Preparation of a planar multimode interference coupler with a graded-index profile using polysilane with photobleaching properties

To investigate the viability of a planar graded-index multimode waveguide fabricated using a new method (to our knowledge) employing polysilane with photobleaching properties, we designed a planar two-way multimode power splitter based on multimode interference, with a core possessing a vertically parabolic and horizontally uniform index profile. We carried out mode propagation analysis using the Marcatili model and optimization using a three-dimensional beam-propagation method. The prototype was fabricated by means of multiple dicing after UV exposure and heat treatment in air. Index profile measurements using a special end-face reflection method showed it to have a vertically graded-index profile with relative index difference of 0.0456. Output beam profile observation using a CCD camera showed that it successfully divided the beam planewise.