In recent years, with the development of materials science and architectural art, ensuring the safety of modern buildings is the top priority while they are developing toward higher, lighter, and more unique trends. Structural health monitoring (SHM) is currently an extremely effective and vital safeguard measure. Because of the fiber-optic sensor’s (FOS) inherent distinctive advantages (such as small size, lightweight, immunity to electromagnetic interference (EMI) and corrosion, and embedding capability), a significant number of innovative sensing systems have been exploited in the civil engineering for SHM used in projects (including buildings, bridges, tunnels, etc.). The purpose of this review article is devoted to presenting a summary of the basic principles of various fiber-optic sensors, classification and principles of FOS, typical and functional fiber-optic sensors (FOSs), and the practical application status of the FOS technology in SHM of civil infrastructure.

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Two-dimensional layered monoelemental materials (Xenes) with excellent optoelectronic properties have various property-related applications, such as energy, biomedicine, and optoelectronic devices. Xenes also show excellent performance in acting as saturable absorbers (SAs) for obtaining ultrafast laser operations. Few-layer tellurene as a typical Xenens exhibits distinct optoelectronic properties and promising practical application potential, and its nonlinear optical absorption characteristics and related ultrafast modulation applications have been investigated preliminarily. However, tellurene-based SAs to demonstrate large-energy mode-locked operations, which have special applications in industrial and scientific research areas, are seldom studied. In this work, we focus on the preparation of tellurene-based SAs and explore its applications in demonstrating large-energy mode-locked operations [dissipative soliton (DS) and noise-like pulses (NLP)]. For DS operation, the maximum average output power, pulse width, and largest pulse energy are 23.61 mW, 5.87 ps, and 1.94 nJ, respectively. NLP operation with a recorded average output power of 106.6 mW and a pulse energy of 8.76 nJ is also generated, which shows significant enhancement in comparison to previously reported Xenes-based works. Our contribution reveals the great potential and capacity of tellurene-based SAs in obtaining large-energy pulse operations and further promotes the explorative investigation of Xenes-based optoelectronic devices.

Low saturable intensity, large TPA coefficient and the absorption cross-section demonstrate that tellurene is an advanced broadband nonlinear absorption material and has potential applications in the nonlinear optics field, especially in the infrared band.

Abstract Air-stable broadband saturable absorbers (SAs) exhibit a promising application potential, and their preparations are also full of challenges. Palladium selenide (PdSe2), as a novel two-dimensional (2D) layered material, exhibits competitive optical properties including wide tunable bandgap, unique pentagonal atomic structure, excellent air stability, and so on, which are significant in designing air-stable broadband SAs. In our work, theoretical calculation of the electronic band structures and bandgap characteristics of PdSe2 are studied first. Additionally, PdSe2 nanosheets are synthesized and used for designing broadband SAs. Based on the PdSe2 SA, ultrafast mode-locked operations in 1- and 1.5-μm spectral regions are generated successfully. For the mode-locked Er-doped operations, the central wavelength, pulse width, and pulse repetition rate are 1561.77 nm, 323.7 fs, and 20.37 MHz, respectively. Meanwhile, in all normal dispersion regions, mode-locked Yb-doped fiber laser with 767.7-ps pulse width and 15.6-mW maximum average output power is also generated successfully. Our results fully reveal the capacity of PdSe2 as a broadband SA and provide new opportunities for designing air-stable broadband ultra-fast photonic devices.