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Ba10Zn7M6Q26: Two New Mid-infrared Nonlinear Optical Crystals with T2 Supertetrahedron 3D Framework
摘要： Two new mid-infrared (MIR) nonlinear optical (NLO) chalcogenide crystals, Ba10Zn7In6S26, 1 and Ba10Zn7Ga6Se26, 2 are discovered by traditional solid state reactions. 1 and 2 are isostructural and they represent a novel three-dimensional (3D) framework made by apexe-sharing T2 supertetrahedron 2D layers that are stacked alternately by another kind of T2 supertetrahedra though sharing apexes along the c direction, with T1 tetrahedra inserting in the tunnels and Ba2+ cations locating both in the voids and tunnels. Among them, 1 shows attractive MIR NLO properties of a wide band gap of 3.0 eV, a strong second harmonic generation (SHG) signal about 4.1 times that of the commercial AgGaS2 at particle sizes of 30–46 μm under a 2.05 μm laser radiation, and a high LDT of 37.2 times that of benchmark AgGaS2 at particle sizes of 150–210 μm under a 1.064 μm laser radiation. This distinguishes 1 as a new promising MIR NLO material. In addition, the density functional theory (DFT) analyses suggest that the SHG response of 1 comes mainly from the electronic transitions from S 3p to Ba 5d, Zn 4s, Zn 3d, In 5s, In 5p states.
关键词： chalcogenide,mid-infrared,second harmonic generation,laser damage threshold,nonlinear optical,supertetrahedron
更新于2025-09-04 15:30:14
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Spectral interval optimization on rapid determination of prohibited addition in pesticide by ATR‐FTIR
摘要： BACKGROUND: Acetamiprid, as a low toxicity pesticide, had already been extensively used to increase plant production and quality. Although fipronil had been prohibited, it was usually illicitly added to acetamiprid due to its particular insecticidal action and effect, so it was highly desirable to obtain a rapid and effective method to detect its concentration. Mid-Infrared spectroscopy (MIR) technique combined with two variable selection methods, interval combination optimization (ICO) and interval partial least squares (iPLS), were used to determinate the prohibited addition of fipronil. RESULTS: The full spectra for both ICO and iPLS were divided into forty equal-width intervals. Consequently, 45 and 135 characteristic variables were extracted from ICO and iPLS to establish the models. Compared with iPLS, the ICO model acquired a more suitable spectral region and as a result gained a higher prediction accuracy. Specifically, ICO method selected the characteristic wavelengths ascribed to C-F and C-N (in five-membered heterocyclics), iPLS chose the intervals associated with C-F and S=O. CONCLUSION: Results revealed that MIR combined with ICO could be efficiently used for rapid identification of illegal addition and had a great potential to provide on-site pesticide quality control.
关键词： pesticide,partial least squares,interval combination optimization,Mid-infrared spectroscopy,interval partial least squares
更新于2025-09-04 15:30:14
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Metamorphic InAs(Sb)/InGaAs/InAlAs nanoheterostructures grown on GaAs for efficient mid-IR emitters
摘要： High-efficiency semiconductor lasers and light-emitting diodes operating in the 3–5 μm mid-infrared (mid-IR) spectral range are currently of great demand for a wide variety of applications, in particular, gas sensing, noninvasive medical tests, IR spectroscopy etc. III-V compounds with a lattice constant of about 6.1 ? are traditionally used for this spectral range. The attractive idea to fabricate such emitters on GaAs substrates by using In(Ga,Al)As compounds is restricted by either the minimum operating wavelength of ～8 μm in case of pseudomorphic AlGaAs-based quantum cascade lasers or requires utilization of thick metamorphic InxAl1-xAs buffer layers (MBLs) playing a key role in reducing the density of threading dislocations (TDs) in an active region, which otherwise result in a strong decay of the quantum efficiency of such mid-IR emitters. In this review we present the results of careful investigations of employing the convex-graded InxAl1-xAs MBLs for fabrication by molecular beam epitaxy on GaAs (001) substrates of In(Ga,Al)As heterostructures with a combined type-II/type-I InSb/InAs/InGaAs quantum well (QW) for efficient mid-IR emitters (3–3.6 μm). The issues of strain relaxation, elastic stress balance, efficiency of radiative and non-radiative recombination at T = 10–300 K are discussed in relation to molecular beam epitaxy (MBE) growth conditions and designs of the structures. A wide complex of techniques including in-situ reflection high-energy electron diffraction, atomic force microscopy (AFM), scanning and transmission electron microscopies, X-ray diffractometry, reciprocal space mapping, selective area electron diffraction, as well as photoluminescence (PL) and Fourier-transformed infrared spectroscopy was used to study in detail structural and optical properties of the metamorphic QW structures. Optimization of the growth conditions (the substrate temperature, the As4/III ratio) and elastic strain profiles governed by variation of an inverse step in the In content profile between the MBL and the InAlAs virtual substrate results in decrease in the TD density (down to 3 × 107 cm?2), increase of the thickness of the low-TD-density near-surface MBL region to 250–300 nm, the extremely low surface roughness with the RMS value of 1.6–2.4 nm, measured by AFM, as well as rather high 3.5 μm-PL intensity at temperatures up to 300 K in such structures. The obtained results indicate that the metamorphic InSb/In(Ga,Al)As QW heterostructures of proper design, grown under the optimum MBE conditions, are very promising for fabricating the efficient mid-IR emitters on a GaAs platform.
