Optics · Cross-listed from quant-ph
Fixed-order postselected CHSH reference acquisition for parity-constrained spatial-mode qubits on a commercial cloud photonic processor
Emma Tully, Jonathan Washburn and Megan Simons
We report a fixed-order Clauser-Horne-Shimony-Holt (CHSH) acquisition and reporting protocol for two encoded photonic
qubits on Quandela's commercial, cloud-accessible Belenos processor, executed end-to-end by external users through the public cloud interface. Each logical
qubit is a two-dimensional spatial-mode subspace in the seven-dimensional zero-sum sector of an eight-mode single-
photon register, and a target postselected linear-optical controlled-$Z$ (ideal success probability $1/9$) couples the registers on $16$ of $24$ modes. The primary quantity is the operational CHSH score $S$ on accepted logical coincidences, with each complete four-setting pass as the experimental unit. Eight sequential same-day passes each gave a raw score above $2$; session means were $2.40$ and $2.58$ (sample standard deviations $0.15$ and $0.03$), with excess dispersion $Q/\nu=6.1$ ($\nu=7$). Count-pooled secondary descriptors are $S_{\mathrm{count}}=2.485\pm0.019$ and a fixed-ratio efficiency-reweighted model scenario $S^{\mathrm{rw}}_{\mathrm{count}}=2.380\pm0.021$, whose weakest reweighted pass ($2.040\pm0.062$) overlapped $2$ within $1\sigma$. The reweighting is an archived-metadata model scenario, not a corrected platform score; an ad hoc $\kappa\in[1.2,1.8]$ stress scan (not a calibrated uncertainty band) spans $2.341$-$2.441$. Setting order was fixed, the compiled mapping was not returned, and residual remote-setting marginals remain, so the data support an operational reference acquisition rather than an
entanglement-witness or cross-platform benchmarking claim. The parity-check terminology labels the encoding subspace; no syndrome measurement was performed. Count records, job identifiers,
circuit-construction code, and analysis are openly archived with content hashes for the submitted targets.
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Optics
Internal Temperature and Center-of-Mass Dynamics of a Levitated Nanoparticle: A Simulator
Jailson Sales Araújo, Lucas Rodrigo Mendicino, Lina Wölcken et al. (+2 more)
This document describes the models used in the simulator for the dynamics of a nanoparticle levitated in a Paul trap combined with an optical tweezer. The focus is the coupled
evolution between the center-of-mass motion, the internal temperature of the particle, and the effective temperature associated with the mechanical motion. The formulation includes electric and optical forces, gas damping, thermal noise, heat exchange with the gas, thermal radiation, active optical absorption, parasitic absorption, anti-Stokes cooling, and absorption/emission spectra obtained from generic presets, generated bands, or experimental tables loaded by the user
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All authors Jailson Sales Araújo, Lucas Rodrigo Mendicino, Lina Wölcken, Santiago Gliosca, Christian Tomás Schmiegelo
Optics · Cross-listed from cond-mat.mes-hall
Strong photoresponse of edge two-dimensional electrons in a magnetic field
Sergey A. Mikhailov and Wladislaw Michailow
Electrons in two-dimensional electron gases in the presence of an out-of-plane
magnetic field propagate along the edge with a high velocity of the order of the Fermi velocity. Under microwave and terahertz radiation,
photon absorption by these electrons provides a pathway to realising sensitive radiation detection. Here, we develop a detailed
quantum theory of the photocurrent generated in such a system by an incident electromagnetic wave and propose an experimental geometry for observing the predicted phenomenon. By using suitably arranged radiation confinement structures, a strong photocurrent generation efficiency can be obtained. We also demonstrate that the resulting photoresponse in III-V
semiconductor structures can be orders of magnitude higher than that measured in
graphene.
