Single-pixel imaging shows great potential for parallel perception of multiple objects. However, existing methods face information security risks and lack effective user access control. In this Letter, we propose an acce...Single-pixel imaging shows great potential for parallel perception of multiple objects. However, existing methods face information security risks and lack effective user access control. In this Letter, we propose an access-controlled imaging method based on structured single-pixel illumination. The system introduces phase modulation equivalently into the measurement matrix by applying key-controlled spatial displacements to the projection patterns, without requiring additional modulation devices. Meanwhile, an optical projection multiplexing architecture enables linear mixing of multi-object information. During reconstruction, the template decomposition vectors serve as user-specific keys for selective imaging. Experimental results demonstrate high-quality parallel imaging with integrated physical-layer access control, providing a promising solution for secure communication and hierarchical surveillance.
Without requiring parity-time () symmetric optical potential, we explore a memory-based temporal synthesis mechanism for non-Hermitian photon control using electromagnetically induced transparency (EIT). In an -type EIT...Without requiring parity-time () symmetric optical potential, we explore a memory-based temporal synthesis mechanism for non-Hermitian photon control using electromagnetically induced transparency (EIT). In an -type EIT system, a dynamic double-lattice configuration can be scheduled to impose spatially shifted periodic cross-phase modulation and cross-amplitude modulation on the spin excitation via giant Kerr nonlinearity. Passive -symmetric imprinting can thus be temporally synthesized in coherent optical memory at low light levels, whereby the phase transition of the system is flexibly engineered in the time domain. Using the multiple exposure technique, the -symmetric moiré imprinting could be further synthesized to control several equal-intensity diffraction peaks. Our work holds promise for time-dependent non-Hermitian manipulation of the retrieved light.
In traditional spin-exchange relaxation-free (SERF) gyroscopes, open-loop detection leaves the scale factor vulnerable to fluctuations in probe laser intensity and environmental temperature. To address this, an external-...In traditional spin-exchange relaxation-free (SERF) gyroscopes, open-loop detection leaves the scale factor vulnerable to fluctuations in probe laser intensity and environmental temperature. To address this, an external-modulator-free closed-loop atomic spin gyroscope (ASG) is demonstrated using direct probe laser injection current modulation. A magnetic feedback loop maintains the total optical rotation at a zero point, decoupling the inertial signal from intensity and optical depth variations. Experimental results demonstrate a closed-loop rotation sensitivity of 2.8×10°/s/Hz at 1 Hz. Compared to open-loop measurements under identical conditions (1×10/s/Hz), low-frequency noise is significantly suppressed. By eliminating bulky external modulators and effectively suppressing low-frequency noise, this design offers a highly competitive architecture for miniaturized atomic inertial sensors.
Lindner J, Gronenborn S, Torrelli V
… +10 more, Pusch T, Reichel J, Herper M, Mönch H, Gullino A, D'Alessandro M, Debernardi P, Maassdorf A, Weyers M, Reitzenstein S
We report on 795 nm vertical-cavity surface-emitting lasers (VCSELs) that achieve record-high (10.9 ± 0.4) mW single-mode output power with linear polarization. In our VCSEL concept based on a strongly elongated oxide ap...We report on 795 nm vertical-cavity surface-emitting lasers (VCSELs) that achieve record-high (10.9 ± 0.4) mW single-mode output power with linear polarization. In our VCSEL concept based on a strongly elongated oxide aperture, a high-order transverse mode is stabilized via distributed grating reliefs (GR) that are positioned on the output facet. To align the phases of the waves from adjacent emission sites, an alternating scheme of GR and dielectric phase-shifting pillars (PP) is introduced, which causes a local phase-shift and transforms the far-field intensity onto the optical axis. This approach is guided by simulations and is experimentally demonstrated. The presented concept for high-order mode stabilization offers a promising route to substantially enhance the single-mode output power of VCSELs while preserving linear polarization and on-axis emission, which is attractive for a broad range of applications, including, for instance, quantum technology and biomedical applications.
