Inhomogeneous line broadening and the threshold current density of a semiconductor quantum dot laser

Asryan, Levon V.; Suris, R. A.

doi:10.1088/0268-1242/11/4/017

Cited by 305 publications

(174 citation statements)

References 21 publications

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“…Assuming a spontaneous emission rate much smaller than the capture and thermal escape processes ͑i.e., B e,h , C e,h ӷ 1͒, a stationary solution for the carrier dynamical evolution is obtained by enforcing the detailed balance condition J e,h g,e =0. 18 Inserting a quasiequilibrium Fermi distribution leads to the Kramer relation 19 linking the capture B e,h and the escape C e,h rates C e,h = B e,h exp͑− ⌬E e,h /k B T͒, ͑7͒…”

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confidence: 99%

Electron-hole asymmetry and two-state lasing in quantum dot lasers

Viktorov

Mandel

Tanguy

et al. 2005

Applied Physics Letters

101

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We study the decrease of the ground-state output with increasing current in two-state quantum dot lasing. We show that the asymmetry in the thermal population redistribution breaks the symmetric dynamical evolution of the electron-hole pairs. This fully explains the transition from two-state to single-state lasing observed experimentally. The model also reproduces the temperature dependence of the two-state lasing. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1995947͔Laser devices based on self-assembled quantum dots are a promising source of new physics. 1 The three-dimensional ͑3D͒ confinement of the carriers induces a discrete density of states that implies, for instance, a reduction of the threshold current, 2 a low chirp, a weak temperature dependence, 3 and a reduced sensitivity to optical feedback 4 at telecom wavelengths on GaAs substrates. The recombination of groundstate ͑GS͒ electrons and holes leads to GS lasing but recombination of excited-states ͑ES͒ electrons and holes can also lead to lasing at lower wavelengths. The occurrence of a secondary threshold, involving a second electron-hole pair of levels, was predicted for a sufficiently high bias. 5 Increasing the current further, the ES will eventually become the only surviving line at the expense of the GS transition. 6-9 For injection rates exceeding the second threshold, theory only predicts up to now that the GS intensity becomes a constant while experiments display a reduction down to zero of the GS emission. The aim of this Letter is to analyze both experimentally and theoretically this behavior.The self-organized quantum dot ͑QD͒ active region heterostructure consisted of six InGaAs QD layers embedded in quantum well using dots in a well ͑DWELL͒ technology. 10 Single transverse mode ridge waveguide lasers were fabricated with lengths of 750 m, 1 mm, 1.5 mm, and 2 mm, ridge widths ranging from 3 to 5 m, and a depth of 0.9 m. Both facets were left uncoated. These devices were mounted epitaxial side up on Peltier-controlled copper heat sinks. While long devices emitted in the GS near 1310 nm, 1-mm-long devices emitted first in the GS but then also in the ES ͑1240 nm͒. The shortest devices emitted in the first excited state for all currents. The light-current curves, characteristic of a 1-mm-device obtained in both cw and pulsed regimes, are shown in Fig. 1. In both cases, as the injection current increases, there is a current range where the power in GS decreased while the power state in ES increased as previously observed. [6][7][8][9] It is also worth to note that the differential efficiency is larger for the ES, as shown on Fig. 1, highlighting its increased density of states. Operation in the pulsed regime is necessary to remove the role of thermal effects. Figure 1 corresponds to a pulse width of 100 ns duration with a repetition rate of 100 kHz. We verified that the behavior is similar with pulse widths down to 6 ns. The qualitative invariance of the dynamical response with respect to the pulse duration indicates that Joule heati...

