Multistage polymeric lens structures integrated into silica waveguides

A waveguide lens, composed of multistage polymer-filled thin grooves in a silica planar lightwave circuit (PLC) is proposed and a low-loss structure has been designed. A waveguide lens in a silica slab waveguide has been fabricated using reactive ion etching (RIE) and formed by filling with polymer. Both an imagding optical system and a Fourier-transform optical system can be configured in a PLC using a waveguide lens. It renders the PLC functional and its design flexible. To obtain a shorter focal length with a low insertion loss, it is more effective to use a multistage lens structure. An imaging optical system and a Fourier-transform optical system with a focal length of less than 1000 um were fabricated in silica waveguides using a multistage lens structure. The lens imaging waveguides incorporate a 16-24-stage lens, with insertion losses of 4-7dB. A 4 × 4 optical coupler, using a Fourier-transform optical system, utilizes a 6-stage lens with losses of 2-4dB.