Optical NAND gate

An optical NAND gate which receives a first digital optical input and a second digital optical input and generates therefrom a NAND function digital optical output, comprising:

• a III-V compound semiconductor substrate having a plurality of III-V compound semiconductor layers epitaxially grown thereon;
• a first electroabsorption modulator formed from the plurality of III-V compound semiconductor layers, with the first electroabsorption modulator receiving the first digital optical input;
• a first waveguide photodetector formed from the plurality of III-V compound semiconductor layers to receive the second digital optical input and to generate therefrom a first photocurrent signal which changes an absorption of light in the first electroabsorption modulator and thereby converts the first digital optical input into an output of the first electroabsorption modulator;
• a second waveguide photodetector formed from the plurality of ITT-V compound semiconductor layers to receive the output from the first electroabsorption modulator and to generate therefrom a second photocurrent signal;
• a laser formed from the plurality of III-V compound semiconductor layers to provide a source of continuous light;
• and
• a second electroabsorption modulator formed from the plurality of III-V compound semiconductor layers to receive the continuous light from the laser and to convert the continuous light into the NAND function digital optical output in response to the second photocurrent signal which is electrically connected to vary the absorption of the continuous light being transmitted through the second electroabsorption modulator.

A photonic integrated circuit which generates a NAND function digital optical output from a pair of digital optical inputs, comprising:

• a first pair of optical waveguide devices formed on a substrate, with the first pair of optical waveguide devices comprising a first electroabsorption modulator which is electrically connected in parallel with a first photodetector, with the first electroabsorption modulator receiving a first digital optical input of the pair of digital optical inputs, and with the first photodetector receiving a second digital optical input of the pair of digital optical inputs to generate therefrom a photocurrent signal which changes a reverse-bias voltage on the first electroabsorption modulator to generate a digital optical output of the first electroabsorption modulator;
• and
• a second pair of optical waveguide devices formed on the substrate, with the second pair of optical waveguide devices comprising a second electroabsorption modulator which is electrically connected in series with a second photodetector, with the second electroabsorption modulator receiving an input of continuous light, and with the second photodetector receiving the digital optical output from the first electroabsorption modulator and generating therefrom another photocurrent signal which changes the reverse-bias voltage on the second electroabsorption modulator to modulate the continuous light being transmitted through the second electroabsorption modulator and thereby generate the NAND function digital optical output.