chirped and spatial vortex pulses, respectively. STS-CAI demonstrates both ultrahigh temporal resolution and robust phase sensitivity. Prospectively, this technique is valuable for spatiotemporal coupling measurements of large-aperture ultrashort pulses and offers promising applications in both fundamental research and applied sciences.Single-shot ultrafast multidimensional optical imaging (UMOI) combines ultrahigh temporal resolution with multidimensional imaging capabilities in a snapshot, making it an essential tool for real-time detection and analysis of ultrafast scenes. However, current single-shot UMOI techniques cannot simultaneously capture the spatial-temporal-spectral complex amplitude information, hampering it from complete analyses of ultrafast scenes. To address this issue, we propose a single-shot spatial-temporal-spectral complex amplitude imaging (STS-CAI) technique using wavelength and time multiplexing. By employing precise modulation of a broadband pulse via an encoding plate in coherent diffraction imaging and spatial-temporal shearing through a wide-open-slit streak camera, dual-mode multiplexing image reconstruction of wavelength and time is achieved, which significantly enhances the efficiency of information acquisition. Experimentally, a custom-built STS-CAI apparatus precisely measures the spatiotemporal characteristics of picosecond spatiotemporally chirped and spatial vortex pulses, respectively. STS-CAI demonstrates both ultrahigh temporal resolution and robust phase sensitivity. Prospectively, this technique is valuable for spatiotemporal coupling measurements of large-aperture ultrashort pulses and offers promising applications in both fundamental research and applied sciences.
Advanced Photonics
- Publication Date: Mar. 07, 2025
- Vol. 7, Issue 2, 026004 (2025)
Research Articles
Cascaded adaptive aberration-eliminating multimode fiber imagingZhong Wen, Qilin Deng, Quanzhi Li, Yizhou Tan... and Qing Yang|Show fewer author(s)
In vivo microscopic imaging inside a biological lumen such as the gastrointestinal tract, respiratory airways, or within blood vessels has faced significant technological challenges for decades. A promising candidate technology is the multimode fiber (MMF) endoscope, which enables minimally invasive diagnostics at a resolution reaching the cellular level. However, for in vivo imaging applications deep inside a biological lumen, sample-induced aberrations and the dynamic dispersion in the MMF make the MMF endoscope a chaotic system with many unknowns, where multiple minor fluctuations can couple and compound into intractable problems. We introduce a dynamically encoding, cascaded, optical, and ultrathin polychromatic light-field endoscopy (DECOUPLE) to tackle this challenge. DECOUPLE includes an adaptive aberration correction that can accurately track and control MMF behavior in the spatial-frequency domain to compensate for chaos introduced during complex dynamic imaging processes. We demonstrate the flexibility and practicality of DECOUPLE for noninvasive volumetric imaging in two colors for light passing through various highly aberrating samples including 120-μm-thick onion epidermal slices and 80-μm-thick layers of fat emulsions. To summarize, we represent a significant step toward practical in vivo imaging deep within biological tissue.In vivo microscopic imaging inside a biological lumen such as the gastrointestinal tract, respiratory airways, or within blood vessels has faced significant technological challenges for decades. A promising candidate technology is the multimode fiber (MMF) endoscope, which enables minimally invasive diagnostics at a resolution reaching the cellular level. However, for in vivo imaging applications deep inside a biological lumen, sample-induced aberrations and the dynamic dispersion in the MMF make the MMF endoscope a chaotic system with many unknowns, where multiple minor fluctuations can couple and compound into intractable problems. We introduce a dynamically encoding, cascaded, optical, and ultrathin polychromatic light-field endoscopy (DECOUPLE) to tackle this challenge. DECOUPLE includes an adaptive aberration correction that can accurately track and control MMF behavior in the spatial-frequency domain to compensate for chaos introduced during complex dynamic imaging processes. We demonstrate the flexibility and practicality of DECOUPLE for noninvasive volumetric imaging in two colors for light passing through various highly aberrating samples including 120-μm-thick onion epidermal slices and 80-μm-thick layers of fat emulsions. To summarize, we represent a significant step toward practical in vivo imaging deep within biological tissue.
