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Milliwatt-Level Spontaneous Emission Across the 3.5a??8 ?μm Spectral Region from Pr3+ Doped Selenide Chalcogenide Fiber Pumped with a Laser Diode
摘要： A spontaneous emission fiber source operating in the mid-infrared (MIR) wavelength range from 3.5 to 8 μm is demonstrated for the first time at output power levels of at least 1 mW. The source is a Pr3+-doped selenide chalcogenide, multimode, glass fiber pumped with commercially available laser diodes operating at 1.470 μm, 1.511 μm and 1.690 μm. This MIR spontaneous emission fiber source offers a viable alternative to broadband mid-infrared supercontinuum fiber sources, which are comparatively complex and costly. The MIR emission wavelength range is significant for molecular sensing applications across biology and chemistry, and in medicine, agriculture, defense, and environmental monitoring.
关键词： mid-infrared,mid-infrared light sources,fiber lasers,chalcogenide glass fibers
更新于2025-09-19 17:13:59
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Forensic soil analysis using laser-induced breakdown spectroscopy (LIBS) and Fourier transform infrared total attenuated reflectance spectroscopy (FTIR-ATR): Principles and case studies
摘要： Soils are crucial trace evidence that can establish or exclude the relationship between a suspect, victim, or an object at a particular scene, which could contribute to building a case. Laser-induced breakdown spectroscopy (LIBS) and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy have been demonstrated to be effective techniques for soil characterization owing to its being rapid, non-destructive, and convenient analysis with little sample preparation requirements. Therefore, the principles of LIBS and FTIR-ATR techniques for soil forensic analysis in typical soil samples were investigated and their practical feasibility was tested by applying the techniques to forensic soil samples in two criminal cases. Principal component analysis (PCA) of a typical soil sample indicated that five typical soil types were clearly distinguished by LIBS and FTIR-ATR spectra. Variations in the soil elements (i.e., Si, Mg, Al, Ca, K, O, and N) and functional groups (i.e., O?H/N?H, C=C/C=O, Si?O, CO3 2?, Al?OH, and NH2) are crucial indicators for soil identification. The casework results demonstrated that both LIBS and FTIR-ATR show great potential for forensic soil analysis in future cases.
关键词： forensics,laser-induced breakdown spectroscopy,criminalistics,Soil identification,mid-infrared attenuated reflectance spectroscopy
更新于2025-09-19 17:13:59
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InGaAs Membrane Waveguide: A Promising Platform for Monolithic Integrated Mid-Infrared Optical Gas Sensor
摘要： Mid-infrared (mid-IR) absorption spectroscopy based on integrated photonic circuits has shown great promise in trace-gas sensing applications in which the mid-IR radiation directly interacts with the targeted analyte. In this paper, considering monolithic integrated circuits with quantum cascade lasers (QCLs) and quantum cascade detectors (QCDs), the InGaAs-InP platform is chosen to fabricate passive waveguide gas-sensing devices. Fully suspended InGaAs waveguide devices with holey photonic crystal waveguides (HPCWs) and sub-wavelength grating cladding waveguides (SWWs) are designed and fabricated for mid-infrared sensing at λ=6.15μm in the low index contrast InGaAs-InP platform. We experimentally detect 5 ppm ammonia with a 1 mm long suspended HPCW and separately with a 3 mm long suspended SWW, with propagation losses of 39.1 dB/cm and 4.1 dB/cm, respectively. Furthermore, based on the Beer-Lambert infrared absorption law and the experimental results of discrete components, we estimated the minimum detectable gas concentration of 84 ppb from a QCL/QCD integrated SWW sensor. To the best of our knowledge, this is the first demonstration of suspended InGaAs membrane waveguides in the InGaAs-InP platform at such a long wavelength with gas sensing results. Also, this result emphasizes the advantage of SWWs to reduce the total transmission loss and the size of the fully integrated device’s footprint by virtue of its low propagation loss and TM mode compatibility in comparison to HPCWs. This study enables the possibility of monolithic integration of quantum cascade devices with TM-polarized characteristics and passive waveguide sensing devices for on-chip mid-IR absorption spectroscopy.
