Abstract
We report on the significantly improved linewidth enhancement factor (αH-factor) of 1.3-µm InAs/GaAs quantum dot (QD) lasers by direct Si doping, compared with ones having identical structures but without the Si doping. It is found that the αH-factors for the ground-state and first excited-state at their gain peak positions of the Si-doped QD lasers are 1.48 and 0.63 while those of the undoped QD lasers are 2.07 and 1.07, greatly decreasing by about 28.5% and 41.1%, respectively. Furthermore, theoretical calculation and analysis suggest that direct Si doping would increase the electron quasi-Fermi level in conduction, leading to the increase in population inversion. Meanwhile, the appearance of a built-in electric field caused by the Si doping would accelerate the capture of electrons into QDs and strengthen the confinement effect of electrons, resulting in an increased differential gain.
Highlights
We investigate the αH-factor of the lnAs/GaAs quantum dot (QD) lasers with and without direct Si doping, which was extracted from scitation.org/journal/adv the amplified spontaneous emission (ASE) spectra
By applying a correcting factor to eliminate the influence of the thermal effect, the αH-factors for the GS and the first excited state (ES1) at their gain peak positions of the Si-doped QD lasers are 1.48 and 0.63, while those of the undoped QD lasers are 2.07 and 1.07, greatly decreasing by about 28.5% and 41.1%, respectively
The results show that electron quasi-Fermi level (EF) and f c would increase with the increase in doping concentration, leading to an increased population inversion
Summary
By applying a correcting factor to eliminate the influence of the thermal effect, the αH-factors for the GS and the first excited state (ES1) at their gain peak positions of the Si-doped QD lasers are 1.48 and 0.63, while those of the undoped QD lasers are 2.07 and 1.07, greatly decreasing by about 28.5% and 41.1%, respectively.
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