Guthriewaddell5951

While optical aberrations caused by atmospheric turbulence have been extensively investigated and well characterized, recent research has identified structural differences in optical phase distortions caused by aircraft-induced, compressible turbulence. These so-called aero-optical distortions can be a critical obstacle in the development of airborne optical systems and reduce the fidelity and on-target intensity of optical beams. Using a model index-of-refraction spectrum that accounts for changes in density due to both temperature and pressure fluctuations in aero-optically active flow fields, expressions for the two-dimensional phase distortion over an aperture are developed. From these results, relations among $\rm OPD_\rm rms$, turbulent flow scales, and aperture size are examined while accounting for the effects of piston and tip/tilt corrections. Additionally, using the model spectrum, resolution requirements for wavefront sensors and numerical simulations of aero-optical flows are examined.Optical diagnostics of gas-phase pressure are relatively unusual. In this work, we demonstrate a novel, rapid, and robust method to use laser-induced grating scattering (LIGS) to derive this property in real time. Previous pressure measurements with LIGS have employed a signal fitting method, but this is relatively time-consuming and requires specialist understanding. find more In this paper, we directly measure a decay lifetime from a LIGS signal and then employ a calibration surface constructed using a physics-based model to convert this value to pressure. This method was applied to an optically accessible single-cylinder internal combustion engine, yielding an accuracy of better than 10% at all tested conditions above atmospheric pressure. This new approach complements the existing strength of LIGS in precisely and accurately deriving temperature with a simple analysis method, by adding pressure information with a similarly simple method.A single-shot dual-wavelength digital holographic microscopy with an adjustable off-axis configuration is presented, which helps realize real-time quantitative phase imaging for living cells. With this configuration, two sets of interference fringes corresponding to their wavelengths can be flexibly recorded onto one hologram in one shot. The universal expression on the dual-wavelength hologram recorded under any wave vector orientation angles of reference beams is given. To avoid as much as possible the effect of zero-order spectrum, we can flexibly select their carry frequencies for the two wavelengths using this adjustable off-axis configuration, according to the distribution feature of object's spatial-frequency spectrum. This merit is verified by a quantitative phase imaging experiment for the microchannel of a microfluidic chip. The reconstructed phase maps of living onion epidermal cells exhibit cellular internal life activities, for the first time to the best of our knowledge, vividly displaying the progress of the nucleus, cell wall, cytoskeleton, and the substance transport in microtubules inside living cells. These imaging results demonstrate the availability and reliability of the presented method for real-time quantitative phase imaging.The temperature dependence of the $\rm O_2$ and $\rm CO_2$ S-branch linewidths in a 30/70% $\rm O_2 - \rm CO_2$ mixture between 295 K and 1900 K has been studied by a picosecond time-resolved pure rotational coherent anti-Stokes Raman scattering (RCARS) approach. The S-branch Raman linewidths are required for diagnostics of thermodynamic properties in oxyfuel combustion processes by RCARS, where this mixture is of special interest, because it is regularly used to replace air when transiting from air-fed to oxyfuel combustion. The obtained linewidths for oxygen and carbon dioxide show a strong deviation from pure self-broadened linewidths and previously used Q-branch linewidths, respectively. A discussion on the expected impact on RCARS thermometry and concentration evaluations as well as a description of specific properties of oxygen and carbon dioxide and their effect on the dephasing behavior of the Raman coherences and, thereby the Raman linewidths, is included, along tabulated linewidths data of both molecules.We consider the GaAsP/AlGaAs/GaAs laser design with two different quantum wells for simultaneous generation of $\rmTE_0$ and $\rmTM_0$ modes having different frequencies in near-IR range. We theoretically investigate the possibility of effective difference frequency generation in the 7.5-8 and 10.5-11 THz regions in the laser design proposed. Resonant increase of second-order susceptibility in AlGaAs in these ranges provides sufficient generation efficiency. We demonstrate an output power-conversion factor for the difference frequencies in the 7.5-8 THz range to be up to $4 - 8\;\rmMW^- 1$ at room temperature in such a laser.Computational ghost imaging (CGI) allows us to reconstruct images under a low signal-to-noise-ratio condition. However, CGI cannot retrieve phase information; it is unsuitable for observation of transparent objects such as living cells. A phase imaging method with CGI architecture is proposed. The proposed method realizes phase imaging with a simple optical setup by introducing pupil modulation differential phase contrast (PMDPC) to CGI. In PMDPC, phase information can be obtained from intensity distributions, which have phase gradient information, and its optical setup is similar to that of CGI. Therefore, the two methods are highly compatible, and the introduction of PMDPC to CGI can be easily achieved. Numerical simulation and an optical experiment demonstrated the feasibility of the proposed method.The paper presents a method for automated defect identification from fringe patterns. The method relies on computing the fringe signal's Wigner-Ville distribution followed by a supervised machine learning algorithm. Our machine learning approach enables robust detection of fringe pattern defects of varied shapes and alleviates the limitations associated with thresholding-based techniques that require careful control of the threshold parameter. The potential of the proposed method is demonstrated via numerical simulations to identify different types of defect patterns at various noise levels. In addition, the practical applicability of the method is validated by experimental results.