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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) - Sub-terahertz Quantum-cascade Laser Source based on Difference-frequency Generation
摘要： Authors report a sub-terahertz monolithic semiconductor source based on a high power, long-wavelength quantum cascade laser. In order to obtain higher nonlinear susceptibility in the sub-terahertz frequency region, we design long wavelength dual-upper-state active region in which transition dipole moments are substantially increased. A fabricated device with distributed feedback grating produces nearly watt-level infrared output power, and as a result, it exhibits a peak output power of 18.5 μW at room temperature, around a frequency of ~700 GHz. Besides, the device produces an output power of 103 μW at 110 K.
关键词： dual-upper-state active region,monolithic semiconductor source,difference-frequency generation,sub-terahertz,quantum-cascade laser
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) - High power THz quantum cascade laser and its demonstration in high resolution holographic imaging
摘要： Fabrication of high power terahertz quantum cascade laser (THz QCL) based upon the resonant-phonon active region design and semi-insulating surface-plasmon waveguide with frequency at 4.4 THz and its demonstration in digital holographic imaging are presented. The maximum peak output power is 95mW at 10K in pulsed mode. The maximum working temperature is 80 K. Interestingly, by changing the injection current, the transverse mode of the laser can be switched between TM00 mode and TM01 mode. With such THz QCL as the light source, the lateral resolution of a home-built digital holographic imaging system can reach 80μm.
关键词： holographic imaging,high power,resonant-phonon,semi-insulating surface-plasmon waveguide,THz quantum cascade laser
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
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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) - Probing Molecules Next to Surfaces
摘要： Selective reflection spectroscopy at normal incidence provides signals with sub-Doppler resolution, linear with optical intensity. Frequency modulated (FM) selective reflection probes atomic vapours at distances comparable to the excitation wavelength (~λ/2π) and is used extensively to probe the Casimir-Polder interactions between an excited state atom and a macroscopic surface. Extending selective reflection spectroscopy to molecular gases allows probing a thin layer of molecular gas next to a surface. This is a very attractive prospect that allows envisaging high-resolution molecular spectroscopy and molecular frequency references in a compact and miniaturised apparatus, such as a thin cell [1] or a photonic crystal [2]. Additionally, it paves the way for spectroscopic probing of the Casimir-Polder interaction with molecules. The molecule-surface interaction has been the object of extensive theoretical investigations, focusing on the effects of molecular orientation and chirality. However, experimental tests are few and comparison with theoretical predictions has been challenging [3]. Here, we present selective reflection measurements on polyatomic molecules in gaseous form. We probe rovibrational molecular transitions of NH3 and SF6 using a Quantum Cascade Laser (QCL) at ~10.6μm. Reflection spectroscopy is performed in a vacuum chamber with transparent ZnSe windows. In a separate chamber, we perform simultaneous saturated absorption measurements, to get molecular frequency references in the volume. We also use an auxiliary set-up to lock the QCL laser, either on the derivative (after FM demodulation) of a Doppler linear absorption, or on the wings of the NH3 linear absorption (direct signal). This allows us to eliminate a frequency drift of the QCL source due to temperature fluctuations. By tuning the molecular pressure and therefore the absorption profile, the latter method (lock on the direct signal) allows stable frequency scanning for hundreds of MHz. A system of electronic valves allows us to empty and refill the chamber with molecules within tens of seconds. Detecting the difference between signals, as well as using multiple vibrating mirrors in our set-up, eliminates to about 0.1ppm an interferometric parasitic background, typical in infrared spectroscopy. Fig.1 shows our experimental results obtained for the isolated saP(1) transition of NH3 (Fig. 1a) and a multitude of transitions of SF6, mostly unidentified in molecular databases (Fig. 1b). Linear selective reflection allows us to pinpoint these transitions and easily determine their relative amplitude. At sufficiently low molecular pressure, the frequency resolution of our measurements is limited to ~0.5MHz essentially by laser linewidth. This allows partially resolving the hyperfine structure of NH3. The dotted curves represent theoretical predictions of selective reflection spectra, with transition amplitude adjustments, accounting for FM and laser linewidth. We are working on the fabrication of thin cells using ZnSe windows for rovibrational transmission spectroscopy in the mid-infrared, as well as glass windows, for probing C2H2 at telecommunication wavelengths. Due to the Dicke narrowing effect, thin cells are a step towards compact high-resolution frequency references. Furthermore, achieving, nanometric molecular confinement, defined by cell thickness, instead of wavelength (λ/2π for selective reflection, here ~1.5μm) will allow us to measure the Casimir-Polder interaction with molecules and to study the thermal coupling and energy transfer between rovibrational molecular transitions and surface polaritons [4].
