Extremely wide modulation bandwidth in a low threshold current strained quantum well laser

Abstract

Lasing characteristics of strained quantum well (QW) structures such as InGaAs/AlGaAs on GaAs and InGaAs/InAlAs on InP were analyzed by taking into account the band mixing effect in the valence band. A relaxation oscillation frequency fr, which gives a measure of the upper modulation frequency limit, was found increased three times in a 50 Å In0.9Ga0.1As/In0.52Al0.48As QW structure compared with that in a 50 Å GaAs/Al0.4Ga0.6As QW structure for the undoped case. One of the main factors for this improved frequency bandwidth is attributed to the reduced subband nonparabolicity as well as the reduced valence-band density of state in the strained QW structure. The corresponding lasing threshold current is one order of magnitude smaller than that of the GaAs/AlGaAs QW structure. With a p doping in the QW the fr value increases, and the 3 dB cutoff frequency of about 90 GHz will be expected with an acceptor concentration of 5×1018 cm−3 in the In0.9Ga0.1As/In0.52Al0.48As QW.

High-speed directly-modulated lasers employing photon-photon resonance

“…Moreover, in the LC-RWG gratings there is only a limited interaction between the grating interfaces and the carriers, which leads to more stable devices with better performances and increased reliability. Over the past several decades, substantial efforts have been undertaken to increase the direct modulation bandwidth of lasers through various methods, ranging from engineering the quantum confinement in the active medium [1][2][3][4][5][6] and utilizing injection locking techniques [7][8] to leveraging cavity quantum electrodynamics effects [9][10]. Unfortunately, despite substantial efforts, no significant breakthrough has been made when the direct modulation bandwidth has been linked to the carrier-photon resonance (CPR), largely because the CPR has inherent physical limitations.…”

Effect of indium distribution on optical properties in InGaAs/GaAs quantum wells

“…The strained quantum well (QW) laser has a more beneficial performance than other QW lasers such as lower threshold current density [1] and wider modulation bandwidth [2], and the emission wavelength of the strained QW laser can be adjusted by appropriately changing the strain [3]. With regard to the InGaAs/GaAs material system, In distribution directly decides the performances of devices.…”

A method for evaluating the ground state excitonic band gaps of strained InxGa1−xN/GaN quantum wells

“…[4][5][6][7] Compressively strained QW lasers with large modulation band widths have also been demonstrated. 8,9 It is now a routine to fabricate strained state-of-the-art ͑In,Ga͒As/GaAs QW lasers with very low threshold current densities, high modal gains, large modulation bands, and a robust temperature insensitiveness. [10][11][12][13] Strain plays an equally important role in the wide band gap ͑In,Ga͒N/GaN QW system that is used in the active regions of nitride-based light-emitting diodes and lasers.…”