This paper outlines our studies of bifurcation, quasi-periodic road to chaos and other dynamic characteristics in an external-cavity multi-quantum-well laser with delay optical feedback. The bistable state of the lase...This paper outlines our studies of bifurcation, quasi-periodic road to chaos and other dynamic characteristics in an external-cavity multi-quantum-well laser with delay optical feedback. The bistable state of the laser is predicted by finding theoretically that the gain shifts abruptly between two values due to the feedback. We make a linear stability analysis of the dynamic behavior of the laser. We predict the stability scenario by using the characteristic equation while we make an approximate analysis of the stability of the equilibrium point and discuss the quantitative criteria of bifurcation. We deduce a formula for the relaxation oscillation frequency and prove theoretically that this formula function relates to the loss of carriers transferring between well regime and barrier regime, the feedback level, the delayed time and the other intrinsic parameters. We demonstrate the dynamic distribution and double relaxation oscillation frequency abruptly changing in periodic states and find the multi-frequency characteristic in a chaotic state. We illustrate a road to chaos from a stable state to quasi-periodic states by increasing the feedback level. The effects of the transfers of carriers and the escaping of carriers on dynamic behavior are analyzed, showing that they are contrary to each other via the bifurcation diagram. Also,we show another road to chaos after bifurcation through changing the linewidth enhancement factor, the photon loss rate and the transfer rate of carriers.展开更多
AlGaAs/GaAs multi-quantum well (MQW) was prepared by molecular beam epitaxy(MBE) with growth-interrupted heterointerface (GIH) method and continuous growth (CG) method, respectively. The microstructures of the MQWs we...AlGaAs/GaAs multi-quantum well (MQW) was prepared by molecular beam epitaxy(MBE) with growth-interrupted heterointerface (GIH) method and continuous growth (CG) method, respectively. The microstructures of the MQWs were characterized by double-crystal X-ray rocking curve (DCRC) and atomic force microscopy (AFM), and the photoluminescence (PL) properties of the MQWs were also studied. The MQWs grown with GIH method show that higher order satellite peaks of Pendell?sung fringes are observed in DCRC, the roughness of surface is much reduced in AFM, and the full width at half maximum (FWHM) of exciton line is much narrower in PL. The results indicate that the GIH method reduces the monolayer growth step density at the heterointerface due to the migration of surface atoms for a few minutes growth interruption, and substantially improves the quality of AlGaAs/GaAs MQWs.展开更多
In this paper, a quantum cascade photodetector based on intersubband transitions in quantum wells with ability of detecting 1.33 μm and 1.55 μm wavelengths in two individual current paths is introduced. Multi quantu...In this paper, a quantum cascade photodetector based on intersubband transitions in quantum wells with ability of detecting 1.33 μm and 1.55 μm wavelengths in two individual current paths is introduced. Multi quantum wells structures based on III-Nitride materials due to their large band gaps are used. In order to calculate the photodetector parameters, wave functions and energy levels are obtained by solving 1-D Schrodinger–Poisson equation self consistently at 80 ?K. Responsivity values are about 22 mA/W and 18.75 mA/W for detecting of 1.33 μm and 1.55 μm wavelengths, respectively. Detectivity values are calculated as 1.17 × 107 (Jones) and 2.41 × 107 (Jones) at wavelengths of 1.33 μm and 1.55 μm wavelengths, respectively.展开更多
Asymmetric InGaN/GaN multiple-quantum well（MQW） light-emitting diodes were fabricated to expose the luminescence distribution and explore the hole transport.Under electrical injection,the sample with a wNQW active r...Asymmetric InGaN/GaN multiple-quantum well（MQW） light-emitting diodes were fabricated to expose the luminescence distribution and explore the hole transport.Under electrical injection,the sample with a wNQW active region in which the first QW nearest the p-side（QW1） is wider than the subsequent QWs shows a single long-wavelength light-emission peak arising from QW1.The inverse nWQW sample with a narrow QW1 shows one short-wavelength peak and one long-wavelength peak emitted separately from QW1 and the subsequent QWs.Increasing the barrier thickness between QW1 and the second QW（QWB1） in the nWQW structure,the long-wavelength peak is suppressed and the total light-emission intensity decreases.It was concluded that the nWQW and thin-QWB1 structure can improve the hole transport,and hence enhance the light-emission from the subsequent QWs and increase the internal quantum efficiency.展开更多
