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Efficient cascaded wavelength conversion based on Stark-chirped rapid adiabatic passage
摘要： We demonstrate a highly efficient process of cascaded wavelength conversion among three states that is based on the Stark-chirped rapid adiabatic passage technique, and enables the achievement of nearly complete wavelength conversion in the mid-infrared laser generation process. By analyzing the relevant parameters in the model, we identify various factors that affect the efficiency of the conversion process. Compared with traditional cascaded wavelength conversion based on the technique of stimulated Raman adiabatic passage, the new conversion process not only maintains a high efficiency but also keeps the intermediate frequency strength low along the interacting length and achieves better stability when the relevant parameters change.
关键词： Stark-chirped rapid adiabatic passage,efficiency,cascaded wavelength conversion,stability,mid-infrared laser
更新于2025-09-23 15:22:29
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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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Quantification of calcium in infant formula using laser-induced breakdown spectroscopy (LIBS), Fourier transform mid-infrared (FT-IR) and Raman spectroscopy combined with chemometrics including data fusion
摘要： Laser-induced breakdown spectroscopy (LIBS), Fourier transform mid-infrared (FT-IR) and Raman spectroscopy combined with chemometrics were investigated to quantify calcium (Ca) content in infant formula powder (INF). INF samples (n=51) with calcium content levels (ca. 6.5-30 mg Ca/100kJ) were prepared in accordance with the guidelines of Commission Directive 2006/125/EC. Atomic absorption spectroscopy (AAS) was used as the reference method for Ca content determination. To predict Ca content in INF samples, partial least squares regression (PLSR) models that developed based on LIBS, Raman and FT-IR spectral data, respectively. The model developed using LIBS data achieved the best performance for the quantification of Ca content in INF (R2 (cross-validation (CV))-0.99, RMSECV-0.29 mg/g; R2 (prediction (P))-1, RMSEP-0.63 mg/g). PLSR models that developed based on data fusion of Raman and FT-IR spectral features obtained the second best performance (R2CV-0.97, RMSECV-0.38 mg/g; R2P-0.97, RMSEP-0.36 mg/g). This study demonstrated the potential of LIBS, FT-IR and Raman spectroscopy to accurately quantify Ca content in INF.
关键词： Fourier transform mid-infrared,laser-induced breakdown spectroscopy,chemometrics,Raman spectroscopy,calcium,infant formula
更新于2025-09-23 15:19:57
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Investigation of Dy3+/Tm3+ co-doped ZrF4-BaF2-YF3-AlF3 fluoride glass for efficient 2.9?μm mid-infrared laser applications
摘要： Different doping concentrations of Dy3+/Tm3+ in ZrF4-BaF2-YF3-AlF3 (ZBYA) fluoride glass samples were prepared by the melt-quenching method. Spectroscopic properties were analyzed through absorption (from 200 to 3300 nm) and emission spectra (from 1200 to 3200 nm). The spontaneous radiative transition probability, branching ratio and radiative lifetime of various energy levels transition were calculated based on the Judd-Ofelt theory. The emission cross-section value of the 1 mol% Dy3+/1 mol% Tm3+ co-doped ZBYA sample at 2.9 μm were calculated as 3.79 10-21 cm2. Near- and mid-IR emission spectra of Dy3+/Tm3+ co-doped ZBYA-fluoride glass under the excitation of 808 nm laser diode were investigated and discussed. Analysis of the emission spectra and the energy transition process of Dy3+/Tm3+ co-doped glass indicated that the introduction of Tm3+ ions can effectively improve the mid-infrared fluorescence intensity of Dy3+ ions, thus the Dy3+/Tm3+ co-doped ZBYA-fluoride glass can be an excellent candidate material for 2.9 μm mid-infrared laser applications.
关键词： Dy3+/Tm3+ co-doped,mid-infrared laser,ZBYA fluoride glass
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 4th Optoelectronics Global Conference (OGC) - Shenzhen, China (2019.9.3-2019.9.6)] 2019 IEEE 4th Optoelectronics Global Conference (OGC) - Theoretical Evaluation of a Pulsed Mid-Infrared Ho <sup>3+</sup> :BaY <sub/>2</sub> F <sub/>8</sub> Laser
摘要： In this study, we construct a theoretical model to analyze the output characteristics of a pulsed Ho3+:BaY2F8 (Ho3+:BYF) laser by taking both energy transfer up-conversion (ETU) and cross relaxation (CR) processes into account. The influences of the pump energy, pulse width, reflectance of an output coupler (OC), crystal length, and Ho3+ doping concentration on the physical performances are investigated in detail for an end-pumped structure. The calculation results reveal that the proper length of a Ho3+:BaY2F8 crystal is from 5 to 10 mm for the Ho3+ doping concentration of 10-40 at.%. We also deduce that a high output can be obtained when the Ho3+ doping concentration is selected as 30 at.%. It has been demonstrated that the relaxation oscillation of a Ho:BYF laser can be observed for a pulsed pump source. We can see that the threshold peak power of a pump light source decreases with the increase of the pulse width. The conclusions might be useful for the realization of a pulsed mid-infrared Ho3+:BYF laser.
