Mccaincraft5430

With the availability of high-power (milliwatts) single-mode tunable laser sources that operate at room temperature across the infrared (IR) region, tunable laser spectrometers have seen an explosion of growth in applications that include commercial, Earth and planetary science, and medical and industrial sensing. CX5461 While the laser sources themselves have shown steady improvement, the detection architecture of using a single-element detector at one end of a multipass cell has remained unchanged over the last few decades. We present here an innovative new approach using a detector array coupled to an IR-transmissive mirror to image all or part of the multipass spot pattern of the far mirror and record spectra for each pixel. This novel approach offers improved sensitivity, increased dynamic range, laser power normalization, contaminant subtraction, resilience to misalignment, and reduces the instrument power requirement by avoiding the need for "fringe-wash" heaters. With many tens of pixels representing each spot during the laser spectral scan, intensity and optical fringe amplitude and phase information are recorded. This allows selection and manipulation (e.g., co-addition, subtraction) of the pixel output spectra to minimize optical interference fringes thereby increasing sensitivity. We demonstrate a factor of ∼20 sensitivity improvement over traditional single-element detection. Dynamic range increase of a factor of ∼100 is also demonstrated through spot selection representing different pathlengths. Additionally, subtracting the spectrum of the first spot from that of the higher pass normalizes the laser power and removes the contribution of contaminant gas and fringes in the fore-optics region. These initial results show that this imaging method is particularly advantageous for multi-channel laser spectrometers, and, once the image field is analyzed, pixel selection can be used to minimize data rate and volume collection requirements. This technique could be beneficial to enhanced-cavity detection schemes.We developed a high-power amplified spontaneous emission (ASE)-free fast wavelength-switchable external cavity diode laser (ECDL) using a digital micromirror device (DMD) as the wavelength selector. Generally, with a conventional fast wavelength-switchable ECDL with a DMD, the output power is limited by the damage threshold of the DMD. However, with our ECDL, a high-power output was realized by optimizing the beam focus on the DMD. In addition, an ASE-free stable output was realized through the introduction of a ring cavity. As a result, we successfully developed a fast wavelength-switchable ECDL realizing a high-power ASE-free output of over 300 mW.We investigate theoretically and numerically one-dimensional three-periodic photonic crystals of the structure [(SiO2/TiO2)N(Al2O3/ZrO2)M]K, formed by dielectric oxides SiO2, TiO2, Al2O3, and ZrO2 (N and M are the number of subperiods, and K is the number of superperiods). We study the transmission spectra, energy and power fluxes of TE- and TM-polarized electromagnetic waves for a photonic crystal, characterized by the sharp PBG edges, and narrow and pronounced peaks of defect modes. The angular distance (difference in the incidence angles) between the transmission peaks of different polarizations is shown to be about 1.5°, which is 5 times more than in the ternary photonic crystals. The results can be useful for designing highly efficient optical devices operating in the infrared regime on the side-surface of the photonic crystal, such as polarization-sensitive couplers and angle sensors for optical fiber systems.This paper presents an optimization-based method for phase extraction from interferograms corrupted with noise, rapid phase variations, and localized amplitude fluctuations. In the proposed method, the phase retrieval problem is addresed by modeling a cost function using non-convex non-smooth total generalized variational regularization. Further, the surrogate principle is used to transform the cost function into convex form for convenient optimization framework. Simulation results demonstrate the performance of the method. We also show the experimental utility of the proposed method for onion cell imaging using digital holographic microscopy.The optoelectronic oscillator (OEO) generates low-phase noise and high-frequency microwave signals thanks to a high Q-factor cavity with long and low-loss fiber delay. Traditionally, for the desired mode selection from the ultradense cavity modes, a narrowband electrical filter is needed, whose frequency tuning is very limited. On the other hand, for a tunable OEO offered by a microwave photonic filter (MPF), a paradox existed between the large number of cavity modes and the wide MPF bandwidth. Here, we achieve a tunable OEO using the mode-selection mechanism of parity-time symmetry, which overcomes the paradox. A high Q-factor silicon nitride microdisk resonator (Si3N4 MDR) is introduced to achieve frequency filtering and tuning. Moreover, the experimental results reveal that the tunable OEO generates a signal range from 3 GHz to 20 GHz with a phase noise about -120dBc/Hz at a 10 kHz offset frequency.A rapid and label free aflatoxin B1 (AFB1) microfluid sensor was proposed and tested. The device was fabricated with hollow-core photonics crystal fiber infiltrated with the AFB1 solution. The autofluorescence emitting from the AFB1 molecules was detected. The sensor length was optimized. The AFB1 concentration was tested with a 4 cm long sensor. The best limit of detection was achieved as low as 1.34 ng/ml, which