	US 12,235,162 B1
	Method, use, device, electronic equipment and storage medium for measuring polarization uniformity of non-uniformly totally polarized beams
Kan Chen, Hangzhou (CN); Kang Zou, Hangzhou (CN); Guofa Wang, Hangzhou (CN); Yijia Gong, Hangzhou (CN); Heliang Shen, Hangzhou (CN); and Xiaowu Shu, Hangzhou (CN)
Assigned to ZHEJIANG UNIVERSITY, Hangzhou (CN)
Filed by ZHEJIANG UNIVERSITY, Zhejiang (CN)
Filed on Oct. 19, 2022, as Appl. No. 17/969,666.
Application 17/969,666 is a continuation of application No. PCT/CN2021/096342, filed on May 27, 2021.
Int. Cl. G01J 4/04 (2006.01)

CPC G01J 4/04 (2013.01)

7 Claims

1. A method for measuring a polarization uniformity of non-uniformly totally polarized beams, wherein the method is implemented by a charge coupled device (CCD) camera, a computer, and one or more of an optical tweezer microscope, a surface plasmon detector, and a polarization tester, and the method comprises following steps:

measuring, by the CCD camera, a Stokes parameter distribution of a cross section of non-uniformly totally polarized beams, wherein the non-uniformly totally polarized beams are spirally polarized beams, polarization states on the cross section of non-uniformly totally polarized beams are linearly polarized beams, an angle of linear polarized beams changes with a radial angle of the cross section, and a Jones matrix of the spirally polarized beams satisfies:

where (r,θ) is a polar coordinate axis of the cross section, ω₀is a beam waist radius of a spot, and γ is a fixed angle, which determines an evolution angle of a linear polarization state of the spirally polarized beams, when γ=0, a linear polarization distribution of the cross section of the spirally polarized beams grows along a radial direction, while when γ=π/2, the linear polarization distribution of the cross section of the spirally polarized beams grows along a tangential direction;

inputting the Stokes parameter distribution of the cross section of non-uniformly totally polarized beams into the computer, and performing, by the computer, following steps;

calculating normalized Stokes parameters through the Stokes parameter distribution, and corresponding a polarization state distribution of the cross section to a Poincare sphere;

performing surface fitting on a polarization state distribution on the Poincare sphere through a spatial triangle surface fitting algorithm;

calculating a sum S_Dof the areas of the fitted triangular surfaces; and

dividing S_Dby a total area S₀of the unit Poincare sphere to obtain the polarization uniformity Ū of the non-uniformly totally polarized beams;

transferring the polarization uniformity Ū to one or more of the optical tweezer microscope, the surface plasmon detector, and the polarization tester;

wherein the sum S_Dof the areas of the fitted triangular surfaces is calculated by a Heron's formula, which comprises:

where i is a serial number of the fitted Delaunay triangle, and p_i, a_i, b_iand c_iare respectively the half circumference and lengths of the three sides of the Delaunay triangle, and the total area of surface fitting is