Garrisonbjerregaard4845

An adhesive-free encapsulation sapphire Fabry-Perot interferometer (FPI) is proposed and demonstrated for high-temperature pressure measurements. The sapphire FPI sensor is packaged by zirconia ferrules and a zirconia sleeve, which is easy to be configured and low in cost. Owing to this packaging technology, the sapphire FPI sensor presents good stability and high temperature resistance. The pressure and temperature properties of the sapphire FPI sensor are investigated within a temperature range from -50∘C to 1200°C and a pressure range from 0.4 to 4.0 MPa. Experimental results show the FPI has a temperature sensitivity of 23 pm/°C and still works as the temperature is up to 1200°C. Meanwhile, the wavelength shift of the sapphire FPI versus the applied pressure is linear at each tested temperature. The pressure sensitivity is measured to be 1.20 nm/MPa at 1200°C, and the linear response shows the proposed sensor has good repeatability within 0.4-4.0 MPa. Such a sapphire FPI sensor has potential applications in engineering areas, such as the oil industry and gas boilers.In this paper, a depth-related uniform multiple wavefront recording plane (UM-WRP) method is proposed for enhancing the image quality of point cloud-based holograms. Conventional multiple WRP methods, based on full-color computer-generated holograms, experience a color uniformity problem caused by intensity distributions. To solve this problem, the proposed method generates depth-related WRPs to enhance color uniformity, thereby accelerating hologram generation using a uniform active area. The aim is to calculate depth-related WRPs with designed active area sizes that then propagate to the hologram. Compared with conventional multiple WRP methods, reconstructed images have significantly improved quality, as confirmed by numerical simulations and optical experiments.We study femtosecond-laser-induced flows of air at a water/air interface, at micrometer length scales. To visualize the flow velocity field, we simultaneously induce two flow fronts using two adjacent laser pump spots. Where the flows meet, a stationary shockwave is produced, the length of which is a measure of the local flow velocity at a given radial position. By changing the distance between the spots using a spatial light modulator, we map out the flow velocity around the pump spots. We find gas front velocities near the speed of sound in air vs for two laser excitation energies. We find an energy scaling that is inconsistent with the Sedov-Taylor model. Due to the flexibility offered by spatial beam shaping, our method can be applied to study subsonic laser-induced gas flow fronts in more complicated geometries.Computer vision camera calibration is widely performed using parallel circles. Various cases of two coplanar circles are algebraically explained, proving that the common pole is located at the line at infinity for all relative positions, and the corresponding polar passes through the centers of the two circles. The two common poles of the two coplanar circles are the points at infinity when concentric; one common pole of the two coplanar circles is a point at infinity when nonconcentric. Accordingly, the vanishing line can be obtained by using the common pole-polar properties of two groups of two coplanar circles, and the camera's intrinsic parameters are solved according to the constraints between the image of the circular points and the imaged absolute conic. The camera calibration can be solved using only three images of two coplanar circles. Simulation and experiments verify that the proposed algorithms are effective.A generalized shift-rotation absolute measurement method for optical surface shapes with polygonal apertures based on migration recognition by Radon transform is proposed. https://www.selleckchem.com/products/blasticidin-s-hcl.html The rotation angles and translation distances of the test surface, measured three times, are calculated through migration recognition. The absolute shape of the test surface with the polygonal aperture is fitted by orthogonal Zernike polynomials. Compared to the existing absolute measurement method for polygonal apertures, our method ensures test surface measurement accuracy without high-precision attitude control and repeated adjustments. The measurement is simple and coherent, which reduces the measurement time and improves the efficiency.Adaptive optics (AO) correction based on pyramid wavefront sensors (P-WFSs) has been successfully implemented in several instruments for astronomical observation due to the P-WFS advantages in terms of sensitivity with respect to other WFSs, such as the Shack-Hartmann. The correction of non-common path aberrations (NCPAs) between the sensing and the scientific arm, commonly performed introducing offsets to the Zernike coefficients of the measured wavefront in the AO closed loop, reduces the sensitivity of P-WFSs causing a loss in sky coverage and scientific throughput. We propose a technique to exploit the full capabilities of P-WFSs compensating the NCPAs up to the fourth order on the WFS channel by means of a multi-actuator adaptive lens (MAL). We show the preliminary results obtained in a dedicated laboratory test bench.We propose a 3D full-field focusing method for microscopic mid-wave infrared (MWIR) imagery. The method is based on the experimental estimation of a confined volumetric vision microscope point spread function. The technique employs our well-known constant-range-based nonuniformity correction algorithm as a preprocessing step and then an iteration in the z-axis Fourier-based deconvolution. The technique's ability to compensate for localized blur is demonstrated using two different real MWIR