Mcphersoncheek1484

A novel relative humidity (RH) sensor, based on an in-line microfiber interferometer (MFI), is proposed and demonstrated in an experiment. The microfiber interferometer is fabricated by tapering multi-core fiber down to the micrometer scale in diameter, and the coupling occurs between the center core mode and the multiple side core modes. To enhance the sensing performance, the microfiber sensor is fixed as U-shaped. The variation of RH is monitored by observing the wavelength shift of the transmission spectrum. The experimental results show that the sensor has a good linear response to RH. A thinner MFI diameter of 8.52 µm can offer a better RH sensitivity of 59.8 pm/(%RH) in the range of 35-95% RH. When temperature changes from 35°C to 85°C, the temperature sensitivity of the sensor is 4.2 pm/°C, which demonstrates that the sensor is insensitive to temperature. The simultaneous measurement of temperature and RH can be realized by cascading with fiber Bragg grating. The microfiber sensor is easy to fabricate and does not have any functional coating, which makes it widely used in accurate RH measuring.We design and theoretically investigate a surface-enhanced Raman scattering (SERS) sensor based on the hybrid plasmonic grating slot waveguide. The sensor is formed by combining a dielectric deep slot waveguide and a metallic grating slot waveguide. The proposed sensor exhibits a high field enhancement with a maximum enhancement factor of 7580.9 at the wavelength of 785 nm, revealing that the electric field in such hybrid plasmonic grating slot waveguide can be extremely strengthened. To better characterize the performance of the sensor in the SERS application, the total normalized volumetric enhancement factor (TNVEF) is proposed, which is determined by both the |E|4-approximation-based volumetric field enhancement and Raman scattered light collection efficiency. The TNVEF is utilized to characterize the influences of the structural parameters on the sensor and further optimize the sensing structure. Such on-chip SERS sensor can be integrated with a micro-laser and a micro-multiplexer on a photonic platform to realize an all-integrated on-chip SERS detection system.Self-mixing interferometry (SMI) is a reliable method that has been applied to measuring displacements, absolute distances, and velocities of remote targets. Evaluating the optical feedback factor C and the linewidth enhancement factor α is a vital step in calculating laser diode parameters and in processing SMI signals using phase unwrapping. This paper proposes an evaluation method for the optical feedback factor and the linewidth enhancement factor of arbitrary waveforms by investigating the slopes of phase discontinuity distribution in the optical feedback regime of 1 less then C. First of all, the effects that the slope of phase discontinuity distribution has on the prediction of the optical feedback factor and the linewidth enhancement factor are clarified. Next, an algorithm is proposed to evaluate the optical feedback factor and the linewidth enhancement factor using the slope variation of phase discontinuity distribution, along with a method to select discontinuities in order to improve measurement accuracy using the cumulative effect of discontinuity distribution. The proposed method is verified through simulations as well as experiments with a low-cost semiconductor laser.We fabricated a binary diffractive lens to control focal distribution, such as intensity distribution, by controlling the focal length and depth of focus. The results revealed changes in the focal length and depth of focus as a function of changes in the ring zone interval ΔRM at the end of the lens. Similar results were obtained from experiments. The peak position on the optical axis shifts further away from the lens. The half-width in the propagation direction increases with the ΔRM. These results demonstrate the possibility of controlling the focal distribution using single flat lenses by changing the periodic structure.In this experimental work we report our findings about a cascade (Ξ) transition 5S1/2→5P3/2→5D3/2 of both 85,87Rb atoms under different laser detuning combinations. The relative power levels of two individual lasers are adjusted under a counter-propagating configuration so that the system exhibits Autler-Townes splitting (ATS). However, the ATS, which is otherwise difficult to detect in a room-temperature alkali vapor cell offering large Doppler background, is well resolved here by using a combination of modulation transfer and phase-sensitive detection techniques. The results show that the AT components clearly indicate the hyperfine structure of 5D3/2 level for 87Rb isotope. this website For 85Rb, the resolution of ATS is limited by the relatively closer proximity of 5D3/2 hyperfine components. The results are also verified through blue fluorescence detection by monitoring the 5D3/2→6P3/2→5S1/2 non-degenerate decay arm. The technique is easy to implement and is able to reveal the hyperfine structure of the excited levels. However, the technique is not a good choice when an excited level with dense hyperfine structure is targeted.Model calibration is performed for an adaptive freeform surface interferometer (AFI). In view of the non-unique null configuration in AFI, the multi-null constraint (MNC) calibration method is proposed to address error coupling in the null configuration modeling. The final figure error of the tested surface can be extracted together with the coupling parameters. The performance of the MNC method is evaluated in simulations and experiments. The higher accuracy is proved after the MNC calibration. This calibration is preparation for the subsequent system instrumentation.In this paper, we propose and demonstrate a dual-channel self-calibration multimode optical-fiber surface plasmon resonance thermometer. The structure of this thermometer is mainly composed by dual sensing channels, in which one channel is coated with a gold layer