2μm波段Ge-on-SOI光电探测器的TPA探测

TPA Detection of 2μm Wavelength Band Ge-on-SOI Photodetector

【目的】随着光通信技术的快速发展,工作在传统通信窗口的光通信系统未来可能会面临通信“波段紧缩”的状况。而在2μm波段,空芯光子带隙光纤的损耗可以低至0.2 dB/km,掺铥光纤放大器(型号为CTFA)在2μm波段的增益峰值可达30 dB,这些高性能器件的出现使得2μm波段有缓解通信“波段紧缩”的潜力,同时也对制作难度小且利于大规模生产的2μm波段硅基光电探测器提出了需求。硅基光电探测器的工作波段扩展主要方案有采用具有可调谐带隙的Ⅲ-Ⅴ族材料、引入低带隙宽度材料作为吸收区和利用吸收区材料在2μm波段新的光吸收机制等。而Ge具有非常高的双光子吸收(TPA)系数(1225 GW/cm@2μm),并且Ge-on-绝缘体上硅(SOI)光电探测器结构兼容标准硅光器件制作工艺,具有制作难度较低和成本较低的优势,是2μm光电探测器的一种较优方案。文章的研究目的是验证Ge-on-SOI光电探测器利用TPA这一特殊光吸收机制实现2μm波段光电探测的可行性。【方法】文章基于Ge材料在2μm波段较高的TPA效应产生电流的物理机制实现了2μm波段的光电探测。理论上,对Ge材料通过TPA效应产生的光生电流大小进行了分析与讨论;在实验上,基于片上硅基器件有源测试系统对商用波导型Ge-on-SOI光电探测器的光输入端(光栅耦合器)施加经过掺铥光纤放大器放大后的高功率2μm波段输入光,并调整光纤与光栅的对准以及输入光偏振态以尽可能减少输入光传输到Ge吸收层的损耗,最终通过探针获取探测器的TPA光生电流。【结果】在功率为21.9 dBm的2μm光信号输入下,该商用波导型Ge-on-SOI光电探测器在2μm波段产生了高至651 nA的TPA净光生电流,并近似获得了>10 mA/W的响应度。【结论】文章验证了通过Ge材料TPA效应实现2μm波段光电探测器的科学可行性,为基于TPA的2μm波段Ge-on-SOI光电探测器的设计提供了实验支撑。

【Objective】The optical communication system working at the traditional telecommunication band is faced with“capacity crunch”with the rapidly development of optical communication technology.The acceptable loss of 0.2 dB/km(@2μm)from the hollow-core photonic bandgap fibers as well as the high optical amplification gains(30 dB@2μm)of thulium-doped fiber amplifiers(CTFA type)provides the potential for the 2μm wavelength band to alleviate the communication“capacity crunch”.As a result,the needs of the 2μm silicon-based photodetectors is also raised due to its mature and convenient manufacture process.The main solutions of the silicon-based photodetectors include the usage ofⅢ-Ⅴcompounds with tunable band gap,the introduction of low band gap width materials as absorption regions,the use of new absorption mechanism in optical absorbed material at the 2μm wavelength band and so on.The Ge material has a high Two Photon Absorption(TPA)coefficient(1225 GW/cm@2μm).And the Ge-on-Silicon-On-Insulator(SOI)photodetector is an excellent method to realize 2μm optical signal detection,which is compatible with the standard silicon photonics device manufacturing process that has the advantages of low production difficulty and cost.The purpose of this paper is to verify the feasibility of the Ge-on-SOI photodetector to achieve 2μm wavelength band photoelectric detection by using the special optical absorption mechanism of TPA.【Methods】In this paper,the photoelectric detection at the 2μm wavelength band based on the physical absorption mechanism of current generated from high TPA of Ge material is realized.The quantification of the photocurrent generated by Ge material through TPA effect is analyzed and discussed in this paper.In the experimental test,we first apply a high power 2μm wavelength band input light source magnified by thulium-doped fiber amplifiers to the input port(grating coupler)of the commercial waveguide-type Ge-on-SOI photodetector in the on-chip active silicon photonics device test system.Then we adjust the alignment of the optical fiber with the grating coupler and the input light polarization to reduce the optical transmission loss from the input optical fiber to the Ge absorption region.Finally,the TPA photocurrent of the on-chip photodetector is obtained by a probe.【Results】A net photogenerated current up to 651 nA and an estimated value of responsivity greater than 10 mA/W is obtained experimentally under a 2μm wavelength optical input power of 21.9 dBm.【Conclusion】The work of this paper verifies the scientific feasibility of 2μm waveband photodetector through the TPA effect of Ge material,and provides experimentally support for the design of the 2μm wavelength band Ge-on-SOI photodetector based on TPA.