microscopic video sequences, captured from two microscopic living organisms using a Janos-Sofradir MWIR microscopy setup. The performance of the proposed algorithm is assessed on real and simulated noisy infrared data by computing the root-mean-square error and the roughness Laplacian pattern indexes, which are specifically developed for the present work.Here we present a cost-effective multichannel optomechanical switch and software proportional-integral-derivative (PID) controller system for locking multiple lasers to a single-channel commercial wavemeter. The switch is based on a rotating cylinder that selectively transmits one laser beam at a time to the wavemeter. The wavelength is read by the computer, and an error signal is output to the lasers to correct wavelength drifts every millisecond. We use this system to stabilize 740 nm (subsequently frequency doubled to 370 nm), 399 nm, and 935 nm lasers for trapping and cooling different isotopes of a Yb+ ion. We characterize the frequency stability of the three lasers by using a second, more precise, commercial wavemeter. We also characterize the absolute frequency stability of the 740 nm laser using the fluorescence drift rate of a trapped 174Yb+ ion. For the 740 nm laser we demonstrate an Allan deviation σy of 3×10-10 (at 20 s integration time), equivalent to sub-200 kHz stability.The scattering effect occurring when light passes through inhomogeneous-refractive-index media such as atmosphere or biological tissues will scramble the light wavefront into speckles and impede optical imaging. Wavefront shaping is an emerging technique for imaging through scattering media that works by addressing correction of the disturbed wavefront. In addition to the phase and amplitude, the polarization of the output scattered light will also become spatially randomized in some cases. The recovered image quality and fidelity benefit from correcting as much distortion of the scattered light as possible. Liquid-crystal spatial light modulators (LC-SLMs) are widely used in the wavefront shaping technique, since they can provide a great number of controlled modes and thereby high-precision wavefront correction. However, due to the working principle of LC-SLMs, the wavefront correction is restricted to only one certain linear polarization state, resulting in retrieved image information in only the right polarization, while the information in the orthogonal polarization is lost. In this paper, we describe a full-polarization wavefront correction system for shaping the scattered light wavefront in two orthogonal polarizations with a single LC-SLM. The light speckles in both polarizations are corrected for retrieval of the full polarization information and faithful images of objects. As demonstrated in the experiments, the focusing intensity can be increased by full-polarization wavefront correction, images of objects in arbitrary polarization states can be retrieved, and the polarization state of the object's light can also be recognized.We investigated whether PrYAlO3 and PrY3Al5O12 (YAG) can work as gain media for high-power visible lasers and replace trivalent praseodymium (Pr)-doped fluoride crystals, with particular focus on thermal loading resistivity. PrYAlO3 exhibits a high laser gain at 747 nm, and we obtained a maximum output power of 1.2 W and a slope efficiency of 26.7% with high-power GaN laser diode pumping. Excited state absorption and large phonon energy hinder laser oscillation of PrYAG at room temperature. We obtained 616 nm laser oscillation of PrYAG at 40 K. Furthermore, we achieved a visible laser with PrYAG ceramics for the first time. The maximum output power is ∼30mW with a slope efficiency of ∼0.7%.We report an enhancement in the corner frequency of an optically trapped non-magnetic microsphere in the plane perpendicular to the laser propagation direction on addition of ferrofluid to the suspension medium. We conjecture that a directed motion of the nanoparticles toward the trap in this plane is responsible for the augmentation. Changes in the corner frequency in the presence of external magnetic field gradients lend credence to this conjecture. Corner frequency augmentation is also observed when zinc oxide nanoparticles are used. Here, however, no further changes are seen in the presence of magnetic field gradients.A surface plasmon resonance (SPR) temperature sensor based on a photonic crystal fiber (PCF) filled with silver nanowires is proposed in this paper. We inject ethanol solution filled with silver nanowires into the grapefruit PCF to realize temperature sensing. The sensitivity of the sensor can reach -433pm/∘C by numerical simulation, and the experimental result is -160pm/∘C. Simulations and experiments show that the wavelength of the resonance peak will blueshift with the invalidity of silver nanowires, and the resonance effect of the sensor will weaken. It can provide reference for the realization and application of other SPR sensors based on PCF.Polarized light absorption in photoalignment material induces anisotropic long-range interactions that orient liquid crystals. The main physical mechanisms behind anisotropic interactions are photocrosslinking and photodestruction of polymers, and photoisomerization and photorotation of azo dyes. Investigation of AtA-2 azo dye azimuthal anchoring versus exposure dose revealed the presence of an unusually strong anchoring peak at low doses, which is beyond our understanding of the known mechanisms. Here we explain these observations and demonstrate the existence of a photoalignment mechanism based on photoinduced hole dipole moments in the azo dye layer. Strong azimuthal anchoring energy >2×10-4J/m2 is obtained with a less then 0.5J/cm2 exposure dose.