meets the test requirement of the national standards for AFB1 in food. The effectiveness of this sensor being applied in beer solution was also verified to be a little more sensitive than in aqueous solution. Compared with traditional AFB1 detection methods, the proposed single-ended device perfectly satisfies the demand of process control in alcoholic beverages manufacture.Multi-wavelength radiometric thermometry has a wide application prospect in many fields. However, due to unknown emissivity, the data processing algorithm remains a difficult problem. The Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm is proposed to inverse true temperature and spectral emissivity without assuming the emissivity model. The BFGS algorithm can automatically identify the emissivity models of different trends. These simulation results show that given different initial emissivity has no significant influence on the inverse temperature and emissivity. Then, we select 0.5 as the initial emissivity and carry out the simulation experiments at 800 and 900 K, respectively. The maximum absolute error of temperature is less than 3.5 K and the computation time is less than 0.2 s. Thus, the algorithm has high precision and efficiency. Finally, the verification experiment indicates that the BFGS algorithm is effective and reliable. The proposed method can be applied to real-time temperature measurement in many industrial processes.Debye series expansion (DSE) is developed for electromagnetic (light) scattering by a charged sphere. By comparing our results with Mie theory (for a charged sphere) and with DSE (for a neutral sphere), we verify our theory numerically. DSE is employed for calculation of far-field intensity, and absorption and extinction efficiencies of charged spherical particles illuminated by a plane wave. The influences of various parameters (including surface charge, refractive index, size parameters, Debye mode, etc.) are studied. The rainbow produced by charged particles is analyzed. These results are of great significance in many fields including particle sizing, optical tweezers, etc.We propose a microlens array-type snapshot hyperspectral microscope system that can provide spatial spectrum sampling according to detector frame rates for the biomedical domain. The system uses a shared optical path design. One path is used to perform direct microscopic imaging with high spatial resolution, while the other is used to collect microscopic images through a microlens array; the images are then spatially cut and reimaged such that they are spaced simultaneously by the prism-grating type hyperspectral imager's dispersion. Rapid acquisition of a three-dimensional data cube measuring 28×14×180 (x×y×λ) can be performed at the detector's frame rate. The system has a spatial resolution of 2.5 µm and can achieve 180-channel sampling of a 100 nm spectrum in the 400-800 nm spectral range with spectral resolution of approximately 0.56 nm. Spectral imaging results from biological samples show that the microlens array-type snapshot hyperspectral microscope system may potentially be applied in real-time biological spectral imaging.In this paper, we implement a mixed constraint scheme with a global Gerchberg-Saxton algorithm for the improved generation of phase holograms from multiplane intensity distributions. We evaluate the performance of the proposed method compared to the mixed constraint sequential Gerchberg-Saxton algorithm, as well as the implementation of both schemes in several scenarios involving intensity distributions of up to nine independent planes. We also show that a careful selection of the parameters involved in the mixed constraint hologram generation technique can lead to even greater improvements in reconstruction quality. We present numerical results validating the effectiveness of our proposal.Satellite angular micro-vibration has an important impact on the efficiency of space quantum communication links. We measured the micro-vibrations on the Micius satellite in orbit using a high-precision optical sensor mounted on the satellite and analyzed the power spectral density. We designed a compound axis acquisition, tracking, and pointing (ATP) system based on a two-axis turntable and tested its suppressive effect on the micro-vibration through in-orbit experiments. The tracking error caused by the angular micro-vibration was found to be 9.3 µrad, with the energy concentrated primarily in the frequencies below 30 Hz; after suppression by the ATP system, the error was 0.47 µrad.To measure surface displacement on micro samples, a non-invasive method with both a low displacement measurement uncertainty below 100 nm and high spatial resolution of around 20 µm is required. In digital image speckle correlation, both requirements can be fulfilled individually but not simultaneously. To lower the displacement measurement uncertainty without deteriorating the spatial resolution, an ensemble averaging technique over multiple uncorrelated speckle patterns is presented. To generate and reproduce different speckle patterns, two concepts for the respective modulation of laser light illumination are investigated a low-cost concept with a rotating glass diffuser, as well as a faster concept using a digital micromirror device combined with a stationary diffuser with a maximum pattern rate of 17.9 kHz. Both setups lead to a measurement uncertainty reduction by one order of magnitude over a wide range of spatial resolutions. As a result, displacements in the micrometer range are measured with a measurement uncertainty of 40 nm and spatial resolution of 20 µm.