arXiv subjects

Chen-Ting Liao

Publications and source records attributed to Chen-Ting Liao.

16 recordsLinked to original sources

arXiv2026

Attosecond Control of Squeezed Light

Squeezed light is a key resource in quantum metrology and quantum information science. It is primarily generated through nonlinear optical interactions, where the degree of squeezing is set by the nonlinearity of the medium. Here, we modulate the third-order nonlinear response of a dielectric with strong ultrafast laser fields to control squeezed light generation on attosecond time scales. By tuning a sub-cycle phase delay between the input femtosecond pulses, we switch the generated light between amplitude-squeezed and phase-squeezed states. We measure the quantum noise using a frequency-resolved balanced homodyne detection scheme that extracts field quadratures in many frequency modes simultaneously. From these measurements we obtain the complete coherency matrix containing quadrature correlations across the frequency modes of the pulse. These results enable quantum light sources with sub-cycle control of squeezing and open a route to transduction of dynamical quantum correlations in matter to quantum correlations in electric fields.

quant-ph↗

arXiv2026

Arithmetic with spatiotemporal optical vortex of integer and fractional topological charges

Spatiotemporal optical vortices carry transverse orbital angular momentum (t-OAM), which give rise to spatiotemporal topological charge (ST-TC). To unleash the full potential of t-OAM in expanding the capacity of communication and computing, we demonstrate the first optical information-processing pipeline capable of performing addition and subtraction on ST-TC values, regardless of whether they are integer or fractional. Additionally, we established a readout method for those mathematical operations through imaging spectral analysis, providing a robust optical basis toward arithmetic operations and verification. These new capabilities mark crucial advancements toward full arithmetic operations on the ST-TC of light for bosonic state computation and information processing.

physics.optics↗

arXiv2026

Wideband Balanced Photodetectors for Classical and Quantum Light Detection from Optical, EUV, to X-rays

The rapid development of coherent short-wavelength light sources in the extreme ultraviolet (EUV) and soft X-ray (SXR) regimes has created a growing need for advanced optoelectronic detection capabilities, particularly for quantum-noise-limited measurements, microelectronics and semiconductor metrology, and emerging quantum information applications. However, extending balanced photodetection to these wavelength regimes is severely hindered by a fundamental bandwidth-noise trade-off imposed by the exceptionally large junction capacitance of EUV-SXR silicon photodiodes. Here, we report a novel wideband photoreceiver architecture that overcomes this bottleneck via a bootstrapped transimpedance amplifier design. By leveraging a low-noise junction field-effect transistor interface, we effectively isolate the photodiode capacitance and suppress the apparent input capacitance seen by the core amplifier. Combined with active compensation of parasitic feedback reactance, this architecture mitigates the conventional trade-off between detector active area and signal bandwidth. Experimentally, we achieved a system-level input-referred noise floor of 13 $fA/\sqrt{Hz}$, closely approaching theoretical thermal limits. Furthermore, we achieved a six-fold extension in signal-to-noise limited bandwidth and, through the implementation of a novel grounded field plate, demonstrated a common-mode rejection ratio (CMRR) exceeding 30 dB up to 100 kHz. This highly scalable, silicon-based architecture effectively bridges the short-wavelength detection gap, establishing a robust experimental platform for next-generation quantum-noise-limited and quantum-enhanced X-ray measurement, as well as ultra-sensitive inspection and metrology applications in high-numerical-aperture EUV lithography.

physics.ins-det↗

arXiv2026

Roadmap on Attosecond Science

Twenty-five years have passed since the first experimental demonstration of attosecond pulses, marking the advent of our ability to resolve and control electron motion in real time. What began as a technological breakthrough - generating the shortest flashes ever produced - has evolved into a powerful approach for probing and steering electronic dynamics in atoms, molecules, and solids. This roadmap, authored by leading experts in the field, surveys the recent rapid progress in the generation and characterization of attosecond pulses, emerging attosecond measurement and control techniques, and their expanding range of applications. It reviews current and future developments in attosecond light sources, including novel laser technologies, waveform synthesizers, new schemes for high-order harmonic generation, attosecond pulse generation at free-electron lasers, and structured light. Advances in attosecond measurement methodologies are also discussed, encompassing all-attosecond pump-probe spectroscopy, attosecond four-wave mixing, attosecond microscopy, spectroscopy with light transients, and attosecond interferometry. Furthermore, the roadmap addresses applications of attosecond spectroscopy to reveal electron dynamics in molecules and condensed matter systems from both theoretical and experimental perspectives, and highlights emerging directions at the interface with quantum optics and quantum entanglement. Overall, this work aims to serve as a comprehensive resource for navigating the evolving landscape of attosecond science.

