Enhanced optical bistability from self-heating due to free carrier absorption in substrate removed silicon ring modulators.

We show enhanced optical bistability induced by free carrier absorption from junction doping in substrate-removed silicon ring modulators. Such linear thermal effects dominate the loss in high-speed depletion silicon ring modulators. Optical bistability was observed with about 100 μW of input optical power. We further show that such thermal interactions causes data-dependent ring resonance shifts, and consequently severely degrade the data modulation quality at low speeds. The frequency response of this effect was measured to be about 100~200 kHz.