硅基马赫曾德电光调制设计优化与实现

Design Optimization and Implementation of Silicon Mach-Zehnder Electro-Optic Modulators

对单端推挽驱动硅基调制器进行了优化设计和实验验证。为了获得较高的调制器性能,首先对PN结的结构参数和掺杂浓度进行了仿真优化,以提高调制效率并降低光传输损耗;其次,对行波电极的阻抗匹配、相位匹配和微波损耗予以了研究,重点分析了低掺杂平板区宽度、行波电极传输线宽度(TWE)和间距对调制性能的影响。在理论分析和仿真计算的基础上,对单端推挽驱动调制器进行了频谱测试、小信号响应测试和高速调制码型测试。调制器的片上插入损耗在7~9 d B,半波电压约为5 V。偏置电压为0 V时,优化后的调制器的带宽大于18 GHz,入射端反射系数低于-20 d B,行波电极具有较好的阻抗匹配。当反偏电压大于4 V时,调制器的带宽可增加到30 GHz以上,并且能实现56 Gbit/s的二进制强度(OOK)调制和40 Gbit/s的二进制相移键控(BPSK)调制。

In this paper,the design optimization and experimental demonstration ofsingle-drive push-pull silicon electro-optic modulators are presented.In order toimprove the modulation efficiency and lower the optical propagation loss,the PNjunction profile and doping concentrations are firstly optimized.Next,the impedancematch,phase match and microwave loss are studied,and in particular,the influenceof low-doping slab width,travelling-wave electrode(TWE)width and spacing on themodulator performance are analyzed.Following the comprehensive theoreticalanalysis and numerical simulation,the modulator performance measurements,including the optical transmission spectrum upon single-drive push-pull tuning,small-signal microwave signal response,and high-speed digital signal modulation areconsequently carried out.The on-chip insertion loss of the modulators is around7-9dB and the half-wave voltage is5V.At a bias voltage of0V,the optimizedmodulator has a modulation bandwidth of>18GHz.The microwave reflectivity at theentrance of the TWE is less than-20dB,suggesting good impedance match.Whenthe reverse bias voltage is increased to4V,the modulation bandwidth can exceed30GHz,allowing for realization of56Gbit/s on-off keying(OOK)and40Gbit/s binaryphase-shift keying(BPSK)modulations.