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We demonstrate the data transmission characteristics of a 1.96 µm laser in an indoor simulated smoke channel. An active mode-locked thulium-doped fiber laser at 1961.63 nm can be generated, and the repetition rate is 2.11 GHz corresponding pulse duration of 12.47 ps. Therefore, the pulse can be modulated by a 2.11 Gb/s digital sequence to act as a carrier light source. The transmission characteristics of signal light under different visibility conditions of 0.5, 0.05, and 0.005 km are studied. Compared with the back-to-back conditions, the signal-to-noise ratios of the carrier can decrease after passing through the smoke channels, which are 3.93, 7.1, and 9.08 dB, respectively. At the same time, the received power jitter can increase from ±0.16 to ±1.14dB. The sensitivity can be -19.52dBm at the visibility of 0.005 km. The experimental results show that thulium-doped mode-locked laser has an excellent performance in a smoke channel.In this paper, by phase-modulating an optical wavefront on circular symmetric Airy vortex beams, we present the circular symmetric Airy-like vortex beams propagating along predesigned parabolic trajectories. Our result shows that we can realize the propagation of an optical vortex with a closed ring lobe along an accelerating parabolic trajectory within a certain propagation distance by using this kind of phase-modulated circular symmetric Airy beam. The vortex that is superimposed on the beams is able to reproduce after being blocked. Additionally, a single twisted dark channel or multiple tornado dark channels with orbital angular momentum rotating along the predesigned parabolic trajectories can also be formed when we impose the off-axis optical vortex on this kind of beam, which has potential in applications of light capturing.A compact digital control system based on an all-programmable system-on-chip iodine-stabilized laser is presented for realization of the meter. The system is composed of ZYNQ7000, peripheral circuits, and human-computer interaction, which can operate independently. An nth-harmonic extraction algorithm with less resource consumption is used in this system. The digital system overcomes the problems of complex debugging, large volume, and manual locking. Additionally, customers can set up, calibrate, and upgrade the system by themselves. Its stability is similar to that of the current analog system, with long-term stability of up to 10-13. The repeatability of the two lasers with the digital system is approximately 1.5×10-11, and the absolute frequencies satisfy the international recommendation.A real-time trace gas detector for benzene is demonstrated. The measurement system takes advantage of modest enrichment through short adsorption periods to reach a ppt-level detection limit with a sampling cycle of 90 s, which includes sample adsorption, desorption, and a spectroscopic measurement. Benzene is collected on Tenax TA sorbent for 30 s and then detected from the enriched samples with photoacoustic spectroscopy. High sensitivity is achieved using cantilever-enhanced photoacoustic spectroscopy and a continuous-wave quantum cascade laser emitting at 14.8 µm wavelength, which corresponds to the absorption wavelength of the strongest benzene infrared band. We reach a detection limit of 150 ppt of benzene, over one sampling cycle. Interference from humidity and other common petrochemicals is evaluated.Due to the processing characteristics of laser cladding, the beads and joints of the laser cladding coatings have different grain sizes. We used the laser ultrasonic (LU) method to measure the distribution of the grain sizes of laser cladding coatings nondestructively. The surface acoustic wave amplitude was influenced by the grain size; hence, the amplitude varied for beads and joints because of their different attenuations. The spatial resolution of LU is higher than that of the traditional ultrasonic testing method, leading to a fringe distribution of the C-scan results in the scanning area. The LU results were verified through metallographic experiments. It was concluded that the LU method can be used to determine the grain sizes of coatings.In a previous paper [Appl. Opt. 61, C20 (2022)] it was proven that for a circular exit pupil and any optical path differences, the border of any spot diagram is integrated by the caustic surface and/or marginal rays. In this paper, the previous results are extended to annular (circular an elliptical) as well as hexagonal (single and segmented) exit pupils. Several examples of wavefronts affected by linear combinations of orthonormal Zernike aberrations are shown.We discuss and describe the development of an origination process for planar free-form micro-optical elements from a given optical design. The targeted masters serve as origination structures for a roll-to-roll mass fabrication process. Specifically targeted are complex, optically smooth, surface relief structures with variable structure heights in the range of 1-20 µm, with typical lateral sizes of more than 5 µm. The area of the targeted masters is in the range of 1cm2. The main part of the paper is devoted to the description of a self-developed grayscale laser direct-write platform enabling one- and two-photon absorption lithography, also in combination on one and the same sample. In the following, we describe both methods and show that both lead to excellent structural quality of surface micro-relief structures. As a showcase of what the system can do in principle, we designed and fabricated free-form micro-optical elements to project light from an LED as a defined light pattern onto a wall. The proper optical functionality of the fabricated element was shown within a demonstrator setup.This study proposes a particle polarization lidar that distinguishes raindrops and snowflakes based on individual precipitation particles' polarization information. As precipitation particles are several millimeters in size, the lidar signal