All-optical image processing with cavity type II second-harmonic generation

High-efficiency second-harmonic generation in doubly-resonant χ(²) microring resonators

By directly simulating Maxwell's equations via the finite-difference time-domain (FDTD) method, we numerically demonstrate the possibility of achieving high-efficiency second harmonic generation (SHG) in a structure consisting of a microscale doubly-resonant ring resonator side-coupled to two adjacent waveguides. We find that ≳ 94% conversion efficiency can be attained at telecom wavelengths, for incident powers in the milliwatts, and for reasonably large bandwidths (Q ∼ 1000s). We demonstrate that in this high efficiency regime, the system also exhibits limit-cycle or bistable behavior for light incident above a threshold power. Our numerical results agree to within a few percent with the predictions of a simple but rigorous coupled-mode theory framework.

Frequency doubling of low power images using a self-imaging cavity

A self-imaging resonator can be simultaneously resonant for many transverse modes and therefore allows cavity build-up for images of various shapes. The stability properties of such a cavity are reviewed. We have used this device for the first time to enhance the efficiency of second harmonic generation of weak images. We characterize the global and local efficiency of the second harmonic generation, and discuss its limitation due to the spatial bandwidth of the cavity and the diffraction along the crystal length.