关键词： rate equations,mid-infrared laser,directly-pumped,Ho3+:BaY2F8
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) - Cr,Fe:ZnMnSe Laser Excited by Flash-Lamp Pumped Er:Glass Laser
摘要： Due to the wide use of coherent radiation in the mid-infrared (IR) region, the attention has been paid to both direct and indirect methods of generation of this radiation over the past two decades. While indirect methods are based on nonlinear conversion (OPOs or Raman scattering), the direct approach looks for a new active media that will allow generation of radiation in the mid-IR region in a single step [1]. It has been found that by replacing Zn2+ ions with Mn2+, Mg2+ or Cd2+ ions with comparable size in the ZnSe matrix, the position of the absorption and emission bands is shifted to the longer wavelengths by increasing concentration of these ions substitution [1, 2]. It allows a one laser oscillator to extend or to shift the emission spectrum further to the mid-IR part of the electromagnetic spectrum, which was previously exclusively based on the nonlinear processes or on the parametric generation.
关键词： Cr,mid-infrared,laser,spectral properties,Er:glass laser,Fe:ZnMnSe
更新于2025-09-12 10:27:22
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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) - Dispersive Fourier Transform Based Single-Shot CEP Drift Measurement at Arbitrary Repetition Rate
摘要： In recent years attosecond science motivated the development of laser systems, which provide millijoule energy level few-cycle pulses. These experiments rely on a field with stable amplitude and carrier envelope phase (CEP) to provide reproducible results [1]. As a consequence, diagnostic devices, which are capable of single-shot CEP measurement and pulse tagging, became a must-have equipment in today’s laser systems. The self-referenced interferometry such as f-to-2f [2] are one of the most typical way to characterize the shift of the CEP in a single-shot manner. The highest achievable recording rate is mostly limited by the measurement times of the optical spectroscopes, which can only reach 10 kHz even with fast detector array. Dispersive Fourier Transform (DFT) [3,4] can be used to bypass this limitation, so single-shot recordings of the output signal of an f-to-2f interferometer becomes possible even at high repetition rates. The method depends on an optical element with enough dispersion to stretch to pulse duration up to the nanosecond range. Therefore, the spectral modulation pattern containing the encoded CEP appears in the temporal domain, which allows for tracking with a relatively slow photodetector. To demonstrate the validity and performance of this concept, a CEP drift measurement was performed on the state-of-the-art mid-infrared (MIR) laser system at ELI-ALPS [5], which provides mid-IR laser pulses at 100 kHz. As a comparison, an alternative measurement was performed in parallel with a grating spectrometer (Fringeezz, Fastlite) [6] at 10 kHz sampling rate. The two recorded signals were synchronized and a decimated 10 kHz subset was extracted, where correlation between measurements is the highest. One of the main limitation of the DFT method originates from the time jitter between the output of the laser and the TTL signal used for triggering. This time jitter changes the time delay of the modulation pattern, creating an additional noise source for the measured relative CEP value. In order to perform truly time jitter-free single-shot CEP drift measurement, an additional CEP independent spectral modulation was introduced, which can be used to determine the noise originating from the jitter. The jitter-free decimated dataset against the grating spectrometer measurement is displayed on Fig. 1. The calculated CEP noises are summarized in Table 1. These values agree within the limit of the uncertainty of these measurements, validating that this new CEP drift measurement method is easily scalable to arbitrary repetition rates.
关键词： high repetition rate,mid-infrared laser system,Dispersive Fourier Transform,CEP drift measurement,single-shot
更新于2025-09-12 10:27:22
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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) - Numerical Simulations of THz Generation with two-Color Mid-Infrared Laser Pulse and Relative Phase Control
摘要： The generation of terahertz (THz) radiation by two-color laser pulse induced gas plasma is an actively researched topic since its exploration [1]. It is a tabletop, powerful spectroscopic tool in the far-infrared spectral regime. The THz spectroscopy is capable to identify chemicals in a nondestructive way [2]. It is capable to generate THz radiation by remotely more than 100m from the laser system [3], the remote sensing of the THz radiation also possible [4]. By the combination of the former mentioned features, the THz spectroscopy is a powerful tool to identify drugs, poisons and explosives with remotely in a nondestructive way.
