Broadband mid-infrared light sources are highly desired for wide-ranging applications that span free-space communications to spectroscopy. In recent years, silicon has attracted great interest as a platform for nonlinear optical wavelength conversion in this region, owing to its low losses (linear and nonlinear) and high stability. However, most research in this area has made use of small core waveguides fabricated from silicon-on-insulator platforms, which suffer from high absorption losses of the use of silica cladding, limiting their ability to generate light beyond 3 µm. Here, we design and demonstrate a compact silicon core, silica-clad waveguide platform that has low losses across the entire silicon transparency window. The waveguides are fabricated from a silicon core fibre that is tapered to engineer mode properties to ensure efficient nonlinear propagation in the core with minimal interaction of the mid-infrared light with the cladding. These waveguides exhibit many of the benefits of fibre platforms, such as a high coupling efficiency and power handling capability, allowing for the generation of mid-infrared supercontinuum spectra with high brightness and coherence spanning almost two octaves (1.6–5.3 µm).

对于跨越自由空间通信到光谱学的广泛应用，非常需要宽带中红外光源。近年来，由于硅的低损耗（线性和非线性）和高稳定性，硅作为该区域非线性光学波长转换的平台引起了极大的兴趣。但是，该领域的大多数研究都使用了由绝缘体上硅平台制成的小型芯波导，该芯波导由于使用了二氧化硅包层而遭受了高吸收损耗，从而限制了它们产生超过3 µm的光的能力。在这里，我们设计并演示了一个紧凑的硅芯，包覆石英的波导平台，该平台在整个硅透明窗口内的损耗均很小。波导由硅纤芯纤维制成，该纤芯经过渐缩以达到工程模态特性，以确保在纤芯中进行有效的非线性传播，同时使中红外光与包层之间的相互作用最小。这些波导具有光纤平台的许多优点，例如高耦合效率和功率处理能力，可以生成具有近两个八度音阶（1.6-5.3 µm）的高亮度和相干性的中红外超连续谱。