This paper proposes a high-security probabilistic shaping 16-7QAM mapping method via constellation-level chaotic tagging. A novel, to the best of our knowledge, constellation-level chaotic tagging rule is devised that re...This paper proposes a high-security probabilistic shaping 16-7QAM mapping method via constellation-level chaotic tagging. A novel, to the best of our knowledge, constellation-level chaotic tagging rule is devised that re-maps the original 16 signal points, each encoded by 4 bits, onto predefined 3-bit modulation symbols. Simultaneously, a Lorenz chaotic system is employed to generate a chaotic sequence, from which a 2-bit tag corresponding to each 3-bit modulation symbol is extracted to form the constellation-level chaotic tag. Subsequently, each signal point is combined with a 2-bit tag generated by a Lorenz chaotic system to form the final output consisting of 7 signal points. Experimental validation over a seven-core fiber transmission system shows that, at a bit error rate of 3.8 × 10, the proposed probabilistic shaping 16-7QAM constellation achieves a 0.49 dB improvement in receiver sensitivity compared with conventional 16-QAM. Moreover, the encryption scheme has almost no impact on the transmission performance of the probabilistic shaping signal itself. Additionally, the key space of the scheme reaches 10, effectively ensuring physical layer security. The proposed method exhibits robust performance and strong security, enhancing both the transmission performance and security of the system.
We demonstrate, for the first time to the best of our knowledge, the implementation of Spatial Frequency Modulated Imaging (SPIFI) microscopy in the mid-infrared region using a Quantum Cascade Laser (QCL) source. Hypersp...We demonstrate, for the first time to the best of our knowledge, the implementation of Spatial Frequency Modulated Imaging (SPIFI) microscopy in the mid-infrared region using a Quantum Cascade Laser (QCL) source. Hyperspectral imaging in the mid-infrared (3-20 μm) enables chemically specific mapping and structural imaging based on molecular contrast, which is otherwise inaccessible in the visible or near-infrared region. But mid-infrared microscopes are often limited by slow raster scanning and costly detector arrays. Our approach uses spatial frequency-encoded structured illumination and a low-cost single-pixel mid-infrared detector to acquire hyperspectral images in transflection mode. The system-structured illumination single-pixel imaging system in the mid-infrared-provides a practical trade-off between speed and complexity, offering acquisition speeds comparable to selected QCL-based point-scanning implementations, while maintaining a simple, cost-effective optical design utilizing off-the-shelf components. We present a preliminary resolution measurement as well as absorption images of coronal sections of a mouse brain at both 6 and 7 μm, demonstrating chemically selective contrast and robust image formation suitable for future high-resolution and compressive implementations.
We introduce a compact operator-based technique that solves the paraxial wave equation (PWE) for a broad class of structured light fields. Using the spatial evolution operator to propagate two families of physically apod...We introduce a compact operator-based technique that solves the paraxial wave equation (PWE) for a broad class of structured light fields. Using the spatial evolution operator to propagate two families of physically apodized inputs, Gaussian-apodized Whittaker (WG) integrals and Gaussian-apodized Helmholtz (HG) fields, we derive closed-form expressions that retain the Gaussian width and therefore describe finite-energy beams. The method unifies and extends the HG families and readily generalizes to non-separable non-diffracting architectures. To physically validate our analytical expressions, we experiment on superposed Bessel-Gauss beams. The precise agreement between physical dynamics and theoretical predictions confirms that this operator approach yields exact, artifact-free phase and amplitude functions, demonstrating that it is a practical alternative to standard diffraction-integral treatments.
