Abstract
The consolidation of laser micro/nano processing technologies has led to a continuous increase in the complexity of optical fiber sensors. This new avenue offers novel possibilities for advanced sensing in a wide set of application sectors and, especially in the industrial and medical fields. In this review, the most important transducing structures carried out by laser processing in optical fiber are shown. The work covers different types of fiber Bragg gratings with an emphasis in the direct-write technique and their most interesting inscription configurations. Along with gratings, cladding waveguide structures in optical fibers have reached notable importance in the development of new optical fiber transducers. That is why a detailed study is made of the different laser inscription configurations that can be adopted, as well as their current applications. Microcavities manufactured in optical fibers can be used as both optical transducer and hybrid structure to reach advanced soft-matter optical sensing approaches based on optofluidic concepts. These in-fiber cavities manufactured by femtosecond laser irradiation followed by chemical etching are promising tools for biophotonic devices. Finally, the enhanced Rayleigh backscattering fibers by femtosecond laser dots inscription are also discussed, as a consequence of the new sensing possibilities they enable.
Highlights
Since Snitzer proved how optical fibers can behave as a resonant cavity in 1961 [1], a lot of attention and research effort has been drawn to the transducing properties of optical fibers [2,3,4,5,6,7,8].This led to the beginning of the development of optical fiber sensors (OFS) in the mid-1970s
They are good for long structures such as oil or gas wells and pipelines: this sector accounts for 46% of the total distributed market according to a 2015 market report [15]
When pulse energy (E p ) increases above a higher threshold of 0.31 μJ [34], and several pulses are delivered to the same volume with enough pulse repetition rate (PRR) to interact with each other (When the time between pulses is less than the thermal diffusion time of the material), a large birefringent and negative refractive index change (RIC) emerges
Summary
David Pallarés-Aldeiturriaga 1,2, * , Pablo Roldán-Varona 1,3,4 , Luis Rodríguez-Cobo 4 and José Miguel López-Higuera 1,3,4. Hubert Curien Laboratory, University of Lyon, Jean Monnet University, UMR 5516 CNRS, F-42000 Saint-Etienne, France. Instituto de Investigación Sanitaria Valdecilla (IDIVAL), 39011 Santander, Spain. Received: 5 November 2020; Accepted: 2 December 2020; Published: 6 December 2020
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