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本文设计了一种由两侧挖孔的六棱柱单胞周期性排列而成的新型光力晶体纳米梁谐振腔, 利用有限元法计算了该结构在不同缺陷态下的带隙特性. 基于移动边界效应和光弹性效应机制, 采用一阶微扰理论并借助光力耦合系数计算法获得了光力晶体纳米梁谐振腔的光力耦合率, 同时分析了谐振腔声学模态的对称性, 并对光力耦合机制进行了探索. 研究表明: 改变缺陷数量或优化几何结构均可改善光学模式和机械模式的重叠性; 对于同种缺陷不同数量的谐振腔结构, 缺陷数量只会影响光力耦合率中移动边界效应和光弹性效应的作用方式, 而几乎不会改变其耦合率的大小. 分析具有梯度缺陷的光力晶体纳米梁谐振腔的振动模态对称性发现, 只有关于 x- y, x- z, y- z平面偶对称的振动模态才能与光学模态产生强耦合, 并得到高达2.25 MHz的光力耦合率.Optomechanical crystals can simultaneously modulate elastic waves and electromagnetic waves as well as localizing phonons and photons to enhance the acousto-optic interaction. In this work, a new type of optomechanical crystal nanobeam cavity is designed by periodically arranging the unit cells with double holes on both sides of a hexagonal prism. Considering the moving boundary effect and the photoelastic effect as well as using the first-order electromagnetic perturbation theory and the optomechanical coupling coefficient calculation method, the optomechanical coupling rate of the structure is calculated. The result shows that the overlap between the optical mode and the mechanical mode can be improved by changing the number of defects and optimizing the geometric structure. For the nanobeam cavity structures with different numbers of the like defects, the number of defects will only affect the action mode of the moving boundary effect and photoelastic effect in the optomechanical coupling rate, but will not change the coupling rate too much. In particular, the optomechanical coupling rate of the single defect optomechanical crystal nanobeam cavity can reach –1.29 MHz, and the equivalent mass is 42.6 fg. Moreover, the designed structure is simple and easy to process and fabricate. The coupling rate of even-symmetric optomechanical crystal nanobeam cavity based on gradient defect can reach 2.25 MHz, and the coupling rate of odd symmetric structure can reach 2.18 MHz, in which the moving boundary effect is dominant. Based on the symmetry analysis of the vibration modes of the optomechanical crystal nanobeam cavity with gradient defects, it is worth noting that only the even symmetrical vibration modes of x- y, x- zand y- zcan strongly couple with the optical modes. The surface density of the moving boundary effect is calculated and analyzed, and it is found that the surface density of the acoustic resonance mode with high symmetry also possesses high symmetry. However, when the surface density of the moving boundary effect in the defect state appears adjacent to each other and cancels out each other, it will destroy the coupling mode of the moving boundary effect and reduce the coupling rate, whether the symmetry is high or low. In addition, the designed optomechanical crystal nanobeam can also improve the quality factor of the resonant cavity by optimizing the defect structure while maintaining a high optomechanical coupling rate. Therefore, this research provides an effective means to find a structure with high optomechanical coupling rate, and also presents the ideas for designing the space sensors.
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A1 B1 C1 D1 E1 F1 gmb/ Hz –1.076×105 –1.805×106 6.721×105 –8.925×104 –1.204×105 3.790×105 gpe/ Hz 1.130×104 6.104×104 –1.888×103 6.130×102 9.662×103 7.078×104 g0/ Hz –9.626×104 –1.744×106 6.532×105 –8.864×104 –1.108×105 4.498×105 meff/ 10–17kg 2.429 4.072 1.657 1.719 6.816 4.698 G1 H1 I1 J1 K1 L1 gmb/ Hz –1.987×106 –9.336×103 –1.745×104 1.102×105 1.028×106 –2.258×103 gpe/ Hz –2.661×105 –1.470×103 –6.952×103 1.425×103 3.462×105 7.341×103 g0/ Hz –2.253×106 –1.081×104 –2.440×104 1.116×105 1.374×106 5.083×103 meff/ 10–17kg 7.086 2.879 2.949 3.320 8.115 3.701 
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A2 B2 C2 D2 E2 F2 G2 gmb/Hz –2.100×106 5.629×104 7.079×103 2.795×104 9.599×104 8.016×104 3.082×104 gpe/Hz –7.580×104 4.084×103 2.762×103 –8.579×103 –1.062×105 –4.091×103 5.240×103 g0/Hz –2.176×106 6.037×104 9.840×103 1.937×104 –1.024×104 7.607×104 –3.606×104 meff/10–17kg 3.28 0.991 1.05 3.65 2.79 1.41 0.110 H2 I2 J2 K2 L2 M2 N2 gmb/Hz –5.600×105 1.818×103 6.875×102 –1.391×103 –1.240×104 1.401×104 1.311×104 gpe/Hz 1.833×105 –2.254×103 1.972×103 –3.701×102 2.550×102 –8.942×103 9.903×102 g0/Hz –3.767×105 –4.357×102 2.659×103 –1.761×103 1.266×104 5.066×103 1.410×104 meff/10–17kg 9.16 1.96 1.89 0.296 0.233 0.287 0.260 下载:
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