基于LiNbO_3的长周期波导光栅可调谐耦合器的设计

设计了一种基于LiNbO_3的长周期波导光栅可调谐耦合器.该耦合器利用长周期光栅的独有特性将输入波导的导模经包层模耦合至输出波导导模.由于LiNbO_3的电光效应,波导光栅芯层与包层的有效折射率随外加电压变化,从而耦合器的谐振波长及耦合效率可由外加电压调谐.分析了光栅周期与耦合器的长度对耦合器带宽和耦合效率调谐范围的影响,以及波导尺寸对谐振波长调谐灵敏度的影响.结果表明光栅周期越短,耦合器长度越长,则耦合器的带宽越窄,耦合效率调谐范围也越大.此外,谐振波长调谐灵敏度随波导宽度的增加而减小,而波导厚度对谐振波长调谐灵敏度的影响可以忽略.对光栅周期为94μm、长度为3.52cm的耦合器进行仿真,结果表明,谐振波长灵敏度为26.2pm/V,3dB带宽可达4.5nm,当外加电压从0变化到200V时,谐振波长变化5.24nm,耦合效率可在1到0.15之间进行调谐.

Design of Tunable Long-period Waveguide Grating Coupler Based on LiNbOa

A tunable long-period waveguide grating coupler based on LiNbO3 was proposed.The light can be coupled effectively from the input waveguide to output waveguide through the cladding because of the long period gratings' unique feature.The effective refractive indexes of the core and cladding of the waveguide grating will change accordingly as a result of electro-optic effect when a tunable voltage is applied,making the resonance wavelength and the coupling efficiency tuned by controlling the applied tuning voltage.The effects of coupler length and the grating period on bandwidth and the coupling efficiency tuning range,and the influence of the waveguide size on the resonant wavelength tuning sensitivity were analyzed.The results show that the shorter grating period and the greater coupler length lead to the narrower bandwith and the greater coupling efficiency tuning range.In addition,the resonance wavelength tuning sensitivity decreases with the increase of waveguide width,and the influence of thickness on the resonance wavelength tuning sensitivity can be ignored.For the coupler with the grating period of 94 μm and the coupler length of 3.52 cm,the simulation results show that the resonance wavelength tuning sensitivity can reach 26.2 pm/V,and the bandwith of 3 dB as 4.5 nm,when the applied voltage varying from 0 to 200 V,the resonant wavelength change 5.24nm,and the coupling efficiency can be tuning from 1 to 0.15.