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设计了一种一次性制备双边调制布拉格波导光栅的新方法。通过周期性改变波导的宽度实现波导光栅的空间调制,其优势是利用波导的制备工艺将波导及光栅一次性制备,工艺简单。基于转移矩阵理论,研究了该结构的波导光栅反射谱特性与波导宽度、波导宽度差、光栅占空比及波导宽度变化的形状的关系。结果表明,双边调制比皱阶调制3 d B带宽明显变大,最大反射率稍有增大。当波导宽度差不变时,随波导宽度增大,最大反射率和零值带宽都随之减小。当波导宽度不变时,随波导宽度差增大,最大反射率和零值带宽都随之增大。当波导宽度与波导宽度差均不变时,光栅占空比为1/2时最大反射率最高,零值带宽最大。且波导宽度差足够大时,可通过改变占空比来改变零值带宽。波导变化的形状对波导光栅的反射谱性能影响较小。
A new method to fabricate bilateral modulated Bragg waveguide grating is designed. The space modulation of the waveguide grating is realized by periodically changing the width of the waveguide. The advantage of the method is that the waveguide and the grating are prepared in one time by the preparation process of the waveguide, and the process is simple. Based on the transfer matrix theory, the relationship between the reflection spectrum of the waveguide grating and the shape of waveguide width, waveguide width difference, grating duty cycle and waveguide width variation was studied. The results show that the bandwidth of 3 d B modulated by the bilateral modulation ratio is obviously larger and the maximum reflectance slightly increases. When the waveguide width is constant, as the waveguide width increases, the maximum reflectance and zero bandwidth decrease. When the waveguide width is constant, the maximum reflectance and the zero-value bandwidth increase with the increase of the waveguide width difference. When the difference between the waveguide width and the waveguide width is constant, the maximum reflectance is the highest when the duty ratio of the grating is 1/2, and the maximum value of the zero value bandwidth. When the waveguide width difference is large enough, the zero-value bandwidth can be changed by changing the duty ratio. The shape of the waveguide changes has little effect on the reflection spectrum performance of the waveguide grating.