Fast Wavelength Locking of a Microring Resonator

Microring resonator devices require thermal initialization to match their intended operating wavelengths in a process called wavelength locking. We use the dither technique, where we apply a small periodic signal to the microring's integrated heater, to demonstrate reliable wavelength locking of a microring resonator filter to an operating wavelength at a wavelength shift rate of 0.012 nm/μs, an order of magnitude faster than previous demonstrations. We also identify and characterize fundamental speed limits of the wavelength locking process, showing that the integrated-heater bandwidth is the limiting factor.