Spontaneous emission control in quantum well laser diodes (original) (raw)
Related papers
The Physics of the Quantum Well Laser
Physica Scripta, 1987
This paper reviews some of the properties of quantum well lasers (QWLs), with emphasis on the two-dimensional origins of these. It is shown that two main effects determine the lowering of threshold current, namely the diminished density of states (DOS) (favourable factor) and the diminished optical confinement (unfavorable factor). The good operation of GaAs-GaAlAs QWLs also relies on more subtle effects such as the square 2D DOS, the enhanced optical matrix element, the high quantum efficiency. .. The poor operation of GaInAs based quantum well lasers is due to the detrimental Auger effect which is larger than in 3D lasers because of the higher carrier densities at which QWLs operate. Several other useful properties of QWLs in the performance (high-frequency, narrow-line) and manufacturing fields are discussed. Problems and advantages of 1 and OD quantum-wire and quantum-box lasers are briefly evaluated.
Switching between generation of two quantum states in quantum-well laser diodes
2008
The dynamics of emission spectra in semiconductor quantum-well lasers generating from two quantum states have been experimentally studied. In the case of electric pumping with 100-ns pulses, the lasing via transitions from the ground state is switched off and the emission from an excited state is switched on within 10-50 ns after laser turn-on. The switching is accompanied by a dip in the intensity of lasing, the duration of which depends on the pumping pulse amplitude. The observed phenomenon is explained in terms of gain saturation (clamping) and redistribution of the carrier concentration between the ground and excited states.
Theory of reduced threshold current density in GaAs/AlGaAs quantum well lasers
Superlattices and Microstructures, 1990
It has recently been demonstrated that (111) GaAs/AlGaAs quantum well lasers can have a lower threshold current density than equivalent (001) lasers. We have used the envelope function method to calculate the hole confinement energies and valence subband dispersion energies of (111) and (001) quantum wells of varying width. We find that the differences in the vlrlence subband dispersion can account fully for the measured differences in threshold current densities. The heavy-hole mass is significantly larger dong (111) than aIong the conventional (001) growth direction. This increases the number of heavy-hole confined states for a given weJI width. Away from the zone centre, the subband dispersion in the well plane shows less mixing between heavy-and light-hole bands than for (001) growth and, in thin we&, the highest subband has a low in-plane effective mass over a greater energy range, resulting in a reduced density of states at the valence band maximum. Laser gain calculations show that this enhanced light-hole behaviour can explain the reduction in threshold current density of (111) lasers compared to equivalent (001) lasers, in good agreement with experimental observation. We also calculate optical matrix elements for TE and TM modes and find that in thin (111) lasers, an improved selection of TE over TM modes is possible, due mainly to the different subband orderings in the two growth directions. This leads to the elimination in (111) lasers of the TM jump of the laser mode observed in some (001) lasers and its replacement by a TE jump, in agreement with experimental observations.
Modulation of quantum well lasers by short optical excitation: energy and spatial dependent effects
IEEE Photonics Technology Letters, 1995
We describe an energy-resolved and spatially selective time domain technique for optically excited measurements of diode laser modulation responses. We report application of the technique to a study of an InGaAs-GaAs quantum well laser. We emphasize the significance of the spatial characteristics of the excitation in resolving effects related either solely to the active region or to the entirety of the laser structure.
Carrier dynamics and microwave characteristics of GaAs-based quantum-well lasers
IEEE Journal of Quantum Electronics, 1999
We investigate the effects of carrier capture and re-emission on the electrical impedance, equivalent circuit, and modulation response of quantum-well (QW) laser diodes. The electrical impedance is shown to be a sensitive function of the time constants associated with carrier capture/transport and carrier re-emission. We compare the theoretical results with measured values of the electrical impedance of high-speed InGaAs-GaAs multiple-quantum-well lasers fabricated using different epilayer structures with a common lateral structure. The experimental results agree well with the theoretical model, allowing us to extract the effective carrier escape time and the effective carrier lifetime in the QW's, and to estimate the effective carrier capture/transport time.
Two-dimensional simulation of quantum well lasers
European Transactions on Telecommunications, 1990
A versatile two-dimensional simulator for various types of semiconductor lasers for both steady state and transients has been developed. The simulator is capable of spectral analysis of quantum-well semiconductor lasers, such as gain-spectrum analysis, as well as analysis of the two-dimensional current flow and optical intensity patterns. The simulator is based on the drift-diffusion model with full Fermi-Dirac statistics for the transport equations as well as for the Poisson equation. Simulation of the thermionic emission current is required at the abrupt heterointerfaces of the quantum well. For the spectral analysis of quantum-well lasers, we have used the photon rate equation for each Fabry-Perot mode. For the optical intensity pattern, we have solved the two-dimensional Helmholtz eigenvalue equation using the subspace iteration method. The transient simulation is done by the full backward-Euler method in conjunction with the full Newton approach for the entire semiconductor equations. To demonstrate the simulator, a model GaAs-AIGaAs graded-index-separate-confinement-heterostructure buriedquantum-well laser is analyzed. (*) This work has been supported by the National Science Foundation through the Engineering Research Center of the University of Illinois at Urbana-Champaign and the Office of Nova1 Research under the SDIO-IST program.
IEEE Journal of Selected Topics in Quantum Electronics, 2002
By measuring the spontaneous emission (SE) from normally operating 1.3-m GaInNAs-GaAs-based lasers we have quantitatively determined the variation of each of the current paths present in the devices as a function of temperature from 130 K to 370 K. From the SE measurements we determine how the current close to threshold, varies as a function of carrier density n, which enables us to separate out the main current paths corresponding to monomolecular (defect-related), radiative or Auger recombination. We find that defect-related recombination forms 55% of the threshold current at room temperature (RT). At RT, radiative recombination accounts for 20% of th with the remaining 25% being due to nonradiative Auger recombination. Theoretical calculations of the threshold carrier density as a function of temperature were also performed using a ten-band
AIP Conference Proceedings, 2008
Quantum well width effect on threshold current density and optical performance of InGaN/GaN single quantum well (SQW) laser diode was determined and investigated. Various thickness (2-5nm) of InO.13GaO.87N wells and 12nm GaN barriers were selected as an active region for Fabry-Perot (FP) cavity waveguide edge emitting laser diode. The quantum confined Stark created a strong quantum well width dependence of threshold current density in the strained InGaN/GaN quantum well laser. Based on our simulation investigation, the exciton localization effect dominated the recombination emission in the thin quantum well structure; while the quantum confined stark effect (QCSE) dominated the recombination emission in the wide quantum well structure. Higher characteristic temperatures were obtained and significantly improved when the quantum well thickness was (2 to 3nm).