Fig. 3: Emission characteristics of individual sg-QDs.

a On-time fractions, (b), histogram of g⁽²⁾(0) (upper panel) derived from the second-order correlation function, g⁽²⁾(τ), and a representative graph (lower panel), and (c), emission linewidths of PL spectrum components, 1S_HX,em (upper panel) and 1S_LX,em (lower panel), of individual CdSe (r = 2.5 nm)-ZnSe sg-QDs as a function of the effective compressive strain imposed by ZnSe of varying shell thicknesses (0 nm ≤ H ≤ 5.0 nm). The g⁽²⁾(τ) in (b) is obtained from a CdSe (r = 2.5 nm)-ZnSe (H = 5.0 nm) sg-QD and the mean value of g⁽²⁾(0) is 0.16. In (a, c), symbols are averages, error bars are standard deviations, and shaded regions are connecting the error bars. d Schematic illustration of the optical measurement setup. The emission from a single sg-QD, \({{{{{{\rm{I}}}}}}}_{0}\), passes through a half-wave plate (HWP), which rotates the polarization direction of the light, and a Wollaston prism (WP), which splits the emission into two linearly polarized beams with orthogonal polarization (\({{{{{{\rm{I}}}}}}}_{\parallel }\) and \({{{{{{\rm{I}}}}}}}_{\perp }\)). e 2D contour plots showing PL spectra (\({{{{{{\rm{I}}}}}}}_{0}\), \({{{{{{\rm{I}}}}}}}_{\parallel }\) and \({{{{{{\rm{I}}}}}}}_{\perp }\) from the top) of an individual sg-QD at varying rotation angles from 0 to 360 degrees (100 ms per each degree) and (f), averaged PL spectra in (e). 1S_HX,em and 1S_LX,em are indicated in each panel. g PL spectra of \({{{{{{\rm{I}}}}}}}_{\parallel }\) (upper panel) and \({{{{{{\rm{I}}}}}}}_{\perp }\)(lower panel) at 0 degree (the grey box in (e)). Each spectrum is fitted with double Lorentzian curves to decouple 1S_HX,em (red line with shading) and 1S_LX,em (blue line with shading). h Rotation angle dependent degree of polarization (DOP) of PL (black open circle), and its components, 1S_HX,em (red open circle) and 1S_LX,em (blue open circle). Each DOP is fitted with a sine function (solid lines in corresponding colors). i Polar graph of 1S_HX,em (red) and 1S_LX,em (blue) divided by the sum of PL intensity. The 1S_LX,em intensity is multiplied by 2 for better visibility.