Design of superresolved phase plates

Diffraction limit is always a key point to almost all optical systems, and diffraction effect is mostly dependent on the numerical aperture of objective and wavelength of light. However, it will be ultimately limited to improve the resolution continuously by increasing the numerical aperture or reducing the wavelength. Here, it is introduced that when these two parameters are fixed, focal spot smaller than Airy pattern could be obtained by means of superresolution techniques. Theoretical analysis for superresolution is presented. Binary phase plates corresponding to transverse or axial superresolution are designed, especially three-dimensional superresolution is proposed employing some optimization algorithms. The simulation results show that for light source with single wavelength or narrow spectral width, superresolution effects are fine, and when the superresolved phase plates are applied to femtosecond laser microfabrication system, the superresolution performances are even better when two-photon absorption is considered. Finally, the influences of spectrum of light sources are discussed. It has been demonstrated that when the spectral width is narrow, the performance of superresolved phase plates is approximately the same as that of a single wavelength. In conclusion, the superresoloved phase plates can be successfully applied to femtosecond laser systems for microfabrication, data memory and et al.