Quasi suppression of higher-order diffractions with inclined rectangular apertures gratings.

Advances in the fundamentals and applications of diffraction gratings have received much attention. However, conventional diffraction gratings often suffer from higher-order diffraction contamination. Here, we introduce a simple and compact single optical element, named inclined rectangular aperture gratings (IRAG), for quasi suppression of higher-order diffractions. We show, both in the visible light and soft x-ray regions, that IRAG can significantly suppress higher-order diffractions with moderate diffraction efficiency. Especially, as no support strut is needed to maintain the free-standing patterns, the IRAG is highly advantageous to the extreme-ultraviolet and soft x-ray regions. The diffraction efficiency of the IRAG and the influences of fabrication constraints are also discussed. The unique quasi-single order diffraction properties of IRAG may open the door to a wide range of photonic applications.

Single-order diffraction grating designed by trapezoidal transmission function.

Diffraction grating is a widely used dispersion element in spectral analysis from the infrared to the x-ray region. Traditionally, it has a square-wave transmission function, suffering from high-order diffraction contamination. Single-order diffraction can be achieved by sinusoidal amplitude transmission grating, but the fabrication is difficult. Here, we propose a novel idea to design a grating based on trapezoidal transmission function, which makes traditional grating a special case. Grating designed by this idea can not only suppress higher order diffraction by several orders of magnitude as sinusoidal amplitude grating does but also greatly reduce the fabrication difficulty to the level of processing for traditional grating. It offers a new opportunity for fabrication of grating with single-order diffraction and measurement of spectrum without contamination of high-order harmonic components. This idea can easily extend to varied-line-space grating, concave grating with single-order diffraction, or zone plates with single foci and will bring great changes in the field of grating applications.