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Polycrystal Synthesis, Crystal Growth, Structure, and Optical Properties of AgGaGe <sub/><i> <i>n</i> </i> </sub> S <sub/> 2( <i> <i>n</i> </i> +1) </sub> ( <i>n</i> = 2, 3, 4, and 5) Single Crystals for Mid-IR Laser Applications
摘要： AgGaGenS2(n+1) crystal is a series of quaternary for mid-IR laser applications of nonlinear optical materials converting a 1.064 μm pump signal (Nd:YAG laser) to 4?11 μm laser output, but only AgGaGeS4 has attracted the most attention, remaining the other promising AgGaGenS2(n+1) crystal whose physicochemical properties can be modulated by n value. In this work, AgGaGenS2(n+1) (n = 2, 3, 4, and 5) polycrystals are synthesized by vapor transport and mechanical oscillation method with di?erent cooling processes. High-resolution X-ray di?raction analysis and re?nement have revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2, resulting in the excellent nonlinear optical property, and the distortion of tetrahedron with the variation of n value causes the discrepancy of physicochemical property. Besides, using the modi?ed Bridgman method, AgGaGenS2(n+1) single crystals with 15 mm diameter and 20?40 mm length have been grown. We have discussed the structure and composition of AgGaGenS2(n+1) by XPS spectra and analyzed the three kinds of vibration modes of tetrahedral clusters by the Raman spectra. The Hall measurement indicates that the AgGaGenS2(n+1) single crystals are p-type semiconductor, and the carrier concentration decreases with the increasing n value. All the transmittances of as-grown AgGaGenS2(n+1) samples exceeds 60% in the transparent range, especially the transmittance of AgGaGe2S6, is up to 70% at 1064 nm, and the band gap of as-grown crystal increases from 2.85 eV for AgGaGe2S6 to 2.92 eV for AgGaGe5S12. After a thermal annealing treatment, the absorptions at 2.9, 4, and 10 μm have been eliminated, and the band gap changed into the range of 2.89?2.96 eV.
关键词： Hall measurement,nonlinear optical materials,thermal annealing treatment,vapor transport,AgGaGenS2(n+1),Bridgman method,Raman spectra,mid-IR laser applications,XPS spectra,mechanical oscillation method
更新于2025-11-14 15:27:09
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Pseudo-Continuous Flow FTIR System for Glucose, Fructose and Sucrose Identification in Mid-IR Range
摘要： In this paper, we present a new FTIR-based micro?uidic system for Glucose, Fructose and Sucrose detection. The proposed micro?uidic system is based on a pseudo-continuous ?ow coupled to a microscope-FTIR instrument. The detection and characterization of sugar samples were performed by recording their absorption spectrum in the wavelength range 700–1000 cm?1 of the Mid-IR region. The proposed pseudo-continuous ?ow system is designed to improve the uniformity of the sample distribution in the analyzed area versus conventional systems. The obtained results for different sugars concentrations, show a very low measurement error of 4.35% in the absorption peak intensity, which is ten times lower than the error obtained using the conventional measurements.
关键词： mid-IR absorption spectroscopy,absorption spectrum,FTIR spectroscopy,microscopy-FTIR spectrometer,sugars detection and quanti?cation,Glucose,Fructose,Sucrose,pseudo-continuous ?ow
更新于2025-09-23 15:21:21
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EXPRESS: Mid-Infrared Reflectance Spectroscopy of Oil Sands Minerals Based on Tunable Quantum Cascade Lasers
摘要： Minerals play an important role in the oil sands extraction efficiency. It is thus important to assess the major mineral abundance in oil sands ores. This paper presents the application of tunable quantum cascade lasers for mid-infrared reflectance spectroscopy on oil sands minerals. The investigations and results show a new tool to determine oil sands mineral type and to determine potentially quartz and clay contents.
关键词： Mid-infrared spectroscopy,mid-IR,reflectance spectroscopy,oil sands,QCL,quantum cascade lasers
更新于2025-09-23 15:21:01
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Review of tellurite glasses purification issues for mida??IR optical fiber applications
摘要： We reviewed the tellurite glass purification studies performed over the last 20 years, in particular dealing with the mid-infrared transmission performances. Best results are obtained under rich O2 atmosphere with platinum crucibles although Gibbs energy calculations show that other crucibles material are possible such as gold or alumina. From the point of view of the thermodynamics of involved oxidation reactions only, we identified the suitable conditions based on Gibbs energy calculations to be a synthesis temperature set above 900K and a O2 pressure around 105 Pa. The performances of the different purification technics were also compared. Finally, we analyzed the tellurite fibers recently optimized for mid-infrared which present low attenuation up to 4 μm allowing supercontinuum generation up to 5 μm.