Advanced Photonics
- Publication Date: Mar. 08, 2025
- Vol. 7, Issue 2, 026005 (2025)
Research Articles
Metasurface-enabled quantum holograms with hybrid entanglementHong Liang, Wai Chun Wong, Tailin An, and Jensen Li
Metasurfaces, with their capability to control all possible dimensions of light, have become integral to quantum optical applications, including quantum state generation, operation, and tomography. We utilize a metasurface to generate polarization–hologram hybrid entanglement between a signal–idler photon pair to construct a quantum hologram. The properties of the quantum hologram can be revealed by collapsing the polarization degree of freedom of the idler photon, inducing interference between two holographic states of the signal photon as a meaningful and selective erasure of the holographic content. On the contrary, interference disappears when the idler photon is detected without observing polarization. This process can be further interpreted as a quantum holographic eraser, where the erasing action is visualized with erased contents in holograms. Our construction of a polarization–hologram hybrid entangled state with metasurfaces will be useful for quantum communication with enhanced robustness, anticounterfeiting applications through the additional quantum degrees of freedom or phase difference between two holographic states, and as an emerging platform for exploring fundamental quantum concepts for entanglement and nonlocality.Metasurfaces, with their capability to control all possible dimensions of light, have become integral to quantum optical applications, including quantum state generation, operation, and tomography. We utilize a metasurface to generate polarization–hologram hybrid entanglement between a signal–idler photon pair to construct a quantum hologram. The properties of the quantum hologram can be revealed by collapsing the polarization degree of freedom of the idler photon, inducing interference between two holographic states of the signal photon as a meaningful and selective erasure of the holographic content. On the contrary, interference disappears when the idler photon is detected without observing polarization. This process can be further interpreted as a quantum holographic eraser, where the erasing action is visualized with erased contents in holograms. Our construction of a polarization–hologram hybrid entangled state with metasurfaces will be useful for quantum communication with enhanced robustness, anticounterfeiting applications through the additional quantum degrees of freedom or phase difference between two holographic states, and as an emerging platform for exploring fundamental quantum concepts for entanglement and nonlocality.
Advanced Photonics
- Publication Date: Mar. 11, 2025
- Vol. 7, Issue 2, 026006 (2025)
Vol. 7, Iss.1-Jan..1,2025
about The Cover
About the cover: Advanced Photonics Volume 7, Issue 1The article provides information about the image on the cover of Advanced Photonics, Volume 7 Issue 1.The article provides information about the image on the cover of Advanced Photonics, Volume 7 Issue 1.
Advanced Photonics
- Publication Date: Feb. 28, 2025
- Vol. 7, Issue 1, 019901 (2025)
Editorials
Quantum: Advancing Photonics for 100 YearsAnatoly Zayats, and Xiao-Cong (Larry) Yuan
The editorial calls on the photonics community to actively engage in shaping the quantum future.The editorial calls on the photonics community to actively engage in shaping the quantum future.
Advanced Photonics
- Publication Date: Feb. 27, 2025
- Vol. 7, Issue 1, 010101 (2025)
Errata
(Erratum) Deep-learning-driven end-to-end metalens imagingJoonhyuk Seo, Jaegang Jo, Joohoon Kim, Joonho Kang... and Haejun Chung|Show fewer author(s)
This erratum notes a correction to a grant number listed in the Acknowledgments section of the originally published article.This erratum notes a correction to a grant number listed in the Acknowledgments section of the originally published article.
