<p>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.</p>
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 1.52×10<sup>8</sup> 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 <sup>o</sup>C to 25 <sup>o</sup>C , then calculated the experimental data. we demonstrated our microrod resonator has 0.04nm frequency shift, 14.41<i>pm</i>/<sup>o</sup>C temperature sensitivity, and 6.3♦10<sup>−3</sup> <sup>o</sup>C temperature resolution.
We investigate a millimeter-size Calcium fluoride (CaF<sub>2</sub>) 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 ~10<sup>8</sup>. 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.
The sunlight reflected from object surfaces is partly polarized, which is the useful information for polarized remote sensing. Therefore, it is important to perform the field polarization measurement, which can not only obtain the true physical polarization characteristics of object, but also be used to match with the polarimetric measured results from the airborne observation. However, there is no research concern the difference of polarized reflectance property between natural background and manmade objects in the natural environment. In this paper, we measure Visible-Near Infrared spectral polarized reflectance properties of two natural surfaces (soil and grass) and six manmade objects (cement and five painted materials) over the hemisphere directions in the field. The measurements are carried out with an automatic polarimetric spectrometer equipped with the goniometer. The results indicate that the polarization reflectance of manmade objects and natural background show the obvious anisotropic characteristics. The soil and grass produce the maximum reflectance value in the backscattering direction, which is opposite to the manmade objects. The polarized reflectance factor of manmade object is much greater than natural background, which can be used to effectively distinguish the object and the natural background. Our study has a great potential for target detection and identification in the field.
The technique of spectral polarization detection is currently one of the important contents of the research at home and abroad. The measuring principle of mid-infrared hyperspectral polarization was introduced. The measuring system of mid-wave infrared hyperspectral polarization was set up. The measuring experiments of polarization characteristic of two coating materials at different temperatures were carried out. The effective experimental data was obtained and analysed. The results show that: as the temperature goes up, the radiance of coating material increase; the more the difference of temperature and emissivity is, the more the upgrade of radiance is; the upgrade of degree of polarization don’t occurs larger change as the change of the upgrade of radiance. This phenomenon provides a meaningful reference for the application of mid-wave infrared spectral polarization characteristic.
Due to the new requirements of multi-site、multi-time、multi-satellites and highfrequency post-launch calibration, the hyperspectral post-launch cross-calibration system is developed. The system integrating global calibration-site network、calibration task automatic planning software and hyperspectral cross-calibration software can efficiently execute post-launch cross-calibration and dynamic performance evaluation. The application of the hyperspectral post-launch cross-calibration system is introduced. Hyperspectral imager Hyperion is used as reference sensor and HJ-1A/HSI is used as sensor to be calibrated. The system is used to acquire the cross-calibration coefficients of all HSI bands. The average differences of all HSI bands is 6.34% when cross-calibration coefficients are compared with site-calibration coefficients. The application feasibility of the post-launch cross-calibration system is validated preliminarily.