关键词： spectroscopy,relative phase control,gas plasma,two-color mid-infrared laser pulse,THz generation
更新于2025-09-12 10:27:22
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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) - Spectral Luminescence Properties of Ho <sup>3+</sup> Ions in Active Media Codoped with Tb <sup>3+</sup> , Pr <sup>3+</sup> and Yb <sup>3+</sup> for Mid-Infrared Laser Development
摘要： Lasers operating in mid-infrared spectral region specifically with 3 m wavelength attract a lot of attention due to their various applications in atmospheric monitoring, medical surgery, remote sensing and scientific research. Such laser can be used as an efficient and high-quality radiation source for optical parametric oscillators and converters to longer IR wavelengths. Laser active media doped with Ho3+ ions are of interest for obtaining the radiation in this spectral range. However the realization of the laser radiation at 5I6 → 5I7 optical transition in Ho3+ ions is a complicated task due to the lack of commercially available laser diodes for efficient pumping of Ho3+ ions. Yb3+ ion is known as an efficient sensitizer for Ho3+ ions in various laser active crystals. The scheme with the excitation transfer from Yb3+ to Ho3+ was realized in Cr:Yb:Ho:YSGG and Cr:Yb:Ho:Eu:YAP lasers with flash lamp pumping [1, 2] and Ho:Yb:GGG and Ho:Yb:YSGG lasers with diode pumping [3]. In addition 5I6 → 5I7 optical transition is known as a “self-terminating” one because the fluorescence lifetime of the lower laser level 5I7 is considerably larger than that of the upper laser level 5I6. Codoping of Ho3+ active media with Tb3+ or Pr3+ ions can accelerate the deactivation process of the lower laser level. The concentration set of CaF2 crystal doped with Ho3+, Yb3+, Tb3+, Pr3+ ions was grown using the Bridgman technique. The number of Gd2O3, Y2O3 single crystal fibers doped with the same ions was successfully obtained by laser-heated pedestal growth method. Absorption spectra of Yb:Ho:Gd2O3 and Yb:Ho:Pr:Gd2O3 crystals showed that Yb3+ doping increased the absorption coefficient within 850-1050nm spectral region and make Yb doped media suitable for efficient pumping by commercially available laser diodes. The fluorescence lifetime of 5I6 and 5I7 manifolds of Ho3+ ions was investigated in CaF2 crystals codoped with Tb3+ and Pr3+ ions. It was found that this codoping resulted in the depopulation of the lower laser level 5I7 in Ho3+ ions and at the same time had little influence on the upper laser level 5I6 (Table 1). The lifetime of the lower laser level reduced from 17.5 ms for Yb:Ho:CaF2 crystal to 0.75 ms for Yb:Ho:Tb:CaF2. Deactivation effect of lower laser level 5I7 in Ho3+ was also observed in Yb3+:Ho3+:Pr3+:Gd2O3 and Yb3+:Ho3+:Tb3+:Gd2O3 single crystal fibers. The lifetime of the lower laser level 5I7 decreased from 8.25 ms to 1.04 ms and to 0.67 ms with a codoping of 0.5 at.% Pr3+ and 0.5 at.% Tb3+ ions, respectively. The use of Yb3+, Tb3+ or Pr3+ codoping with Ho3+ to enhance the laser properties of Ho3+ ions at 5I6→5I7 optical transition at the wavelength of ~2.8-3 μm were investigated in the Gd2O3, Y2O3 single crystal fiber for the first time. Obtained results indicate that single crystal fiber Yb3+:Ho3+:Tb3+:Gd2O3 and CaF2 :Yb3+:Ho3+:Tb3+ crystal is a promising laser medium for developing compact LD-pumped lasers operating at the wavelength of 2.8-3 μm.
关键词： Pr3+ ions,Tb3+ ions,mid-infrared laser,fluorescence lifetime,laser active media,Ho3+ ions,Yb3+ ions
更新于2025-09-11 14:15:04
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Growth, spectroscopic, diode-pumped mid-infrared laser properties of Er:GSAG crystal
摘要： A great potential mid-infrared laser crystal of heavily Er3+ doped GSAG crystal with high optical quality is successfully grown by Cz method. The crystal quality of Er:GSAG crystal is determined by XRC. The structure parameters of Er:GSAG crystal are obtained by the X-ray Rietveld refinement method (a=b=c=12.3196?). The absorption cross section at 961nm and 967 nm are 0.381 × 10-21 cm2 and 0.414 × 10-21 cm2, respectively. The 962 nm laser diode end-pumped Er:GSAG laser operated at 2828 nm is demonstrated for the first time. The performance of Er:GSAG laser is investigated in great detail. A maximum output power of Er:GSAG laser is 410 mW when pumped by 962 nm LD at 300 Hz and 0.5 ms. Simulating results display the highest temperatures of Er:GSAG laser spot is 345.8 K, indicating a small thermal lensing effect of Er:GSAG crystal. Besides, the laser performance of Er:GSAG crystals which irradiate by different doses of gamma-ray are used to investigated its potential for working in the radiation resistance environment. The results show the relatively minor differences on the Er:GSAG lasers performance, indicating a great potential of Er:GSAG crystal in radiant environment application.
关键词： Er:GSAG,Mid-infrared laser,Radiation resistant,Crystal structure,Absorption spectrum
更新于2025-09-11 14:15:04