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Optics
Label-Free Deep-Tissue Peripheral Nerve Detection with a Handheld Multimodal OCT Probe and NerveDetNet
Yihan Wang, Ruilin You, Shaobai Li et al. (+4 more)
Peripheral nerves buried beneath intact tissue are difficult to visualize during surgery and remain inaccessible to white light wide-field imaging and other surface optical imaging methods. Existing OCT nerve studies have largely relied on exposed nerves or polarization contrast with limited depth penetration, restricting their value for subsurface intraoperative guidance. Here, we introduce, to our knowledge, the first label-free framework for detecting peripheral nerves beneath unopened tissue and resolving their depth using intensity-based OCT structural signatures alone. The framework combines a handheld
multimodal probe, integrating swept-source OCT with co-registered white light and autofluorescence imaging, with a “confirm-then-capture” workflow designed for practical surgical use. To enable efficient analysis of sparsely sampled OCT volumes, we develop NerveDetNet, a lightweight 2.5D segmentation network that recovers weak and spatially displaced nerve signals by incorporating spatial context, frame-order information, and shift-tolerant correlations across frames through a dedicated nerve feature correlation module. In ex vivo tissue experiments, NerveDetNet consistently outperformed six representative 2D baselines across all frame spacings, achieving a Dice score of 0.725 under the sparsest sampling condition while using approximately half the model parameters. End-to-end validation demonstrated localization of nerves invisible at the surface and depth-resolved detection up to 1.3–1.4~mm below the tissue surface, with OCT derived depth maps overlaid directly onto the surgical view. Together, these results establish a practical label-free approach for subsurface nerve visualization that supports intraoperative compatibility, enables efficient sparse-volume analysis, and provides depth-resolved guidance without tissue opening, contrast
agents, or nerve exposure.
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All authors Yihan Wang, Ruilin You, Shaobai Li, Jiabin Chen, Bofan Song, Anh D. Le, Rongguang Liang
Optics
Intracavity THz generation using a thin lithium niobate plate in a compact Kerr-lens mode-locked Yb:CALGO bulk oscillator
Mohsen Khalili, Jokūbas Pimpė, Yicheng Wang et al. (+5 more)
We demonstrate intracavity terahertz (THz) generation via optical rectification in a 50-m-thick lithium niobate
crystal placed inside a compact diode-pumped Kerr-lens mode-locked (KLM) Yb:CALGO bulk oscillator. The oscillator operates at a repetition rate of 85 MHz and delivers 83-fs pulses with up to 71 W of average intracavity power, obtained with only 21.4 W of low-cost multimode diode pump power. We generate single-cycle THz pulses with a spectrum extending up to 3 THz, detected by electro-optic sampling with 60 dB dynamic range within 156 s of measurement time (313 averaged traces) and up to 120 W of THz average power. This work combines the high damage threshold, power-handling capability, and cost-effectiveness of thin LN plates with simplicity, compactness, and low-cost multimode diode-pumped solid-state bulk
lasers, offering an attractive alternative for high-repetition-rate THz time-domain spectroscopy systems.
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All authors Mohsen Khalili, Jokūbas Pimpė, Yicheng Wang, Julius Vengelis, Kore Hasse, Sergiy Suntsov, Detlef Kip, Clara J. Saraceno
Optics
Shaper-based dispersion scan for the characterization of polarization-shaped laser fields
Darius Köhnke, Jan-Erik Havekost, Nick Robin Rother et al. (+4 more)
We present a pulse-shaper-based dispersion-scan (d-scan) framework for the combined generation and characterization of polarization-tailored femtosecond
laser fields. By integrating a programmable $4f$ pulse shaper with polarization-resolved d-scan measurements, the framework enables the programmable synthesis and reconstruction of complex time-dependent polarization states. We demonstrate its capabilities for several classes of vector fields, including counter-rotating circularly polarized pulse pairs, oppositely chirped counter-rotating circularly polarized pulses, polarization-gate pulses, and multi-pulse sequences utilizing
polynomial, periodic and discrete spectral phase functions. The reconstructed temporal electric fields and time-dependent ellipticities show excellent agreement with the simulated target fields and accurately reproduce the defining features of each pulse class. By combining the versatility of programmable pulse shaping with the robustness of the d-scan technique, this approach provides a flexible platform for the generation and validation of polarization-tailored ultrashort
laser fields in ultrafast photonics and light-matter interaction studies.
