Design of an ultrafast all-optical NOR logic gate based on Mach-Zehnder interferometer using quantum-dot SOA

This paper proposes a design for all-optical NOR logic gate, based on Mach-Zehnder interferometer (MZI) using quantum-dot semiconductor optical amplifier (QD-SOA). In this regard, a theoretical model for an ultrafast all-optical signal processor is developed using QD-SOA to achieve high bit rate operation. We have demonstrated the NOR gate operation in two cases of with and without an optical control pulse. Simulations have been carried out at data bit rates 160 Gb/s, 200 Gb/s, and 250 Gb/s for the case that control pulse is not applied, and also at data bit rates 1 Tb/s and 2 Tb/s in presence of control pulse which leads to improvement of gain recovery time and ultrafast NOR logic operation. In addition, quality factors of the output signals in presence and without the control pulse at different bit rates with different bias currents have been investigated for pseudo-random binary sequence (PRBS) of word length 2⁸–1.     

Cascadable all-optical inverter based on a nonlinear vertical-cavity semiconductor optical amplifier

We report, for the first time to our knowledge, the operation of a cascadable, low-optical-switching-power(~10 microW) small-area (~100 microm(2)) high-speed (80 ps fall time) all-optical inverter. This inverter employs cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics of an electrically pumped vertical-cavity semiconductor optical amplifier (VCSOA). The measured transfer characteristics of such an optical inverter resemble those of standard electronic metal-oxide semiconductor field-effect transistor-based inverters exhibiting high noise margin and high extinction ratio (~9.3 dB), making VCSOAs an ideal building block for all-optical logic and memory.     

Reconfigurable all-optical logic gate using four-wave mixing (FWM) in HNLF for NRZ-PolSK signal

We demonstrate a reconfigurable all-optical logic gate for NRZ-PolSK signal based on FWM in a highly nonlinear fiber at 10 Gb/s. Half subtracter, XOR, AB?, āB or XNOR, AND, and NOR logic gates can be implemented simultaneously. The input power for the HNLF is optimized to be as low as about 15.2 dBm and the high Q factors above 8 dB for eye diagrams are achieved. Experimental results show Q factors of AB?, āB, AND, and NOR were higher than those of XOR, and XNOR. Error-free operation is achieved experimentally for 10 Gb/s 2⁷-1 pseudorandom bit sequence (PRBS) data. Power penalties for the logic gate are less than 3 dB. Simulation analysis about the wavelength characteristic for all logic gates is given and it predicts that the reconfigurable logic gate can realize error-free operation when the wavelength separation is less than 5 nm.     

1 Tb/s high quality factor NOR gate based on quantum-dot semiconductor optical amplifier

The performance of all-optical logic gate NOR has been simulated. NOR operation is realized by using Mach–Zehnder interferometer utilizing semiconductor optical amplifier (SOA) with quantum-dot (QD) active region. Nonlinear dynamics including carrier heating and spectral hole-burning in the QD–SOA are taken into account together with the rate equations in order to realize the all-optical logic NOR operation. The study is carried out when the effect of amplified spontaneous emission is taken into account in the simulation analysis. Results show that the NOR operation is capable of operating at a data speed of 1 Tb/s with high output quality factor (Q-factor). The dependence of the output $Q$ -factor on QD–SOA parameters is also investigated and discussed.     

Parity checking and generating circuit with semiconductor optical amplifier in all-optical domain

In this paper, an all-optical parity checker and parity generator circuit is proposed in which SOA-MZI configuration is used to implement the XOR logic gate. This performance monitoring logic device is simulated at ultra high speed i.e. 120 GHz. Two logic circuits are proposed for parity generator, in one design inverter used to generate parity bit is implemented by the same additional XOR gate as inverter while in 2nd design inverter is implemented using XGM in SOA and thus number of SOA in 2nd design is reduced. ER ratio achieved in 1st case is 9.28 with maximum Q factor 73.39 and minimum BER 0 while in 2nd design it is 9.35 with maximum Q factor 8.41 and minimum BER 1.93e−17. ER ratio achieved in parity checker circuit is 32.54 with maximum Q factor 77.76 and minimum BER 0.     

Demonstration of nanophotonic NOT gate using near-field optically coupled quantum dots

We propose and demonstrate the operation of a nanometric optical NOT gate using CuCl quantum dots coupled via an optical near-field interaction. The device was smaller than 20 nm and its repeated operation was verified. The operating energy of this device was much lower than that of a conventional photonic device. We also introduce all-optical NAND and NOR gates using coupled quantum dots. Toward an actual nanophotonic device, we discuss the possibility of coupled InAlAs quantum dots. A double layer of InAlAs quantum dots for nanophotonic device operation was prepared using molecular beam epitaxial growth. We obtained a near-field spectroscopy signal, indicating that the InAlAs quantum dots coupled with the optical near field acted as a NOT gate. The experimental results show that the sample has great potential as an actual nanophotonic device. PACS 78.67.Hc; 07.79.Fc; 42.79.Ta     

