Coupled GaAs/AlGaAs quantum-well electroabsorption modulators for low-electric-field optical modulation

Debbar, Nacer; Hong, Songcheol; Singh, Jasprit; Bhattacharya, P.; Sahai, R.

doi:10.1063/1.342554

Cited by 47 publications

(13 citation statements)

References 12 publications

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“…On the other hand, in coupled quantum wells and superlattices the wave functions can become strongly distorted with increasing applied field, leading to stronger electric field dependence of subband energies and oscillator strengths. 14,15 Furthermore, introducing an asymmetry between the two wells of the structure enhances the separation of the electron and hole wave functions down to zero field, leading to a linear ͑Pockels͒ electro-optic effect that can exceed quadratic contributions at sufficiently low fields.…”

Section: Introductionmentioning

confidence: 99%

Linear electroabsorption in semi-insulating GaAs/AlGaAs asymmetric double quantum wells

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Carrascosa

Agulló‐López

et al. 1999

Journal of Applied Physics

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Electroabsorption has been investigated in semi-insulating asymmetric GaAs/AlGaAs double quantum wells presenting high linear Stark responses, adequate for photorefractive applications. We have used the envelope function approximation to calculate the linear Stark shifts of the energy levels and select a suitable structure for the experimental study. The experimental data indicate that the response to the applied field critically depends on a complicated interplay of effects that compete or cooperate to suppress or enhance the electroabsorption. For positive field polarity, the competing contributions of the overlapping e1 -hh1 and e1 -hh2 transitions partially cancel the electroabsorption despite large linear Stark shifts. On the other hand, small negative fields induce large electroabsorption because the Stark shifts of the two transitions have opposite signs.

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Section: Introductionmentioning

confidence: 99%

Linear electroabsorption in semi-insulating GaAs/AlGaAs asymmetric double quantum wells

Aguilar

Carrascosa

Agulló‐López

et al. 1999

Journal of Applied Physics

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“…The absorber MQW placement in the top DBR coincides with an antinode of the optical standing wave, thereby maximizing efficiency of the absorption process. We chose to use a coupled-QW architecture to maximize the electric field dependence of exciton absorption wavelength [8]. The distance from the active region is determined so that maximum absorption will not shut off the laser, and maximum modulation depth is obtained.…”

Section: Device Descriptionmentioning

confidence: 99%

Modulation properties of VCSEL with intracavity modulator

et al. 2007

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We have studied the modulation properties of VCSEL with intracavity multiple quantum well (MQW) electroabsorption modulator integrated into the top distributed Bragg reflector (DBR) [1]. Small signal analysis of rate equations for loss modulation shows an intrinsic high-frequency roll-off slope of 1/ω instead of 1/ω 2 in directly modulated laser diodes, and consequently bandwidths in excess of 40 GHz are obtainable with this configuration [2]. Possible limiting factors to high bandwidth were examined by fitting high frequency characteristics to a multi-pole transfer function, and include RC delay and carrier drift-limited time of flight (TOF) in the modulator intrinsic region. Intracavity loss modulation shows a strong (+20dB) relaxation oscillation resonant feature in both theory and experiment. As demonstrated, this feature can be significantly reduced in amplitude using parasitics. We have extracted relative contribution of TOF and parasitic capacitance by varying the modulator intrinsic region width (105 and 210 nm) and lateral size of the modulator (18 and 12µm). It was estimated that the small size modulator exhibits parasitics ƒ -3dB at 8GHz. To estimate the carrier TOF contribution to bandwidth limits, low temperature growth of a 210 nm absorber i-region and MQW was employed to reduce photogenerated carrier lifetime. Bandwidth limitations were found to be mostly due to diode and metallization capacitances, in addition to one pole set by the optoelectronic resonance frequency. We have used p-modulation doping of the gain region to increase the relaxation frequency. Pronounced active Q-switching was observed, yielding pulse widths of 40 ps at a 4 GHz rate.

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“…Even though some studies of interwell coupling in coupled systems have been reported, most of them have been done on double QW structures without involving DMS's ͑i.e., without the advantage of continuous tuning͒; [20][21][22][23][24][25] and, more importantly, these studies focused primarily on the dependence of coupling strength on the properties of the separating barriers ͑i.e., on their width and height͒. 26,27 It is obvious that the strength of the coupling between the wells is determined not only by the barrier properties, but also by the relative alignment of the wells themselves ͑i.e., whether or not the system is in a resonant con-dition͒.…”

Section: Introductionmentioning

confidence: 99%

Magnetic-field-induced substructures in multiple quantum wells consisting of magnetic and nonmagnetic semiconductor layers

et al. 2000

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We have investigated multiple quantum well systems consisting of diluted magnetic (Zn 1ϪxϪy Cd x Mn y Se) and nonmagnetic (Zn 1Ϫx Cd x Se) semiconductor wells, separated by nonmagnetic ZnSe barriers. By focusing on interband transitions involving the lowest multiplet of states ͑i.e., the ground state split by interwell interactions͒, we were able to study the details of the coupling between the wells. The strongest interaction between the states of each well occurs when the wells are identical ͑i.e., when they are in a resonant condition͒. The coupling between the wells is dramatically reduced in the presence of an external magnetic field, which can change the depth of diluted magnetic semiconductor ͑DMS͒ wells relative to the non-DMS wells via the large Zeeman splitting that occurs in the DMS layers. As soon as the depth of the wells becomes unequal, the multiple quantum well system subdivides into separate subsystems consisting of groups of equal ͑resonant͒ wells, one associated with non-DMS wells, and the other with DMS wells. This is clearly evident both from theoretical investigation and from the observed magnetic-field dependence of the absorption lines associated with the ground-state multiplet.

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Coupled GaAs/AlGaAs quantum-well electroabsorption modulators for low-electric-field optical modulation

Cited by 47 publications

References 12 publications

Linear electroabsorption in semi-insulating GaAs/AlGaAs asymmetric double quantum wells

Linear electroabsorption in semi-insulating GaAs/AlGaAs asymmetric double quantum wells

Modulation properties of VCSEL with intracavity modulator

Magnetic-field-induced substructures in multiple quantum wells consisting of magnetic and nonmagnetic semiconductor layers

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