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We present a design of 2D photonic crystal coupled-cavity waveguide with a high transmission efficiency and a quality factor simultaneously.By optimizing the structural parameters such as amount and radius of air holes between microcavities and waveguide,a 90% transmission efficiency is obtained with a Q factor of 8.20×104.In order to increase Q factor without sacrificing too much efficiency,a new kind of coupled-cavity waveguide is formed by introducing microcavity chains.Photons hop in adjacent microcavies.For this new kind of waveguide,Q factor is improved one order higher and transmission efficiency only decrease by 40%.The result has a practical gui-ding significance for application of photonic crystal in various different fields such as slow light,light trap,optical transmission.

We designed a type of reflector that consisted of one-dimensional diffraction gratings and one-dimensional photonic crystal.It can be used for thin-film silicon solar cells.The structure parameters were optimized by Legendre polynomial expansion method,and the reflectivity at the range of 400~1 200 nm was calculated.Under the high reflectivity one-dimensional photonic crystal,the propagation path of the photon can be extended and absorbed in the battery.The results show that the diffraction grating and a back reflector in the photonic crystal structure are efficient at the range of 750~1 100 nm.Back-reflection layer can greatly improve the light harvesting capacity and enhance the conversion efficiency of solar cells.