Based on the effective mass approximation, the Schrodinger equation and Poisson equation in GaAs/AlGaAs multi-quantum wells(MQWs) are self-consistently solved to obtain the wave functions and energy levels of electron...Based on the effective mass approximation, the Schrodinger equation and Poisson equation in GaAs/AlGaAs multi-quantum wells(MQWs) are self-consistently solved to obtain the wave functions and energy levels of electrons in the conduction band for the ground first excited state by considering a lateral electric field(LEF). Then, the effects of size, ternary mixed crystal, doping concentration, and temperature on linear and nonlinear intersubband optical absorption coefficients(IOACs), and refractive index changes(RICs) due to the transition between ground states and the first excited states of electrons are discussed based on Fermi’s golden rule. The results show that, under a fixed LEF, with increase of A1 composition and doping concentration, the IOACs produce a red shift. With increases of both widths of the wells and barriers IOACs appear as blue shifts and their amplitudes increase, but the barrier width change is much more important to affect nonlinear IOACs, whereas increasing the temperature results in a blue shift first and then a red shift of IOACs. When the other parameters are fixed but there is an increase in the LEF, IOACs occur with a blue shift, and the RICs have similar properties.展开更多
The ionization dynamics of multi-well quantum systems in intense laser fields (~ 1014W/cm) has been numerically investigated through solving the time-dependent Schrodinger equation. The enhanced ionization effect at a...The ionization dynamics of multi-well quantum systems in intense laser fields (~ 1014W/cm) has been numerically investigated through solving the time-dependent Schrodinger equation. The enhanced ionization effect at a critical inter-well distance is found as a general feature of multi-well quantum systems subjected to intense laser fields. It is well rationalized in terms of.the field-induced over-the-barriers ionization mechanism. With the number of wells increasing the whole ionization peak slightly shifts to small inter-well distance, but the enhanced ionization tendency still keeps. The ionization potential of multi-well systems is not the sole important factor of intense field-ionization of system.展开更多
对 Ga As/ Al Ga As量子阱红外探测器器件进行显微荧光光谱 (μ- PL)测量 ,光谱中表征势垒、势阱基态间光跃迁能量位置的荧光峰直接与势垒中 Al含量相关 ,通过光谱实验上对势垒和量子阱带间跃迁能量的确定并结合有效质量理论的计算 ,获...对 Ga As/ Al Ga As量子阱红外探测器器件进行显微荧光光谱 (μ- PL)测量 ,光谱中表征势垒、势阱基态间光跃迁能量位置的荧光峰直接与势垒中 Al含量相关 ,通过光谱实验上对势垒和量子阱带间跃迁能量的确定并结合有效质量理论的计算 ,获得了 Al组分和阱宽值 ,并由此推算出相应的红外探测响应波长 ,与光电流谱的实验结果相比吻合良好 .展开更多
文摘This paper outlines our studies of bifurcation, quasi-periodic road to chaos and other dynamic characteristics in an external-cavity multi-quantum-well laser with delay optical feedback. The bistable state of the laser is predicted by finding theoretically that the gain shifts abruptly between two values due to the feedback. We make a linear stability analysis of the dynamic behavior of the laser. We predict the stability scenario by using the characteristic equation while we make an approximate analysis of the stability of the equilibrium point and discuss the quantitative criteria of bifurcation. We deduce a formula for the relaxation oscillation frequency and prove theoretically that this formula function relates to the loss of carriers transferring between well regime and barrier regime, the feedback level, the delayed time and the other intrinsic parameters. We demonstrate the dynamic distribution and double relaxation oscillation frequency abruptly changing in periodic states and find the multi-frequency characteristic in a chaotic state. We illustrate a road to chaos from a stable state to quasi-periodic states by increasing the feedback level. The effects of the transfers of carriers and the escaping of carriers on dynamic behavior are analyzed, showing that they are contrary to each other via the bifurcation diagram. Also,we show another road to chaos after bifurcation through changing the linewidth enhancement factor, the photon loss rate and the transfer rate of carriers.
