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Rapid analysis of food raw materials adulteration using laser direct infrared spectroscopy and imaging
摘要： The objective of this study was to assess the application of the Laser Direct Infrared (LDIR) imaging system as a rapid screening technology for detection, identification, and semi-quantitation of adulterants in food ingredients. Forty-five samples of skimmed milk powder, thirty-one samples of soy protein isolate, thirty-five samples of chicken meat powder, thirty-two samples of pea protein isolate and six samples of wheat flour were dry blended adulterated with nitrogen-rich compounds and bulking agents at concentrations of 1.0 to 15.0% (w/w). In addition, ten samples of skimmed milk powder were wet blended with food adulterants at 5.0% and 10.0% (w/w) to check the LDIR performance when different fraudulent processes are applied. The results from this study shows that LDIR can be used as a rapid untargeted screening method that are independent of adulterants to detect, identify and semi-quantify food adulterants in dry blended samples. In most samples, the technology accurately identified all nitrogen-rich compounds and bulking agents present in the dry blended samples. In addition, the technology shows sensitivity of 82% for samples adulterated at 1% and sensitivity from 92% to 100% for samples adulterated at ≥ 5% economic adulteration. On the other hand, the detection and identification of food adulterants in samples prepared by wet blending process was more challenging than dry blended samples because mid-infrared technology may not be sensitive enough to detect adulterants if they are dissolved or if hidden within the particles.
关键词： Food adulteration,mid-infrared,laser direct infrared imaging,vibrational spectroscopy,untargeted method,raw materials
更新于2025-09-23 15:19:57
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Electrical Phase Control Based on Graphene Surface Plasmon Polaritons in Mid-infrared
摘要： Phase modulation of light is the core of many optoelectronic applications, such as electro-optic switch, sensors and modulators. Graphene Surface plasmon polaritons (SPPs) exhibit unique properties in phase modulation including dynamic tunability, a small driving voltage and small device size. In this paper, the novel phase modulation capability of graphene SPPs in mid-infrared are confirmed through theory and simulation. The results show that graphene SPPs can realize continuous tuning of the phase shift at multiple wavelengths in mid-infrared, covering the phase range from 0° to 360°. Based on these results, a sandwich waveguide structure of dielectric–graphene–dielectric with a device length of 800 nm is proposed, which shows up to 381° phase modulation range at an operating wavelength of 6.55 μm, given a 1 V driving voltage. In addition, the structure size is much shorter than the wavelength in mid-infrared and can realize sub-wavelength operation. This work paves the way to develop graphene-based tunable devices for mid-infrared wave-front control.
关键词： Mid-infrared,phase modulation,graphene surface plasmon polaritons
更新于2025-09-23 15:19:57
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Mid-infrared supercontinuum generation with high spectral flatness in dispersion flattened tellurite all-solid hybrid microstructured optical fibers
摘要： Tellurite all-solid hybrid microstructured optical fibers are proposed for chromatic dispersion control. An ultra-flattened chromatic dispersion profile with variation as small as ± 0.2 ps/km/nm over the wavelength range from 2.5 to 3.7 μm can be obtained. The fibers with flattened chromatic dispersion profiles have high potential for broadband mid-infrared supercontinuum generation. Fabrication of the fiber is successfully performed and by pumping the fabricated fiber at 2 μm, a broad and highly coherent supercontinuum with high spectral flatness is generated.
关键词： mid-infrared,supercontinuum generation,microstructured optical fibers,tellurite fibers,chromatic dispersion
更新于2025-09-23 15:19:57
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Mid-Infrared Electro-Optical Modulation Using Monolithically Integrated Titanium Dioxide on Lithium Niobate Optical Waveguides
摘要： tunable photonic circuits were demonstrated in the mid-infrared (mid-iR) regime using integrated tio2-on-Linbo3 (toL) waveguides. the upper waveguide ridge was made by a sputtered tio2 thin film with broad transparency at λ = 0.4–8 μm and an optimized refractive index n = 2.39. The waveguide substrate is a z-cut single crystalline Linbo3 (LN) wafer that has strong Pockels effect, thus enabling the tunability of the device through electro-optical (e-o) modulation. A sharp waveguide mode was obtained at λ = 2.5 μm without scattering or mode distortion found. The measured E-O coefficient γeff was 5.9 pm/V approaching γ31 of 8.6 pm/V of LN. The ToL waveguide showed a hybrid mode profile where its optical field can be modified by adjusting the TiO2 ridge height. our monolithically integrated ToL modulator is an efficient and small footprint optical switch critical for the development of reconfigurable photonic chips.