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All authors Darius Köhnke, Jan-Erik Havekost, Nick Robin Rother, Christoph Kuntze, Lars Englert, Tim Bayer, Matthias Wollenhaupt
Optics
Fully Fiber-Integrated 3D-Printed Probes for Plug-and-Play Endoscopic Optical Coherence Tomography
Yihan Wang, Ruilin You, Jiabin Chen et al. (+5 more)
Miniature probes extend optical coherence
tomography (OCT) into lumens and other confined spaces, but conventional implementations often rely on multiple distal components, fiber processing, and probe-specific interferometer matching. Here, a fully fiber-integrated OCT (F2I-OCT) architecture is demonstrated in which two-
photon microfabrication defines not only the terminal imaging optic, but the complete distal optical and interferometric architecture within a single fiber-mounted element. Beam expansion, side-view redirection, common-path reference generation, and terminal imaging are physically integrated while remaining independently designable. This architecture transfers complexity from component fabrication and interferometer matching into three-dimensional optical design, reducing assembly to a print-and-bond process and enabling plug-and-play exchange on the same OCT platform. Terminal optics can be adapted to different working distances, surrounding media, and wavefront transformations without redesigning the upstream architecture. Twenty assembled probes exhibit returned-reference and side-viewing-output power standard deviations of 0.149 dB and 0.071 dB, respectively. The system achieves 93.1 dB sensitivity and enables ex vivo imaging of airway and dental structures. The combination of a common plug-and-play architecture with broad optical design freedom provides a versatile platform for endoscopic and confined-space imaging across diverse biomedical and technical environments.
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All authors Yihan Wang, Ruilin You, Jiabin Chen, Bofan Song, Zien Feng, Paula Patricia Villarreal, Gracie Vargas, Rongguang Liang
Optics
Enhanced Third-Harmonic Generation in a Bound State in the Continuum Assisted Multiband All-Dielectric Metasurface
Partha Mondal, Hadeel Alamoudi, Rodrigo P. Sanchez et al. (+4 more)
Multiband Fano resonances are demonstrated in the near-infrared (near-IR) using an all-dielectric metasurface whose unit
cell consists of four silicon nanoblocks on a glass substrate. An in-plane asymmetry triggers
symmetry-protected quasi-bound states in the continuum (QBICs), producing multiple high-Q resonances. Their origin is identified through multipolar decomposition of the scattering cross section and field distributions at the resonances. The strong field localization at these resonances enables efficient multiband third-harmonic (TH) generation in the ultraviolet (UV), with a maximum simulated conversion efficiency of $8.5 \times 10^{-3}$ at a peak pump intensity of $1.6\,\mathrm{GW/cm^{2}}$. The metasurface is fabricated in symmetric and asymmetric configurations, and its linear and nonlinear responses are measured under normal incidence. A TH conversion efficiency of $1.2 \times 10^{-6}$ is obtained at a peak pump intensity of $3.25\,\mathrm{GW/cm^{2}}$. These results establish a route to multiband photonic devices, including multiwavelength
lasers, multiband harmonic generation, and single-
photon sources for
quantum photonics.
