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Monday 21 September

Optics

Phase fields in momentum space of photonic crystal slabs

Chuanlin Li, Aobo Ren and Jiang Wu

Optical phase modulation is of great significant importance in fields such as optical communication, information processing, and precision measurement. Compared with real-space modulation, momentum-space phase modulation has distinct advantages: it is free from structural center constraints, supports unlimited mode capacity, and possesses intrinsic topological protection. This inherent flexibility and scalability allow practical applications systems to operate without stringent optical alignment while providing a large number of independent control channels, thereby advancing the development of high-performance, highly integrated optical systems. Photonic crystal slabs, with their open boundary periodicity and capabilities for momentum-space optical field manipulation, have become a crucial platform for research on momentum-space phase fields. Based on polarization orthogonal decomposition and the scattering matrix within temporal coupled-mode theory, this paper systematically elucidates the generation mechanisms of both two-dimensional momentum-space phase fields, including phase vortices, phase gradients, and phase difference, and multidimensional synthetic momentum-space phase fields in photonic crystal slabs, and reviews recent research and application progress in this area. Finally, the development status, advantages, and possible breakthroughs in the field of momentum-space phase fields are summarized and prospects for future work are discussed.
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Optics

Observation of Replica Symmetry Breaking in Filamentation and Multifilamentation

André C. A. Siqueira, Guillermo Palacios, Jessica E. Q. Bautista et al. (+4 more)

We report the experimental observation and characterization of Replica Symmetry Breaking (RSB) manifestation while analyzing the transverse intensity profile of pulses in filamentation experiments using sapphire crystal and distilled water, excited by a femtosecond laser centered at 800 nm. The RSB arises from the competition between self-focusing and plasma defocusing, subject to local fluctuations in the nonlinear refractive index generated by plasma via multiphoton excitation, which subsequently promotes frustration among modes. Our results confirm the existence of glassy-like photonic states not only in multifilamentation, as previously reported [W. Ettoumi, J. Kasparian, and J. Wolf, "Spin-glass model governs laser multiple filamentation," Phys. Rev. Lett., vol. 115, no. 3, pp. 033902, 2015], but also in the generation of a single filament and in filamentation accompanied by conical emission. These findings improve the understanding of statistical nonlinear optics by establishing connections with magnetism and highlighting the glassy-like behavior of light in the context of ultrafast optical phenomena.
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All authors André C. A. Siqueira, Guillermo Palacios, Jessica E. Q. Bautista, Anderson M. Amaral, Albert S. Reyna, Edilson L. Falcão-Filho, Cid B. de Araújo

Optics · Cross-listed from physics.app-ph

Pendellösung length-scale neutron and X-ray interferometry

Owen Lailey, Alexandre Boutot, David G. Cory et al. (+12 more)

Neutron and X-ray perfect-crystal interferometers (PCIs) are powerful platforms for studies of fundamental physics and phase-contrast imaging. Further enhancing several PCI capabilities requires reducing crystal blade thickness to the micron scale, which minimizes dynamical-diffraction image blur, permits operation in the pendellösung regime where blade thickness controls beam splitting, and reduces absorption for simultaneous neutron and X-ray operation. However, fabricating multiple crystal blades with identical micrometer-scale thicknesses over centimeter-scale areas remains a major challenge. Here, using a non-etching sub-micron fabrication technique, we demonstrate silicon triple-Laue interferometers with equal-blade-thicknesses of 110 $\mu$m and 350 $\mu$m, operated with both neutrons and X-rays. These devices are the thinnest PCIs realized to date, enabling a factor-of-six reduction in dynamical-diffraction beam spreading for improved phase-contrast imaging, while reaching the single pendellösung length regime in which crystal thickness provides an experimentally accessible control parameter for engineered quantum-optical beam splitting of plane-wave inputs. These results motivate multi-blade PCI designs utilizing identical half-pendellösung crystal lamellae that are proposed for neutron spin–orbit and electric dipole moment measurements.
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All authors Owen Lailey, Alexandre Boutot, David G. Cory, Joseph P. Cotter, Vishal Dhamgaye, Tao Hong, Michael G. Huber, Young-June Kim, Winfried Kockelmann, Jeremy W. Paster, Dusan Sarenac, Kawal Sawhney, Naume Shentevski, Ivar Taminiau, Dmitry A. Pushin

Optics

Real-Time Doppler-Frequency Measurement and Frequency-Pulling Suppression in Arm-locking

Zheng-Rong Xiang, Jun Ke, Tian-Chi Zhu et al. (+3 more)

