The Research Of Deep-subwavelength Grating By Holographic- Immersion Lithography

The period of deep-subwavelength grating is much smaller than the wavelength of the work, which shows that the ideal polarization characteristic. The polarization characteristic of the deep-subwavelength, kinds of metal grating polarizers are fabricated for various bands. It has the characteristic of small volume, compact structure and working wavelength can be customized, has broad application prospects. The mask of deep-subwavelength grating is mainly produced by adopting the method of electron beam exposure, X-ray lithography and other methods, but these production methods process is complicated and costly, affecting the large-scale application of the metal grating in various fields. Compared with electron beam lithography and x-ray lithography, adopting holographic lithography in the fabrication of grating mask has the advantage of large area, low cost and simple process. In this paper, the manufacture technology of deep-subwavelength grating is investigated. Combining with the holographic lithography and immersion lithography, the period of 180 nm deep-subwavelength grating is fabricated by using holography-immersion lithography, and then the metal grating in visible broadband is fabricated. The main contents include the following aspects:(1) The significance of the research of deep-subwavelength grating and the application progress in the field of optical polarization.(2) The period of 575 nm, 350 nm and 240 nm grating mask are fabricated, we have analyzed the effects of the period, exposure volume, development time and different kinds of photoresist on the grating profile. According to the study the characteristics of the photoresist, the period of 180 nm deep-subwavelength grating is fabricated by using holography-immersion lithography.(3) The Finite Difference Time Domain(FDTD) theory is introduced and the TM transmission efficiency and extinction ratio of metal grating is discussed by FDTD theory. The best parameters of the metal grating used in visible band are pointed out and the influence of the angle of incidence and the process error on the characteristics of metal grating is analyzed.(4) For fabrication technique, the ion beam etching(IBE) is introduced. Metal grating is fabricated by ion beam etching and metal deposition technique process. The transmission efficiency and extinction ratio of the metal grating is measured, and the effects of the production process of the polarization properties of the metal grating are analyzed.