College of Optoelectics Science and Engineering, National University of Defense Technology, Changsha, 410073, China.
Opt Lett. 2011 Aug 1;36(15):2842-4. doi: 10.1364/OL.36.002842.
We realize a unidirectional transmission by cascading two nonparallel gratings (NPGs) made of isotropic, lossless, and linear media. For a pair of orthogonal linear polarizations, one of the gratings is designed as a polarizer, which is a reflector for one polarization and a transmitter for the other; another grating is designed as a polarization converter, which converts most of one polarized incident wave into another polarized transmitted wave. It is demonstrated by numerical calculation that more than 85% of the incident light energy can be transmitted with less than 1% transmission in the opposite direction for linearly polarized light at normal incidence, and the relative bandwidth of the unidirectional transmission is nearly 9%. The maximum transmission contrast ratio between the two directions is 62 dB. Unlike one-way diffraction grating, the transmitted light of the NPGs is collinear with the incident light, but their polarizations are orthogonal.
我们通过级联两个由各向同性、无损耗和线性介质制成的非平行光栅（NPG）实现单向传输。对于一对正交线性偏振，一个光栅设计为偏振器，对于一个偏振是反射器，对于另一个偏振是透射器；另一个光栅设计为偏振转换器，它将大部分入射的一个偏振波转换为另一个偏振透射波。数值计算表明，对于正常入射的线性偏振光，超过 85%的入射光能量可以以小于 1%的反向传输传输，单向传输的相对带宽接近 9%。两个方向的最大传输对比度为 62dB。与单向衍射光栅不同，NPG 的透射光是与入射光共线的，但它们的偏振是正交的。
