Single-mode optically activated phase modulator on GaAs/GaAlAs compound semiconductor rib waveguides

Abstract

We report on an optically activated phase modulator (OAM) and modulator array on GaAs-GaAlAs compound semiconductor rib waveguides. A rib waveguide device with an optical activation window of 5 μm in diameter was fabricated. Optical activation was produced by using a HeNe 632.8 nm wavelength as the free-carrier generator and a 1.3 μm laser as the signal carrier. A 33% modulation depth was observed and 10−2 index modulation was experimentally confirmed on an OAM working in the phase modulation regime. OAMs working in both phase- and cutoff-modulation regimes were further determined by considering the variation of the waveguide confinement factor. An 8.2 dB modulation depth was observed on an OAM working at the cutoff regime. Furthermore, the activation source for the free-carrier generation is in the mW power region, which significantly reduces the size and cost of all optical switching devices.