High-efficiency V-shaped phase gratings to suppress high order diffractions

Abstract

We propose a V-shaped phase grating to simultaneously improve the diffraction efficiency of the 1st order diffraction mode and suppression of high order modes. An analytic description is given that indicates the 0th, 2nd, 3rd, and 4th order diffractions can be completely suppressed while the 1st order absolute diffraction efficiency can reach a theoretical maximum of 27.72%, which is much higher than that reported from single order gratings, such as sinusoidal amplitude transmission gratings. The dependencies of the 1st order diffraction efficiency on the wavelength and depth deviations are also discussed. The experimental results show that the absolute efficiency of the 1st order diffraction is 25.85% while the 2nd, 3rd, and 4th order diffractions disappear completely, confirming the theoretical predictions. The diffraction patterns of a xenon lamp demonstrate the suppression of the high order diffractions from our quartz phase grating. The unique dispersive properties of the V-shaped phase grating make it attractive for broad spectroscopy and high-accuracy monochromatization applications.