Gain and linewidth enhancement factor in InAs quantum-dot laser diodes

Newell, T.C.; Bossert, David; Stintz, A.; Fuchs, B.; Malloy, K.J.; Lester, L. F.

doi:10.1109/68.806834

Cited by 262 publications

(115 citation statements)

References 14 publications

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“…. 5 are commonly measured, the measured α-factors in quantum-dot lasers range from near-zero [NEW99a,KON04a,ALE07] to very high values [DAG05], and even "infinite" α [CON07,GRI08a]. Furthermore, a strong dependence on the pump current has been observed [SU05a,JIA12].…”

Section: Amplitude-phase Coupling In Quantum-dot Lasersmentioning

confidence: 99%

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Lingnau

2015

Springer Theses

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In this thesis the dynamics and performance of optoelectronic devices based on semiconductor quantum-dots are investigated.In the first part, the dynamics of quantum-dot lasers under external perturbations is discussed. Using a microscopically based balance equation model that incorporates detailed charge-carrier scattering dynamics and the possibility to describe nonequilibrium between intra-band electronic states, the relaxation oscillations of the quantum-dot laser are investigated. Three qualitatively different dynamic regimes are identified in dependence of the scattering rates -the "constantreservoir" regime for slow scattering, the "overdamped" regime, and the "synchronized" regime for high scattering -characterized by a varying degree of nonequilibrium between the quantum-dot and reservoir states.Important differences to conventional lasers are found in the modulation response and the dynamics in optical injection and feedback setups. Common theoretical models and approaches used to describe these applications are shown to yield inaccurate predictions, especially in the "constant-reservoir" and "overdamped" dynamic regimes. An important consequence is that the amplitude-phase coupling in quantum-dot lasers, commonly described by the α-factor, differs from conventional descriptions due to the desynchronization of gain and refractive index. While the α-factor describes bifurcations of fixed points accurately, it fails in describing dynamic solutions and overestimates the extent of complex dynamics. The observed low sensitivity to optical perturbations in quantum-dot lasers can therefore be attributed partly to the charge-carrier nonequilibrium. Three quantum-dot laser models on different levels of sophistication are presented that can accurately describe the quantum-dot nonequilibrium dynamics.In the second part of the thesis, the performance of quantum-dot semiconductor optical amplifiers is investigated, and two types of applications unique to quantum-dots as active medium are discussed. The ground and excited states of the quantum-dots allow an ultra-broad-band amplification of optical data streams. Amplified signals on the ground-state frequencies are shown to generally exhibit higher quality than on the excited state, due to a lower sensitivity of the groundstate to carrier-density variations. Nevertheless the quantum-dot amplifier is found to allow effective amplification on both frequency ranges. Furthermore, a parameter range is identified that allows for a simultaneous amplification of data signals on the ground and excited state in a counter-propagating setup.The long microscopically polarization dephasing times in quantum-dots are found to enable quantum-coherent interactions on a macroscopic scale at room-temperature. By comparison with experiments, the occurrence of Rabi-oscillations by amplification of ultra-short pulses is demonstrated. Quantum-dot based devices could therefore be used for future applications based on quantum-coherent effects.

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Section: Amplitude-phase Coupling In Quantum-dot Lasersmentioning

confidence: 99%

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Lingnau

2015

Springer Theses

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“…The linewidth enhancement factor characterizes the linewidth broadening and chirp due to fluctuation in the carrier density, which are detri mental sources for high-speed performance. Several methods have been proposed to measure , such as interferometric measurement [1], RF-modulation measurement [2], injec tion-locking method [3], and amplified spontaneous emission (ASE) method [4]. In this letter, a new method for the determi nation of the linewidth enhancement factor of a semiconductor Fabry-Perot (FP) laser is performed by measuring the injection locking range of the laser.…”

mentioning

confidence: 99%

“…Once the band structure is known, the optical gain based on a non-Markovian gain model using a spon taneous-emission transformation method is given in [5], and the induced change in the refractive index due to interband transition is given by (4) where definitions of symbols can be found in [5]. In addition, there is a contribution from the free carrier plasma effect [9] for TE polarization.…”

mentioning

confidence: 99%

Measurement of linewidth enhancement factor of semiconductor lasers using an injection-locking technique

Liu

Jin

Chuang

2001

IEEE Photon. Technol. Lett.

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Abstract-A new method for measuring the linewidth enhance ment factor of semiconductor lasers using the injection-locking technique is presented. This idea is based on the relation between the upper and lower bounds of the locked and unlocked regimes when the detuning of the pump and slave laser is plotted as a function of the injection power. Our results are confirmed with an independent measurement using amplified spontaneous emission (ASE) spectroscopy as well as our theory, which takes account of the realistic quantum-well (QW) band structure and many-body effects. This method provides a new approach to measure the linewidth enhancement factor above laser threshold.Index Terms-Linewidth enhancement factor, optical injection, semiconductor laser.T HE LINEWIDTH enhancement factor ( ) is one of the key parameters for semiconductor lasers. The linewidth enhancement factor characterizes the linewidth broadening and chirp due to fluctuation in the carrier density, which are detri mental sources for high-speed performance. Several methods have been proposed to measure , such as interferometric measurement [1], RF-modulation measurement [2], injec tion-locking method [3], and amplified spontaneous emission (ASE) method [4]. In this letter, a new method for the determi nation of the linewidth enhancement factor of a semiconductor Fabry-Perot (FP) laser is performed by measuring the injection locking range of the laser. In the past, it was proposed that can be obtained by measuring the optical power change of an injection-locked laser [3]. In this method, the injection level should be low to satisfy the assumption for the calculation. At the same time, it is difficult to injection-lock the laser and measure the power variation at low injection levels accurately. Our method does not require any fitting parameters, which would bring uncertainty for different laser systems. Meanwhile, our results are in excellent agreement with our independent measurement based on ASE spectroscopy. Both experimental results are confirmed with our theory, which takes account of realistic band structure with the valence band-mixing effect and many-body effects.In an optical injection-locked laser system, which consists of a master laser (stable laser oscillation) and a test laser, the locking properties of the test laser depend on its linewidth en hancement factor . The locking range is asymmetric when , and the value of the linewidth enhancement factor can be evaluated from this asymmetry. Fig. 1 shows the experimental setup. The test laser is a buried heterostructure FP laser with five compressively strained quantum wells (QWs) made of materials with a lasing wavelength at 1550 nm [5]. The test laser has a threshold current of 11.7 mA, and is operated at a bias current of 25 mA and a heat sink temperature of 25 C. The master lasers are selected from a group of single wavelength DFB lasers with sidemode suppression ratios greater than 40 dB and lasing wavelengths ranging from 1520 nm to 1580 nm. The master laser is mounted on a heat sink...

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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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Gain and linewidth enhancement factor in InAs quantum-dot laser diodes

Cited by 262 publications

References 14 publications

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Measurement of linewidth enhancement factor of semiconductor lasers using an injection-locking technique

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

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