High-frequency modulation without the relaxation oscillation resonance in quantum cascade lasers

Paiella, Roberto; Martini, Rainer; Capasso, Federico; Gmachl, Claire F.; Hwang, Harold Y.; Sivco, Deborah L.; Baillargeon, J. N.; Cho, Alfred Y.; Whittaker, Edward A.; Liu, H. C.

doi:10.1063/1.1411982

Cited by 132 publications

(68 citation statements)

References 11 publications

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“…Despite this, the time-resolved pulse response for the same current, 460 mA, shows no trace of oscillatory response (see Fig. 3), corroborating the findings of others [9], [10]. The test signal for the time trace was a square wave of amplitude 1 mA peak-to-peak and 2.5 ns period (corresponding frequency 400 MHz).…”

Section: Resultssupporting

confidence: 86%

Terahertz quantum cascade laser bandwidth prediction

Agnew

Grier

Taimre

et al. 2015

2015 International Topical Meeting on Microwave Photonics (MWP)

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Abstract-Recent research shows that terahertz quantum cascade lasers are well-suited to high speed free space communication. The results of both theoretical and laboratory work indicate the devices are able to deliver bandwidths in the gigahertz to tens of gigahertz range without the burden of relaxation oscillations found in diode lasers. Using a novel rate equation model we explore the frequency response characteristics of a real device and report on the finding of a strongly peaked bias currentdependent response.Index Terms-Free space communication, terahertz quantum cascade laser, bandwidth

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Section: Resultssupporting

confidence: 86%

Terahertz quantum cascade laser bandwidth prediction

Agnew

Grier

Taimre

et al. 2015

2015 International Topical Meeting on Microwave Photonics (MWP)

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“…4 shows no relaxation oscillation, in accordance with the findings of others. 21 In summary, we have incorporated the temperature and bias-dependence of the carrier lifetimes, injection efficiencies, and gain in a RRE model of a THz QCL and coupled this with a thermal model. This approach enables the THz power, threshold current, and cut-off current to be determined rapidly over the full range of operating temperatures, with no empirical fitting parameters in the RRE model.…”

mentioning

confidence: 99%

Efficient prediction of terahertz quantum cascade laser dynamics from steady-state simulations

Agnew

Grier

Taimre

et al. 2015

Applied Physics Letters

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Terahertz-frequency quantum cascade lasers (THz QCLs) based on bound-to-continuum active regions are difficult to model owing to their large number of quantum states. We present a computationally efficient reduced rate equation (RE) model that reproduces the experimentally observed variation of THz power with respect to drive current and heat-sink temperature. We also present dynamic (time-domain) simulations under a range of drive currents and predict an increase in modulation bandwidth as the current approaches the peak of the light–current curve, as observed experimentally in mid-infrared QCLs. We account for temperature and bias dependence of the carrier lifetimes, gain, and injection efficiency, calculated from a full rate equation model. The temperature dependence of the simulated threshold current, emitted power, and cut-off current are thus all reproduced accurately with only one fitting parameter, the interface roughness, in the full REs. We propose that the model could therefore be used for rapid dynamical simulation of QCL designs.

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“…Since the first demonstration of a QCL in 1994 [1], remarkable advances in device performance have been made. Scientifically and technologically important examples are the development of high-power MBE-and MOVPE-grown QCL operating in CW at room temperature and above [2]- [4], high-speed electrical modulation without relaxation oscillation [5] and observation of Bloch gain in QCLs [6], and the realization of QC structures emitting in the terahertz (THz) range of the spectrum [7], [8]. However, the mechanism of electronic transport across the active and injector regions, which is closely related to the dynamic gain recovery, has not been extensively investigated, though there have been some studies of carrier transport and relaxation processes in nonlasing quantum-well (QW) structures [9]- [12].…”

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confidence: 99%

Time-Resolved Investigations of Electronic Transport Dynamics in Quantum Cascade Lasers Based on Diagonal Lasing Transition

Choi

Diehl

et al. 2009

IEEE J. Quantum Electron.

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Abstract-In this study, the nature of electronic transport in quantum cascade lasers (QCLs) has been extensively investigated using an ultrafast time-resolved, degenerate, pump-probe optical technique. Our investigations enable a comprehensive understanding of the gain recovery dynamics in terms of a coupling of the electronic transport to the oscillating intracavity laser intensity. In QCLs that have a lasing transition diagonal in real space, studies of the near-threshold reveal that the transport of electrons changes bias region from phonon-limited relaxation (tens of picoseconds) below threshold to photon-driven transport via stimulated emission (a few picoseconds) above threshold. The gain recovery dynamics in the photon-driven regime is compared with conventional four-level lasers such as atomic, molecular, and semiconductor interband lasers. The depopulation dynamics out of the lower lasing state is explained using a tight-binding tunneling model and phonon-limited relaxation. For the superlattice relaxation, it is possible to explain the characteristic picosecond transport via dielectric relaxation; Monte Carlo simulations with a simple resistor model are developed, and the Esaki-Tsu model is applied. Subpicosecond dynamics due to carrier heating in the upper subband are isolated and appear to be at most about 10% of the gain compression compared with the contribution of stimulated emission. Finally, the polarization anisotropy in the active waveguide is experimentally shown to be negligible on our pump-probe data, supporting our interpretation of data in terms of gain recovery and transport.

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High-frequency modulation without the relaxation oscillation resonance in quantum cascade lasers

Cited by 132 publications

References 11 publications

Terahertz quantum cascade laser bandwidth prediction

Terahertz quantum cascade laser bandwidth prediction

Efficient prediction of terahertz quantum cascade laser dynamics from steady-state simulations

Time-Resolved Investigations of Electronic Transport Dynamics in Quantum Cascade Lasers Based on Diagonal Lasing Transition

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