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Side polished fiber (SPF) has a controllable average roughness and length of the side-polishing region, which becomes a versatile platform for integrating multiple materials to interact with the evanescent field to fabricate all-fiber devices and sensors. It has been widely used in couplers, filters, polarizers, optical attenuators, photodetectors, modulators, and sensors for temperature, humidity, strain, biological molecules, chemical gas, and vector magnetic monitoring. In this article, an overview of the development history, fabrication techniques, fiber types, transmission characteristics, and varied recent applications of SPFs are reviewed. Firstly, the fabrication techniques of SPFs are reviewed, including the V-groove assisted polishing technique and wheel polishing technique. Then, the different types of SPFs and their characteristics are discussed. Finally, various applications of SPFs are discussed and concluded theoretically and experimentally, including their principles and structures. When designing the device, the residual thickness and polishing lengths of the SPF need to be appropriately selected in order to obtain the best performance. Developing all-fiber devices and sensors is aimed at practical usability under harsh environments and allows to avoid the high coupling loss between optical fibers and on-chip integrated devices. [ABSTRACT FROM AUTHOR]

Humidity sensors by exploiting transition metal dichalcogenides have attracted enormous attention in various applications. Here, we demonstrate a high-sensitivity fiber-optic humidity sensor based on microfibers overlaid with niobium disulfide (NbS2). Our experimental results show that this type of humidity sensor has high sensitivity, and good repeatability and reversibility. In the RH range of 72–97%, a sensitivity of up to 1.05 dB/RH% and an excellent linearity correlation of 99.5% were achieved. The transmission spectrum of the humidity sensor indicates that this sensor has a wide wavelength detection range from 1530 to 1565 nm. We applied the sensor to monitor human breath with a fast response. We anticipate that the humidity sensor will be useful for the environmental monitoring, food production, and semiconductor industries. [ABSTRACT FROM AUTHOR]

Two-dimensional material tungsten diselenide (WSe2) nanosheets are coated on a microfibre knot resonator (MKR) to achieve an all-optical power modulation functionality. On account of the strong absorption property of WSe2 and the resonance enhancement properties of MKR, the transmitted optical power of signal light within the WSe2-based MKR can be effectively modulated. The sensitivities of light–control–light experiments with 405- and 660-nm lasers are as high as 0.32 and 0.12 dB/mW, respectively. The sensitivities and power tuning can be enhanced by a higher resonance Q and a larger extinction ratio of MKR. In terms of the response time, the average rise and fall times are 3.5/3.7 and 3.5/4 ms with 405- and 660-nm lasers, respectively. This proposed structure is expected to achieve potential applications in all-fibre-optic–based tunable device such as optical modulator, detector, and so on. [ABSTRACT FROM AUTHOR]

Correction to: J Mater Sci (2020) 55:16576-16587 https://doi.org/10.1007/s10853-020-05230-0 In the original article one of the grant numbers in the Acknowledgments was incorrect. The corrected paragraph should read as follows: This work was supported in part by National Natural Science Foundation of China (61775084, 61505069, 61705089, 61705087), in part by the Guangdong Special Support Program (2016TQ03X962), in part by the Guangdong Natural Science Funds for Distinguish Young Scholar (2015A030306046), in part by the Science Foundation of Guangdong Province (2020A1515010791), in part by the Fundamental Research Funds for the Central Universities (21619409, 21619410). [Extracted from the article]

Benefiting from the unique properties of MoS2 nanosheets including high electron mobility, quantum confinement, nanoscale thickness, etc., an effective way is proposed and demonstrated to enhance the refractive index sensitivity of surface plasmon resonance (SPR) sensors, which is strongly desired all the time in the field of biochemical sensing. The SPR sensors are modified by the physical deposition of MoS2 nanosheets, and the sensitivity dependence on the number of deposition cycles is investigated experimentally. It is found that the sensitivity first increases and then declines with the increase of the number of deposition cycles, meaning an optimal thickness thus existing. By depositing MoS2 nanosheets for two cycles, the maximal sensitivity of 2793.5 nm RIU−1 (RIU: refractive index unit) can be achieved, which shows an enhancement of 30.67% compared with the case without any modification. Taking into account the evanescent field intensity and the propagation length, the experimental results can be well analyzed and explained. Simulation results show that the increase of MoS2 overlayers can enhance the intensity of electrical field penetrating into the analyte solution while reducing the propagation length, which collectively results in the nonmonotonic change of the sensitivity depending on deposition cycles. [ABSTRACT FROM AUTHOR]

• The intermodal interference of microfiber was enhanced by forming the micro-arched transition region. • The RI sensitivity of the sensor was up to 12,620.0 nm/RIU in the RI range of 1.3940–1.3980, respectively. • The sensor showed a sensitivity of 0.3 nm/(mg/ml) to the concentration of bovine serum albumin solution. A novel refractive index (RI) sensor based on micro-fiber with micro-arched transition (MMAT) was proposed. The power extinction ratio of interference spectra was enhanced by the micro-arched transition. Although the waist diameter of micro-fiber was less than 6 μm, the power extinction ratio was larger than 10 dB, which was critical to the spectral dip measurement. The relationship between waist diameter of micro-fiber and RI sensitivity was systematically investigated. It turned out that higher RI sensitivity of MMAT could be obtained by decreasing the waist diameter of micro-fiber. While the waist diameter was 5.6 μm, the RI sensitivities of MMATs were up to 2739.8 nm/RIU, 4515.7 nm/RIU and 12,620.0 nm/RIU in the RI range of 1.333–1.3580, 1.3705–1.3905 and 1.3940–1.3980 respectively. The sensor was applied to detecting the concentrations of bovine serum albumin (BSA) solutions and showed the sensitivity of 0.3 nm/(mg/ml). Owing to its small volume and high sensitivity, this kind of senor can be expected to widely apply in fields of biology, chemistry and physics. [ABSTRACT FROM AUTHOR]