Three-Dimensional Optical Circuits Consisting of Waveguide Films and Optical Z-Connections

Two types of three-dimensional (3-D) optical circuits based on waveguide films are proposed and experimentally demonstrated. Type 1 is "Stacked waveguide films with 45deg mirrors". Waveguide films with 70-mum-thick undercladding layers and 32-mum-wide cores with air cladding are fabricated by the built-in mask method using photo-definable materials. The films are stacked by contacting their undercladding layers. Optical Z-connections are formed by aligning the 45deg mirrors in upper and lower films. The mirror-to-mirror distance is ~170 mum. When a probe beam of 650 nm or 1.3 mum in wavelength is introduced into input in the first film, it is transmitted to the second film through optical Z-connection and is observed at output. Loss at the optical Z-connection for 1.3-mum wavelength is ~14 dB, which might be due to leakage of probe beams reflected from the mirror with large diverging angles. Type 2 is "Waveguide films with vertical waveguides". After coating a photo-refractive layer of 500-mum thickness on the back of a cladding layer of a waveguide film, a 405-nm wavelength write beam is introduced into input. Then, a vertical waveguide of 3-D self-organized lightwave network (3-D SOLNET) is grown in the photo-refractive layer above a 45deg mirror. A probe beam guided in the vertical waveguide is observed with a beam size close to that in the core of the waveguide film. Loss reduction at the optical Z-connection is expected by combining optical circuits of Types 1 and 2 to insert the 3-D SOLNET between waveguide films as well as by decreasing cladding layer thicknesses