Design and fabrication of photonic crystal superlens for mid-infrared telescopes

摘要

We are developing a photonic crystal superlens based on negative refraction effect for mid-infrared astronomical telescopes to improve their angular resolution. The superlens will convert incident beams of large F-number to output beams of small F-number without changing image height. Firstly, we designed the superlens by theoretical calculations. We optimized two-dimensional dielectric structures of the superlens by calculating its band structures and iso-frequency contours using Plane-wave expansion (PWE) method. We also studied interface structures of input/output ports of the superlens in order to maximize its transmittance by numerical calculations using Fourier modal method (FMM). Then, wave-propagation simulations through the superlens by Finite-difference time-domain (FDTD) method showed that Full Width Half Maximum (FWHM) of point spread function will be reduced by approximately 15%. Secondly, we are trying to manufacture the superlens using a three-dimensional laser lithography system based on two-photon polymerization process. We also have measured complex refractive indices of SU-8 photoresist around wavelength of lOmicron by spectroscopic ellipsometry. The fabrication and optical benchmark of the superlens are currently underway. In this paper, we present experimental results as well as the design process of the superlens.