from individual precipitation particles can be detected with a single laser pulse. Therefore, particle polarization lidar observation can obtain the range distribution of raindrops and snowflakes from the polarization information of individual precipitation particles. This paper reports the principle of the particle polarization lidar and vertical distributions of raindrops and snowflakes obtained by the lidar observations.In this work, based on the nonlinear electrooptic (EO) modulation model, the relationship between the polarization states and the birefringence modulation caused optical phase of c-axis barium titanate (BaTiO3) crystal film is investigated first. Then, under an ensemble effect of phase-polarization modulation (PPM), the photon polarization behavior of a lightwave in a BaTiO3 film waveguide and its dynamic conversion process is clearly presented. Further, the optical output and optical phase changes of a Mach-Zehnder interferometric (MZI) type EO intensity modulator based on a dynamic nonlinear optical birefringence modulation are theoretically modeled. As a result, the systematic simulations show that, for one-wave (2π) optical phase modulation (OPM), the full width at half-maximum of the output signal is efficiently compressed 30% more than the current OPM. Finally, the improvements of the MZI output signal by the PPM scheme are in accord with the experimental results.A laser-induced cavitation bubble shock forming technology is proposed for microgroove formation in thin copper. It is stamped by using the impact pressure generated by the laser breakdown of liquid. The impact-induced micro-formation of thin copper is studied by numerical simulation and experimentation. A finite-element model is developed, and the impact pressure created by laser-induced cavitation is measured to study the spatial distribution of impact pressure. The laser-induced cavitation process of the high-speed impact on thin copper is numerically simulated. The results of simulations are consistent with those of experiments, confirming the model's accuracy. The simulation is then used to study the dynamic formation and deformation behavior of the laser-induced cavitation impact of thin copper. The stress and thickness distributions during the formation of microgrooves in thin copper are also investigated. selleck chemical Furthermore, the influence of laser fluence and copper thickness on formation is studied. The results reveal that the high-speed impact forming of thin copper by laser-induced cavitation is due to three impact forces a plasma shock wave, a cavitation shock wave, and a microjet, and this technology can be used to form thin metal walls.Reflectographic analyses applied on paintings can be performed using cameras equipped with different detectors with different abilities in detecting and visualizing underdrawings, repainting, restorations, and other nonvisible information. In this research, the results obtained through thermographic imaging followed by statistical imaging postprocessing methods have been compared with those obtained with traditional reflectographic methods in the short-wave infrared range. The comparison has been performed studying the thermal sequence after a single pulse of light with a different spectrum of ad hoc mock-ups. Results showed that for limited cases, signal-to-noise ratio seems to be more relevant in obtaining reliable images of underdrawings with respect to the effect of optical absorption of visible light by painting layers.In recent years, compressive spectral imaging (CSI) has emerged as a new acquisition technique that acquires coded projections of the spectral scene, reducing considerably storage and transmission costs. Among several CSI devices, the single-pixel camera (SPC) architecture excels due to its low implementation cost when acquiring a large number of spectral bands. Although CSI allows efficient sampling, a complete reconstruction of the underlying scene is needed to perform any processing task, which involves solving a computationally expensive optimization problem. In this paper, we propose a fast method to classify the underlying spectral image by directly using compressed SPC measurements, avoiding reconstruction. In particular, the proposed method acquires an RGB image of the scene as side information to design the SPC coding patterns. Our design approach allows incorporating the similarity information of neighboring pixels from the RGB image into compressed measurements. After acquiring the compressed measurements with our designed coding patterns, we extract features of the scene to perform classification without reconstruction. After simulations, we obtained an overall accuracy of 95.41% and 97.72% for the Pavia University and Salinas spectral images, respectively. Furthermore, we tested our approach in the laboratory and classified our own dataset, which has four different materials flowers, sand, grass, and dry leaves, with an overall accuracy of 94.66%.The rice kernel inside a hull is composed of the embryo and endosperm. The embryo or germ of the rice seed will grow and become the shoot and the root parts of a seedling, while the endosperm is an important nutrient source for the embryo in the early stages. Hence, the health of seedlings depends particularly on the sizes of the embryo and endosperm. In this work, we propose and experimentally demonstrate how the embryo and endosperm areas of brown rice can simply be determined. Our key idea is based on the utilization of a smart mobile device equipped with our specifically designed lens module arranged in a simple cross-polarization imaging configuration for acquiring a rice grain image upon the illumination of a white light source and then spatially analyzing the sizes of embryo and endosperm areas. The prototype shows promising results in identifying the sizes of the embryo and endosperm within 2 s per seed with a measurement error of less then 9% compared with the use of off-the-shelf image editing software.