Quantum cascade lasers(QCLs) have broad application potentials in infrared countermeasure system,free-space optical communication and trace gas detection.Compared with traditional Fabry-Pérot(FP) cavity and exter...Quantum cascade lasers(QCLs) have broad application potentials in infrared countermeasure system,free-space optical communication and trace gas detection.Compared with traditional Fabry-Pérot(FP) cavity and external cavity,distributed feedback quantum cascade lasers(DFB-QCLs) can obtain narrower laser linewidth and higher integration.In this paper,the structure design,numerical simulation and optimization of the Bragg grating of DFB-QCLs are carried out to obtain the transmission spectrum with central wavelength at 4.6 μm.We analyze the relationship among the structure parameters,the central wavelength shift and transmission efficiency using coupled-wave theory and finite-difference time-domain(FDTD) method.It is shown that the increase in the number of grating periods enhances the capabilities of mode selectivity,while the grating length of a single period adjustment directly determines the Bragg wavelength.Additionally,variations in etching depth and duty cycle lead to blue and red shifts in the central wavelength,respectively.Based on the numerical simulation results,the optimized design parameters for the upper buffer layer and the upper cladding grating are proposed,which gives an optional scheme for component fabrication and performance improvement in the future.展开更多
Nitric oxide(NO)is one of the most crucial products in the plasma-based nitrogen fixation process.In this work,in situ measurements were performed for quantifying the NO synthesis spatially in a warm air glow discharg...Nitric oxide(NO)is one of the most crucial products in the plasma-based nitrogen fixation process.In this work,in situ measurements were performed for quantifying the NO synthesis spatially in a warm air glow discharge,through the method of Mid-infrared quantum cascade laser absorption spectroscopy(QCL-AS).Two ro-vibrational transitions at 1900.076 cm^(-1) and 1900.517 cm^(-1) of the ground-state NO(X)were probed sensitively by the help of the wavelength modulation spectroscopy(WMS)approach to increase the signal/noise(S/N)level.The results show a decline trend of NO synthesis rate along the discharge channel from the cathode to the anode.However,from the point of energy efficiency,the cathode region is of significantly low energy efficiency of NO production.Severe disproportionality was found for the high energy consumption but low NO production in the region of cathode area,compared to that in the positive column zone.Further analysis demonstrates the high energy cost of NO production in the cathode region,is ascribed to the extremely high reduced electric field E/N therein not selectively preferable for the processes of vibrational excitation or dissociation of N_(2) and O_(2) molecules.This drags down the overall energy efficiency of NO synthesis by this typical warm air glow discharge,particularly for the ones with short electrode gaps.Limitations of further improving the energy cost of NO synthesis by variations of the discharge operation conditions,such as discharge current or airflow rate,imply other effective manners able to tune the energy delivery selectively to the NO formation process,are sorely needed.展开更多
A simulation method for the thermal analysis of InAlAs/InGaAs/InP mid-infrared quantum cascade lasers (QCLs) based on finite-element method (FEM) is presented. The thermal distribution of the QCLs on substrate-side or...A simulation method for the thermal analysis of InAlAs/InGaAs/InP mid-infrared quantum cascade lasers (QCLs) based on finite-element method (FEM) is presented. The thermal distribution of the QCLs on substrate-side or epilayer-side mounting forms is simulated and the results are compared. Results show that the epilayer-side mounting form has much better heat dissipation capability than the substrate-side mounting.展开更多
基金supported by the Scientific Research Project of Beijing Municipal Education Commission (No.KM202411232020)the Young Backbone Teacher Support Plan (No.YBT202408)the Scientific Researchof Beijing Information Science and Technology University (No.2023XJJ08)。
文摘Quantum cascade lasers(QCLs) have broad application potentials in infrared countermeasure system,free-space optical communication and trace gas detection.Compared with traditional Fabry-Pérot(FP) cavity and external cavity,distributed feedback quantum cascade lasers(DFB-QCLs) can obtain narrower laser linewidth and higher integration.In this paper,the structure design,numerical simulation and optimization of the Bragg grating of DFB-QCLs are carried out to obtain the transmission spectrum with central wavelength at 4.6 μm.We analyze the relationship among the structure parameters,the central wavelength shift and transmission efficiency using coupled-wave theory and finite-difference time-domain(FDTD) method.It is shown that the increase in the number of grating periods enhances the capabilities of mode selectivity,while the grating length of a single period adjustment directly determines the Bragg wavelength.Additionally,variations in etching depth and duty cycle lead to blue and red shifts in the central wavelength,respectively.Based on the numerical simulation results,the optimized design parameters for the upper buffer layer and the upper cladding grating are proposed,which gives an optional scheme for component fabrication and performance improvement in the future.
基金partly supported by National Natural Science Foundation of China(Nos.11975061,52111530088)the Technology Innovation and Application Development Project of Chongqing(No.cstc2019jscx-msxm X0041)+1 种基金the Construction Committee Project of Chongqing(No.2018-1-3-6)the Fundamental Research Funds for the Central Universities(No.2019CDQYDQ034)。
文摘Nitric oxide(NO)is one of the most crucial products in the plasma-based nitrogen fixation process.In this work,in situ measurements were performed for quantifying the NO synthesis spatially in a warm air glow discharge,through the method of Mid-infrared quantum cascade laser absorption spectroscopy(QCL-AS).Two ro-vibrational transitions at 1900.076 cm^(-1) and 1900.517 cm^(-1) of the ground-state NO(X)were probed sensitively by the help of the wavelength modulation spectroscopy(WMS)approach to increase the signal/noise(S/N)level.The results show a decline trend of NO synthesis rate along the discharge channel from the cathode to the anode.However,from the point of energy efficiency,the cathode region is of significantly low energy efficiency of NO production.Severe disproportionality was found for the high energy consumption but low NO production in the region of cathode area,compared to that in the positive column zone.Further analysis demonstrates the high energy cost of NO production in the cathode region,is ascribed to the extremely high reduced electric field E/N therein not selectively preferable for the processes of vibrational excitation or dissociation of N_(2) and O_(2) molecules.This drags down the overall energy efficiency of NO synthesis by this typical warm air glow discharge,particularly for the ones with short electrode gaps.Limitations of further improving the energy cost of NO synthesis by variations of the discharge operation conditions,such as discharge current or airflow rate,imply other effective manners able to tune the energy delivery selectively to the NO formation process,are sorely needed.
文摘A simulation method for the thermal analysis of InAlAs/InGaAs/InP mid-infrared quantum cascade lasers (QCLs) based on finite-element method (FEM) is presented. The thermal distribution of the QCLs on substrate-side or epilayer-side mounting forms is simulated and the results are compared. Results show that the epilayer-side mounting form has much better heat dissipation capability than the substrate-side mounting.
