Improvement of efficient coupling and optical resonances by using taper-waveguides coupled to cascade of UV210 polymer micro-resonators

Abstract

In this paper, we report the overall design, fabrication and optical characterization of single and multiple resonant micro-structures patterned on the UV210 polymer and shaped by adequate deep-UV lithography procedures. Various families of ring and racetrack forms are investigated with different geometrical dimensions linked to the micro-resonators and the specific taper-waveguides and gaps allowing the optimized coupling. Well defined photonic structures families in the sub-micrometer range obtained by this deep UV-light process are clearly confirmed through scanning electron microscopy. In order to evaluate and quantify the efficiency of the submicrometer coupling, the recirculation of the light and the quality of the optical resonance aspects, a global study including top view intensity imaging, spectral measurements and Fast Fourier Transform analysis is performed for all these devices based on single and multiple family resonators. The experimental TE-mode resonance transmissions reveal a complete agreement with the period of the theoretically expected resonances. A maximum value of the quality factor Q = 3.5 x 10 3 at 1035 nm with a 3.2 times higher resonance contrast is assessed for cascade of triple micro-resonators respect to the photonic devices based on only one micro-resonator. In addition, these UV210 circuits made of specific tapers coupling to cascade loops act directly on the improvement of the evanescent coupling and resonances in terms of quality factor and extinction rate, by selecting successively and more precisely the optical mode resonance. All these designs and low cost technological reproducible steps, and furthermore the devices and protocol measurements are markedly suitable for mass fabrication and metrology applications.

A laterally coupled UV210 polymer racetrack micro-resonator for thermal tunability and glucose sensing capability

“…Particularly, an improvement on the coupling mechanism makes better the performance of the microresonators: this can be achieved either by selecting alternate photonic circuit design strategies such as vertically coupled microresonators (which implies more fabrication costs), or simply by elongating the coupling region of the microresonator. 14,16 In this work, we have focused on the resonator based on UV210 photoresist, and developed through deep UV (DUV) lithography, procedures yielding a racetrack-shaped geometry with apt lateral coupling mechanisms with respect to the bus optical waveguide.…”

“…Our device was fabricated following the DUV lithography procedures and considering the UV210 photoresist handling conditions, which enable to develop OI devices in the submicrometer order. 16,23 More specifically, the 400-nm gap between the cavity and the rib waveguides ensures an apt optical coupling via an evanescent field. This gap value overcomes those discussed in previous publications, where we also observed clear resonance transmission.…”

“…This gap value overcomes those discussed in previous publications, where we also observed clear resonance transmission. 15,16 The R ¼ 50 mm radius and the Lc ¼ 60 mm coupling length are both main features characterizing the Figure 1 Schematic representation of racetrack microresonator. Parameters R, Lc and g represent, respectively, the radius, the coupling length and the distance between the rib waveguides and the microresonators geometry of a racetrack.…”

“…This result is two times higher in comparison with the previous one obtained for devices with one resonant structure developed with this photoresist, which is mainly owing to the reduced gap size value characterizing this racetrack microresonator. 16,27 Temperature sensor based on racetrack microresonator: test results…”

“…Then, the design and the overall fabrication and optical characterization of a cascade of multiple microresonators acting as modal filters have been presented. 16 In order to demonstrate the complete feasibility of the UV210 photoresist to support OI devices, this paper aims to present the first developments of this polymeric microracetrack for temperature and homogeneous glucose sensing. Section 2 briefly describes the design and fabrication of such a polymeric microracetrack.…”