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Spectral Shift of Quantum-Cascade Laser Emission under the Action of Control Voltage
摘要： Spectral redistribution of the intensity of short- and long-wavelength emission components within gain bandwidth of a 7- to 8-μ m quantum-cascade laser under the action of control voltage is demonstrated. As the voltage was increased from 10.5 to 18.2 V, the wavelength of maximum laser emission intensity shifted by approximately 200 nm. The maximum bandwidth of laser gain was about 300 nm (at a temperature of 80 K). The quantum-cascade laser heterostructure was grown by molecular beam epitaxy. The laser active region design was based on double-phonon depopulation of the lower level as implemented on In0.53Ga0.47As/In0.52Al0.48As heteropair of solid alloys lattice-matched with an InP substrate.
关键词： indium phosphide,quantum-cascade lasers,superlattices,epitaxy
更新于2025-09-16 10:30:52
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Optical spectroscopy studies of atom intermixing in the core versus growth temperature of the claddings in MOCVD-grown quantum cascade lasers
摘要： Here we present optical spectroscopy studies to examine structural and optical properties of active region of quantum cascade lasers grown fully by MOCVD technique. The active part is InGaAs/AlInAs based multilayer structure nominally lattice matched to InP substrate. In this communication we study a set of structures with different growth temperature of the cladding layers and its influence on the properties of active core. The x-ray spectroscopy (XRD) allowed to determine the widths of constituent layers and compare obtained values with nominal ones. Fourier-transformed photoluminescence (FTPL) and photoreflectance (PR) measurements provided high signal to noise spectra, proving good optical and structural properties of investigated samples. A model of atoms interdiffusion processes was presented to explain observed small energy shifts of the transitions energies within the investigated multilayer structures.
关键词： MOCVD,optical spectroscopy,semiconductors,mid infrared,atoms interdiffusion,quantum cascade lasers
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - To the Treatment of Anterior Uveitis
摘要： We investigate terahertz quantum cascade lasers with a dense array of active micropillars forming the gain medium. Depending on the size of these pillars relative to the emission wavelength different optical regimes are identified. For pillar dimensions on the order of the emission wavelength, a photonic crystal resonator is created. Single mode emission is observed at high symmetry points of the photonic band structure. The selection mechanism of the favored laser mode is studied by analyzing the gain enhancement effect for eigenmodes with a low group velocity and a large mode confinement of the electric field energy in the micropillars. Subwavelength micropillar arrays constitute a photonic metamaterial, which can be described using an effective medium approximation. Similar to a bulk laser ridge, the array forms a Fabry–Pérot resonator that is defined by the boundaries of the array. From the longitudinal mode spacing, we derive an effective group index of the pillar medium. Limitations in terms of minimum filling factors and waveguide losses for the realization of subwavelength micropillar and nanowire array terahertz quantum cascade lasers are investigated.
关键词： Photonic crystals,terahertz,optical waveguides,optical metamaterials,quantum cascade lasers
更新于2025-09-16 10:30:52
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Electrical tuning of a terahertz quantum cascade laser based on detuned intersubband absorption
摘要： A mechanism to electrically tune the frequency of terahertz quantum cascade lasers (QCLs) is developed that allows for tuning, while the QCL is operated close to its peak bias and temperature. Two optically coupled but electrically isolated cavities are used in which the bias of a control cavity tunes the resonant-mode of the coupled QCL cavity independent of the QCL’s operating bias. Approximately 4 GHz electrical tuning is realized for a 3:6 THz distributed-feedback QCL operating in pulsed mode at 58 K in a Stirling cooler. The single-mode QCL emits near-constant peak-power in the range of 5 (cid:2) 5:3 mW through the tuning range and radiates in a narrow single-lobed beam with a far-?eld divergence of (cid:3)4(cid:4) (cid:5) 11(cid:4). The superlattice structure of the QCL is designed to implement a low-voltage intersubband absorption transition that is detuned from that of its gain transition, the strength of which could be controlled sensitively with applied voltage utilizing resonant-tunneling injection of electrons in the absorption subband. The tuning is realized by the application of small bias voltages ((cid:3)6 (cid:2) 7 V) and requires a narrow bias range ((cid:3)1 V, (cid:3)40 A=cm2) to traverse across the entire tuning range, and the method should be generally applicable to all intersubband lasers including mid-infrared QCLs.
