Chemical Physics · Cross-listed from cond-mat.soft
Reaction-transport coupling drives spatiotemporal organization in fuel-driven supramolecular polymerization
Akta Singh, Nayana Mukherjee, Jagannath Mondal et al. (+1 more)
Chemically fueled supramolecular systems provide a versatile platform for generating nonequilibrium structures and dynamical instabilities, including chemical oscillations and traveling waves reminiscent of biological organization. However, a minimal mechanistic framework capable of capturing the emergence of such spatiotemporal order is still lacking. Here, we develop a minimal reaction-transport framework for fuel-driven supramolecular polymerization that couples activation-deactivation chemistry with cooperative assembly, fragmentation, and
polymer length-dependent
diffusion. The model captures autonomous oscillations arising through a
Hopf bifurcation and demonstrates how temporal instabilities evolve into spatial self-organization upon inclusion of transport. We show that the nonlinear interplay between reaction kinetics and state-dependent mobility gives rise to traveling polymerization fronts, oscillatory wave dynamics, and complex spatiotemporal patterns. The propagating fronts exhibit near-ballistic dynamics, revealing a fundamentally nonequilibrium transport mechanism emerging from reactive feedback and dynamically evolving diffusivity. These findings establish a minimal physical framework connecting dissipative self-assembly, nonlinear transport, and active matter, while providing design principles for programmable supramolecular materials capable of autonomous spatiotemporal organization.
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All authors Akta Singh, Nayana Mukherjee, Jagannath Mondal, Pushpita Ghosh
Plasma Physics
Non-Ambipolarity of Microturbulent Transport
Allen H Boozer
When exact
magnetic surfaces are assumed to exist, the gyrokinetic theory of microturbulence gives the same radial transport for ions and electrons. But, exact
magnetic surfaces do not exist in the presence of what is called electrostatic microturbulence. When the
plasma pressure is non-zero, a turbulent electric potential is accompanied by a turbulent
magnetic field, which splits the rational
magnetic surfaces with which it resonates. If the
magnetic field is assumed to have an ideal
topology-conserving
evolution, delta function current densities arise on resonant surfaces. The singularity of the current density allows islands to open quickly, but there is no singularity that allows a rapid closure. Islands remain and do not flutter into and out of existence. A relative rotation of the electron fluid in neighboring island chains produces a non-dissipative force that can lock the islands together and produce a non-ambipolar transport. At sufficient
plasma pressure, the islands associated with different resonant rational surfaces can overlap. When this occurs some
magnetic field lines will cross the entire radial region occupied by overlapping islands. The effect on the electron fluid is to create a viscosity-like force, which is dissipative and tends to remove gradients in the electron rotation. This also produces a non-ambipolar transport. Under many assumptions, the island locking force is larger than the viscosity-like force.
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Atmospheric and Oceanic Physics
Toward Trustworthy Short-Range Forecasts with AFNO: From Skill Metrics to Conservation Checks
Akshay Sunil, B. Deepthi and Muhammed Rashid
Data driven weather models now approach traditional numerical weather prediction (NWP) skill at short to medium lead times, but their dynamical consistency during autoregressive rollout remains uncertain.
Optics · Cross-listed from quant-ph
Enhancing the Size of Phase-Space States Containing Sub-Planck-Scale Structures via Non-Gaussian Operations
Arman and Prasanta K. Panigrahi
We observe a metrological advantage in phase-space sensitivity for
photon-added cat and kitten states over their original forms, due to phase-space broadening from increased amplitude via
photon addition, albeit with higher energy cost. Using accessible non-classical resources, weak squeezing and displacement, we construct a squeezed state and two superposed states: the squeezed cat state and the symmetrically squeezed state. Their
photon-added variants are compared with parity-matched cat and KSs using
quantum Fisher information and fidelity. The QFI isocontours reveal regimes where KS exhibit high fidelity and large amplitude, enabling their preparation via Gaussian operations and
photon addition. Similar regimes are identified for cat states enhanced by squeezing and
photon addition, demonstrating improved metrological performance. Moreover, increased amplitude and thus larger phase-space area reduces the size of interferometric fringes, enhancing the effectiveness of
quantum error correction in cat codes.
