Fabry-Perot electroabsorption modulators for high-speed free-space optical communication

Retroreflective modulators are key components in free-space optical communication systems between mobile platforms and users. Wide-aperture surface-normal electroabsorption modulators based on GaAs-AlGaAs quantum wells embedded in an asymmetric Fabry-Perot cavity are designed and fabricated with a high yield process on 10-cm wafers. It is shown that the modulator yield and its speed are improved significantly by a pixellated approach in which monolithic modulators are divided into 4-64 pixels. The fabricated 1.5×1.5 cm² devices exhibit contrast ratios of 8 dB at a driving voltage of 8 V and a modulation frequency higher than 10 MHz, which provides low noise and fast data transmission for long distance free-space optical communication.