Direct comparison of second and third harmonic generation in mono- and few-layer MX2 (M=Mo, W; X=S, Se) by multiphoton microscope

摘要

We present a comprehensive study of second harmonic generation (SHG) and third harmonic generation (THG) from single- and few-layer transition metal dichalcogenides (MoS2, MoSe2, WS2 and WSe2). We measure SHG and THG from these materials with a multiphoton microscope with linearly polarized 1560 nm femtosecond excitation. We find that SHG from monolayer MoSe2 under 1560 nm excitation is more than four times stronger than that of other studied materials. This can be attributed to resonant enhancement of SHG in MoSe2.