physics.optics↗

arXiv2025

Transverse orbital angular momentum and polarization entangled spatiotemporal structured light

Intra-system entanglement occurs between non-separable modes within the same system. For optical systems, the various degrees of freedom of light represent different modes, and the potential use of light to create higher dimensional classical entangle states offers a promising potential to drive new technological developments. In this work, we present experimental results demonstrating the orthogonality between transverse orbital angular momentum (t-OAM) of different spatiotemporal topological charges, a previously unverified property of t-OAM. Based on those results, we developed methods to create and characterize a novel family of t-OAM and polarization entangled spatiotemporal structured light. We further provide theoretical analysis to support our study of the entanglement between those modes. By demonstrating the feasibility of leveraging t-OAM as a new family of modes for classical entanglement, our work represents a new advancement towards higher dimensional classical entanglement strategies.

quant-ph↗

arXiv2024

Extreme-ultraviolet spatiotemporal vortices via high harmonic generation

Spatiotemporal optical vortices (STOV) are space-time structured light pulses with a unique topology that couples spatial and temporal domains and carry transverse orbital angular momentum (OAM). Up to now, their generation has been limited to the visible and infrared regions of the spectrum. During the last decade, it was shown that through the process of high-order harmonic generation (HHG) it is possible to up-convert spatial optical vortices that carry longitudinal OAM from the near-infrared into the extreme-ultraviolet (EUV), thereby producing vortices with distinct femtosecond and attosecond structure. In this work we demonstrate theoretically and experimentally the generation of EUV spatiotemporal and spatiospectral vortices using near infrared STOV driving laser pulses. We use analytical expressions for focused STOVs to perform macroscopic calculations of HHG that are directly compared to the experimental results. As STOV beams are not eigenmodes of propagation, we characterize the highly-charged EUV STOVs both in the near and far fields, to show that they represent conjugated spatiotemporal and spatiospectral vortex pairs. Our work provides high-frequency light beams topologically coupled at the nanometer/attosecond scales domains with transverse OAM, that could be suitable to explore electronic dynamics in magnetic materials, chiral media, and nanostructures.

physics.optics↗

arXiv2024

Non-Destructive, High-Resolution, Chemically Specific, 3D Nanostructure Characterization using Phase-Sensitive EUV Imaging Reflectometry

Next-generation nano and quantum devices have increasingly complex 3D structure. As the dimensions of these devices shrink to the nanoscale, their performance is often governed by interface quality or precise chemical or dopant composition. Here we present the first phase-sensitive extreme ultraviolet imaging reflectometer. It combines the excellent phase stability of coherent high-harmonic sources, the unique chemical- and phase-sensitivity of extreme ultraviolet reflectometry, and state-of-the-art ptychography imaging algorithms. This tabletop microscope can non-destructively probe surface topography, layer thicknesses, and interface quality, as well as dopant concentrations and profiles. High-fidelity imaging was achieved by implementing variable-angle ptychographic imaging, by using total variation regularization to mitigate noise and artifacts in the reconstructed image, and by using a high-brightness, high-harmonic source with excellent intensity and wavefront stability. We validate our measurements through multiscale, multimodal imaging to show that this technique has unique advantages compared with other techniques based on electron and scanning-probe microscopies.

physics.optics↗

arXiv2024

Visualizing Magnetic Order in Self-Assembly of Superparamagnetic Nanoparticles

We use soft x-ray vector-ptychographic tomography to determine the three-dimensional magnetization field in superparamagnetic nanoparticles self-assembled at the liquid-liquid interface and reveal the magnetic order induced by layered structure. The spins in individual nanoparticles become more aligned with increasing number of layers, resulting in a larger net magnetization. Our experimental results show a magnetic short-range order in the monolayer due to the proliferation of thermally induced magnetic vortices and a magnetic long-range order in the bilayer and trilayer, stemming from the strengthened dipolar interactions that effectively suppress thermal fluctuations. We also observe a screening effect of magnetic vortices and the attractive interaction between the magnetic vortices with opposite topological charges. Our work demonstrates the crucial role of layered structure in shaping the magnetization of nanoparticle assemblies, providing new opportunities to modulate these properties through strategic layer engineering.