An ultra-broadband and compact mode converter based on a multimode interferometer (MMI) with a micro-slot embedded is demonstrated, where the micro-slot serves as a localized refractive-index perturbation in the MMI that...An ultra-broadband and compact mode converter based on a multimode interferometer (MMI) with a micro-slot embedded is demonstrated, where the micro-slot serves as a localized refractive-index perturbation in the MMI that precisely controls the phase evolution of lateral modes. The fabricated device is based on a fiber-compatible polymer platform with a 2700 µm MMI length and a 100 × 14 × 5 µm micro-slot. The fabricated device enables the efficient conversion between the E mode and the E mode with a mode conversion efficiency higher than 92% and modal crosstalk lower than -11 dB across the O band and the C + L band and beyond while maintaining large device fabrication tolerance. Our proposed mode converter offers a robust, CMOS-compatible, and high-performance solution for ultra-broadband mode manipulation and signal processing where high-order modes are required.
Ultrafast, high-precision roll-angle metrology is crucial for dynamic motion control yet remains challenging because roll is not directly accessible to conventional geometric optical methods. Here, we present a roll-angl...Ultrafast, high-precision roll-angle metrology is crucial for dynamic motion control yet remains challenging because roll is not directly accessible to conventional geometric optical methods. Here, we present a roll-angle measurement method based on a polarization-modulated optical frequency comb (PMOFC). By modulating the offset frequency, a sequence of femtosecond pulses with periodically varying polarization was generated. After passing through a birefringent target and a fixed-angle analyzer, the roll angle is retrieved from the corresponding intensity sequence. Experimental results demonstrate an absolute non-ambiguous range of 0°-90°, and a single-shot measurement time of ∼71 ns. At the worst-case angular position, the Allan deviation decreases below 20 after 3.93 μs of averaging. These results establish a practical route to high-rate absolute roll-angle measurement.
The practical viability of lead-free perovskites is often constrained by their instability and low photoluminescence quantum yield (PLQY). Here, we achieved a thermally stable perovskite with a PLQY of 90.5% on Te-doped...The practical viability of lead-free perovskites is often constrained by their instability and low photoluminescence quantum yield (PLQY). Here, we achieved a thermally stable perovskite with a PLQY of 90.5% on Te-doped CsZrCl material through ionic-liquids (ILs)-mediated crystal growth. Temperature-dependent PL spectroscopy reveals that ILs treatment raises the thermal activation energy up to 109.9 meV, attributed to ILs-induced retarded crystal growth, which enables effective defect passivation and suppression of defect-assisted electron-phonon coupling process. Femtosecond transient-absorption spectroscopy further reveals ultrafast cascaded energy transfer from CsZrCl host to singlet state of doped Te and subsequent intersystem crossing (ISC) to its triplet state, with kinetic analysis demonstrating that ILs treatment drastically accelerates the route by shortening the host-to-dopant transfer time from 149.0 to 31.0 ps and the ISC time from 2115.5 to 732.9 ps compared to that of the untreated sample. These results reveal that ILs-mediated defect passivation can promote the cascaded energy-transfer process, thereby boosting perovskite PLQY.
Triplet sensitization of semiconductor nanocrystals is important in photocatalysis and photodynamic therapy. However, current photosensitizers often contain toxic or precious metals, making the development of environment...Triplet sensitization of semiconductor nanocrystals is important in photocatalysis and photodynamic therapy. However, current photosensitizers often contain toxic or precious metals, making the development of environmentally benign nanocrystal-based systems challenging due to scarce suitable materials and insufficient understanding of excited-state transfer. Herein, we investigate triplet energy transfer from CuInS/ZnS nanorods to surface-anchored 9-anthracene carboxylic acid acceptors, with a rate constant of 1.02 × 10 s and 90% efficiency. Besides, the transferred spin-triplet states undergo triplet-triplet annihilation in the interfaced annihilator molecules of diphenyl anthracene, enabling photon upconversion with a threshold of 23.26 W/cm² and an efficiency of 6.8%. These findings highlight CuInS/ZnS nanorods as nontoxic triplet sensitizers and provide a viable strategy for sustainable upconversion optoelectronic devices.
