Figure 2

(a) Photoluminescence signal and measured \({\chi }^{(2)}\) from monolayer MoS₂: the blue line is the measured spectrum of the photoluminescence signal (under 437 nm excitation); the red circles are \({\chi }^{(2)}\) values measured in literature¹⁶ (not in scale, magnified 20 times); the green line with dots represent our experimental data for \({\chi }^{(2)}\) measurement, where the right hand side y-axis corresponds to the real calculated value of \({\chi }^{(2)}\) in our experiment, (b) Cross-correlation measurement with 50 nm bandwidth centred around 875 nm, (c) SHG polarisation dependence measurement with a pump wavelength at 875 nm.