Dielectric-loaded graphene-based plasmonic multilogic gate using a multimode interference splitter.

100 Gb/s all-optical multifunctional AND, NOR, XOR, OR, XNOR, and NAND logic gates in a single compact scheme based on semiconductor optical amplifiers

In this study, we propose complementary metal-oxide−semiconductor (CMOS) NOR logic gates consisting of silicon nanowire (NW) arrays on bendable substrates. A circuit consisting of two p-channel NW field-effect transistors (NWFETs) in series and two n-channel NWFETs in parallel is constructed to operate a two-input CMOS NOR logic gate. The NOR logic gates operate at a low supply voltage of 1 V with a rail-to-rail logic swing and a high voltage gain of approximately −3.0. The exact NOR logic functionality is achieved owing to the superior electrical characteristics of the well-aligned p- and n-NWFETs, which are obtained using conventional Si-based CMOS technology. Moreover, the NOR logic gates exhibit stable characteristics and have good mechanical properties. The proposed bendable NW CMOS NOR logic gates are promising building blocks for future bendable integrated electronics.

We report on a thin film InGaAsP laser integrated with a 1 x 4 polymer multimode interference (MMI) splitter on a silicon substrate for planar optical signal distribution. The thin film laser had a threshold current of 40 mA and was endfire coupled to the integrated passive polymer MMI splitter, and the optical signal from the laser was distributed to the four output waveguides of the MMI coupler. The measured loss of the MMI splitter was 0.79 dB. The normalized powers of the four MMI output ports in the integrated system were measured to be 0.823, 0.978, 0.852, and 1.

As soft-hardware-logic circuits had been proposed in the literature as an alternative for digital circuits taking advantage the fact that any Boolean function could be implemented with the same cell, just configuring external signals, this work shows a methodology that could be followed particularly for the design of a four bits logic gate, using the so-called neuron MOS transistor (ν-MOS). Simulation results show the feasibility of the design for performing as XNOR, NOR, OR, XOR, AND or NAND logic gates, for instance. In order to extrapolate the design to a higher number of bits, the key issue is to properly consider the weight of the input capacitances in correlation with the number of input bits. A D/A converter can be used as the input stage of the configuration. This design considers the D/A converter-less version, since it helps to increase device integration as the number of transistors used is reduced with no difference in its performance. The design should be based on the theoretical floating potential diagram (FPD) of the desired logic gate.

All-optical switching has been theoretically analyzed in LOV2 phototropin, the blue light plant photoreceptor based on nonlinear intensity-induced excited-state absorption. The transmission of a cw probe laser beam at 660 nm through LOV2 protein can be controlled by a cw or pulsed pump laser beam at 442 nm, respectively. This modulation is sensitive to the small-signal absorption coefficient, absorption cross-section of the excited L-state at pump beam wavelength and sample thickness. It is shown that the unique spectral and kinetic properties of wild-type LOV2 and LOV2-C39A mutant, result in the probe beam getting completely switched off (100% modulation), by the pump laser beam of intensity 50 kW/cm² and 1 kW/cm², respectively. The switching response in LOV2-WT is faster (~μs) than in LOV2-C39A mutant (~ms). The results have been used to design an optically-addressed spatial light modulator and all-optical NOT, and the universal NAND and NOR logic gates. The results show the applicability of this novel plant photoreceptor protein for photonic applications.

The novel 2×VDD NOT, NAND, and NOR logic gates have been designed and implemented in a nanoscale CMOS process with only 1×VDD devices. With the proposed dynamic source bias technique, the logic gates can be designed to have 2×VDD tolerant capability. Thus, the new 2×VDD logic gates can be operated under 2×VDD voltage environment without suffering the gate-oxide reliability issue.

A detailed theoretical analysis of reverse saturable absorption (RSA) to saturable absorption (SA) transition has been presented in Ru complex [{Ru (bipy)2}2L][PF6], with picosecond laser pulses at 532 nm wavelength. Interestingly, it is shown that an increase in pulse intensity leads to transition from RSA to SA, with increased contrast, due to strong excited-state absorption. Theoretical results are in good agreement with reported experimental results. The effect of pulse intensity, pulse width, frequency and concentration has been studied to optimize the RSA to SA transition, which has been used to design all-optical picosecond NOT, AND, OR, and the universal NAND and NOR logic gates. The designs are the first application of Ru dioxolene complex based all-optical logic gates with picosecond switch off/on time. These results show the potential of transition-metal complexes for photonic applications.

We demonstrate a technique to convert p-type single-walled carbon nanotube (SWNT) network transistor into ambipolar transistor by thermally evaporating C60 on top. The addition of C60 was observed to have two effects in enhancing ambipolar characteristics. First, C60 served as an encapsulating layer that enhanced the ambipolar characteristics of SWNTs. Second, C60 itself served as an electron transporting layer that contributed to the n-type conduction. Such a dual effect enables effective conversion of p-type into ambipolar characteristics. We have fabricated inverters using our SWNT/C60 ambipolar transistors with gain as high as 24, along with adaptive NAND and NOR logic gates.