Arm-locking is an important technique for suppressing laser frequency noise in space-based gravitational-wave detection. However, stronger noise suppression inevitably increases the magnitude of frequency pulling, thereby prolonging the lock-acquisition time and increasing the risk of system instability. To address this issue, this paper proposes a real-time Doppler-frequency measurement and frequency-pulling suppression method based on a linear-quadratic-gaussian controller. To achieve a balance between noise suppression and pulling suppression, a time-varying control strategy is adopted. At the initial stage of the time-varying control process, the primary objective is to rapidly limit frequency pulling. Subsequently, the level of pulling suppression is gradually relaxed while the capability for laser frequency-noise suppression is progressively enhanced, so that the residual frequency noise satisfies the time-delay interferometry (TDI) requirement by the end of the transition. Comprehensive performance simulations are conducted for several arm-locking configurations. The results show that the proposed suppressor can reduce frequency pulling within approximately 1000 s while limiting its magnitude to below 100 MHz, thereby eliminating the need for the conventional Doppler frequency pre-estimation stage. When a Fabry-Perot laser is used, the amplitude spectral density (ASD) of the closed-loop laser frequency noise meets the requirements of second-generation and first-generation TDI after 2000 s and 9200 s of closed-loop operation, respectively. These results demonstrate that the proposed suppressor provides both rapid frequency-pulling suppression and a high level of laser frequency-noise suppression. This new method provide a feasible way for rapid acquisition and locking of arm-locking.
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All authors Zheng-Rong Xiang, Jun Ke, Tian-Chi Zhu, Hao-Xin Xu, Cheng-Gang Shao, Jie Luo

Optics

Replica Symmetry Breaking in the Quasi Mode Locked Regime of Titanium Sapphire Lasers

Nicolas P. Alves, Ricardo V. M. de Almeida Filho, Isaac C. Nunes et al. (+4 more)

Recent observations of replica symmetry breaking (RSB) in ytterbium-based mode-locked fiber lasers have revealed glassy behavior in the quasi-mode-locked (QML) regime. Here, we investigate whether this behavior is restricted to a specific laser implementation or represents a more general feature of mode-locked systems. By analyzing statistical correlations of spectral intensity fluctuations through the Parisi overlap and Pearson correlation parameters, we study two Titanium:sapphire laser systems: a homemade cavity and a commercial laser. In both cases, clear signatures of RSB are observed in the QML regime, while replica-symmetric behavior is recovered in the amplified spontaneous emission (ASE) and standard mode-locked (SML) regimes. These results demonstrate the occurrence of RSB in Titanium:sapphire lasers and support the interpretation of the QML regime as a photonic glassy phase. Together with previous observations in ytterbium-based fiber lasers, these findings suggest that the connection between QML dynamics and RSB may be a general feature of mode-locked laser systems.
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All authors Nicolas P. Alves, Ricardo V. M. de Almeida Filho, Isaac C. Nunes, Gleison S. Bezerra, Cid B. de Araújo, Marcio H. G. de Miranda, André C. A. Siqueira

Optics

Ultralow-power, high-speed programmable Si photonic circuits with InGaAsP membrane

Tomohiro Akazawa, Rui Tang, Hanzhi Tang et al. (+6 more)

Programmable photonic circuits have emerged as a promising platform for applications ranging from optical communications to artificial-intelligence computing and quantum information processing, but their scaling is fundamentally constrained by their essential building block, the optical phase shifter. Existing phase-shifter technologies face inherent trade-offs among power consumption, operating speed, modulation efficiency, optical loss, and thermal crosstalk, making it challenging to realize high-performance, large-scale programmable photonic circuits. Here, we present a programmable photonic circuit based on InGaAsP/Si hybrid metal-oxide-semiconductor (MOS) phase shifters that combines ultralow power consumption, high-speed operation, high modulation efficiency, low optical loss and negligible thermal crosstalk. The phase shifters combine the low leakage current of a MOS capacitor with the strong carrier-induced refractive-index modulation of an InGaAsP membrane, achieving a static power consumption below 30 fW/$\pi$, a switching time of 555 ps, a phase-modulation efficiency ($V_\pi L$) of 0.13 Vcm and a carrier-induced excess insertion loss of only 0.20 dB/$\pi$. We integrate these phase shifters into a programmable Mach-Zehnder interferometer mesh and demonstrate optical switching and programmable unitary transformations, while maintaining femtowatt-level static power consumption across integrated phase shifters. We further demonstrate circuit-level operation with negligible thermal crosstalk, addressing a major obstacle to densely integrated programmable photonic circuits. These results establish a foundation for scalable, high-performance programmable photonic systems for next-generation signal processing and computation.
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All authors Tomohiro Akazawa, Rui Tang, Hanzhi Tang, Makoto Okano, Yangyang Wan, Nobuyuki Matsuda, Kasidit Toprasertpong, Shinichi Takagi, Mitsuru Takenaka

Optics · Cross-listed from quant-ph

Versatile Quantum Machine Learning with an Ultra-low Power Photonic Quantum Reservoir Computer

Wei Wang, Zan Tang, Menglong Fang et al. (+7 more)

Integrated photonic microprocessors provide high-bandwidth, massively parallel linear computation, but realizing nonlinear feature maps and temporal memory remain key challenges for machine learning. Conventional approaches rely on active tuning and additional nonlinear elements, increasing architectural complexity and power overhead. Here we demonstrate an integrated photonic quantum reservoir computer that achieves nonlinear mapping, fading memory, and task versatility without active tuning of the reservoir core. The same chip supports accurate static classification, dynamic prediction, and stable autonomous forecasting, establishing broad utility across both classification and temporal inference tasks. Competitive performance is retained in the zero-bias state, where all on-chip phase shifters are unpowered, eliminating active control and reducing computational power consumption to zero. This passive operation highlights a scalable route to multifunctional machine-learning hardware, where large-scale photonic quantum processors can be repurposed as reservoirs without reconfiguring their internal optical networks. By combining quantum-state encoding, multimode interferometric mixing, and photon-statistical readout, this architecture provides a physically grounded paradigm for low-power, large-scale quantum reservoir computing.
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All authors Wei Wang, Zan Tang, Menglong Fang, Daiqin Su, Mile Gu, Jayne Thompson, Lip Ket Chin, Hong Cai, Leong-Chuan Kwek, Ai-Qun Liu

