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Ultra-low-loss optical delay line on a silicon chip

2012; Nature Portfolio; Volume: 3; Issue: 1 Linguagem: Inglês

10.1038/ncomms1876

2041-1723

Hansuek Lee, Tong Chen, Jiang Li, Oskar Painter, Kerry J. Vahala,

Advanced Fiber Laser Technologies

Light propagation through an optical fibre causes a long, non-resonant (true) time delay used in numerous applications. In contrast to how it is deployed in optical communication systems, fibre is coiled in these applications to reduce footprint. This is a configuration better suited for a chip-based waveguide that would improve shock resistance, and afford the possibility of integration for system-on-a-chip functionality. However, integrated waveguide attenuation rates lag far behind the corresponding rates of optical fibre, featuring attenuation many orders larger. Here we demonstrate a monolithic waveguide as long as 27 m (39 m optical path length), and featuring broadband loss rate values of (0.08±0.01) dB m−1 measured over 7 m by optical backscatter. Resonator measurements show a further reduction of loss to 0.037 dB m−1, close to that of optical fibres when first considered a viable technology. Scaling this waveguide to integrated spans exceeding 250 m and attenuation rates below 0.01 dB m−1 is discussed. Fibre-optic waveguides are used to provide timing delays for different sensing and signal processing applications, but their transfer to on-chip platforms is a challenge. Here low-loss delay lines based on whispering-gallery spiral waveguides up to 27 m long are produced, presenting a scalable alternative.