Second Harmonic Generation (SHG) is a second-order nonlinear optical effect that occurs only in noncentrosymmetric media. This inherent selectivity allows to probe various noncentrosymmetric structures such as crystals, collagen, microtubules, and other ordered structures. SHG is also active at interfaces where the symmetry is broken by the interface that is located between isotropic media. This allows SHG to be surface specific, i.e., light can be generated exclusively at the interface. SHG is thus an ideal method to probe aqueous interfaces, biological membranes, and semiconductor surfaces.


  • Detection of sparse crystals <5 nm detection limit
  • Imaging of crystals and aggregates
  • Detection of the solubility limit of drug-screening compounds
Technological Application Crystallization And Aggregation
Technological Application Surface Electrostatic

(Left) Using water as a label-free probe of membrane electrostatics, (Right) Water molecules at the membrane interface are oriented by surface charge providing label-free contrast. Read about the article here.


  • Imaging of electrostatic potential with 300 nm spatial and 100 ms temporal resolution.
  • Measurement of the surface potential of particles, droplets, and liposomes with > 30 nm size range.
  • Water structure at interfaces.


Particles, droplets, and liposomes:

  • Surface chemical structure of objects
  • Protein, peptide, macromolecule interaction
  • All vibrational modes: 1000-4000 cm-1
Technological Application Surface Chemistry In Solution