Fe ion as an activator with eco-friendly nature has an exceptional ability to achieve efficient near-infrared (NIR) luminescence within 700-1100 nm range. However, its emission in 820-880 nm region is rarely reported, li...Fe ion as an activator with eco-friendly nature has an exceptional ability to achieve efficient near-infrared (NIR) luminescence within 700-1100 nm range. However, its emission in 820-880 nm region is rarely reported, limiting the versatile applications of Fe-activated materials. In this Letter, a double-perovskite KLaMgTeO:Fe phosphor was developed, which exhibits an emission peak centered at 851 nm, accompanied by a high photoluminescence quantum yield (PLQY) of up to 82%. Furthermore, the fabricated NIR light source demonstrated excellent performance in night-vision, imaging, and non-destructive testing applications. Thus, this study offers an efficient NIR material that covers a previously underexplored emission window, expanding the application landscape of Fe-doped materials.
We report a Ge MSM photodetector decorated with Al nanoparticles (NPs) via magnetron sputtering. Exploiting the low Al-Ge solid solubility, Al atoms spontaneously segregate and self-assemble into high-density surface NPs...We report a Ge MSM photodetector decorated with Al nanoparticles (NPs) via magnetron sputtering. Exploiting the low Al-Ge solid solubility, Al atoms spontaneously segregate and self-assemble into high-density surface NPs. The resulting localized surface plasmon resonance enhances visible-light absorption through strong scattering and local electric fields. At 405 nm, the device exhibits a ~9-fold enhancement in responsivity, reaching 0.67 A/W, with a detectivity of 1.66 × 10⁹ Jones and rapid response times (rise/fall: 0.37/0.54 μs). This work demonstrates efficient dual-band detection, providing a promising low-cost route for dual-band optoelectronic integration.
This paper presents a stepped AlN/SiO/Au cavity structure based on the phonon material AlN, achieving topological phase transitions and the excitation of spin-locked topological edge states. The reflective topological ch...This paper presents a stepped AlN/SiO/Au cavity structure based on the phonon material AlN, achieving topological phase transitions and the excitation of spin-locked topological edge states. The reflective topological characteristics of the cavity are described by the winding number, derived from the encirclement behavior of the reflection coefficient in the complex plane. By adjusting the thickness of the AlN absorption layer, the cavity transitions between overdamped and underdamped states, realizing a topological transition from trivial to non-trivial reflection surfaces. Finite element method (FEM) simulations demonstrate that highly localized topological edge states emerge at the interface of the stepped structure where the winding number jumps, exhibiting pronounced spin-momentum locking. Fourier transform analysis further confirms consistency between real-space field distributions and reciprocal-space spectra. This work provides a strategy for spatial control of infrared thermal radiation, which can be achieved within other target bands based on characteristic frequencies of phononic or excitonic materials.
Microscale optical beams can be especially useful when generated by micrometric platforms. Here, we achieve one such combination by exploiting the concept of the self-similar beam. Fresnel diffraction-based reformulation...Microscale optical beams can be especially useful when generated by micrometric platforms. Here, we achieve one such combination by exploiting the concept of the self-similar beam. Fresnel diffraction-based reformulation of the self-similar beam leads to a compact platform design realizable with 3D-printing of low-index photopolymers. The final design, refined through numerical simulations, is only 1050 nm high and 5500 nm wide and generates bright-core microbeams out of unstructured plane wave excitation. Experimentally, we realized the design by 3D-nanoprinting and produced self-similar bright beams that maintained ±15 µm beam width over the millimetric propagation range. Their characteristics are close to those of quasi-non-diffracting microbeams. We also confirmed the self-healing characteristic of the microbeams.
