Tilted and axis-shift Lloyd's mirror system for recording low-density and large-area holographic grating

It is difficult to record holographic gratings of low density (<100 lines/mm) and large area simultaneously using traditional holographic system. In order to produce both low-density and large-area holographic gratings, a tilted and axis-shift (TAS) Lloyd's mirror system was designed for recording such holographic gratings. The recording area will increase largely especially for gratings of low density, by setting the angle between the Lloyd's mirror and the substrate larger than 90°, and meanwhile, by enlarging the intersection angle of incident light and mirror surface. Insuring the projected area onto the substrate by reflex equal to the incident area directly onto the substrate, the optical axis was shifted to realize the maximization of utilization of interference area. The contrast of fringe pattern was analyzed by the coherence for the laser beam in the space and time scale. The TAS Lloyd's mirror system for 60 lines/mm grating in the contrast of 0.8 was optimized, and as a result, the interference area was increased by about 150 times comparing to the traditional Lloyd's mirror system using the Lloyd's mirror of same dimensions.