Shen Bing, Polson Randy, Menon Rajesh
Opt Express. 2015 Aug 10;23(16):20961-70. doi: 10.1364/OE.23.020961.
We demonstrate broadband asymmetric transmission or optical-diode behavior via a digital metasurface, that is, a surface that is digitally patterned at subwavelength dimensions. Enhanced light-matter interactions at the interfaces of the metasurface break the symmetry in the propagation direction, and enables high light-transmission in one direction, while strongly reflecting the light in the opposite direction. We measured a peak extinction ratio of 11.18 dB and peak forward transmission efficiency of 74.3% at the design wavelength of 1.55μm. The operational bandwidth of the device was 201nm. We further designed, fabricated and experimentally characterized a digital metasurface that enables polarization-independent optical-diode behavior, which we believe is the first device of its kind. Our digital metasurfaces enable the optical-diode behavior in a single layer of sub-wavelength thickness for several input modes and therefore, can perform as a passive, albeit imperfect optical isolator.
我们通过数字超表面展示了宽带非对称传输或光学二极管行为，即一种在亚波长尺度上进行数字图案化的表面。超表面界面处增强的光与物质相互作用打破了传播方向上的对称性，使得光在一个方向上具有高透射率，而在相反方向上强烈反射光。在1.55μm的设计波长下，我们测得的峰值消光比为11.18dB，峰值正向传输效率为74.3%。该器件的工作带宽为201nm。我们进一步设计、制造并通过实验表征了一种能够实现偏振无关光学二极管行为的数字超表面，我们认为这是同类中的首个器件。我们的数字超表面能够在单层亚波长厚度内对多种输入模式实现光学二极管行为，因此，尽管并不完美，但可作为一种无源光学隔离器。
