Sun Mingwei, Xiong Bing, Sun Changzheng, Hao Zhibiao, Wang Jian, Wang Lai, Han Yanjun, Li Hongtao, Gan Lin, Luo Yi
Opt Express. 2024 Apr 22;32(9):16455-16466. doi: 10.1364/OE.521854.
Novel evanescently coupled waveguide modified uni-traveling carrier photodiodes (MUTC-PDs) employing a thick multi-layer coupling waveguide are reported. To improve the optical-to-electrical (O/E) conversion efficiency, a thick multi-layer coupling waveguide with a gradually increased refractive index from the bottom layer to the absorption layer is utilized. The refractive index profile facilitates the upward transmission of incident light into the absorption region, thereby enhancing the evanescent coupling efficiency. Meanwhile, the coupling waveguide, with a total thickness of 1.75 µm, expands the mode field diameter, thereby reducing the input coupling loss. Additionally, the top layer of the coupling waveguide also serves as the drift layer. This configuration facilitates efficient light absorption within a short PD length, thus ensuring ultrawide bandwidth and high O/E conversion efficiency simultaneously. Without an additional spot size coupler or anti-reflection coating, the measured responsivity is as high as 0.38 A/W for the PD with an active area of 5 × 6 µm. Meanwhile, an ultrawide 3-dB bandwidth of 153 GHz has been demonstrated.
报道了一种采用厚多层耦合波导的新型倏逝耦合波导改性单载流子光电二极管（MUTC-PD）。为了提高光电（O/E）转换效率，采用了一种从底层到吸收层折射率逐渐增加的厚多层耦合波导。折射率分布有利于入射光向上传输到吸收区，从而提高倏逝耦合效率。同时，总厚度为1.75μm的耦合波导扩大了模场直径，从而降低了输入耦合损耗。此外，耦合波导的顶层还用作漂移层。这种结构有利于在短的光电二极管长度内实现高效光吸收，从而同时确保超宽带宽和高O/E转换效率。在没有额外的光斑尺寸耦合器或抗反射涂层的情况下，对于有源面积为5×6μm的光电二极管，测得的响应度高达0.38 A/W。同时，已证明具有153 GHz的超宽3 dB带宽。