Optics

Non-Hermitian photonic time quasicrystal

Shuhang Chen, Zhi Zheng and Qi Zhu

Photonic time crystals amplify waves through temporal modulation. We study a temporal analogue of the non-Hermitian Aubry-André-Harper model. By continuing an incommensurate temporal modulation into the complex phase plane, we find that the bulk amplification rate as a function of the complexification coordinate is organized into distinct integer phases, with its slope locked to an integer within each phase. This integer is Avila's acceleration, connecting a global structure of quasiperiodic operator theory with a directly observable optical propagation response. The quantized response persists in the presence of defects in the time-dependent permittivity modulation that preserve the underlying analytic phase structure. As a wave-level consequence, two input frequencies belonging to different integer phases acquire exponentially separated amplification, producing spectral selection and reshaping the temporal beat pattern. Our results establish that a global integer of quasiperiodic operator theory can govern a tunable, quantized growth response in a non-Hermitian photonic time quasicrystal.
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Optics · Cross-listed from cond-mat.mtrl-sci

Amorphous insulating MoS$_x$ films deposited by magnetron sputtering as a low-index optical coating

S.G. Martanov, E.V. Tarkaeva, A.V. Muratov et al. (+4 more)

While much effort are now concentrated on exploration of crystalline form of MoS$_2$ as a two-dimensional material, we show that room-temperature DC magnetron sputtering from pressurized MoS$_2$ powder target produces amorphous MoS$_x$ films with optical properties fundamentally different from those of crystalline MoS$_2$. The films were found to have a sulfur content of approximately $x=1.8$, indicating sulfur deficiency. They are optically isotropic and exhibit rather low optical losses, with a refractive index of about 2 over the visible and near-infrared spectral range. Their compatibility with lift-off lithography and dry etching makes amorphous MoS$_x$ a promising material for integrated photonic applications.
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All authors S.G. Martanov, E.V. Tarkaeva, A.V. Muratov, A.V. Lubenchenko, O.N. Pavlov, A.G. Vitukhnovsky, A.Yu. Kuntsevich

Optics

Dual-layer large-numerical-aperture metalenses with rotational zoom capability

Tingfeng Lei, Guanqing Shu and Xiaodong Chen

We present a non-paraxial design strategy based on the full ideal aberration-free phase function for a dual-layer rotational zoom metalens. By adopting the exact lens phase expression rather than the conventional parabolic approximation, this approach preserves the higher-order phase contributions critical to large-NA operation. Zooming is achieved by engineering complementary phase distributions on two metasurface layers and dynamically modulating their combined phase via controlled rotation. To realize the target phase profiles, a dielectric metasurface operating at 10 GHz is designed using ceramic cylindrical resonators arranged in a triangular lattice. A systematic parametric optimization of lattice period, cylinder diameter, and height ensures a complete 2pi phase coverage while maintaining a transmission above 85%. The resulting phase-geometry mapping establishes a reliable unit-cell library for device implementation. Leveraging this library, the dual-layer metalens is designed and its performance evaluated through finite-difference time-domain simulations. A prototype with a 300 mm aperture is fabricated and experimentally characterized using three-dimensional near-field scanning measurements. Both simulations and experiments confirm that continuous focal-length tuning is achieved as the rotation angle varies from -60deg to 60deg, corresponding to a focal-length range of 100 to 300 mm and a zoom ratio of 3:1. The device achieves a maximum NA of 0.83, and the measured focal spots remain nearly diffraction-limited. The experimentally extracted focal-length variation agrees closely with theoretical predictions and simulations.
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Optics

Hypervectors from Optical Disorder: Programmable Encoding and Optical Inference for Hyperdimensional Computing

Takuya Iwata, Namthip Srisuthep and Satoshi Sunada

Hyperdimensional computing (HDC) is a computing framework that represents information as high-dimensional pseudorandom vectors called hypervectors (HVs), enabling learning and inference through simple algebraic operations. The HV dimensionality provides computational capacity and error robustness, but the required high-dimensional randomness must be stored or regenerated, imposing a memory–computation tradeoff. Here, we address this tradeoff by physically embodying the randomness required for HV generation in the static disorder of a scattering medium. Specifically, a silicon photonic circuit combined with the scattering medium generates high-dimensional HVs from a small number of input values in a single optical shot. Detector-side encoding programs HV correlations for continuous and categorical representations. The resulting HVs reproduce key statistical and compositional properties of ideal i.i.d.\ random HVs, including pairwise similarity statistics, associative-memory capacity, and factorization capacity. We further demonstrate an optically assisted inference path using the generated HVs and optical similarity evaluation.
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Optics

Adaptive Solitons

Yuchuan Chen, Jiacheng Zhao, Qiuran Zhu et al. (+1 more)

