Near field measurements of optical channel waveguides and directional couplers

Abstract

Near field microscopy is used to investigate the guided mode intensity distribution of optical channel waveguides and directional couplers with subwavelength spatial resolution. The directional coupler consisted of two single mode optical ridge channel waveguides formed with silicon nitride deposited on a lower cladding layer of SiO2 on a silicon substrate. A near field measurement of the guided mode intensity profile in the transverse direction parallel to the waveguide surface was performed across one of the optical channel waveguides. These variations are compared with model calculations. Similar transverse measurements of light propagating through a directional coupler were performed at many locations along the coupler, providing a view of the evolution of optical power transfer.