Fully integrated 3-bit all-optical analog to digital converter based on photonic crystal semiconductor optical amplifier

•An ultra-low power small footprint integrated 3-bit all optical analog to digital is presented.•Designing 3-bit AO-ADC with no missing code has been made possible using PhC-SOA instead of conventional SOA.•An innovative encoder is proposed to produce binary code at the output.•The structure parameters are optimized by microfluidic infiltration which is a post-fabrication fine tuning method. Integrating a photonic crystal based semiconductor optical amplifier (PhC-SOA) composed of InP/InGaAsP/InP heterostructure with eight PhC based channel drop filters (CDFs) based on an InGaAsP platform, we have designed a fully integrated all-optical 3-bit analog to digital converter (AO-ADC). A probe signal after passing through a 9-µm long PhC-SOA in the presence of an amplitude-modulated Gaussian pulse of 1.422 ps width and maximum energy of 37.2 fJ exhibited a 4.8-nm wavelength shift. The eight appropriately designed PhC-CDFs have coded the chirped signal into eight quantization levels. The numerical results show that the proposed structure can convert analog photonic signals into 3-bit digital output with no missing code at 10Gs/s. The proposed AO-ADC structure with a small footprint of 455 μm2, along with its ultra-low power consumption, can pave the way for the further development of the next-generation integrated photonic chips.