Femtosecond laser pulses have incredible potential but still face some performance and stability issues. Here we discover a new nonlinear optical effect, frequency-comb-induced stimulated Brillouin scattering resonance, which can only be excited by a new type of soliton, adaptive solitons. Adaptive solitons possess the unique properties of adaptive down-chirp which breaks area theorem limitation on pulse energy in normal dispersion lasers, spectral profile self-regulation which provides high pulse contrast and breaks gain narrowing limitation in amplifiers, and freedom from dispersive radiation that weakens and deforms current ultrashort laser pulses in transmission media. More intriguingly, they have an adaptive transmission gain in normal dispersion waveguides which has the potential to enable them to be lossless in long normal dispersion waveguides for repeaterless soliton communication. A passive frequency-modulation mode-locked fiber laser was successfully built and generated incredibly stable adaptive solitons. Even though the laser had no negative dispersion elements, the output solitons were measured as down-chirped which enables them to keep soliton properties in normal dispersion waveguides, perfect for ultrafast applications with waveguide delivery. With the advantages of high consistency, high pulse contrast, and high energy capability; adaptive solitons are excellent for fields including micromachining, laser surgery, quantum computing, and spectroscopy.
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All authors Yuchuan Chen, Jiacheng Zhao, Qiuran Zhu, Bill Chen

Optics

Synthetic-Aperture Super-Resolution Imaging via Spatial-Frequency Shift in Near-Field Diffraction

Qihao Sun, Chunzheng Bai, Wenjing Fang et al. (+5 more)

Grating-based computational imaging shifts high-spatial-frequency information into the detectable range, enabling super-resolution reconstruction. However, a fixed grating produces effective diffraction-mediated shifts only for specific spatial-frequency vectors, limiting spatial-frequency coverage. Here, we propose a synthetic-aperture super-resolution method in which repeated imaging with a rotating grating broadens spatial-frequency coverage and expands the effective aperture. A physics-prior-guided restoration framework then employs a multichannel deep-learning network to fuse images acquired at different grating orientations. Using diffraction images from only three grating orientations, the proposed method reconstructed the object with a resolution of $\lambda/3.9$. This approach offers a practical route to grating-modulated super-resolution imaging in systems with limited numerical aperture.
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All authors Qihao Sun, Chunzheng Bai, Wenjing Fang, Zongyan Zhang, Songlin Yang, Yonghong Ye, Mingyi Tao, Jiayu Zhang

Optics

Sustained Orbital Motion Driven by Circularly Polarized Light in Nanoscale Stator-Rotor Architectures

Shiye Du, Juanshu Wu, Xin Chen et al. (+2 more)

Light-induced forces and torques offer a versatile strategy for remotely actuating microscopic objects, enabling breakthroughs including optical trapping and light-driven nanomachines. Extending such optical actuation to sustained cyclic motion, however, requires fundamentally distinct designs and, in particular, forces capable of delivering nonzero mechanical work over repeated cycles. Here, we demonstrate via simulations a nanoscale stator-rotor architecture, which achieves persistent orbital motion of a spherical rotor under circularly polarized plane-wave illumination. An off-center rotor displacement defines a stator-rotor structural polarity. Optical helicity coupled to this polarity generates a tangential force perpendicular to the instantaneous stator-rotor direction; as the rotor moves around the stator, the force direction rotates with it. Electrodynamic symmetry analysis identifies this response as arising from antisymmetric, nonconservative forces that produce nonzero closed-cycle work, whereas linear polarization yields symmetric, conservative responses with zero closed-cycle work. Material screening and Bayesian optimization identify an Ag-nanoshell design region, while Pareto analysis balances tangential actuation and radial confinement. A balanced candidate is predicted to lower the maximum steady-state temperature rise from 56.2 to 20.9 K relative to Au at the same light intensity. Brownian-dynamics simulations further show confined, helicity-defined orbital motion, with all 32 trajectories retaining the same circulation direction. These results establish a symmetry-guided route toward sustained cyclic optical actuation at the nanoscale.
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All authors Shiye Du, Juanshu Wu, Xin Chen, Mouhong Lin, Hongyu Chen

Optics

Square-Root Higher-Order Exceptional Points with Symmetry-Induced Multiple Spectral Responses

Haoyang Zhang, Yadi Niu, Nuo Wang et al. (+2 more)

We generalize square-root procedure to non-Hermitian systems with finite lattices, providing a spectral operation scheme applicable to arbitrary tight-binding models. Via this generalized square-root approach, we construct novel chiral-symmetric higher-order exceptional points (EPs) with multiple spectral responses. By taking square-root of a parent Hamiltonian hosting an $n$th-order EP (EP$_n$), an EP$_{2n+1}$ chiral-symmetric square-root system is obtained, whose lattice sites are inherited from both the parent system and an auxiliary residual system. The chiral-symmetry-induced structure of the generalized eigenspace enables onsite and coupling perturbations to selectively generate spectral responses of different orders. The proposed scheme is universal, applicable to any existing tight-binding EP system and iterable to generate EPs of arbitrarily high order. With enriched ultrasensitive spectral responses, the chiral-symmetric higher-order EP system provides a promising platform for signal amplification, detection and non-Hermitian control.
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All authors Haoyang Zhang, Yadi Niu, Nuo Wang, Zihan Mo, Ying Gu

