We report the experimental observation and analysis of optical second-harmonic generation in the 3R and 2H polytypes of molybdenum disulfide (MoS<sub>2</sub>) by a fundamental excitation wavelength of 1064 nm. We include an extension from the literature to account for multiple reflections of the fundamental, anisotropic optical constants, and strong absorption of the second harmonic to deduce the second-order nonlinear dielectric susceptibilities. We observe a bulk nonlinearity of |d<sub>21</sub>|=500±200 pm/V for 3R-MoS<sub>2</sub>. The absence of a signal from 2H-MoS<sub>2</sub>, a centrosymmetric stacking polytype, is consistent with |d<sub>eff</sub>|<5×10<sup>−2</sup> pm/V.
© 1998 Optical Society of America
G. A. Wagoner, P. D. Persans, E. A. Van Wagenen, and G. M. Korenowski, "Second-harmonic generation in molybdenum disulfide," J. Opt. Soc. Am. B 15, 1017-1021 (1998)