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General Physics
Scaling-Based Quantization of Spacetime Microstructure
Weihu Ma and Yu-Gang Ma
Planck-scale physics challenges the classical smooth-spacetime picture by introducing
quantum fluctuations that imply a nontrivial spacetime microstructure. We present a framework that encodes these fluctuations by promoting local scale factors, rather than the metric tensor, to fundamental dynamical variables while preserving general covariance. The construction employs a two-tiered hierarchy of scale
manifolds, comprising a first-order
manifold of scale coordinates and a second-order
manifold of fluctuation amplitude coordinates. On the first-order
manifold, we formulate differential geometry, field equations, and a canonical quantization procedure. The theory yields a
geometric renormalization-group flow for scale variables and implies spacetime discreteness at the microscopic level. By constructing a quadratic action and performing spectral decomposition with a stabilizing potential, we obtain discrete modal degrees of freedom quantized as harmonic oscillators. The framework proposes a microscopic description for zero-point energy of spacetime and explores implications for
vacuum energy and ultraviolet regularization, suggesting a potential dynamical mechanism that could ameliorate the cosmological constant problem. Main results include a generalized uncertainty relation with scale-dependent coefficients, locally scaled Klein-Gordon and Dirac equations, geodesic equations for scale spacetime, and a microscopic area operator whose state counting is consistent with the Bekenstein-Hawking
entropy. This work develops a scale-based quantization procedure, providing a foundation for further mathematical analysis and phenomenological tests of spacetime quantization.
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Optics
An optical transistor of the nonlinear resonant structure
Jongbae Kim
An optical transistor capable of simultaneous amplification and switching is theoretically proposed via cascaded second-order nonlinear interactions in a resonant structure. Two distinct operational schemes are analyzed. A single frequency scheme employs cascaded second harmonic generation and inverse second harmonic generation (SHG/iSHG) using two Type-I SHG interactions, whereas a dual frequency scheme employs cascaded SHG and optical parametric amplification (SHG/OPA). Exact theoretical solutions and numerical calculations show cascadable amplification and digital on/off switching. A new optical phenomenon of nonlinear transparency is predicted by the theoretical solutions and confirmed by the numerical solutions in each scheme of the cascaded SHG/iSHG and SHG/OPA. The single and dual frequency configurations satisfy the cascadability and fan-out criteria with power transfer ratios of 4.838 and 52.26 and power amplification factors of 48.38 and 522.6, respectively. These results indicate transistor-like performance at input powers in the milliwatt range, readily supplied by
laser diodes. The proposed structure establishes a physically feasible and practically scalable route to optical transistors operating at high speed and low power for integrated photonic
circuits, with broad applications in all optical communication and computing.
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Fluid Dynamics
Structures of elastoinertial turbulence in pipe flow
Manish Kumar and Michael D. Graham
Elastoinertial
turbulence (EIT) is a self-sustaining chaotic state resulting from the interplay between inertia and elasticity in the flow of dilute polymeric solutions, and its emergence is believed to limit the achievable drag reduction in
turbulence flow using
polymer additives. In the present study, we introduce a viscoelastic variant of spectral proper orthogonal decomposition (VESPOD) that decomposes velocity and polymeric stress fields of EIT together into well-defined orthogonal oscillating modes such that the decomposition is optimal in the terms of the total mechanical energy of the flow. Using this technique, we investigate the dominant coherently evolving structures underlying the dynamics of EIT in axisymmetric pipe flow. By analyzing distinct peaks in the leading
eigenvalue of the VESPOD
eigenvalue spectrum, we find that the dynamics of EIT in pipe flow is dominated by three distinct families of traveling waves, where the higher wavenumber structures of each family are simple harmonics of their respective fundamental waves. The radial velocity fields of the traveling waves are characterized by the formation of large-scale structures spanning the pipe radial direction. However, the polymeric stress fields corresponding to them are characterized by the formation of thin inclined sheets of high stress fluctuations at the critical layers of the respective waves, i.e.~ the locations where the wave speed of the VESPOD mode matches the mean streamwise velocity. Additionally, these sheets exhibit nested structures, where the polymeric sheets of faster waves are confined by those of the immediately slower waves.