关键词： tellurite glasses,supercontinuum generation,optical fiber,purification,mid-IR
更新于2025-09-23 15:21:01
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Noise and spectral stability of deep-UV gas-filled fiber-based supercontinuum sources driven by ultrafast mid-IR pulses
摘要： Deep-UV (DUV) supercontinuum (SC) sources based on gas-filled hollow-core fibers constitute perhaps the most viable solution towards ultrafast, compact, and tunable lasers in the UV spectral region, which can even also extend into the mid-infrared (iR). noise and spectral stability of such broadband sources are key parameters that define their true potential and suitability towards real-world applications. In order to investigate the spectral stability and noise levels in these fiber-based DUV sources, we generate an SC spectrum that extends from 180 nm (through phase-matched dispersive waves - DWs) to 4 μm by pumping an argon-filled hollow-core anti-resonant fiber at a mid-IR wavelength of 2.45 μm. We characterize the long-term stability of the source over several days and the pulse-to-pulse relative intensity noise (RIN) of the DW at 275 nm. The results indicate no sign of spectral degradation over 110 hours, but the RIN of the DW pulses at 275 nm is found to be as high as 33.3%. Numerical simulations were carried out to investigate the spectral distribution of the RIN and the results confirm the experimental measurements and that the poor noise performance is due to the high Rin of the mid-IR pump laser, which was hitherto not considered in numerical modelling of these sources. The results presented herein provide an important step towards an understanding of the noise mechanism underlying such complex light-gas nonlinear interactions and demonstrate the need for pump laser stabilization.
关键词： Deep-UV,supercontinuum sources,spectral stability,ultrafast mid-IR pulses,gas-filled fiber,noise
更新于2025-09-23 15:19:57
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Room temperature low frequency noise in n <sup>+</sup> -InAs/n-InAsSbP/InAs/p-InAsSbP double heterostructure infrared photodiodes
摘要： Low frequency forward current noise as well as the photocurrent noise are studied in InAsSbP/InAs double heterostructure (DH) photodiodes, in the frequency range 1–104 Hz. The photocurrent noise in DH photodiodes is signi?cantly lower than in single heterostructure (SH) photodiodes. The forward current noise in a DH diode exhibiting the 1/f frequency dependence is also much lower than that in SH diodes. However, in some DH diodes, it is the generation-recombination mechanism that provides the dominant contribution to the forward current noise; in this case the noise level is signi?cantly higher. At suf?ciently high forward current densities, the noise decreases with current. The observed generation-recombination noise spectrum cannot be described within the conventional theory.
关键词： InAs photodiodes,low frequency noise,forward bias,photocurrent noise,Mid-IR photodetectors
更新于2025-09-19 17:13:59
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Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source
摘要： Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (mid-IR) spectroscopy for decades. Supercontinuum laser sources operating in the mid-IR spectral region now offer the potential to enrich the field of FT-IR spectroscopy due to their distinctive properties, such as high-brightness, broadband spectral coverage and enhanced stability. In our contribution, we introduce this advanced light source as a replacement for conventional thermal emitters. Furthermore, an approach to efficient coupling of pulsed mid-IR supercontinuum sources to FT-IR spectrometers is proposed and considered in detail. The experimental part is devoted to pulse-to-pulse energy fluctuations of the applied supercontinuum laser, performance of the system, as well as the noise and long-term stability. Comparative measurements performed with a conventional FT-IR instrument equipped with a thermal emitter illustrate that similar noise levels can be achieved with the supercontinuum-based system. The analytical performance of the supercontinuum-based FT-IR spectrometer was tested for a concentration series of aqueous formaldehyde solutions in a liquid flow cell (500 mm path length) and compared with the conventional FT-IR (130 mm path length). The results show a four-times-enhanced detection limit due to the extended path length enabled by the high brightness of the laser. In conclusion, FT-IR spectrometers equipped with novel broadband mid-IR supercontinuum lasers could outperform traditional systems providing superior performance, e.g., interaction path lengths formerly unattainable, while maintaining low noise levels known from highly stable thermal emitters.
