用于空间望远镜的膜光子筛

Abstract

According to the requirements of a space diffraction imaging system for large-aperture, weight-lightening and space deployable, a new diffraction optical element, PI photon sieve, was designed and fabricated. Firstly, the design theory of PI photon sieve was analyzed and the design parameters for an amplitude photon sieve were given according to the characteristics and the principle of space applications. Then, the mechanical structure of the photon sieve was designed by using UG software and a PI membrane photon sieve was successfully manufactured by employing micro-fabrication methods including e-beam vacuum coating, photolithography and wet etching. Finally, the diffraction efficiency of the PI photon sieve was measured and the imaging performance was tested. The experimental results show that the diffraction efficiency of photon sieve is 4.916% at the wavelength of 632.8 nm, which is about 73.9% of the theoretical value. For the star testing, by choosing the star hole with a diameter of 10 m and using a He-Ne laser for the light source, an ideal Airy disc with a diameter of 176.70 m was obtained, which is very close to the theoretical value, and the error is only 4.04%. For the imaging experiments, the maximum resolution of the photon sieve is measured to be 12.2 lp/mm, which is close to the spatial frequency limit of 14.4 lp/mm. It is shown that the experimental results are generally in agreement with the theoretical results. Comparing with other diffractive elements, PI photon sieve satisfies the application requirement of the primary mirror used in a space telescope for its lighter weight and better imaging performance.