High-speed Optical Logic Research Articles

Design of Optically Controlled Reversible NOT Gate Using Micro Ring Resonators

Micro Ring Resonator (MRR) is a successful micro-device with the help of which different types of optical logic gates, logic processors, arithmetic units, etc. can be designed and integrated easily into the modern high-speed communication network. In this article, at first, the author has explained the switching mechanism of MRR and then designed an optically controlled Feynman gate (i.e. reversible controlled-Not gate) using MRRs. The switching mechanism of MRR is reliable and the switching speed of MRR is very fast. The change the resonance condition of MRR can occur when the ring is exposed in the optical pump beam with high intensity. The logic processors using Reversible Logic gates are more acceptable due to their data recovery capability and low power consumption. The designed circuit of optically controlled NOT Gate is testified with the MATLAB simulation results. To fulfil the demand for an ultra-high-speed network, the development of high speed optical logic processors is the primary requisite and this scheme will be very helpful for developing such elements.

Seven-channel all-optical reconfigurable canonical logic units multicasting at 40 Gb/s based on a nonlinearity-enhanced silicon waveguide

All-optical canonical logic unit (CLU) is the basic building block of high-speed optical logic operation and complex optical computing. By utilizing the parallelism of optical signals, multichannel multicasting of all-optical CLUs can expand the capacity of the computing system effectively. Here, we propose and experimentally demonstrate the 40 Gb/s all-optical reconfigurable two-input CLUs generated in seven wavelength channels via four-wave mixing (FWM) in the nonlinearity-enhanced silicon waveguide. By introducing reverse-biased PIN junctions to reduce nonlinear loss, the output power of converted light can be increased over 10 dB. Moreover, pumped by two optical signals and a continuous wave beam, a full set of reconfigurable CLUs is multicasted in seven parallel wavelength channels. All logic signals with error-free performance are realized. Attributing to the rate transparency of FWM and parallel multicasting of logic functions, the proposed scheme offers more flexibility and expandability in future high-speed optical logic processing and complex optical computing.

Designing a Circuit for High-Speed Optical Logic Half Subtractor

In this paper, a high-speed optical subtractor has been designed and simulated. This circuit is based on a photonic crystal structure with silicon rods embracing a circular cross-section in the air platform. This structure was performed based on the photonic band gap. The best performance of this subtractor is in the highly-usable telecommunication wavelength of 1550, laying in the range of the photonic band gap of this structure. To design the circuit, two inputs with optical sources and two outputs have been used for difference and borrow bit. The features of this logic half subtractor encompassed simple structure, small dimensions, and appropriate level of the outputs 1 and 0.

Ultra-contrast ratio optical encoder using photonic crystal waveguide

In recent year, ultra-compact and high-speed optical logic devices are extremely attractive for the scientific community and optical computing. In this paper, 2 × 1 encoder is proposed and designed using two-dimensional photonic crystal based microstructure. This logic device is constructed by point and line defects in a triangular lattice with silicon rod embedded in air host. The encoder performances are analyzed by using Finite Difference Time Domain method. The numerical results reveal that the designed micro device is capable of working accurately for different logic states. The proposed device is operated at 1520 nm, and it provides a high contrast ratio of 25.82 dB, the excellent response time of 0.2833 ps and a bit rate of around 3.52 Tbps. Hence, it is highly suitable for an optical signal processor and photonic integrated circuits.

Room temperature operation of electro-optical bistability in the edge-emitting tunneling-collector transistor laser

Optical bistable devices are fundamental to digital photonics as building blocks of switches, logic gates, and memories in future computer systems. Here, we demonstrate both optical and electrical bistability and capability for switching in a single transistor operated at room temperature. The electro-optical hysteresis is explained by the interaction of electron-hole (e-h) generation and recombination dynamics with the cavity photon modulation in different switching paths. The switch-UP and switch-DOWN threshold voltages are determined by the rate difference of photon generation at the base quantum-well and the photon absorption via intra-cavity photon-assisted tunneling controlled by the collector voltage. Thus, the transistor laser electro-optical bistable switching is programmable with base current and collector voltage, and the basis for high speed optical logic processors.