关键词： electro-optical modulation,lithium niobate,optical waveguides,mid-infrared,titanium dioxide
更新于2025-09-23 15:19:57
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Ultrahigh resolution spectroscopy for dimethyl sulfide at the ??1- and ??8-bands by a distributed feedback interband cascade laser
摘要： The ultrahigh-resolution, air-broadened mid-infrared absorption spectrum of dimethyl sulfide (DMS) was recorded in the spectral region of 2994.17–2999.03 cm?1, where the strong ν1-/ν8-bands are located. Benefitting from the tunable laser absorption spectrometry with a distributed feedback interband cascade laser, the spectral resolution achieved 5.69 × 10?6 cm?1. The recorded spectra of DMS are very close to that in the Pacific Northwest National Laboratory (PNNL) database, however it has a much lower absorbance uncertainty of 0.38%. And the maximum relative difference of the full width at half maximum and the integrated area of spectral peaks between the recorded spectra and the PNNL data are as large as 16.7% and 27.9%, respectively, which could mainly come from the difference of the spectral resolution. The more accurate reference spectrum is hopeful to be applied to absolute measurement and remote sensing for gaseous DMS.
关键词： Tunable laser absorption spectroscopy (TLAS),Dimethyl sulfide (DMS),Ultrahigh-resolution spectrum,Interband cascade laser (ICL),Mid-infrared
更新于2025-09-23 15:19:57
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Optical properties of metamorphic type-I InAs <sub/> 1? <i>x</i> </sub> Sb <sub/><i>x</i> </sub> /Al <sub/><i>y</i> ? </sub> In <sub/> 1? <i>y</i> ? </sub> As quantum wells grown on GaAs for the mid-infrared spectral range
摘要： We analyse the optical properties of InAs1?xSbx/Aly In1?y As quantum wells (QWs) grown by molecular beam epitaxy on relaxed Aly In1?y As metamorphic buffer layers (MBLs) using GaAs substrates. The use of Aly In1?y As MBLs allows for the growth of QWs having large type-I band offsets, and emission wavelengths >3 μm. Photoluminescence (PL) measurements for QWs having Sb compositions up to x = 10% demonstrate strong room temperature PL up to 3.4 μm, as well as enhancement of the PL intensity with increasing wavelength. To quantify the trends in the measured PL we calculate the QW spontaneous emission (SE), using a theoretical model based on an eight-band k·p Hamiltonian. The theoretical calculations, which are in good agreement with experiment, identify that the observed enhancement in PL intensity with increasing wavelength is associated with the impact of compressive strain on the QW valence band structure, which reduces the band edge density of states making more carriers available to undergo radiative recombination at fixed carrier density. Our results highlight the potential of type-I InAs1?xSbx/Aly In1?y As metamorphic QWs to address several limitations associated with existing heterostructures operating in the mid-infrared, establishing these novel heterostructures as a suitable platform for the development of light-emitting diodes and diode lasers.
关键词： light-emitting diode,k·p modelling,metamorphic heterostructure,mid-infrared,semiconductors,molecular beam epitaxy,photonics
更新于2025-09-23 15:19:57
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Multi-octave spanning, Watt-level ultrafast mid-infrared source
摘要： We present a source of brilliant mid-infrared radiation, seamlessly covering the wavelength range between 1.33 and 18 μm (7500–555 cm?1) with three channels, employing broadband nonlinear conversion processes driven by the output of a thulium-fiber laser system. The high-average-power femtosecond frontend delivers a 50 MHz train of 250 fs pulses spectrally centered at 1.96 μm. The three parallel channels employ soliton self-compression in a fused-silica fiber, supercontinuum generation in a ZBLAN fiber, and difference-frequency generation in GaSe driven by soliton self-compressed pulses. The total output enables spectral coverage from 1.33 to 2.4 μm, from 2.4 to 5.2 μm, and from 5.2 to 18 μm with 4.5 W, 0.22 W and 0.5 W, respectively. This spatially coherent source with a footprint of less than 4 m2 exceeds the brilliance of 3rd-generation synchrotrons by more than three orders of magnitude over 90% of the bandwidth.