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Physics and Society · Cross-listed from cs.SI
Community-Size Biases in Statistical Inference of Communities in Temporal Networks
Theodore Y. Faust, Arash A. Amini and Mason A. Porter
In the study of time-dependent (i.e., temporal) networks, researchers often examine the
evolution of communities, which are sets of densely connected sets of nodes that are connected sparsely to other nodes. An increasingly prominent approach to studying community structure in temporal networks is statistical inference. In the present paper, we study the performance of a class of statistical-inference methods for community detection in temporal networks. We represent temporal networks as multilayer networks, with each layer encoding a time step, and we illustrate that statistical-inference models that generate community assignments via either a uniform distribution on community assignments or discrete-time Markov processes are biased against generating communities with large or small numbers of nodes. In particular, we demonstrate that statistical-inference methods that use such generative models tend to poorly identify community structure in networks with large or small communities. To rectify this issue, we introduce a novel statistical model that generates the community assignments of the nodes in given layer (i.e., at a given time) using all of the community assignments in the previous layer. We prove results that guarantee that our approach greatly mitigates the bias against large and small communities, so using our generative model is beneficial for studying community structure in networks with large or small communities. Our code is available at https://github.com/tfaust0196/TemporalCommunityComparison.
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Optics · Cross-listed from cond-mat.mes-hall
Anomalous valley Hall dynamics of exciton-polaritons
Xingzhou Chen, Yuanjun Guan, Areg Ghazaryan et al. (+6 more)
The valley degree of freedom in atomically thin transition-metal dichalcogenides provides a natural binary index for information processing.
Exciton-polaritons formed under strong light-matter coupling offer a promising route to overcome the limited lifetime and transport of bare valley
excitons. Here we report an anomalous optical valley
Hall effect in a monolayer WS2
exciton-polariton system. Using polarization- and time-resolved real-space imaging, we directly visualize a
symmetry-breaking spatial separation of polaritons from opposite valleys under linearly polarized excitation, accompanied by an ultrafast
Hall drift velocity on the order of 10^5 m/s. This behaviour cannot be accounted for by conventional cavity-induced mechanisms and instead points to a strain-induced synthetic pseudomagnetic field acting on the excitonic component of polaritons. Our results establish
exciton-polaritons as a high-speed and optically accessible platform for valley transport, opening pathways towards tunable valleytronic and topological photonic devices.
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All authors Xingzhou Chen, Yuanjun Guan, Areg Ghazaryan, Shiran Sun, Lingxiao Yu, Ruitao Lv, Artem Volosniev, Zheng Sun, Jian Wu
Optics
Burst Mode Ultrafast Laser Welding of Sapphire and Fe-36Ni Alloy with Non-optical Contact Condition
Yu Wang, Nan Li, Yuxuan Li et al. (+8 more)
Ultrafast
laser welding provides a promising approach for high precision integration of transparent and metallic materials. However, its practical application remains constrained by the precise regulation of the interfacial gap. This study investigates the interfacial response and bonding mechanism of sapphire and Fe-36Ni
alloy joints under controlled non-optical contact conditions using burst mode ultrafast
laser irradiation. A
polymer interlayer was introduced between naturally stacked samples to establish a variable interfacial gap, allowing systematic evaluation of gap-dependent morphology, melting behavior, and elemental transport. By redistributing the pulse energy into sequential sub-pulses, the burst mode reconstructs the temporal energy-deposition process, yielding enhanced
plasma-material coupling and stable thermal accumulation. Compared with single pulse irradiation, burst mode sustains continuous bonding across gaps exceeding 10 um–far beyond the failure threshold of the single pulse mode–and forms a fusion zone 82% larger. Fracture surface and cross-sectional analyses of SEM and EDS results confirm that sequential sub-pulses promote extensive sapphire melting, droplet-driven gap bridging, and enhanced Al-Fe interdiffusion at the interface. These results provide a scientific basis for high-gap-tolerance ultrafast
laser welding and scalable integration of transparent-metal hybrid components in advanced optoelectronic and precision engineering applications.
