Auger recombination effect on threshold current of InGaAsP quantum well lasers

The Auger recombination effect on the threshold current of the InGaAsP quantum well (QW) laser is studied theoretically. All possible transitions between the quantized subbands of two-dimensional carriers are taken into account in evaluating the radiative process with thek-selection rule and the Auger process. The calculated threshold current agrees well with the reported experimental results for 1.07 μm InGaAsP QW lasers. The Auger component of the threshold current and its temperature dependence strongly depend on the QW structure, resulting in the necessity for an elaborate QW structure design, although both cannot be optimized at the same time. A design procedure is elucidated for a structure which gives the lowest threshold current density for the 1.07, 1.3, and 1.55 μm InGaAsP QW lasers.     

Optimal quantum well width and the effect of quantum well position on the performance of transistor lasers

Transistor laser (TL) model based on InGaP/GaAs/InGaAs/GaAs is analyzed and presented. It is realized that quantum well (QW) with width of 10 nm may be formed for low base threshold current density J th . The emission wavelength is found to be 1.05 μm, and the indium (In) composition is 0.25 for optimal QW width. It is identified that J th decreases with the movement of QW towards the base-emitter (B-E) interface. Small signal optical response is calculated, and the effect of QW position is studied. The bandwidth is enhanced due to the movement of the QW towards the emitter base junction.     

Lifetime broadening in GaAs-AlGaAs quantum well lasers

Experimental observations of spontaneous emission spectra from GaAs-AlGaAs quantum well lasers shown that spectral broadening should be included in any realistic model of laser performance. A model of the lifetime broadening due to intraband Auger processes of the Landsberg type is described and developed for the case of electron-electron scattering in a 2-D system. The model is applied to the calculation of gain and spontaneous emission spectra and gain-current relationships in short-wavelength GaAs-AlGaAs quantum well lasers, and the results are compared with those obtained using both a fixed intraband scattering time and one that varies as n^-1/2, where n is the volume injected carrier density     

Well-barrier hole burning in quantum well lasers

The reported wide variations in the damping behavior of quantum well lasers are explained by a novel theory of nonlinear gain, well-barrier hole burning. In the model a spatial hole develops perpendicular to the active region involving carriers moving between the wells and the barrier/confinement layers. The modified rate equations describing well-barrier hole burning are presented. An analytical approximation for the nonlinear gain coefficient epsilon , valid only under certain conditions, is given. A numerical solution is given for the case of high photon densities and large capture-times. It is shown how well-barrier hole burning explains the measurements of the increased spontaneous emission from the barrier/confinement region above threshold. Various higher-than-expected damping rates reported in some quantum well lasers are shown to be consistent with the model.<>     

Simulation of semiconductor quantum well lasers

A new quantum well laser simulator that accounts for details of carrier transport, distribution of two-dimensional (2-D) carriers within the quantum well, optical gain spectra, and photon rate equations, is presented. The resulting set of complicated equations is solved using “slack variables”-a new algorithm that is both efficient and stable. Results are compared with experiments to verify the simulator     

20000 h InGaAs quantum well lasers

Strained-layer GRINSCH-SQW InGaAs lasers operating CW at 1.01 mu m have been CW life tested to over 20000 h while exhibiting an average degradation rate of 1.3% per kh. These uncoated lasers were life tested at 70 mW (per facet) in constant power mode at a heatsink temperature of 30 degrees C. In addition to their longevity, these lasers exhibited a resistance to sudden failure with an unscreened sample of fifteen lasers experiencing total survival to 10000 h.<>     

Linewidth enhancement factor in strained quantum well lasers

The linewidth enhancement factor α of strained quantum-well lasers is analyzed by the k-p perturbation method using the effective-mass approximation. It is found that the α factor in a strained In_0.80Ga_0.20As/InP quantum-well (QW) laser with 1.9% biaxial compression is less than 1.5. For a strained QW laser with p-type modulation doping (MD) of 5×10 ¹⁸ cm^-3, the α factor is as small as 0.8. It is also demonstrated that the spectral linewidth and wavelength chirping in the strained MD QW laser are significantly less than those in conventional bulk and QW lasers     

Threshold currents for AlGaAs quantum well lasers

The threshold currents for AlGaAs quantum well lasers are studied theoretically. The structure dependent gain coefficient is obtained by taking into account the electron distribution inLvalleys. Theoretical threshold current densities calculated using the gain coefficient agree well with reported experimental results for separate-confinement heterostructure lasers. A design procedure for low threshold current laser is elucidated. The lowest threshold currents are 570 and 53 μA per 1 μm stripe width for modified multiple quantum well lasers with 32 percent and 90 percent reflectivity facet mirrors, respectively.     