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All authors Partha Mondal, Hadeel Alamoudi, Rodrigo P. Sanchez, Redha H. Al Ibrahim, Boon S. Ooi, Iman Roqan, Hakan Bagci
Optics
Nonlinear wave dynamics in photonic time crystals
Fabio Biancalana
Maxwell's wave equation in the presence of a cubic nonlinearity and a periodically time-varying refractive index (a photonic time
crystal) is reduced, for spatially monochromatic waves, to a nonlinear Mathieu equation. Near the principal momentum gap this equation admits an autonomous two-dimensional reduction whose complete
Hamiltonian phase portrait can be obtained analytically. We derive the two homoclinic separatrices corresponding to temporally localised momentum gap
solitons, identify the nonlinear centres and the critical
Hamiltonian value $H_c$, and calculate the point of maximum linear parametric gain. We then consider spatially localised pulses and show how the nucleation of multiple spatiotemporal gap
solitons can produce a broad supercontinuum in momentum space; for stronger seeds, transient extreme nonlinear localisation can accompany an abrupt additional broadening of this momentum spectrum. These results establish a direct connection between Floquet amplification, nonlinear saturation, homoclinic dynamics, and momentum space spectral broadening in nonlinear photonic time
crystals.
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Optics · Cross-listed from physics.ins-det
Optical Characterization Measurements of Commercial Polyvinyltoluene Scintillators for Accurate Geant4 Detector Modeling
Fergus Martin Huggins, Micah S. Johnson and Matthew Quinn Buckner
Accurate Monte Carlo simulation of plastic scintillator detectors requires precise wavelength-dependent optical properties. We present the first comprehensive measurements of wavelength-dependent refractive index $n(\lambda)$ and bulk absorption length $L_{\mathrm{abs}}(\lambda)$ for six commercial polyvinyltoluene (PVT)-based scintillators (Saint Gobain BC-400, BC-404, BC-408, BC-418, BC-422, and BC-430) across the 370-660 nm range. Using a precision refraction apparatus and variable-thickness transmission measurements, we characterize material-specific dispersion that deviates substantially from both the manufacturer specification and literature values for pure PVT. Validation simulations of a BC-422 detector demonstrate a 7.2% reduction in detected
photon counts when using our measured $n(\lambda)$ compared to the constant manufacturer value, highlighting the practical importance of accurate optical property data for detector design and calibration. We successfully measure absorption lengths for BC-430 across most of the visible spectrum (2.2-12.4 mm) and for all materials at 372 nm (21-38 mm), while establishing lower bounds exceeding 750 mm for weakly absorbing formulations at longer wavelengths.
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Optics · Cross-listed from quant-ph
Heuristic Lookahead Distillation Protocol Search
Matthew Barber and Stefano Pirandola
Bipartite
qubit entanglement distillation is the process of converting noisy ebits into pure ebits using only local operations and classical communication. This is a core operation for
quantum repeaters, enabling such crucial tasks as long-distance
quantum communication and distributed
quantum computing. In this work, we introduce a method for searching for
entanglement distillation protocols and, using this technique, distil
qubit Werner states at a higher rate than could be achieved using previously discovered protocols. In particular, we demonstrate the advantage of our new
distillation strategy by improving the best-known lower bound for the two-way-assisted
quantum capacity of the
qubit depolarising channel across a wide range of channel parameters, making progress in one of the long-standing problems of
quantum information theory.
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Optics
All-optical switching of nonlinear structured light in crystal-engineered van der Waals materials
Paolo Valisa, Marc Richstaetter, Bianca Sanfilippo et al. (+9 more)
The orbital angular momentum (OAM) of light is a discrete, unbounded degree of freedom that underpins mode-multiplexed communications and high-dimensional
quantum photonics. Yet, dynamic OAM control remains dependent on bulky free-space optics or cascaded architectures that separate switching from wavefront shaping, hindering nanoscale integration. Here, we engineer artificial van der Waals
crystals from rhombohedrally stacked (3R) MoS$_2$, in which spatial control of the local
crystal orientation imprints a nonlinear
geometric phase onto the second-harmonic (SH) field, enabling background-free generation of SH
vortex beams in an ultrathin (46 nm) van der Waals platform. Leveraging the C$_{3v}$
symmetry of 3R-MoS$_2$, we demonstrate monolithic, all-optical switching with sub-optical-cycle precision between Hermite-Gauss-like and Laguerre-Gaussian
vortex SH beams with opposite topological charges ($l=\pm1$). Our results establish artificial 3R-MoS$_2$
crystals as a monolithic platform for the generation and all-optical reconfiguration of nonlinear structured light at the nanoscale, advancing active nanophotonic sources for integrated classical and
quantum photonic technologies.
