Applied optics最新文献

Ghost imaging is an indirect imaging method that utilizes the correlation properties of light to reconstruct the real-space image of an object. While originally developed in the spatial and temporal domains, its principles can be extended into the spectral domain by spatially dispersing broadband light and pseudo-randomly modulating its spectral components. In this work, we present a proof-of-concept implementation of computational spectral ghost imaging, combined with a deep learning framework to dramatically improve reconstruction fidelity and reduce measurement acquisition time. We introduce Spectral Ghost Imaging using Convolutional Neural Network (SGICNN), an encoder-decoder model trained exclusively on simulated data. Remarkably, SGICNN achieves high-fidelity image reconstruction and effective denoising of rudimentary spectral ghost images generated from as few as 8000 realizations, surpassing the accuracy of images constructed with 100,000 measurements. This corresponds to more than 10× reduction in acquisition time without compromising image quality. Our proposed approach is robust, straightforward, and holds strong potential for remote spectral sensing and high-resolution integrated spectrometers.

Metasurface transmission, where light of different wavelengths or modes is redistributed and regulated by the metasurface structure, plays a crucial role in modern photonics and nano-optics research. Herein, an in-plane symmetry-breaking approach is designed to excite quadruple transmission dips using the LiNbO₃ metasurface based on the leaked plasmonic bound states in the continuum (BIC). The influence of the difference between the major and minor diameters of the ellipse of the LiNbO₃ metasurface is accounted for, and the C_4v symmetry is maintained. According to the theoretical derivation, four quasi-BICs are obtained, with the highest quality factor (Q-factor) reaching 2.1×10⁴ and the figure of merit being 5707RIU^-1. The multi-level decomposition and near-field analysis of the four specific BIC modes indicate that the modes are excited by toroidal dipoles and magnetic quadrupoles rather than any related guided-mode resonances. The results reveal that the four resonances are polarization-independent, and their properties are maintained even for circularly polarized light. The results provide insights into the utilization of LiNbO₃ in advanced integrated nonlinear optics for integrated optics, biosensing, filtering, and lasers.

This paper reviews the WALES mission by the European Space Agency (ESA) and the HALO missions conducted by Langley Research Center (LaRC) of NASA. It evaluates potential risks associated with spaceborne applications by examining factors such as single-pulse energy, pulse repetition frequency, optical frequency stability, efficiency, spectral purity, and reliability. The review also explores advancements in solid-state laser technology operating at 820 nm over the past two decades, as well as recent developments in diode-pumped Er:YAG lasers. Key innovations from these technologies have been incorporated into differential absorption lidar transmitters to enhance performance. Separating weather forecasting from climate-change research is recommended for spaceborne missions. The 935 nm spectral band is optimal for water vapor DIAL measurements in the upper troposphere and lower stratosphere (UTLS). In contrast, the 820 nm band is ideal for measurements in the lower troposphere.

We demonstrate a Vernier effect-enhanced all-fiber gas pressure sensor with an extremely simple structure. The sensor consists of a rectangular air cavity near the end face of a single-mode fiber (SMF) fabricated by femtosecond laser micromachining. The two walls of the air cavity and the end face of the SMF form micro cascaded Fabry-Perot interferometers to generate the Vernier effect. The sensor exhibits a gas pressure sensitivity of 79.69 nm/MPa within a range of 0.1-2.5 MPa, an ultralow temperature cross-sensitivity of 0.0002 MPa/°C, and excellent stability. Owing to its straightforward fabrication and outstanding performance, the sensor holds significant potential for mass production and application in confined spaces for high-precision gas pressure monitoring.

Given the limited bandwidth of radio frequency and acoustic waves, alongside the growing demand for high-speed data transmission in underwater applications, underwater wireless optical communication (UWOC) has emerged as a promising and viable alternative. Nevertheless, UWOC systems face significant challenges due to performance degradation attributed to underwater attenuation, oceanic turbulence, bubble-induced blockages, and uncertainty in receiver positioning. This paper proposes a protocol design for reliable and energy-efficient UWOC operation. Specifically, we introduce an incremental redundancy hybrid automatic repeat request scheme integrated with energy harvesting capabilities. Additionally, a comprehensive and realistic UWOC channel model is developed to accurately characterize environmental impairments. To assess the system performance, we present a Markov chain-based analytical framework capable of deriving key performance metrics including average bit error rate, average throughput, average packet delay, and packet loss probability. Theoretical analysis is validated through the Monte Carlo simulations, confirming the effectiveness of the proposed design compared to state-of-the-art solutions.