Proposal for all-optical NOR gate using single quantum-dot semiconductor optical amplifier-based Mach–Zehnder interferometer

The feasibility of realizing an all-optical NOR gate for 160 Gb/s return-to-zero data pulses using a single quantum-dot semiconductor optical amplifier (QD-SOA)-based Mach–Zehnder interferometer is theoretically investigated and demonstrated. The proposed scheme exploits a modified Fredkin gate driven not only by the pair of data streams between which the Boolean NOR function is executed but by the complement of one of these signals as well. A numerical simulation is conducted to evaluate the performance of the scheme against the extinction ratio and find for which choice of the critical data signals and QD-SOAs parameters this metric becomes acceptable. Provided that the specified requirements are satisfied, which is technologically feasible, the NOR gate can be realized for data signals of the same wavelength both with logical correctness and high quality.     

NOR and NAND gates using two photon absorption in silicon wire waveguide

Ultrafast all-optical NOR gate based on two photon absorption (2PA) process in SOI waveguide is already established. We have designed NAND gate also based on this process with a novel waveguide coupler structure. Power attenuation due to 2PA process and the working of these gates is developed with FDTD simulation. Dominant 2PA process is incorporated in FDTD update equations and it is shown that the influence of high intensity pump pulses on a different frequency continuous probe beam can be utilized to form NOR as well as NAND gates.     

All optical switching in henna thin film

The optical nonlinearity in henna (Lawson (2- hydroxyl-1,4 naphthoquinone) film was utilized to demonstrate all optical switching. The nonlinear absorption of the henna film was calculated by measuring the transmission of the laser beam (λ = 488 nm) as a function of incident light intensities. The observed nonlinear absorption is attributed to a two-photon absorption process. The pump and probe technique was used to demonstrate all optical switching. The switching characteristics can be utilized to generate all-optical logic gates such as simple inverter switches (NOT) NOR, AND NAND logic functions.     

High speed logic gate using two-photon absorption in silicon waveguides

The switching speed of conventional silicon-based optical switching devices based on plasma dispersion effect is limited by the lifetime of free carriers which introduce either phase or absorption changes. Here we report an all-optical logic NOR gate which does not rely on free carriers but instead uses two-photon absorption. High speed operation was achieved using pump induced non-degenerate two-photon absorption inside the submicron size silicon wire waveguides. The device required low pulse energy (few pJ) for logic gate operation.     

激光二极管泵浦Nd:YAG 946nm激光器及倍频研究

提出如何克服准三能级再吸收损耗和抑制寄生振荡实现LD泵浦的Nd:YAG946nm激光器.在室温下946nm连续输出大于120mW,斜率效率接近10%,同时采用KNbO₃晶体实现了腔内倍频的蓝色激光输出.对实验结果进行了分析并提出了改进措施.     

Efficient generation of blue light by intracavity frequency doubling of a cw Nd:YAG laser with LBO

We report on the efficient room-temperature operation of ⁴F_3/2–⁴I_9/2 transition in a diode pumped Nd:YAG laser operating at 946 nm. An output power of 5.1 W and a slope efficiency of 23.6% at 946 nm have been obtained. Different LBO crystals of length 3×3×10 mm³, 3×3×15 mm³, 3×3×18 mm³ were selected as frequency doubling material for comparison. A maximum single-ended output power of 1.3 W at 473 nm was achieved by frequency doubling with an optical conversion efficiency of 5%. When the Nd:YAG rod was replaced by the one with high reflectivity coating at 473 nm on the pump side, the output power of blue light was almost twice that without high reflectivity coating for 473 nm at the same pump power level. Moreover, the theoretical optimum length of LBO crystal for intracavity frequency doubling was discussed, and the experimental results made a good agreement with it.     

Analytical and simulative studies on optical NOR and controlled NOR logic gates with semiconductor optical amplifier

Semiconductor optical amplifier (SOA) is used for different successful frequency based switching operations. In this paper the authors describe the simulation study of the performances of SOA in various optical switches like frequency conversion, add-drop multiplexer and frequency encoded optical NOR gate, which is one the most important gates in logic family as it is known as one of the universal logic gates. Again, the controlled optical NOR logic operation with semiconductor optical amplifier is also proposed in this paper.     

NOR gate based on QD-SOA at 250 Gbit/s

The performance of all-optical logic NOR gate based on quantum-dot- semiconductor optical amplifier (QD-SOA) is simulated. By solving the rate equations of QD-SOAs when incorporated in the arms of a Mach–Zehnder interferometer the performance of NOR gate is numerically investigated. The model takes into account the impact of the amplified spontaneous emission, the input pulse energy and the injection current density on the system’s quality factor. Results show that NOR gate using QD-SOA is capable of operating at speeds of 250 Gbit/s with proper quality-factor.     