Advanced Photonics
- Publication Date: Jan. 15, 2025
- Vol. 7, Issue 1, 019801 (2025)
News and Commentaries
Toward infrared spectral imaging at high resolution and high sensitivityAndrius Baltuška
The article comments on a significant breakthrough in detecting mid-infrared light at low photon counts.The article comments on a significant breakthrough in detecting mid-infrared light at low photon counts.
Advanced Photonics
- Publication Date: Jan. 08, 2025
- Vol. 7, Issue 1, 010501 (2025)
News and Commentaries
Picophotonics goes to higher dimensionsYijie Shen, and Nikolay I. Zheludev
The emerging discipline of picophotonics explores events on a scale thousands of times smaller than the wavelength of light. A recent work introduces a phase singularity ruler that allows picometer-scale localization metrology in three dimensions.The emerging discipline of picophotonics explores events on a scale thousands of times smaller than the wavelength of light. A recent work introduces a phase singularity ruler that allows picometer-scale localization metrology in three dimensions.
Advanced Photonics
- Publication Date: Jan. 28, 2025
- Vol. 7, Issue 1, 010502 (2025)
News and Commentaries
“Pinching” aromatic molecules closer with optical tweezers in single-molecule junctionsLiwei Wang, and Shengxiong Xiao
The commentary discusses work recently published in Physical Review Letters, which reported a nondestructive approach to realizing precise control of p-p stacking at single molecule scale by laser illumination.The commentary discusses work recently published in Physical Review Letters, which reported a nondestructive approach to realizing precise control of p-p stacking at single molecule scale by laser illumination.
Advanced Photonics
- Publication Date: Jan. 28, 2025
- Vol. 7, Issue 1, 010503 (2025)
Research Articles
All-optical spatiotemporal oscilloscope for few-cycle optical waveformQi Zeng, Xinyue Yang, Yimin Deng, Wei Cao, and Peixiang Lu
The advancement of ultrafast science necessitates diagnostic techniques capable of higher precision and increased dimensionality for few-cycle pulses. As pulses continue to shorten temporally and broaden spectrally, the temporal and spatial components become inseparable. Consequently, many established techniques fall short of accurately diagnosing both the temporal and spatial characteristics of pulses. We propose an all-optical spatiotemporal oscilloscope to comprehensively characterize the waveform of few-cycle pulses. By introducing a spatiotemporal perturbing pulse to influence high-harmonic (HH) generation, the frequency of the radiating HHs oscillates with variations in the delay between the pulses. This spatially dependent frequency oscillation of the HHs enables the reconstruction of the temporal and spatial details of the perturbing pulse. This method provides a straightforward and reliable strategy for multidimensional waveform characterization of few-cycle pulses, with potential applications in probing ultrafast dynamical processes carrying spatiotemporal information.The advancement of ultrafast science necessitates diagnostic techniques capable of higher precision and increased dimensionality for few-cycle pulses. As pulses continue to shorten temporally and broaden spectrally, the temporal and spatial components become inseparable. Consequently, many established techniques fall short of accurately diagnosing both the temporal and spatial characteristics of pulses. We propose an all-optical spatiotemporal oscilloscope to comprehensively characterize the waveform of few-cycle pulses. By introducing a spatiotemporal perturbing pulse to influence high-harmonic (HH) generation, the frequency of the radiating HHs oscillates with variations in the delay between the pulses. This spatially dependent frequency oscillation of the HHs enables the reconstruction of the temporal and spatial details of the perturbing pulse. This method provides a straightforward and reliable strategy for multidimensional waveform characterization of few-cycle pulses, with potential applications in probing ultrafast dynamical processes carrying spatiotemporal information.
