Reset Inputs Research Articles

Selective naked-eye detection of Hg²⁺ through an efficient turn-on photoinduced electron transfer fluorescent probe and its real applications.

A simple molecular fluorescent probe 5 has been designed and synthesized by appending anthracene and benzhydryl moieties through a piperazine bridge. The probe upon interaction with different metal ions showed high selectivity and sensitivity (2 ppb) for Hg(2+) through fluorescence "turn-on" response in HEPES buffer. The significant fluorescence enhancement (~10-fold) is attributable to PET arrest due to complexation with nitrogen atoms of the piperazine unit and Hg(2+) in 1:2 stoichiometry, in which a naked-eye sensitive fluorescent blue color of solution changed to a blue-green (switched-on). As a proof of concept, promising prospects for application in environmental and biological sciences 5 have been utilized to detect Hg(2+) sensitively in real samples, on cellulose paper strips, in protein medium (like BSA), and intracellularly in HeLa cells. Moreover, the optical behavior of 5 upon providing different chemical inputs has been utilized to construct individual logic gates and a reusable combinational logic circuit. The combinational circuit (switch ON mode; OR logic gate) is easily resettable to the original position (switch OFF mode; INHIBIT logic gate) by applying reset chemical inputs (OH(-) and PO4(3-)) with great reproducibility.

Discrete dynamical modeling and analysis of the R– S flip-flop circuit

A simple discrete planar dynamical model for the ideal (logical) R– S flip-flop circuit is developed with an eye toward mimicking the dynamical behavior observed for actual physical realizations of this circuit. It is shown that the model exhibits most of the qualitative features ascribed to the R– S flip-flop circuit, such as an intrinsic instability associated with unit set and reset inputs, manifested in a chaotic sequence of output states that tend to oscillate among all possible output states, and the existence of periodic orbits of arbitrarily high period that depend on the various intrinsic system parameters. The investigation involves a combination of analytical methods from the modern theory of discrete dynamical systems, and numerical simulations that illustrate the dazzling array of dynamics that can be generated by the model. Validation of the discrete model is accomplished by comparison with certain Poincaré map like representations of the dynamics corresponding to three-dimensional differential equation models of electrical circuits that produce R– S flip-flop behavior.

Principles of design of a set-reset finite state logic nanomachine

Pulsed electrical set and reset inputs are used to simulate the temporal action of a finite state machine in a three terminal configuration for a variety of arrangements. The gate electrode is necessary only if it is of interest to tune the tunneling rate and to compensate for background charges. When the output is the current, a source and drain electrodes are required. If the output is determined by measuring charge occupancy, then a single junction suffices. The electron transfer rates are computed from the free energy change for a single electron transfer to or from a quantum dot of size such that only charge quantization matters. For a small enough dot the device could operate at room temperature. An asymmetric configuration of the source and drain favors a longer term time preservation of the memory of the device. An alternative design that operates with the same energetics and kinetic parameters is to pulse the resistance rather than the voltage.

All-optical set–reset flip–flop based on the passive microring-resonator bistability

In this paper, we propose a design for an all-optical R–S flip–flop with separate set and reset inputs, which is based on the optical bistability due to Kerr and two-photon absorption (TPA) effects in the microring resonators. Based on the steady state analysis of the light propagation in nonlinear microrings, variations of hysteresis parameters versus the system variables, such as transmission coefficient, nonlinear refractive index and detuning angle, are analyzed. The switching temporal behavior of the proposed flip–flop is obtained by the microring transient analysis. It is shown that the contrast ratio parameter and the switching power of the proposed all-optical flip–flop can be controlled by system parameters.

All-optical flip-flop with high on-off contrast ratio using two injection-locked single-mode Fabry-Perot laser diodes

An all-optical flip-flop with inverted output is presented. The flip-flop is realized based on the optical bistability of an injection-locked single-mode Fabry-Perot laser diode (FP-LD). The operation principle is explained and experimental results are presented in this paper. The flip-flop with separate optical set and reset inputs had an on-off contrast ratio of over 35 dB.

Submicrometer All-Optical Digital Memory and Integration of Nanoscale Photonic Devices Without Isolators

In this paper, the authors introduce multibit all-optical memory devices in nanostructured photonic-crystal circuits using only intrinsic nonresonant optical nonlinearities of semiconductors. Introduced devices can record incoming pulses at speeds of 10 Gb/s using power levels less than 1 mW or at speeds approaching 70 Gb/s using power levels of 10 mW. The incoming pulses are recorded in high-contrast digital output levels independent of the input bit format. The devices exhibit tunable gain for fan-out with negligible reflection and low dissipation and can provide signal regeneration, including reshaping and retiming. Separate signal, clock and reset inputs, and memory outputs coexist without any crosstalk. Input, clock, and output operating frequencies can be independently tuned. By simulating the operation of such all-optical memory devices, it is also shown that nanoscale optical devices can be cascaded to construct densely integrated systems without any isolators or amplifiers, even in the presence of reflections.

All-optical flip-flop memory based on two coupled polarisation switches

An all-optical flip-flop memory with separate set and reset inputs is presented. The flip-flop is realised from two coupled polarisation switches. The concept is explained and experimental results are presented that demonstrate that a contrast ratio of 20 dB and a switching power of <-3 dBm can be obtained. The all-optical flip-flop can be utilised in all-optical packet switches.

Initialisation of BIST Circuits Based on Rule 60 Cellular Automata

A theory of initialising new type linear test pattern generators (TPGs) based on rule 60 Cellular Automata (register composed of T-type flip-flops only) is developed in the paper. Two practical ways of setting an initial state of such registers are also shown. One of them is based on the use of external tester while another one is well suited to BIST applications. They both involve much less area overhead than hitherto employed TPG initialisation techniques, which require using either T-type flip-flops with set or reset inputs or T-type flip-flops equipped with scan mode.

Symmetric self-electro-optic effect device: Optical set-reset latch

We demonstrate an integrated symmetric self-electro-optic effect device consisting of two quantum well p-i-n diodes electrically connected in series. The device acts as a bistable optical memory element with individual set (S) and reset (R) inputs and complementary outputs (optical S-R latch). The switching point is determined by the ratio of the two inputs, making the device insensitive to optical power supply fluctuations when both power beams are derived from the same source. The device also shows time-sequential gain, in that the state can be set using low-power beams and read out with subsequent high-power beams. The device showed bistability for voltages greater than 3 V, incident optical switching energy densities of ∼16 fJ/μm2, and was tested to a switching time of 40 ns.