Next Article in Journal
Error Overboundings of KF-Based IMU/GNSS Integrated System Against IMU Faults
Next Article in Special Issue
Magnetic Field Sensor Based on a Tri-Microfiber Coupler Ring in Magnetic Fluid and a Fiber Bragg Grating
Previous Article in Journal
A Revisiting Method Using a Covariance Traveling Salesman Problem Algorithm for Landmark-Based Simultaneous Localization and Mapping
Open AccessArticle

Combination of an Axicon Fiber Tip and a Camera Device into a Sensitive Refractive Index Sensor

Department of Mechanical Engineering, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan
Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
Institute of Biophotonics, National Yang-Ming University, Taipei 11221, Taiwan
Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 20224, Taiwan
Author to whom correspondence should be addressed.
Sensors 2019, 19(22), 4911;
Received: 7 October 2019 / Revised: 1 November 2019 / Accepted: 6 November 2019 / Published: 11 November 2019
(This article belongs to the Special Issue Optical Fiber Sensors and Photonic Devices)
An axicon fiber tip combined with a camera device is developed to sensitively detect refractive indexes in solutions. The transparent axicon tips were made by etching optical fibers through a wet end-etching method at room temperature. When the axicon fiber tip was immersed in various refractive index media, the angular spectrum of the emitted light from the axicon fiber tip was changed. Using a low numerical aperture lens to collect the directly transmitted light, a high intensity sensitivity was achieved when the tip cone angle was about 35 to 40 degrees. We combined the axicon fiber tip with a laser diode and a smartphone into a portable refractometer. The front camera of the smartphone was used to collect the light emitted from the axicon fiber tip. By analyzing the selected area of the captured images, the refractive index can be distinguished for various solutions. The refractive index sensitivity was up to 56,000%/RIU, and the detection limit was 1.79 × 10−5 RIU. By measuring the refractive index change via the axicon fiber tip, the concentration of different mediums can be sensitively detected. The detection limits of the measurement for sucrose solutions, saline solutions, and diluted wine were 8.86 × 10−3 °Bx, 0.12‰, and 0.35%, respectively. View Full-Text
Keywords: axicon optical fiber; refractometer; smartphone; intensity sensitivity axicon optical fiber; refractometer; smartphone; intensity sensitivity
Show Figures

Figure 1

MDPI and ACS Style

Tai, Y.-H.; Tsai, P.-C.; Ho, Y.-L.; Delaunay, J.-J.; Wei, P.-K. Combination of an Axicon Fiber Tip and a Camera Device into a Sensitive Refractive Index Sensor. Sensors 2019, 19, 4911.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

Back to TopTop