文摘AlGaAs/GaAs multi-quantum well (MQW) was prepared by molecular beam epitaxy(MBE) with growth-interrupted heterointerface (GIH) method and continuous growth (CG) method, respectively. The microstructures of the MQWs were characterized by double-crystal X-ray rocking curve (DCRC) and atomic force microscopy (AFM), and the photoluminescence (PL) properties of the MQWs were also studied. The MQWs grown with GIH method show that higher order satellite peaks of Pendell?sung fringes are observed in DCRC, the roughness of surface is much reduced in AFM, and the full width at half maximum (FWHM) of exciton line is much narrower in PL. The results indicate that the GIH method reduces the monolayer growth step density at the heterointerface due to the migration of surface atoms for a few minutes growth interruption, and substantially improves the quality of AlGaAs/GaAs MQWs.
文摘In this paper, a quantum cascade photodetector based on intersubband transitions in quantum wells with ability of detecting 1.33 μm and 1.55 μm wavelengths in two individual current paths is introduced. Multi quantum wells structures based on III-Nitride materials due to their large band gaps are used. In order to calculate the photodetector parameters, wave functions and energy levels are obtained by solving 1-D Schrodinger–Poisson equation self consistently at 80 ?K. Responsivity values are about 22 mA/W and 18.75 mA/W for detecting of 1.33 μm and 1.55 μm wavelengths, respectively. Detectivity values are calculated as 1.17 × 107 (Jones) and 2.41 × 107 (Jones) at wavelengths of 1.33 μm and 1.55 μm wavelengths, respectively.
基金supported by the National High Technology Research and Development Program of China(No.2006AA03A122)the Knowledge Innovation Program of the Chinese Academy of Sciences(No.ISCAS2009T02)
文摘Asymmetric InGaN/GaN multiple-quantum well（MQW） light-emitting diodes were fabricated to expose the luminescence distribution and explore the hole transport.Under electrical injection,the sample with a wNQW active region in which the first QW nearest the p-side（QW1） is wider than the subsequent QWs shows a single long-wavelength light-emission peak arising from QW1.The inverse nWQW sample with a narrow QW1 shows one short-wavelength peak and one long-wavelength peak emitted separately from QW1 and the subsequent QWs.Increasing the barrier thickness between QW1 and the second QW（QWB1） in the nWQW structure,the long-wavelength peak is suppressed and the total light-emission intensity decreases.It was concluded that the nWQW and thin-QWB1 structure can improve the hole transport,and hence enhance the light-emission from the subsequent QWs and increase the internal quantum efficiency.
基金Project supported by the National Natural Science Foundation of China(No.61764012)
文摘Based on the effective mass approximation, the Schrodinger equation and Poisson equation in GaAs/AlGaAs multi-quantum wells(MQWs) are self-consistently solved to obtain the wave functions and energy levels of electrons in the conduction band for the ground first excited state by considering a lateral electric field(LEF). Then, the effects of size, ternary mixed crystal, doping concentration, and temperature on linear and nonlinear intersubband optical absorption coefficients(IOACs), and refractive index changes(RICs) due to the transition between ground states and the first excited states of electrons are discussed based on Fermi’s golden rule. The results show that, under a fixed LEF, with increase of A1 composition and doping concentration, the IOACs produce a red shift. With increases of both widths of the wells and barriers IOACs appear as blue shifts and their amplitudes increase, but the barrier width change is much more important to affect nonlinear IOACs, whereas increasing the temperature results in a blue shift first and then a red shift of IOACs. When the other parameters are fixed but there is an increase in the LEF, IOACs occur with a blue shift, and the RICs have similar properties.
文摘The ionization dynamics of multi-well quantum systems in intense laser fields (~ 1014W/cm) has been numerically investigated through solving the time-dependent Schrodinger equation. The enhanced ionization effect at a critical inter-well distance is found as a general feature of multi-well quantum systems subjected to intense laser fields. It is well rationalized in terms of.the field-induced over-the-barriers ionization mechanism. With the number of wells increasing the whole ionization peak slightly shifts to small inter-well distance, but the enhanced ionization tendency still keeps. The ionization potential of multi-well systems is not the sole important factor of intense field-ionization of system.