Fourier ptychographic microscopy (FPM) can achieve high-resolution and large field-of-view complex field imaging via phase retrieval and a synthetic aperture using a series of low-resolution intensity images captured und...Fourier ptychographic microscopy (FPM) can achieve high-resolution and large field-of-view complex field imaging via phase retrieval and a synthetic aperture using a series of low-resolution intensity images captured under angularly varying illumination. While powerful, it exhibits sensitivity to illumination angle deviation, which can cause significant artifacts during the reconstruction process. To address this limitation, we propose a Parallel Feature Shifting (PFS) strategy, a robust and universal illumination angle calibration method utilizing the lateral shift of features on a dual-sided calibration mask under oblique illumination. The PFS strategy can accurately retrieve the illumination vectors by calculating the relative shift between the ring and disk array patterns on the opposing surfaces of the calibration mask. By combining a rigorous physical model with system-agnostic operation principles, the PFS strategy demonstrates strong tolerance to misalignment and provides a universal framework for angle calibration in illumination-angle-encoded computational microscopy systems.
Compared with direct short-wave infrared (SWIR) detection, up-conversion imaging enables room-temperature SWIR imaging using mature visible-band detectors. However, poled crystals are limited by their small apertures, wh...Compared with direct short-wave infrared (SWIR) detection, up-conversion imaging enables room-temperature SWIR imaging using mature visible-band detectors. However, poled crystals are limited by their small apertures, while large-aperture critical phase-matched (CPM) bulk crystals usually suffer from walk-off-induced image degradation. Here we demonstrate broadband SWIR up-conversion imaging using a noncritical phase-matched KTiOPO crystal with a 6 mm × 7 mm aperture and a length of 0.5 mm. The system operates over a spectral range of 1.3-2.2 μm and achieves finest resolvable linewidths of 8.8 μm and 12.4 μm at illumination wavelengths of 1.334 μm and 1.792 μm, respectively. These values correspond to about 5-6× and 2× improvements in two orthogonal directions over the aperture-limited resolution of a representative 1 mm × 3 mm poled crystal. The absence of walk-off improves image fidelity, and the measured performance approaches the theoretical resolution limit. This study presents the first, to the best of our knowledge, comprehensive characterization of NCPM-based broadband up-conversion imaging and establishes a fixed-crystal route to high-resolution broadband SWIR up-conversion imaging.
Weyl points (WPs) have attracted widespread discussion in three-dimensional (3D) systems owing to their distinctive topological properties, yet the pursuit of two-dimensional (2D) WPs remains a formidable challenge. In e...Weyl points (WPs) have attracted widespread discussion in three-dimensional (3D) systems owing to their distinctive topological properties, yet the pursuit of two-dimensional (2D) WPs remains a formidable challenge. In electronic systems, 2D WPs are inherently fragile due to spin-orbit coupling, while photonic implementations typically rely on synthetic dimensions, resulting in only quasi-3D WPs. Here, we demonstrate genuine 2D WPs in an interlaced woven Kagome layer, where the out-of-plane braiding breaks inversion and mirror symmetries while preserving the layer-group symmetry LG 76 (p622) that pins chiral linear crossings at the Brillouin-zone vertices. By controlled stretching of one family of rods, we reduce the symmetry to a lower subgroup and directly track the motion of the WPs. The associated edge spectra reveal a controllable evolution from Weyl-connecting gapless states to a gapped valley-topological phase after full symmetry lifting. This work establishes a mechanically tunable platform for intrinsic 2D Weyl physics and reconfigurable topological wave transport.
The generation of arbitrary polarization states of light is essential for optical communication and photonic information processing. Photonic crystal and metasurface platforms supporting bound states in the continuum (BI...The generation of arbitrary polarization states of light is essential for optical communication and photonic information processing. Photonic crystal and metasurface platforms supporting bound states in the continuum (BICs) provide a powerful route for polarization engineering by tailoring the radiation from the resonant modes. However, existing approaches typically rely on static structural symmetry breaking or off-normal radiation, which limits continuous polarization tuning of vertical radiation. Here, we demonstrate a magneto-optical metasurface that generates arbitrary polarization states of light at normal radiation. By applying an external magnetic field with variable orientation, a symmetry-protected BIC is transformed into a quasi-BIC whose radiation polarization can be continuously tuned. The magneto-optical perturbation drives the controlled migration of polarization singularities in momentum space, allowing the emitted states to continuously span the entire Poincaré sphere without structural modification. This approach establishes a compact platform for actively tunable polarization sources and polarization-encoded photonic devices.
