Optics express最新文献

Non-line-of-sight (NLOS) imaging has seen rapid progress recently. However, owing to the limited sensor capacity, dynamic NLOS imaging still encounters challenges in dynamic scene analysis. Existing approaches reduce the number of sampling points or shorten the unit acquisition time to increase the frame rate, yet at the cost of lowered spatial resolution or signal-to-noise ratio of the measurements. To simultaneously achieve high-resolution and high-frame-rate transient measurements, we introduce TransVID, the first Transient Video Interpolation method built upon the Diffusion model. Given consecutive low-resolution measurements at a low frame rate, TransVID maps the upsampled measurements into the latent feature space via an encoder with tailored spatial-temporal attention. Subsequently, a conditional diffusion process is performed in the latent space to interpolate the latent features of the intermediate frames, which are then decoded and reconstructed to the high-resolution transient frames. Experimental results demonstrate that TransVID breaks the current frame rate limit of physical capture in NLOS imaging, successfully recovers hidden objects with a 128 × 128 resolution at 16 FPS from an original video of a 16 × 16 resolution at 4 FPS.

We propose an efficient scheme to manipulate spontaneous emission spectra using optical vortices carrying orbital angular momentum (OAM) in a coherently driven cold five-level atomic system assisted by a radio frequency (RF) or microwave field. Using experimentally achievable parameters, we find that the spontaneous emission is strongly influenced by quantum destructive interference. And we show that the structured light profile of the probe field can be transferred to the spontaneous emission spectrum via spontaneously generated coherence (SGC). With the aid of SGC, the intensities and detunings of the control and RF fields can be used to tailor the vortex-induced spontaneous emission spectra. When the control and RF fields are configured as vortex beams, it is demonstrated that the spontaneous emission can be coherently controlled through quantum interference by adjusting their topological charges (TCs). Furthermore, we explore intriguing optical properties of the vortex-induced spontaneous emission by varying the TCs of the probe and control fields. This coherently driven atomic system features three closely spaced levels, giving rise to multiple vortex-induced SGC pathways. Our scheme opens avenues for applications in structured light, ranging from optical storage to optical communication.

Tilted fiber Bragg gratings (TFBGs) are highly sensitive refractometric probes, but their broad cladding-mode spectra have long been considered incompatible with wavelength-division multiplexing. As a result, TFBG refractive-index sensors are generally restricted to single-point operation, despite their inherent advantages. Here, we demonstrate for the first time that multiple bare, uncoated TFBGs (inscribed with distinct grating periods and tilt angles) can be cascaded within a single-mode fiber and independently interrogated over an 80-nm bandwidth. Although the cladding-mode spectra strongly overlap, we show that first-order derivative spectrum analysis isolates the local slope of each cut-off mode, effectively suppressing the envelope distortions typically induced by upstream gratings. This enables reliable and decoupled multipoint refractive-index sensing, with sensitivities of 52-58 nm/RIU that are fully consistent with intrinsic TFBG performance in aqueous media and remain stable after cascading. The derivative method enhances the demodulation accuracy by up to 65% and preserves linearity (R² = 0.94-0.98) while maintaining cross-talk below 0.03 nm. These results overturn the longstanding belief that TFBG refractometers cannot be multiplexed, paving the way for compact, low-cost, and scalable quasi-distributed chemical and biological sensing networks based on TFBG arrays.

Flat optical components capable of dynamic multifunctional control are essential for next-generation imaging, anti-counterfeiting, and communication technologies. Here, we demonstrate a reconfigurable metalens based on a bilayer Sb₂Se₃ metasurface operating at 1064 nm in the near-infrared regime. By harnessing the large refractive index contrast between amorphous and crystalline phases and employing Pancharatnam-Berry phase engineering, the device enables non-volatile switching among tunable focal lengths, variable focus intensities, and dual- or single-focus modes. Reversible phase transitions of individual Sb₂Se₃ nanofins in upper and lower layers allow arbitrary switching between F₁, F₂, and combined F₁+ F₂ focusing states, with focusing efficiency exceeding 50%. Building on this, we further show programmable pattern generation across different focal planes by spatially controlling the phase states of meta-atom arrays, enabling intensity-tunable image rendering for compact, high-security optical anti-counterfeiting systems. This work advances programmable photonics through a scalable and integrable platform for adaptive flat optics.

Fiber-to-fiber gain is demonstrated in waveguide amplifiers fabricated from Al₂O₃:Nd³⁺ films. The Nd-doped aluminium oxide film is deposited using reactive sputtering, resulting in a polycrystalline film with an approximate ion concentration of 2.2 × 10²⁰ ions/cm³. An amplifier with a length of 5.5 cm is optically pumped at 805 nm, following a bi-directional pumping scheme. For an incident signal input power of -14.9 dBm, the amplifier shows an external gain at a signal wavelength of 1064 nm as large as 14.5 dB, limited by the available pump power. Under those conditions, a noise figure of 8.5 dB was measured. These results pave the way towards on-chip amplification for applications including biomedical imaging, spectroscopy, atmospheric LiDAR, and quantum technologies.