cond-mat.mes-hall↗

arXiv2022

Roadmap on spatiotemporal light fields

Spatiotemporal sculpturing of light pulse with ultimately sophisticated structures represents the holy grail of the human everlasting pursue of ultrafast information transmission and processing as well as ultra-intense energy concentration and extraction. It also holds the key to unlock new extraordinary fundamental physical effects. Traditionally, spatiotemporal light pulses are always treated as spatiotemporally separable wave packet as solution of the Maxwell's equations. In the past decade, however, more generalized forms of spatiotemporally nonseparable solution started to emerge with growing importance for their striking physical effects. This roadmap intends to highlight the recent advances in the creation and control of increasingly complex spatiotemporally sculptured pulses, from spatiotemporally separable to complex nonseparable states, with diverse geometric and topological structures, presenting a bird's eye viewpoint on the zoology of spatiotemporal light fields and the outlook of future trends and open challenges.

physics.optics↗

arXiv2022

Single-frame characterization of ultrafast pulses with spatiotemporal orbital angular momentum

Light carrying spatiotemporal orbital angular momentum (ST-OAM) makes possible new types of optical vortices arising from transverse OAM. ST-OAM pulses exhibit novel properties during propagation, transmission, refraction, diffraction, and nonlinear conversion, attracting growing experimental and theoretical interest and studies. However, one major challenge is the lack of a simple and straightforward method for characterizing ultrafast ST-OAM pulses. Using spatially resolved spectral interferometry, we demonstrate a simple, stationary, single-frame method to quantitatively characterize ultrashort light pulses carrying ST-OAM. Using our method, the presence of an ST-OAM pulse, including its main characteristics such as topological charge numbers and OAM helicity, can be identified easily from the unique and unambiguous features directly seen on the raw data--without any need for a full analysis of the data. After processing and reconstructions, other exquisite features, including pulse dispersion and beam divergence, can also be fully characterized. Our fast characterization method allows high-throughput and quick feedback during the generation and optical alignment processes of ST-OAM pulses. It is straightforward to extend our method to single-shot measurement by using a high-speed camera that matches the pulse repetition rate. This new method can help advance the field of spatially and temporally structured light and its applications in advanced metrologies.

physics.optics↗

arXiv2021

Second-harmonic generation and the conservation of spatiotemporal orbital angular momentum of light

Light with spatiotemporal orbital angular momentum (ST-OAM) is a recently discovered type of structured and localized electromagnetic field. This field carries characteristic space-time spiral phase structure and transverse intrinsic OAM. In this work, we present the generation and characterization of the second-harmonic of ST-OAM pulses. We uncovered the conservation of transverse OAM in a second-harmonic generation process, where the space-time topological charge of the fundamental field is doubled along with the optical frequency. Our experiment thus suggests a general ST-OAM nonlinear scaling rule - analogous to that in conventional OAM of light. Furthermore, we observe that the topology of a second-harmonic ST-OAM pulse can be modified by complex spatiotemporal astigmatism, giving rise to multiple phase singularities separated in space and time. Our study opens a new route for nonlinear conversion and scaling of light carrying ST-OAM with the potential for driving other secondary ST-OAM sources of electromagnetic fields and beyond.

physics.optics↗

arXiv2021

Direct observation of 3D topological spin textures and their interactions using soft x-ray vector ptychography

Magnetic topological defects are energetically stable spin configurations characterized by symmetry breaking. Vortices and skyrmions are two well-known examples of 2D spin textures that have been actively studied for both fundamental interest and practical applications. However, experimental evidence of the 3D spin textures has been largely indirect or qualitative to date, due to the difficulty of quantitively characterizing them within nanoscale volumes. Here, we develop soft x-ray vector ptychography to quantitatively image the 3D magnetization vector field in a frustrated superlattice with 10 nm spatial resolution. By applying homotopy theory to the experimental data, we quantify the topological charge of hedgehogs and anti-hedgehogs as emergent magnetic monopoles and probe their interactions inside the frustrated superlattice. We also directly observe virtual hedgehogs and anti-hedgehogs created by magnetically inert voids. We expect that this new quantitative imaging method will open the door to study 3D topological spin textures in a broad class of magnetic materials. Our work also demonstrates that magnetically frustrated superlattices could be used as a new platform to investigate hedgehog interactions and dynamics and to exploit optimized geometries for information storage and transport applications.