Sunday 20 September

Optics

Nonlinear susceptibility for stimulated light scattering in plasmas

Aleksei Zheltikov

A self-consistent treatment of strong-field laser - plasma interactions suggests a heuristically valuable extension of the notion of nonlinear-optical susceptibility to perturbative regimes of stimulated light scattering in plasmas, offering powerful insights into stimulated-scattering-induced cross-beam energy transfer processes. These findings lay grounds for a unified treatment of stimulated light scattering across a vast area of optical physics, spanning from fiber optics and neutral gases to laser - plasma physics.
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Optics · Cross-listed from physics.flu-dyn

Design of a combined polarimetric and velocimetric measurement for viscoelastic stress, and its constitutive resolving power

Zijian Liu, Julian Olszewski, Bruce I. Gaynes et al. (+1 more)

A polarimeter does not report stress. It reports a retardance and an azimuth, and converting those to a stress pair fixes both the calibration that is required and the covariance that the subsequent inference must carry. We set out that observation chain for planar viscoelastic flow, combine it with velocimetry, and ask what the combined measurement can resolve. The calibration constant is fixed by three separately measurable quantities (path length, stress-optic coefficient and wavelength) rather than being fitted. Propagating the polarimetric errors to first order gives a stress covariance that is anisotropic and site dependent even for independent homoscedastic inputs, and whose conditioning degrades as the retardance approaches zero, where the linearization itself stops describing the measurement. Wrapping imposes a separate design bound. Two numerical studies follow, both in ideal calibrated stress coordinates under a prescribed covariance rather than the propagated polarimetric one. Holding the total scalar count fixed and varying the split between velocimetric and optical sites, an unequal allocation favoring optical sites outperforms either pure configuration. We then ask what the measurement resolves between constitutive models compatible with the same velocity data. In self-consistent pressure-driven flow of the finitely extensible nonlinear elastic Peterlin model, at extensibility L^2=50 and 3% noise, the optical channel rejects the velocity-compatible Oldroyd-B family in 78.1% of realizations at the Deborah number De=2, the ratio of the relaxation time to the flow timescale, and in 100% at De=4, while rejecting only about 5% below De=0.3. The resolving power of a design is therefore a strong function of Deborah number and must be quoted with it.
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All authors Zijian Liu, Julian Olszewski, Bruce I. Gaynes, Jie Xu

2609.23787 · 20 Sep · 16 pages, 4 figures, 1 table. Supplementary material (15 pages) is included as an ancillary file. See also arXiv:2609.25663. v2: reference to arXiv:2609.25663 made resolvable; editorial revisions to the abstract and text; results unchanged

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Optics

Extended three dimensional optical tweezers with a Single Gaussian Beam in a stratified medium

Sramana Das, Suvajit Dey, Nirmalya Ghosh et al. (+2 more)

We demonstrate a simple and effective approach for realizing extended volumetric optical trapping using a single linearly polarized Gaussian beam propagating through a stratified medium with engineered refractive index gradients. On modifying the gradients, the focal field undergoes axial elongation and develops multiple localized intensity maxima, enabling simultaneous trapping of particles at distinct axial planes. Both on-axis and off-axis trapping configurations are experimentally observed, forming a volumetric particle distribution without the need for complex holographic beam shaping. A rigorous theoretical framework based on the Debye Wolf diffraction formalism combined with Generalized Lorenz-Mie Theory is employed to model the focused field and the resulting optical forces. The analysis, substantiated with numerical simulations, shows that spherical aberration arising from refractive-index discontinuities plays a crucial role in redistributing optical energy, leading to the formation of multiple stable trapping regions. The axial trapping potential decreases monotonically with increasing mismatch, indicating a trade-off between multi-site trapping capability and trapping potential, which is in quantitative agreement with experimental observations. This work establishes refractive index engineering as a powerful tool for tailoring three-dimensional optical force landscapes using minimal optical complexity, thus offering a scalable alternative to conventional holographic optical tweezers towards applications in colloidal assembly, micromanipulation, and biophotonics.
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All authors Sramana Das, Suvajit Dey, Nirmalya Ghosh, Subhasish Dutta Gupta, Ayan Banerjee

Optics

Laser-Driven Electron Emission Carrying Orbital Angular Momentum from Carbon Nanotubes

Lihan Chi, Ziwen Wang, Yigeng Peng et al. (+3 more)

Extending the orbital angular momentum (OAM) degree of freedom to slow electrons would open a distinct regime of low-energy electron-matter interactions. Using time-dependent density-functional theory, we demonstrate that laser-driven armchair carbon nanotubes (CNTs) can emit OAM-carrying slow electrons. A circularly polarized OAM-writing pulse promotes circumferential electronic motion and generates OAM about the tube axis; a delayed linearly polarized extraction pulse releases slow electrons carrying the injected angular momentum. We find much higher ionization yields and net emitted axial OAM in representative CNTs than in oriented CO2 and benzene under identical laser conditions. Increasing the tube diameter enhances the ionization yield and OAM substantially, and moreover, reversing the helicity of the OAM-writing pulse flips the sign of the emitted OAM. Together, these findings establish CNTs as a platform for slow-electron emission with optically controllable OAM.
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All authors Lihan Chi, Ziwen Wang, Yigeng Peng, Chao Yu, Zhongjun Li, Ruifeng Lu

Optics · Cross-listed from physics.chem-ph

Attosecond charge migration timescales are dominated by transition dipoles, not correlations

