Third-harmonic Mie scattering from semiconductor nanohelices

Third-harmonic Mie scattering optical activity from suspensions of semiconductor (CdTe) nanostructured helices is observed, opening ways for chiroptical characterization of semiconductor and other chiral non-metallic particles in volumes potentially of the order of 10(-17) m(3). Chiroptical spectroscopies provide structural analyses of molecules and nanoparticles but they require sample volumes that are incompatible with generating large chemical libraries. New optical tools are needed to characterize chirality for the ultrasmall (<1 mu l) volumes required in the high-throughput synthetic and analytical stations for chiral compounds. Here we show experimentally a novel photonic effect that enables such capabilities-third-harmonic Mie scattering optical activity-observed from suspensions of CdTe nanostructured helices in volumes <<1 mu l. Third-harmonic Mie scattering was recorded on illuminating CdTe helices with 1,065, 1,095 and 1,125 nm laser beams and the intensity was around ten-times higher in the forward direction than sideways. The third-harmonic ellipticity was as high as 3 degrees and we attribute this effect to the interference of chiral and achiral effective nonlinear susceptibility tensor components. Third-harmonic Mie scattering on semiconductor helices opens a path for rapid high-throughput chiroptical characterization of sample volumes as small as 10(-5) mu l.

Automated summary

The study demonstrates the third-harmonic Mie scattering optical activity in suspensions of semiconductor nanostructured helices, allowing for chiroptical characterization of sample volumes as small as 10(-17) m(3). The new experimental results open up possibilities for high-throughput chiroptical characterization of chiral compounds in ultrasmall volumes.