Mirror array-based intelligent reflecting surfaces (mIRS) offer a promising solution to line-of-sight (LoS) blockage in optical camera communication (OCC). However, since the physical size of individual mIRS mirrors is s...Mirror array-based intelligent reflecting surfaces (mIRS) offer a promising solution to line-of-sight (LoS) blockage in optical camera communication (OCC). However, since the physical size of individual mIRS mirrors is smaller than the imaging field of view, reflected optical signals appear as discrete, fragmented stripe segments on the image sensor. These fragmented signals cannot be directly demodulated, constituting a primary challenge for mIRS-aided OCC. This Letter proposes a Geometric-Signal Reconstruction (GSR) scheme, which integrates an Overlapping Beam Alignment (OBA) algorithm for mIRS orientation configuration and a Correlation Sequence Stitching (CSS) algorithm for fragmented signal integration. We report the first, to the best of our knowledge, experimental implementation of an mIRS-aided OCC system. Experimental results verify that the proposed GSR scheme successfully restores blocked links with a bit error rate (BER) of 10 and significantly enhances physical layer security through spatial selectivity.
Accurate object localization is critical for robust autofocus in digital holography (DH). Here, we present a time-reversal (TR) symmetry-enabled autofocus strategy integrated with depth-dependent randomized sparse sampli...Accurate object localization is critical for robust autofocus in digital holography (DH). Here, we present a time-reversal (TR) symmetry-enabled autofocus strategy integrated with depth-dependent randomized sparse sampling. Our approach is grounded in the low-rank structure of the TR operator. This inherent property, arising from the dynamical constraints of the wave equation, provides a physical foundation for sparse sampling without compromising subspace separation. By using independent, uniformly distributed test point sets at each axial plane, the method effectively decorrelates sampling-induced clutter and acts as an approximately unbiased Monte Carlo estimator. This analytical, training-free solution preserves the inherent orthogonality of signal and noise subspaces, ensuring high-fidelity localization even at ultra-low sampling rates (e.g., 0.25). Simulations and experiments demonstrate that the proposed method achieves high-resolution autofocus with significant computational savings, paving the way for real-time dynamic autofocus in diverse sensing environments.
Eye tracking is pivotal for human-computer interaction, yet current wearable devices have constrained detection capability due to side-view camera configurations. While cameras integrated with optical waveguides provide...Eye tracking is pivotal for human-computer interaction, yet current wearable devices have constrained detection capability due to side-view camera configurations. While cameras integrated with optical waveguides provide transparent front-view imaging windows, they typically necessitate customized structures to form clear eye images directly. In this work, we propose an eye-tracking system with a non-customized diffractive augmented reality waveguide utilizing a computational imaging approach. By employing computational reconstruction to address optical distortions, our scheme eliminates the strict requirement for hardware-based point-to-point optical mapping. The imaging quality is validated through quantitative metrics and downstream gaze estimation tasks, demonstrating an experimental gaze angular resolution of 0.776 under the present fixed-distance eyeball-model setup. This approach enables the reuse of commercial display waveguides for sensing, offering a compact and cost-effective path for advanced AR system integration.
High-repetition-rate sub-optical-cycle synthesis based on two-color Yb lasers requires few-cycle pulses from both the fundamental wave (FW) and its second harmonic (SH). Yet generating few-cycle SH pulses remains challen...High-repetition-rate sub-optical-cycle synthesis based on two-color Yb lasers requires few-cycle pulses from both the fundamental wave (FW) and its second harmonic (SH). Yet generating few-cycle SH pulses remains challenging. Here, we demonstrate a 3.1 W few-cycle green source at 50 kHz using a strategy that first compresses the FW pulses, followed by frequency doubling and subsequent post-compression of the SH pulses in an argon-filled gas cell. The system derived pulses of 6.3 fs with 62-µJ pulse energy with 0.3% RMS power stability over 6 h, enabling strong-field electron dynamics control within sub-cycle regime and its applications at high signal-to-noise ratio.