关键词： Mid-infrared spectroscopy,mid-IR,supercontinuum laser source,Fourier transform infrared spectroscopy,FT-IR
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Fiber Source for Generation of Tunable Broadband f <sub/>CEO</sub> -Free Mid-IR Pulses for Laser Spectroscopy Applications
摘要： Recent decade brought a tremendous progress laser-based gas detection techniques. This progress would not be possible without the relentless devotion of the scientific community in developing state-of-the-art sources capable of targeting strong absorption lines of gases localized in the mid-infrared (mid-IR) wavelength region. Although narrowband, semiconductor-based mid-IR lasers offer non-complex implementation their tuning range is usually limited to several cm-1. Therefore designing a sensor capable of simultaneous monitoring of several gas species, even with absorption profiles clustered nearby, requires incorporating individual expensive quantum cascade laser (QCL) or interband cascade laser (ICL) sources into a single platform. Recent development of reliable mid-IR comb sources, combined with clever methods of signal processing allowed for designing gas sensors capable of simultaneous monitoring of several gas analytes in fractions of a second [1]. Obtaining broadband pulsed radiation in the mid-IR region is usually accomplished by utilizing nonlinear conversion or in recently presented on-chip QCL combs [2]. Although QCL combs offer compactness and efficiency they do not allow straightforward control of the repetition frequency (frep) or the carrier-envelope offset frequency (fCEO), which are critical in some particular cavity-enhanced comb-based sensing techniques, e.g. Vernier spectroscopy [3]. Here we present a fully-fiberized, fCEO-free mid-IR optical frequency comb source capable of covering 6 – 9 μm wavelength region with tunable frep. The setup of the source is presented in Fig 1. The heart of the source is a ring-cavity graphene mode-locked laser generating sub-250 fs pulses at 1560 nm and frep of 100 MHz. The pulses are split using a 50/50 coupler and directed to separate sections of the source. In the blue section the source the pulses are amplified to 80 mW in an all-fiber-based chirped pulse amplifier (CPA) and recompressed in a 8 m-long section of PM1550 fiber to ~200 fs. In the red section a custom manufactured nonlinear fiber with tailored dispersion (PCF) is utilized to soliton-shift the 1.56 μm pulses into the 1.9 - 2 μm wavelength region. Subsequently the pulses are amplified in a CPA and recompressed to ~200 fs. Combined 1.56 and 2 μm pulses are focused on a 3 mm-long orientation patterned gallium phosphide (OP-GaP) crystal to generate mid-IR radiation via differential frequency generation (DFG). Since both pulses originated from the same ML source, the generated mid-IR frequency comb is inherently fceo-free and can be used in laser-based gas sensors requiring stable carrier-envelope offset. The source is built entirely from PM single-mode fibers.
关键词： mid-IR,optical frequency comb,laser spectroscopy,fCEO-free,gas detection
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Comparative Study of High Order Harmonic Generation in Monolayer-Thick Semiconductors
摘要： In this contribution we report on the results of an experimental comparative study of high order harmonic generation (HHG) from strong mid-IR femtosecond laser pulses in two-dimensional (2D) materials consisting of a single layer. Beside their promising application in electronics and photonics, these materials allow to study microscopic light-condensed-matter interaction on the atomic scale. HHG in 2D materials, in comparison to a bulk, have several distinct qualitative features: single atom layer essentially excludes propagation effects and minimizes absorption, whereas weak charge screening results in significantly higher exciton binding energy. Here we report on comparative study of intensity and polarization dependence of HHG in polycrystalline single layers of MoS2 and WS2.
关键词： WS2,MoS2,mid-IR femtosecond laser pulses,2D materials,high order harmonic generation
更新于2025-09-16 10:30:52
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From CuFeS <sub/>2</sub> to Ba <sub/>6</sub> Cu <sub/>2</sub> FeGe <sub/>4</sub> S <sub/>16</sub> : rational band gap engineering achieves large second-harmonic-generation together with high laser damage threshold
摘要： A new germanium-based sulfide, Ba6Cu2FeGe4S16, achieves a band-gap broadening of more than 1 eV relative to CuFeS2. Remarkably, Ba6Cu2FeGe4S16 exhibits excellent comprehensive NLO performance (SHG, 1.5 (cid:2) AgGaSe2; LDT, 2 (cid:2) AgGaSe2), satisfying the essential requirements of mid-IR NLO candidates.
关键词： laser damage threshold,mid-IR NLO materials,germanium-based sulfide,second-harmonic-generation,band-gap engineering
更新于2025-09-16 10:30:52