Tuning the performance of polymeric microring resonator with femtosecond laser

Abstract

Microring resonator realized by femtosecond laser-induced two-photon photopolymerization in photoresist SU-8 and the factors influencing the performance of the microring resonator are demonstrated in this study with unique advantages of flexibility, high precision, and possible three-dimensional fabrication. By varying the laser parameters, it is possible to tune the performance of the polymeric microring resonator through the adjustment of different specifications, including the magnitudes of the radius and cross section. It is revealed that the free spectral range of the microring resonator is closely related with the parameters such as ring radius, resonance wavelength, cross section of the microring, and the polarization of the light. The ring resonator with a radius of 60μm shows a free spectral range of 3.9 nm, which linearly increases as the curvature of the ring increases. Though the value of the free spectral range does not vary for a multiple microring, the full-width half-maximum of the resonance is larger for the microring resonator consisting of multiple rings. The polarization modes of the microring resonator exhibit different resonance wavelengths due to different effective refractive indices, which opens new venues for the applications of microring resonators.