Zemax-based optimized design of hydrogel fiber lens

In the optical fiber sensor, the signal light output from the silica fiber is transmitted to the detector, which usually needs to be coupled through the lens focusing. However, this often destroys the compactness and flexibility of the optical fiber sensor system structure. Therefore, this article proposes a hydrogel fiber optic lens solution, that is, a method that can directly focus the signal light output from the quartz fiber to the photodetector. Its bottom-up photochemical fixation method determines its flexible sexual characteristics and can meet individual needs. In this article, according to the size of the image distance, that is, the distance from the silica fiber to the detector (image distance), and the size of the spot on the detector (focal point), the radius of curvature of the polyethylene glycol diacrylate (PEGDA)-based hydrogel fiber lens and the distance from its apex to the silica fiber end face (object distance) are optimized. Through simulation, it is found that as the radius of curvature decreases, the diameter of the spot increases, and the increase of the object distance also increases the diameter of the spot, while the size of the central bright spot decreases with the decrease of the radius of curvature and the increase of the object distance. Consistent with the variation trend of the Airy disk in the simulation, it is proved that a smaller radius of curvature and a larger object distance can improve the focusing effect of the hydrogel fiber. The simulation based on ZEMAX verifies the application feasibility of this hydrogel fiber lens, which is expected to realize the integration of optical fiber sensor structure and has the potential to be applied to some fields such as industry, biology and medicine.