First-Order Forward and Backward Quasi-Phase Matched Second Harmonic Generation in Silicon-Organic Hybrid Structures

Abstract

We propose and design a high-efficiency forward and backward second harmonic generation (SHG) in nonlinear polymer filled silicon slot waveguide known as silicon-organic hybrid (SOH) waveguides. The spatial distribution of second-order nonlinearity, χ(2) , of waveguide is altered by periodically poling of nonlinear polymer to achieve quasi-phase matching (QPM) between fundamental frequency and second harmonic waves. The simulations show that first-order QPM SHG with high conversion efficiency of η ≍ 7.2% can be achieved in the optimized structure with relatively small input power of 25 mW. This level of improvement is the result of high confinement of SOH waveguide as well as possible fabrication of very small period length in silicon photonics which could not be realized in traditional nonlinear materials such as LiNbO3. Our simulation results show ∼17% efficiency with only 25 mW input power for forward SHG being comparable to the other platforms even with smaller device length and lower pump power. We expect this device will open up its application in the fields of all-optical signal processing, optical (mirrorless) parametric amplification, low-noise detection of mid-IR signal in near-IR windows, and mid-IR sources.