The concept of synthetic dimensions in photonics has attracted rapidly growing interest in
the past few years. Among a variety of photonic systems, the ring resonator system under
dynamic modulation has been investigated in depth both in theory and experiment and has
proven to be a powerful way to build synthetic frequency dimensions. In this Tutorial, we start
with a pedagogical introduction to the theoretical approaches in describing the dynamically
modulated ring resonator system and then review experimental methods in building such a …