Yuzhe Xiao
The Institute of Optics
Adiabatic Wavelength Conversion in Travelling-wave and Resonant Photonic Structures
Tuesday, August 16
12:00- 1:00 PM
Goergen 101
All-optical signal processing, especially wavelength conversion plays a crucial role in modern lightwave systems. Many ways of wavelength conversion use nonlinear effects that require high power and phase matching. Recently, it was found that the spectrum of light can change inside a linear medium whose refractive index changes with time. The term adiabatic wavelength conversion (AWC) is used to describe this optical phenomenon. Methods such finite-difference time-domain (FDTD) simulations and a modal approach, have been used to study this effect. In this talk, we present a new approach for understanding AWC by developing a linear system model for the dynamic photonic structures. The model is first applied to a travelling-wave device to reveal a new physical picture of AWC: a rescaling of transit time by dynamic refractive index changes of the medium. We show that temporal changes in the refractive index not only shift the pulse spectrum but also lead to pulse compression and spectral broadening as well as to phase changes. In the optical resonators, our approach correctly predicts the spectral shift related to AWC. More importantly, it allows us to study the temporal and spectral evolution of an optical pulse that has been ignored so far. Our method is applicable to a broad range of integrated photonic structures, including silicon micro-rings and photonic crystal resonators, and is useful for applications ranging from all-optical signal processing to routing, as well as optical buffering.
