Waveguide behavior of Distributed Bragg Reflectors probed by polarization-modulated near-field optical microscopy

Distributed Bragg Beffectors (DBRs) have been found to be very effective in increasing the efficiency of light emitting diodes and semiconductor laser devices, By using polarization-modulated scanning near-field optical microscopy (PM-SNOM), we investigate the optical response to different illumination polarization states of a DBR. structure that consists of a, stack of quarter wavelength thick slabs of dielectrics with alternating high and low refractive index. The DBR has been optically characterized in the near-field at different wavelengths in illumination- and in collection- mode with light excitation orthogonal to the probe axis, for fixed as well as for modulated polarization. We have found that the optical signal does not follow the morphological structure of the slabs, as expected but it shows a different spatial periodicity related to the excitation properties and to the interplay of the different DBR. planes.