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US 8,363,990 B1Granted
Optical set-reset latch
AssigneeSandia Corporation
InventorErik J. Skogen
Life of this patent
Estimating the term…
Abstract
An optical set-reset (SR) latch is formed from a first electroabsorption modulator (EAM), a second EAM and a waveguide photodetector (PD) which are arranged in an optical and electrical feedback loop which controls the transmission of light through the first EAM to latch the first EAM in a light-transmissive state in response to a Set light input. A second waveguide PD controls the transmission of light through the second EAM and is used to switch the first EAM to a light-absorptive state in response to a Reset light input provided to the second waveguide PD. The optical SR latch, which may be formed on a III-V compound semiconductor substrate (e.g. an InP or a GaAs substrate) as a photonic integrated circuit (PIC), stores a bit of optical information and has an optical output for the logic state of that bit of information.
Claims25
An optical set-reset (SR) latch, comprising:
- a first electroabsorption modulator which is initially electrically biased in a light-absorptive state wherein little, if any, light which is received into an input of the first electroabsorption modulator is transmitted to an output thereof;
- a second electroabsorption modulator which is optically connected to receive a first portion of the light transmitted through the first electroabsorption modulator with a second portion of the light transmitted through the first electroabsorption modulator being directed to a Q output of the optical SR latch to provide an indication of an optical logic state of the optical SR latch, and with the second electroabsorption modulator being electrically biased in a light-transmissive state wherein a majority of the first light portion received into the input of the second electroabsorption modulator is transmitted to the output thereof;
- a first waveguide photodetector optically connected to receive a Set light input and the first light portion after transmission through the second electroabsorption modulator, with the first waveguide photodetector being electrically connected to the first electroabsorption modulator, and with the first waveguide photodetector, upon detecting the Set light input, generating a photocurrent signal which temporarily changes the electrical biasing of the first electroabsorption modulator and switches the first electroabsorption modulator to the light-transmissive state so that the first light portion transmitted through the second electroabsorption modulator to the first waveguide photodetector increases in intensity to a light level which continues to generate the photocurrent signal after the Set light input diminishes in intensity, thereby latching the first electroabsorption modulator in the light-transmissive state;
- and
- a second waveguide photodetector optically connected to receive a Reset light input, with the second waveguide photodetector being electrically connected to the second electroabsorption modulator, and with the second waveguide photodetector, upon detecting the Reset light input, generating another photocurrent signal which temporarily changes the electrical biasing of the second electroabsorption modulator to switch the second electroabsorption modulator to the light-absorptive state wherein the first light portion transmitted through the second electroabsorption modulator to the first waveguide photodetector diminishes in intensity to a light level wherein the photocurrent signal generated by the first waveguide photodetector is insufficient to maintain the first electroabsorption modulator in the light-transmissive state so that the first electroabsorption modulator switches back to the light-absorptive state.
2 more elements
An optical set-reset (SR) latch, comprising:
- a substrate having a first electroabsorption modulator, a second electroabsorption modulator, a first waveguide photodetector and a second waveguide photodetector formed thereon,
- with the first and second electroabsorption modulators and the first waveguide photodetector being arranged to provide an optical and electrical feedback loop which controls whether the first electroabsorption is in a light-transmissive state or in a light-absorptive state,
- with the light-transmissive state being set by providing a Set light input into the first waveguide photodetector to generate a photocurrent which reduces an electrical bias voltage across the first electroabsorption modulator, and with the first electroabsorption modulator being latched in the light-transmissive state by feedback of a continuous light input through the first and second electroabsorption modulators to the first waveguide photodetector to maintain the photocurrent and the reduced electrical bias voltage across the first electroabsorption modulator, and
- with the light-absorptive state being reset by providing a Reset light input into the second waveguide photodetector to change the electrical bias voltage across the second electroabsorption modulator and thereby reduce the feedback of the continuous light input through the second electroabsorption modulator to the first waveguide photodetector so that the photocurrent generated by the first waveguide photodetector is reduced and the electrical bias voltage across the first electroabsorption modulator is increased to switch the first electroabsorption modulator to the light-absorptive state until such time as another Set light input is provided to the first waveguide photodetector, and
- with a portion of the continuous light input which is transmitted through the first electroabsorption modulator being coupled to an optical output of the optical SR latch to indicate a logic state of the optical SR latch.
2 more elements
Dependencies are inferred from the claim text.