UV-curable liquid-core fiber lenses with controllable focal length

Gongxun Bai,Yuen H Tsang,Xuming Zhang,Kwok Lung Jim

doi:10.1364/oe.21.005505

Abstract

Lensed fiber optics is of great importance to many applications such as optical sensing, optical coupling, laser trapping etc. In this paper we have demonstrated a unique method to fabricate liquid-core lensed fibers by filling UV curable adhesive into hollow fibers, and to control the focal length and spot size by pumping liquid into or out of the fiber end. In experiment, tuning of focal length from 2.414 to 0.810 mm has been obtained, and solidification of the adhesive core has also been carried out successfully. Further simulation suggests that the focused spot size can be reduced to <10 micron by adjusting the refractive index and fiber geometry. Such technique has the potential to manufacture custom-made solid lensed fibers and liquid-core solid-tip lensed fibers in volume at low cost. The same technique may be used for input and output coupling of optofluidic waveguides with external optical components like optical fibers and lasers.

Highlights

Liquid-core waveguide has the merit of sensitivity enhancement and is of great interest to many sensing applications such as fluorescence and Raman measurements, long-path-length UV–visible absorption/transmission, and IR spectrometry [1]
Lensed fiber optics is of great importance to many applications such as optical sensing, optical coupling, laser trapping etc
In this paper we have demonstrated a unique method to fabricate liquid-core lensed fibers by filling UV curable adhesive into hollow fibers, and to control the focal length and spot size by pumping liquid into or out of the fiber end

Summary

Introduction

Liquid-core waveguide has the merit of sensitivity enhancement and is of great interest to many sensing applications such as fluorescence and Raman measurements, long-path-length UV–visible absorption/transmission, and IR spectrometry [1]. Traditional approaches like electrowetting require high voltage It will be less complicated if the shape and size of liquid lens are controlled by mechanically pumping the liquid into or out of the tip region of waveguide. The focusing power of liquid lens can be adjusted without changing the lens aperture [8] Such idea can be further developed to fabricate solid-state lensed fibers, which have great commercial market for the applications in diode laser pigtails, semiconductor laser coupling systems, biomedical sensing, mode-matching waveguide devices and laser trapping [9,10,11,12,13]. This method would enable the manufacture of high-end customized lensed fibers in volume and at low cost

Experimental setup and results

Conclusions