Mcclurestewart1167

A novel configuration of a Fourier domain mode locked (FDML) laser based on silicon photonics platform is presented in this work that exploits the narrowband reflection spectrum of a photonic crystal (PhC) cavity resonator. Configured as a linear Fabry-Perot laser, forward biasing of a p-n junction on the PhC cavity allowed for thermal tuning of the spectrum. The modulation frequency applied to the reflector equalled the inverse roundtrip time of the long cavity resulting in stable FDML operation over the swept wavelength range. An interferometric phase measurement measured the sweeping instantaneous frequency of the laser. The silicon photonics platform has potential for very compact implementation, and the electro-optic modulation method opens the possibility of modulation speeds far beyond those of mechanical filters.The state of the art terahertz-frequency quantum cascade lasers have opened a plethora of applications over the past two decades by testing several designs up to the very limit of operating temperature, optical power and lasing frequency performance. The temperature degradation mechanisms have long been under the debate for limiting the operation up to 210 K in pulsed operation in the GaAs/AlGaAs material system. In this work, we review the existing designs and exploit two main temperature degradation mechanisms by presenting a design in which they both prove beneficial to the lasing operation by dual pumping and dual extracting lasing levels. We have applied the density matrix transport model to select potential candidate structures by simulating over two million active region designs. We present several designs which offer better performance than the current record structure.Early detection of a gas kick is crucial for preventing uncontrolled blowout that could cause loss of life, loss of assets, and environmental damage. Multiphase flow experiments conducted in this research demonstrate the capability of downhole fiber optic sensors to detect a potential gas influx in real-time in a 5000 ft deep wellbore. Gas rise velocities estimated independently using fiber optic distributed acoustic sensor (DAS), distributed temperature sensor (DTS), downhole gauges, surface measurements, and multiphase flow correlations show good agreement in each case, demonstrating reliability in the assessment. Real-time data visualization was implemented on a secure cloud-based platform to improve computational efficiency. This study provides novel insights on the effect of circulation rates, gas kick volumes, backpressure, and injection methods on gas rise dynamics in a full-scale wellbore.Fourier transform infrared (FTIR) spectroscopy is a powerful technique in analytical chemistry. Typically, spatially distributed spectra of the substance of interest are conducted simultaneously using FTIR spectrometers equipped with array detectors. Scanning-based methods such as near-field FTIR spectroscopy, on the other hand, are a promising alternative providing higher spatial resolution. However, serial recording severely limits their application due to the long acquisition times involved and the resulting stability issues. We demonstrate that it is possible to significantly reduce the measurement time of scanning methods by applying the mathematical technique of low-rank matrix reconstruction. Data from a previous pilot study of Leishmania strains are analyzed by randomly selecting 5% of the interferometer samples. The results obtained for bioanalytical fingerprinting using the proposed approach are shown to be essentially the same as those obtained from the full set of data. This finding can significantly foster the practical applicability of high-resolution serial scanning techniques in analytical chemistry and is also expected to improve other applications of FTIR spectroscopy and spectromicroscopy.Here, we describe in detail a procedure for the numerical design of planar focusing mirrors based on monolithic high contrast gratings. We put a special emphasis on the reconstruction of the hyperbolic phase of these mirrors and we conclude that the phase does not have to be perfectly mimicked to obtain a focusing reflector. We consider here the grating mirrors that focus light not in the air but in the GaAs substrate and we compare them with conventional parabolic reflectors of corresponding dimensions. The light intensity at the focal point of the focusing grating mirrors was found to be comparable to that of the parabolic reflector. Moreover, the reflectivity of the focusing grating mirrors is almost as high as that of parabolic mirrors covered with an additional reflecting structure, if the ratio of the reflector width to the focal length is less than 0.6. Planar focusing grating mirrors offer a good alternative to parabolic mirrors, especially considering the complexity of fabricating three-dimensional structures compared to planar structures.We investigated the roughness-induced scattering loss (LossR) of small-core polymer waveguides fabricated using the photolithography method, both theoretically and experimentally. The dependence of LossR on the roughness parameter, waveguide dimension, operation wavelength, refractive index difference and distribution, polarization sensitivity, sidewall angle, and bending radius were studied. https://www.selleckchem.com/products/pf-2545920.html The surface roughness of both the sidewall and the top/bottom of the fabricated waveguides were measured using laser confocal microscope, and the results showed that the averaged sidewall roughness was approximately 60 nm, which is 3 times that of the top/bottom surface. As a result, the sidewall roughness-induced LossR is 9 times that induced by the top/bottom roughness. The calculated value of LossR agrees well with the measured value. LossR increases rapidly with the decrease in the waveguide width, especially when the waveguide width is reduced below 10 µm, at which the LossR is approximately 0.3 dB/cm. On the other hand, the dependence of LossR on the waveguide height is negligible. Our results provide guidance for developing single-mode polymer waveguides with low loss for optical interconnect applications.Optical needles with central zero-intensity points have attracted much attention in the field of 3D super-resolution microscopy, optical lithography, optical storage and Raman spectroscopy. Nevertheless, most of the studies create few types of optical needles with central zero-intensity points based on the theory and intuition with time-consuming parameter sweeping and complex pre-select of parameters. Here, we report on the inverse design of optical needles with central zero-intensity points by dipole-based artificial neural networks (DANNs), permitting the creation of needles which are close to specific length and amplitude. The resolution of these optical needles with central zero-intensity points is close to axial diffraction limit (∼1λ). Additionally, the DANNs can realize the inverse design of several types on-axis distributions, such as optical needles and multifocal distributions.