Changing the colour of light in a silicon resonator

As the demand for high bandwidths in microelectronic systems increases, optical interconnect architectures are now being considered that involve schemes commonly used in telecommunications, such as wavelength-division multiplexing (WDM) and wavelength conversion1. In such on-chip architectures, the ability to perform wavelength conversion is required. So far wavelength conversion on a silicon chip has only been demonstrated using schemes that are fundamentally all-optical2,3,4,5,6, making their integration on a microelectronic chip challenging. In contrast, we show wavelength conversion obtained by inducing ultrafast electro–optic tuning of a microcavity. It is well known that tuning the parameters of an optical cavity induces filtering of different colours of light7. Here we demonstrate that it can also change the colour of light. This is an effect often observed in other disciplines, for example, in acoustics, where the sound generated by a resonating guitar string can be modified by changing the length of the strings (that is, the resonators)8. Here we show this same tuning effect in optics, enabling compact on-chip electrical wavelength conversion. We demonstrate a change in wavelength of up to 2.5 nm with up to 34% on–off conversion efficiency.