Advanced Photonics
- Publication Date: Dec. 23, 2024
- Vol. 7, Issue 1, 016001 (2025)
Research Articles
Waveguide superlattices with artificial gauge field toward colorless and low-crosstalk ultrahigh-density photonic integrationXuelin Zhang, Jiangbing Du, Ke Xu, and Zuyuan He
Dense waveguides are the basic building blocks for photonic integrated circuits (PICs). Due to the rapidly increasing scale of PIC chips, high-density integration of waveguide arrays working with low crosstalk over broadband wavelength range is highly desired. However, the subwavelength regime of such structures has not been adequately explored in practice. We propose a waveguide superlattice design leveraging the artificial gauge field mechanism, corresponding to the quantum analog of field-induced n-“photon” resonances in semiconductor superlattices. This approach experimentally achieves -24 dB crosstalk suppression with an ultrabroad transmission bandwidth more than 500 nm for dual polarizations on the Si3N4 platform. The fabricated waveguide superlattices support high-speed signal transmission of 112 Gbit/s with high-fidelity signal-to-noise ratio profiles and bit error rates. This design, featuring a silica upper cladding, is compatible with standard metal back-end-of-the-line processes. Based on such a fundamental structure, which is readily transferable to other platforms, passive and active devices over versatile platforms can be realized with a significantly shrunk on-chip footprint, thus it holds great promise for significant reduction of the power consumption and cost in PICs.Dense waveguides are the basic building blocks for photonic integrated circuits (PICs). Due to the rapidly increasing scale of PIC chips, high-density integration of waveguide arrays working with low crosstalk over broadband wavelength range is highly desired. However, the subwavelength regime of such structures has not been adequately explored in practice. We propose a waveguide superlattice design leveraging the artificial gauge field mechanism, corresponding to the quantum analog of field-induced n-“photon” resonances in semiconductor superlattices. This approach experimentally achieves -24 dB crosstalk suppression with an ultrabroad transmission bandwidth more than 500 nm for dual polarizations on the Si3N4 platform. The fabricated waveguide superlattices support high-speed signal transmission of 112 Gbit/s with high-fidelity signal-to-noise ratio profiles and bit error rates. This design, featuring a silica upper cladding, is compatible with standard metal back-end-of-the-line processes. Based on such a fundamental structure, which is readily transferable to other platforms, passive and active devices over versatile platforms can be realized with a significantly shrunk on-chip footprint, thus it holds great promise for significant reduction of the power consumption and cost in PICs.
Advanced Photonics
- Publication Date: Jan. 28, 2025
- Vol. 7, Issue 1, 016002 (2025)
Research Articles
Unevenly distributed pixel-based camouflage metasurface hiding multiwavelength holograms in color printingYaqin Zheng, Yuan Liao, Yulong Fan, Lei Zhang... and Dangyuan Lei|Show fewer author(s)
Ultracompact metasurfaces have gained a high reputation for manipulating light fields precisely within a subwavelength scale, bringing great development to the fields of nanophotonics, integrated optics, and quantum technology. There is broad interest in expanding the working band of metasurfaces to expand functionalities and the scope of applications. However, increasing the number of working wavelengths multiplexed in a single holographic metasurface is always complicated by two vital issues, i.e., spectral cross talk and the efficiency imbalance between different wavelength channels. Therefore, holographic metasurfaces with multiplexed working wavelengths over three are seldom reported. To address these two issues, we present a design strategy based on unevenly distributed pixels (UEDPs). As a proof of concept, a UEDP-based metasurface is designed to offer a camouflage method to hide four encrypted holographic images in a multicolor printed image. Our results not only demonstrate the idea of UEDP as an easy-to-implement and effective way for strengthening the wavelength multiplexing of metasurfaces but also give rise to a camouflage metasurface by integrating high-capacity and high-security encrypted holographic information with a single printed image. We believe that the generic UEDP-based metasurface design strategy can be readily extended to the realization of artificial functional structures in various disciplines, such as optics, thermology, and acoustics.Ultracompact metasurfaces have gained a high reputation for manipulating light fields precisely within a subwavelength scale, bringing great development to the fields of nanophotonics, integrated optics, and quantum technology. There is broad interest in expanding the working band of metasurfaces to expand functionalities and the scope of applications. However, increasing the number of working wavelengths multiplexed in a single holographic metasurface is always complicated by two vital issues, i.e., spectral cross talk and the efficiency imbalance between different wavelength channels. Therefore, holographic metasurfaces with multiplexed working wavelengths over three are seldom reported. To address these two issues, we present a design strategy based on unevenly distributed pixels (UEDPs). As a proof of concept, a UEDP-based metasurface is designed to offer a camouflage method to hide four encrypted holographic images in a multicolor printed image. Our results not only demonstrate the idea of UEDP as an easy-to-implement and effective way for strengthening the wavelength multiplexing of metasurfaces but also give rise to a camouflage metasurface by integrating high-capacity and high-security encrypted holographic information with a single printed image. We believe that the generic UEDP-based metasurface design strategy can be readily extended to the realization of artificial functional structures in various disciplines, such as optics, thermology, and acoustics.