关键词： intra-pulse difference frequency generation (DFG),ultrafast optics,supercontinuum generation,mid-infrared generation,ZBLAN optical fibre,nonlinear optics
更新于2025-09-23 15:19:57
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Ultra-long carrier lifetime in neutral graphene-hBN van der Waals heterostructures under mid-infrared illumination
摘要： Graphene/hBN heterostructures are promising active materials for devices in the THz domain, such as emitters and photodetectors based on interband transitions. Their performance requires long carrier lifetimes. However, carrier recombination processes in graphene possess sub-picosecond characteristic times for large non-equilibrium carrier densities at high energy. An additional channel has been recently demonstrated in graphene/hBN heterostructures by emission of hBN hyperbolic phonon polaritons (HPhP) with picosecond decay time. Here, we report on carrier lifetimes in graphene/hBN Zener-Klein transistors of ~30 ps for photoexcited carriers at low density and energy, using mid-infrared photoconductivity measurements. We further demonstrate the switching of carrier lifetime from ~30 ps (attributed to interband Auger) down to a few picoseconds upon ignition of HPhP relaxation at finite bias and/or with infrared excitation power. Our study opens interesting perspectives to exploit graphene/hBN heterostructures for THz lasing and highly sensitive THz photodetection as well as for phonon polariton optics.
关键词： photodetectors,mid-infrared,phonon polaritons,van der Waals heterostructures,THz,Graphene,carrier lifetime,hBN
更新于2025-09-23 15:19:57
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Tunability of the Freea??Spectral Range by Microwave Injection into a Mida??Infrared Quantum Cascade Laser
摘要： The free-spectral range (FSR) of quantum cascade lasers (QCLs) emitting at 4.7 μm can be tuned through direct microwave modulation. The intrinsic short carrier lifetime of inter-subband transitions, along with impedance matched electrical packaging, allows a high-speed modulation up to more than 30 GHz. A signi?cant broadening and ?attening of the lasing spectrum is observed under radio frequency (RF) injection with frequencies close to the round-trip cavity. An accurate analysis of the high resolution spectra of the laser shows a comb-like regime for both free-running and RF modulated QCLs, if the modulation frequency is within the locking-range of the device. One of the main advantages of collecting high-resolution mid-infrared spectra, over the plain investigation of the beatnote in the microwave region, is the access to all the longitudinal modes and thus the accurate measure of the FSR over the whole optical spectrum. The use of high-resolution spectroscopy provides an in-depth and comprehensive analysis of lasing spectra under microwave modulations.
关键词： quantum devices,mid-infrared region,injection locking,tunability of the free-spectral-range,ultrafast devices
更新于2025-09-23 15:19:57
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Evaluation of baking performance by means of mid-infrared imaging
摘要： The present work aims to validate mid-infrared imaging as a promising method for evaluating oven systems. Therefore, a novel approach by analyzing mid-infrared radiation patterns captured by a thermal camera and subsequent image processing was developed. A thermal camera was adapted to two di?erent oven systems: a standard electric deck oven and a novel gas-?red baking oven with integrated volumetric ceramic burners (VCBs). The baked goods were analyzed and key indicators describing the ?nal product quality were determined. Speci?c volume, surface browning and mid-infrared image processing demonstrated a comparable performance of both oven systems. Furthermore, the determined surface heat homogeneity of the items to be baked was 0.65 ± 0.05 (–) for the electronic oven and 0.70 ± 0.03 (–) for the VCB oven. The proposed approach proved its fundamental quali?cation for comparing and evaluating di?erent oven systems.
关键词： Oven system evaluation,Baking monitoring,Image processing,Mid-infrared
更新于2025-09-23 15:19:57