Many atmospheric laser applications rely on the long-range propagation of laser pulses. In this work, we demonstrate a method for remotely shaping laser beams by generating stable gaseous optical elements in air. These s...Many atmospheric laser applications rely on the long-range propagation of laser pulses. In this work, we demonstrate a method for remotely shaping laser beams by generating stable gaseous optical elements in air. These structures emerge from controlled gas dynamics driven by filamentation of a kilohertz picosecond Yb:YAG laser. We observe a new, to the best of our knowledge, air photonic structure-a tunable defocusing lens-attributed to the cumulative effects of low-density channels. Additionally, we show that self-focusing of a collimated Laguerre-Gauss beam can form a permanent air waveguide of 6 mm extending over more than 20 meters. Numerical simulations of the gas dynamics reproduce the observed features of a continuous wave (CW) probe beam injected into these optical structures. This air photonics strategy has broad potential applications in laser power modulation and atmospheric optics.
We demonstrate five dual-wavelength DFB lasers based on continuous-phase-shift gratings (CPSGs). The CPSG design preserves an effective coupling coefficient comparable to that of uniform Bragg gratings, while enabling de...We demonstrate five dual-wavelength DFB lasers based on continuous-phase-shift gratings (CPSGs). The CPSG design preserves an effective coupling coefficient comparable to that of uniform Bragg gratings, while enabling deterministic control of the dual-mode spacing via a global phase ramp implemented in a single lithography step. Beat-note spacings ranging from 50 GHz to 1 THz are achieved, with dual‑mode operation exhibiting a side‑mode suppression ratio (SMSR) above 33 dB over a DFB drive current range exceeding 40 mA, albeit with increased threshold and reduced slope efficiency for the smallest 50 GHz spacing. These results establish CPSG-based dual-wavelength DFB lasers as compact optical beat sources for millimeter-wave/THz photomixing and heterodyne systems.
A field-induced multimode liquid crystal (LC) switchable grating is proposed, fabricated via a patterned alignment process combined with a LC cell integrated with in-plane switching (IPS) electrodes. By applying voltages...A field-induced multimode liquid crystal (LC) switchable grating is proposed, fabricated via a patterned alignment process combined with a LC cell integrated with in-plane switching (IPS) electrodes. By applying voltages of different amplitudes, the grating enables flexible multimode switching: in the absence of an external voltage, it functions as a one-dimensional (1D) grating based on the patterned alignment; under a low driving voltage, it switches to a two-dimensional (2D) grating; and under a high driving voltage, it rapidly switches to another 1D grating (1D*) dominated by the IPS electrodes. Essentially, this grating is an alignment layer-electrode synergistically regulated phase grating, formed by the coupling of two independent gratings. The period sizes and fringe directions of the two constituent gratings can be flexibly tailored by virtue of photomask design, electrode arrangement, and exposure process parameters. In addition, it possesses advantages such as a simple fabrication process and flexible switching, exhibiting broad application prospects in fields including optical communication and 3D displays.
We propose a high-resolution inverse synthetic aperture radar (ISAR) imaging scheme based on bandwidth synthesis with photonic analog-to-digital converter (PADC) reception. In this architecture, multiple sub-band signals...We propose a high-resolution inverse synthetic aperture radar (ISAR) imaging scheme based on bandwidth synthesis with photonic analog-to-digital converter (PADC) reception. In this architecture, multiple sub-band signals are transmitted sequentially, while the echoes from all synthesized frequency bands are directly sampled by a wideband PADC. By preserving the original echo information and avoiding analog-domain de-chirp processing, the proposed scheme enables high-fidelity digital bandwidth synthesis for ultra-wideband radar imaging. In experiments, an equivalent ultra-wideband signal spanning 2-18 GHz was reconstructed from four sub-bands with a synthesized bandwidth of 11.2 GHz, achieving a range resolution of 1.1 cm. Two-dimensional ISAR imaging results further demonstrate the feasibility of the proposed approach.
