为了对双边布拉格反射波导半导体激光器的远场双瓣特性进行整形, 使之合并成为单瓣出光远场, 在布拉格反射波导的出光腔面上制作了表面等离子体双光栅结构。利用Au-SiO2光栅结构对表面等离子体的耦合效应和表面等离子体的透射增强现象将双瓣远场耦合成为单瓣出射, 然后通过Au-Si3N4光栅结构将透射的表面等离子体耦合成为光子进行准直出射, 最终得到单瓣准直的远场光斑。计算结果表明: 当Au-SiO2光栅厚度为50 nm, 填充因子为0.5, 光栅周期为350 nm; Au-Si3N4光栅厚度为70 nm, 填充因子为0.5,光栅周期为660 nm时可以得到远场发散角压缩到6.1°的整形光斑, 比没有双光栅结构的发散角缩小了3.6倍; 其远场透射光功率达到了模式光源的62%, 是没有双光栅结构单瓣出射功率的1.59倍; 同时腔面反射率也降低到12.4%, 是没有双光栅结构的0.53倍。结果显示,提出的双光栅结构优化了布拉格反射波导半导体激光器的出光远场特性。

To shape the beam with two-lobe far-field property from a dual side Bragg reflection waveguide semiconductor laser, a dual grating structure based on surface plasmons was prepared on the optical outlet facet of a Bragg reflection waveguide.It could combine the two lobes into a single lobe and to increase the optical intensity and quality of the beam. An Au-SiO2 grating was used to couple photons into surface plasmons and to combine the two lobe beams into a single beam. The surface plasmons also were taken to increase the extraordinary optical transmission. On the other hand, the Au-Si3N4 grating was used to help the outlet surface plasmons couple back to photons, meanwhile collimating the outlet beam to increase the far-field property. Numerical simulation results indicate when the parameters for Au-SiO2 show a depth of 50 nm, a filling factor of 0.5 and a duration of 350 nm, and those for Au-Si3N4 show 70, 0.5 and 660 nm, respectively, the outlet far-field beam will has a 6.1° divergence, which means the divergence angle shrinks by 3.6 times as that without the dual grating structure. The far-field optical transmission power reaches 62% of the model source, that is 1.59 times of the power of a single lobe far-field to the structure without the dual grating. Moreover, the cavity facet reflectivity has reduced to 12.4%, 0.53 times as the structure without the dual grating. It concludes that the dual grating structure has optimized the far field properties of dual side Bragg reflection waveguide semiconductor lasers.