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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 10^\mathrm \mathbf 4 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. [ABSTRACT FROM PUBLISHER]

Mode-locking is a milestone in the history of lasers that allows the generation of short light pulses and stabilization of lasers. This phenomenon is known to occur only in standard ordered lasers for long time and until recently it is found that it also occurs in disordered random lasers formed by nanoscale particles. Here, we report the realization of a so-called quasi mode-locking of coherent feedback random fiber laser which consists of a partially disordered linear cavity formed between a point reflector and a random distributed fiber Bragg grating array with an inserted graphene saturable absorber. We show that multi-groups of regular light pulses/sub-pulses with different repetition frequencies are generated within the quasi mode-locking regime through the so-called collective resonances phenomenon in such a random fiber laser. This work may provide a platform to study mode locking as well as pulse dynamic regulation of random lasing emission of coherent feedback disordered structures and pave the way to the development of novel multi-frequency pulse fiber lasers with potentially wide frequency tuning range. [ABSTRACT FROM AUTHOR]

A compact all-in-line graphene-based distributed feedback Bragg-grating fiber laser (GDFB-FL) with narrow linewidth of hundreds kHz is demonstrated and investigated in this study. Performing as an optical saturable absorber, graphene oscillates the initially kHz linewidth DFB-FL, and generates high-quality passively Q-switched pulses. Pumped with a 980 nm continuous-wave laser, the Q-switched GDFB-FL observes ~1 μs pulse durations, with pulse energies up to ~10 nJ and approaching the transform limit. The peak power is ~600 times higher than the original DFB-FL laser. By optimizing the cavity design and the graphene material, it is predicted that fast Q-switched pulses with more than MHz repetition rates and sub-100 ns pulse durations are achievable. Such transform-limited Q-switched GDFB-FLs with narrow linewidth of sub-MHz have long coherence length, good tunability, stability, compactness and robustness, with potential impact in optical coherent communications, metrology and sensing.

Graphene based new physics phenomena are leading to a variety of stimulating graphene-based photonic devices. In this study, the enhancement of surface evanescent field by graphene cylindrical cladding is observed, for the first time, by using a graphene-coated microfiber multi-mode interferometer (GMMI). It is found theoretically and experimentally that the light transmitting in the fiber core is efficiently dragged by the graphene, hence significantly enhancing the evanescent fields, and subsequently improving the sensitivity of the hybrid waveguide. The experimental results for gas sensing verified the theoretical prediction, and ultra-high sensitivities of ~0.1 ppm for NH(3) gas detection and ~0.2 ppm for H(2)O vapor detection are achieved, which could be used for trace analysis. The enhancement of surface evanescent field induced by graphene may pave a new way for developing novel graphene-based all-fiber devices with compactness, low cost, and temperature immunity.

Graphene Bragg gratings (GBGs) on microfiber are proposed and investigated in this paper. Numerical analysis and simulated results show that the mode distribution, transmission loss, and central wavelength of the GBG are controllable by changing the diameter of the microfiber or the refractive index of graphene. Such type of GBGs with tunability may find important applications in optical fiber communication and sensing as all-fiber in-line devices.

Background: Pigs have been regarded as the preferred source of organs for human xenotransplantation. The aim of the present study was to explore the biomechanical properties of the bile duct in pigs and humans to provide evidence for liver xenotransplantation., Materials and Methods: Fresh bile duct specimens obtained from 50 pigs aged 3 to 12 months and five deceased human donors. The diameters and wall thickness of the bile duct were measured using a computer imaging analysis system. The pressure-diameter of bile ducts was tested with biomechanical equipment. The corresponding parameters were calculated: incremental elastic moduli (E(inc)), pressure-strain elastic modulus (E(p)), volume elastic modulus (E(v)), and compliance., Results: The E(inc), E(p), and E(v) of porcine bile duct gradually decreases with age. However, the E(inc), E(p), and E(v) gradually increased after pigs aged 10 months. The E(inc), E(p), and E(v) of pig bile ducts aged 3 to 6, and 11 to 12 months were higher than that of humans aged 20 to 40 years (P < .01). The changes in compliance of the porcine bile duct with age oppose those in elastic modulus. There were no significant differences in the elastic modulus and compliance of the bile duct between pigs aged 7 to 10 months and adult humans (P > .05)., Conclusions: The biomechanical properties of the bile duct of pigs aged 7 to 10 months match that of adult humans. The correlation between age and biomechanical properties of bile ducts in pigs implied that a pig aged 7 to 10 months should be chosen for pig-to-human liver xenotransplantation., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Objective: Our aim was to explore the biomechanical properties of hepatic portal vein (HPV) in humans and pigs to provide evidence for liver xenotransplantation., Materials and Methods: The pressure-diameter relationships of HPV from 6 deceased donors and 36 pigs were measured on a biomechanical experimental stand to calculate the elastic modulus and compliance. Each sample sliced into 5-mm frozen sections was stained with hematoxylin-eosin (H&E). Geometric morphological indices were measured with a computer image analysis system., Results: The length, wall thickness, and diameters of HPV in pigs increased from 1 to 6 months (P < .05). There were no significant differences between 6-month-old pigs and adult humans (P > .05). The incremental elastic modulus of the pig HPV increased with age, whereas the compliance decreased. There was no difference in the elastic modulus of HPV between 5- to 6-month-old pigs and humans (P > .05). Also, there was no difference in HPV compliance between 6-month-old pigs and humans (P > .05)., Conclusions: Our results suggested that the biomechanical properties of HPV in 6-month-old pigs were similar to those of humans. From a biomechanical perspective, anastomosis of corresponding HPV from 6-month-old pigs to humans may be feasible in the process of pig-to-human liver xenotransplantation.