Design of Hollow Core Bragg Fibers for a Compact Fluorescence Sensing Scheme

We propose a compact fluorescence sensing scheme based on hollow core Bragg fibers (HCBFs) that simultaneously serve as a sample cell, a collector, and a delivery channel for the desired fluorescence, as well as a filter for the residual excitation light mixed with fluorescence. The liquid samples filled in the air core are laterally irradiated by the excitation light for the spatial separation from fluorescence. Both the photonic bandgap (PBG) effect in the common HCBF (C-HCBF) and the transverse resonant behavior in the defect HCBF (D-HCBF) can be employed for filtering the residual excitation light mixed with fluorescence. The performance of the fluorescence sensing scheme strongly depends on the characteristics of PBG and modal loss for both types of HCBFs. According to the design principle, we present the design strategies of C-HCBF and D-HCBF for fluorescence sensing, respectively. Two typical examples are demonstrated to confirm the feasibility of our proposed fluorescence sensing scheme. We believe that our proposal would provide a new way to build a compact fluorescence sensing system.