Lensed Dual-Fiber Probe for the Effective Collection of Fluorescence Signals

A simple and compact lensed dual-fiber probe having high collection efficiency for fluorescence signal is demonstrated. A lensed dual-fiber probe, composed of two parallel fibers and a common focusing lens, was simply implemented by the electric arc discharge method. The performance of the proposed probe was evaluated experimentally by measuring the reflection powers and fluorescence spectra of well-known targets and a fresh ginkgo leaf. The experimental result shows that the proposed probe provides a six-fold increase in the collection efficiency compared to measurements without the lens. In addition, the signal collection occurs very close to the probe surface with a suitably localized depth.

I. Introduction

Light-Induced fluorescence spectroscopy is an invaluable measurement tool in many areas including biomedical and chemical engineering [1]–[3]. A fluorescence spectroscopy system is typically composed of a light source, an optical spectrum analyzer as a detector, and a light delivery component for excitation light illumination and excited fluorescence signal collection. The use of an optical fiber as the light delivery component provides great advantages, such as flexibility of the probe, a compact size, and easy coupling to spectroscopic instruments.