METHOD FOR MEASURING DIFFERENCE OF EQUIVALENT REFRACTIVE INDEX BETWEEN TE AND TM WAVES

摘要

PURPOSE:To make a high-precision measurement, possible, by exciting simultaneously optical waveguide modes (TE waves and TM waves), which have oscillation field components orthogonal to each other, on a thin film and discharging these waves from the end face of the thin film to detect the phase difference. CONSTITUTION:A thin film 2 is irradiated with the laser light of a linearly polarized light from a light source 3 through a 1/2 wavelength plate 4 and a prism 5. The light discharged from an optically polished end face 6 becomes an elliptically polarized light- and a beam spread in the thickness direction. This beam is converted to a beam with TE waves and TM waves converged through a cylindrical lens 7 and is subjected to phase compensation through a compensating plate 8 to become a 45 deg. linearly polarized light. The light passing through an analyzer 9 which is preliminarily set so that the 45 deg. linearly polarized light is extinguished is detected by a photodiode 10, and the compensating plate is so adjusted that this detection sensitivity is minimum. The variation of a phase compensation quantity phi due to the compensating plate 8 to a length between the prism 5 and the exit end face 6, namely, dphi/dl is obtained to lead out the difference of equivalent refractive index between TE and TM waves.