We demonstrate infrared spectroscopy systems that are capable of predicting acrylamide level in powders of potato fries based on all-fiber high power supercontinuum (SC) lasers in both the short-wave and mid-wave infrared spectral range. Two SC lasers used in this study cover wavelength range of 670nm to 2500nm and 1600nm to 11000nm, respectively. We use the spectroscopy system to measure 32 French fry samples with different acrylamide concentrations calibrated by gas chromatography-mass spectroscopy (GCMS). Our predicted acrylamide concentrations show a good linear correlation to the measured acrylamide concentration obtained through GCMS, and the partial least square regression analysis shows standard error down to 145ppb. Based on our results, our system could provide a non-destructive alternative method for determining the acrylamide in food samples at a stand-off distance, which could be important for near-line or in-line quality control purposes.
All-fiber integrated super-continuum (SC) sources are described based on a platform architecture that can operate in the visible, near-infrared, short-wave infrared, mid-wave infrared and long-wave infrared, with demonstrated SC wavelengths ranging from 0.47 to 12 μm. Modulation instability initiated SC generation leads to a simple SC source with no moving parts and that uses o_-the-shelf components from the mature telecommunications and fiber optics industry. The resulting light sources are basically a cascade of fibers pumped by fiber-pigtailed laser diodes and some drive and control electronics; thus, the SC sources have the potential to be cost-effective, compact, robust and reliable. Starting from fused silica fibers, the SC spectrum can be extended to shorter or longer wavelengths by cascading fibers with appropriate dispersion and/or transparency. As one example, we demonstrate a long-wave infrared SC source that generates a continuous spectrum from approximately 1.57 to 12 μm using a fiber cascade comprising fused silica fiber followed by ZBLAN fluoride fiber followed by sulfide fiber and, finally, a high-numerical-aperture selenide fiber. The time-averaged output power is as high as 417 mW at 33% duty cycle, and we observe a near-diffraction-limit, single spatial-mode beam across the entire spectral range. A prototype is described that is based on a three-layer architecture with a form factor of 16.7 × 10 × 5.7 and that plugs into a standard wall plug. This SC prototype has been used in a number of field tests as the active illuminator for stand-off FTIR system over distances of 5 to 25 m, thus enabling identification of targets or samples based on their chemical signature. Further optimization of the SC source will also be described to increase the output power and to reduce the form factor.
We demonstrate a prototype sensor capable of measuring specular and diffuse reflectance spectra from samples 3.6 m away. The sensor utilizes mid-wave to long-wave infrared supercontinuum light coupled into a rotational FTIR spectrometer to actively probe remote samples. We measure the diffuse reflectance of acetaminophen at 41.77 μg/cm2 on a glass substrate and find that a modified Bobbert-Vlieger analysis can estimate the effects of particle size distribution on return spectra. We find that the measured return from stand-off particulate measurements depends not only on the chemical identity, but also the size and distribution of particles on the substrate.