Photonic Logic Circuits Research Articles

A neural networks approach for designing compact all-optical photonic crystal based AND logic gate

Abstract This paper introduces a new method for creating an all-optical AND gate by utilizing a two-dimensional photonic crystal configuration for the first time. This gate design is intended for applications in optical computing and all-optical logic, offering the potential for rapid computation and parallel processing. The described gate is characterized by its compact dimensions and comprises two inputs and a single output. The high and low logic states are defined based on power values, where logic 0 corresponds to low power and logic 1 corresponds to high power emitted from the light source. To enhance the design process, artificial neural networks (ANNs) are utilized. ANNs offer a powerful tool for optimizing and fine-tuning the photonic crystal structure parameters to achieve the desired logic functionality. With the help of the applied ANNs, the design process is eased and high performance is achieved for the proposed photonic crystal structure. By integrating ANNs into the design process, this research opens up new possibilities for advancing the field of photonic logic circuits. Combining photonic crystals and ANN optimization provides a powerful approach to designing complex and efficient optical computing systems. The results show that the obtained power values are high for 1 logic state and low for the 0 logic state, which verifies the AND gate accuracy table. The achieved accurate results verify the validity of the proposed approach for achieving precise and reliable all-optical logic operations.

Elastic Gallium Phosphide Nanowire Optical Waveguides-Versatile Subwavelength Platform for Integrated Photonics.

Emerging technologies for integrated optical circuits demand novel approaches and materials. This includes a search for nanoscale waveguides that should satisfy criteria of high optical density, small cross-section, technological feasibility and structural perfection. All these criteria are met with self-assembled gallium phosphide (GaP) epitaxial nanowires. In this work, the effects of the nanowire geometry on their waveguiding properties are studied both experimentally and numerically. Cut-off wavelength dependence on the nanowire diameter is analyzed to demonstrate the pathways for fabrication of low-loss and subwavelength cross-section waveguides for visible and near-infrared (IR) ranges. Probing the waveguides with a supercontinuum laser unveils the filtering properties of the nanowires due to their resonant action. The nanowires exhibit perfect elasticity allowing fabrication of curved waveguides. It is demonstrated that for the nanowire diameters exceeding the cut-off value, the bending does not sufficiently reduce the field confinement promoting applicability of the approach for the development of nanoscale waveguides with a preassigned geometry. Optical X-coupler made of two GaP nanowires allowing for spectral separation of the signal is fabricated. The results of this work open new ways for the utilization of GaP nanowires as elements of advanced photonic logic circuits and nanoscale interferometers.

All-optical computing circuits half-subtractor and comparator based on soliton interactions

The speed limitations of electronic processors have created a demand for a high bandwidth and ultra-fast computing circuits. By replacing the electric logic gates with photonic ones, a high bandwidth and fast photonic microprocessor will be achieved which will overcome the speed limitations of electronic circuits. Digital photonic logic circuits are key elements in the next generation optical computers. In this paper, all-optical logical half-subtractor and digital comparator are designed based on spatial optical solitons. These computational gates are designed simply with repulsive and attractive interactions of three inphase and out of phase spatial optical solitons in a bulky nonlinear Kerr medium. With tuning the phase input solitons and exploiting inphase and out of phase soliton interactions a high functional circuit with broad operational bandwidth, high switching speed and high contrast ratio between ON/OFF states is achieved by a simple structure.

Al3+‐Morpholine‐appended Anthracene Ensemble as a Dual Photonic Switch for H2PO4− and CN− Ions and its Biological Applications

A highly selective Al3+‐morpholine anthracene (1•Al 3+) chelate was designed as a novel fluorescent photonic switch for H2PO4− and CN− ions. The in situ‐generated Al3+ chelate could be used to detect H2PO4− ions only in the absence of CN− ions. In contrast, CN− ions effectively extruded Al3+ from the chelate, resulting in the regeneration of probe 1 with a concomitant revival of PET, resulting in a turn‐off response. By exploiting the complexation‐ and decomplexation‐aided off–on switching system through the sequential addition of Al3+ followed by H2PO4− or CN−, combinational photonic logic circuits, as well as image‐guided fluorogenic tracking, was demonstrated.

