图 1  本文考虑的理论模型　(a)被$ {\mathrm{Al}}_{0.33}{\mathrm{Ga}} _{0.67}{\mathrm{As}} $势垒隔开的GaAs调制掺杂量子阱结构的单周期能带示意图, 图中还显示了电子能级的位置及相应的波函数. (b)能级排列示意图. 前向传输时光场$ \varOmega_{{\mathrm{p}}}^{{\mathrm{f}}} $(红色), $ \varOmega_{{\mathrm{c}}} $(深蓝色), $ \varOmega_{{\mathrm{d}}} $(浅蓝色)与相应能级跃迁相互作用, 产生混频场$ \varOmega_{{\mathrm{m}}}^{{\mathrm{f}}} $(绿色); 后向传输时, 三个光场$ \varOmega_{{\mathrm{p}}}^{{\mathrm{b}}} $(玫红色), $ \varOmega_{{\mathrm{c}}} $, $ \varOmega_{{\mathrm{d}}} $耦合相应的能级跃迁. (c) SDQW样品与光场相互作用示意图

Fig. 1.  Theoretical model considered in this paper: (a) Schematic band diagram of a single period of the GaAs modulation-doped quantum wells structure separated by a $ {\mathrm{Al}}_{0.33}{\mathrm{Ga}} _{0.67}{\mathrm{As}} $ barrier. The positions of the calculated energy subbands and the corresponding modulus squared of the electronic wave functions are also displayed. (b) Schematic of the energy level arrangement. During forward transmission, the light fields $ \varOmega_{{\mathrm{p}}}^{{\mathrm{f}}} $ (red), $ \varOmega_{{\mathrm{c}}} $ (dark blue), $ \varOmega_{{\mathrm{d}}} $ (light blue) interact with the corresponding energy level transitions to generate a mixing field $ \varOmega_{{\mathrm{m}}}^{{\mathrm{f}}} $ (green); during backward transmission, the three light fields $ \varOmega_{{\mathrm{p}}}^{{\mathrm{b}}} $ (rose red), $ \varOmega_{{\mathrm{c}}} $, $ \varOmega_{{\mathrm{d}}} $ are coupled with corresponding energy level transitions. (c) Schematic diagram of the SDQW sample interacting with all optical fields.

图 2  前向探测场和后向探测场不同光学深度时的仿真图　(a)前向探测场$ \varOmega_{{\mathrm{p}}}^{{\mathrm{f}}} $和后向探测场$ \varOmega_{{\mathrm{p}}}^{{\mathrm{b}}} $在光学深度范围0—800内变化的相位图; (b)前向探测场和后向探测场的振幅随$ \alpha $的变化; (c)前向探测场和后向探测场的相移随$ \alpha $的变化. 其他参数取值为$ \gamma_{21}=0.2\; {\mathrm{meV }}$, $ \gamma_{31}=\gamma_{41}=2\; {\mathrm{meV }} $, $ \varOmega_{{\mathrm{c}}}=\varOmega_{{\mathrm{d}}}=24.5\varGamma $, $ \delta_{{\mathrm{p}}}=\delta_{{\mathrm{c}}}=0 $, $ \delta_{{\mathrm{d}}}=100.25\varGamma $, $ \varGamma=4\; {\mathrm{meV }} $

Fig. 2.  Simulation diagrams of the forward probe field and the backward probe field at different optical depths: (a) Phase diagram of the forward probe field $ \varOmega_{{\mathrm{p}}}^{{\mathrm{f}}} $ and the backward probe field $ \varOmega_{{\mathrm{p}}}^{{\mathrm{b}}} $ in the optical depth range 0 to 800; (b) diagram of the amplitude of the forward probe field and the backward probe field changing with $ \alpha $; (c) diagram of the phase shift of the forward probe field and the backward probe field changing with $ \alpha $. Other parameters are $ \gamma_{21}=0.2\; {\mathrm{meV }} $, $ \gamma_{31}=\gamma_{41}=2\; {\mathrm{meV }} $, $ \varOmega_{{\mathrm{c}}}=\varOmega_{{\mathrm{d}}}=24.5\varGamma $, $ \delta_{{\mathrm{p}}}=\delta_{{\mathrm{c}}}=0 $, $ \delta_{{\mathrm{d}}}=100.25\varGamma $, and $ \varGamma=4 \; {\mathrm{meV }}$.

图 3  不同探测场的振幅和相移在不同驱动失谐$ \delta_{{\mathrm{d}}} $时的仿真结果　(a)前向探测场和后向探测场的振幅随$ \delta_{{\mathrm{d}}} $的变化; (b)前向探测场和后向探测场的相移随$ \delta_{{\mathrm{d}}} $的变化. 其他参数取值与图2 相同, 除了$ \alpha $ = 630

Fig. 3.  Simulation results of the amplitude and phase shift of different probe fields under different detuning of driving fields $ \delta_{{\mathrm{d}}} $: (a) Change graph of the amplitude of the forward probe field and the backward probe field with $ \delta_{{\mathrm{d}}} $; (b) change graph of the phase shift of the forward probe field and the backward probe field with $ \delta_{{\mathrm{d}}} $. Other parameters are the same as in Fig. 2, except for $ \alpha $ = 630.

图 4  光隔离器和环行器装置的简单示意图. 对于光隔离器, 只考虑嵌入SDQW纳米结构的上分支. 为了实现光环行器, 下分支与上分支使用分束器BS 1和BS 2组成MZI

Fig. 4.  A simple schematic of the optical isolator and circulator devices. For the optical isolator, we consider only the upper branch embedded in the SDQW nanostructure. To implement the optical circulator, the lower branch and the upper branch use beam splitters BS 1 and BS 2 to form the MZI.

图 5  用作光隔离器时的仿真结果　(a)传输系数$ T_{12} $和$ T_{21} $随探测失谐$ \delta_{{\mathrm{p}}} $的变化图; (b)隔离比IR和插入损耗IL随探测失谐$ \delta_{{\mathrm{p}}} $的变化图. 除了$ \alpha=630 $, 其他参数取值与图2 相同

Fig. 5.  Simulation results when used as an optical isolator: (a) Graph of transmission coefficients $ T_{12} $ and $ T_{21} $ with probe detuning $ \delta_{{\mathrm{p}}} $; (b) graph of isolation ratio IR and insertion loss IL with probe detuning $ \delta_{{\mathrm{p}}} $. Parameters are the same as in Fig. 2, except that $ \alpha=630 $.

图 6  用作光环行器时的仿真结果　(a), (b)前向循环和后向循环传输系数与探测失谐$ \delta_{{\mathrm{p}}} $的关系; (c)光环行器的保真度F和平均光子存活率η与探测失谐$ \delta_{{\mathrm{p}}} $的关系. 除了$ \alpha=630 $, 其他参数取值与图2 相同

Fig. 6.  Simulation results when used as an optical circulator: (a), (b) Relationship between the transmission coefficients of the forward cycle and the backward cycle and the probe detuning $ \delta_{{\mathrm{p}}} $; (c) fidelity F and average survival probability η of the optical circulator versus probe detuning $ \delta_{{\mathrm{p}}} $. Parameters are the same as in Fig. 2 except for $ \alpha=630 $.