cond-mat.str-el↗

arXiv2019

Light with a self-torque: extreme-ultraviolet beams with time-varying orbital angular momentum

Twisted light fields carrying orbital angular momentum (OAM) provide powerful capabilities for applications in optical communications, microscopy, quantum optics and microparticle rotation. Here we introduce and experimentally validate a new class of light beams, whose unique property is associated with a temporal OAM variation along a pulse: the self-torque of light. Self-torque is a phenomenon that can arise from matter-field interactions in electrodynamics and general relativity, but to date, there has been no optical analog. In particular, the self-torque of light is an inherent property, which is distinguished from the mechanical torque exerted by OAM beams when interacting with physical systems. We demonstrate that self-torqued beams in the extreme-ultraviolet (EUV) naturally arise as a necessary consequence of angular momentum conservation in non-perturbative high-order harmonic generation when driven by time-delayed pulses with different OAM. In addition, the time-dependent OAM naturally induces an azimuthal frequency chirp, which provides a signature for monitoring the self-torque of high-harmonic EUV beams. Such self-torqued EUV beams can serve as unique tools for imaging magnetic and topological excitations, for launching selective excitation of quantum matter, and for manipulating molecules and nanostructures on unprecedented time and length scales.

physics.optics↗

arXiv2017

Probing autoionizing states of molecular oxygen with XUV transient absorption: Electronic symmetry dependent lineshapes and laser induced modification

The dynamics of autoionizing Rydberg states of oxygen are studied using attosecond transient absorption technique, where extreme ultraviolet (XUV) initiates molecular polarization and near infrared (NIR) pulse perturbs its evolution. Transient absorption spectra show positive optical density (OD) change in the case of $nsσ_g$ and $ndπ_g$ autoionizing states of oxygen and negative OD change for $ndσ_g$ states. Multiconfiguration time-dependent Hartree-Fock (MCTDHF) calculation are used to simulate the transient absorption spectra and their results agree with experimental observations. The time evolution of superexcited states is probed in electronically and vibrationally resolved fashion and we observe the dependence of decay lifetimes on effective quantum number of the Rydberg series. We model the effect of near-infrared (NIR) perturbation on molecular polarization and find that the laser induced phase shift model agrees with the experimental and MCTDHF results, while the laser induced attenuation model does not. We relate the electron state symmetry dependent sign of the OD change to the Fano parameters of the static absorption lineshapes.

physics.atom-ph↗

arXiv2016

Attosecond Transient Absorption in Dense Gases: Exploring the Interplay between Resonant Pulse Propagation and Laser-Induced Line Shape Control

We investigate the evolution of extreme ultraviolet (XUV) spectral lineshapes in an optically-thick helium gas under near-infrared (IR) perturbation. In our experimental and theoretical work, we systematically vary the IR intensity, time-delay, gas density and IR polarization parameters to study lineshape modifications induced by collective interactions, in a regime beyond the single atom response of a thin, dilute gas. In both experiment and theory, we find that specific features in the frequency-domain absorption profile, and their evolution with propagation distance, can be attributed to the interplay between resonant attosecond pulse propagation and IR induced phase shifts. Our calculations show that this interplay also manifests itself in the time domain, with the IR pulse influencing the reshaping of the XUV pulse propagating in the resonant medium.

physics.atom-ph↗

arXiv2015

Beyond the single-atom response in absorption lineshapes: Probing a dense, laser-dressed helium gas with attosecond pulse trains

We investigate the absorption line shapes of laser-dressed atoms beyond the single-atom response, by using extreme ultraviolet (XUV) attosecond pulse trains to probe an optically thick helium target under the influence of a strong infrared (IR) field. We study the interplay between the IR-induced phase shift of the microscopic time-dependent dipole moment and the resonant-propagation-induced reshaping of the macroscopic XUV pulse. Our experimental and theoretical results show that as the optical depth increases, this interplay leads initially to a broadening of the IR-modified line shape, and subsequently to the appearance of new, narrow features in the absorption line.

physics.atom-ph↗