Advanced Photonics
- Publication Date: Jan. 30, 2025
- Vol. 7, Issue 1, 016003 (2025)
Research Articles
Training neural networks with end-to-end optical backpropagationJames Spall, Xianxin Guo, and Alexander I. Lvovsky
Optics is an exciting route for the next generation of computing hardware for machine learning, promising several orders of magnitude enhancement in both computational speed and energy efficiency. However, reaching the full capacity of an optical neural network (NN) necessitates that the computing be implemented optically not only for inference but also for training. The primary algorithm for network training is backpropagation, in which the calculation is performed in the order opposite to the information flow for inference. Although straightforward in a digital computer, the optical implementation of backpropagation has remained elusive, particularly because of the conflicting requirements for the optical element that implements the nonlinear activation function. We address this challenge for the first time, we believe, with a surprisingly simple scheme, employing saturable absorbers for the role of activation units. Our approach is adaptable to various analog platforms and materials and demonstrates the possibility of constructing NNs entirely reliant on analog optical processes for both training and inference tasks.Optics is an exciting route for the next generation of computing hardware for machine learning, promising several orders of magnitude enhancement in both computational speed and energy efficiency. However, reaching the full capacity of an optical neural network (NN) necessitates that the computing be implemented optically not only for inference but also for training. The primary algorithm for network training is backpropagation, in which the calculation is performed in the order opposite to the information flow for inference. Although straightforward in a digital computer, the optical implementation of backpropagation has remained elusive, particularly because of the conflicting requirements for the optical element that implements the nonlinear activation function. We address this challenge for the first time, we believe, with a surprisingly simple scheme, employing saturable absorbers for the role of activation units. Our approach is adaptable to various analog platforms and materials and demonstrates the possibility of constructing NNs entirely reliant on analog optical processes for both training and inference tasks.
Advanced Photonics
- Publication Date: Feb. 04, 2025
- Vol. 7, Issue 1, 016004 (2025)
Research Articles
Resonantly driven nonlinear dynamics of soliton molecules in ultrafast fiber lasersDefeng Zou, Runmin Liu, Yanqing Shi, Aoyan Zhang... and Perry Ping Shum|Show fewer author(s)
Recent years have seen significant advances in the study of dissipative soliton molecules in ultrafast lasers, driven by their remarkable connections to a wide range of physical systems. However, understanding and controlling the underlying physics of soliton molecules remain elusive due to the absence of a universal physical model that adequately describes intramolecular motion. We demonstrate that resonant excitation generates breather soliton molecules, with their resonance susceptibility exhibiting high amplitude-driven operations that can be well understood within the framework of the Duffing model. Harnessing powerful experiment techniques and detailed numerical simulations, we reveal the fundamental resonant mode within intrapulse separation constrained to the 100 fs level as well as the presence of the subharmonic and overtones. Additionally, we observe chaotic dynamics arising from the multiple-frequency nonlinear interactions in a strongly dissipative regime. Our work provides a perspective on the complex interactions of dissipative optical solitons through the lens of nonlinear physics. This approach offers a simple test bed for complex nonlinear physics research, with ultrafine