Polymer ring resonator made by two-photon polymerization and vertically coupled to a side-polished optical fiber

We have developed a novel approach for fabricating and testing optical ring resonators. Using a side-polished optical fiber and fabricating a ring waveguide directly over its core, an efficient and passive signal filter in the 1.55 um telecommunication band is created. A standard single mode optical fiber is permanently secured in an arcing groove in quartz and is side polished proximally to its core. The ring resonator is fabricated using two-photon initiated free-radical polymerization of tri-functional acrylate on low-index quartz substrate with a 100 femtosecond pulsed Ti/sapphire laser. The quartz substrate is inverted and vacuum mounted to an X-Y-Z stage so that the polymer ring waveguide can be positioned directly above the core of the fiber forming a vertically coupled ring resonator. Our technique allows infinite variation of the width, height, diameter and location (therefore the coupling strength between the fiber and the ring) of the ring resonator waveguide. This approach enables resonators to be fabricated, tested and subsequently removed multiple times on the same side-polished fiber, refining both the ring resonator geometry and materials. Because it is a fiber-based device, it possesses negligibly low optical insertion loss and can be used for fixed and tunable wavelength filters, intensity modulators, and fiber-optic sensors. Both theoretical analysis and experimental data will be presented.