The degradation of image quality in space-based remote sensing is a critical challenge due to atmospheric disturbances. In this paper, we propose a new model to simulate image blur effects caused by turbulence and aerosol scattering. It also analyzes a distortion vector field to simulate the distortion effects from atmospheric turbulence. Using this time-varying physical model, we present a generative adversarial network called MSFFA-GAN. It uses a multi-scale feature fusion and attention mechanism to analyze and apply optimal constraints on deep neural networks for atmospheric impact parameters. This helps our network handle complex atmospheric conditions that cause image degradation. Experimental results show that MSFFA-GAN improves the peak signal-to-noise ratio (PSNR) by 5.05 dB and the structural similarity index (SSIM) by 4.43%. It effectively restores degraded images and enhances the image quality of remote sensing systems.

Correcting wavefront distortion caused by atmospheric turbulence is crucial for atmospheric optics. To evaluate correction systems, a real and fast atmospheric turbulence time-evolving model is needed. We proposed a model for a time-evolving turbulence phase screen (PS) based on its fractal nature, which achieves scale transformation under time or space. According to fractional Brownian motion, an interpolation algorithm is proposed to enhance the spatio-temporal resolution of PS efficiently. Additionally, a grid-based time-evolving PS generation method is proposed combining the covariance matrix and temporal spectra. The results demonstrate that our method can efficiently generate time-evolving PS with high spatio-temporal resolution and accuracy, and the interpolation algorithm introduces a slight deviation of less than 2%, which has a minimal impact on the overall results. The fractal nature of atmospheric turbulence has enabled the generation of PS with high accuracy, efficiency, and flexibility. This advancement is meaningful for atmospheric turbulence simulation and related atmospheric optics fields.

This study investigates the effects of laser off-nadir angles on sea surface echo dynamic range in airborne oceanic lidar. Using a dual-wavelength (486/532 nm) system with fixed off-nadir angles, varied aircraft rolls generated adjustable off-nadir angles. Experimental results reveal two to three orders of magnitude sea surface signal variations at 0°–35° off-nadir angles. A range of experimental results have shown that when the aircraft is at a lower altitude, saturation occurs at 0°–10° but is avoided at 15°–35°. Comparisons with simulations confirm that optimizing off-nadir angles reduces dynamic range occupancy and prevents saturation, enhancing lidar performance in oceanic profiling.

A method of spectrum estimation based on the genetic simulated annealing (GSA) algorithm is proposed, which is applied to retrieve the three-dimensional wind field of typhoon Nangka observed by our research group. Compared to the genetic algorithm (GA), the GSA algorithm not only extends the detection range and guarantees the accuracy of retrieval results but also demonstrates a faster retrieval speed. Experimental results indicate that both the GA and GSA algorithms can enhance the detection range by 35% more than the least squares method. However, the convergence speed of the GSA algorithm is 17 times faster than that of the GA, which is more beneficial for real-time data processing.

This paper has proposed an experimental system for non-orthogonal multiple access (NOMA) wireless optical communication in challenging underwater turbulent environments, employing the gallium nitride (GaN)-based micro-LED array. This design of the GaN-based micro-LED array enables the independent transmission of signals from distinct data streams within the NOMA framework, facilitating direct optical power-domain superposition of NOMA signals. The experimental setup involves emulating oceanic turbulence channels, characterized by varying the level of scintillation intensity, to thoroughly investigate the bit error rate (BER) performance. The outcomes unequivocally demonstrate the superiority of our proposed NOMA scheme, as compared to conventional circuit-driven optical NOMA systems utilizing fixed LED array grouping, particularly in the presence of turbulent underwater channels. The proposed NOMA scheme exhibits consistently superior BER performance and maintains excellent linearity at the lower frequencies while effectively mitigating signal distortion at the higher frequencies.

