This dataset contains experimental results supporting the research article titled 'Optical activity in third-harmonic Rayleigh scattering: a new route for measuring chirality'.

The 'Linear_CD' folder contains results of chiral optical (chiroptical) characterisation in the linear optical regime of the left-handed (LH) and right-handed (RH) Ag nanohelices dispersed in a solvent (1 mM aqueous trisodium citrate). Spectra of the solvent were measured first. These reference measurements were then automatically subtracted from the circular dichroism spectra of the samples. Each sample was measured in two wavelength ranges (indicated in the file name). A different detector was used for each of the ranges.

The 'Power_dependence' folder contains measurements of third-harmonic Rayleigh scattering (THRS) intensity as a function of incident power. The sample is specified in the file name. The text files contain four columns. The first column specifies the incident power. The second column specifies the angle of the quarter-wave plate (QWP). QWP angles equal to 45 deg and 225 deg correspond to incident left circularly polarised light; QWP angles equal to 135 deg and 315 deg correspond to incident right circularly polarised light. Gated photon counting was used. The third column (Count A) contains the number of counts detected when the optical chopper let the laser beam through. The fourth columns (Count B) contains the number of counts detected with the laser beam blocked, i.e. ambient counts and noise.

The folder called 'Emission_spectra' contains measurements of nonlinear emission under illumination with 1065-nm, 1095-nm, and 1125-nm light (as specified in the file name). Both LH and RH nanohelices were measured. The text files contain four columns. The first column specifies the bandpass filter placed in front of the detector. The filter name is in the form of: EO - centre wavelength in nm - full-width at half-maximum in nm. The remaining columns have the same meaning as in the 'Power_dependence' folder.

The folder called 'THRS_polarisation' contains measurements of THRS intensity for two polarisations of the incident light and multiple angles of the analysing quarter-wave (AQWP). '45' or '135' after 'QWP' in the file name indicate the orientation of the quarter-wave plate in the illumination arm of our experimental setup. '45' and '135' correspond to left and right circular polarisation, respectively. The number after 'AQWP' in the file name represents the angle of the analysing quarter-wave plate. An angle of 0 degrees means the fast axis of the wave plate was horizontal. The .shg files are text files containing two columns. The second column contains the measured TH intensity in counts/second.

The folder called 'Forward_emission' contains measurements of third-harmonic intensity as a function of incident power in the forward emission configuration. The number after 'QWP' in the file name specifies the orientation of the quarter-wave plate in the illumination arm of our experimental setup. QWP angles equal to 45 deg and 225 deg correspond to incident left circularly polarised light; QWP angles equal to 135 deg and 315 deg correspond to incident right circularly polarised light. The incident power is specified in the file name. The .shg files are text files containing two columns. The second column contains the measured TH intensity in counts/second.

The folder called 'Lumerical_simulations' contains the raw data text file output from Lumerical FDTD of the E-field strength upon illumination with 365-nm and 1095-nm light. 'Orientation_001' corresponds to light propagating along the x-axis, 'Orientation_002' to light propagating along the y-axis, and 'Orientation_003' to light propagating along the z-axis. 'RHL' in the folder name stands for right handed circularly polarised light and 'LHL' for left handed circularly polarised light.