This article presents a comprehensive analysis of the dispersion characteristics of virtually imaged phased array (VIPA) based on the principle of paraxial dispersion. It proposes a calculation equation for the Brillouin shift specifically designed for a single-stage VIPA-based Brillouin scattering measurement system. To capture Brillouin scattering images of water and anhydrous glycerol, a Brillouin scattering measurement system is constructed. The Brillouin shift of both substances is calculated using the proposed method in this article as well as the methods proposed by Giuseppe Antonacci and Pei-Jun Wu. The comparison of the three calculation results with the theoretical values confirms the accuracy and reliability of the proposed method. Moreover, this study addresses practical challenges in Brillouin image processing and introduces a precise method for extracting Brillouin spectra from the images. Additionally, a spectral calibration program is developed using MATLAB, guaranteeing accurate spectral extraction while greatly streamlining the spectral processing workflow.
As a standard light source, medium and low temperature blackbody is widely used in the field of quantitative infrared remote sensing, so it is urgent to improve its calibration accuracy. This paper studies the calibration method of medium and low temperature blackbody radiation temperature based on standard transfer detector, and designs a dual channel thermal infrared transfer standard radiometer. The radiometer adopts optical path structure with achromatic off-axis reflection, its optical mechanical system is placed in liquid nitrogen refrigeration vacuum Dewar, and an optical chopper is used to improve the systematic noise ratio. Finally, through the correction experiment of commercial blackbody radiation temperature, we found that there is a certain deviation at different temperature points, and its maximum value is 3.22k. The results prove the effectiveness of the design.
Radiometric calibration is one of the important ways to objectively evaluate the performance of spectral radiometric instruments and related devices. Therefore, the establishment and transfer of radiation standards have become the key technologies. In this paper, based on the traditional optical path for visible light calibration, the optical path for radiometric calibration in infrared band is designed by using light coupling and spatial filtering technology. The output light is collimated and parallel, polarized in P direction, the optical power is stable, the spot is pure and free of stray light. Also, the optical path can be adjusted accurately, which solves the problem that the calibration optical path of the absolute cryogenic radiometer (ACR) is difficult to adjust in the infrared band.
In order to establish the standard transfer chain traceable to the absolute cryogenic radiometer and improve the absolute calibration accuracy of spectral radiation for optical remote sensor, an optical radiometric calibration method based on broadband monochromator light source is proposed and the corresponding system is developed. In the system design, not only the high-efficiency monochromator lighting system, low aberration off-axis paraboloid reflection optical path, high precision mechanical adjustment device and positioning device are adopted, but also the light source water-cooling system is used to effectively improve the performance of the system. The results show that the system has the characteristics of broadband, high precision and good stability, which provides an effective and feasible technical means for realizing the standard transfer of detector with high-precision.
In this paper, we present an interferometric method to measure the shape of X-ray wavefront and the slope error of optical elements using microfocus x-ray source. According to the fractional Talbot effect, we built an x-ray grating interferometer for x-ray wavefront characterization at the working wavelength. The interferometer consists of a phase grating as a beam splitter and an absorption grating as a transmission mask for the detector. however, the determination of the relation between x-ray grating interferometer system parameters and the sensitivity, which is influenced by many optical elements in the system, is crucial for the optimization of the setup. It is very complicated to determine the best optical parameters in the course of experiment. The interferometry system is abstracted into a linear system, and then a mathematical model is constructed. The influence of different physical parameters, such as the source size and the energy spectrum, on the functional capability of an x-ray grating interferometer applied for X-ray wavefront characterization is discussed using numerical simulations based on Fresnel diffraction theory. The slope variations can be detected with an accuracy better than 100nrad.
The quantification of remote sensing information requires spectral radiometric calibration technology support with high accuracy, and this technology can ensure the comparability, accuracy, and long-term stability of data acquisition for sensor. Now, the calibration technique traced to the absolute cryogenic radiometer (ACR) is the trend of development. To improve the accuracy of infrared absolute spectral responsivity, a gold-plated hemisphere reflector is added to a thermopile detector with electrical substitution pins. So an infrared electrical substitution radiometer (ESR) is developed as the standard transfer detector. The spectral response linearity, uniformity, and stability of ESR are tested by electric substitution technology. We also have established a radiometric calibration system based on ACR. The combined uncertainty in the spectral responsivity of this detector from 0.7 to 20 μm is about 0.99%. The application of infrared ESR to radiometric calibration can improve the calibration accuracy of detectors through its shorter calibration chain.
The whispering-gallery-mode(WGM) resonators have a number of advantages, including ultra-high quality factor(Q factor), extremely small mode volume and so on. It has been widely used in many fields related to high sensitivity sensing measurement, photonics material, linear and non-linear optics, and optical communication. Here we built an experimental platform for microrod resonator fabrication with a high power CO2 laser. Based on this experimental fabrication platform, a microrod resonator with an approximate 2.5mm diameter has been made, which has an ultra-smooth surface. We also designed a test platform used a tapered fiber to measure optical performances of the fabricated microrod resonator. With this test platform, we measured the maximum Q factor of the fabricated resonator, which can reach 1.52×108 under the condition of 1550nm wavelength. The fabrication platform for microrod resonator designed by our laboratory with features of fast (less than 10min), cheap, repeatable and low experimental condition. These features have huge advantages on further scaled sensing application, optoelectronic device. Furthermore, in order to design and fabricate the ultra-high sensitivity temperature sensing device, we demonstrated the frequency shift feature of the fabricated microrod resonator. We heated the microrod resonator from 22 oC to 25 oC , then calculated the experimental data. we demonstrated our microrod resonator has 0.04nm frequency shift, 14.41pm/oC temperature sensitivity, and 6.3♦10−3oC temperature resolution.
We investigate a millimeter-size Calcium fluoride (CaF2) microdisk resonator fabricated by a customized machining procedure. Stable coupling can be realized in our microdisk resonator coupled by a special tapered fiber. The mcirodisktaper coupling system exhibits an ultra-high Q factor up to ~108. In particularly, our coupling system exhibits a freespectral- range low to ~0.03 nm (~3.91 GHz). The frequency is suitable in microwave photonic systems, such as optical filters, optoelectronic oscillators, and optical gyroscopes for several technological applications such as radar, light-wave technology, frequency synthesis, detection inertial navigation system.
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