Optical waveguide lightmode spectroscopy (OWLS)

OWLS is an optical technique that enables the in situ study of macromolecules’ adsorption on a planar waveguide.

For a discrete coupling angle, the laser beam is coupled into the waveguide via a diffraction grating and the propagation of the totally reflected light is monitored in real time. The adsorption of molecules disrupts the evanescent field and causes changes in the effective refractive index of the guided transverse electric (NTE) and magnetic (NTM) modes.

These measurements make it possible to quantify the refractive index and thickness of the adsorbed layers.