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This work reports femtosecond laser based fabrication of long period fiber gratings (LPFG). Index modulation in the core of single mode fiber (SMF) is written employing femtosecond pulse filamentation technique. Highly repeatable filamentary voids written in line-by-line femtosecond laser inscription technique enables steady and noise free growth o...
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Long period fiber gratings are emerging as a potential candidate in the list of surrounding refrac-tive index optical fiber sensors. Their sensitivity can be enhanced greatly if the grating period, fiber dimensions and surrounding refractive index are optimized in a way to operate at a point called turn around point on phase matching curves of thes...
The growing needs for fast and reliable sensing devices stimulate development of new technological solutions. In this work a new multi-domain sensing method is demonstrated where optical sensing device has been applied to enhance amount of data received during electrochemical analysis. Thin, optically transparent, high-refractive-index, and electri...
A highly integrated sensing technology, combining a stimulated Brillouin scattering-based distributed sensor with XFG (fiber Bragg grating (FBG) and long-period fiber grating (LPFG)) sensors on a single fiber, is proposed for the simultaneous measurement of fully distributed and multiple discrete dynamic strains/temperatures. A multiparameter monit...
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... Concerning the fabrication of LPFGs, several methods have been developed, including the use of UV and CO2 laser radiation exposure, electric arc discharges, mechanical pressure, ion beam irradiation, chemical etching, and IR femtosecond laser radiation [1]. The fabrication of LPFGs has shown to be possible in a variety of optical fibers [4]. ...
A femtosecond laser direct writing system was developed to explore the fabrication of long-period fiber gratings (LPFGs) in SMF28 fibers. The LPFGs, showing the mode LP1,6 at 1500 nm, were exposed to high-temperature annealing up to 950 °C. Modifications in the refractive index (RI) modulation are observed through a blue-shift in the LPFG attenuation bands and above 850 °C, the mode LP1,7 appear at 1600 nm. The wavelength sensitivity to external RI from 1.300 to 1.452 was estimated for both modes before and after annealing. Greater sensitivity was found for the higher order mode in the entire range reaching 2400 nm/RIU around 1.440.
... Due to the expansion of multimedia services such as video on demand, video-conferencing, e-learning, interactive services, and VOIP, the demand for an optical fiber based high speed Internet network has increased significantly. Although optical fibers have been designed primarily for optical communication, they show promise in a wide range of application areas including coupling [1], fiber lasers [2], optical sensors [3][4][5][6][7][8][9], imaging and spectroscopy [10,11], and biomedical engineering [12]. In most of the cases, micro-structuring of the optical fibers is required to produce application specific optical fibers. ...
This paper reports the fabrication of various micro-lensed single-mode optical fibers through the use of an enhanced peak power CO2 laser beam. The end faces of the optical fibers are exposed to the CO2 laser beam to form convex, concave, and conical shape optical fiber tips. Peak power of the CO2 laser beam was varied from 0.8 W to 1.5 W depending on the shape of the optical fiber tip. We also discover the dependence of the angle of the optical fiber tip on the rotation angle and the number of CO2 laser irradiations. The angle shows an increasing trend with both these parameters. We achieve a wide range of lenticular fibers with end face angle varying from 4.47° to 8.13°. Furthermore, we investigate the emission pattern of light from the developed micro-lensed fibers. The proposed CO2 laser based optical fiber reshaping technique shows great consistency, and thus is suitable for commercial applications.
... Although the initial laser beam was continuous wave, nowadays high energy pulsed laser sources having variable pulse width varying from nanosecond to attosecond exist for micro/nano-scale patterning of materials. During last several decades, femtosecond laser beams have been utilized for various applications including micro/nano-structuring [2,3], photonic devices fabrication [4,5], and metal colorizing [6]. ...
This paper demonstrates the characterization of femtosecond laser filamentation in soda-lime glass. We achieved femtosecond pulse filamentation of variable height and width by focusing the femtosecond laser beam in different layers inside the sample glass. The dielectric medium immediately before the target position increases the effective numerical aperture of the objective lens that causes the elongation of focal length of the laser beam in a tiny focal spot with high power density. As a result, high aspect ratio voids are engraved inside the glass samples. Furthermore, we investigate the characteristics of the fabricated voids and their dependence on the irradiation conditions of the laser beam and associated optical setup. The height and width of the voids are controlled by varying the laser power, numerical aperture & magnification of the objective lens, and width of the dielectric medium before laser focusing position. Using high power femtosecond laser pulse filaments, we fabricated very long voids inside the glass sample, which undergoes cleaving process with uniform mechanical pressure for smooth cutting of the glass substrate.
Optical fiber Mach-Zehnder interferometers were fabricated by combining two TiO 2 coated LPFGs fabricated through femtosecond laser direct writing. Results of its refractometric characterization are presented and compared with the single LPFGs sensors. Wavelength sensitivity of 1175 nm/RIU at 1.38 and spectral resolution of 2.2x10 ⁻⁵ were achieved.
This study used an inductively coupled plasma (ICP) dry etching process with a metal amplitude mask to fabricate a double-side notched long-period fiber grating (DNLPFG) for loading sensing. The DNLPFG exhibited increasing resonance attenuation loss for a particular wavelength when subjected to loading. When the DNLPFG was subjected to force loading, the transmission spectra were changed, showing a with wavelength shift and resonance attenuation loss. The experimental results showed that the resonant dip of the DNLPFG increased with increasing loading. The maximum resonant dip of the 40-μm DNLPFG sensor was −26.522 dB under 0.049-N loading, and the largest force sensitivity was −436.664 dB/N. The results demonstrate that the proposed DNLPFG has potential for force sensing applications.
In this paper, we propose using notched long-period fiber grating (NLPFG) fabricated by inductively coupled plasma etching for glucose concentration measurements. The experimental results show that the wavelengths varied linearly with differing glucose concentrations. The sensitivity of the NLPFG glucose concentration sensor is −0.147 nm/wt % from 0-40 wt % and the linearity (R2) is 0.938. The results demonstrate that the proposed NLPFG has potential for high-sensitivity glucose concentration sensor applications.
