Near-infrared ultrafast third-order nonlinear optical response of 2D NbS₂, NbSe₂, ZrTe₂, and MoS₂

By employing the optical Kerr gate technique at 800 nm with 180 fs pulses at 76 MHz, we evaluated the third-order nonlinear optical response of two-dimensional (2D) semiconducting MoS₂, semimetallic ZrTe₂, and metallic NbS₂ and NbSe₂. The modulus of the nonlinear refractive index was measured to range from 8.6 × 10^-19 m²/W to 5.3 × 10^-18 m²/W, with all materials' response time limited by the pulse duration. The physical mechanism to explain the ultrafast response time's origin considers the nature of the 2D material, as will be discussed.