Micro/nanoscale self-aligned optical couplings of the self-organized lightwave network (SOLNET) formed by two-photon photochemistry

Abstract

To solve the coupling issue in optical systems, we previously proposed a coupling method based on the selforganized lightwave network (SOLNET) formed by self-focusing in photo-induced refractive-index increase (PRI) materials such as photopolymers. SOLNETs are formed by an attractive force between light beams, providing Optical Solder that enables self-aligned couplings between optical devices, even if misalignments and core size mismatching exist. In the present work, in order to extend the lateral misalignment tolerance between nanoscale waveguides and between microscale and nanoscale waveguides, we propose the two-photon SOLNET, which is formed using twophoton photochemistry. Simulations based on the finite-difference time-domain method reveal that when write beams with wavelengths of 500 and 600 nm are respectively introduced into a two-photon PRI material from two 600-nm-wide waveguides opposed with a 32-μm distance and a 4200-nm lateral misalignment, a two-photon SOLNET is formed between them. The misalignment tolerance is 7-times larger than that in conventional one-photon SOLNETs, and 1.4- times larger than that in two-photon SOLNETs formed using 400-nm and 780-nm write beams. The two-photon SOLNET extends the lateral misalignment tolerance to <1000 nm for couplings between a 3-μm -wide waveguide and a 600-nm-wide waveguide, exhibiting a function of mode-size convertors. Preliminary experiments demonstrate that the two-photon SOLNETs are formed between multimode optical fibers by introducing a 448-nm write beam and a 780-nm (or 856-nm) write beam from the fibers into a photosensitive organic/inorganic hybrid material, SUNCONNECT®, with doped camphorquinon (or biacetyl).