Gain saturation in semiconductor lasers: Theory and experiment (original) (raw)
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Effect of gain saturation on the current-power characteristic of semiconductor laser
Technical Physics Letters, 2012
It is shown that, when temperature effects are excluded, even a small bend of the current-power characteristic of a semiconductor laser caused by gain saturation indicates that the carrier concentration that is necessary to maintain lasing should be increased by several times (i.e., that the effective lasing threshold significantly increases).
Minority carrier lifetimes and lasing thresholds of PbSnTe heterostructure lasers
IEEE Journal of Quantum Electronics, 1979
PbSnTe is presented which yields lifetimes an order of magnitudegreater than previously accepted values. These results are used in combination with recent measurements of minority carrier lifetime and interface recombination velocity in PbSnTe double heterojunction laser structures to calculate DH laser thresholds. It is demonstrated that radiative recombination is a relatively inefficient process in present F'bSnTe lasers, and that when this inefficiency is taken into account the magnitude of the experimentally observed threshold and its variation with active region width and temperature can be accurately predicted, even at low temperatures where all previous models have failed.
Nonlinear gain model and its application for numerical investigation of semiconductor lasers
1999
The optimization of parameters and adequate methods of modeling for the creation of new types of semiconductor lasers with impro¨ed properties are required. In this work, a numerical model of gain is presented, which contains a complex description of the linear and nonlinear effects in an acti¨e layer. We show the more exact conformity of the gi¨en model to experimental data for large le¨els of light power and pumping currents. The original method of calculations of the total ( ) density states function for the quantum well QW laser is shown. The gi¨en expression has allowed us to reduce the model calculation time.
Side-mode gain in semiconductor lasers
Journal of the Optical Society of America B, 1992
Side-mode gain and coupling coefficients in semiconductor laser media are calculated with the use of a multimode Fourier technique valid both for mode spacings that are small compared with the carrier-carrier relaxation rates and for spacings comparable with these rates as predicted by the Boltzmann theory of Binder et al. [Phys. Rev. B 45, 1107]. The medium is described by a free-carrier model that provides for carrierprobability pulsations around quasi-equilibrium Fermi-Dirac values. We find that population pulsations play just as important a role as spectral hole burning for mode spacings comparable with the intraband relaxation rates. For the carrier-carrier relaxation rates of Binder et al., side-mode gain is predicted to be smaller than the main-mode gain, leading to single-mode operation. However, for somewhat smaller intraband relaxation rates, side-mode gain is readily found that exceeds the single-mode gain, which would encourage multimode operation. In addition, we find that the gain and coupling coefficient spectra are sensitive to the k dependence of the carrier-carrier relaxation rates and might provide a useful way to measure these rates. We are also able to explain the asymmetric side-mode gain spectra for small beat frequencies in terms of the rapid decrease of the quasi-equilibrium Fermi-Dirac electron distribution just above the gain region.
Semiconductors, 2006
It is shown that the reason why the maximum attainable optical power in semiconductor lasers is limited is the finite time of carrier energy relaxation via scattering by nonequilibrium optical phonons in the quantum-well active region. The power and spectral characteristics of semiconductor lasers are studied experimentally at high excitation levels (up to 100 kA/cm 2 ) in pulsed lasing mode (100 ns, 10 kHz). As the drive current increases, the maximum intensity of stimulated emission tends to a constant value ("saturates"), and the emitted power increases owing to extension of the spectrum to shorter wavelengths. The intensity saturation is due to limitation of the rate of stimulated recombination, caused by a finite time of the electron energy relaxation via scattering by polar optical phonons. It is found that the broadening of the stimulated emission spectrum is related to an increase in carrier concentration in the active region, which enhances the escape of electrons into the waveguide layers. As the drive current increases, the carrier concentration in the waveguide reaches its threshold value and there appears an effective channel of current leakage from the active region. The experiment shows that the appearance of a band of waveguide lasing correlates with a sharp drop in the differential quantum efficiency of a semiconductor laser.
IEEE Journal of Quantum Electronics, 1991
A density matrix equation for semiconductor lasers has been derived from the microscopic equation of motion for electrons using a projection operator method. The effect of non-Markovian intraband relaxation has been found to be described by the autocorrelation functions of electron scattering terms in the microscopic interaction Hamiltonian. The obtained density matrix equation provides a systematic treatment for dynamical properties of semiconductor lasers, and the treatment can be performed by calculating the autocorrelation functions from available material parameters. A gain formula for arbitrary light output power has been derived from a single-mode steady-state nonperturbative solution. A simplified estimation employing a stochastic model has shown that non-Markovian intraband relaxation enhances both linear gain and nonlinear gain. The reduction of nonlinear gain effects is also discussed.
Long-wavelength PbSnTe-PbTeSe lattice-matched single-heterestructure lasers grown by LPE
IEE Proceedings I Solid State and Electron Devices
Properties of Pbix Sn x Te-PbTeiy Se y lattice-matched single-heterostructure (SH) diode lasers grown on Pbi-^Sn^Te substrates by liquid-phase epitaxy were studied for various compositions in the range 0.13 < x < 0.24, which corresponds to a wavelength range of 12/um to 18.5 Mm (at T = 20K). Threshold current density J t^ was measured as a function of temperature from 10 K to 140 K, and was found to be comparable to that observed previously in PbSnTe-PbTeSe and PbSnTeSe-PbTeSe DH lasers. An external differential quantum efficiency of 1-2% was measured in these lasers. The emission spectra of the SH lasers frequently show a single-mode structure for J<2J th at high temperatures. Measurements of i/V characteristics carried out in these lasers suggest that tunnelling currents contribute significantly to the observed threshold current density. At high temperatures, characteristic temperatures T o in the range 16.5 to 21 K were measured.
Influence of doping on gain characteristics of GaInNAs/GaAs quantum well lasers
Semiconductor Science and Technology, 2003
We investigate the effect of doping on the parameters of transparency carrier density and peak gain of GaInNAs/GaAs quantum well lasers emitting at 1.3 µm and compare the results with that of an equivalent nitrogen-free InGaAs/GaAs structure. A significant reduction in the transparency carrier density by p-type doping and an increase in gain by n-type doping are observed for GaInNAs/GaAs contrary to nitrogen-free InGaAs/GaAs. The results are analysed using the band-anti-crossing model for band gap, effective mass and simple approximate expressions for carrier density and optical gain. Our calculations show that doped III-N-V quantum well active layers may have certain benefits to lasers.