Impact of oxide aperture diameter on optical output power, spectral emission, and bandwidth for 980 nm VCSELs

TL;DR: In this article, the top emitting VCSELs were characterized at room temperature (∼25 °C) using an automated (university-built) wafer mapping system, resulting in two-dimensional colorized maps of several performance attributes of interest including optical output power, threshold current, and maximum power conversion efficiency.

Abstract: We produce experimental 980 nm vertical cavity surface emitting lasers (VCSELs) with a wide range of oxide aperture diameters (o) from ∼2.5 to 15 µm on wafers designed to minimize the epitaxial growth and VCSEL design complexity. The structures are grown in batches of 12, 3-inch diameter wafers in a production metal-organic vapor phase epitaxy machine. We characterize the top emitting VCSELs at room temperature (∼25 °C) – grouped into unit cells with 16 rows and 15 columns—using an automated (university-built) wafer mapping system, resulting in two-dimensional colorized maps of several performance attributes of interest including optical output power, threshold current, and maximum power conversion efficiency. By etching part of the topmost layer of the upper distributed Bragg reflector to decrease the VCSEL optical cavity photon lifetime, we boost the small signal modulation bandwidth (f3dB). The room temperature maximum f3dB is ∼30 GHz for VCSELs with o ∼3 µm and ∼20 GHz for VCSELs with o ∼15 µm.