Abstract

We present, we believe for the first time, an ordered strained superlattice as a quantum well (QW) modulator in the InAs/GaAs material system. This short period strained layer superlattice (SPSLS) can replace ternary strained layered quantum wells¹,² to achieve superior performance. Each QW is composed of the following SPSLS structure: two monolayers of InAs followed by five monolayers of GaAs, repeated five times, followed by another two monolayers of InAs for a well width of 111 Å. This structure confines the heavy holes while the unconfined light holes see a resonant tunneling structure. Only the heavy hole exciton is seen in the absorption spectrum (at 975 nm). Both the field and propagation direction were normal to the growth planes when electroabsorption was measured. A reflection sample (double pass) had a peak ΔR/R of 40% at 5 V. The peak in modulation depth occurred below the exciton peak, contrary to other QCSE modulators,¹,² because the wave functions within the SPSLS-QW lose oscillator strength slowly. Using Δα/α as a figure of merit, at 5 V the SPSLS gave Δα/α = 1.8 compared to 1.2 for strained layered ternary quantum wells.²

© 1991 Optical Society of America