High-resolution and large-strain distributed dynamic sensor based on Brillouin and Rayleigh scattering.

A wide-dynamic-range and high-resolution optical fiber sensor based on Brillouin and Rayleigh scattering is proposed, which merges frequency-scanning phase-sensitive optical time-domain reflectometry (Φ-OTDR) and Brillouin optical time domain analysis (BOTDA) via an adaptive signal corrector (ASC). The ASC suppresses the accumulated error of Φ-OTDR with the reference of BOTDA, which breaks through the measurement range limitation of Φ-OTDR so that the proposed sensor can perform a high-resolution measurement in a wide dynamic range. Its measurement range is determined by BOTDA, and can reach the limitation of optical fiber, while the resolution is limited by Φ-OTDR. In proof-of-concept experiments, a maximum strain variation of up to 302.9 µÉ› is measured with a resolution of 5.5 nɛ. Furthermore, with an ordinary single-mode fiber, high-resolution dynamic pressure monitoring in the range from 20 MP to 0.29 MPa is also demonstrated with 0.14-kPa resolution. This research represents the first time, to the best of our knowledge, that a solution for merging data from a Brillouin sensor and a Rayleigh sensor which achieves the advantages of the two sensors at the same time has been realized.

Quasi-acoustic impedance matching distributed opto-mechanical sensor with aluminized coating optical fibers.

The uncoated single-mode fiber has been extensively researched as an opto-mechanical sensor since it can achieve substance identification of the surrounding media by exciting and detecting transverse acoustic waves via forward stimulated Brillouin scattering (FSBS), but it has the danger of being easily broken. Although polyimide-coated fibers are reported to allow transverse acoustic waves transmission through the coating to reach the ambient while maintaining the mechanical properties of the fiber, it still suffers from the problems of hygroscopic property and spectral instability. Here, we propose a distributed FSBS-based opto-mechanical sensor using an aluminized coating optical fiber. Benefiting from the quasi-acoustic impedance matching condition of the aluminized coating and silica core cladding, aluminized coating optical fibers not only have stronger mechanical properties and higher transverse acoustic wave transmission efficiency but also have a higher signal-to-noise ratio, compared with the polyimide coating fibers. The distributed measurement ability is verified by identifying air and water around the aluminized coating optical fiber with a spatial resolution of 2 m. In addition, the proposed sensor is immune to external relative humidity changes, which is beneficial for liquid acoustic impedance measurements.

Pulse compression to one-tenth of phonon lifetime using quasi-steady-state stimulated Brillouin scattering.

A new stimulated Brillouin scattering (SBS) compression mechanism, quasi-steady-state SBS compression, in which the compression limit is one-tenth of the phonon lifetime with a high energy efficiency, is proposed and practically realized in this study. The feasibility of this approach is demonstrated experimentally, in which a compression of 0.36τB with an energy efficiency of 65% is achieved in a 3M Fluorinert Electronic Liquid FC-3283 and a compression output of 0.12τB (near-compression-limited) with an energy efficiency above 40% is obtained in acetone when the phonon lifetime to leading-edge to ratio is greater than 10. This ratio is identified experimentally as the key parameter in quasi-steady-state SBS compression. This work provides a practical approach to reliably generating one-tenth-phonon-lifetime pulses by quasi-steady-state SBS compression.

Pulse-shape dependence of stimulated Brillouin scattering pulse compression to sub-phonon lifetime.

A new approach to sub-phonon lifetime pulse compression by stimulated Brillouin scattering (SBS) is presented. Triangular and step pulse pumps are both used as a pump source in a single-cell SBS compression setup. Compared with a Gaussian pump (shortest compressed pulse is the phonon lifetime with the highest energy conversion, approximately 60% under the same conditions), the compression ratio is significantly improved in the case of triangular and step pulse pumps, and there is some improvement in the energy conversion when a step pulse pump is used. A pulse as short as a quarter of a phonon lifetime is produced by a triangular pulse pump, with an energy conversion above 30%. The pump pulse shape is identified as the key parameter in achieving sub-phonon lifetime pulse compression. By using a step pulse shape, a 4.5 ns pump pulses with a 60mJ at 1064-nm are compressed down to 292 ps (below semi-phonon-lifetime) in 3M Fluorinert Electronic Liquid FC-770 with an energy conversion above 65%. This work presents a route to reliable generation of sub-semi-phonon-lifetime pulses by SBS compression.

[Study on Detection of Prohibited Pigments in Drinks Using Paper-Based SERS Substrates].

In this paper, a novel paper-based Surface enhanced Raman spectroscopy (SERS) substrate with high sensitivity, good uniformity and popular price is developed via liquid/liquid interface self-assembly technique. Three pigment, rhodamine B, sunset yellow and chrysoidine were detected through paper-based SERS substrates using a portable Raman spectrometer. The structures of the three pigments were investigated and vibrational modes of characteristic peaks of three pigments were assigned. SERS spectra of rhodamine B, sunset yellow and chrysoidine in aqueous solution with different concentrations were detected respectively. Rhodamine B, sunset yellow and chrysoidine in drinks were also detected in drinks without any pretreatment. Within a certain range of concentrations, it meets certain function. For rhodamine B and sunset yellow, the relationship between concentration and Raman peak intensity is on an index curve, while for chrysoidine, the relationship is linear. In addition, high recoveries are achieved for detecting rhodamine B, sunset yellow and chrysoidine in drinks, which indicated our method is suited for semi-quantitative analysis for the concentration of rhodamine B, sunset yellow and chrysoidine in drinks. Surface-enhanced Raman spectroscopy provides an easy approach to fast and efficient detection for multiple pigments in drinks and can be used for quality control and market monitoring of drinks.

Fabrication of transparent SERS platform via interface self-assembly of gold nanorods and gel trapping technique for on-site real time detection.

A transparent SERS platform was fabricated via the gel-trapping method coupled with a liquid/liquid interface self-assembly technique. We employed gold nanorods as the building blocks for interface self-assembly because of their strong localized surface plasmons upon excitation by infrared radiation. Based on a "top cover" configuration, this transparent SERS platform endows high signal reproducibility for directly detecting liquid samples by confining the sample droplet into a regular shape. The Au NR PDMS platform was able to directly detect crystal violet in aqueous solutions down to 10 ppb level with high enhancement factor (0.87 × 10(5)) and signal uniformity (RSD = 3.9%). Furthermore, SERS-based anti-fungal agent detection on a fish scale was demonstrated by simply covering the fish scale with a tailored GNRs PDMS film. The experimental results clearly show that the Au NR PDMS SERS platform has great potential for on-site real time detection of contaminants in water as well as on curved surfaces.