scanning of temporal separations of ultrashort laser pulses demonstrating significant potential for applications requiring high detection sensitivity.Recent years have seen significant advances in the study of dissipative soliton molecules in ultrafast lasers, driven by their remarkable connections to a wide range of physical systems. However, understanding and controlling the underlying physics of soliton molecules remain elusive due to the absence of a universal physical model that adequately describes intramolecular motion. We demonstrate that resonant excitation generates breather soliton molecules, with their resonance susceptibility exhibiting high amplitude-driven operations that can be well understood within the framework of the Duffing model. Harnessing powerful experiment techniques and detailed numerical simulations, we reveal the fundamental resonant mode within intrapulse separation constrained to the 100 fs level as well as the presence of the subharmonic and overtones. Additionally, we observe chaotic dynamics arising from the multiple-frequency nonlinear interactions in a strongly dissipative regime. Our work provides a perspective on the complex interactions of dissipative optical solitons through the lens of nonlinear physics. This approach offers a simple test bed for complex nonlinear physics research, with ultrafine scanning of temporal separations of ultrashort laser pulses demonstrating significant potential for applications requiring high detection sensitivity.
Advanced Photonics
- Publication Date: Feb. 07, 2025
- Vol. 7, Issue 1, 016005 (2025)
Research Articles
Large-scale free-space photonic circuits in two dimensionsMaria Gorizia Ammendola, Francesco Di Colandrea, Lorenzo Marrucci, and Filippo Cardano
Photonic circuits, engineered to couple optical modes according to a specific map, serve as processors for classical and quantum light. The number of components typically scales with that of processed modes, thus correlating system size, circuit complexity, and optical losses. We present a photonic-circuit technology implementing large-scale unitary maps in free space, coupling a single input to hundreds of output modes in a two-dimensional compact layout. The map corresponds to a quantum walk of structured photons, realized through light propagation in three liquid-crystal metasurfaces, having their optic axes artificially patterned. Theoretically, the walk length and the number of connected modes can be arbitrary while keeping losses constant. The patterns can be designed to replicate multiple unitary maps. We also discuss limited reconfigurability by adjusting the overall birefringence and the relative displacement of the optical elements. These results lay the basis for the design of low-loss nonintegrated photonic circuits, primarily for manipulating multiphoton states in quantum regimes.Photonic circuits, engineered to couple optical modes according to a specific map, serve as processors for classical and quantum light. The number of components typically scales with that of processed modes, thus correlating system size, circuit complexity, and optical losses. We present a photonic-circuit technology implementing large-scale unitary maps in free space, coupling a single input to hundreds of output modes in a two-dimensional compact layout. The map corresponds to a quantum walk of structured photons, realized through light propagation in three liquid-crystal metasurfaces, having their optic axes artificially patterned. Theoretically, the walk length and the number of connected modes can be arbitrary while keeping losses constant. The patterns can be designed to replicate multiple unitary maps. We also discuss limited reconfigurability by adjusting the overall birefringence and the relative displacement of the optical elements. These results lay the basis for the design of low-loss nonintegrated photonic circuits, primarily for manipulating multiphoton states in quantum regimes.