关键词： detuned absorption,cavity pulling,terahertz quantum cascade lasers,electrical tuning,intersubband absorption
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) - Extended-Cavity-Quantum-Cascade-Laser-Voltage Intracavity Sensing and Application to Atmospheric Gas Detection
摘要： Laser spectrometers based on Quantum Cascade Lasers (QCL) provide good results for gas sensing in terms of sensibility and selectivity thanks to the characteristics of these sources. Distributed feedback (DFB) configuration provides narrow linewidth that enhances selectivity and their emission in the mid-IR enables to reach the fundamental absorption bands of molecules. The main limitation of these sources is their narrow tuning range (~ 10 cm-1) that prevents from monitoring complex species with broad absorption spectra or realizing multi-gas sensing. To obtain a broader tuning range, one solution consists of QCL DFB array with an arrayed waveguide grating to perform multi-species spectroscopy [1]. A more common technique is to implement the laser in an external cavity system. In GSMA, a commercial Extended-Cavity Quantum Cascade Laser emitting at 10.5 μm has been used to demonstrate photoacoustic gas sensing of heavy molecules such as butane [2] and a lab-made EC-QCL emitting at 7.5 μm was developed for detection of acetone and POCl3 in gas phase [3]. Moreover, the use of an external cavity allows the possibility to perform Intra-Cavity Laser Absorption Spectroscopy (ICLAS). In this method the sample is placed within the laser resonator. Absorption lines of the sample imprint signatures on the spectrum because they influence it during many round trips. The cavity output light is detected to perform spectroscopy. The used QCL developed by mirSense is operated in cw operation at room temperature and emits from 7.4 to 7.8 μm. A technique using the QCL compliance voltage [4] called EVIS (EC-QCL Voltage Intracavity Sensing) is used to retrieve the spectrum of the gas inside the cavity. This way no detector outside the cavity is needed. With gas inside the cavity, losses rise implies a variation of intracavity intensity thus a variation of laser voltage. The large wavenumber sweeping is performed through the grating rotation and the variation of QCL current supply permits to obtain a small wavelength variation. In order to suppress the QCL mode hops influence, a current ramp is applied so that the small wavelength total variation is equal to 1 QCL mod hop. Then QCL voltage is recorded during the current ramp, for all grating positions, and a numerical treatment is performed to improve the signal. Fig. 1 presents a result of this measurement (on the left) compared with the absorption coefficient calculated from the HITRAN database [www.hitran.org] (on the right). This measurement corresponds to a cavity filled with 0.3% of CH4 in air (containing water vapor) at atmospheric pressure. This preliminary result shows a good agreement between the voltage difference and the calculated absorption coefficient. The resolution is estimated to approx. 0.1 cm-1.
关键词： Quantum Cascade Lasers,gas sensing,ICLAS,Intra-Cavity Laser Absorption Spectroscopy,EVIS,EC-QCL Voltage Intracavity Sensing,QCL
更新于2025-09-12 10:27:22
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Multiscale Electrothermal Simulation of Quantum Cascade Laser Operation
摘要： Quantum cascade lasers (QCLs) are high-power coherent light sources in the midinfrared and terahertz parts of the electromagnetic spectrum. They are systems in which the electronic and lattice systems are far from equilibrium, strongly coupled to one another, and the problem bridges disparate spatial scales. We present our ongoing work on the far-from-equilibrium transport of charge and heat in QCLs.
