Normandrejer2385

This work reveals the underlying physics of temperature influence on SPhPs and LSPhRs of SrTiO3 and helps explore its potential applications as photonic resonators at high temperatures.A scheme of quarter-overlapped microlens arrays (QOMLA) is proposed to improve the display performance of integral imaging (II). The theory and the design of QOMLA is presented by the combination of geometric optics and wave optics and is verified by the optical experiments. The angular sampling density of the II system can be doubled in each dimension to further increase the spatial resolution. Multiple central depth planes can be constructed by adjusting the spacing of the multilayers, so as to expand the depth of field (DoF). Furthermore, QOMLA is easier to process when compared with the single-layer microlens array, and it reduces processing costs.We demonstrate the DC-Kerr effect in plasma enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) and use it to demonstrate a third order nonlinear susceptibility, χ(3), as high as (6±0.58)×10-19m2/V2. learn more We employ spectral shift versus applied voltage measurements in a racetrack resonator as a tool to characterize the nonlinear susceptibilities of these films. In doing so, we demonstrate a χ(3) larger than that of silicon and argue that PECVD SRN can provide a versatile platform for employing optical phase shifters while maintaining a low thermal budget using a deposition technique readily available in CMOS process flows.Extending the optical communication wavelengths to 2 µm can significantly increase data capacity. Silicon photonics, which is a proven device integration technology, has made rapid progress at 2 µm recently. As a fundamental functional element in the photonic design kit, the 3 dB power splitter has been extensively studied in both the 1.55 µm and 2 µm regime. While the device is highly desirable to operate over both wave bands, the large waveguide dispersion in silicon makes it challenging. In this work, we demonstrate an ultra-broadband power splitter on silicon, which has a 0.2 dB bandwidth exceeding 520 nm from 1500 to 2020 nm according to simulations. The beam splitter is realized by a triple tapered Y-junction, and its operational bandwidth is greatly increased by subwavelength grating structure. The device has an ultra-compact footprint of only 3µm×2µm. Due to the limitations on the setup and coupling technique, we measure the device bandwidth in 1.55 µm and 2 µm wave bands. The device insertion loss is measured to be below 0.4 dB from 1500 to 1620 nm and from 1960 to 2020 nm, respectively. According to these results, the proposed device is believed to be capable of operating over a broadband from 1.55 µm and 2 µm wavelengths.Respiration and heartbeat monitoring during sleep is essential in the assessment of personal health. However, conventional monitoring systems are complex, expensive, and uncomfortable. In this Letter, a mat embedded with a macrobending optical fiber sensor is proposed for non-contact vital signs monitoring during sleep based on vibration sensing. Exploiting the whispering gallery mode, a small-core fiber is adopted and pre-bent to enhance sensitivity to subtle vibrations. The mat sensing system can simultaneously detect and track respiration and ballistocardiography. With high vibration sensitivity, high reliability, and good stability, the mat provides a non-contact and low-cost alternative for long-term monitoring of vital signs, especially for daily home use.We introduce a projection-type light field display featuring effective light modulation. By combining a tomographic display with integral imaging (InIm) technology, a novel optical design is capable of an autostereoscopic light field projector. Here, the tomographic approach generates a high-resolution volumetric scene, and InIm makes it possible for the volumetric scene to be reconstructed on a large screen through a projection. Since all the processes are realized optically without digital processing, our system can overcome the performance limitations associated with the number of pixels in the conventional InIm displays. We built a prototype display and demonstrated that our optical design has the potential of massive resolution with a full-parallax in a single device.Recently, large-scale photonic integrated circuits have seen rapid development. Optical switches are the elementary units used to realize optical routers and processors. However, the high static power and large footprint of silicon electro-optic and thermo-optic switches are becoming an obstacle for further scaling and high-density integration. In this Letter, we demonstrate a 2×2 nonvolatile silicon Mach-Zehnder optical switch enabled by low-loss phase change material Sb2S3. Changing the phase state of Sb2S3 can switch the optical transmission between the bar and cross paths. As no static power is required to maintain the phase state, it can find promising applications in optical switch matrices and reconfigurable optical circuits.Due to the beam cleanup effect, brightness enhancement (BE) can be achieved in a Raman fiber amplifier (RFA) based on multimode (MM) graded-index (GRIN) fiber. In this Letter, a novel, to the best of our knowledge, diagnostic tool of mode decomposition (MD) based on a stochastic parallel gradient descent algorithm is demonstrated to observe the beam cleanup effect in a GRIN-fiber-based RFA for the first time, to our knowledge. During output power boosting up to 405 W at 1130 nm, the output beam quality factor M2 improves from 3.45 to 2.88, with a BE factor of 10.5. The MD results based on the near-field beam profiles from RFA indicate that the modal weight of the fundamental mode increases from 74.5% to 87%, confirming that the