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All authors Yu Wang, Nan Li, Yuxuan Li, Yitong Chen, Qingwei Zhang, Jianing Zhao, Zhe Lin, Zihui Dong, Guochang Jiang, Zhengqiang Zhu, Shanglu Yang
Plasma Physics
A kinetic-moment framework for electron energy dynamics in capacitively coupled plasmas: absorption, conversion, transport, and dissipation
Jianxiong Yao, Zeduan Zhang, Feng He et al. (+3 more)
Understanding electron energy dynamics in low-temperature
plasmas such as capacitively coupled
plasmas (CCPs), including energy absorption, conversion, transport, and dissipation, is essential for interpreting discharge physics and process applications. We propose a kinetic-moment framework based on particle-in-
cell/Monte Carlo collision (PIC/MCC) simulations. The framework reconstructs the first three velocity moments of the Boltzmann equation directly from PIC/MCC data and enables a quantitative, self-consistent description of electron energy dynamics in low-pressure CCPs. To clarify energy conversion among electromagnetic energy, electron fluid kinetic (mechanical) energy, and electron thermal (internal) energy, we further separate the total energy transport equation into kinetic- and thermal-energy equations. We find that, at low pressure, electrons gain directed kinetic energy in the sheath and convert it locally into thermal energy through pressure-strain interaction and collisions. Thermal energy is then transported into the bulk and is dissipated mainly by inelastic electron-neutral collisions. We further decompose pressure-strain interaction into reversible pressure dilatation and irreversible viscous-like dissipation, which correspond to conversion driven by volumetric compression or expansion and by shear deformation, respectively. This decomposition reveals a significant thermalization channel beyond collisions. More broadly, the results show coexistence of localized kinetic-to-thermal conversion near the sheath and nonlocal energy transport from the sheath to the bulk dominated by microscopic heat flux. The heat flux deviates strongly from
Fourier's law based on local temperature gradients. This framework provides a clear fluid description with kinetic fidelity and offers a practical tool for analyzing energy
evolution in nonequilibrium
plasmas.
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All authors Jianxiong Yao, Zeduan Zhang, Feng He, Jinsong Miao, Jiting Ouyang, Bocong Zheng
Optics
Adaptive information-maximization encoding for ghost imaging–A general Bayesian framework under experimental physical constraints
Jianshuo Sun, Chenyu Hu, Zunwang Bo et al. (+5 more)
Ghost imaging (GI) has demonstrated diverse imaging capabilities enabled by its encoding-decoding-based computational imaging mechanism. Accordingly, information-theoretic studies have emerged as a promising avenue for probing the fundamental performance bounds of of GI and related computational imaging paradigms. However, the design of information-theoretically optimal encoding strategies remains largely unexplored, primarily due to the intractability of the prior probability density function (PDF) of an unknown scene. Here, by leveraging the ability of recursively estimating the PDF of the object to be imaged via
Bayesian filtering, we propose to establish an adaptive information-maximization encoding (AIME) design framework. Based on the adaptively estimated posterior PDF from previously acquired measurements, the expected information gain of subsequent detections is evaluated and maximized to design the corresponding encoding patterns in a closed-loop manner. Within this framework, the theoretical form of the information-optimal encoding under representative physical constraints is analytically derived. Corresponding experimental results show that, GI systems employing information-optimal encoding achieve markedly improved imaging performance compared with conventional fixed point-to-point imaging without relying on additional heuristic regularization schemes, particularly in low signal-to-noise ratio regimes. Moreover, the proposed strategy consistently enables significantly enhanced information acquisition capability compared with existing encoding strategies, leading to substantially improved imaging quality. These results establish a principled information-theoretic foundation for optimal encoding design in computational imaging paradigms,provided that the forward model can be accurately characterized.