Monolithic Mid-Infrared Integrated Photonics Using Silicon-on-Epitaxial Barium Titanate Thin Films.

Broadband mid-infrared (mid-IR) photonic circuits that integrate silicon waveguides and epitaxial barium titanate (BTO) thin films are demonstrated using the complementary metal-oxide-semiconductor process. The epitaxial BTO thin films are grown on lanthanum aluminate (LAO) substrates by the pulsed laser deposition technique, wherein a broad infrared transmittance between λ = 2.5 and 7 μm is observed. The optical waveguiding direction is defined by the high-refractive-index amorphous Si (a-Si) ridge structure developed on the BTO layer. Our waveguides show a sharp fundamental mode over the broad mid-IR spectrum, whereas its optical field distribution between the a-Si and BTO layers can be modified by varying the height of the a-Si ridge. With the advantages of broad mid-IR transparency and the intrinsic electro-optic properties, our monolithic Si on a ferroelectric BTO platform will enable tunable mid-IR microphotonics that are desired for high-speed optical logic gates and chip-scale biochemical sensors.

Electro-optical hysteresis and bistability in the ring-cavity tunneling-collector transistor laser

Bistable devices are fundamental to digital electronics as building blocks of switches, logic gates, and memory in computer systems. We demonstrate here transistor lasers exhibiting both electrical and optical hystereses with sharp square-corner current switching and different voltage thresholds in the collector IC–VCE and optical L–VCE family of characteristics. The electro-optical hysteresis is explained by the different switching paths of electron-hole (e-h) and photon interactions involving cavity coherent and incoherent energy states employing intracavity photon-assisted tunneling at the collector junction and spontaneous/stimulated e-h recombination at the base quantum-well. The electro-optical bistability of the transistor laser possesses a unique property of voltage (field) modulation and the basis for high speed optical logic processors.

Optically controlled polarizer using a ladder transition for high speed Stokesmetric Imaging and Quantum Zeno Effect based optical logic

We demonstrate an optically controlled polarizer at ~1323 nm using a ladder transition in a Rb vapor cell. The lower leg of the 5S(1/2),F = 1->5P(1/2),F = 1,2->6S(1/2),F = 1,2 transitions is excited by a Ti:Sapphire laser locked to a saturated absorption signal, representing the control beam. A tunable fiber laser at ~1323 nm is used to excite the upper leg of the transitions, representing the signal beam. When the control beam is linearly polarized, it produces an excitation of the intermediate level with a particular orientation of the angular momentum. Under ideal conditions, this orientation is transparent to the signal beam if it has the same polarization as the control beam and is absorbed when it is polarized orthogonally. We also present numerical simulations of the system using a comprehensive model which incorporates all the relevant Zeeman sub-levels in the system, and identify means to improve the performance of the polarizer. A novel algorithm to compute the evolution of large scale quantum system enabled us to perform this computation, which may have been considered too cumbersome to carry out previously. We describe how such a polarizer may serve as a key component for high-speed Stokesmetric imaging. We also show how such a polarizer, combined with an optically controlled waveplate, recently demonstrated by us, can be used to realize a high speed optical logic gate by making use of the Quantum Zeno Effect. Finally, we describe how such a logic gate can be realized at an ultra-low power level using a tapered nanofiber embedded in a vapor cell.

All-optical high speed logic gates using SOA

In this paper a novel and simple structure of a high speed optical logic gate based on bulk semiconductor optical amplifier (SOA) is presented. The gain dynamic and phase response of bulk SOA using rate equations including the dynamics of carrier heating (CH) and spectral-hole burning (SHB) is investigated numerically. The operation of NOR gate is analyzed by using the presented numerical method, and a NOR gate that can operate up to 1 Tbps is designed. By using the proposed structure, high speed logic gates based on bulk SOA can be realized.