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.
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT; NRF-2019R1A2C1006119, 2019R1C1C1008070 and 2021R1A4A1032085), and by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. NRF-2021R1A6A1A10044950). This work was also supported by Institute for Information and Communications Technology Promotion (IITP) grant funded by the Korea government (MSIT) (2021-0-00185).