关键词： Quantum cascade lasers,far-from-equilibrium,electrothermal simulation,multiphysics,multiscale
更新于2025-09-12 10:27:22
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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) - A broadband polarization-rotating antipodal Vivaldi antenna for improved far-field properties of terahertz quantum cascade lasers
摘要： Double metal waveguide based terahertz quantum cascade lasers (QCLs) have excellent properties in terms of compactness, large bandwidth and low waveguide dispersion. However, as they confine the optical mode to subwavelength dimensions, their far-field is highly divergent. Our antipodal Vivaldi antenna is designed to produce a single-lobed far-field pattern with a beam width of less than 20°, spanning over two octaves in frequency (1.5-4.5 THz). Far-field measurements agree well with numerical simulations.
关键词： Vivaldi antenna,quantum cascade lasers,far-field,terahertz,broadband
更新于2025-09-12 10:27:22
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Low Power Consumption Distributed-Feedback Quantum Cascade Lasers Operating in Continuous-Wave Mode above 90°C at λ ～ 7.2 μm
摘要： We report on the design and fabrication of ?? ～ 7.2 ??m distributed feedback quantum cascade lasers for very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90°C. For a 2-mm-long and 10-??m-wide laser coated with high-reflectivity on the rear facet, more than 170 mW of output power is obtained at 20°C with a threshold power consumption of 2.4 W, corresponding to 30 mW with a threshold power consumption of 3.9 W at 90°C. Robust single-mode emission with a side-mode suppression ratio above 25 dB is continuously tunable by the heat sink temperature or injection current.
关键词： high temperature operation,Distributed feedback quantum cascade lasers,low power consumption,continuous-wave mode
更新于2025-09-12 10:27:22
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Mid-infrared laser absorption spectroscopy of the Ne–NO(X <sup>2</sup> Π) complex
摘要： The rovibrational spectrum of the Ne–NO(X2Π) open-shell complex has been measured in the 5.3 μm region using distributed feed-back quantum cascade lasers to probe the direct absorption in a slit-jet supersonic expansion. Three P-subbands (P′ ← P′′: 1/2 ← 1/2, 3/2 ← 1/2, and 5/2 ← 3/2) were observed, where P is the projection of the angular momentum J along the inertial a-axis of the complex. The hyperfine structure due to the nuclei spin of 14N (I = 1) was partially resolved in the P′ ← P′′: 1/2 ← 1/2 and 3/2 ← 1/2 subbands. The observed mid-infrared spectrum of Ne–NO (X2Π) together with the previously reported microwave spectrum was analyzed using a modified semirigid asymmetric rotor Hamiltonian for a planar open-shell complex. The band origin is located at 1876.0606(97) cm?1, which is blue-shifted from that of the NO monomer by only 0.0888 cm?1. The complex shows strong structural relaxation upon excitation of the overall rotation and the internal rotation of the NO subunit.
关键词： mid-infrared,hyperfine structure,rovibrational spectrum,Ne–NO,quantum cascade lasers
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) - Optoelectronic Devices Based on ZnO/ZnMgO
摘要： The terahertz (THz, 30 μm – 300 μm) spectral region covers various relevant and significant real-world applications like spectral imaging [1], medical diagnostics [2] and trace gas spectroscopy [3]. But due to the lack of high-performance laser sources, it is also referred to as the “THz-gap” in the electromagnetic spectrum. To close this gap, room temperature THz emitting laser sources are needed. Up to now, GaAs-based quantum cascade lasers (QCLs) [4] are the most promising candidates to fulfil this task but they lack significant improvements within recent years concerning their maximum operating temperature and are still limited to operation at cryogenic temperatures around 200K. They are fundamentally limited by the parasitic, non-optical LO-phonon transitions (36meV in GaAs), being on the same order as the thermal energy at room temperature (kT = 26meV). Therefore, other semiconductor materials might solve this problem, including new material systems like ZnO or GaN with their larger LO-phonon energy (ELO,ZnO = 72meV, ELO,GaN = 91meV). While GaN has recently already been investigated in detail without final breakthrough concerning GaN-based QC devices, ZnO is new to this field of application. Consequently, the design and fabrication of ZnO-based QC structures has to be mastered, including a high quality epitaxial growth and well-controlled fabrication processing.
关键词： ZnMgO,quantum cascade lasers,ZnO,molecular beam epitaxy,terahertz
更新于2025-09-12 10:27:22