POLARIZATION MODULATION LASER-SCANNING MICROSCOPY - A POWERFUL TOOL TO IMAGE MOLECULAR-ORIENTATION AND ORDER

To image the orientational order in a broad class of biological and ma nufactured materials, a new microscope has been developed that integra tes laser scanning microscopy with polarization modulation polarimetry . Polarimetry allows quantitative characterization of the molecular or ientation and the degree of order through characterization of optical anisotropy. Combined with laser scanning microscopy, it is used here t o image the anisotropy with high spatial resolution, sensitivity, and speed. The design of the microscope is presented; and the vast improve ment in sensitivity achieved using PM-LSM over conventional polarizati on microscopy is illustrated by imaging the linear dichroism of ultrat hin Langmuir-Blodgett polymer films. PM-LSM allows imaging of the magn itude and Orientation of linear dichroism in films as thin as three mo lecular layers (similar to 66 Angstrom) at high resolution by rasterin g a diffraction limited spot of laser light across the sample. The rat e of image acquisition is over 2000 pixels/s, two to three orders of m agnitude faster than the previous methods of imaging optical anisotrop y.