Juulhardy0095

Given an arbitrary input wavefront, we derive the analytical refractive surface that refracts the wavefront into a single image point. The derivation of the surface is fully analytical without paraxial or numerical approximations. read more We evaluate the performance of the surface with several cases, and the results were as expected.Nonintrusive, quantitative measurements of thermodynamic properties of flows associated with propulsion systems are pivotal to advance their design and optimization. Laser-based diagnostics are ideal to provide quantitative results without influencing the flow; however, the environments in which such flows exist are often not conducive for such techniques. Namely, they often lack the optical accessibility required to facilitate the delivery of incident laser radiation and the subsequent collection of induced signals. A particularly challenging, yet crucial, task is to measure thermodynamic properties of plumes issuing from thrusters operating within a vacuum chamber. Large chambers used to simulate the vacuum of space generally lack optical ports that can facilitate complex laser-based measurements. Additionally, the near-vacuum environments within such chambers coupled with the ability of thrusters to efficiently expand the gas flowing through their nozzles lead to plumes with prohibitively low number densities (pressures below 1 Torr). Thus, there is a need to develop a diagnostic system that can offer high throughput without the use of free-space optical ports. Moreover, facilities where propulsion systems are tested typically lack vibrationally isolated space for diagnostic equipment and accurate climate control. As a result, such a high-throughput system must also be compact, versatile, and robust. To this end, the present work describes a fiber-coupled, multipass cell, spontaneous Raman scattering spectroscopy system. This system is intended to provide accurate temperature measurements within low-pressure environments via H2 rotational Raman thermometry. Proof-of-principle measurements are successfully performed at pressures as low as 67 Pa (500 mTorr). Techniques to maintain the signal-to-noise ratio at lower pressures, and the trade-offs associated with them, are discussed and evaluated. Finally, the ability of this system to facilitate additional quantitative measurements is also discussed.We demonstrate a new, to the best of our knowledge, dimensional "horizontal optimization" scheme, which can improve the high-speed characteristics of a PIN photodetector by designing the incident optical field distribution. First, coaxially incident faculae with the same peak and same power are studied and simulated, revealing that the bandwidth of the photodetector illuminated by uniform light is higher than that of the device illuminated by nonuniform light. Next, an annular optical field is designed incident to the photodetector, and the bandwidth is further improved. For a PIN photodetector, by carefully optimizing the incident optical field distribution, the photodetector bandwidth under an annular optical field can be increased significantly compared with that under conventional coaxial illumination.Our current work exploits direct laser writing (DLW) and low one-photon absorption (LOPA) in a low-cost three-dimensional optical fabrication system designed to print micrometric polymeric structures. Micropedestals were obtained by focusing a laser beam on a photoresist layer deposited on a silica glass substrate. Subsequent coating with rhodamine 6G dye allows these pedestals to function as microlasers upon optical excitation at 532 nm. Our microlasers, with a diameter of ∼53µm and a height of ∼40µm, exhibit a broad fluorescence peak in the spectral range 540-600 nm, in addition to narrow lasing peaks, exhibiting quality factors Q exceeding 2000 and a lasing threshold of ∼5µJcm-2. The observed free spectral range associated with the lasing peaks of ∼1.3nm is consistent with simulations, which we include in this paper. In addition, we present simulations for the longitudinal shift of the patterning laser spot, which occurs particularly for relatively thick photoresist layers, coupled with a large index contrast at the photoresist top surface. Such a shift could introduce errors in the resulting microfabricated structures if left unaccounted for. We hope that our work will contribute to the development of microlasers for various photonic applications, particularly if dimensions can be reduced, for on-chip optical communications and data processing.In this paper, we present a novel strategy for fabricating surface-enhanced Raman scattering (SERS) optical probe modified monolayer gold nanoparticles (AuNPs) by a seed-mediated growth method. The morphology and optical properties of the samples were characterized by transmission electron microscopy, scanning electron microscopy, and UV-visible absorption spectroscopy. The results show that the resulting probes exhibit high sensitivity with a detection limit down to 10-9mol/L for Methylene Blue solution and 10-8mol/L for both Crystal Violet and Rhodamine 6G solutions. Furthermore, the probes show an excellent reproducibility (relative standard deviation of 9.2% at 1621cm-1) and good stability, and the SERS spectra can be reproduced after storing the probes for one month in air. Finally, by finite-element simulations, we investigate the electromagnetic field distribution of the fiber facet modified with AuNPs. This work provides a promising potential of prepared SERS fiber probes and has broad application prospects in food safety, pesticide residue analysis, and environmental surveillance.We propose a space-time block coded multiple input single output (STBC-MISO) terrestrial-satellite laser communication uplink system based on orthogonal frequency division multiplexing (OFDM) modulation. It further uses Málaga distribution to simulate near-ground turbulence. Considering the combined effects of the uplink light intensity scintillation, beam wander, and angle-of-arrival fluctuation, a closed expression of the terrestrial-satellite uplink bit error rate for the proposed system is derived. The simulation analyzes the influence of transmitting radius, receiving aperture, beam divergence, zenith angle, and signal-to-noise ratio on the system's error performance, and compares it with OFDM modulated single input single output (SISO) and differential phase-shift keying-modulated SISO schemes. Finally, the experimental data are verified by the Monte Carlo method. This research provides a theoretical basis for research on MISO terrestrial-satellite laser communication uplink system coding technology.