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All authors Paolo Valisa, Marc Richstaetter, Bianca Sanfilippo, Benedikt Ursprung, Zhi Hao Peng, Victoria Quiros-Cordero, Francesco Gucci, Xiaoyang Zhu, P. James Schuck, Giulio Cerullo, Luca Carletti, Chiara Trovatello
Optics
In-situ Adjoint Wave Control in Reconfigurable Non-Hermitian Nonlinear Systems
John Guillamon, William Tuxbury, Cheng-Zhen Wang et al. (+3 more)
Complex multipath environments are usually avoided in wave-based information processing because repeated scattering creates many interfering propagation paths, obscuring controllability and generating extreme sensitivity to perturbations. The addition of nonlinear mechanisms fundamentally alters the wave-control landscape by breaking the superposition principle that underpins most wave-management strategies. Here, we show that these two apparent impediments – multipath complexity and nonlinearity – can instead be harnessed as key resources for physical optimization. We demonstrate an in-situ adjoint optimization protocol in a wave-chaotic platform incorporating a single localized nonlinear defect, in which the system itself performs both the forward and the adjoint propagations required for gradient evaluation. Recurrent multipath returns repeatedly expose the wave to the defect, producing from a minimal hardware a rich nonlinear input-output map with many pathway-mediated degrees of freedom. At the same time, a suitable adjoint excitation enables direct extraction of the sensitivities from measurements alone, without a digital twin or conventional numerical backpropagation. We experimentally validate the protocol on a minimal nonlinear multipath platform composed of incommensurate coaxial cables connected via T-junctions, one of which hosts a diode-loaded cavity. Our approach opens a route to adaptive wireless communications, imaging and analog intelligence in complex, partially unknown environments where conventional modeling is impractical.
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All authors John Guillamon, William Tuxbury, Cheng-Zhen Wang, Owen Miller, Zin Lin, Tsampikos Kottos
Optics · Cross-listed from physics.comp-ph
Characteristic Mode Analysis of Plasmonic Nanostructures Using Hydrodynamic Volume Integral Equation
Meruyert Khamitova, Ran Zhao, Doolos Aibek Uulu et al. (+2 more)
Metallic nanostructures confine electromagnetic fields at subwavelength scales, making them attractive as plasmonic nanoantennas. At these scales, the response of metals becomes nonlocal, and the hydrodynamic model is widely used to capture this response. However, existing solvers provide only the response to a prescribed excitation and do not directly reveal the intrinsic resonances of the structure. This work extends the characteristic mode analysis to plasmonic nanostructures to enable excitation-independent modal analysis of their resonant behavior. For simple metals, the coupled hydrodynamic and volume integral equations are reduced to a single hydrodynamic volume integral equation in terms of the induced current. The equation is discretized and cast as a generalized
eigenvalue problem within the characteristic mode analysis framework, whose solution yields the characteristic mode currents and modal significance curves of the structure. The proposed framework is validated through three metallic nanostructures: a nanosphere, a nanorod, and a nanodimer. The results show that the method identifies the intrinsic resonances of each structure, including resonances not excited by a given source and additional resonances arising from the nonlocal response, which are absent in local models. The proposed framework provides physical insight into the modal mechanisms of plasmonic nanostructures and serves as a practical tool for their analysis and design.
