Electroabsorption modulators operating at 1.3 μm on GaAs substrates

Abstract

This paper describes the growth and device performance of electroabsorption modulators on GaAs substrates operating near 1.3 μm, the dispersion minimum for silica fibres. The key to the successful molecular beam epitaxial (MBE) growth of these devices was the incorporation of a linearly-graded buffer layer beneath the InGaAs/AlGaAs multi-quantum-well active layer. Both transmission and reflection modulators are produced. For transmission devices, larger modulation is achieved when the buffer is graded more slowly: The maximum modulation reported was 22% for ΔT/T _O corresponding to a 0.86 dB contrast ratio with an insertion loss of roughly 5 dB at 1.34 μm. Antireflection coating a transmission modulator yields a reasonable reflection modulator. However, improved performance is reported for a reflection modulator using a novel technique of integrating the bottom quarter-wave mirror into a buffer with linearly-graded In composition. At 1.33 μm, a normally-off reflection modulator with an integrated mirror exhibited a ΔR/R _O of 73%, a constrast ratio of 2.38 dB, and an insertion loss of 4 dB.