Birefringence imaging with illumination mode near field scanning optical microscope

A new optical configuration for a near field scanning optical polarized microscope with an illumination mode is reported. It uses two circularly polarized laser beams with different frequencies, which are generated by an axial Zeeman laser. A laser beam is incident on an optical fiber and is launched from the apex of a sharpened fiber probe in order to illuminate the sample. The scattered light on the surface of the sample is collected with an objective lens and goes through the optical elements of the quarter wave plate and the linear polarizer. The light from polarization devices is converted to an electric signal with a photomultiplier and fed into a lock-in amplifier. The quadrature components and intensity signal are acquired to computer, and the retardation and the azimuth angle of the birefringence are then calculated via computer. The measurement characteristic of the developed system and images of birefringence material are shown.