Lundqvistallison6677

Preliminary results suggest that leaks giving rise to methane concentrations of the order of 500 ppm-m can be effectively detected-sensitivity similar to current satellites with more continuous temporal coverage and areal coverage of the order of 100s of km2 for relatively low cost. We outline a method of using an array of LHRs to localize the leak using lineshape information and tomographic reconstruction techniques that will be tested in future work.Multichannel imaging systems consist of multiple channels that have different imaging characteristics (fields-of-view and angular resolutions). We design and demonstrate a six-channel multiresolution imaging system that can achieve a relative magnification ratio of up to 10 times between the channels and at the same time result in different depths-of-field. The imaging system consists of two double-sided lens arrays made of PMMA material, a baffle to eliminate possible cross talk between neighboring channels, and a Sony full-frame image sensor. The imaging system was tested by capturing images of stationary and moving objects. The acquired images exhibit different resolutions, fields-of-view, and levels of blur proving our concept.We propose, to the best of our knowledge, a novel kind of tunable liquid crystal core refractive index (RI) sensor based on photonic crystal fiber (PCF) covered with a nanoring gold film. The finite element method is used to discuss and analyze the sensing performance of the RI sensor. Gold is used as the excitation material for surface plasmon resonance, and a gold nanoring is embedded around the first cladding of the PCF. The liquid analytes penetrate the outermost layer of the cladding, and the central hole is filled with liquid crystal E7. Complete coupling and incomplete coupling are excited as the analyte RI increases, and the resonance strength of complete coupling is stronger than that of incomplete coupling. It can be proved by calculation that at different wavelengths, resonant coupling of fifth-order and sixth-order surface plasmon polaritons is obtained. The RI of liquid analytes ranges from 1.405 to 1.445. The diameters of the liquid crystal cores are 0.2, 0.4, 0.6, and 0.8 µm; their average sensitivities are 10700, 10566, 10167, and 9166 nm/RIU; and the linear fitting constants are 0.98025, 0.97387, 0.96597, and 0.95507, respectively. In short, the RI sensor has the advantages of tunability, wide range, and high sensitivity, and is expected to be applied in various fields.A novel frequency-domain image processing method is proposed, to the best of our knowledge, to filter the noise from data collected by distributed optical fiber sensors based on Brillouin optical time-domain sensing (BOTDS). In the proposed method, we first divide a data image into subimages, and then we filter the noisy subimages by retaining the useful frequency information corresponding to the Lorentz-shape frequency spectrum and Brillouin frequency shift (BFS) transitions. The denoising performance improvements are verified by simulation and experiment. learn more The performances in terms of temperature/strain measurement uncertainty, spatial resolution, and processing time achieved by the proposed filter are then compared with those by using a Gaussian filter and a nonlocal means (NLM) filter. In a proof-of-concept experiment with a 5.2 km length G657 sensing fiber, we achieve a temperature measurement uncertainty improvement of 27% compared with the results obtained by using the Gaussian filtering method. Furthermore, the processing speed of the proposed method is 22 times faster than that of the NLM filter under the same temperature measurement uncertainty.The damage of large-aperture optical components caused by organic contamination limits the performance improvement of high-power laser facilities. We propose an in situ plasma cleaning technology to remove the organic contaminants on large-aperture optical components, demonstrated by the simulated equipment. The cleaning characteristics of the equipment were investigated by spectral diagnosis. The cleaning capability coefficient was defined to evaluate the performance of the plasma equipment. Then diffusion properties of reactive species along the surface of optical components were elucidated under various charge parameters, including powers, source frequencies, and gas pressures. We discuss the underlying cleaning mechanism for removing organic contaminants. A new plasma cleaning model is established to predict the treatment time with the cleaning capability coefficient.This publisher's note serves to correct Appl. Opt.61, 1552 (2022)APOPAI0003-693510.1364/AO.452140.An analysis of the Mach-Zehnder modulator's chirp factor α versus DC bias is presented. Unlike the well-known belief that α is infinite at 0 and π biases, it is shown that α can be zero at these biases under a careful balance of the modulations in the two modulator arms. Derivation of the condition to achieve this effect is given, and practical verifications are presented, where an excellent agreement with the theory is obtained. It is shown that modulators with a low residual chirp over a wide range of DC bias are achieved by designing the RF driving such that α would be minimized at zero bias instead of at quadrature bias as used currently in the modulator design.It is well known that semiconductor lasers under optical injection present rich, dynamic behavior. In this paper, we focus on pulsing regimes, which can be either exploited in a broad variety of applications or lead to undesired instabilities. In particular, we develop a multi-metric method to automatically identify pulsing regimes in the parameter space. We apply this method to extensive numerical simulations to show that these regimes occur in the vicinity