Design of dynamically tunable photonic crystal mirrors in THz free electron lasers
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摘要: 利用传输矩阵法对太赫兹自由电子激光光腔光子晶体镜进行了模拟设计，中心波段在1~3 THz。对光腔镜的光子晶体结构参数如介质厚度、层数、折射率与反射率的关系等进行了研究，并给出了一维光子晶体用于高反镜的设计方法。通过对耦合输出镜光子晶体中引入缺陷层情况的数值模拟，发现通过对缺陷层的调节设计，可以实现耦合输出率的可调谐；并给出了可用于THz 自由电子激光光腔耦合输出镜的调节方法。通过对介质层厚度的调节设计，可以实现反射光谱的整体移动，从而实现宽谱可调谐，扩大了高反镜及耦合输出镜的调节范围。Abstract: A 1-D photonic crystal (PC) mirror of the optical resonator for THz free electron lasers (FELs) is designed theoretically with central frequencies from 1 to 3 THz. The relationship between the reflection spectrum and structural parameters of 1-D PC, such as dielectric thickness, number of layers, and refraction index, is studied. A systematical method to design PC mirrors with high reflectivity is proposed. The out-couplers in the presence of defect layers in PC structure is simulated. It is shown that the out-coupling ratio of the resonator is dynamically tunable by careful adjustment and design of the defect layers. A practical tuning method for THz FELs using PC mirrors is proposed. Moreover, the shift of the whole reflection spectrum is also viable by adjusting the dielectric layer thickness, which extends the tuning range of high reflection PC mirrors and out-couplers.
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Key words:
- free electron laser /
- optical resonator /
- terahertz /
- photonic crystal /
- dynamically tunable
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