A high-power distributed feedback laser array suitable for optical I/O applications is demonstrated. The epitaxial structure incorporates a high-refractive-index layer in the N-doped region to improve single-transverse-mode characteristics and reduce internal loss, enabling single-mode operation at a ridge width of 5 µm with an internal loss of 3 cm^-1. An asymmetric π-phase-shift, implemented using the reconstruction-equivalent chirp technique, ensures high single-mode yield. The fabricated array achieves output powers above 300 mW per channel at 25 °C with 800 mA injection current and exhibits uniform channel spacing with side mode suppression ratios exceeding 50 dB. Stable single-longitudinal-mode operation is maintained without mode hopping over a broad current and temperature tuning range. Under simultaneous operation at an injection current of 300 mA per channel, all channels of the laser array deliver output powers exceeding 100 mW, with an average wavelength deviation of 0.0692 nm. The devices further show a minimum Lorentzian linewidth of 300 kHz, and relative intensity noise of -154 dB/Hz, demonstrating strong potential for high-speed optical interconnects.

We present a theoretical and computational framework for metasurface mirrors that switch optical angular momentum as a function of wavelength. The approach is based on controlling the phase retardance and amplitude balance of anisotropic meta-atoms to create a sharp wavelength threshold, termed a spectral horizon, where the reflected light reverses its spin and orbital angular momentum. The paper develops an operational definition of this spectral horizon, supported by analytical modeling, large-scale Monte Carlo validation, and full-field simulations of spatial intensity and phase profiles incorporating fabrication variability. The reference design, based on TiO₂ nanopillars operating near 1550 nm, exhibits a steep spectral transition, narrow switching bandwidth, and high efficiency that remain stable under realistic tolerances. These results support a passive and reproducible route to wavelength-selective angular momentum control with applications in wavelength-division multiplexing, quantum state routing, and spectrally encoded photonic logic. We focus on the formulation and statistical validation of a synthetic spectral horizon for angular momentum, which connects metasurface dispersion, device performance metrics, and fabrication tolerances in a unified framework.

The technology of integrated sensing and communication over fiber (ISACoF) has emerged as a key enabler for achieving high-speed communication alongside ubiquitous sensing capabilities in fiber-based short-reach networks. In this paper, we propose a digital subcarrier multiplexing (DSCM)-based ISACoF scheme for spectrally integrating the digital linear frequency-modulated (LFM) sensing signal into intensity modulation and direct detection (IM/DD) systems, enabling simultaneous sensing and communication through a shared IM transmitter. By jointly optimizing the bias voltage of the intensity modulator and the communication-to-sensing power ratio (CSPR), proof-of-concept experiments are carried out to evaluate the feasibility of the proposed DSCM-based ISACoF scheme. Experimental results demonstrate that the proposed DSCM-based ISACoF scheme is capable of transmitting a 16-Gbit/s 16-quadrature amplitude modulation (QAM)-DSCM signal over a 10-km IM/DD link. Simultaneously, distributed acoustic sensing with a sensitivity of 54 pε/Hz and a spatial resolution of 10 m can be achieved.

With the increasing demand for non-destructive ultra-smooth surface optical components in optical systems, a polishing liquid with asphalt interface modification was proposed for small tool polishing to meet application requirements. Dodecylbenzenesulfonic acid (DBSA) promotes the dispersion of abrasive particles, improves the stability of the polishing liquid, and simultaneously reduces the contact angle. Additionally, DBSA regulates the modification effect of mineral oil (MO) on the asphalt polishing pad through emulsification. This process addresses the issue of abrasive particle accumulation on the polishing pad, reduces the average load of effective abrasive particles at the interface, and promotes material removal primarily through mechanically induced chemical bond breaking. Under a scanning area of 20 × 20 µm², the surface roughness of quartz glass reaches Ra 0.097 nm, providing what we believe to be a novel approach to achieving an ultra-smooth surface without surface or subsurface destruction.

All-optical logic-gate-based switching is a prerequisite for photonic computing. This article introduces a logic-gate protocol for noncollinear four-wave mixing (FWM) of one attosecond extreme ultraviolet (XUV) with two few-femtosecond near infrared (NIR) pulses. Simulations show that the NIR carrier-envelope phases (CEPs) alter the spatial distribution of the XUV FWM emission, using doubly-excited states of gas-phase helium as an example. A complete set of logic gates-X(N)OR, (N)AND, and (N)OR-is realized for the 2s3p FWM signal at 63.66 eV with switching contrasts of 3.6 to 10.4. This theoretical study extends all-optical logic switching to the XUV and x-ray regimes and opens a new pathway for ultrafast photonic logic.