All-fibre heterogeneously-integrated frequency comb generation using silicon core fibre

Originally developed for metrology, optical frequency combs are becoming increasingly pervasive in a wider range of research topics including optical communications, spectroscopy, and radio or microwave signal processing. However, application demands in these fields can be more challenging as they require compact sources with a high tolerance to temperature variations that are capable of delivering flat comb spectra, high power per tone, narrow linewidth and high optical signal-to-noise ratio (OSNR). To date, there has not been a frequency comb technology that is able to simultaneously achieve all these requirements. This work reports the generation of a flat, high power frequency comb in the telecom band using a 17-mm fully-integrated silicon core fibre (SCF) as a parametric mixer. Our all-fibre, cavity-free source combines the materials benefits of planar waveguide structures with the advantageous properties of fibre platforms to achieve a 30 nm bandwidth comb source containing 143 tones with <3 kHz linewidth, 12 dB flatness, and >30 dB OSNR over the entire spectral region. The unique combination of technical features offered by this SCF-based source opens a path towards a new class of high-performance frequency comb generators for communications and signal processing applications.