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In order to accurately obtain the birefringence dispersion of liquid crystal variable retarder (LCVR) with wavelength ranges from 414nm to 702nm. Here, we propose an improved fitting method of birefringence dispersion by using the theory of polarized light interference. The birefringence of LCVR in 478nm is 0.3863 based on the improved method. The experimental result is 0.3862 and the percentage error is 0.026%, compared to the 1.761% of the original fitting method. This work provides an improved way to character the birefringence dispersion of LCVR.

In this paper, we propose a dielectric cavity enhanced high reflective multiband waveplate based on nano-grating structure, which exhibits quarter waveplate at two wavelengths (λ=810nm and λ=1530nm) and half waveplate at another wavelength (λ=1100nm). The simulation results show that at the working wavelengths (i.e., 810nm, 1100nm and 1531nm) of the device, the reflections are larger than 94% and the average value is about 95% with polarization orientation at 45° . As compare with the traditional metal nanograting waveplate, it has large phase difference with the same geometrical parameters (period, aspect ratio and thickness), and it also does not need to rotate the polarization orientation of the incident light when it work at different wavelengths. It provides a great potential for applications in advanced nanophotonic devices and integrated photonic systems.

The wave plate is an indispensable optical element for transforming polarization state in various optical fields. In the retarder’s applications, precise measurement of the retardance is necessary. However, there is no common and effective way to analyze resolution of the retardance measuring instrument. For ensuring the retardance measurement accuracy, an analysis method involving a wedge wave plate with a tiny angle between two planes is proposed to characterize the resolution. The retardance of the wedge wave plate varies linearly and slightly due to its linear and diminutive variation of thickness. The diminutive variation of retardance versus displacement can be measured when the instrument has enough resolution. And the instrument demonstrates higher resolution when it can measure smaller retardance variation. In the experiment, a wedge wave plate is mounted on a two dimensions stage and its one surface is normal to the detecting light of the instrument. And then the retardance is measured along one certain direction and the results are fitted linearly. The method can be used to evaluate the resolution differences of retardance measurement instruments. The gained resolution of both two instruments is superior to 0.1nm. Through several experiments, it can be demonstrated that the proposed analysis method has the advantages of easy operation, high efficiency and simple configuration.