Enhanced Optical Third-Harmonic Generation in Phase-Engineered MoTe<sub>2</sub> Thin Films
Seongju Ha, Hyeonkyeong Kim, Hyun-Jun Nam, Jungseok Choi, Kwanbyung Chae, Jae‐Ung Lee, Ji‐Yong Park, Youngdong Yoo, Dong‐Il Yeom
Abstract
Molybdenum ditelluride (MoTe2) is a relatively unexplored layered transition metal dichalcogenide in nonlinear optics. Several recent studies have shown that MoTe2 has strong second-order optical nonlinearities originating from tellurium atoms. However, the third-order optical nonlinearities of MoTe2 have not been explored yet, except for the nonparametric saturable absorption process. Here we report the enhanced optical third-harmonic generation in phase-engineered MoTe2 thin films. MoTe2 films, including 2H and 1T′ phases simultaneously, are synthesized by the flux-controlled phase-engineering method, and their nonlinear response is characterized. We observe that the 2H-MoTe2 film exhibits up to a 15-fold stronger nonlinear signal than that of the 1T′-phase film. The estimated third-order effective nonlinear susceptibility of 2H-MoTe2 is 9.3 × 10–19 m2 V–2 maximum, which is larger than highly nonlinear layered materials such as molybdenum disulfide. Our MoTe2 film synthesized with the desired phase over a large area will be a potential building block for ultrathin nonlinear photonics.