Analysis of an optical logic gate using a symmetric coupler operating with pulse position modulation (PPM)

In this paper we propose the operation of an all-optical logical gate based in a symmetric nonlinear directional coupler (NLDC) operating with a pulse position modulation (PPM). The performance of a symmetric NLDC realizing two-input AND/OR logical functions, which can be applied in transmission and processing of signals in all-optical form in TDM systems, is examined. This integrated symmetric NLDC logical gate operates with two ultrashort soliton light pulses (2 ps), which are modulated in agreement with the technique of pulse position modulation (PPM). Initially, we evaluate the effect resulting of an increment in the PPM coding parameter offset (ε), for the temporal position of the output pulse, considering the anomalous group-velocity dispersion (GVD), nonlinear self phase modulation (SPM) and without loss propagation regime of input pulses, in the cores 1 and 2 of the NLDC. In this situation, we analyze the four possible situations for the two-input logical gate, modulating the 1 and 2 input pulses through temporal displacement and allowing a variation in the coding parameter offset. We can conclude that is possible to get AND/OR logical operations for the cores 1 or 2, without to insert PPM error, since a phase control (Δ?) exists applied in agreement with the logical level of the input pulse in the core 1. Finally we define the truth table, considering the adequate phase difference and coding parameter offset for the stable operation of the AND/OR logical gate based in the symmetric NLDC.     

基于半导体光纤环形腔激光器的新型全光AND门和NOR门

提出了一种新型的基于半导体光纤环形腔激光器(SFRL)中同时发生的四波混频效应和交叉增益调制效应同时实现全光AND门和NOR门方案，并建立了这种全光逻辑门完整的宽带理论模型.通过数值模拟的方法，研究了输入信号光峰值功率及SFRL中两个耦合器的耦合比对这种全光逻辑门输出特性的影响. 关键词： 半导体光纤环形腔激光器 全光逻辑门 四波混频 交叉增益调制     

Repetition Operation of A 447.3 nm Blue–Violet Laser by Intracavity Frequency Doubling of an LD-Pumped Cesium Vapor Laser

We investigate experimentally the repetition operation of a 447.3 nm blue–violet lasers pumped by intracavity frequency doubling of an LD-pumped cesium vapor laser. We study the output performance of the 447.3 nm laser using am LBO crystal as an intracavity frequency doubler. We obtain maximum power in the repetition operation of 0.36 mW, and the slope efficiency does not decrease in the range of pump powers from 2 to 16 W. Our results show that the thermal effect can be reduced in the repetition operation. The optimized working temperature of the LBO is ~25^°C, with a full width at half maximum (FWHM) of 4.1^°C.     

All-optical reconfigurable multi-logic gates based on nonlinear polarization rotation effect in a single SOA

We demonstrate an all-optical reconfigurable logic gate based on dominant nonlinear polarization rotation accompanied with cross-gain modulation effect in a single semiconductor optical amplifier (SOA).Five logic functions,including NOT,OR,NOR,AND,and NAND,are realized using 10-Gb/s on-off keying signals with flexible wavelength tunability.The operation principle is explained in detail.By adjusting polarization controllers,multiple logic functions corresponding to different input polarization states are separately achieved using a single SOA with high flexibility.     

All-optical flip-flop based on vertical cavity semiconductor optical amplifiers

We report the operation of an all-optical set-reset (SR) flip-flop based on vertical cavity semiconductor optical amplifiers (VCSOAs). This flip-flop is cascadable, has low optical switching power (~10 microW), and has the potential to be integrated on a small footprint (~100 microm(2)). The flip-flop is composed of two cross-coupled electrically pumped VCSOA inverters and uses the principles of cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics to achieve flip-flop functionality. We believe that, when integrated on chip, this type of all-optical flip-flop opens new prospects for implementing all-optical fast memories and timing regeneration circuits.     

On the feasibility of ultrafast all-optical NAND gate using single quantum-dot semiconductor optical amplifier-based Mach–Zehnder interferometer

The feasibility of implementing an all-optical NAND gate for 160 Gb/s return-to-zero data pulses using a single quantum-dot semiconductor optical amplifier (QD-SOA)-based Mach–Zehnder interferometer is theoretically investigated and demonstrated. The proposed scheme exploits a modified Fredkin gate simultaneously driven by the pair of data streams between which the Boolean NAND function is to be executed, a sequence of continuous pulses and the complement of the first data input. The impact of the peak data power as well as of the QD-SOAs current density, small signal gain and electron relaxation time from the excited state to the ground state on the amplitude modulation of the switching outcome is explored and assessed by means of numerical simulation. The interpretation of the obtained results allows to specify the conditions under which the QD-SOAs must be biased to operate so that the defined performance metric becomes acceptable. By following the extracted guidelines whose satisfaction is technologically feasible and making a suitable choice for the critical parameters the NAND gate can be realized both with logical correctness and high quality at the target ultrafast data rate while being cascadable and scaleable for constructing more complex all-optical circuits.