WSe2/GeSe heterojunction photodiode with giant gate tunability

The van der Waals integration of atomically thin two-dimensional (2D) materials can enable a new generation of tunable optoelectronic devices, in which the photocarrier generation, separation and extraction can be modulated by an external gate potential. However, studies to date only show a limited modulation due to non-ideal band alignment and the lack independent modulation of distinct 2D layers in the van der Waals heterojunction. Here report the construction of a WSe2/GeSe heterojunction photodiode with type-II band alignment, in which the value of the conduction band and valence band edge in WSe2 is approximately equal to that of GeSe. What's more, the Fermi level of GeSe remains relative stationary and that of WSe2 can be modulated across the entire band gap by an external gate-voltage, thus rendering widely tunable open-circuit voltages from positive (+ 0.7 V) to negative (− 0.1 V). We further show the photoresponsivity can be modulated by the gate-voltage with a factor of 105, which is similar to the current switching ratio in traditional field-effect transistors, opening up exciting potential for photonic logic circuits.

Fluorescence Resonance Energy Transfer-Based Photonic Circuits Using Single-Stranded Tile Self-Assembly and DNA Strand Displacement.

Structural DNA nanotechnology has great potential in the fabrication of complicated nanostructures and devices capable of bio-sensing and logic function. A variety of nanostructures with desired shapes have been created in the past few decades. But the application of nanostructures remains to be fully studied. Here, we present a novel biological information processing system constructed on a self-assembled, spatially addressable single-stranded tile (SST) nanostructure as DNA nano-manipulation platform that created by SST self-assembly technology. Utilizing DNA strand displacement technology, the fluorescent dye that is pre-assembled in the nano-manipulation platform is transferred from the original position to the destination, which can achieve photonic logic circuits by FRET signal cascades, including logic AND, OR, and NOT gates. And this transfer process is successfully validated by visual DSD software. The transfer process proposed in this study may provide a novel method to design complicated biological information processing system constructed on a SST nanostructure, and can be further used to develop intelligent delivery of drug molecules in vivo.

Model reduction of cavity nonlinear optics for photonic logic: a quasi-principal components approach

Kerr nonlinear cavities displaying optical thresholding have been proposed for the realization of ultra-low power photonic logic gates. In the ultra-low photon number regime, corresponding to energy levels in the attojoule scale, quantum input–output models become important to study the effect of unavoidable quantum fluctuations on the performance of such logic gates. However, being a quantum anharmonic oscillator, a Kerr-cavity has an infinite dimensional Hilbert space spanned by the Fock states of the oscillator. This poses a challenge to simulate and analyze photonic logic gates and circuits composed of multiple Kerr nonlinearities. For simulation, the Hilbert of the oscillator is typically truncated to the span of only a finite number of Fock states. This paper develops a quasi-principal components approach to identify important subspaces of a Kerr-cavity Hilbert space and exploits it to construct an approximate reduced model of the Kerr-cavity on a smaller Hilbert space. Using this approach, we find a reduced dimension model with a Hilbert space dimension of 15 that can closely match the magnitudes of the mean transmitted and reflected output fields of a conventional truncated Fock state model of dimension 75, when driven by an input coherent field that switches between two levels. For the same input, the reduced model also closely matches the magnitudes of the mean output fields of Kerr-cavity-based AND and NOT gates and a NAND latch obtained from simulation of the full 75 dimension model.

Electrically pumped InGaAsP-InP microring optical amplifiers and lasers with surface passivation

Vertically coupled electrically pumped InGaAsP microring optical amplifiers providing gain at 1550 nm are demonstrated. The microrings provide up to 10 dB of gain at the through-port in pulsed mode. The bias current is used to control the loss in the ring and, hence, the region of operation (under-coupled, critically coupled, transparency, and gain). Sulfur passivation is used to reduce carrier loss due to surface recombination in the active region. The amplifiers are designed for application in cascaded microring optical logic gates in photonic logic circuits.

Photonic logic NOR gate based on two symmetric microring resonators

We demonstrate an all-optical NOR logic gate based on symmetric GaAs-AlGaAs microring resonators whose resonances are closely matched. Two input pump data streams are tuned close to one resonance of the symmetric microrings to switch a probe beam tuned to another resonance by two-photon absorption. The switching energy of the gate is 20 pJ/pulse, and the switching window is 40 ps, limited by the carrier lifetime. The use of two rings provides for better cascading in photonic logic circuits because of the higher number of available ports.