Km Akanksha Dubey and Ofer Neufeld

Attosecond charge migration (CM) is an ultrafast process occurring when a molecule is irradiated by ultrashort laser pulses, creating a localized hole. The hole propagates rapidly through the molecule, generating electric currents and transferring charge across the molecular backbone. CM is a key ingredient in solar energy conversion, photosynthesis, and radiation damage. Despite its importance and intensive research, the fundamental physical and chemical mechanisms of CM remain not fully understood. Especially, a deeper insight into the role correlations play in the dynamics, and which chemical attributes determine CM timescales, is needed. Here we study with ab-initio time-dependent density functional theory CM in the benchmark molecule, BrC$_4$H. We thoroughly explore CM under different initial conditions at the electronic and structural levels, including with theories of varying degrees of electronic correlations. We uncover a universal behavior where the hole moment (connecting to experimental observables) dominant frequency is roughly independent of all of these characteristics. In contrast, the timescales of the hole density evolution do vary with the chemical conditions and level of correlations. Employing a semi-analytical theory that reconstructs the hole moments in the cationic reference frame, we show that the attosecond timescale of CM is determined by molecular dipoles that filter out specific frequency responses with an analogy to optical selection rules. Our results provide essential insight into CM physics, which should be useful for interpreting attosecond experiments and engineering CM timescales by tailoring transition dipoles.
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Optics

Cryogenic thermo-optic response of low-loss phase change material for non-volatile photonic phase shifter

Marcus Tamura, Chuanyu Lian, Hongyi Sun et al. (+8 more)

Phase change materials (PCMs) can enable non-volatile optical memory through the large refractive index and extinction coefficient contrast between crystalline and amorphous states. Among them, $\mathrm{Sb}_{2}\mathrm{Se}_{3}$ combines low optical attenuation at telecom wavelengths, making it promising for low-loss programmable phase shifters. Its non-volatility is particularly useful for cryogenic systems, where power dissipation and thermal load constrain scalability. However, its optical properties at cryogenic temperatures remains poorly understood. Here, we report the first cryogenic optical characterization of $\mathrm{Sb}_{2}\mathrm{Se}_{3}$ integrated on a foundry silicon photonic platform from 4K to 300K for both crystalline and amorphous states. We observe that the magnitude of the thermo-optic coefficient decreases upon cooling, whereas the optical attenuation changes only weakly for both the amorphous and crystalline phases. We report the stability of the material upon repeated thermal cycling. These measurements provide the material parameters and stability required to design low-loss, non-volatile photonic memory elements for scalable cryogenic information processing.
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All authors Marcus Tamura, Chuanyu Lian, Hongyi Sun, Yi-Siou Huang, Sadra Rahimi Kari, Zhimu Guo, Alexander N. Tait, Nir Rotenberg, Nathan Youngblood, Carlos A. Ríos Ocampo, Bhavin J. Shastri

Optics · Cross-listed from quant-ph

Feedback-Induced Dynamical Phases in a Self-Adaptive Quantum Kicked Rotor

Pan Gao, Zheng-Wei Zhou, Guang-Can Guo et al. (+1 more)

We introduce a self-adaptive Floquet system based on a quantum kicked rotor, in which the kicking strength itself becomes a dynamical variable generated self-consistently through cavity-mediated feedback. A superradiant transition gives rise to cavity-mediated kicking and two competing instability channels, symmetric and antisymmetric, which provide a unified organizing principle for the nonequilibrium Floquet phases. For resonant kicking, their competition produces double-kick dynamics that support resonant ballistic transport and an emergent antiresonance with period-quadrupled rotor evolution, arising from a balance between the two instability channels. Remarkably, for incommensurate kicking, the antisymmetric instability stabilizes a robust period-doubled localized phase with persistent subharmonic dynamics despite the underlying incommensurate driving, revealing localized temporal order absent in conventional kicked rotors. As the feedback strength increases, correlated temporal fluctuations progressively suppress quantum interference, driving crossovers from period-doubled localization to irregular localization and eventually to subdiffusive transport. Our results establish a general framework for self-adaptive quantum-chaotic dynamics and demonstrate how dynamical feedback can fundamentally reshape transport, localization, and temporal order in driven quantum systems.
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All authors Pan Gao, Zheng-Wei Zhou, Guang-Can Guo, Xi-Wang Luo

Optics

$f$-2$f$ self-referencing for silicon nitride photonics via a heterogeneously integrated lithium niobate layer

Weichen Fan, Bastian Ruhnke, Camiel Op de Beeck et al. (+4 more)

Heterogeneous integration combines complementary material properties in a single photonic platform. Here, we demonstrate on-chip $f$-2$f$ self-referencing in a heterogeneously integrated Si$_3$N$_4$/LiNbO$_3$ platform, in which supercontinuum generation in a Si$_3$N$_4$ waveguide and second-harmonic generation in a LiNbO$_3$ layer are spatially separated and linked by adiabatic escalator couplers. Pumped by a 1560 nm mode-locked laser with 75 pJ on-chip pulse energy, we detect the carrier-envelope offset frequency with 30 dB signal-to-noise ratio in 300 kHz resolution bandwidth. A comparative measurement confirms that the second harmonic originates in the LiNbO$_3$ layer and indicates opportunity for further improvements through periodic poling. These results establish heterogeneous Si$_3$N$_4$/LiNbO$_3$ integration as a viable building block for self-referenced ultrafast pulse sources in low-loss Si$_3$N$_4$ photonics.
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All authors Weichen Fan, Bastian Ruhnke, Camiel Op de Beeck, Giulio Tavani, Anton Vasiliev, Franz Kärtner, Tobias Herr