Swirling spin configurations with a non-trivial topological state are popularly known as magnetic skyrmions. They are often observed in magnetic thin films with perpendicular magnetic anisotropy and Dzyaloshinskii–Moriya interaction (DMI). Due to their small size and non-collinear spin texture, they are being considered as a potential candidate for spintronic devices such as data storage devices, and logic-based devices. These skyrmions have distinct properties and interactions, that can be utilized to control their movement by applying an external electric current. In this work, we have successfully demonstrated the operation of skyrmion-based universal NAND and NOR logic gates. We have further performed arithmetic addition of two and three single-bit by using a half and full adder, fabricated based on the XOR and AND gates. We have observed that the presence of only uniform DMI is not enough to achieve all logic operations. The presence of a negative DMI at the edges is crucial in achieving proper logic operations. The findings are very important for the realization of skyrmion-based logic and computational operations.

Theoretical analysis of reverse saturable absorption in graphene-oxide metal porphyrin composites with femtosecond laser pulses at 800 nm has been presented and optimized to design ultrafast all-optical universal NAND and NOR logic gates.

We propose a hybrid structure composed of a silver mirror and two spaced graphene monolayers to enhance light absorption. A broad plasmon-induced reflection (PIR) window can be generated because of the destructive interference between the bright and dark modes, resulting in a dual-narrowband absorption switching effect. The dual-narrowband absorption switch is strongly dependent on the geometric structure parameters and dynamic tuning parameter of the hybrid structure, and each parameter has a wide tuning range for absorption state ‘on/on’. Especially, compared with the hybrid structure composed of a graphene monolayer and one-dimensional photonic crystal (1D PC), the proposed structure is simpler and easier to fabricate, and the dynamic tuning width of Fermi energy of graphene for light absorption state ‘on/on’ is significantly broadened (∼3 times). Compared with plasmon-induced transparency (PIT) systems, the absorption performance of graphene is greatly enhanced, and the absorption is increased from about 50% to higher than 97%. Moreover, by adjusting the widths of the graphene monolayers, NAND and NOR logic gates are realized, and the output contrast between logic states ‘1’ and ‘0’ is high up to 18.6 dB. This study may provide an approach to construct dual-narrowband absorption switches, perfect absorbers, and plasmon logic gates.

Due to the increasing trend of photonic element miniaturisation and the need for optical splitting, we propose and simulate a new type of three-dimensional (3D) optical splitter based on multimode interference (MMI) for the wavelength of 1550 nm. We present various designs and simulations of various parameters for the optimized MMI splitter. We focus on the possibility of its integration on an optical fiber. The design is focused on a possible production process using 3D laser lithography for the prepared experiments. The MMI splitter was prepared by laser lithography using direct writing process and finally investigated by output characterisation by the near-field measurement.

Ultrafast saturable and reverse saturable absorption has been theoretically analyzed in hemoprotein cytochrome-c (cyt-c). The effect of laser pulse intensity and pulse width, absorption cross-section, pulse frequency and lifetime of the excited states has been studied in detail to optimize saturable and reverse saturable absorption. The results have been used to design all-optical femtosecond AND, OR NOT and the universal NOR and NAND logic gates, at 530 and 460 nm respectively. Theoretical simulations are in good agreement with reported experimental results. The designs are the first application of cyt-c based all-optical logic gates with sub-picosecond switch off/on time. The advantages of simple design, ultrafast operation, high nonlinear optical coefficients and stability of cyt-c in a broad spectral range, make it prospective for photonic computing applications.

In this paper, a novel all-optical NOR logic gate based on two dimension (2-D) photonic crystals (PC) is designed and simulated by a cascade of two all-optical switches. The new all-optical switch is composed of a nonlinear photonic crystal ring resonator (PCRR) and T-type waveguide. The PC structure has a square lattice of silicon rod with refractive index of 3.39 in air. The bandgap of this structure is derived by the plane wave expansion (PWE) method, which is from a/= 0.32 to a/= 0.44. In this structure to work at the wavelength of 1550 nm, the lattice constant ‘a’ should be 630 nm; the total size of the proposed optical NOR gate is only 18 m × 11 m. The simulation results using two dimensional finite difference time domain (FDTD) method indicated that the proposed optical NOR logic gate is a potential candidature for ultrafast optical digital circuits.

An all-optical logic NOR gate operating at 40 Gb/s has been demonstrated using an SOA-based Mach-Zehnder interferometer (MZI). An optical loop mirror is used as a delayed interferometer to reshape the return-to-zero (RZ) NOR sequence from the MZI output port. The performance of the NOR operation is numerically analyzed by solving the rate equation of an SOA. An increase in signal output power enhances the Q factor and extinction ratio. Faster SOAs such as quantum-dot SOAs can achieve higher Q value. The demonstrated technique has potential for optical logic operation at ultrahigh speed