Caibin Yu

Graphene oxide deposited microfiber knot resonator for gas sensing

Graphene and its derivative graphene oxide (GO) have been the focus of attention in the field of chemical and biological sensing. In this paper, we report a fiber-optic sensor for chemical gas sensing by using graphene oxide coated microfiber knot resonator (GMKR). The refractive index of GO was changed when the gas molecules were adsorbed to the surface of GO, and the gas concentration varying induced refractive index change can be detected by measuring the interference fringes shift of the GMKR. The experimental results show the sensitivities of ~0.35pm/ppm for NH3 and ~0.17pm/ppm for CO detection, due to the different adsorption energy and charge transfer ability between the gas molecules and GO. Experimental results show GO is a promising candidate for gas sensing and can be combined with various fiber-optic devices due to the easy transfer process.

Highly sensitive force sensor based on optical microfiber asymmetrical Fabry-Perot interferometer

An asymmetrical Fabry-Perot interferometric (AFPI) force sensor is fabricated based on a narrowband reflection of low-reflectivity fiber Bragg grating (LR-FBG) and a broadband Fresnel reflection of the cleaved fiber end. The AFPI sensor includes a section of microfiber made by tapering and it achieves a force sensitivity of 0.221 pm/μN with a tapered microfiber of 40 mm length and 6.1 μm waist diameter. Compared with similar AFPI structure in 125 μm-diameter single mode fiber, the force sensitivity of the microfiber AFPI structure is greatly enhanced due to its smaller diameter and can be optimized for different force scales by controlling the diameter. The fabrication process of the AFPI sensor is simple and cost-effective. The AFPI sensor has better multiplexing capacity than conventional extrinsic fiber-optic Fabry-Perot sensors, while it also release the requirement on the wavelength matching of the FBG-pair-based FPI.

Graphene-Based D-Shaped Polymer FBG for Highly Sensitive Erythrocyte Detection

Graphene-based silica fiber-optic sensors, with high sensitivity, fast response, and low cost, have shown great promise for gas sensing applications. In this letter, by covering a monolayer of p-doped graphene on a D-shaped microstructured polymer fiber Bragg grating (FBG), we propose and demonstrate a novel biochemical probe sensor, the graphene-based D-shaped polymer FBG (GDPFBG). Due to the graphene-based surface evanescent field enhancement, this sensor shows high sensitivity to detect surrounding biochemical parameters. By monitoring the Bragg peak locations of the GDPFBG online, human erythrocyte (red blood cell) solutions with different cellular concentrations ranging from 0 to 104 ppm were detected precisely, with the maximum resolution of sub-ppm. Such a sensor is structurally compact, is clinically acceptable, and provides good recoverability, offering a state-of-the-art polymer-fiber-based sensing platform for highly sensitive in situ and in vivo cell detection applications.

Optical Graphene Gas Sensors Based on Microfibers: A Review

Graphene has become a bridge across optoelectronics, mechanics, and bio-chemical sensing due to its unique photoelectric characteristics. Moreover, benefiting from its two-dimensional nature, this atomically thick film with full flexibility has been widely incorporated with optical waveguides such as fibers, realizing novel photonic devices including polarizers, lasers, and sensors. Among the graphene-based optical devices, sensor is one of the most important branch, especially for gas sensing, as rapid progress has been made in both sensing structures and devices in recent years. This article presents a comprehensive and systematic overview of graphene-based microfiber gas sensors regarding many aspects including sensing principles, properties, fabrication, interrogating and implementations.

Highly sensitive and selective fiber-optic Fabry-Perot volatile organic compounds sensor based on a PMMA film

A compact fiber-optic Fabry-Perot interferometric (FFPI) volatile organic compounds (VOCs) sensor is fabricated based on a single mode fiber (SMF) and a polymethyl methacrylate (PMMA) film. The VOCs induce the swelling effect and refractive index changes of PMMA film. The swelling of PMMA film affects the cavity length of Fabry-Perot interferometer resulting in shift of resonant dip, while the change in refractive index influences reflection resulting in change of extinction ratio (ER). The sensitivities of 2.7 pm/ppm for ethanol and 2.17 pm/ppm for acetone are achieved. Moreover, this sensor is insensitive to the inorganic gases. In addition, it has the advantages of ease of fabrication and high sensitivity to VOCs.

Graphene-Enhanced Brillouin Optomechanical Microresonator for Ultrasensitive Gas Detection

Forward phase-matched Brillouin optomechanical resonance, excited by a tapered fiber, in a graphene inner-deposited whispering-gallery-mode microfluidic cavity, is demonstrated for the first time. The generated Brillouin optomechanical modes with Q factor ∼ 47000 show extremely high sensitivity (200kHz/ppm) for absolute gas detection based on frequency variation, achieving a detection limit down to 1 ppb and a dynamic range >105 orders of magnitude.

A Highly Sensitive Fiber-Optic Microphone Based on Graphene Oxide Membrane

We present a fiber-optic microphone (FOM) based on graphene oxide (GO) membrane in this study. A Fabry–Perot cavity consisting of a single-mode fiber and a piece of GO membrane works as the acoustic sensing structure. Using the GO as the core acoustic sensing component, the fabricating process of the FOM is demonstrated to be simple and efficient. Acoustic tests show that this FOM achieves an average minimum detectable pressure of 10.2 μPa/Hz 1/2, while maintaining a linear acoustic pressure response and a flat frequency response in the range of 100 Hz to 20 kHz. These results indicate the excellent suitability of this FOM for acoustic detection in the audible range with high sensitivity and high fidelity.

Fiber interrogated and graphene enhanced Brillouin optomechanical microresonator for ultra-sensitive gas detection

Forward phase-matched Brillouin optomechanical resonance, excited by a tapered fiber, in a graphene inner-deposited whispering-gallery-mode microfluidic cavity, is demonstrated for the first time. The generated Brillouin optomechanical modes with Q factor ∼ 47000 show extremely high sensitivity (200kHz/ppm) for absolute gas detection based on frequency variation, achieving a detection limit down to 1 ppb and a dynamic range >105 orders of magnitude.

Highly sensitive fiber-optic Fabry-Perot geophone with graphene-coated PMMA membrane

A highly sensitive fiber-optic Fabry-Perot interferometric geophone (FFPG) with graphene coated PMMA membrane is proposed and demonstrated, where the graphene coating is used for enhancement of the mechanical strength of the membrane. It is found that the sensitivity of the FFPG is much higher than that of the conventional electrical geophone. Such a novel all-optical geophone with low cost, high sensitivity, electromagnetic interference immunity, easy fabrication and robust structure would have great potential for use in oil/gas exploration and seismic wave detection.

Sensitivity Improvement of Fiber-optic NH 3 Gas Sensor Using Pt Nanoparticle Doped Graphene Oxide

By incorporating Pt nanoparticle with graphene oxide (GO), a nanocomposite-based microfiber sensor with high sensitivity for NH3 sensing was fabricated and demonstrated, which indicates sensitivity improvement of 3 times over that without Pt doping.