Optical Frequency Metrology Study on Nonlinear Processes in a Waveguide Device for Ultrabroadband Comb Generation

Abstract

Waveguide-based devices are essential for highly efficient nonlinear optical conversion. However, the nonlinearity associated with the conversion in such devices is not self-evident. The authors present a method using optical frequency metrology to reveal the nonlinearity inside a waveguide, and establish that the spectral broadening in a periodically poled lithium niobate waveguide is due to quadratic nonlinearity. They also demonstrate absolute frequency measurement using the generated ultrabroadband comb. This study will contribute to the design of chip-scale, fully integrated devices for efficient nonlinear optical conversion.