Polymer-based racetrack microring resonator fabricated on micropillars

Abstract

There has been a rapid technological development in the field of polymer-based photonic devices in recent times due to advanced fabrication techniques. Though, effective way to couple the light into the polymer devices is a difficult task. In this paper, we propose a novel technique to overcome the challenges in coupling the light from an optical fibre to a polymer-based photonic device. Unlike in silicon photonic devices where usually grating couplers are used to couple light, the same technique is quite ineffective to couple the light in polymer-based photonic devices due to small refractive index contrast and poor confinement. The proposed device has been theoretically analyzed using Lumerical MODE Solutions in the wavelength range of 1520-1580 nm. The proposed structure consists of a conventional 4-port, add-drop, racetrack resonator with a high-quality factor of 5316.7 for the notch at 1527.8 nm on top of cylindrical pillars of radius 6 μm. The free spectral range of the device is 11.42 nm. Two-photon polymerization based direct laser writing technique has been used to fabricate the device, using IP-DIP polymer. The micro-pillars provide a degree of freedom and lift the entire resonator structure to the desired height, thereby relaxing the vertical mismatch between fibre and the resonator. This method provides a simple method to couple light without using grating couplers or etching the fibre.