基于光声晶体结构的受激布里渊散射芯片

On-chip stimulated Brillouin scattering (SBS) has plenty of significant potential applications, including on-chip optical comb, ultra-low phase noise laser, optical isolator, microwave photonic filter, slow light and optical storage, sensing and array signal processing. However, on-chip stimulated Brillouin scattering based on SOI (Silicon on Insulator) chip has not been realized for a long time as acoustic wave tends to leak into silica and silicon waveguide cannot simultaneously confine both acoustic and optical waves. Different with the confining mechanism of traditional waveguides, optomechanical crystals simultaneously confine both acoustic and optical waves with phononic and photonic bandgap by artificially designing the geometric parameters of nanostructure, such as the period and the hole radius. This is a brand new mechanism to realize stimulated Brillouin scattering on silicon chip. Based on the innovative new mechanism of utilizing the bandgaps of optomechanical crystal to confine both photon and phonon, this project will study the coupling between optical and acoustic waves in optomechanical crystals and fundamentally resolve the problem that optical and acoustic waves cannot simultaneously guided on the silicon chip. Finally, this project will realized stimulated Brillouin scattering on silicon chip and explore the realization and applications of on-chip high Brillouin gain devices.

片上受激布里渊散射有很多重要的潜在应用，例如片上光频梳、超低相位噪声激光器、光隔离器、微波光子滤波器、布里渊慢光和光存储、传感和阵列信号处理等。但是在硅基光器件材料SOI（Silicon on Insulator）片上却难以实现受激布里渊散射，原因是声波更容易泄露到作为Insulator的二氧化硅材料中，在光传导的硅层中无法实现光波与声波的同时限制和传导，难以构成产生受激布里渊散射的条件。本项目创新的提出利用光声晶体对光子和声子带隙限制的新机理，通过设计微纳结构的周期、孔径等结构参数，形成光子和声子带隙，研究光声晶体中的光波与声波相互作用的受激布里渊现象，从根本上解决光波和声波无法同时在片上硅基结构中限制和传导的问题，基于这一全新机理最终实现硅基受激布里渊散射芯片，并探索片上高增益布里渊器件的实现与应用。

针对片上受激布里渊散射实现的难点，本项目的研究工作直接瞄准片上光子与声子的相干相互作用展开研究，在光子、声子激射的理论研究、设计实现到测试技术上取得了关键性突破。提出了二维雪花光声晶体波导用于实现慢光增强的受激布里渊散射；通过引入光声晶体微腔，有效的增强了光子和声子的相互作用，首次实现了光子、声子的同时激射，器件长度缩短至10μm，阈值降至0.5mW；理论上研究了光子、声子在腔增强情况下的激射动力学，并首次给出了光子和声子同时激射的线宽公式，论证了在热噪声下，声子和光子的线宽趋于Schawlow-Townes极限。相比硅基纳米波导的布里渊激光器（~2000μm, 7.5mW(Science, 360_1113, 2018)），硅基光声晶体微腔中的光子和声子同时激射现象，为新型硅基片上相干光源提供了更易集成、更低功耗的解决方案；在此基础上，本项目进一步拓展光声激射后的应用，获得了频率6.22GHz、线宽5.2kHz的声子激射模式，实验实现了基于声子激射的高精度片上折射率和质量传感；基于光子晶体超表面结构，成功研制世界首个可见光波段高精度的光谱成像芯片。项目成果得到国际、国内同行认可，发表论文4篇，其中SCI收录3篇，EI收录1篇，专利授权9项，国际国内会议上做特邀报告4次。