fundamental mode dominates with higher Raman gain. Moreover, the beam quality is found to be limited by the existence of a higher-order (Laguerre-Gaussian) LG10 mode, which is insensitive to the beam cleanup effect. The correlation coefficient reaches over 0.98 for all MD results. Thus, the accuracy of the MD method is high enough to provide further valuable insight into the physics of spatiotemporal beam dynamics in MM GRIN fiber.Wavelength-tunable optical vortices with a topological charge equal to l=1 of orbital angular momentum (OAM) were experimentally realized using a single off-axis spiral phase mirror (OSPM) with lasers of various visible-light wavelengths. Using an OSPM designed for 561 nm and an incidence angle of 45°, circular doughnut-shaped l=1 optical vortices were obtained at 561, 473, and 660 nm by rotating the OSPM to modify the laser incidence angle. Wavelength-tunable l=1 optical vortices were obtained at the respective incidence angles of 45°, 53.4°, and 33.7°, because the effective geometrical thickness of the OSPM, which determines the order of OAM, was identical at each wavelength. This flexible OSPM which operates over a wide wavelength range will provide continuously wavelength-tunable optical vortices for applications in the fields of advanced optics and photonics in which optical vortices with wide wavelength tunability are in demand.Optical see-through head-mounted displays are actively developed in recent years. An appropriate method for mutual occlusion is essential to provide a decent user experience in many application scenarios of augmented reality. However, existing mutual occlusion methods fail to work well with a large field of view (FOV). In this Letter, we propose a double-parabolic-mirror structure that renders hard-edge occlusion within a wide FOV. The parabolic mirror increases the numerical aperture of the system significantly, and the usage of paired parabolic mirrors eliminates most optical aberrations. A liquid crystal on silicon device is introduced as the spatial light modulator for imaging a bright see-through view and rendering sharp occlusion patterns. A loop structure is built to eliminate vertical parallax. The system is designed to obtain a maximum monocular FOV of H114∘×V95∘ with hard-edge occlusion, and a FOV of H83.5∘×V53.1∘ is demonstrated with our bench-top prototype.We study the formation of spatially dependent electromagnetically induced transparency (EIT) patterns from pairs of Laguerre-Gauss (LG) modes in an ensemble of cold interacting Rydberg atoms. The EIT patterns can be generated when two-photon detuning does not compensate for the Rydberg level energy shift induced by van der Waals interaction. Depending on the topological numbers of each LG mode, we can pattern dark and bright Ferris-wheel-like structures in the absorption profile with tunable barriers between sites, providing confinement of Rydberg atoms in transverse direction while rendering them transparent to light at specific angular positions. We also show how the atomic density may affect the azimuthal modulation of the absorption profile.The ability to engineer the properties of quantum optical states is essential for quantum information processing applications. Here, we demonstrate tunable control of spatial correlations between photon pairs produced by spontaneous parametric down-conversion, and measure them using an electron multiplying charge coupled device (EMCCD) camera. By shaping the spatial pump beam profile in a type-I collinear configuration, we tailor the spatial structure of coincidences between photon pairs entangled in high dimensions without effect on intensity. The results highlight fundamental aspects of spatial coherence and hold potential for the development of quantum technologies based on high-dimensional spatial entanglement.Daytime use of Shack-Hartmann wavefront sensor (SHWS)-based adaptive optics (AO) at a telescope is hindered by the fluctuating bright sky background. Therefore, we propose a Gaussian modeling centroid extraction algorithm that performs real-time daylight AO closed-loop corrections. The algorithm is executed in the process of modeling and updating each pixel of the consecutive SHWS images. The simulation results show that our method can provide a lower centroid estimation error (CEE) for bright sky background conditions. We also performed a field experiment on a 2 m ground-based telescope and achieved a daylight AO correction of 2.1 times diffraction limit for a star with a visual magnitude of 4.7 (HIP113116) when the elevation angle of the sun was 7.7°. This represents the first publicly reported daylight natural guide star AO correction result on a 2 m class telescope.The electric-field-enhanced effect of permittivity can improve the performance of electro-optic modulators and deflectors. A theoretical model of super electro-optic modulation based on the field-enhanced effect of the permittivity was proposed. Results showed that a strong field-enhanced effect can greatly reduce the half-wave voltage and increase the modulation depth as a result of increased relative dielectric permittivity and permittivity gradient to the electric field. For bulk paraelectric KTNCu near the Curie temperature, we found a novel phenomenon that the response of relative dielectric permittivity to the bias electric field was closely related to the frequency, including attenuation, invariance, and enhancement. We effectively selected the frequencies corresponding to the strong field-enhanced effect by measuring the dielectric-frequency spectrum under the bias voltage. At these frequencies, a phase retardation of π was achieved through 2Vpp AC modulation voltage, indicating that the half-wave voltage was reduced by one order of magnitude.