Novel monolithic waveguide-based smart pixel for high-contrast, high-gain, and high-speed optical switching

Abstract

We present results on optical switching of a novel monolithic waveguide-based smart pixel. In this smart pixel two surface-normal optical input beams control an optical output beam propagating in-plane through a waveguide modulator. For the operation only DC biases are required. The optical front end of our waveguide-based smart pixel consists of a specially designed n-i-p photoconductive detector in series with a reference n-i-p photodiode. Together, both devices are forming a digital opto-electronic switch, which is directly controlling the waveguide modulator. All components are based on the Franz-Keldysh effect. For a first demonstration of our monolithic waveguide-based smart pixel all components have been processed from the same GaAs/AlGaAs double hetero n-i-p structure grown by MBE on a semi-insulating GaAs substrate. With a non-optimized sample design we obtain an output contrast ratio of 17 dB and an optical gain in excess of 320. The optical input energy is estimated to be 2.6 pJ (detector area 20 X 20 micrometers 2 ). In this case the wavelength of the input beams was 783 nm, while the waveguide modulator was operated at 910 nm. An evaluation of the switching dynamics indicates that high-speed operation in excess of 400 Mbit/s can be achieved. This waveguide-based smart pixel could for example be used in optical routing networks.