Lloyd´s mirror interference lithography using a single mode fiber spatial filter

In this paper, a simple but stable laboratory scale laser interference lithography(LIL) system by using a single mode optical fiber (SMF) as a spatial filter, flexible beam transport path, and beam expander has been demonstrated. The linearly polarized light from a HeCd laser (λ=325nm) was coupled into one end of a UV SMF and used the expanding beam from the other end for LIL exposures using a Lloyd´s mirror configuration. By using the output of the fiber as the source for the LIL system, the effects of pointing stability of the laser are eliminated. Although the SMF was not Polarization Maintaining (PM), the fiber could stably preserve the linear polarization of the light with I_TE:I_TM >;100. In this system, the gratings were produced easily in photoresist with a period of 220nm over an area of several square centimeters. Exposure times over 10 minutes with expanded beams result in high contrast patterns without any need for any active feed-back or fringe-locking.