Acousto-optic interaction induced photonic band gaps in silicon slab waveguides

We demonstrate that the photonic band gaps in silicon slab waveguides are generated through the acousto-optic (AO) interaction. By exciting the acoustic eigenmodes of slab waveguides, the refractive indices and interfaces of silicon slab can be modulated periodically to perturb the guided optical waves and open up the photonic band gaps. We find that the occurrence of the strong forbidden effect to form the band gaps is due to nonlinear interactions between the guided optical and acoustic modes. Using the finite-element method, we calculate the photonic band structures of TE waves and TM waves under the perturbation of the lowest three acoustic eigenmodes, respectively. The results show that the fundamental symmetric acoustic slab mode can create Bragg photonic band gaps of tunable width. With generating acoustic-wave amplitude of 1.0 % of the slab thickness, photonic band gaps from 70.76-71.09 THz for TE and 95.59-95.8 THz for TM are demonstrated. Applications include the design of optomechanical and AO devices and micro and nanolasers.

關鍵字

Optomechanical crystal ； acousto-optic interaction ； band gap

並列摘要

聲光作用應用於新穎光機電元件，展現了許多優異的光機電調變特性。本文研究次微米矽板聲波模態引致波導結構的光頻隙效應。首先，我們激發出矽板聲波模態，聲場將週期性地調變矽板的介面以及材料折射率，使得波導結構的光學性質產生週期性的變化。研究結果發現，藉由聲光作用的增強將可開啟布拉格的光頻隙。選擇適當的聲波模態與矽板長度，可有效地調控光的頻隙寬度與穿射率，進而調控光在波導結構中的傳播特性。本研究成果將可應用於主動調變的光機電元件。

並列關鍵字

光機械晶體；聲光作用；頻隙

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