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High-Performance Growth of Terahertz Quantum Cascade Laser Structures by Solid Source MBE
摘要： High performance growth of terahertz quantum cascade lasers (THz QCLs) based on hybrid bound-to-continuum transition and resonant phonon extraction is presented by solid source molecular beam epitaxy. The corresponding accurate control of layer thickness and alloy composition during growth, with precise calibration of the growth rate of Ga and Al by reflection high energy electron diffractometry and high resolution XRD techniques are studied in detail. By utilizing surface plasmon ridge waveguide device structures, the THz QCLs lasing at 3.3 THz with maximum powers of 426 mW at 10 K and 213 mW at 80 K are realized in pulsed mode and the maximum lasing temperature achieves 110 K.
关键词： quantum cascade laser,superlattice,molecular beam epitaxy,terahertz,heterostructure
更新于2025-09-16 10:30:52
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Density matrix superoperator for periodic quantum systems and its application to quantum cascade laser structures
摘要： In this work we present a generalization of the Liouvillian superoperator for periodic quantum systems that can be formulated through partitioned Hamiltonians. We formulate a compact algebraic form of the superoperator that allows efficient numerical implementation along with the possibility of further generalization and the inclusion of the system’s boundary effects (i.e. device contacts). We apply this formalism to Quantum Cascade Laser structure where we compare the second nearest and the nearest on approximation, and present the laser dynamics that is independent from the number of states considered.
关键词： Liouvillian superoperator,periodic quantum systems,density matrix,Khatri-Rao product,Quantum Cascade Laser
更新于2025-09-12 10:27:22
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High Power Quantum Cascade Laser at λ 5.1 <i>μ</i> m Based on Low Strain Compensation Design
摘要： We demonstrate the development of a high performance quantum cascade laser at (cid:2) ～ 5(cid:3)1 (cid:4)m with low strain-balanced structure using a double-phonon resonant design approach. The wafer was grown by solid source molecular beam epitaxy and fabricated with buried heterostructure waveguides. A high output power up to 1.5 W is obtained at 288 K with a high wall plug ef?ciency of 8.5% for devices with stripe dimension of 5 mm × 10 (cid:4)m. The characteristic temperatures, T 1, are 114 K and 198 K respectively.
关键词： High Power Laser,Strain-Compensation,Quantum Cascade Laser
更新于2025-09-12 10:27:22
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Widely tunable compact terahertz gas lasers
摘要： The terahertz region of the electromagnetic spectrum has been the least utilized owing to inadequacies of available sources. We introduce a compact, widely frequency-tunable, extremely bright source of terahertz radiation: a gas-phase molecular laser based on rotational population inversions optically pumped by a quantum cascade laser. By identifying the essential parameters that determine the suitability of a molecule for a terahertz laser, almost any rotational transition of almost any molecular gas can be made to lase. Nitrous oxide is used to illustrate the broad tunability over 37 lines spanning 0.251 to 0.955 terahertz, each with kilohertz linewidths. Our analysis shows that laser lines spanning more than 1 terahertz with powers greater than 1 milliwatt are possible from many molecular gases pumped by quantum cascade lasers.
关键词： gas lasers,tunable sources,molecular laser,quantum cascade laser,terahertz
更新于2025-09-12 10:27:22
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Generation of Frequency Combs by Quantum Cascade Lasers Emitting in the 8-μm Wavelength Range
摘要： We have studied the generation of frequency combs by quantum cascade lasers (QCLs) emitting in the 8-μm wavelength range. Results showed the presence of a self-pulsation regime near the lasing threshold. Further increase in the pumping current led to a sharp increase in width of the lasing spectrum, which allowed us to obtain frequency combs with a spectral width exceeding 1.5 THz. This behavior of QCLs can be explained by radiation absorption at the stripe edge that is related to the penetration of waveguide mode into unpumped regions.
关键词： quantum cascade laser,mode locking,Q-switching,frequency comb
更新于2025-09-12 10:27:22
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Nonlinear intersubband absorption coefficient in an Al xGa 1?x As/GaAs quantum cascade laser-like profile
摘要： In this work we perform a theoretical study on the nonlinear intersubband absorption response in a quantum cascade laser (QCL) pro?le-like heterostructure that consists of a triple AlxGa1?xAs/GaAs quantum well. In particular, we investigate the role of the central quantum well width, as well as the electric and magnetic ?eld e?ects, on the intersubband optical properties of the system. Results on the electronic structure arise within the framework of the e?ective mass, and parabolic band approximations. The calculation also takes into account the e?ective mass mismatch in the kinetic energy and magnetic potential energy terms, in order to investigate the importance of the position dependence of this parameter. The conduction band o?set ratio was determined using the model solid theory, considering strain e?ects. The expression from which we calculate the nonlinear optical response comes from the third-order dielectric susceptibility derived within the compact density matrix formalism. In general we have obtained that, as a function of the central well width and the applied magnetic ?eld strength, the light absorption coe?cient can exhibit red- and blue-shifts. Meanwhile, in the case of the application of an electric ?eld only blue-shifts are observed. The e?ective mass mismatch is more signi?cant for small applied magnetic ?elds, due to the di?erence in the resonant peak found in the absorption coe?cient. In all cases it is found that the third-order correction is signi?cant in value.
