Open AccessOptimum thickness of GaAs top layer in AlGaAs‐based 850 nm VCSELs for 56 Gb/s PAM‐4 applications
Author(s) -
Yu ShinWook,
Kim SangBae
Publication year - 2021
Publication title -
etri journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.295
H-Index - 46
eISSN - 2233-7326
pISSN - 1225-6463
DOI - 10.4218/etrij.2020-0194
Subject(s) - materials science , laser , optics , saturation (graph theory) , optoelectronics , rate equation , oscillation (cell signaling) , physics , mathematics , chemistry , biochemistry , combinatorics , quantum mechanics , kinetics
We studied the influence of GaAs top‐layer thickness on the small‐signal modulation response and 56 Gb/s four‐level pulse‐amplitude modulation eye quality of 850 nm vertical‐cavity surface‐emitting lasers (VCSELs). We considered the proportionality of the gain‐saturation coefficient to the photon lifetime. The simulation results that employed the transfer‐matrix method and laser rate equations led to the conclusion that the proportionality should be considered for proper explanation of the experimental results. From the obtained optical eyes, we could determine an optimum thickness of the GaAs top layer that rendered the best eye quality of VCSEL. We also compared two results: one result with a fixed gain‐saturation coefficient and the other that considered the proportionality. The former result with the constant gain‐saturation coefficient demonstrated a better eye quality and a wider optimum range of the GaAs top‐layer thickness because the resultant higher damping reduced the relaxation oscillation.