Germanium Mid-Infrared Integrated Photonic Circuits

该项目涉及III-V族光源与光子集成电路的集成，用于开发一个全面的中红外硅光子平台，该平台可用作气体传感器。第IV组光子学在过去十年中一直是一个新兴的研究课题，专注于开发工作在近红外（NIR）中红外（MIR）波长范围内的光子器件。然而，这项工作只集中在MIR器件的开发上，这些器件适用于许多应用，包括化学、生物和环境传感、安全、通信以及天文学。整个项目旨在实现的主要目标是开发集成光子器件，这些器件可以集成在单个硅芯片上。本报告介绍了在过去8个月内为实现这一目标而开展的工作。更具体地说，这包括用于MIR波长范围的低损耗波导的开发。这些波导使用的平台上的悬浮锗硅绝缘体（Ge-on-SOI）进行了演示。波导最初使用Lumerical Mode Solutions设计。对生长在220 nm厚的Si层和3 m厚的SiO2层（又称埋氧层）构成的SOI衬底上的400 nm和1 m厚的Ge脊形波导进行了模拟。在3.8 μ m处测得的传播损耗为16.7 dB/cm。然后，通过使用氢氟酸（HF）的湿法蚀刻步骤去除BOX来悬挂波导。通过在波导旁边设计亚波长孔来实现对BOX的访问。在去除BOX之后，观察到在3.8 _m处的传播损耗（2.82dB/cm）。测得的弯曲损耗为0.13 dB/弯曲。制备了1 mGe-on-SOI样品，并进行了测试。还研究了量子级联激光器（QCL）在Si上的集成。QCL-波导重叠分析表明，1 _m的横向失调对应于大约0.34 dB的插入损耗，对于5.5 _m的失调，插入损耗增加到10 dB。垂直失准的相应值对于1 _m为2.71 dB，对于1.9 _m为10 dB。

This project involves the integration of III-V light sources with photonic integrated circuits for the development of a comprehensive mid-infrared silicon photonic platform which can be potentially used as a gas sensor.Group IV photonics has been an emerging topic of research over the last decade which focuses on the development of photonic devices which operate in the Near-Infrared (NIR) Mid-Infrared (MIR) wavelength range. However, this work focuses only in the development of devices for MIR.These devices are suitable for numerous applications including chemical, biological and environmental sensing, security, communications, as well as astronomy. The main point which the overall project aims to achieve is the development of integrated photonic devices that can potentially be integrated on a single silicon chip.This report presents the work that has been carried out towards this aim, over the last 8 months. More specifically, this includes the development of low loss waveguides for the MIR wavelength range. These waveguides were demonstrated using the platform of suspended Germanium-on-Silicon-on-Insulator (Ge-on-SOI). The waveguides were initially designed using Lumerical Mode Solutions. The simulations were carried out for 400 nm and 1 _m thick Germanium (Ge) rib waveguides grown on an Silicon on Insulator (SOI) substrate formed of a 220 nm thick Silicon (Si) layer and a 3 _m thick Silicon Dioxide (SiO2) layer (also known as the Buried Oxide (BOX)). The measured propagation loss was 16.7 dB/cm at 3.8 _m. Then the waveguides were suspended by removing the BOX using a wet etch step with Hydrofluoric Acid (HF). Access to the BOX was achieved by designing subwavelength holes alongside the waveguides. After removing the BOX, a propagation loss of (2.82 dB/cm) at 3.8 _m was observed. The measured bend loss was 0.13 dB/bend. Samples of 1 _m Ge-on-SOI have also been fabricated and are due to be measured. Integration of Quantum Cascade Lasers (QCLs) on Si has also been investigated. A QCL-waveguide overlap analysis has been carried out showing that a lateral misalignment of 1 _m corresponds to an insertion loss of approximately 0.34 dB which is increased to 10 dB for 5.5 _m of misalignment. The respective values of the vertical misalignment are 2.71 dB for 1 _m and 10 dB for 1.9 _m.