High-speed optical modulation with GaAs/GaAlAs quantum wells in a <i>p</i>-<i>i</i>-<i>n</i> diode structure

TLDR

The authors propose and demonstrate a new high‑speed optical modulator. The modulator operates by applying a perpendicular electric field across 4‑µm GaAs/GaAlAs multiple quantum wells in a p‑i‑n diode, altering carrier confinement energies. The device achieves nearly a two‑fold drop in transmission at 857 nm under 8‑V reverse bias and switches in 2.8 ns, limited only by RC and instrumentation, suggesting even faster intrinsic performance.

Abstract

A new type of high-speed optical modulator is proposed and demonstrated. An electric field is applied perpendicular to GaAs/GaAlAs multiple quantum well layers using a ‘‘p-i-n’’ diode doping structure of 4-μm total thickness. The optical absorption edge, which is particularly abrupt because of exciton resonances, shifts to longer wavelengths with increasing field giving almost a factor of 2 reduction in transmission at 857 nm with an 8-V reverse bias. The shifts are ascribed to changes in carrier confinement energies in the wells. The observed switching time of 2.8 ns is attributed to RC time constant and instrumental limitations only, and fundamental limits may be much faster.