We report on a high-average-power, high-energy cryogenic Ho:YLF picosecond chirped-pulse amplification system operating at 1 kHz repetition rate. High gain characteristics and excellent thermal management were well achie...We report on a high-average-power, high-energy cryogenic Ho:YLF picosecond chirped-pulse amplification system operating at 1 kHz repetition rate. High gain characteristics and excellent thermal management were well achieved by integrating cryogenic cooling with in-band pumping. A maximum compressed average power of 205 W at 1 kHz repetition rate with a pulse duration of 1.7 ps was delivered by the system. A high extraction efficiency of 41.2% and near-diffraction-limited beam quality (M = 1.14) were demonstrated.
Holographic steganography is considered a highly secure information transmission method that relies on active optical media to achieve multifunctionality. Transition metal oxides undergo reversible color changes during p...Holographic steganography is considered a highly secure information transmission method that relies on active optical media to achieve multifunctionality. Transition metal oxides undergo reversible color changes during photoelectrically driven cation migration, providing a platform for tunable holography. However, single-ion migration systems suffer from rapid attenuation of holographic fringe contrast under repeated electrical switching, leading to the loss of diffraction efficiency and hindering reliable information readout. In this Letter, we develop a WO/electrolyte/TiO optoelectronic memory based on Li-Ag dual-cation synergistic regulation. The excitation of near-ultraviolet coherent light not only constructs an initial hologram in the WO layer but also generates latent nucleation sites for Ag particles on the TiO surface. During subsequent electrical switching, the dual-cation device can either hide holograms by modulating the Li ions distribution or reproduce signals by selectively depositing Ag particles on the pre-defined latent sites. The device integrates the color-changing pathway of WO/Li with the silver electrodeposition of TiO/Ag, improving the diffraction efficiency and cycling durability. By programming specific voltage sequences, the holographic steganography based on spatiotemporal multiplexing is achieved. This work paves a bright path for high-density information security storage.
We propose a vibration detection scheme that directly utilizes integrated coherent receivers and leverages pilot symbols (PS) consistent with implementation agreements (IAs)-defined digital signal processing (DSP) frame....We propose a vibration detection scheme that directly utilizes integrated coherent receivers and leverages pilot symbols (PS) consistent with implementation agreements (IAs)-defined digital signal processing (DSP) frame. By applying a low-complexity sliding filter and an averaging operation to the phase tracked by the widely and commercially used PS-based carrier phase recovery algorithm, the external-cavity lasers (ECLs)-induced phase noise is effectively suppressed. Simulations demonstrated the accurate retrieval of vibrations across the frequency range of 10-40 kHz, with a linearity of =0.9998 and a sensitivity of 0.04 rad. Experimental validation in a 60-GBaud dual-polarization 16-quadrature amplitude modulation (DP-16QAM) system yielded a sensing signal-to-noise ratio (SSNR) of 23.9 dB for a ∼5.5-rad vibration at 60 kHz, achieving a sensitivity of 0.09 rad. This scheme offers a robust solution for integrated sensing in future intelligent optical networks.
We propose and study a new, to the best of our knowledge, periodic PT-Symmetric optical scheme consisting of two waveguides with alternating gain/loss sections. The structure exhibits multiple EPs and PT-Symmetric/Broken...We propose and study a new, to the best of our knowledge, periodic PT-Symmetric optical scheme consisting of two waveguides with alternating gain/loss sections. The structure exhibits multiple EPs and PT-Symmetric/Broken-symmetry regions, even for negligible gain/loss. The positions of these branches can be changed not only by the level of gain/loss but also by modifying the periodicity of the structure, thus allowing controllable dynamics and on-demand switching between symmetry phases.