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All authors Meruyert Khamitova, Ran Zhao, Doolos Aibek Uulu, Sebastian Celis Sierra, Hakan Bagci
Optics · Cross-listed from quant-ph
Field-Widened Multimode Interferometer with Long Time-Bin Delay Using a Multi-Pass Herriott Cell
Ramy Tannous, Stéphane Vinet, Kaylee Sherk et al. (+2 more)
Interference of optical signals in free-space channels requires optical receivers to support many spatial modes due to atmospheric
turbulence, typically necessitating adaptive optics systems. Field-widened interferometers offer a passive alternative, making them particularly attractive for time-bin encoded signals with delays on the order of one nanosecond. Here, we demonstrate a field-widened, multimode interferometer design that achieves a high interference visibility for spatially multimode beams with large time bin separations. The interference of the multimode beams is enabled using a multi-pass Herriott
cell that enables a very long path separation with a small form-factor. The design is tested using both numerical ray-tracing simulations and proof-of-principle demonstrations. We create a prototype interferometer with a path length difference of 12ns and determine that it maintains a high interference visibility with a large field-of-view of $0.4^{\circ}$.
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All authors Ramy Tannous, Stéphane Vinet, Kaylee Sherk, Kimia Mohammadi, Thomas Jennewein
Optics
Spectrally smooth broadband response via autocorrelation-constrained inverse design
Johannes Gedeon, Rasmus Ellebæk Christiansen and Ole Sigmund
Time-domain inverse design in photonics is known to be suitable for maximizing the efficiency of optical devices over broad frequency ranges. Objectives commonly used in this context include time-integrated field quantities derived from Poynting's
theorem, such as energy, flux, or dissipated power, which can be directly linked to integrated frequency-domain responses via Parseval's
theorem. While computationally efficient, these objectives measure only the total response over the targeted bandwidth and, as we demonstrate, are insufficient to capture undesired in-band ripple, narrow spectral features, or sidelobes. We overcome this limitation by introducing a time-domain metric quantifying such spectral variations based on the weighted long-lag autocorrelation energy of the optical response. We incorporate this metric into an FDTD-based
topology-optimization framework and demonstrate its beneficial effect on the example of inverse designing one-dimensional dielectric Bragg mirrors via the time-domain adjoint method.
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Optics
Geometric Parametric Instability in Nonlinear Multipass Cells
Chao Mei, Junhong Yang, Tao Sun et al. (+5 more)
Geometric parametric instability (GPI) is the resonant growth of discrete spectral sidebands enabled by longitudinally periodic multimode
evolution and has been studied primarily in graded-index fibers. Here we show theoretically and numerically that GPI can occur in gas-filled nonlinear multipass
cells (MPCs). By mapping a mode-matched MPC onto an equivalent waveguide, we derive a Floquet quasi-phase-matching condition governed by the single-pass Gouy-phase imbalance of the signal–idler pair relative to the pump pair. The theory predicts the small-signal gain and bandwidth. A pump-depleted coupled-mode model (CMM) further relates the maximum converted fraction to the residual phase mismatch. The CMM predicts multiple geometrically tunable sideband pairs associated with different radial indices and Floquet orders. For argon at $5$~bar, varying the cavity geometry shifts the sideband detuning from approximately $96$ to $46$~THz when the $p_{\mathrm{s}}=1$, $h=0$ branch is considered. A truncated multimode generalized nonlinear Schrödinger equation (MMGNLSE) model is used for numerical simulations with a semiclassical
stochastic seed corresponding to one
photon per spectral mode. The MMGNLSE simulations reproduce the predicted sideband frequencies and reveal pump depletion and competition among the retained radial channels. GPI in MPCs may therefore limit spatial beam quality in nonlinear pulse compression while providing a tunable mechanism for broadband multicolor generation.
