High-Efficiency Broad-Angle Dielectric Diffraction Grating

Researchers at Stanford have developed a dielectric diffraction grating that provides high (near-unity) diffraction efficiencies in an ultra-compact volume. With applications in a variety of optical systems such as telescopes and VR, this innovation utilizes low-refractive-index materials and is compatible with nano-imprint fabrication methods for low-cost, large-area manufacturing. The grating is optimized for incoming light to have very large glancing incident angles, providing an ultra-compact volume and beam magnification. The grating is further optimized for the desired output angle, which can be selected over a broad range. By varying the grating across the full surface, light can be arbitrarily redirected, performing functions such as beam expansion or focusing. By including a second diffraction grating in series, more operations can be achieved such as chromatic dispersion-compensation or 2-D functionality. Furthermore, the low profile grating can be made visibly transparent when fabricated on a narrow-band Bragg mirror.

Overall configuration (image credit: the inventors)

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