Saturday 19 September

Optics · Cross-listed from quant-ph

Deterministic synthesis and processing of frequency-bin qubits in a macroscopically coherent quantum memory

S.A.Moiseev

Quantum information processing requires efficient storage and manipulation of photonic states. In this work, we harness pre-created macroscopic spin coherence as an additional degree of freedom to control a cavity-assisted quantum memory. We derive equations of motion for such a memory that predict efficient emission and absorption of two-color fields under a generalized nonlocal spectral impedance-matching condition, which reduces to the well-known condition in the single-mode case. These equations reveal a new operating mechanism of cavity-assisted quantum memory wherein the controlled spin coherence couples the emitted spectral modes. As a result, our memory deterministically synthesizes arbitrary frequency-bin photonic qubits using simple radio-frequency rotations, while the temporal reversibility of the protocol provides perfect transformation of the qubit states. Our findings establish a unified platform bridging quantum storage with elementary signal processing for quantum networks based on spectral encoding of photonic qubits.
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Optics · Cross-listed from quant-ph

Secure Quantum Metasurfaces for Direct Quantum Key Distribution Measurements

Yan He and Adetunmise C. Dada

Quantum key distribution (QKD) can deliver information-theoretic security, but its receivers are still typically assembled from cascaded bulk optics. Metasurfaces offer a radical reduction in this complexity. Here, we make the metasurface function as the QKD measurement device itself. We design wavelength-specific dielectric apertures at 780, 1550, 2000, and 10 600 nm that interweave the linear H/V and circular R/L phase libraries at a 0.44–0.49{\lambda} cell pitch, i.e., below half the operating wavelength, and map the complete passive-BB84 measurement directly onto four detector channels. This subwavelength basis co-location prevents an ordinary propagating-wave aperture mask from isolating one basis without simultaneously attenuating or perturbing the other. Simulated full-wave focal-plane intensities are converted directly into conditional Born probabilities using fitted, calibration-fixed detector regions. The selected designs achieve probability fidelities of 97.96–99.08%, four-port collected efficiencies of 17.43–40.94%, and mean intrinsic quantum bit error rates of 1.42–3.96%. At 1550 nm, the selected design gives an asymptotic device-level yield of 0.151 secret bits per incident photon under an ideal single-photon model. Six-state detector tomography gives positive both-basis security bounds for all six reconstructed receiver models, including their polarization-dependent loss, basis imbalance and crosstalk. These results establish protocol-matched meta-optics as a route to compact, passive QKD receivers.
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Optics

High-Q Magneto-Optical Microdisk Resonators Based on Monocrystalline Bismuth-substituted Yttrium Iron Garnets

Takeru Yambe, Kota Taniguchi, Tatsuya Kitai et al. (+7 more)

Microresonators based on diverse material platforms have driven the progress of integrated photonics by enhancing light-matter interactions in compact volumes. Extending this strategy to magneto-optical (MO) media is highly attractive for nonreciprocal photonics, magnonics, and quantum transduction, yet compact high-Q resonators based on single-crystalline yttrium iron garnet (YIG) have remained elusive because of the difficulty of its nanofabrication. Here we demonstrate high-Q, small-mode-volume MO microdisk resonators based on monocrystalline Bi-substituted YIG (Bi:YIG). Low-loss Bi:YIG thin films prepared by bonding and thinning, combined with optimized Ar-plasma etching, enable submicron-thick, air-suspended microdisks that support telecom-band whispering-gallery modes with $Q = 1.52\times 10^5$, a mode volume $V \approx 200$ cubic wavelengths, and $Q/V \approx 760$, representing an orders-of-magnitude improvement for integrated high-Q YIG MO cavities. The device exhibits clear magnetic-field-dependent spectral responses, including reciprocal resonance shifts and nonreciprocal frequency splitting of counter-propagating modes. A perturbative analytical model quantitatively reproduces these responses and indicates an effective MO coefficient about twice the bulk value, suggesting a possible miniaturization-induced enhancement. These results establish monocrystalline YIG microdisks as a compact high-Q MO platform for integrated isolators, optomechanics, microcombs, and photon-magnon quantum interfaces.
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All authors Takeru Yambe, Kota Taniguchi, Tatsuya Kitai, Daisuke Sato, Syuan Gao, Hajime Kumazaki, Shun Fujii, Takasumi Tanabe, Satoshi Iwamoto, Yasutomo Ota

Optics

Non-Polynomial Wave Computation through Recurrent Resonant Scattering

Junyu Zhu, Enzong Wu, Xiaomeng Li et al. (+2 more)