surrounded by liquid crystal (LC), and the other is prepared with bilayers of silver and thin indium tin oxide (ITO) layer. The gold channel is the main channel, and the channel of the ITO layer with high refractive index is viewed as a configuration of self-calibration. The experimental results of the system show that the temperature sensitivities are 1.006 nm/°C in the range of 20°C-34°C and 0.058 nm/°C in the range of 35°C-80°C. In particular, at the phase transition temperature 34.5°C of changing from the nematic to the isotropic phase of the LC, the temperature sensitivity shows a step increase of 6.8 nm with a unit temperature change. This structure can be highly advantageous for temperature controlling and alarming in laboratory monitoring and industrial production.Photoacoustic computed tomography with compressed sensing (CS-PACT) is a commonly used imaging strategy for sparse-sampling PACT. However, it is very time-consuming because of the iterative process involved in the image reconstruction. In this paper, we present a graphics processing unit (GPU)-based parallel computation framework for total-variation-based CS-PACT and adapted into a custom-made PACT system. Specifically, five compute-intensive operators are extracted from the iteration algorithm and are redesigned for parallel performance on a GPU. We achieved an image reconstruction speed 24-31 times faster than the CPU performance. We performed in vivo experiments on human hands to verify the feasibility of our developed method.In this work we present what we believe is the first application of software-defined optoelectronics (SDO) for bidimensional optoacoustic tomography (OAT). The SDO concept refers to optoelectronic systems where the functionality associated with the conditioning and processing of optical and electrical signals are digitally implemented and controlled by software. This paradigm takes advantage of the flexibility of software-defined hardware platforms to develop adaptive instrumentation systems. We implement an OAT system based on a heterodyne interferometer in a Mach-Zehnder configuration and a commercial software-defined radio platform (SDR). Here the SDR serves as a function generator and oscilloscope, while at the same time providing perfect carrier synchronization between its transmitter and receiver in a coherent baseband modulator scheme. This carrier synchronization enables us to have much better phase recovery. We study the performance of the OAT SDO system using different bidimensional phantoms and carry out an analysis of the reconstructed images.Digital optical phase conjugation (DOPC) is a newly developed technique in wavefront shaping to control light propagation through complex media. Currently, DOPC has been demonstrated for the reconstruction of two- and three-dimensional targets and enabled important applications in many areas. Nevertheless, the reconstruction results are only phase conjugated to the original input targets. Herein, we demonstrate that DOPC could be further developed for creating structured light beams through a multimode fiber (MMF). By applying annular filtering in the virtual Fourier domain of the acquired speckle field, we realize the creation of the quasi-Bessel and donut beams through the MMF. In principle, arbitrary amplitude and/or phase circular symmetry filtering could be performed in the Fourier domain, thus generating the corresponding point spread functions. We expect that the reported technique can be useful for super-resolution endoscopic imaging and optical manipulation through MMFs.High-resolution, single-shot on-axis digital holography is proposed. Generally, an on-axis configuration samples carrier fringes with higher spatial resolution compared to an off-axis configuration. However, the reconstructed image is obtained with unnecessary images of a conjugate image and a zero-order beam. The proposed method uses a phase-modulated illumination beam and image processing to eliminate these unnecessary images. Since time-division and parallel phase-shifting methods are not required, the proposed method has higher temporal and spatial resolutions. During image processing, the conjugate image is removed by filtering on the Fresnel domain while keeping most of the information of the object image intact. The usefulness of the proposed method is confirmed by a numerical simulation and an optical experiment.A new luminance calculation method that accounts for mesopic vision and fog penetration ability is presented. This method aims to select a suitable light source for street lighting and is obtained using the mesopic luminance calculation and transmittance calculation methods at each individual wavelength. Additionally, the new method was evaluated using six LED light sources between 3500 and 6000 K. Overall, the calculation results indicate that suitable LEDs' CCT decreases with an increase of luminance for low transmittance rates. However, for high transmittance rates, high CCT LED lamps are the most suitable for street lighting. The recommended CCT of LED light sources for street lighting under different visibility and luminance conditions is presented.In this paper, a 1550 nm five-channel all-fiber homodyne laser Doppler vibrometer with high sensitivity and good signal probing probability is presented. Under the anechoic tank, standing on an airborne platform above the water surface 3 m away, the calibration experiments of the designed system are conducted. The minimum detectable sound pressure level is up to 101.73 dB re 1 µPa at 10 kHz under the hydrostatic water surface condition, and the time distribution of the final outputs are consistent with that of the underwater sound transducer. For the hydrodynamic detection capability, with the help of a 1064 nm high-pulse-energy laser whose pulse energy is 6J, pulse duration is about 8 ns, and repetition rate is 1 Hz, the system performance is tested in Qiandao Lake. And the signal probing probability of the whole sensing system is up to 59.77%.