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All authors Jianshuo Sun, Chenyu Hu, Zunwang Bo, Zhentao Liu, Mengyu Chen, Longkun Du, Weitao Liu, Shensheng Han
Plasma Physics
Density Limit Experiments and Core-localized Kinetic MHD Activities in HL-2A Ohmic Heating Plasmas
L. W. Hu, W. Chen, P. W. Shi et al. (+12 more)
The density limit is a mysterious barrier to
magnetic confinement
nuclear fusion, and is still an unresolved issue. In this paper, we will present the experimental results of the density limit and core-localized kinetic MHD instabilities on HL-2A. Firstly, the high density shots with $ne/ne_G>1$ have been achieved by the conventional gas-puff fuelling method in Ohmic heating
plasmas, and the corresponding duration time is close to $t\sim500$ ms ($\sim$ $30\tau_E$), where $\tau_E$ is the global energy confinement time. Secondly, it is found for the first time that there are kinetic MHD instabilities in the core
plasmas while $ne/ne_G\sim1$. The analysis suggests that the core-localized MHD activities belong to Alfvénic ion temperature gradient (AITG) modes or kinetic ballooning modes (KBM), and firstly it is found on experiment that they trigger the minor or major disruption of bulk
plasmas while the density profile is peaked. These new findings are of great importance to figure out and understand the origin of the density limit.
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All authors L. W. Hu, W. Chen, P. W. Shi, T. Long, J. Q. Xu, R. R. Ma, Y. G. Li, L. M. Yu, X. Yu, M. Jiang, T. F. Sun, J.M. Gao, Y. B. Dong, X. L. Zhu, Z. B. Shi
Biological Physics
Swelling-Induced Stress-Assisted Transfer of Nanodiamond Arrays with a PVA Carrier Tape for Conformal Bio-Integrated Sensing and Labelling
Luyao Zhang, Lingzhi Wang, Xinhao Hu et al. (+7 more)
The conformal integration of nitrogen-vacancy (NV) center nanodiamond arrays onto soft, hydrated, curvilinear biological interfaces remain a fundamental challenge for in vivo
quantum sensing and imaging. Conventional transfer techniques often fail due to reliance on high temperature, corrosive chemicals, or mechanical peeling, leading to pattern damage, low fidelity, or poor biocompatibility. Here, we report a transfer strategy utilizing polyvinyl alcohol (PVA) carrier soluble tape, enabling rapid, residue-free, high-fidelity transfer of nanodiamond patterns onto diverse biointerfaces. The success of this method is rooted in a unique "hydrate-soften-expand-self-peel" mechanism of the soluble tape with PVA backing. In situ mechanical tracking reveals non-uniform PVA swelling upon hydration generates transient local normal and shear stresses at the interface. These stresses delaminate the tape within 3 minutes at room temperature while promoting adhesion of the nanodiamond array to the substrate. In contrast, conventional water-soluble tapes with composite structures undergo passive dissolution and collapse, causing residue contamination and reduced efficiency. Leveraging this mechanism, we achieve conformal patterning on ultra-soft hydrogels (~0.6 kPa) and highly curved bio-surfaces (hair, 100 {\mu}m^-1). Additionally, we demonstrate a dual-identity verification system integrating data storage and physical unclonable functions on a hydrogel contact lens. This work provides a versatile tool for bio-interface engineering and a general framework for gentle, efficient transfer of functional nanomaterials.
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All authors Luyao Zhang, Lingzhi Wang, Xinhao Hu, Yip Tai Nam, Mingzhe Sun, Jixiang Jing, Lizhi Xu, Yuan Lin, Yong Hou, Zhiqin Chu
Atomic Physics · Cross-listed from quant-ph
Optimized Slice-Phase Control of Mirror Pulse in Cold-Atom Interferometry with Finite Response Time
Xueting Fang, Doudou Wang, Kun Yuan et al. (+6 more)
Atom interferometers require both high efficiency and robust performance in their mirror pulses under experimental inhomogeneities. In this work, we demonstrated that
quantum optimal control designed mirror pulse significantly enhance interferometer performance by using novel adaptive sliced structure. Using gradient ascent pulse engineering (GRAPE), optimized mirror pulse for a Mach-Zehnder light-pulse atom interferometer was designed by discretizing the control into non-uniform phase slices. This design broadened the tolerence to experimentally relevant variations in detuning $[-\Omega_0,\Omega_0]$ and Rabi frequency $[0.1\times\Omega_0,1.9\times\Omega_0]$ ($\Omega_0=2\pi\times25$ kHz), while maintaining high transfer efficiency even when the response-time delays up to 1.6 $\rm{\mu s}$. The optimized pulse was found to be robust to coupling inhomogeneity and velocity spread, offering a significant improvement in robustness over conventional pulse. The adaptive pulse slicing method provides a minimalist strategy that reduces experimental complexity while enhancing robustness and scalability, offering an innovative scheme for
quantum optimal control in high precision atom interferometry.
