Excitation efficiency of a side-pumped fiberized fluorescent dye microcapillary

• We study a micro-capillary structure filled with a fluorescent dye solution.
• The solution is side-pumped along the filled hole by an angle-polished fiber.
• We used fibers polished at 20°, 25°, 30°, 35°, 40° and 45° with aluminium coatings.
• Overall power transmission dependence from different polishing angles is presented.
• The polishing angle causes different behavior of the observed fluorescent spectra.

In the present work we study the dependence of fluorescence spectra for different pump source characteristics on the length of a micro-capillary filled with a fluorescent dye solution. A standard fiber-optic glass ferrule with two parallel 125 μm inner diameter holes serving as capillary structures has been studied. One of the holes of the ferrule was filled with a solution of Rhodamine 6G in glycerin, while in the second hole an angle-polished single-mode pump optical fiber was placed. Experiments with pump fibers polished at 20°, 25°, 30°, 35°, 40° and 45° with a reflective aluminium coating have been conducted. The analysis of the experimental data shows differences in the behavior of the fluorescent spectra at different polished angles. Theoretical calculations for pump ray trajectories as well as overall power transmission for pump fibers polished at different angles have been made. The results show that the proposed construction could be used in optofluidic chemical and biosensors, microfluidic lasers or as a compact fluorescent source compatible with fiber-optic components.