Abstract

Semiconductor electrooptic modulators (EOMs) have drawn a significant attention for their large modulation bandwidth and low chirping. One drawback of such devices, however, is a large switching voltage mainly due to the weak linear electrooptic (LEO) effect. In this paper, we report an efficient semiconductor EOM with a switching voltage smaller than 1 V/mm. The phase modulator was fabricated on (100) GaAs/AlGaAs double hetero-structure p-i-n substrate. The rib waveguide is 2 p.m wide at the top, etched down to remove the top p-doped cladding layer covered by an ohmic contact, and 2mm long along [011] as shown in Fig. 1. The optical modulation characteristics were measured at λ=1.3 μm for both the TE and TM modes. From the measured optical intensities, as shown in Fig. 2, one can easily estimate the phase change due to the applied voltage. Considering that the LEO effect occurs only for the TE mode on (011) GaAs/AlGaAs substrate, one can point out the phase change due to the LEO effect from the phase difference between the TE and TM modes. Fig. 2 indicates that the total phase changes are approximately 10 times larger than the phase change due to the LEO effect. Such enhancement turned out to be mainly due to the carrier plasma effect in the i-GaAs layer as will be further elaborated at the conference.

© 2000 IEEE