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confidence: 99%

Electron-hole asymmetry and two-state lasing in quantum dot lasers

Viktorov

Mandel

Tanguy

et al. 2005

Applied Physics Letters

101

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“…(3) and (4), v g is the group velocity of light, g max 1 is the maximum modal gain of ground-state lasing, 22 b ¼ (1/L) ln(1/R) is the mirror loss, and R is the facet reflectivity.…”

Section: Rate Equations Modelmentioning

confidence: 99%

“…(3)] for spontaneous radiative recombination in the OCL and QDs, since this process is bimolecular. 22 We focus here on the effects of carrier capture into QDs and intradot relaxation on the lower-(ground-) state lasing, and, for this reason, we do not consider the stimulated emission via the upper (excited) state in QDs. To rule out the stimulated emission via the excited state in QDs, we set the maximum modal gain via excited-state transitions lower than the mirror loss b.…”

Section: Rate Equations Modelmentioning

confidence: 99%

Direct and indirect capture of carriers into the lasing ground state and the light-current characteristic of quantum dot lasers

Asryan

2014

Journal of Applied Physics

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Articles you may be interested inEffect of excited states on the ground-state modulation bandwidth in quantum dot lasers Appl. Phys. Lett. 102, 191102 (2013) We calculate the light-current characteristic (LCC) of a quantum dot (QD) laser under the conditions of both direct and indirect capture of carriers from the optical confinement layer into the lasing ground state in QDs. We show that direct capture is a dominant process determining the ground-state LCC. Only when direct capture is slow, the role of indirect capture (capture into the QD excited state and subsequent intradot relaxation to the ground state) becomes important. V C 2014 AIP Publishing LLC.

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“…where is the cross-section of carrier capture into a QD, is the carrier thermal velocity, is the spontaneous radiative lifetime in a QD given by (8) in [29], is the light velocity in vacuum, is the group index of the dispersive OCL material, is the surface density of QDs, is the QD layer area (the cross-section of the junction), is the QD layer width (the lateral size of the device), is the QD layer length (the cavity length), is the maximum (saturation) value of the modal gain spectrum peak (see [29] and (41) in [30]), is the number of photons in the lasing mode, is the OCL thickness, is the radiative constant for the OCL (given by (10) in [29]), is the injection-current density, is the mirror loss, is the facet reflectivity, and is the modal internal loss [see assumption 6) above].…”

Section: B Rate Equationsmentioning

confidence: 99%

Internal efficiency of semiconductor lasers with a quantum-confined active region

Asryan

Luryi

Suris

2003

IEEE J. Quantum Electron.

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Abstract-We discuss in detail a new mechanism of nonlinearity of the light-current characteristic (LCC) in heterostructure lasers with reduced-dimensionality active regions, such as quantum wells (QWs), quantum wires (QWRs), and quantum dots (QDs). It arises from: 1) noninstantaneous carrier capture into the quantum-confined active region and 2) nonlinear (in the carrier density) recombination rate outside the active region. Because of 1), the carrier density outside the active region rises with injection current, even above threshold, and because of 2), the useful fraction of current (that ends up as output light) decreases. We derive a universal closed-form expression for the internal differential quantum efficiency int that holds true for QD, QWR, and QW lasers. This expression directly relates the power and threshold characteristics. The key parameter, controlling int and limiting both the output power and the LCC linearity, is the ratio of the threshold values of the recombination current outside the active region to the carrier capture current into the active region. Analysis of the LCC shape is shown to provide a method for revealing the dominant recombination channel outside the active region. A critical dependence of the power characteristics on the laser structure parameters is revealed. While the new mechanism and our formal expressions describing it are universal, we illustrate it by detailed exemplary calculations specific to QD lasers. These calculations suggest a clear path for improvement of their power characteristics. In properly optimized QD lasers, the LCC is linear and the internal quantum efficiency is close to unity up to very high injection-current densities (15 kA/cm 2 ). Output powers in excess of 10 W at int higher than 95% are shown to be attainable in broad-area devices. Our results indicate that QD lasers may possess an advantage for high-power applications.Index Terms-Quantum dots (QDs), quantum wells (QWs), quantum wires (QWRs), semiconductor heterojunctions, semiconductor lasers.

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Inhomogeneous line broadening and the threshold current density of a semiconductor quantum dot laser

Cited by 305 publications

References 21 publications

Electron-hole asymmetry and two-state lasing in quantum dot lasers

Electron-hole asymmetry and two-state lasing in quantum dot lasers

Direct and indirect capture of carriers into the lasing ground state and the light-current characteristic of quantum dot lasers

Internal efficiency of semiconductor lasers with a quantum-confined active region

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