This publisher's note reports corrections to Appl. Opt.64, 6848 (2025)10.1364/AO.567814.

This publisher's note reports corrections to Appl. Opt.64, 6803 (2025)APOPAI0003-693510.1364/AO.564737.

The large-aperture CPP is widely used in inertial confinement fusion systems. It is a key diffractive optical element to achieve beam shaping and smoothing. Successful ignition fusion has placed high requirements on its surface accuracy and gradient. The MRF used to imprint large-aperture CPP will introduce mid-spatial frequency errors, which will seriously affect the performance of CPP and the further convergence of subsequent residual errors. Smooth is often used to control it. However, when facing CPP with a larger gradient, the smoothing effect is not ideal. When smoothing and smoothing mid-spatial frequency errors, the accuracy of the low-frequency surface shape and the high-gradient characteristics are often destroyed, or the suppression of mid-spatial frequency errors is not obvious. At this stage, there is a lack of research on this part. First, this paper explains the limitations of smoothing. To study the influence of smoothing processes with polishing disks of different sizes on introducing mid-spatial frequency, experiments were conducted. The influence of smoothing on each frequency band is systematically analyzed, and it is confirmed that smoothing effect on mid-spatial frequency errors on large-aperture high-gradient CPPs is weakened or even ineffective. Second, a method based on spatial filtering in MRF is proposed and applied to the imprinting of large-aperture high-gradient CPPs, achieving a residual error RMS of 31 nm within the clear aperture. Compared to the 45 nm obtained using traditional methods, the precision is improved by over 30%. This study reveals the mechanism and limitations of the smoothing process on error control in various frequency bands of high-gradient CPP and verifies the effectiveness of what we believe to be is a newly proposed method. It also provides a reliable technical approach for the manufacture of large-aperture high-gradient CPP and solves the problems of fairing surfaces and the failure to suppress intermediate frequency errors and destruction of surface shape when facing high-gradient CPP.

This paper presents a method to measure and correct the non-linearity of a high-resolution digital photodetector based on photon flux variation. This so-called "derivative sampling method" requires no calibrated light source or reference and has been successfully implemented with two SLEDs. This setup could be easily adapted for future satellites for accurate post-launch in-orbit calibration. A correction greater than one order of magnitude has been achieved.

We propose and demonstrate a novel fiber optic temperature sensor (FOTS), to our knowledge, that simultaneously achieves both high sensitivity and rapid response. The FOTS is based on a compact Solc-Sagnac interferometer that incorporates thin polarization-maintaining fibers (TPMFs). Splicing two TPMFs of different lengths at a certain angle could achieve the Vernier effect to enhance sensitivity. The low thermal capacity of TPMF could significantly enhance the dynamic response of a harmonic Vernier effect-based FOTS. Theoretical and simulation analyses demonstrate that a distinct normal Vernier effect is generated when two TPMFs of nearly equal length are fused at a 45° splicing angle between their fast axes. The different-order harmonic Vernier effect is realized by configuring the length of one TPMF to be an additional detuning factor plus an integer multiple of the other TPMF length, and the inner-envelope fitting technique is also proposed. The impact of different-order harmonics (i) and the detuning factor (ΔL₀) on sensitivity is investigated. The experiments demonstrate that the temperature sensitivity is directly proportional to the harmonic order (i) and inversely proportional to the detuning factor (ΔL₀). When the FOTS realized the second-order Vernier effect, it achieved a temperature sensitivity of 27.12 nm/°C. The FOTS features high sensitivity, simple structure, ease of manufacturing, rapid response, low hysteresis effect, and excellent stability. It holds significant potential for engineering applications requiring real-time temperature monitoring and precise temperature control.