Advanced Spectroscopy

Photoluminscence (PL)

PL is a technique to measure the optical bandgap in insulators and semiconductors. The incident light pumps the electron from the valence bands to the high-energy conduction bands. These hot carriers relax to the band edge and then recombine, resulting in emission PL spectra.

Raman spectroscopy

Raman spectroscopy is a technique to measure inelastic scattering. The incident photons interact with the materials and transfer energy with them. We measure the outgoing photons and analyze them spectrally. The spectra tell us the scattering processes, such as light-phonon scattering.

Second harmonic generation (SHG)

SHG is a nonlinear optical process that combines two incident photons and generates one photon with double energy. The cross-section of the SHG process is governed by "second-order nonlinear susceptibility", which is strongly related to the material symmetry.