Structural nonlinearity enables nonlinear input–output mappings to emerge from otherwise linear wave dynamics. Repeated interactions with an input-encoded structure can enhance such mappings, but finite-depth implementations restrict the accessible functional order. Here we show that recurrent scattering in a resonant cavity provides a distinct regime for structural nonlinearity. Repeated interactions are coherently accumulated into a non-polynomial response to structural perturbations. The resulting mapping naturally takes a Kolmogorov–Arnold form: perturbation-induced resonance shifts realize the inner univariate mappings, while the resonant spectral response provides the outer mapping. We identify two complementary physical controls of representation capacity: the resonance linewidth governs the functional richness within each branch, whereas combining multiple branches expands the accessible function space. Microwave-cavity measurements validate the two-stage mapping and demonstrate a two-branch nonlinear computation through XOR classification. Our results connect recurrent resonant scattering with controllable non-polynomial computation in linear wave systems.
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All authors Junyu Zhu, Enzong Wu, Xiaomeng Li, Hongsheng Chen, Zuojia Wang

Optics

Rubidium referenced Kerr comb with cavity phase matching

Xinwei Yi, Kunpeng Jia, Jingru Ji et al. (+6 more)

Phase matching is a fundamental problem in nonlinear optics that is normally constrained by material dispersion. The limited operation wavelengths within phase matching window limits the application, including the precise metrology using Kerr combs. Demanding applications like compact optical clock and astronomical spectroscopy requires atomic reference around 800 nm, where the natural phase matching is challenging. Here we revisit the concept of cavity phase matching (CPM), and fully reveal its advantage to engineer artificial phase matching beyond material dispersion. With the access of CPM condition in a monolithic high-Q fiber Fabry-Pérot resonator featuring a macroscopic cavity length, we achieve low noise Kerr comb generation around 800 nm, within the power budget of a single-mode laser diode. Inside a pump-integrated package of 19 cm3, low phase noise of -125 dBc/Hz at 100 kHz offset frequency is achieved for a 10.1 GHz repetition rate. Most importantly, the generated Kerr comb has been directly referenced to rubidium atomic transition for long-term stable operation. This result not only opens a new way for Kerr comb generation at arbitrary wavelengths, but also can be generalized to any other nonlinear optical frequency conversion application.
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All authors Xinwei Yi, Kunpeng Jia, Jingru Ji, Zhong Yan, Biaobing Jin, Zhenlin Wang, Wei Liang, Shi-Ning Zhu, Zhenda Xie

Friday 18 September

Optics

Cascaded Brillouin-Kerr microcombs in surface nanoscale axial photonic resonators

Emily Eadie, Juan Diego Mazo-Vásquez, Sophia Padvaiskas et al. (+3 more)

Surface nanoscale axial photonic resonators (SNAPRs) provide an axially structured whispering-gallery-mode platform in which nanoscale effective-radius variations produce spatially localized optical resonances. Here, we demonstrate cascaded Brillouin-Kerr microcomb generation in a SNAPR fabricated from 660 micrometer diameter silica fiber. Under continuous-wave pumping, cascaded stimulated Brillouin scattering generates first- and second-order Stokes fields that seed Kerr four-wave mixing within the cavity. The resulting nonlinear spectrum contains two comb families with a common azimuthal spacing of 100.2 GHz and a relative offset of 9.6 GHz, consistent with the Brillouin shift in silica. A low-power transmission spectrogram provides a spatially resolved modal analysis of the resonator, revealing localized resonances with loaded quality factors on the order of ten million, and optical resonance pairs compatible with the measured Brillouin spacing. These results establish SNAPRs as a platform for studying cascaded stimulated Brillouin scattering, Kerr four-wave mixing, and comb formation in axially structured whispering gallery resonators.
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All authors Emily Eadie, Juan Diego Mazo-Vásquez, Sophia Padvaiskas, Flore K. Kunst, Lewis Hill, Pablo Bianucci

Optics

Ultrafast light-sheet optical tweezers for in situ parallelized biomechanical characterization of cells and soft tissues

Krishangi Krishna, Gannon Lemaster, Jieyi Xu et al. (+8 more)

Quantitative characterization of the mechanical properties of cells and tissues is essential for understanding disease progression and tissue regeneration. Optical tweezers (OT) enable the direct application of biologically relevant forces; however, OT has been limited to single axial indentations of cells, thereby restricting throughput. Furthermore, the use of quadrant photodiodes is insufficient for assessing the large displacements required for biomechanical characterization of tissues. We present light-sheet optical tweezers as a force transducer (LOFT), an approach that improves the throughput by at least 3x through simultaneous multiparticle trapping and parallelized characterization under sub-nN forces. LOFT is achieved by uniquely integrating light-sheet illumination for extended trapping, femtosecond-pulsed lasers to augment the optical gradient force, and videography-based particle tracking for observation of force transduction. The platform is validated through single-cell indentation experiments. We then apply LOFT to myocardial tissue, revealing significant biomechanical differences between healthy and infarcted regions; the interpretation of which is further supported by quantitative multiphoton imaging using the same optical source and platform. This work represents the first demonstration of OT for the mechanical testing of intact soft tissues, and establishes LOFT as a versatile, multifunctional platform for high-throughput, minimally invasive, mechanical characterization of complex biological systems in situ.
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All authors Krishangi Krishna, Gannon Lemaster, Jieyi Xu, Zhaowei Jiang, Carlonia G. Casas, Zahra Ahmed, Stephanie Roser, Kareen L. K. Coulombe, Anita Shukla, Vikas Srivastava, Kimani C. Toussaint Jr