We propose an optical fiber immunosensor based on graphene oxide coated dual-peak long period grating (GO-dLPG), in which GO-IgG linking layer is used for rapid immunoassays. The binding interaction between antibody and antigen produced a detectable optical signal in terms of grating resonant wavelength shift, which was proportional to the analyte concentration. By deposition of GO overlay, the bulk RI sensitivity of dLPG was enhanced around 150%. The GO-coated dLPG was biofunctionalized by the immobilization of IgG to generate the biosensor. The IgG-bound GO-dLPG was used to detect the anti-IgG and anti-PSA, respectively, demonstrating high sensitivity and selectivity. The GO-dLPG biosensor can be further developed as a biosensing platform with advantages of label-free, real-time and low limit of detection.
In this work, a graphene oxide-coated long period fibre grating (GO-LPG) is proposed for chemical sensing application.
Graphene oxide (GO) has been deposited on the surface of long period grating to form a sensing layer which
significantly enhances the interaction between LPG propagating light and the surrounding-medium. The sensing
mechanism of GO-LPG relies on the change of grating resonance intensity against surrounding-medium refractive index
(SRI). The proposed GO-LPG has been used to measure the concentrations of sugar aqueous solutions. The refractive
index sensitivities with 99.5 dB/RIU in low refractive index region (1.33-1.35) and 320.6 dB/RIU in high index region
(1.42-1.44) have been achieved, showing an enhancement by a factor of 3.2 and 6.8 for low and high index regions,
respectively. The proposed GO-LPG can be further extended to the development of optical biochemical sensor with
advantages of high sensitivity, real-time and label-free sensing.
Ultrafast laser owns extreme small beam size and high pulse intensity which enable spatial localised modification either on the surface or in the bulk of materials. Therefore, ultrafast laser has been widely used to micromachine optical fibres to alter optical structures. In order to do the precise control of the micromachining process to achieve the desired structure and modification, investigations on laser parameters control should be carried out to make better understanding of the effects in the laser micromachining process. These responses are important to laser machining, most of which are usually unknown during the process. In this work, we report the real time monitored results of the reflection of PMMA based optical fibre Bragg gratings (POFBGs) during excimer ultraviolet laser micromachining process. Photochemical and thermal effects have been observed during the process. The UV radiation was absorbed by the PMMA material, which consequently induced the modifications in both spatial structure and material properties of the POFBG. The POFBG showed a significant wavelength blue shift during laser micromachining. Part of it attributed to UV absorption converted thermal energy whilst the other did not disappear after POFBG cooling off, which attributed to UV induced photodegradation in POF.
We report the simplification and development of biofunctionalization methodology based on one-step 1-ethyl-3-(3- dimethylaminopropyl)carbodiimide (EDC)-mediated reaction. The dual-peak long period grating (dLPG) has been demonstrated its inherent ultrahigh sensitivity to refractive index (RI), achieving 50-fold improvement in RI sensitivity over a standard LPG sensor used in low RI range. With the simple and efficient immobilization of unmodified oligonucleotides on sensor surface, dLPG-based biosensor has been used to monitor the hybridization of complementary oligonucleotides showing a detectable oligonucleotide concentration of 4 nM with the advantages of label-free, real-time, and ultrahigh sensitivity.
The humidity sensor made of polymer optical fiber Bragg grating (POFBG) responds to the water content change in fiber induced by the change of environmental condition. The response time strongly depends on fiber size as the water change is a diffusion process. The ultrashort laser pulses have been providing an effective microfabrication method to achieve spatial localized modification in materials. In this work we used the excimer laser to create different microstructures (slot, D-shape) in POFBG to improve its performance. A significant improvement in the response time has been achieved in a laser etched D-shaped POFBG humidity sensor.