Foleymontgomery4431

In this investigation, we describe a spectrally resolved polarizing interferometer to modify the typical spectrally resolved interferometer based on the Fourier method, which has a dead zone caused by the minimum measurable range. By use of a polarization pixelated CMOS camera, which enables us to obtain spatially phase-shifted spectral interferograms, the spectral phase can be extracted with a single image, and the proposed interferometer can obtain a line profile of a specimen at once. By the nature of phase-shifting technique, moreover, the directions of the measured distances can be identified, and the measuring range is extended to twice that of the typical spectrally resolved interferometer. In the experimental results, the measuring range was 104 µm, and the capability to obtain a line profile of a specimen with a single image was confirmed. For 3D surface profiling, lateral scanning was adopted, and the measurement results were compared with the result of the Fourier method.Brillouin-shift (B-S) fluctuations in multiwavelength Brillouin Raman erbium-doped fiber laser generation are investigated to obtain a probability distribution of acoustic-phonon speeds in the crystal lattice of a dispersion-compensating fiber (DCF) in a linear cavity. Even though the available B-S line spacing can be at 0.076 and 0.08 nm when Raman pump (RP) power is zero or 76 mW, the other B-S possibilities are obvious, especially at RP power 257 mW. A crystal effective mass participating in the crystal vibration is obtained 8937, 8943, 8954, and 12,106 times the electron rest mass by fitting a general form of a Boltzmann density function and the resulting most probable speed of 5445 m/s at a fixed Brillouin pump power of 6.5 dBm and RP powers of 0, 76, 163, and 257 mW, respectively. Finally, an uncertainty in the crystal dimension is also estimated by Heisenberg's uncertainty principle.In recent years, the investigations of lasers based on group IV material have been limited by the low quality (Q) factor of the resonant modes. With the improvement of the optical bound states in the continuum (BICs) in various dielectric systems, we propose a novel design that takes advantages of both the direct bandgap dielectric material GeSn and the BIC phenomenon. In addition to the demonstration of the unprecedented high-Q factors (i.e., ∼1010) that improve the emission process, the vertical symmetry broken structure can emit light at the wavelength of 1870 nm with higher luminous intensity (i.e., ∼24). The modulation effect of the material and geometric parameters on the Q value and the luminous intensity of the structure are also demonstrated. Our investigations provide useful guidelines for potential applications such as on-chip light sources in group IV photonics and optical communications.Acoustic resolution photoacoustic microscopy (ARPAM) is a promising imaging tool in biomedical applications for its advantage of penetration over other optical imaging techniques. However, the lateral resolution of ARPAM deteriorates significantly in the out-of-focus region. The synthetic aperture focusing technique (SAFT) is required to restore this kind of focus-related imaging distortion. The conventional SAFT method is based on the virtual detector (VD) conception, in which the phase of the received photoacoustic (PA) signal is calculated by assuming the focus of the transducer as a VD. Nevertheless, the phase of the received PA signal is not only determined by the geometrical parameters of the transducer, but also by the transducer's electromechanic response and the original PA signal. Ignoring these two factors will reduce the quality of the imaging results. In this work, a new SAFT method, which is based on acoustic simulation, is proposed for ARPAM. The measured PA signal from a point target at the focus is employed to evaluate the convolution of the transducer's electromechanic response and the original PA signal. This measured signal is used as the excitation in an acoustic simulation. The simulation, which is based on the geometrical and acoustic parameters of the transducer, is employed to calculate the delay time and weighted coefficient for the SAFT calculation. The phantom experiments with point and line targets indicate that the proposed method obtains imaging results with better lateral resolution and improved signal-noise ratio compared with the widely used VD-based SAFT method.A scheme to enhance the optical delay in Rydberg atoms is proposed. In the linear case, the optical delay in a four-level system can be significantly enhanced compared to that of the three-level system. However, the width of the transparent window will decrease with an increase in the optical delay. In the nonlinear case, the nonlinear dispersion becomes steep around the transparency window. The enhanced cross-Kerr nonlinearity mainly contributes to the effective dispersion, which dramatically increases the optical delay. The simulation result shows that the optical delay of the system could be enhanced tens of times; moreover, the wide transparency window remains. So the delay-bandwidth product could be significantly improved due to nonlinear dispersion. We further examine Gaussian pulse propagation in the Rydberg atoms.We report on the experimental observation of the diffraction pattern formed in the far-field region when a high-power continuous-wave laser convergent or divergent Gaussian beam passes through a cuvette with ferrofluid. Two different types of diffraction rings with opposite light-intensity distribution are shown in the far field. The difference between the diffractive patterns is attributed to the interaction of the strong spatial self-phase modulation caused by the refractive index change of the medium with wavefront curvature of the input Gaussian beam. Fenretinide The observed behavior of the diffraction pattern dynamics is interpreted theoretically based on the Fresnel-Kirchhoff integral. The negative polarity of nonlinear refraction can be identified by the central interference profiles and the diffraction pattern. At the same time, the self-defocusing phenomena of the ferrofluid can be determined by the type of pattern. The nonlinear refraction coefficients of the ferrofluid were estimated to be ∼-2.89×10-5cm2/W (convergent Gaussian beam) and ∼-3.