Strong and Broadband Second-Order Optical Nonlinearity Through Multiple Coupled Metallic Quantum Wells

Abstract

A material system with strong and broadband optical second-order nonlinearity in the near-infrared is theoretically and experimentally demonstrated. Multiple units of TiN-based coupled metallic quantum wells with slightly shifted nonlinear response peaks are uniquely designed and epitaxially grown to form a multilayered stack. By measuring near-infrared to visible second-harmonic generation, second-order susceptibility χ (2) reaches 740 pm V -1 at 900 nm and spreads 200 nm, covering wavelength range from 800 nm to 1000 nm. Our discoveries open up the possibility to create materials with tailored optical nonlinearity, which can be valuable for building nonlinear optical devices in the fields of bioimaging, ultrafast light source generation, and quantum information technologies.