Design of SiN waveguide reference wave source for point diffraction interferometer

Point diffraction interferometer (PDI) has become the most promising measurement tool since it is firstly proposed by Linnik and its key component used to generate the reference wave can be called as the reference wave source (RWS). A new RWS based on the silicon nitride (SiN) waveguide is now proposed, aimed at providing a spherical reference wave with high NA and high accuracy. Simulation results show that the PV and the RMS of the reference wave generated by the waveguide RWS are 2.86×10-4λ (λ=532nm) and 4.83×10-5λ respectively, and the maximum light transmittance of this RWS could reach 24%. In addition, the NA of the reference wave reaches up to 0.58.