Strained InGaAs quantum well lasers grown on

The growth by molecular beam epitaxy (MBE) of AlGaAs/GaAs/InGaAs strained quantum well lasers on GaAs     

AlGaInP/GaInAs strained quantum well lasers

AlGaInP cladding layers have been applied for the first time to GaInAs strained quantum well lasers oscillating around 0.98 mu m. The device has lower threshold current and larger T/sub 0/ than a device with GaInP cladding layers. This was expected from a larger bandgap difference between active and cladding layers.<>     

量子阱激光器的阈值电流和外量子效率

地于半导体分别限制单量子阱激光器，为了降低阈值电流，提高外量子效率，分析和讨论了影响阈值电流和外量子效率的各种因素，并做了一定的数值计算，给出了量佳结构参数。     

Carrier capture and escape in multisubband quantum well lasers

Carrier capture and escape processes between quantum wells and barriers via carrier-polar optical phonon interactions are theoretically studied in multisubband quantum well structures. We find that carriers in each subband have their own minimum capture and escape times when the energy difference between the band edges of the subbands and the barrier is equal to the energy of a longitudinal optical phonon. Our results indicate that carrier escape time is more quantum well structure-dependent while carrier capture time is less structure-dependent. Explicit forms for calculating carrier capture and escape times are given which are crucial for designing the quantum well structures with optimal capture or escape efficiencies     

Differential gain in bulk and quantum well diode lasers

Differential gain (g^') of bulk and single-quantum-well (SQW) lasers was determined from threshold current density and differential quantum efficiency measurements. The threshold measurement technique was used to show that g^' is a function of cavity length (L) in SQW lasers and independent of L in bulk lasers. It was found that g^' of long SQW lasers (1000 μm) is about 7×10^-16 cm² , approximately two times that of bulk lasers. At short cavity lengths (250 μm), g^' is about the same for both laser types     

Gain and index measurements in GaAlAs quantum well lasers

Measurements of the modal gain and group index in GaAlAs single-quantum-well (SQW) lasers are presented. The elimination of substrate emission has allowed accurate results to be obtained even in the near-bandgap and below-bandgap spectral regions. Substantial lifetime broadening is observed, and the gain smoothly goes to zero as the bandgap is approached. The group velocity index measurements indicate a dispersion of -3.44 μm^-1     

单模AlGaAs／GaAs脊形波导量子阱半导体激光器

本文报道用分子束外延设备研制梯度折射率分别限制式单量子阱AlGaAs/GaAs脊形波导半导体激光器。该激光器具有良好的性能,条宽5μm器件室温阈值电流23mA,线性连续输出单模激光功率大于15mW。     

Gain-coupled DFB lasers with truncated quantum well second-ordergratings

Static and dynamic properties of in-phase gain-coupled multiple quantum well distributed feedback (DFB) lasers with second-order gratings have been measured at 1.55 μm. Devices with both facets antireflection coated and with a κL product between 4 and 5 have achieved a sidemode suppression ratio of over 63 dB. Relative intensity noise measurements have confirmed that the dynamic properties of second-order truncated well gain-coupled (GC)-DFB lasers are comparable to those with first-order truncated-well gratings     

光子晶体使面发射量子级联激光器成为可能

将光子晶体共振腔内置到量子级联激光器中，美国的研究人员已开发出一种小型的面发射激光器。这种激光器将在化学传感、光谱分析及成像中具有潜在的应用。美国新泽西州默里希尔的贝尔试验室和帕萨迪纳州的加利福尼亚工学院的科研小组共同研制的中红外激光器可作为研究光子晶体及微腔作用的样机系统。     

Critical thickness in strained-layer GaInAs/GaAs quantum well lasers

The critical thickness in strained-layer GaInAs/GaAs quantum well lasers was studied by measuring the dependence of the threshold current on the number of quantum wells. The critical thickness for 20% In composition was found to be around 30 nm, which is twice as large as predicted by the Matthews-Blakeslee model.<>     

Nonlinear gain effects on spectral dynamics in quantum well lasers

A theoretical analysis is presented to show how nonlinear gain affects the spectral dynamics of quantum well (QW) lasers. The results indicate that the nonlinear gain, which is enhanced by the quantum confinement of carriers, causes an increase in the linewidth enhancement factor alpha . This enhancement of alpha results in spectral rebroadening: under high power output conditions. These properties should be taken into account when quantum well lasers are designed for highly coherent lasers.<>     

On carrier injection and gain dynamics in quantum well lasers

A detailed carrier dynamics model for quantum well lasers is presented. The model describes the transport of carriers using full continuity equations and the gain by rate equations for each well separately, and it also takes into account electron-hole interactions which modify the energy band structure. To this end, the model includes Poisson and Schrodinger equations. The model is solved in steady state where it yields nonuniform carrier distributions along the crystal growth axis. Dynamically, the model is solved in the time domain, yielding the evolution of carriers in time and space and highlighting a new effect, photon-assisted carrier transport. The model is also solved in the small-signal regime where the phase lag in gain between wells is determined