of the static synchronization boundary. Furthermore, analyzing these pulsing regimes, we identify pulsations with repetition rates ranging from several megahertz up to more than 1 GHz. Finally, we analyze the effect of the linewidth enhancement factor and the slave-laser bias current, revealing that a linewidth enhancement factor of 3 and a higher bias current lead to broader regions of pulsation regimes.Midinfrared (MIR) optical frequency combs are of great significance as broadband coherent light sources used in extensive areas such as coherent communications and molecule detections. Conventional MIR combs are usually restricted in size and power, while most microcombs are focused in the near-infrared (NIR) region because of the limited accessible Q-factor of microrings and the poor performances of available pumps. In this paper, we numerically demonstrate the simultaneous generation of a broadband MIR and NIR comb in a GaP microring with an additive waveguide. The achieved octave-spanning (1890-4050 nm) MIR microcomb at a low pump power of 34 mW can be effectively converted to the second-harmonic NIR comb covering 1120-1520 nm with separate dispersion optimization of the ring cavity and straight waveguide. The proposed system has the advantage of simple structure and low power threshold, which could find potential in highly integrated MIR optical sources and related applications.This study reports a new, to the best of our knowledge, view registration method that can achieve high-quality tomographic reconstruction in spite of a large view registration (VR) error. The correlation-based view registration (CBVR) method is a directional orientation modification method based on the cross-correlation between measured projections and ray-tracings generated from the reconstruction, which can reduce the gross VR error to moderate levels by iterations. In the CBVR method, a traditional multi-camera VR process is first performed, based on the sensitivity of the projections to the VR error, and are evaluated and quantified for all cameras. Afterward, the orientation of each camera is iteratively updated based on the cross-correlation of the measured projections and the ray-tracings generated from the reconstruction calculated through all other cameras. The CBVR is consecutively validated by numerical and experimental studies. Through a numerical study on a controlled phantom introduced with 2% Gaussian noise, the CBVR method is proved to be able to reduce the large VR error (up to 4.8°) to 0.2° as well as to reduce the reconstruction error to ∼6.7% in 12 rounds of iterations, which is very close to that obtained without any VR error (6% caused by Gaussian noise only). The CBVR method is then demonstrated and validated by reconstructing a two-branch laminar flame. By implementing the method, the initial projection orientations are optimized from traditional multi-camera VR results within a range of ±3∘, leading to effectively improved tomographic reconstruction of flame chemiluminescence distribution.A physical model is demonstrated to optimize narrow-linewidth distributed feedback lasers based on apodized laterally coupled gratings (AG-DFB). The structure can effectively suppress the longitudinal spatial hole burning as well as remove the regrowth process during fabrication by using the apodized grating geometry. The studies include numerical simulations of the AG-DFB laser for its static and dynamic behaviors at different cavity lengths and facet coating conditions. The results show that the proposed device can achieve narrow linewidth, high slope efficiency, and broad modulation bandwidth, as compared to λ/4 phase-shifted DFB lasers.Diffraction gratings with high upward diffraction efficiency and large effective length are required for chip-scale light detection and ranging. We propose a diffraction grating based on a multilayer silicon nitride waveguide, which theoretically achieves an upward diffraction efficiency of 92%, a near-field effective length of 376 µm, and a far-field divergence angle of 0.105° at a wavelength of 850 nm. The diffraction grating has a high tolerance to process variations based on Monte Carlo analysis. When the conditions are ±5% layer thickness variation, ±50nm lithographic variation, and ±20nm wavelength drift, more than 71% of the grating samples have a diffraction efficiency higher than 80%, and 100% of the samples have an effective length larger than 200 µm (corresponding to a far-field divergence less then 0.2∘). Furthermore, the near-field effective length of the grating with an upward diffraction efficiency above 90% can be adjusted from hundreds of microns to centimeters by changing the etching layer thickness and the grating duty cycle. This diffraction grating has a potential application in optical sensing and imaging from visible to near-IR wavelengths.An all-fiber Mach-Zehnder interferometer (MZI) using ring core few-mode fiber (RC-FMF) for curvature sensing is proposed and experimentally demonstrated. The MZI was fabricated by splicing a segment of RC-FMF between two pieces of single-mode fiber (SMF). With the benefit of a RC of the central axis of the RC-FMF, the sensor is more sensitive to curvature compared to other fiber sensors based on ordinary SMF or FMF. Curvature measurement can be achieved by monitoring the wavelength shift of interference dips. Experimental results have shown that the sensitivity of curvature sensing can reach up to -4.370nm/m-1, within the range of 1.199-1.549m-1. Also, the temperature sensing characteristics of the sensor are measured, and the maximum temperature sensitivity is 57.6 pm/°C, ranging from 25°C to 45°C. The proposed MZI sensor has excellent potential for curvature measurement of building structural health monitoring, bridge engineering, and more.