Adiabatic frequency conversion using the optical KERR effect

When you pluck a guitar string with your finger, a note of a certain pitch will sound from the guitar for a while. What happens if you quickly change the tension of the string while the note continues to sound? As you can imagine, the pitch of the note emitted from the guitar will change as the tension changes. Physically, this can be explained by the fact that the natural frequency of the string changes as the tension changes.

In fact, a similar phenomenon can also be observed in a micro optical resonator. When the resonant frequency of a micro optical resonator containing light is quickly shifted, the frequency of the light itself in the resonator also changes along with the resonant frequency shift. This phenomenon is known as adiabatic frequency conversion. Until now, most adiabatic wavelength conversion has been achieved by shifting the resonance frequency of a resonator, such as a photonic crystal resonator, through the effect of a carrier. However, the use of carriers has the problems that temporal control is difficult due to the finite diffusion time of the carriers and that the loss of the resonator increases as the carrier density increases. In this study, we realized a low-loss and highly controllable adiabatic frequency conversion by controlling the resonance frequency of a glass resonator called a silica micro optical resonator using the optical Kerr effect, a lossless and instantaneous response technique.