Near field scanning optical microscopy (NSOM) has been used to investi
gate the guided mode intensity distribution in optical channel wavegui
des, phase-matched directional couplers, and symmetric Y-junctions. A
near field measurement of the guided mode intensity profile across the
optical channel waveguide has been performed and compared with model
calculations. The near field guided mode intensity profiles above the
waveguides were measured as a function of distance along the propagati
on direction of both a directional coupler and a Y-junction, providing
a near field view of the spatial evolution of optical power in these
structures.