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All authors Xueting Fang, Doudou Wang, Kun Yuan, Jie Deng, Qin Luo, Xiaochun Duan, Minkang Zhou, Lushuai Cao, Zhongkun Hu
Optics
Head-wearable Holographic Head-mounted Display with 6 Degrees of Freedom
Taichi Sakakihara, Teppei Jodo, Seok Kang et al. (+1 more)
A head-mounted display (HMD) using holography technology (holo-HMD) is expected to be the next generation of HMDs capable of reducing three-dimensional sickness. In HMDs, it is important to generate images that respond to head movement in real time. However, in holo-HMDs, generation of hologram data in real time is difficult due to the large computational resources required. This paper proposes a fast calculation
algorithm for generating hologram data for holo-HMDs, which requires low computational power. A holo-HMD supporting six degrees of freedom was also developed using this
algorithm and it was confirmed that it obtained reconstructed images with six degrees of freedom in real time (30 fps or more).
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All authors Taichi Sakakihara, Teppei Jodo, Seok Kang, Yuji Sakamoto
Optics
{\sigma}h-Broken Induced Topological quasi-BIC
Yongqi Chen, Chaofeng Xie, Tongtong Zhu et al. (+2 more)
Transitions from bound states in the continuum (BICs) to quasi-BICs (qBICs) are typically realized by introducing in-plane asymmetry, including permittivity asymmetry ({\epsilon}-qBICs) and geometry asymmetry (g-qBICs). Here, we demonstrate that when the in-plane
symmetry is rigorously kept, the transition can also be occurred, provided the out-of-plane asymmetry is designed, which is called {\sigma}h -qBICs in this work. When the {{\sigma}h
symmetry is gradually broken, the system undergoes a topological phase transition characterized by a Zak phase inversion, leading to a band inversion between quadrupole and dipole modes. This process not only enables controlled radiation coupling of BICs but also introduces a defect-immune qBIC regime. Our findings establish a general mechanism for engineering high-Q resonances and topologically robust plasmonic cavities.
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All authors Yongqi Chen, Chaofeng Xie, Tongtong Zhu, Weiqiang Ding, Yurui Fang
Plasma Physics
Discovery of Density Limit Disruption Induced by Core-localized Alfv${\'e}$nic Ion Temperature Gradient Instabilities in a Tokamak Plasma
Wei Chen, Liwen Hu, Jianqiang Xu et al. (+17 more)
To achieve a high energy gain, the fusion reactor
plasma must reach a very high density. However, the tokamak
plasmas ofen undergo disruption when the density exceeds the Greenwald density. The density limit disruption in tokamak
plasmas is a mysterious barrier to
magnetic confinement
nuclear fusion, and hitherto, is still an unresolved issue. Over the past several years, the high density experiments with Greenwald density ratio $n_e/n_{eG}\sim1$ has been carried out using the conventional gas-puff fuelling method in HL-2A NBI and Ohmically heated
plasmas. It is found for the first time that there are multiple-branch MHD instabilities in the core
plasmas while $n_e/n_{eG}>0.85$. The simulation analysis suggests that the core-localized magnetohydrodynamics (MHD) activities belong to Alfv${\'e}$nic ion temperature gradient (AITG) modes, and on experiment firstly, it is discovered that they trigger the minor or major disruption of bulk
plasmas while the density is peaked. These new findings are of great importance to figure out and understand the origin of density limit disruptions, as well as to forecast and avoid them for future fusion rectors.
