Raman spectroscopy (RS) is a non-destructive analytical technique, that provides a unique fingerprint of molecules with high accuracy. It proves to be a reliable and practical alternative to chemical analysis, allowing sample identification without the use of reagents. This label-free technique finds applications in quality control and in-line process monitoring, however, like any other technique RS also presents its challenges such as expensive and delicate instrumentation and complex design, which often confines the technique to the laboratory. In order to address these challenges, a 3D printed Lab-On-Chip (LOC) was fabricated and assembled with four channel optical fibres, which will collect the Raman scattering. The performance of our Raman Probe on Chip is evaluated using Isopropanol alcohol (IPA) as a validation sample.
The widespread use of smartphones forecasts huge increase in application-based portable sensors, particularly using the embedded light source and camera detector. Albeit Fibre Bragg gratings (FBG) were originally discovered at visible wavelengths, their commercial and scientific dissemination is predominant in the C-band of optical communications. Recently, several authors gave attention to FBG in the visible, aiming simpler and low-costly interrogation methods that could increase the application of FBG sensors in biomedicine, immunology and biophysics. We study the detection of VIS FBG using standard lamps or LEDs coupled to VIS, silicon based, CCDs in commercial instruments. We show that is possible to record the FBG spectrum with adequate signal to noise ratio,allowing hand held FBG interrogation methods in diverse environments.
Thermal sensitivity increase of regenerated fiber Bragg gratings (RFBG) in the visible range is reported. The FBGs are produced by direct illumination under the phase mask using UV light from two different laser sources at 248 nm. After regeneration the thermal sensitivity is obtained at 500°C to avoid spectra vanishing for temperatures near that of regeneration. At 500°C, the determined thermal sensitivities are 5.74pmK-1 before and 7.65pmK-1 after regeneration (single mode fiber in the visible, femtosecond laser), and a similar pattern is presented for all regenerated FBGs.
A visible fiber Bragg grating (Vis-FBG) with wavelength peak centered at 673.07 nm was inscribed in a multimode fiber designed for infrared (IR) operation using a femtosecond (fs) laser emitting at 248 nm. The fiber cladding is removed by chemical etching in hydrofluoric acid solution (40%). The sensor refractive index response is determined by dipping the sensor into diluted glycerin solution at different concentrations with refractive index range from 1.3328 to 1.4607. The Vis-FBG performance is compared with an IR etched FBG (EFBG) with similar diameter. The sensitivity found for the Vis-FBG sensor is 15.71nm/RIU with a 6.34 x 10-3 RIU resolution for a refractive index of 1.4607.
We report regeneration studies of fiber Bragg gratings with resonance band in the visible spectral range. The FBG were produced by direct illumination under the phase mask using UV light from a fs-laser pumped optical parametric amplifier. Some seed gratings were not so saturated as common C-Band gratings written by other methods but their regeneration efficiency is quite high. The final line-widths are narrower than the similar C-band regenerated gratings.
The thermal and deformation properties of fiber Bragg gratings (FBG) in the visible range were characterized for the first
time in our knowledge. The FBG were written in silica single mode (cutoff in the visible and infrared range) and
multimode fibers, using a phase-mask (460 nm period) illuminated by a 248 nm femtosecond laser.