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采用渐变圆弓形散射元构建线性缺陷波导,并将其应用于光子晶体的慢光效应。在工作波长λ=1550nm时,通过圆弓形散射元单列纵向渐变,获得群折射率在31.4~95.0,低色散(Δng<10%)带宽在3.7~11.8nm,无量纲标量积ng×(Δλ)/λ在0.2268~0.2390,超低色散带宽(Δng<1%)在2.2~4.8nm之间的慢光;通过三列圆弓形散射元纵向周期性渐变,获得群折射率在31.6~108.2,低色散(Δng<10%)带宽在4.0~13.0nm,无量纲标量积ng×(Δλ)/λ在0.2650~0.2792,超低色散带宽(Δng<1%)在2.6~6.8nm之间的慢光;通过圆弓形散射元横向渐变,获得群折射率在32.1~89.3,低色散带宽在2.9~9.3nm,无量纲标量积ng×(Δλ)/λ在0.1670~0.1926,超低色散带宽在1.6~3.5nm之间的慢光。可见,采用散射元纵向渐变和横向渐变,特别是纵向渐变,可以实现慢光效应,从而为慢光结构设计和应用提供了新的方向。
A linear defect waveguide is constructed by using a gradual circular arc-shaped scattering element and is applied to the slow-light effect of photonic crystals. At the working wavelength of λ = 1550nm, the vertical gradient of circular arc-shaped scatterers was used to obtain the group index of 31.4 ~ 95.0, the low dispersion (Δng <10%) bandwidth of 3.7 ~ 11.8nm and the dimensionless scalar product ng × (Δλ) / λ is 0.2268 ~ 0.2390, slow light with ultra-low dispersion bandwidth (Δng <1%) between 2.2 ~ 4.8nm. By means of longitudinal periodic gradient of three circular arc-shaped scatterers, the group refractive index is between 31.6 and 108.2, Dispersion (Δng <10%) Bandwidth 4.0 ~ 13.0nm, dimensionless scalar product ng × (Δλ) / λ at 0.2650 ~ 0.2792, slow light with ultra-low dispersion bandwidth (Δng <1%) between 2.6 ~ 6.8nm The transverse refractive index of the circular bow-shaped scatterer is used to obtain the group refractive index of 32.1-89.3 and the low dispersion bandwidth of 2.9-9.3 nm. The dimensionless scalar product ng × (Δλ) / λ is 0.1670 ~ 0.1926. The ultra-low dispersion bandwidth is 1.6 ~ Slow light between 3.5nm. It can be seen that the slow-light effect can be achieved by using the longitudinal gradient and the lateral gradient of the scattering element, especially the longitudinal gradient, thereby providing a new direction for the design and application of the slow light structure.