Low linewidth enhancement factor for InGaAsP and InGaAIAs multiple quantum well lasers

A comparative measurement is reported of the linewidth enhancement factor of bulk and multiple quantum well (MQW) long-wavelength diode lasers using the chirp halfwidth product method. Although MQW lasers provide substantially improved chirp performance compared with bulk devices, this depends considerably on the drive conditions when gain switching.     

InGaAs/GaAs应变量子阱激光器线宽展宽因子的理论研究

详细地介绍了计算线宽展宽因子(α因子)的理论基础及推导过程, 建立了α因子的简便模型. 该模型分别考虑了带间跃迁、带隙收缩和自由载流子效应对α因子的影响, 利用不同载流子浓度下的增益曲线得到光子能量随载流子浓度的变化速率以及微分增益, 进而对α因子进行近似计算. 模拟计算了InGaAs/GaAs量子阱激光器的增益曲线及α 因子的大小, 计算结果与文献报道的实验值相符. 进一步讨论了InGaAs/GaAs量子阱阱宽及In组分对α 因子的影响. 结果表明, α 因子随In组分和阱宽的增加而增加.     

Analysis of linewidth enhancement factor for compressively strained AlGaInAs and InGaAsP quantum well lasers

We have compared and analyzed theoretical investigation for the possibility of extreme reductions in the linewidth enhancement factor (??-factor) in strained layer quantum-well (QW) lasers between AlGaInAs and InGaAsP material. Valence band effective masses and optical gain in both types of QW lasers under compressive strain have been calculated using 4 ×?4 Luttinger?CKohn Hamiltonian. We have used Kramers?CKronig relations to calculate the refractive index change due to carrier induced. The ??-factor was up to 1.61 times smaller in AlGaInAs QW than in InGaAsP QW laser. The material differential modal gain and carrier induced refractive index change was found to be approximately 1.38 times larger and 1.15 times smaller respectively, in the previous material QW than in the latter QW laser. We also compared our results to the previously reported results for both QWs lasers.     

Narrow luminescence linewidth of a silicon quantum dot

Single-dot luminescence spectroscopy was used to study the emission linewidth of individual silicon nanocrystals from low temperatures up to room temperature. The results show a continuous line narrowing towards lower temperatures with a linewidth as sharp as 2 meV at 35 K. This value, clearly below the thermal broadening at this temperature, proves the atomiclike emission from silicon quantum dots subject to quantum confinement. The low temperature measurements further reveal a approximately 6 meV replica, whose origin is discussed. In addition, an approximately 60 meV TO-phonon replica was detected, which is only present in a fraction of the dots.     

Subnatural linewidth single photons from a quantum dot

The observation of quantum-dot resonance fluorescence enabled a new solid-state approach to generating single photons with a bandwidth approaching the natural linewidth of a quantum-dot transition. Here, we operate in the small Rabi frequency limit of resonance fluorescence--the Heitler regime--to generate subnatural linewidth and high-coherence quantum light from a single quantum dot. The measured single-photon coherence is 30 times longer than the lifetime of the quantum-dot transition, and the single photons exhibit a linewidth which is inherited from the excitation laser. In contrast, intensity-correlation measurements reveal that this photon source maintains a high degree of antibunching behavior on the order of the transition lifetime with vanishing two-photon scattering probability. Generating decoherence-free phase-locked single photons from multiple quantum systems will be feasible with our approach.     

Dissipative solitons in quantum dot lasers

The spatiotemporal dynamics of radiation in wide-aperture semiconductor quantum-dot lasers is studied analytically and numerically. It was found that the choice of relatively rapid amplifying layers with quantum dots of a small size and slow absorbing layers with a maximal rate of exciton capture from wetting layers is optimal for the stability of spatial dissipative solitons in a single-longitudinal-mode laser. A large relaxation time of the slow absorber was found to result in a substantial decrease in the sensitivity of solitons to the tilt of the mirrors, which increases their stability and gives real chances of the experimental revealing of laser solitons.     

Kilohertz linewidth from frequency-stabilized mid-infrared quantum cascade lasers

Frequency stabilization of mid-IR quantum cascade (QC) lasers to the kilohertz level has been accomplished by use of electronic servo techniques. With this active feedback, an 8.5-microm QC distributed-feedback laser is locked to the side of a rovibrational resonance of nitrous oxide (N(2) O) at 1176.61cm (-1) . A stabilized frequency-noise spectral density of 42Hz/ radicalHz has been measured at 100 kHz; the calculated laser linewidth is 12 kHz.     

Thresholds of quasi-supercontinuum interband quantum dot lasers

We present the analysis of threshold conditions that produces wideband- stimulated emission in semiconductor quantum-dot laser. Our theoretical model reveals critical occurrence of broadband lasing when the energy spacing between quantized energy states (ΔE) is comparable to the inhomogeneous broadening of quantum dot nanostructures.     

Stability properties of current-profiled quantum dot lasers

The stability properties of injection-current profiled quantum dot lasers are analyzed for broad area devices of different length. In general, devices demonstrate stable output at low to moderate injection levels before the onset of filamentary dynamics at higher injection levels. By comparing devices of different lengths, the onset of filamentary dynamics is shown to coincide in each case with the onset of excited state lasing and so the loss in stability may be linked to the increased low frequency noise and phase-amplitude coupling that occurs in this regime.     