Megahertz-rate optical coherence tomography (MHz-OCT) is an optical imaging technology that has attracted considerable attention in clinical practice. Its advantages, such as ultra-high speed, noninvasiveness, and high r...Megahertz-rate optical coherence tomography (MHz-OCT) is an optical imaging technology that has attracted considerable attention in clinical practice. Its advantages, such as ultra-high speed, noninvasiveness, and high resolution, endow it with broad application prospects in various clinical fields. However, MHz-OCT systems place high demands on the sampling rate and bandwidth of acquisition and data transmission systems, greatly increasing the system cost. Based on a high-speed k-linear swept laser with the acousto-optic deflector (AOD), this paper proposes a hardware-based down-sampling method. Sweeping a narrowband spectrum and utilizing the linear wavenumber characteristic of the laser enables an equivalent down-sampling of the original interference signal. Deep learning is employed to recover high-resolution images from the down-sampled signals. High-quality imaging results have been successfully achieved at a high sweep speed of 1 MHz while using acquisition and data transmission systems with lower bandwidth and sampling rate. The novel down-sampled OCT system proposed in this paper helps to reduce the cost of MHz-OCT systems in clinical settings and promotes their popularization and application.
How nonspherical raindrops scatter light and how their scattering deviates from spheroidal approximations remain poorly quantified owing to complex geometries and extreme size parameters (>10). Here, we extend the three-...How nonspherical raindrops scatter light and how their scattering deviates from spheroidal approximations remain poorly quantified owing to complex geometries and extreme size parameters (>10). Here, we extend the three-dimensional vectorial complex ray model (VCRM3D) to investigate light scattering by Beard-Chuang (BC) raindrops, the established equilibrium model for realistic falling drops. Validated against Lorenz-Mie theory and the multilevel fast multipole algorithm, our results characterize the light scattering signatures of BC raindrops and quantify their discrepancies from those of spheroids. Unlike the monotonic increase for spheroids, BC backscattering efficiency exhibits non-monotonic behavior governed by surface curvature, peaking at ≈4.2 mm before declining.
We study photonic meta-atoms, a unique class of composite solitary wave supported in nonlinear waveguides. We establish an analogy to one-dimensional soft-core atoms, allowing us to describe the complex dynamics via conc...We study photonic meta-atoms, a unique class of composite solitary wave supported in nonlinear waveguides. We establish an analogy to one-dimensional soft-core atoms, allowing us to describe the complex dynamics via concepts from atomic physics. Higher-order dispersive effects cause specific spectral resonances characteristic for the eigenspectrum of a meta-atom. We demonstrate that subtle changes in this level of spectrum cause frequency shifts of the resonances. These shifts consist of isotopic and isomeric contributions that can be distinguished in terms of a simple model. We further demonstrate a generic mechanism that causes a Zeeman-like splitting of resonance lines.
We demonstrate the generation of 20.2 W of continuous-wave, low-intensity noise, single-frequency light at 840 nm, obtained via sum-frequency mixing of two high-power infrared fiber laser systems in an MgO-doped periodic...We demonstrate the generation of 20.2 W of continuous-wave, low-intensity noise, single-frequency light at 840 nm, obtained via sum-frequency mixing of two high-power infrared fiber laser systems in an MgO-doped periodically poled lithium niobate (ppLN) crystal. Subsequent cavity-enhanced frequency doubling to 420 nm yields an output power of 15.2 W. Respective conversion efficiencies of 48% and 79% are achieved for the sum-frequency and second-harmonic stages, with good beam quality (M < 1.3), low intensity noise (<0.05% RMS [1 kHz-10 MHz]), and long-term continuous operation. Relative intensity noise and frequency noise of the generated signals are experimentally characterized.
A high-efficiency ultraviolet (UV) optical wireless communication link is proposed and demonstrated between unmanned aerial vehicles (UAVs) employing a novel azimuthally omnidirectional optical antenna based on an annula...A high-efficiency ultraviolet (UV) optical wireless communication link is proposed and demonstrated between unmanned aerial vehicles (UAVs) employing a novel azimuthally omnidirectional optical antenna based on an annular compound parabolic concentrator (ACPC). The receiving antenna offers a 114° field of view (FOV), covering polar angles from 10° to 124°, while achieving a maximum omnidirectional gain of 21.6 dB at a distance of 9 m. With a data transmission rate of 9.6 kbps, an outdoor transmission of live images between two in-flight UAVs successfully validates the link performance.