Electrically Tunable Strong Optical Nonlinearity in Near‐Infrared by Coupled Metallic Quantum Wells

Abstract An electrically tunable nonlinear optical device working at near‐infrared wavelength is theoretically and experimentally demonstrated. Ultrahigh optical second‐order nonlinearity from titanium‐nitride‐based coupled metallic quantum wells can be electrically tuned by external electric field. Tunability of second‐order susceptibility χ⁽²⁾ reaches a 63% modulation depth with an average tunability of 10.5% per volt. In addition, electro‐optic modulation of second‐harmonic signal is presented by continuous tuning of χ⁽²⁾ over a long period of time with high stability. These results provide a new material platform with actively controllable strong nonlinearity for future nonlinear photonic systems, such as ultra‐compact opto‐electronic modulation devices and reconfigurable nonlinear metamaterials and metasurfaces.