Influence of linewidth enhancement factor $$\alpha $$ on self-mixing interferometry in solid-state lasers

Optical Review - Up to now, laser self-mixing interferometry (SMI) has been widely applied to numerous scientific and industry fields. A easily negligible parameter, linewidth enhancement factor...     

Proton radiation effects in quantum dot lasers

Proton beams with energies of 10 and 200 MeV were irradiated onto InAs quantum dot lasers with a wavelength of 1.3 μm. The increase in threshold current by proton irradiation was small compared with those of the previously reported other quantum dot lasers with larger active region and 1.3-μm InGaAsP quantum well lasers. These results were discussed by taking account of non-ionizing energy loss and effective volume of active region.     

Ground and first excited state energies of impurity-bound polaron in a parabolic quantum dot

A Landau–Pekar variational theory is employed to obtain the ground and the first excited state binding energies of an electron bound to a Coulomb impurity in a polar semiconductor quantum dot (QD) with parabolic confinement in both two and three dimensions. It is found that the binding energy increase with increasing the Coulomb binding parameter and increase with the decrease in size of the QD and is much more pronounced with decreasing dimensionality.     

Low-frequency fluctuations in two-state quantum dot lasers

We study the feedback-induced instabilities in a quantum dot semiconductor laser emitting in both ground and excited states. Without optical feedback the device exhibits dynamics corresponding to antiphase fluctuations between ground and excited states, while the total output power remains constant. The introduction of feedback leads to power dropouts in the ground state and intensity bursts in the excited state, resulting in a practically constant total output power.     

Simulation of characteristics of broadband quantum dot lasers

Authors theoretically present the characterization of the multiple states broadband InGaAs/GaAs quantum-dot lasers that agrees well with the measured data. Based on the derived model, this new class of semiconductor laser is further characterized theoretically to gain an idea of the derivative characteristic such as linewidth enhancement factor in providing a picture of the competency of this novel device for diverse applications.     

Nonlinear dynamics of doped semiconductor quantum dot lasers

We discuss the influence of wetting layer doping on the turn-on dynamics of a quantum dot (QD) laser by using a microscopically based rate equation model which separately treats the dynamics of electrons and holes. As the carrier-carrier scattering rates depend nonlinearly on the wetting layer carrier densities we observe drastic changes of relaxation oscillation frequency and damping if the wetting layer is doped. We gain insight into the nonlinear dynamics of the QD laser by a detailed analysis of various sections of the five-dimensional phase space focusing on changes in the coupling between QD electron and holes dynamics.     

A review of external cavity-coupled quantum dot lasers

Since the external cavity quantum dot laser was first demonstrated, the performances have been improved in terms of operation temperature, output power, pulse generator and tuneability based on the naturally size fluctuation of quantum dot. Nowadays, the external cavity quantum dot sources have been successfully used in different absorption spectroscope techniques, in industry, biomedical and research. In this paper we reviewed the recent developments of quantum dot lasers operated in a grating-coupled external cavity system where a single frequency and wide tunable wavelength range were easily obtained by adjusting the grating angle. In all cases, we mainly stressed the significant progresses in understanding of basic optical and electronic properties to enable the importance steps forward. The prospects for further progress directed towards stability, mode-hoping-free tuning range, miniaturization and integration of the external cavity quantum dot lasers also reviewed.     

Beam properties of injection profiled quantum dot lasers

The impact of injection current profiling on the spatial mode structure of quantum dot semiconductor lasers is investigated. Numerical simulations based on a spatial extension of a simple rate equation model for quantum dot devices reveal the role of non-resonant carries in the appearance of strong dips in the optical field of the device. Symmetry breaking may also occur whereby the position of the dip shifts from the centre of the injection region.     

抛物量子点中强耦合磁双极化子内部激发态性质

基于Lee-Low-Pines幺正变换,采用Pekar类型变分法研究了抛物量子点中强耦合磁双极化子的内部激发态性质,当考虑自旋和外磁场影响时,推导出二维量子点中强耦合磁双极化子基态的能量E0,声子平均数ˉN0以及第一激发态的能量E1,声子平均数ˉN1随量子点受限强度ω0,介电常数比η,电子-声子耦合强度α和磁场的回旋共振频率ωC的变化规律.结果表明,磁双极化子的基态能量E0和第一激发态能量E1由两电子的单粒子能量E E,两电子间库仑相互作用能E C,电子自旋与磁场相互作用能E s和电子-声子相互作用能E e-ph四部分组成;单粒子"轨道"运动与磁场相互作用导致了第一激发态能级E1分裂为E(1+1)1,E(1-1)1两条,而电子自旋-磁场相互作用的效应又使基态和第一激发态的各能级均产生了三条"精细结构";ˉN0和ˉN1随ω0,α和ωc的增加而增大,E e-ph的取值总是小于零,其绝对值随α,ω0和ωc的增加而增大;电子-声子相互作用的效应是束缚态磁双极化子形成的有力因素,而限定势和电子之间的库仑排斥能的存在不利于束缚态磁双极化子的形成;能量为E(1-1)1的磁双极化子要比能量为E(1+1)1的磁双极化子更容易且更稳定地处于束缚态.     

Voltage-controlled linewidth of excitonic transitions in a single self-assembled quantum dot

We report electron and hole tunnelling phenomena in a single self-assembled quantum dot as a function of the applied electric field. We use absorption spectroscopy which allows us to measure excitonic transitions under conditions where optical recombination cannot be observed due to the high, ionizing, electric field.