Optimized design and fabrication of nanosecond response electro-optic switch based on ultraviolet-curable polymers

A nanosecond response waveguide electro-optic （EO） switch based on ultraviolet （UV） sensitive polymers of Norland optical adhesive （NOA73） and Dispersed Red 1 （DR1） doped SU-8 （DR1/SU-8） is designed and fabricated. The absorption properties, refractive indexes, and surface morphologies of NOA73 film are characterized. The single-mode transmission condition is computed by the effective index method, and the percentage of optical field distributed in EO layer is optimized to be 93.78 %. By means of spin-coating, thermal evaporation, photolithography, and inductively coupled plasma etching, a Mach-Zehnder inverted-rib waveguide EO switch with micro-strip line electrode is fabricated on a silicon substrate. Scanning electron microscope characterization proves the physic-chemical compatibility between NOA73 cladding and DR1/SU-8 core material. The optical transmission loss of the fabricated switch is measured to be 2.5 dB/cm. The rise time and fall time of switching are 3.199 ns and 2.559 ns, respectively. These results indicate that the inverted-rib wave- guide based on UV-curable polymers can effectively reduce the optical transmission loss and improve the time response performance of an EO switch.