Advanced Photonics
- Publication Date: Feb. 10, 2025
- Vol. 7, Issue 1, 016006 (2025)
Research Articles
Microcomb-driven photonic chip for solving partial differential equationsHongyi Yuan, Zhuochen Du, Huixin Qi, Guoxiang Si... and Qihuang Gong|Show fewer author(s)
With the development of the big data era, the need for computation power is dramatically growing, especially for solving partial differential equations (PDEs), because PDEs are often used to describe complex systems and phenomena in both science and engineering. However, it is still a great challenge for on-chip photonic solving of time-evolving PDEs because of the difficulties in big coefficient matrix photonic computing, high accuracy, and error accumulation. We overcome these challenges by realizing a microcomb-driven photonic chip and introducing time-division multiplexing and matrix partition techniques into PDE photonic solving, which can solve PDEs with a large coefficient matrix on a photonic chip with a limited size. Time-evolving PDEs, including the heat equation with the first order of time derivative, the wave equation with the second order of time derivative, and the nonlinear Burgers equation, are solved with an accuracy of up to 97%. Furthermore, the parallel solving of the Poisson equation and Laplace’s equation is demonstrated experimentally on a single chip, with an accuracy of 95.9% and 95.8%, respectively. We offer a powerful photonic platform for solving PDEs, which takes a step forward in the application of photonic chips in mathematical problems and will promote the development of on-chip photonic computing.With the development of the big data era, the need for computation power is dramatically growing, especially for solving partial differential equations (PDEs), because PDEs are often used to describe complex systems and phenomena in both science and engineering. However, it is still a great challenge for on-chip photonic solving of time-evolving PDEs because of the difficulties in big coefficient matrix photonic computing, high accuracy, and error accumulation. We overcome these challenges by realizing a microcomb-driven photonic chip and introducing time-division multiplexing and matrix partition techniques into PDE photonic solving, which can solve PDEs with a large coefficient matrix on a photonic chip with a limited size. Time-evolving PDEs, including the heat equation with the first order of time derivative, the wave equation with the second order of time derivative, and the nonlinear Burgers equation, are solved with an accuracy of up to 97%. Furthermore, the parallel solving of the Poisson equation and Laplace’s equation is demonstrated experimentally on a single chip, with an accuracy of 95.9% and 95.8%, respectively. We offer a powerful photonic platform for solving PDEs, which takes a step forward in the application of photonic chips in mathematical problems and will promote the development of on-chip photonic computing.
Advanced Photonics
- Publication Date: Feb. 14, 2025
- Vol. 7, Issue 1, 016007 (2025)
Research Articles
Wavelength-insensitive snapshot Stokes polarimetric imaging based on cascaded metasurfacesXuanguang Wu, Kai Pan, Xuanyu Wu, Xinhao Fan... and Jianlin Zhao|Show fewer author(s)
Compact, single-shot, and accurate Stokes polarimetric imagers are highly desirable for imaging at all scales, from remote sensing to biological diagnosis. Recently, polarimetric imaging demonstrated on the metasurface platform is accelerating its realization and revolutionizing associated techniques and imagers. These breakthroughs, however, are greatly limited by the single operating wavelength and the complexity of metasurfaces. We present a minimalist yet powerful cascaded metasurface strategy to realize wavelength-insensitive snapshot Stokes polarimetric imaging. Two cascaded metasurface polarization gratings built into the 4f imaging system enable optical spin Hall momentum shifts and cross-polarization interference of incident light, which are wavelength-robust and free of polarization cross talk, allowing the 4f system to perform accurate and single-shot polarimetric imaging at an arbitrary wavelength and even low-coherence light. We demonstrate the feasibility and robustness of this cascaded metasurface architecture by characterizing diverse polarization objects. We open an avenue for polarimetric imaging and exhibit promising potential in emerging areas of applications such as biological diagnosis.Compact, single-shot, and accurate Stokes polarimetric imagers are highly desirable for imaging at all scales, from remote sensing to biological diagnosis. Recently, polarimetric imaging demonstrated on the metasurface platform is accelerating its realization and revolutionizing associated techniques and imagers. These breakthroughs, however, are greatly limited by the single operating wavelength and the complexity of metasurfaces. We present a minimalist yet powerful cascaded metasurface strategy to realize wavelength-insensitive snapshot Stokes polarimetric imaging. Two cascaded metasurface polarization gratings built into the 4f imaging system enable optical spin Hall momentum shifts and cross-polarization interference of incident light, which are wavelength-robust and free of polarization cross talk, allowing the 4f system to perform accurate and single-shot polarimetric imaging at an arbitrary wavelength and even low-coherence light. We demonstrate the feasibility and robustness of this cascaded metasurface architecture by characterizing diverse polarization objects. We open an avenue for polarimetric imaging and exhibit promising potential in emerging areas of applications such as biological diagnosis.