关键词： SF6,Casimir-Polder interactions,molecular gases,Quantum Cascade Laser,NH3,Selective reflection spectroscopy
更新于2025-09-16 10:30:52
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Influence of exciton energy on intersubband transition of chirped superlattice GaAs/AlGaAs quantum cascade laser
摘要： The influence of exciton energy on intersubband transition was simulated for a chirped supperlattice quantum cascade laser of GaAs/AlxGa1-xAs. Exciton energy was modelled as a function of QW width for alloys of various percentages of constituent elements. The results showed that the exciton energy decreased proportionally with increasing QW width. Models were also generated to study exciton energy as a function of the percent alloy contents of AlxGa1-xAs barriers for QWs of various widths. Exciton energy showed characteristics of higher discrete energy when QW width was narrower. Transition energy was also simulated from 1e and 2e to the 1s exciton state as functions of applied electric field at various QW widths. Our simulation results showed that the transition energy from 2e to the 1s exciton state increased proportionally to the increasing strength of the electric field. This transition energy was indicative of THz range radiation.
关键词： percent alloy contents,chirped superlattice quantum cascade laser,aluminum arsenide monolayer,THz radiation,transition energy
更新于2025-09-16 10:30:52
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Enhanced RDX Detection Studies on Various Types of Substrates via Tunable Quantum Cascade Laser Spectrometer Coupled with Grazing Angle Probe
摘要： Owing to scientific advances in the field of materials sciences and engineering, researchers have developed new energy sources used for spectroscopic applications and measurements of properties resulting from the interaction of matter and electromagnetic radiation in the mid-infrared (MIR) region. MIR lasers, such as quantum cascade lasers (QCLs), used for spectroscopy have quickly found numerous applications in a wide cadre of IR techniques. This provides the opportunity to study properties of highly energetic materials (HEM), among many other applications. MIR laser spectroscopy based detection experiments of HEMs were carried out using a QCL optically coupled to compact grazing angle probe mount (QCL-GAP) enabling reflection-absorption infrared spectroscopy (RAIRS) measurements of thin films of HEMs. A saturated solution of RDX in acetone was prepared, and aliquots of subsequent dilutions of the stock solutions were transferred to test surfaces for QCL-GAP back-reflectance measurements. RDX reflectance signals were monitored as function as the decreasing surface concentration until the signal/noise was ~ 3. Stainless steel (SS) plates were used as reflective substrates, and anodized aluminum (AN-Al), cardboard, and Teflon were used as non-reflective (matte) substrates. Using generated calibration curves a low limit of detection (LOD) of 1.7 ng/cm2 for RDX/SS and 95 μg/cm2 for RDX/AN-Al were found. Based on the area of laser spot (0.3 cm2) we conclude the minimum masses detected were 490 pg (RDX/SS) and 28 μg (RDX/AN-Al).
