Investigation of 2H/1T/1T′ phase MoS2 optical nonlinearity

Abstract

2H and 1T/1T′ molybdenum disulfide (MoS₂) are typical phases that can be found in crystalline and thin film materials. In this work, by controlling the atmosphere during thin film chemical vapor deposition, 2H or 1T/1T′ phase MoS₂ are grown separately. Additionally, by employing the Z-scan technique, the phase-dependent optical nonlinearity of MoS₂ is observed and investigated. The 2H phase-dominated few-layered MoS₂ shows clear reversed saturable absorption with a peak intensity reaching \(3.3 \, \text{GW}/{\text{cm}}^{2}\) 3.78 GW/cm², indicating extra higher-order nonlinear absorption. In contrast with the 2H phase, dominant single photon absorption is observed in the 1T/1T′ phase MoS₂. In addition, the nonlinear refractive index (n₂) of the two phases is characterized, exhibiting values of 1.82 × 10^–10 cm²/W (1T/1T′ phase) and − 4.82 × 10^–10 cm²/W (2H phase). This is the first time that the phase-dependent optical nonlinearity of MoS₂ has been distinguished. Meanwhile, the proposed methodology not only provides information on the differences between the phases but also serves as a guide for determining suitable phases in specific applications.