关键词： Intersubband absorption coe?cient,E?ective mass mismatch,Quantum cascade laser
更新于2025-09-12 10:27:22
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Lasing of a Quantum-Cascade Laser with a Thin Upper Cladding
摘要： We present the results of experiments on the fabrication and study of the properties of quantum-cascade lasers of the spectral range of 7–8 μ m in the geometry of a waveguide with a thin top cladding based on indium phosphide. The heterostructure is synthesized by molecular beam epitaxy on an InP substrate with an active region based on a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid alloys. Laser emission at a wavelength of 7.8 μ m at a temperature of 300 K with a threshold current density of ~6 kA/cm2 was achieved. The values of characteristic temperatures T0 and T1 for the studied quantum-cascade lasers are of the order of 150 and 450 K, respectively. The results obtained confirm that the design of the waveguide with a thin top cladding for devices for detecting liquids, the fabrication of microfluidic devices, and photonic circuits on silicon holds promise.
关键词： quantum-cascade laser,indium phosphide,lasing,MBE
更新于2025-09-12 10:27:22
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Determining a Line Strength in the ν <sub/>3</sub> Band of the Silyl Radical Using Quantum Cascade Laser Absorption Spectroscopy
摘要： Silane (SiH4) plasmas are widely used for the deposition of hydrogenated amorphous silicon (a-Si:H) films. Nevertheless, the chemical processes governing film deposition are still incompletely understood. Moreover, there is still no general method available to determine the absolute concentration of the silyl radical (SiH3), which is the accepted chemical precursor of a-Si:H films. In this study, a 10% silane in helium RF plasma was spectroscopically investigated between 2085 and 2175 cm?1 using an external cavity quantum cascade laser (EC-QCL) based spectrometer. This led to the identification of 4 distinct species from their absorption features: SiH4, disilane (Si2H6), SiH3, and an unassigned short-lived species. Furthermore, 17 absorption features of SiH3 were identified and unambiguously assigned. Fast spectral scanning of selected absorption features belonging to the four species in a 10 Hz pulsed RF plasma enabled the measurement and interpretation of their temporal behavior in terms of plausible chemical reactions involving silicon containing species. By quantitatively measuring the decay of the SiH3 a ← a pP4 (5) transition at 2151.3207 cm?1 after the discharge was stopped, its line strength (S) was determined to be (7.5 ± 5.5) × 10?20 cm2 cm?1 mol?1.
关键词： quantum cascade laser absorption spectroscopy,hydrogenated amorphous silicon,Silane plasmas,line strength,silyl radical
更新于2025-09-12 10:27:22
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Line-defect photonic crystal terahertz quantum cascade laser
摘要： The terahertz (THz) quantum cascade laser (QCL) provides a versatile tool in a plethora of applications ranging from spectroscopy to astronomy and communications. In many of these fields, compactness, single mode frequency emission, and low threshold are highly desirable. The proposed approach, based on line defects in a photonic crystal (PhC) matrix, addresses all these features while offering unprecedented capabilities in terms of flexibility, light waveguiding, and emission directionality. Nine line-defect QCLs were realized in a triangular lattice of pillars fabricated in the laser active region (AR), centered around ～2 THz by tuning the photonic design. A maximal 36% threshold reduction was recorded for these ultraflat dispersion line-defect QCLs in comparison to standard metal-metal QCL. The mode selectivity is an intrinsic property of the chosen fabrication design and has been achieved by lithographically scaling the dimension of the defect pillars and by acting on the PhC parameters in order to match the AR emission bandwidth. The measured line-defect QCLs emitted preferentially in the single frequency mode in the propagation direction throughout the entire dynamic range. An integrated active platform with multiple directional outputs was also fabricated as proof-of-principle to demonstrate the potential of this approach. The presented results pave the way for integrated circuitry operating in the THz regime and for fundamental studies on microcavity lasers.
关键词： photonic crystal,line-defect,quantum cascade laser,low threshold,terahertz,single mode emission
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) - Dual-Lasing Channel of a High-Temperature Terahertz Quantum Cascade Laser
摘要： Terahertz (THz) quantum cascade lasers (QCLs) are powerful coherent light sources covering the frequency range from 1.2 to 5.4 THz, but still suffer from operation temperatures below 200 K. Here, we show the results of a barrier height study for a three-well active region based on GaAs/AlxGa1-xAs heterostructure with changing Al concentrations from x = 12% to 24%. Higher barriers reduce the thermal leakage of electrons at elevated temperatures and reduce the coupling of the electron wave functions. The calculated energy difference of these two electronic states (1.75 meV) agrees with the separation of the two regions in the measured frequency spectrum at 3.4 and 3.8 THz (ΔE = 1.65 meV) at low temperature. With this technique we expect to improve the maximum operation temperature and to optimize broadband devices which are necessary for frequency combs and mode-locked devices.
关键词： Quantum Cascade Laser,High-Temperature Operation,Dual-lasing Channel,Terahertz
更新于2025-09-12 10:27:22