Tapered tip optical fiber refractometer with dramatically enhanced sensitivity

Hamed Nikbakht; Mert Yusuf Erdolu; Chunyu Lu; Bob Van Someren; B. Imran Akca

doi:10.1117/12.2632447

30 May 2022 Tapered tip optical fiber refractometer with dramatically enhanced sensitivity

Hamed Nikbakht, Mert Yusuf Erdolu, Chunyu Lu, Bob Van Someren, B. Imran Akca

Proceedings Volume PC12145, Biophotonics in Point-of-Care II; PC121450H (2022) https://doi.org/10.1117/12.2632447
Event: SPIE Photonics Europe, 2022, Strasbourg, France

Abstract

We demonstrated an inexpensive, simple and ultra-sensitive refractive index (RI) sensor based on a long tapered tip optical fiber combined with a straightforward image analysis method. The tapering length was optimized through beam propagation simulations and trapezoidal tip fibers were fabricated using a single-step chemical etch process. A simple measurement setup was built that consists of a single wavelength light source (λc= 660 nm), a cuvette, an objective lens, and a camera. The sensitivity of the fibers was measured using saline solutions with different concentrations. The light rays exiting the fiber tip along the tapered section form a circular interference pattern on the camera, whose size in the central part very strongly depends on the surrounding refractive index. By analyzing the areal changes in the center of the fringe patterns for different saline solutions, we obtained an unprecedented sensitivity value of 24160 dB/RIU (refractive index unit), which is the highest value reported so far among intensity-modulated fiber refractometers. We also performed beam propagation simulations to predict the behavior of the tapered tip fiber sensor. The experimental results are consistent with the simulations. This sensor is ultra-sensitive, simple, easy-to-fabricate, and low-cost, which makes it a promising tool for on-site measurements and point-of-care applications such as DNA tests based on loop-mediated isothermal amplification.

Conference Presentation

Citation Download Citation

Hamed Nikbakht, Mert Yusuf Erdolu, Chunyu Lu, Bob Van Someren, and B. Imran Akca "Tapered tip optical fiber refractometer with dramatically enhanced sensitivity", Proc. SPIE PC12145, Biophotonics in Point-of-Care II, PC121450H (30 May 2022); https://doi.org/10.1117/12.2632447

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KEYWORDS

Lamps

Optical fibers

Fringe analysis

Chemical analysis

Fiber optics sensors

Refractive index

Sensors

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