关键词： Buffer layer,Non-radiative recombination,Mid-infrared emitters,Photoluminescence,Metamorphic heterostructures,InSb,InAs,Structural properties,Molecular beam epitaxy,Nanostructures,In(Ga,Al)As ternary alloys,Threading dislocations,Quantum well
更新于2025-09-04 15:30:14
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Wavelength dependence of high-order harmonic yields in solids
摘要： We theoretically investigate the wavelength dependence of high-order harmonic yields in solids driven by a mid-infrared laser field. By solving the three-dimensional two-band density matrix equations in the wavelength range of 2.0–7.5 μm, it is shown that, in the limit of slow dephasing (dephasing time T2 → ∞), the high-order harmonic yield from a crystal follows a scaling of λ?4 for a fixed energy interval. The λ?4 scaling is attributed to the wave-packet spreading (λ?3) for the overall yield and the energy distribution effect (λ?1) due to the increase of the cutoff. For the crystal with a finite dephasing time T2, we find that the exponential factor x of λ?x increases with a decay of T2. An apparent and rapid fluctuation on a fine wavelength mesh is also observed in the harmonic yields. The fine-scale oscillation originates from the quantum interference effect, and the corresponding modulation period δλ scales as λ?1.
关键词： high-order harmonic generation,solids,wavelength dependence,mid-infrared laser field,quantum interference
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE Photonics Conference (IPC) - Reston, VA, USA (2018.9.30-2018.10.4)] 2018 IEEE Photonics Conference (IPC) - All-Chalcogenide Single-Mode Couplers
摘要： We demonstrate the fabrication of all-chalcogenide single-mode fiber couplers with a coupling extinction ratio of up to 35 dB. Couplers are made in two formats: wavelength-dependent and polarization beamsplitters with separation of the orthogonally polarized components up to 18 dB.
关键词： polarizing beamsplitter,single-mode coupler,mid-infrared
更新于2025-09-04 15:30:14
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EXPRESS: Mid-Infrared Polarization Spectroscopy Measurements of Species Concentrations and Temperature in a Low-Pressure Flame
摘要： We demonstrate quantitative measurements of methane (CH4) mole fractions in a low pressure fuel-rich premixed dimethyl ether/oxygen/argon flat flame (Φ =1.87, 37 mbar) using mid-infrared polarization spectroscopy (IRPS). Nonintrusive in situ detection of CH4, acetylene (C2H2), and ethane (C2H6) in the flame was realized by probing the fundamental asymmetric C–H stretching vibration bands in the respective molecules in the spectral range 2970–3340 cm–1. The flame was stabilized on a McKenna-type porous plug burner hosted in a low pressure chamber. The temperature at different heights above the burner (HAB) was measured from the line ratio of temperature sensitive H2O spectral lines recorded using IRPS. Quantitative measurements of CH4 mole fractions at different HAB in the flame were realized by a calibration measurement in a low pressure gas flow of N2 with a small admixture of known amount of CH4. A comprehensive study of the collision effects on the IRPS signal was performed in order to quantify the flame measurement. The concentration and temperature measurements were found to agree reasonably well with simulations using Chemkin. These measurements prove the potential of IRPS as a sensitive, nonintrusive, in situ technique in low pressure flames.
关键词： dimethyl ether,methane,Mid-infrared polarization spectroscopy,quantitative concentrations,low pressure flame,temperature
更新于2025-09-04 15:30:14