A highly-compact optical amplifier for densely-integrated communications systems

我们提出了一种新的甚小形状因子（VSFF）光放大器的芯片上。当前的VSFF放大器限于半导体光放大器（SOA），其使用昂贵的材料并且受到引起信号串扰的高噪声和非线性的阻碍。作为领先的替代技术，掺铒光纤放大器（EDFA）可提供低噪声和高增益，以实现光学系统的高性能。 然而，用于构建这种放大器的石英光纤大约有几米长，并且在缠绕时不能弯曲得太紧，从而限制了设备的整体尺寸。一种潜在的替代方案是掺铒波导放大器（EDWA），其中掺铒波导在低成本硅衬底上制造，由于使用具有高折射率的薄膜材料并且其允许比二氧化硅更高的铒掺杂剂浓度，因此允许大规模生产和尺寸的数量级减小。我们最近改进了EDWA使用一种新的平台的基础上混合掺铒碲酸盐玻璃和氮化硅波导。我们的平台消除了过去阻碍EDWA商业化的挑战，包括使用成熟的氮化硅技术的可重复制造方法，以及通过高折射率掺杂碲酸盐玻璃实现的紧凑外形的高增益。我们已经证明了使用该平台的光学增益高达5 dB，显示了其可行性。该项目中有待解决的其余挑战包括：a）在较长的螺旋波导中展示高达20 dB的更高光增益; B）将光泵浦和信号光的光纤-芯片耦合损耗降低至<1 dB，以提高效率和噪声性能; c）展示在同一芯片上具有光泵浦和信号多路复用的封装组件以及紧凑外形的输入和输出端口。这种紧凑型EDWA将在光通信网络、数据中心、高性能计算、人工智能、空间通信以及自动驾驶车辆的检测和测距中具有广泛的应用。

We propose to develop a new very-small-form-factor (VSFF) optical amplifier on a chip. Current VSFF amplifiers are limited to semiconductor optical amplifiers (SOAs), which use costly materials and are hampered by high noise and nonlinearities which induce signal crosstalk. The leading alternative technology, erbium-doped fiber amplifiers (EDFAs) offer low noise and high gain for high performance in optical systems. However, the silica optical fiber used to build such amplifiers is on the order of meters long and cannot be bent too tightly when wrapped up, thereby imposing a limit on the overall size of the device. A potential alternative is the erbium-doped waveguide amplifier (EDWA), in which an erbium-doped waveguide is fabricated on a low-cost silicon substrate, allowing for large-scale production and orders of magnitude reduction in size because of the use of thin film materials with high refractive index and which allow for higher erbium dopant concentrations than silica. We have recently improved EDWAs using a novel platform based on hybrid erbium-doped tellurite glass and silicon nitride waveguides. Our platform removes past challenges with EDWAs which have prevented their commercialization, including reproducible fabrication methods using well-established silicon nitride technology, and high gain in a compact form factor enabled by the high refractive index doped tellurite glass. We have demonstrated optical gain of up to 5 dB using this platform, showing its viability. The remaining challenges to be addressed in this project include a) demonstrating higher optical gain of up to 20 dB in longer spiral waveguides; b) reducing the fiber-chip coupling loss to < 1 dB for optical pump and signal light to improve efficiency and noise performance; c) demonstrating a packaged component with optical pump and signal multiplexing on the same chip and input and output ports in a compact form factor. Such compact EDWAs will have wide-ranging applications in optical communications networks, data centers, high-performance computing, AI, space communications, and detection and ranging in self-driving vehicles.