Astro-combs are critical for achieving cm⋅s radial velocity (RV) precision in exoplanet detection, as they offer dense reference lines well matched to stellar absorption features. We demonstrate a blue-band astro-comb by...Astro-combs are critical for achieving cm⋅s radial velocity (RV) precision in exoplanet detection, as they offer dense reference lines well matched to stellar absorption features. We demonstrate a blue-band astro-comb by filtering a 1 GHz ytterbium fiber frequency comb with a passively stabilized zero-dispersion Fabry-Pérot cavity (FPC) and fully characterize the filtered spectrum using a homemade Fourier transform spectrometer (FTS). Our key finding is that the FPC transmission lines exhibit non-uniform spacing, with deviations mostly within 4 MHz (up to 10 MHz) relative to the average free spectral range of ~44.789 GHz-challenging the conventional assumption of uniformly spaced calibration markers. Despite this non-uniformity, averaging over 1340 resolvable comb teeth suppresses single-line RV errors (2 m·s) to an overall RV precision of 5.5 cm·s. Long-term stability tests over 45 days yield RV precision between 7 and 8 cm⋅s, confirming suitability for exoplanet detection campaigns. This work underscores the need for detailed spectral characterization of astro-combs, as FPC-induced spacing non-uniformity fundamentally influences calibration accuracy and provides critical insights for advancing cm·s-level RV precision.
Accurate knowledge of the Kerr nonlinear coefficient is essential for modeling nonlinear propagation in optical fibers, yet most established experimental techniques rely on coherent receivers or interferometric phase me...Accurate knowledge of the Kerr nonlinear coefficient is essential for modeling nonlinear propagation in optical fibers, yet most established experimental techniques rely on coherent receivers or interferometric phase measurements. Here, we demonstrate a low-complexity method for measuring using direct detection on a photodiode combined with digital Kramers-Kronig (KK) field reconstruction. A receiver-side pilot laser enforces the minimum-phase condition required for KK processing, enabling recovery of the complex optical field without a coherent receiver. Three-tone excitation produces correlated nonlinear phase shifts that are extracted from the reconstructed field and used to extract from the power-dependent differential phase. Experiments on telecom fibers ranging from 3.2 to 25.3 km yield values consistent with fiber specifications using only milliwatt-level optical powers.
As the scale of reconfigurable photonic chips increases, solutions are needed to address the increasing complexity of the electronic readout circuits needed to monitor the optical functionality. The number of these eleme...As the scale of reconfigurable photonic chips increases, solutions are needed to address the increasing complexity of the electronic readout circuits needed to monitor the optical functionality. The number of these elements is strictly related to the scale of the photonic chip, and it can represent a significant overhead, in terms of electrical connections and area occupation, when the optical complexity increases. Here, we propose two scalable methods for controlling programmable chips using a single readout circuit, by individually labeling each photonic device. Experimental results at 10 Gbit/s confirm the effectiveness of the approach, while simulation analyses highlight the trade-offs that need to be considered when employing the proposed techniques.
High-precision Mz/Mx atomic magnetometers have "dead zones", where the magnetic-field information will be lost because the light-atom interaction vanishes at specific field angles. To suppress dead zones, we propose a sc...High-precision Mz/Mx atomic magnetometers have "dead zones", where the magnetic-field information will be lost because the light-atom interaction vanishes at specific field angles. To suppress dead zones, we propose a scheme with polarization-gradient optical pumping field by using counter-propagating lin⊥lin beams. We found through experiments that the lin⊥lin scheme eliminates dead zones in the transverse plane of the probe beam propagation (minimum ∼40% normalized signal) but leaves two noncanonical magic-angle-like directions (≈30 and 150) in the longitudinal plane, which is distinct from the standard tensor magic angle (≈54 and 126). These observations are quantitatively explained using a multipole-based model formulated in terms of an effective, spatially averaged density matrix, which is the first time that the spatial average density matrix has been used for energy state analysis in atomic magnetometers. Under the probing of a linearly polarized light, the measured signal is determined by the field-angle-dependent projection of the atomic longitudinal alignment moment () onto the -defined quantization axis. Compared with other dead-zone elimination schemes, our scheme avoids polarization modulation and multi-cell architectures, showing potential for improving the spatial response range of compact atomic magnetometry.