The marine atmosphere exhibits different turbulence spectrum characteristics when compared to the turbulence spectra of the land atmosphere and underwater medium. The performance of M-ary pulse position modulated (PPM) optical wireless communications (OWC) systems operating in the marine atmosphere, as measured by the bit error rate (BER), is studied here. In our investigation, the scintillation index and the average intensity in marine atmospheric turbulence are used. The variations of BER performance are reported against the marine atmospheric turbulence parameters for various values of the average current gain of the avalanche photodetector (APD), data bit rate of the OWC link, and M value of the M-ary PPM.A SiO2/TiO2 bilayer thin-film-based fiber optic humidity sensor was fabricated via a modified dip coating process with enhanced sensitivity. SiO2 film was coated on the surface of the fiber core, followed by deposition of the TiO2 layer on SiO2. The relative humidity (RH) is measured by modulation in intensity of the transmitted laser at room temperature. The optical fiber humidity sensor based on SiO2/TiO2 film shows two-segmented linearity in measurement with sensitivities of 5.35 and 1.94 µW/% RH at 15%-50% RH and 50%-95% RH, respectively. The response time and recovery time are 25 s and 50 s, respectively. To our knowledge, the superior response time and recovery time of the sensor in our study were achieved over those fiber optic humidity sensors reported with modulation in intensity. Furthermore, this fiber optic humidity sensor has a good reproducibility and long-term stability. The sensing mechanism is attributed to effects of moisture on the refractive index and the light absorption coefficient of SiO2 film and modulation in the transmission characteristic of evanescent waves in the optical fiber.Saccharomyces cerevisiae(S. cerevisiae) has been classically used as a treatment for diarrhea and diarrhea-related diseases. However, cases of the fungal infections caused by S. cerevisiae have been increasing in the last two decades among immunocompromised patients, while a long time was spent on S. cerevisiae isolation clinically so it was difficult to achieve timely diagnosis the diseases. Here, a novel approach for isolation and selection of S. cerevisiae is proposed by designing a microfluidic chip with an optically induced dielectrophoresis (ODEP) system. S. cerevisiae was isolated from the surroundings by ODEP due to different dielectrophoretic forces. Two special light images were designed and used to block and separate S. cerevisiae, respectively, and several manipulation parameters of ODEP were experimentally optimized to acquire the maximum isolation efficiency of S. cerevisiae. The results on the S. cerevisiae isolation declared that the purity of the S. cerevisiae selected by the method was up to 99.5%±0.05, and the capture efficiency was up to 65.0%±2.5 within 10 min. This work provides a general method to isolate S. cerevisiae as well as other microbial cells with high accuracy and efficiency and paves a road for biological research in which the isolation of high-purity cells is required.Vibrations cause many problems such as displacement, distortion, and defocusing in microscopic imaging systems. Because vibration errors are random in direction, amplitude, and frequency, it is not known which aspect of the image quality will be affected by these problems and to what extent. Polarization parametric indirect microscopic imaging (PIMI) is a technique that records polarization parameters in a conventional wide-field reflection microscope using polarization modulation of the illumination beam and additional data analysis of the raw images. This indirect imaging technique allows the spatial resolution of the system to be improved. Here, the influence of vibration on the image sharpness and spatial resolution of a PIMI system is analyzed theoretically and experimentally. Degradation in the sharpness of PIMI images is quantified by means of the modulation transfer function and deterioration in the effective spatial resolution by the Fourier ring correlation. These results show that the quality of PIMI images can be improved significantly using vibration isolation.Due to complications of the off-axis three-mirror anastigmat (TMA) telescope, each optical element in the off-axis TMA telescope is introduced with theoretical eccentricity and tilt. Moreover, the introduction of freeform surfaces and other optical elements with complex surface features generally causes the initial alignment accuracy of the optical path to be low. A large initial alignment error amplifies the sensitivity of the misalignment calculation accuracy to the measurement error of the Zernike coefficient, resulting in difficulty obtaining convergence results for a computer-aided alignment algorithm. Considering the above issues, the alignment sensitivity of each component in the optical path is analyzed in this. The large conditional number of the sensitivity matrix results in poor algorithm robustness. Thus, an adaptive damping factor least-squares algorithm model is proposed and derived to improve the efficiency of the classical least-squares algorithm. A method for piecewise optimization of the damping factor is also deduced. Experiments based on a 0.6 m off-axis TMA telescope verify the effectiveness of the algorithm. Simulation and integration experiments show that the proposed method can reduce the accuracy requirements of the initial alignment and improve the adaptability of Zernike coefficient measurement noise. The alignment procedure is carried out for three iterations, and the average of the five field-of-view wave aberration values is enhanced from 2.1λ (RMS; λ=632.8nm) to 0.09λ (average). learn more The improved algorithm can solve the large initial alignment error of a nonsymmetrical off-axis reflective optical system with a freeform surface as well as the problem of the low success rate of the misalignment value due to low Zernike coefficient measurement accuracy.Subsurface damage (SSD) induced during conventional manufacturing of optics contributes mainly to a reduction in the performance and quality of optics. In this paper, we propose the application of full-field optical coherence tomography (FF-OCT) as a high-resolution and nondestructive method for evaluation of SSD in optical substrates. Both ground and polished surfaces can be successfully imaged, providing a path to control SSD throughout the entire optics manufacturing process chain. Full tomograms are acquired for qualitative and quantitative analyses of both surface and SSD. The main requirements for the detection of SSD are addressed. Data processing allows the removal of low-intensity image errors and the automatic evaluation of SSD depths. OCT scans are carried out on destructively referenced glass samples and compared to existing predictive models, validating the obtained results. Finally, intensity projection methods and depth maps are applied to characterize crack morphologies. The experiments highlight differences in crack characteristics between optical glasses SF6 and HPFS7980 and illustrate that wet etching can enhance three-dimensional imaging of SSD with FF-OCT.