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All authors Chao Mei, Junhong Yang, Tao Sun, Qian Gao, Jinhui Yuan, Jintao Fan, Peilong Yang, Günter Steinmeyer
Optics
Inverse-Designed High-Q/V Silicon Nitride Photonic Crystal Cavities for Second- and Third-Harmonic Generation
M. Takiguchi, P. Heidt, X. Z. Lim et al. (+7 more)
SiN photonic
crystal (PhC) cavities are promising platforms for nonlinear and
quantum photonics because of their wide transparency window, CMOS compatibility, and negligible two-
photon absorption. However, realizing high-Q/V cavities remains challenging because of the relatively low refractive index of SiN. Here, we employ inverse design to optimize a two-dimensional SiN PhC cavity and experimentally demonstrate a quality factor of approximately 80,000, the highest reported for a near-stoichiometric SiN 2D PhC cavity. Furthermore, both second- and third-harmonic generation are observed from the same cavity, providing experimental evidence of strong optical confinement and large Q/V. Our results establish inverse-designed SiN PhC cavities as a promising platform for nonlinear photonics and future heterogeneous integrated photonic devices.
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All authors M. Takiguchi, P. Heidt, X. Z. Lim, J. Zöllner, S. Yanagimoto, K. Nakayama, T. Aihara, M. Ono, H. Sumikura, M. Notomi
Optics · Cross-listed from quant-ph
Heterogeneously Integrated Squeezed-Light Generation and Detection on a Single Photonic Chip
Haoran Chen, Benjamin Westcott, Fatemehsadat Tabatabaei et al. (+10 more)
Squeezed light underpins
quantum-enhanced sensing and continuous-variable
quantum information processing, and integrated photonics offers a route to producing it at scale. Universal to these applications are squeezed-light generation and measurement. Importantly,
quantum measurements serve not only as readout but also as active operations in
quantum-state
evolution. However, integrating squeezed-light generation and photodetection on the same photonic chip has remained challenging because they impose fundamentally conflicting material requirements: low optical loss to preserve
quantum correlations, but efficient
photon absorption for photodetection. Here, we demonstrate squeezed-light generation, routing, and balanced homodyne detection integrated on a single photonic chip through heterogeneous integration. A two-mode squeezed
quantum microcomb comprising 34
quantum modes is measured with approximately 3 dB squeezing. Our work establishes a scalable architecture for fully integrated squeezed-light
quantum photonic systems, unifying
quantum-state generation, processing, and detection on a single chip.
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All authors Haoran Chen, Benjamin Westcott, Fatemehsadat Tabatabaei, Xiangwen Guo, Shuman Sun, Zijiao Yang, Gedalia Y. Koehler, Beichen Wang, Shadrach Sarpong, Steven Bowers, Olivier Pfister, Andreas Beling, Xu Yi
Optics
Ultrafast Tracking of the Spallation Layer in Bulk Gold, Aluminum, and Steel
Nicolas Thomae, Julian Vollmann, Julian Freundel et al. (+3 more)
Extreme manufacturing with ultrashort-pulse (USP)
lasers at the physical limit of precision and efficiency requires understanding ablation dynamics on the picosecond-to-nanosecond timescale. Pump-probe reflectometry (PPR) provides direct access to photomechanical spallation through Newton ring (NR) interference, but this signature vanishes when the spallation layer becomes optically opaque or the ablated material strongly attenuates the probe. Here, we combine PPR with phase-sensitive interferometric pump-probe (PPI) measurements to track the spallation layer in bulk steel, aluminum, and gold. PPI resolves the propagating layer even when the reflected probe signal is suppressed by >95%. Joint PPR/PPI analysis with transfer-
matrix modelling (TMM) yields spallation layer thickness, vapor layer absorption, and the layer disintegration times. These quantities are key determinants of the energy coupling of subsequent pulses in GHz burst processing.
