Compact optical one-way waveguide isolators for photonic-band-gap microchips
Compact optical one-way waveguide isolators for photonic-band-gap microchips
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DOI：
10.1103/physreva.78.023804
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发表时间：
2008-08-01
影响因子：
2.9
通讯作者：
John, Sajeev
中科院分区：
文献类型：
--
作者：
Takeda, Hiroyuki;John, Sajeev
在二维(2D)光子晶体(PC)中，我们展示了紧凑型光波导隔离器，其中光只能单向传播。波导是由具有磁畴壁的磁光材料组成的。磁光效应和磁畴壁分别破坏了时间反转和空间反转对称性，导致了对给定频率的前向和后向传播光具有不同群速度的非互易光波导。当后向光具有零群速度时，只有前向光可以传输，而后向光停止。通过在非互易PC光波导中引入吸收损耗，消除了背向光的缓慢泄漏(当群速度不是精确为零时)。因此，对前向光的吸收小于对后向光的吸收。通过引入增益材料和电流注入放大信号，前向光可以无净损耗传输，只有后向光衰减。我们证明了群速度几乎为零的后向光由于在长的有效光程长度上的吸收而可以被消除。这实现了紧凑型片上光子带隙隔离器。波导器。隔离器假定为。由氧化铕组成，在0.9特斯拉磁场下，波长为1.5微米，法拉第旋转角为3.49×10(3)rad/cm。在8.5微米长的波导隔离器中，背向光在特定频率上的透射率几乎为零。当前向光的透过率通过电流注入放大到i时。随着器件长度的增加，以1.5微米波长为中心的可用带宽可达12 nm(L=42.6µm)。我们证明了类似的结果对非对称：非互易无磁畴壁的波导。对于三维有限厚度的二维膜光子晶体，论证了紧凑型片上光子带隙隔离器的可能性。计算采用平面波展开法、时域有限差分法和光学Wannier函数法。
In two-dimensional (2D) photonic crystals (PC's), we demonstrate compact optical waveguide isolators in which light can propagate only one way. Waveguides are composed of magneto-optical materials with magnetic domain walls. Magneto-optical effects and magnetic domain walls break time-reversal and space-inversion symmetries, respectively, leading to nonreciprocal waveguides with different group velocities for forward and backward propagating light of a given frequency. When backward light has a zero group velocity, only forward light can be transmitted while backward light stops. Slow leakage of backward light (when the group velocity is not precisely zero) is eliminated by introducing absorption loss in nonreciprocal PC waveguides. Then, absorption of forward light is less than that of backward light. Introducing gain material and signal amplification by current injection, forward light can propagate with no net loss and only backward light is attenuated. We demonstrate that backward light, with nearly zero group velocity, can be eliminated because of absorption over a long effective optical path length. This enables compact on-chip photonic band-gap isolators. The waveguide. isolator is assumed to be. composed of europium oxide with the Faraday rotation angle of theta(F)=3.49X10(3) rad/cm at wavelength lambda=1.5 mu m under a magnetic field 0.9 Tesla. In a waveguide isolator with the length of 8.5 mu m, transmittance of backward light is mostly zero at a specific frequency. when transmittance of forward light is amplified to I by current injection. The usable bandwidth is up to 12 nm centered at 1.5 micron wavelength as the device length is increased (L=42.6 mu m). We demonstrate similar results for an asymmetric: nonreciprocal waveguide without a magnetic domain wall. The possibility of compact on-chip photonic band-gap isolators is demonstrated for 2D membrane photonic crystals with finite thickness in the third dimension. Computations are performed using plane wave expansion, finite difference time domain, and optical Wannier function methods.