关键词： sub-wavelength waveguides,gas sensing,absorption spectroscopy,photonic crystal waveguides,mid-infrared,photonics integrated circuits,quantum cascade devices,parts-per-billion
更新于2025-09-19 17:13:59
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Efficient Tm:LiYF4 Lasers at ～2.3 lm: Effect of Energy-Transfer Upconversion
摘要： The 3H4 → 3H5 transition of Thulium ions (Tm3+), which features laser emission at ~2.3 μm is studied in details. We revise the conditions for efficient laser operation using a rate- equation model accounting for the ground-state bleaching, cross- relaxation and energy-transfer upconversion (ETU). We show that ETU has a crucial role in reaching more than unity pump quantum efficiency (QE) for ~2.3 μm Tm lasers based on highly- doped crystals. A Ti:Sapphire pumped quasi-continuous-wave 3.5 at.% Tm:LiYF4 laser generated 0.73 W at 2306 nm with a record-high slope efficiency of 47.3% (versus the absorbed pump power, for double-pass pumping) featuring a QE of 1.27. Diode- pumping of this crystal yielded a peak output power of >2 W. The first 2.3 μm Tm waveguide laser is also reported based on Tm:LiYF4 epitaxial layers with even higher doping of 6.2 at.% generating 0.23 W with a slope efficiency of 19.8%. The spectroscopic properties of Tm:LiYF4 relevant for the ~2.3 μm laser operation are revised as well.
关键词： mid-infrared,spectroscopy,laser transitions,Solid-state lasers
更新于2025-09-19 17:13:59
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Ppb-level formaldehyde detection system based on a 3.6???μm interband cascade laser and mode-locked cavity enhanced absorption spectroscopy with self-calibration of the locking frequency
摘要： A mid-infrared formaldehyde (H2CO) detection system was demonstrated using a continuous-wave distributed-feedback interband cascade laser (DFB-ICL) emitting at 3.6 μm as light source and an assembly F-P cavity with 20 m effective optical path length as gas chamber. The laser and the cavity were locked to the H2CO absorption peak simultaneously by an electro-optic modulation based automatic Pound-Drever-Hall (PDH) scheme which consist of two steps: dynamic PDH locking and continuous PDH locking. Before continuous PDH locking, the dynamic PDH locking was conducted to acquire the H2CO absorption spectrum and calibration the locking frequency. Then, the cavity transmitted intensity was detected continuously to characterize the gas concentration. H2CO measurements were conducted to evaluate the performance of the sensor system. A linear relationship was observed between the voltage of the absorption signal and the H2CO concentration within the range of 0–6 ppm. Based on Allan deviation analysis, a minimum detection limit of 5.8 ppb was achieved with an averaging time of 30 s.
关键词： Cavity enhanced absorption spectroscopy,Mid-infrared,Interband cascade laser,Formaldehyde detection
更新于2025-09-19 17:13:59
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Study on Irradiation Effect of Mid-Infrared Free Electron Laser on Hen Egg-White Lysozyme by Using Terahertz-Time Domain Spectroscopy and Synchrotron-Radiation Vacuum-Ultraviolet Circular-Dichroism Spectroscopy
摘要： Mid-infrared free-electron laser (MIR-FEL) is potentially applicable for tissue ablation and dissociation of pathological peptide aggregates in medicine. However, it is still poorly understood how the MIR-FEL irradiation influences on functional proteins such as enzymes. In the current study, the effect of MIR-FEL on both aggregate and non-aggregate (= native) states of hen egg-white lysozyme (HEWL) as a representative enzyme has been investigated. Absorption intensity at terahertz region (0.3–1.2 THz, 10–40 cm?1) of the aggregate of HEWL was lower than that of the native HEWL, but the former was increased nearly to the same level with the latter after the MIR-FEL irradiation tuned to 6 μm that corresponds to carbonyl stretching vibrational mode of amide bonds (amide I). This indicates that the aggregate of HEWL was converted to the native state by the irradiation. On the other hand, synchrotron-radiation vacuum-ultraviolet circular-dichroism spectroscopy showed that protein conformation of the native HEWL, which was rich in α-helix, was little changed after the MIR-FEL irradiation under the same condition with the case of the aggregate of HEWL. Furthermore, the enzymatic hydrolysis activity of the native HEWL against bacterial glycan was not remarkably decreased by the irradiation. Therefore, it can be estimated that the native structure of HEWL is little damaged although the aggregate state can be easily dissociated by the resonant excitation at amide bonds.
