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Comparison of detection limit in fiber-based conventional, amplified, and gain-clamped cavity ring-down techniques

Comparison of detection limit in fiber-based conventional, amplified, and gain-clamped cavity ring-down techniques
Comparison of detection limit in fiber-based conventional, amplified, and gain-clamped cavity ring-down techniques

Relative performance and detection limit of conventional, amplified, and gain-clamped cavity ring-down techniques (CRDT) in all-fiber configurations are compared experimentally for the first time. Refractive index measurement using evanescent field in tapered fibers is used as a benchmark for the comparison. The systematic optimization of a nested-loop configuration in gain-clamped CRDT is also discussed, which is crucial for achieving a constant gain in a CRDT experiment. It is found that even though conventional CRDT has the lowest standard error in ring-down time (Δτ), the value of ring-down time (τ) is very small, thus leading to poor detection limit. Amplified CRDT provides an improvement in τ, albeit with two orders of magnitude higher Δτ due to amplifier noise. The nested-loop configuration in gain-clamped CRDT helps in reducing Δτ by an order of magnitude as compared to amplified CRDT whilst retaining the improvement in τ. A detection limit of 1.03×10−4 RIU at refractive index of 1.322 with a 3 mm long and 4.5 μm diameter tapered fiber is demonstrated with the gain-clamped CRDT.

Cavity ring-down technique, Detection limit, Evanescent wave sensing, Optical fiber sensors, Refractive index, Tapered fiber
0030-4018
186-192
Sharma, K.
c56d338f-ba42-459e-bed4-d0562410a6e9
Abdul Khudus, M.I.M.
17127b8f-cde4-4c11-aca0-3c9151a42d94
Alam, S.U.
2b6bdbe5-ddcc-4a88-9057-299360b93435
Bhattacharya, S.
efdbfb8b-26cb-43e8-934a-b7ea0301332f
Venkitesh, D.
aea6870a-6fed-499d-b35f-7874f8bf25c6
Brambilla, G.
815d9712-62c7-47d1-8860-9451a363a6c8
Sharma, K.
c56d338f-ba42-459e-bed4-d0562410a6e9
Abdul Khudus, M.I.M.
17127b8f-cde4-4c11-aca0-3c9151a42d94
Alam, S.U.
2b6bdbe5-ddcc-4a88-9057-299360b93435
Bhattacharya, S.
efdbfb8b-26cb-43e8-934a-b7ea0301332f
Venkitesh, D.
aea6870a-6fed-499d-b35f-7874f8bf25c6
Brambilla, G.
815d9712-62c7-47d1-8860-9451a363a6c8

Sharma, K., Abdul Khudus, M.I.M., Alam, S.U., Bhattacharya, S., Venkitesh, D. and Brambilla, G. (2018) Comparison of detection limit in fiber-based conventional, amplified, and gain-clamped cavity ring-down techniques. Optics Communications, 407, 186-192. (doi:10.1016/j.optcom.2017.09.017).

Record type: Article

Abstract

Relative performance and detection limit of conventional, amplified, and gain-clamped cavity ring-down techniques (CRDT) in all-fiber configurations are compared experimentally for the first time. Refractive index measurement using evanescent field in tapered fibers is used as a benchmark for the comparison. The systematic optimization of a nested-loop configuration in gain-clamped CRDT is also discussed, which is crucial for achieving a constant gain in a CRDT experiment. It is found that even though conventional CRDT has the lowest standard error in ring-down time (Δτ), the value of ring-down time (τ) is very small, thus leading to poor detection limit. Amplified CRDT provides an improvement in τ, albeit with two orders of magnitude higher Δτ due to amplifier noise. The nested-loop configuration in gain-clamped CRDT helps in reducing Δτ by an order of magnitude as compared to amplified CRDT whilst retaining the improvement in τ. A detection limit of 1.03×10−4 RIU at refractive index of 1.322 with a 3 mm long and 4.5 μm diameter tapered fiber is demonstrated with the gain-clamped CRDT.

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More information

Accepted/In Press date: 5 September 2017
e-pub ahead of print date: 22 September 2017
Published date: 15 January 2018
Keywords: Cavity ring-down technique, Detection limit, Evanescent wave sensing, Optical fiber sensors, Refractive index, Tapered fiber

Identifiers

Local EPrints ID: 417431
URI: http://eprints.soton.ac.uk/id/eprint/417431
ISSN: 0030-4018
PURE UUID: 6870956e-e36a-45a9-bd64-1c71ca7ebfee
ORCID for G. Brambilla: ORCID iD orcid.org/0000-0002-5730-0499

Catalogue record

Date deposited: 31 Jan 2018 17:30
Last modified: 28 Apr 2022 01:48

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Contributors

Author: K. Sharma
Author: M.I.M. Abdul Khudus
Author: S.U. Alam
Author: S. Bhattacharya
Author: D. Venkitesh
Author: G. Brambilla ORCID iD

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