Advanced Photonics
- Publication Date: Feb. 12, 2025
- Vol. 7, Issue 1, 016008 (2025)
Research Articles
Skyrmionic spin textures in nonparaxial lightXinrui Lei, Aiping Yang, Xusheng Chen, Luping Du... and Xiaocong Yuan|Show fewer author(s)
Topological textures in optics such as skyrmions and merons are increasingly studied for their potential functions in light–matter interactions, deep-subwavelength imaging, and nanometrology. However, they were previously generated either in strongly confined guided waves or in paraxial beams. This has posed a significant challenge in constructing skyrmions in nonparaxial propagating waves due to the lack of symmetry-breaking in the optical field and difficulty in characterizing the full three-dimensional spin textures at the nanoscale. We theoretically propose and experimentally demonstrate the generation of skyrmionic spin textures in nonparaxial light, where skyrmionic textures with a Bloch-type scheme, including isolated skyrmioniums, skyrmion, and meron lattices are generated in free space. We introduce the interplay between the Hertz potentials to break the dual symmetry of light and build well-defined domains of skyrmions. We experimentally realized the topological textures by applying a hybrid polarized optical vortex and observed the complete three-dimensional spin distributions by a dual-mode waveguide probe. By bridging the gap in the skyrmionic group, we present a topologic diagram, showing how spin–orbit coupling of light governs the spin topology. These findings offer new insights into optical quasi-particles and electron–photon correspondence, potentially facilitating advanced applications in optical metrology, sensing, and storage.Topological textures in optics such as skyrmions and merons are increasingly studied for their potential functions in light–matter interactions, deep-subwavelength imaging, and nanometrology. However, they were previously generated either in strongly confined guided waves or in paraxial beams. This has posed a significant challenge in constructing skyrmions in nonparaxial propagating waves due to the lack of symmetry-breaking in the optical field and difficulty in characterizing the full three-dimensional spin textures at the nanoscale. We theoretically propose and experimentally demonstrate the generation of skyrmionic spin textures in nonparaxial light, where skyrmionic textures with a Bloch-type scheme, including isolated skyrmioniums, skyrmion, and meron lattices are generated in free space. We introduce the interplay between the Hertz potentials to break the dual symmetry of light and build well-defined domains of skyrmions. We experimentally realized the topological textures by applying a hybrid polarized optical vortex and observed the complete three-dimensional spin distributions by a dual-mode waveguide probe. By bridging the gap in the skyrmionic group, we present a topologic diagram, showing how spin–orbit coupling of light governs the spin topology. These findings offer new insights into optical quasi-particles and electron–photon correspondence, potentially facilitating advanced applications in optical metrology, sensing, and storage.
Advanced Photonics
- Publication Date: Feb. 14, 2025
- Vol. 7, Issue 1, 016009 (2025)
Theme Issue on Orbital Angular Momentum (2023)
Published
Editor (s): Xiao-Cong Yuan, Guixin Li, Junsuk Rho
Breaking the diffraction limit for label-free chemical imaging
Vol. 6, Issue 6, 060502 (2024)
Three decades riding the photonic crystal fiber wave: an interview with Prof. Philip Russell
Vol. 6, Issue 6, 060501 (2024)
Physics and artificial intelligence: illuminating the future of optics and photonics
Vol. 6, Issue 5, 050500 (2024)
Vol. 6, Issue 3, 036003 (2024)
Plasmon-assisted mode selection lasing in a lanthanide-based microcavity
Vol. 6, Issue 3, 035001 (2024)
Vol. 6, Issue 2, 026007 (2024)
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