Chen Yuankai, Yang Yongying, Wang Chen, Li Yao, Bai Jian
Appl Opt. 2020 Feb 10;59(5):1410-1419. doi: 10.1364/AO.383740.
Reference wave source (RWS) is the key component of the point diffraction interferometer, which determines the quality of the reference wave. The silicon nitride waveguide RWS is proposed to efficiently overcome the drawbacks of the existing RWSs, aimed at providing a spherical reference wave with high numerical aperture (NA) and high accuracy. The waveguide RWS consists of the straight waveguide, the bend waveguide, and the Y-branch edge coupler. The straight waveguide determines the accuracy and the NA of the reference wave, whereas the latter two determine the light transmittance of the RWS. Simulation results show that the peak-to-valley (PV) and the rms of the deviation from an ideal spherical wave are 2.86×10 (=532) and 4.83×10, respectively, and the maximum light transmittance could reach 24%. Experiment results show that the NA of the reference wave reaches up to 0.58, its spot has a good circular symmetry, and its intensity has Gaussian distribution. Although the light transmittance is only 0.2%, it is expected to improve with the development of experimental conditions and waveguide fabrication technology.
参考波源（RWS）是点衍射干涉仪的关键部件，它决定了参考波的质量。提出了一种氮化硅波导参考波源，旨在有效克服现有参考波源的缺点，以提供具有高数值孔径（NA）和高精度的球面参考波。该波导参考波源由直波导、弯曲波导和Y分支边缘耦合器组成。直波导决定了参考波的精度和数值孔径，而后两者决定了参考波源的光透射率。仿真结果表明，与理想球面波的偏差的峰谷值（PV）和均方根分别为2.86×10（=532）和4.83×10，最大光透射率可达24%。实验结果表明，参考波的数值孔径高达0.58，其光斑具有良好的圆对称性，强度呈高斯分布。虽然光透射率仅为0.2%，但随着实验条件和波导制造技术的发展，有望得到提高。
