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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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Tunable infrared asymmetric light transmission and absorption via graphene-hBN metamaterials
摘要： We theoretically prove in this paper that using planar multilayer graphene-hexagonal boron nitride (hBN) metamaterials (GhMMs) can yield ultrabroadband and high-contrast asymmetric transmission (AT) and asymmetric absorption (AA) of light. The AA and AT features are obtained in the far-infrared (FIR) and mid-infrared (MIR) regions for normally incident light with transverse magnetic polarization. Here, the GhMMs are integrated with two asymmetric gratings of Ge and are composed of alternating multilayers of graphene (11 multi-layers) and hBN layers (10 layers). Moreover, the total subwavelength thickness of the hybrid structures is about 3 μm, being less than half of the free-space wavelength up to nearly 50 THz. This approach—which is similar to the one introduced by Xu and Lezec [Nat. Commun. 5, 4141 (2014)] for a passive hyperbolic metamaterial operating in the visible range—is based on the excitation of high-β modes of the GhMM with di?erent transmission characteristics. In addition to being ultrabroadband and high-contrast, AT and AA features of the proposed GhMMs can be actively tuned by varying the chemical potential of graphene. Furthermore, it is shown that an on-o? switching of AT factor at FIR and selective tunability at MIR frequencies can be obtained via varying μ. Due to its subwavelength and planar con?guration and active operation, these multilayer graphene-hBN metamaterials with AT and AA characteristics hold promise for integration with compact optical systems operating in the MIR and FIR ranges and are suitable for applications such as optical diodes, sensors, and thermal emitters.
关键词： asymmetric absorption,asymmetric transmission,mid-infrared,graphene-hBN metamaterials,tunable optical properties,far-infrared
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Coupled-Resonator-Induced-Transparency on Germanium-on-Insulator Mid-Infrared Platform
摘要： We demonstrate the operation of a thermally tunable coupled-resonator-induced transparency system on a germanium-on-insulator photonic platform working at a mid-infrared wavelength of approximately 1.95 μm. A maximum coupling rate of 1.25 GHz is realized between the two evanescently coupled microring resonators.
关键词： Thermo-optic tuning,Mid-infrared,Microring resonators,Germanium-on-insulator
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Molecular Fingerprint Sensing using Ge-on-Si Waveguides
摘要： Germanium-on-silicon, mid-infrared waveguides are used to demonstrate molecular fingerprint sensing of poly(methyl methacrylate) between 7.5 and 10 μm wavelength. The results are compared to Fourier transform infrared spectroscopy measurements, highlighting the potential of the platform for the identification of analytes.
关键词： sensing,Germanium,waveguides,molecular fingerprint,mid-infrared
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Mid-Infrared Silicon Waveguide-Based Bolometer
摘要： We demonstrate the ?rst waveguide-based bolometers on Silicon-on-Insulator (SOI) platform for mid-infrared (MIR) wavelengths, which use plasmonic antennas as absorbing elements. The bolometer achieves a sensitivity of 0.80 % change in resistance per milliwatt of input power at the 3.8 μm wavelength.
关键词： bolometer,silicon photonics,mid-infrared,optical antenna
更新于2025-09-16 10:30:52
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Investigation of Chaotic and Spiking Dynamics in Mid-Infrared Quantum Cascade Lasers Operating Continuous-Waves and Under Current Modulation
摘要： This study investigates chaotic and spiking dynamics of mid-infrared quantum cascade lasers operating under external optical feedback and emitting at 5.5 μm and 9 μm. In order to deepen the understanding, the route to chaos is experimentally studied in the case of continuous-wave and current modulation operation. The non-linear dynamics are analyzed with bifurcation diagrams. While for quasi-continuous wave operation, chaos is found to be more complex, pure continuous wave pumping always leads to the generation of a regular spiking induced low-frequency ?uctuations dynamics. In the latter, results show that by combining external optical feedback with periodic forcing and further induced current modulation allows a better control of the chaotic dropouts. This work provides a novel insight into the development of future secure free-space communications based on quantum cascade lasers or unpredictable optical countermeasure systems operating within the two transparency atmospheric windows hence between 3 μm–5 μm and 8.5 μm–11 μm.