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All authors Wei Chen, Liwen Hu, Jianqiang Xu, Ruirui Ma, Peiwan Shi, Rui Ke, Ting Long, Zhiyong Qiu, Haotian Chen, Xiaoxue He, Yonggao Li, Liming Yu, Wenping Guo, Min Jiang, Jinming Gao, Xin Yu, Zhengji Li, Huiling Wei, Deliang Yu, Zhongbing Shi
Optics · Cross-listed from quant-ph
Bright Pulsed Squeezed Light for Quantum-Enhanced Precision Microscopy
Alex Terrasson, Lars Madsen, Joel Grim et al. (+1 more)
Squeezed states of light enable enhanced measurement precision by reducing noise below the standard
quantum limit. A key application of squeezed light is nonlinear microscopy, where state-of-the-art performance is limited by photodamage and
quantum-limited noise. Such microscopes require bright, pulsed light for optimal operation, yet generating and detecting bright pulsed squeezing at high levels remains challenging. In this work, we present an efficient technique to generate high levels of bright picosecond pulsed squeezed light using a $\chi^2$ optical parametric amplification process in a waveguide. We measure $-3.2~\mathrm{dB}$ of bright squeezing with optical power compatible with nonlinear microscopy, as well as $-3.6~\mathrm{dB}$ of
vacuum squeezing. Corrected for losses, these squeezing levels correspond to $-15.4^{+2.7}_{-8.7}~\mathrm{dB}$ of squeezing generated in the waveguide. The measured level of bright amplitude pulsed squeezing is to our knowledge the highest reported to date, and will contribute to the broader adoption of
quantum-enhanced nonlinear microscopy in biological studies.
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All authors Alex Terrasson, Lars Madsen, Joel Grim, Warwick Bowen
Optics
An ultrafast diamond nonlinear photonic sensor
Daisuke Sato, Junjie Guo, Takuto Ichikawa et al. (+6 more)
The integration of light and materials technology is key to the creation of innovative sensing technologies. Sensing of electric and
magnetic fields, and temperature with high spatio-temporal resolution is a critical task for the development of the next-generation of nanometer-scale
quantum devices. Color centers in diamonds are attractive for potential applications owing to their characteristic
quantum states, although they require metallic contacts for the introduction of external microwaves. Here, we build an ultrafast diamond nonlinear photonic sensor to assess the surface electric field; an electro-optic sensor based on nitrogen-vacancy centers in a diamond nanotip breaks the spatial-limit of conventional pump-probe techniques. The 10-fs near-infrared optical pulse modulates the surface electric field of a 2D transition metal dichalcogenide and we monitor the dynamics of the local electric field at nanometer-femtosecond spatio-temporal resolutions. Our nanoscopic technique will provide new horizons to the sensing of advanced nano materials.
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All authors Daisuke Sato, Junjie Guo, Takuto Ichikawa, Dwi Prananto, Toshu An, Paul Fons, Shoji Yoshida, Hidemi Shigekawa, Muneaki Hase
Applied Physics
Experimental Demonstration of Nonlinear Photoconductive Gain in N-Doped $\beta$-Ga$_2$O$_3$ Devices
Vikash K. Jangir and Sudip K. Mazumder
Photoconductive devices based on ultra-wide-bandgap (UWBG) materials offer a promising pathway toward compact, high-voltage (HV) optoelectronic and optical sensing in harsh environments. In this Letter, we report field-tunable nonlinear photoconductive gain in vertical $\beta$-Ga$_2$O$_3$ photoconductive devices under sub-bandgap visible-light excitation. The devices were fabricated on a $5.6\,\mu\text{m}$-thick nitrogen-doped semi-insulating $\beta$-Ga$_2$O$_3$ epilayer grown on a conductive Sn-doped substrate and characterized under $445\,\text{nm}$ continuous-wave illumination. A distinct transition from linear to nonlinear photoconductive behavior is observed at a threshold electric field of approximately $0.67\,\text{MV/cm}$, resulting in an approximately $20\times$ enhancement in photocurrent. Complementary TCAD simulations indicate strong electric-field localization and a rapid increase in impact-ionization generation at high bias, suggesting that impact-ionization–assisted carrier multiplication contributes to the observed gain. These results demonstrate a high-field visible-light photoconductive detection mode in $\beta$-Ga$_2$O$_3$ enabled by defect-assisted transport, providing a pathway toward field-tunable gain photodetectors operating without deep-ultraviolet (DUV) excitation.
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