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All authors Nicolas Thomae, Julian Vollmann, Julian Freundel, Maximilian Spellauge, David Redka, Heinz P. Huber
Optics
Micro- and nanoscale focusing across the XUV range of the ASTRID2 light source with a capillary optic
Alfred J. H. Jones, Zhihao Jiang, Asger Petersen et al. (+5 more)
Focusing of synchrotron light across extreme ultraviolet (XUV) and soft X-ray regimes is increasingly desired for photoemission-based techniques where reduced beam width gives access to smaller samples such as microscopic single
crystals and functioning two-dimensional (2D)
heterostructures and devices. Many existing focusing methods, however, are not able to take full advantage of the synchrotron beam due to limited
photon energy range or low transmission. Modern capillary optics have enabled achromatic, high transmission focusing of XUV and X-ray light. Here, we present a detailed characterisation of such an achromatic capillary optic installed at the AU-SGM4 beamline for spatial- and angle-resolved photoemission spectroscopy (ARPES) experiments at the ASTRID2 light source. The transmission of the capillary as a function of
photon energy is given, and the dependence of the beam width, position, and transmission are measured against the source size. Analysis of the far-field image of the beam allows for slope errors on the inner surface of the capillary to be overcome by selectively aperturing the beam, resulting in a minimum beam width of 900 nm measured in a photoemission geometry.
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All authors Alfred J. H. Jones, Zhihao Jiang, Asger Petersen, Søren V. Hoffmann, Nykola C. Jones, Philip Hofmann, Jill A. Miwa, Søren Ulstrup
Optics · Cross-listed from physics.ins-det
Scan-Coil Delay Causes Anisotropic Signal Loss in Fast 4D-STEM
Vishal Kumar, Andreas Jehle, Tizian Lorenzen et al. (+4 more)
Fast pixelated detectors are driving 4D-STEM toward microsecond dwell times, a regime in which the finite response of the scan deflection coils becomes comparable to the dwell time itself. Using direct probe imaging and sub-frame diffraction analysis, we document a significant intra-dwell scan-coil delay that systematically smears the recorded signal anisotropically along the fast scan direction, with a settling timescale of several tens of microseconds. We present a phase-correlation-based sub-frame
alignment procedure that measures and corrects this smearing, and we assess its impact on focused and defocused 4D-STEM reconstructions over a range of scan step sizes. The correction restores signal across a broad range of spatial frequencies, with the largest gains at the large step sizes required for low-dose biological imaging. Because it operates on existing data with no modification to the microscope, the method offers a practical route to recovering signal that would otherwise be lost to scan-coil delay.
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All authors Vishal Kumar, Andreas Jehle, Tizian Lorenzen, Julika Radecke, Knut Müller-Caspary, Massimo Kube, Henning Stahlberg
Optics · Cross-listed from cond-mat.dis-nn
Graph-theoretic design of lasing networks for physical vision
Paul Obernolte, Jakub Dranczewski, Yixiu Yin et al. (+10 more)
Physical neural networks perform learning through the intrinsic nonlinear dynamics of matter. Optimising their design presents a considerable challenge: complex many-body physics can provide powerful computation, but are expensive to simulate and large experimental optimisation runs are impractical to fabricate. Hence, the high-dimensional space of possible network
topologies cannot be effectively directly searched. Here, we show that this search can be efficiently performed in an abstract graph space that is vastly cheaper to explore. Using random lasing networks – composed of interconnected nanoscale waveguides and hosting strongly coupled lasing modes – as an exemplar physical
vision system, we establish a quantitative three-layer link: simple graph-theoretic metrics predict the nonlinear lasing physics, which in turn predicts
vision performance. After validating this relationship using physical simulations, we exploit it to drive an evolutionary
algorithm using graph metrics, producing network
topologies that outperform random designs at a fraction of the computational cost (3000$\times$ speed-up compared to physical simulation). On simulated image-classification tasks, graph-optimised networks substantially improve classification accuracy. As our framework operates on network
topology rather than substrate-specific physics, we anticipate it can transfer to other network-based physical learning systems, providing an efficient route for the directed design and optimisation of complex, strongly-interacting physical neural networks.
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All authors Paul Obernolte, Jakub Dranczewski, Yixiu Yin, Tobias Farchy, Wai Kit Ng, Tobias Simonsen, Elias Großhauser, Alexis Arnaudon, Robert L. Peach, Mauricio Barahona, Riccardo Sapienza, Jack C. Gartside, T. V. Raziman