Study on the calibration of full polarization imager.

Polarization is one of the fundamental properties of light, which has a wide range of applications and is developing rapidly. To meet the needs of polarization detection, different types of polarization instruments came into being. The precision of the polarization detection instruments is vital to the result analysis. In this paper, a full polarization imager is designed, and the radiometric calibration and polarization calibration of this instrument are studied. In radiometric calibration, the different numbers lights are set to verify the light intensity response of the imager. The mathematical model was constructed for numerical fitting, and the correlation between the fitted values and the measured values in the 490 nm, 550 nm, and 670 nm bands was above 0.99. Fixed the radiance of the integrating sphere, and adjusted exposure times. The correlation of the three bands is above 0.99, which verifies that the radiative stability of the imager is good. The polarimetric calibration system adopts the adjustable degree of polarization reference light source (APOL). The theoretical and measured values of the degree of polarization of reference light sources in three different bands are analyzed. The results show that the measurement accuracy of the 490 nm band is less than 2%. The precision of polarization measurement in the 550 nm band is less than 1.5%, and the precision of polarization calibration in the 670 nm band is less than 1%. The imager is verified to have high polarization calibration accuracy and meets the requirements of high-precision polarization detection.

Structural exploration of Au x M- (M = Si, Ge, Sn; x = 9-12) clusters with a revised genetic algorithm.

We used a revised genetic algorithm (GA) to explore the potential energy surface (PES) of Au x M- (x = 9-12; M = Si, Ge, Sn) clusters. The most interesting finding in the structural study of Au x Si- (x = 9-12) is the 3D (Au9Si- and Au10Si-) → quasi-planar 2D (Au11Si- and Au12Si-) structural evolution of the Si-doped clusters, which reflects the competition of Au-Au interactions (forming a 2D structure) and Au-Si interactions (forming a 3D structure). The Au x M- (x = 9-12; M = Ge, Sn) clusters have quasi-planar structures, which suggests a lower tendency of sp3 hybridization and a similarity of electronic structure for the Ge or Sn atom. Au9Si- and Au10Si- have a 3D structure, which can be viewed as being built from Au8Si- and Au9Si- with an extra Au atom bonded to a terminal gold atom, respectively. In contrast, the quasi-planar structures of Au x M- (x = 9-12; M = Ge, Sn) reflect the domination of the Au-Au interactions. Including the spin-orbit (SO) effects is very important to calculate the simulated spectrum (structural fingerprint information) in order to obtain quantitative agreement between theoretical and future experimental PES spectra.