关键词： Vacuum-ultraviolet circular-dichroism spectroscopy,Mid-infrared free-electron laser,Protein aggregate,Terahertz-time domain spectroscopy
更新于2025-09-19 17:13:59
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Fabrication of Er:Y2O3 transparent ceramics for 2.7?μm mid-infrared solid-state lasers
摘要： Laser grade 7 at.% Er:Y2O3 transparent ceramics with submicron grain size were fabricated by using one-step vacuum sintering followed by hot isostatic pressing (HIPing) technique. Through studying the sintering trajectory of Er:Y2O3 ceramics, the sintering temperature zone where sufficient relative density (> 96%), no pore-boundary separation, and sub-micron grain size (< 1 μm) ceramic samples could be identified. The samples pre-sintered in this zone were readily densified by HIPing. To maximum the densification and achieve high transparency, it is critical to suppress the final-stage grain growth. After HIPing at 1520 °C, the Er:Y2O3 ceramics were fully densified without further grain growth, and exhibited in-line transmission of about 81.6% at 2000 nm. Continuous wave (CW) room temperature laser operation of the Er:Y2O3 transparent ceramic at 2.7 μm was demonstrated.
关键词： Transparent ceramics,Microstructure,Mid-infrared,Solid-state lasers
更新于2025-09-19 17:13:59
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Modeling of optical signal processing based on injection-locked broadband quantum cascade lasers
摘要： An all-optical signal processing approach has been presented which relies on gain competition between interconnected wavelengths in a broadband QCL. It has been shown that optical injection-locking, as the physical mechanism which modifies the inter-coupling between widely separated wavelengths, induces spectral reshaping through suppressing or raising the output intensity at intended wavelengths. Our developed model which is based on an experimental demonstration of an ultra-broadband QCL reveals a correlation between the intensity and modulation response of the injection-locked wavelengths. Also, it has been shown that logic operations and extremely wideband wavelength conversion between the mid and far-IR spectral regions of the laser can be accomplished.
关键词： Broadband cascade lasers,mid-infrared signal processing potential,Quantum cascade lasers
更新于2025-09-19 17:13:59
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Graphene-Coated Nanowire Waveguides and Their Applications
摘要： In recent years, graphene‐coated nanowires (GCNWs) have attracted considerable research interest due to the unprecedented optical properties of graphene in terahertz (THz) and mid‐infrared bands. Graphene plasmons in GCNWs have become an attractive platform for nanoscale applications in subwavelength waveguides, polarizers, modulators, nonlinear devices, etc. Here, we provide a comprehensive overview of the surface conductivity of graphene, GCNW‐based plasmon waveguides, and applications of GCNWs in optical devices, nonlinear optics, and other intriguing fields. In terms of nonlinear optical properties, the focus is on saturable absorption. We also discuss some limitations of the GCNWs. It is believed that the research of GCNWs in the field of nanophotonics will continue to deepen, thus laying a solid foundation for its practical application.
关键词： graphene plasmons,mid‐infrared waves,graphene‐coated nanowires,waveguide
更新于2025-09-19 17:13:59
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Numerical and Theoretical Study of Tunable Plasmonically Induced Transparency Effect Based on Brighta??Dark Mode Coupling in Graphene Metasurface
摘要： In this paper, we numerically and theoretically study the tunable plasmonically induced transparency (PIT) effect based on the graphene metasurface structure consisting of a graphene cut wire (CW) resonator and double split-ring resonators (SRRs) in the middle infrared region (MIR). Both the theoretical calculations according to the coupled harmonic oscillator model and simulation results indicate that the realization of the PIT effect significantly depends on the coupling distance and the coupling strength between the CW resonator and SRRs. In addition, the geometrical parameters of the CW resonator and the number of the graphene layers can alter the optical response of the graphene structure. Particularly, compared with the metal-based metamaterial, the PIT effect realized in the proposed metasurface can be flexibly modulated without adding other actively controlled materials and reconstructing the structure by taking advantage of the tunable complex surface conductivity of the graphene. These results could find significant applications in ultrafast variable optical attenuators, sensors and slow light devices.
关键词： plasmonically induced transparency effect,metasurface,mid-infrared region,graphene split-ring resonators,graphene cut wire resonator
更新于2025-09-19 17:13:59