The path toward an even faster Internet has been blocked by energy consumption and cost. The optical spectrum is a limited resource, as as internet traffic has increased dramatically, bandwidth has become more precious. To maximize the power and cost efficiency of communication, optical networks must be able to flexibly allocate bandwidth, giving each customer only what they need at any given time. We are developing nano-photonic devices and systems for flexile optical networking. For example, we recently demonstrated a widely bandwidth tunable filter using grating-assisted contra-directional coupler on a silicon chip. It gives a network controller the freedom to select the frequency and bandwidth for each channel and change them on the fly. Its performance is comparable to the best bench-top systems, but at a fraction of the size and cost. This work was featured by OSA (Read more; Paper).