A 40-Gbit/s electro-absorption modulator with a record modulation efficiency (50 GHz/V) enhanced by a novel technique of hybrid integration on the driver IC

We fabricate a compact integrated transmitter, in which an EA modulator is directly mounted on a driver-IC with a chip size of 1.9-mm×2.4-mm and demonstrate 40-Gbit/s operation of this modulator at a low driving voltage (V_p-p=0.7 V). The modulation efficiency, defined by f_{3 dB}/V_p-p´ is a high 50 GHz/V. We further reduced the transmitter´s size by monolithically integrating the EA modulator with a distributed feedback (DFB) laser; tests demonstrated the success of this approach, where we have integrated an optical source, EA modulator, and modulator driver on a single chip.