The silicon optical modulator is a key element in the advancement to meet the continuous demand on larger capacity of
data transmission through optical interconnects, where the transmitted signal is required to have very low loss and large
bandwidth. We present the experimental results of an all-silicon optical modulator based on carrier depletion in a lateral
PIPIN diode. By embedding a p-doped slit in the intrinsic region of the PIN diode, the best compromise between
effective index variation and optical loss in the middle of the waveguide is obtained. The PIPIN diode design guarantees
a reduction of optical loss because large part of the waveguide is left unintentionally doped. Additionally, self-aligned
fabrication was used to have an exact alignment of the active region, and to guarantee maximum modulation efficiency.
At 40 Gb/s, the modulator delivered a 6.6 dB extinction ratio, with a 6 dB insertion loss at the operation point.
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