Broadband optical concentration technology based on grating side-coupling

摘要

Though the technology of grating side-coupling is often applied in fields, such as coupling of light of single wavelength or narrow waveband, pump of fiber laser, integration of optical waveguide, its application for broadband coupling of visible spectrum is rarely studied. Sunlight can concentrate and output at the edge of waveguides by integrating sub-wavelength gratings with waveguides, making it a novel solar concentrator. In this paper, we simulated different grating structures with the finite-difference time-domain solution software (FDTD) to obtain the optimal structure design, since different grating structures feature different diffractive efficiencies. The result demonstrates that the structures mentioned above all feature good diffractive efficiencies in broadband wavelength, among which the blazing grating reaches the largest efficiency, namely 48.8%.This kind of sub-wavelength gratings feature integration of small size, which makes it promising in absorption of solar energy, such as lumination, photovoltaic cell, space melting, etc.