Responding to the urgency of remote sensing for monitoring large concentrations of methane leakage, a high-speed modulation continuous laser methane leakage remote methodology based on a near-infrared single-photon avalanche diode detector (SPAD) and a lower power distributed feedback laser was developed. Based on the proposed laser modulation and time-correlated single-photon counting method, the method could simultaneously detect the methane concentration and background target distance. The effects of SPAD dead time and after-pulse probability on the intensity of methane spectra were investigated. The proposed ranging and methane sensing method was also demonstrated by conducting outfield observation through the verification system. The measured methane absorption spectral intensity was verified and consistent with theoretical value. The initial validation results provide a new scheme for subsequent single-photon gas detection, and reference for subsequent methane monitoring equipment development.

A real-time wavefront sensing method for arbitrary targets is proposed, which provides an effective way for diversified wavefront sensing application scenarios. By using a distorted grating, the positive and negative defocus images are simultaneously acquired on a single detector. A fine feature, which is independent of the target itself but corresponding to the wavefront aberration, is defined. A lightweight and efficient network combined with an attention mechanism (AM-EffNet) is proposed to establish an accurate mapping between the features and the incident wavefronts. Comparison results show that the proposed method has superior performance compared to other methods and can achieve high-accuracy wavefront sensing in varied target scenes only by using the point target dataset to train the network well.

The infrared imaging windows of the hyper/supersonic optical dome are encountering severe aero-optical effects (AOEs), so a flow control device, the ramp vortex generator array (RVGA) is proposed based on the ramp vortex generator to inhibit the supersonic mixing layers’ AOE, which is done by the nanotracer-based planar laser scattering technique and ray-tracing method. The experiments prove that under different pressure conditions, RVGA can reduce the mean and standard deviation of the root mean square of the optical path difference (OPDrms) and reduce the supersonic mixing layers’ thickness and mixture a great deal. The AOE of the pressure-matched mixing layer is the weakest. Higher RVGA results in better optical performance. RVGA has the potential to be applied to supersonic film cooling to reduce aero-optical aberrations.

The multilongitudinal mode (MLM) high-spectral-resolution lidar (HSRL) based on the Mach–Zehnder interferometer (MZI) is constructed in Xi’an for accurate measurements of aerosol optical properties. The critical requirement of the optimal match between the free spectral range of MZI and the longitudinal mode interval of the MLM laser is influenced by the laboratory temperature, pressure, and vibration. To realize the optimal separation of aerosol Mie scattering signals and molecular Rayleigh scattering signals excited by the MLM laser, a self-tuning technique to dynamically adjust the optical path difference (OPD) of the MZI is proposed, which utilizes the maximum ratio between the received power of the Mie channel and Rayleigh channel as the criterion of the OPD displacement. The preliminary experiments show the feasibility of the MLM-HSRL with self-tuning MZI and the stable performance in the separation of aerosol Mie scattering signals and molecular Rayleigh scattering signals.

We introduce the Stokes scintillation indices and the corresponding overall Stokes scintillations for quantitatively studying the fluctuations of both the intensity and polarization of an optical vector beam transmitting through the atmospheric turbulence. With the aid of the multiple-phase-screen method, we examine the Stokes fluctuations of a radially polarized beam in Kolmogorov turbulence numerically. The results show that the overall scintillation for the intensity distribution is always larger than the overall scintillation for the polarization-dependent Stokes parameters, which indicates that the polarization state of a vector beam is stabler than its intensity distribution in the turbulence. We interpret the results with the depolarization effect of the vector beam in turbulence. The findings in this work may be useful in free-space optical communications utilizing vector beams.

Orbital angular momentum (OAM) is a fundamental physical characteristic to describe laser fields with a spiral phase structure. Vortex beams carrying OAMs have attracted more and more attention in recent years. However, the wavefront of OAM light would be destroyed when it passes through scattering media. Here, based on the feedback-based wavefront shaping method, we reconstitute OAM wavefronts behind strongly scattering media. The intensity of light with desired OAM states is enhanced to 150 times. This study provides a method to manipulate OAMs of scattered light and is of great significance for OAM optical communication and imaging to overcome complex environment interference.