关键词： Quantum Cascade Laser,RDX detection,Grazing Angle Probe,Highly Energetic Materials,Mid-Infrared Spectroscopy
更新于2025-09-16 10:30:52
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Quasi-statischer MOEMS-Gitterscanner zum spektralen Durchstimmen eines MIR-Quantenkaskadenlasers
摘要： Broadband tuning of MIR-infrared radiation from 3 to 10 μm (1000 to 3200 wavenumbers) is a very promising way for spectroscopic study of gaseous, liquid, or solid species or intermixtures. We report a new quasi-static micro-optical-electrical-mechanic (MOEMS) grating for spectral tuning of an IR light source based on a quantum cascade laser. This concept unites the advantages of broadband sources with the advantages of coherent laser sources in a miniaturized setup. In contrary to resonant MOEMS device, the quasi-static driving principle allows the scanning with arbitrary trajectories and velocity and thus with potential higher spectral resolution. To stabilize the trajectory the MOEMS device is controlled by integrated position sensors. We report the dynamical characteristics of MOEMS micro-mirror with integrated diffraction grating and experimental results of the tuning of a QCL in the wavelength range from 4150 to 4600 nm.
关键词： quantum cascade laser,IR spectroscopy,MOEMS scanner,diffraction grating,micro-mirror
更新于2025-09-16 10:30:52
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Identification of Chemical Compounds by the Reflected Spectra in the Range of 5.3–12.8 μm Using a Tunable Quantum Cascade Laser
摘要： We have considered the technique and experimental laboratory setup that allow the recording of the specular and diffuse reflectance spectra of the infrared radiation of substances in solid and liquid aggregate states on various surfaces. A quantum cascade laser, tunable in the wavelength range of 5.3–12.8 μ m with a spectral resolution of 2 cm–1 and an average power of 15 mW, was used as a probing radiation source. The experimental setup made it possible to record the spectra of the diffusely reflected radiation of the substances. Methods for the identification of substances based on the scattered radiation spectra are proposed. It is shown that the use of the Kramers–Kronig integral transform increases the degree of selectivity of the spectra and, as a consequence, the reliability of identification.
关键词： quantum cascade laser,infrared spectroscopy,Kramers–Kronig relations,identification
更新于2025-09-16 10:30:52
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MOVPE-Grown Quantum Cascade Laser Structures Studied by Kelvin Probe Force Microscopy
摘要： A technique for direct study of the distribution of the applied voltage within a quantum cascade laser (QCL) has been developed. The detailed pro?le of the potential in the laser claddings and laser core region has been obtained by gradient scanning Kelvin probe force microscopy (KPFM) across the cleaved facets for two mid-infrared quantum cascade laser structures. An InGaAs/InAlAs quantum cascade device with InP claddings demonstrates a linear potential distribution across the laser core region with constant voltage drop across the doped claddings. By contrast, a GaAs/AlGaAs device with AlInP claddings has very uneven potential distribution with more than half of the voltage falling across the claddings and interfaces around the laser core, greatly increasing the overall voltage value necessary to achieve the lasing threshold. Thus, KPFM can be used to highlight design and fabrication ?aws of QCLs.
关键词： MOVPE,quantum cascade laser,Kelvin probe force microscopy
更新于2025-09-16 10:30:52
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Numerical study of Riskena??Nummedala??Grahama??Haken instability in mid-infrared Fabrya??P??rot quantum cascade lasers
摘要： We review our recent theoretical studies on multimode instabilities in Fabry–Pérot cavity mid-infrared quantum cascade lasers (QCLs) caused by parametric excitation of Rabi flopping oscillations. Numerical simulations are based on the semiclassical traveling wave Maxwell–Bloch equations. QCLs with a few mm cavity without an absorber exhibit intermittent RNGH self-pulsations, while regular self-pulsations are possible in short-cavity QCLs, with the cavity length of 100 μm or smaller. However, the second threshold in short-cavity QCLs is significantly increased compared to the values for a few mm long devices. We provide here a new insight on RNGH instability via bifurcation analysis of the output waveform and studies of the recurrence period density entropy. We propose an interpretation of the broadening/narrowing of the optical spectrum of a QCL i.e. switching the RNGH instability on and off observed in experiment.
关键词： Quantum cascade laser,RNGH instability,Self-pulsations,Bifurcation diagram,Spatial hole burning
更新于2025-09-16 10:30:52