关键词： entrainment phenomenon,quantum cascade laser,secure communications,external optical feedback,mid-infrared photonics,Nonlinear dynamics
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - <sup>15</sup> NH <sub/>3</sub> terahertz gas laser pumped by a mid-infrared quantum-cascade laser
摘要： We present an optically pumped terahertz gas laser, which is based on a distributed-feedback mid-infrared quantum-cascade laser as a pump source, a standing wave resonator, and 15NH3 as a gain medium.
关键词： optical pumping,15NH3,terahertz gas laser,mid-infrared,quantum-cascade laser
更新于2025-09-16 10:30:52
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Enhancement mechanisms of Tm3+-codoping on 2?μm emission in Ho3+ doped fluoroindate glasses under 888?nm laser excitation
摘要： Ho3+ doped and Ho3+/Tm3+ co-doped fluoroindate glass samples were prepared and their emission properties were compared. Under 888 nm laser excitation, the emission at 2 μm of Ho3+ ions with co-doping 2 mol% Tm3+ ions had a 2.9-fold improvement compared with that of Ho3+ doped. The absorption and emission spectra, and energy level lifetime of Ho3+/Tm3+ co-doped glass samples were measured to analyze the energy transfer processes and enhancement mechanisms. The luminescence intensity at 2 μm can be greatly increased due to the bidirectional energy transfer between Tm3+ and Ho3+ ions.
关键词： Luminescence,Mid-infrared,Ho3+/Tm3+ co-doped,Fluoroindate glass
更新于2025-09-16 10:30:52
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Nanoantenna Structure with Mid-Infrared Plasmonic Niobium-Doped Titanium Oxide
摘要： Among conductive oxide materials, niobium doped titanium dioxide has recently emerged as a stimulating and promising contestant for numerous applications. With carrier concentration tunability, high thermal stability, mechanical and environmental robustness, this is a material-of-choice for infrared plasmonics, which can substitute indium tin oxide (ITO). In this report, to illustrate great advantages of this material, we describe successful fabrication and characterization of niobium doped titanium oxide nanoantenna arrays aiming at surface-enhanced infrared absorption spectroscopy. The niobium doped titanium oxide film was deposited with co-sputtering method. Then the nanopatterned arrays were prepared by electron beam lithography combined with plasma etching and oxygen plasma ashing processes. The relative transmittance of the nanostrip and nanodisk antenna arrays was evaluated with Fourier transform infrared spectroscopy. Polarization dependence of surface plasmon resonances on incident light was examined confirming good agreements with calculations. Simulated spectra also present red-shift as length, width or diameter of the nanostructures increase, as predicted by classical antenna theory.
关键词： niobium-doped titanium oxide,mid-infrared plasmonics,nanoantenna
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) - Optical Frequency Comb Generation using Quantum Cascade Lasers Subject to Optical Injection
摘要： Mid-infrared optical frequency combs (OFCs) are of prime importance for spectroscopy detection of many gas molecules, such as carbon dioxide and methane because of their strong absorption lines in the mid-infrared regime. Quantum cascade laser (QCL) is one of the dominate mid-infrared laser sources, however it is hard to obtain OFCs using the common mode locking technique due to the ultrashort carrier lifetime. On the other hand, QCLs have successfully produced OFCs based on the four-wave mixing effect, the difference-frequency process, and the Kerr nonlinearity. This work proposes to use the period-one (P1) dynamics of QCLs subject to optical injection for OFC generation.
关键词： Optical Frequency Comb,Spectroscopy,Mid-infrared,Quantum Cascade Laser,Optical Injection
更新于2025-09-16 10:30:52