Pulse Polarization Research Articles

High-Performance CMOS Latch Designs for Recovering All Single and Double Node Upsets

Latches areused extensivelyin digital circuits; however, as technology scaling reaches nanometric feature sizes, externally induced phenomena (such as radiation strikes in aerospace applications) may cause a single event upset (SEU) in either single or double nodes. Rather than masking, mitigation of an SEU is effectively achieved by recovering the correct value throughthe design of hardened latches. Using the polarity of the radiation-induced voltage pulse, a stacked design is proposed; this circuit permits to accomplish protection and SEU recovery at reduced overhead and so at substantially improved performance. The first proposed latch (RH-1) recovers all single node upsets and has an extremely low delay in its operation, because this latch propagates data to the output stage though only a transmission gate. The fast operation of RH-1 is utilized in the second latch (RH-2) proposed in this article. RH-2 consists of two RH-1 modules to guarantee that at least two nodes maintain the latched values under the occurrence of a double node upset. Simulation results are provided; they show that RH-1 (recovering all single node upsets and many double node upsets) has the best delay and power-delay-area product (PDAP, as combined metric) among all considered designs and the second-best area and dynamic power dissipation among the recovering schemes, and meanwhile RH-2 (recovering all double node upsets) has the best dynamic power dissipation and PDAP among all considered designs and the best area and delay among recovering schemes.

Development of Microchip Laser for Ophthalmic Therapy Application

We have recently developed a several milli-joule, sub-nanosecond laser source for ophthalmic therapy application which allows to lower a laser breakdown threshold, less than half, and more stably/effectively yield the breakdown phenomenon compared to that based on conventionally employed source, implying the developed source has a potential to realize more minimally invasive ophthalmic treatment for secondary cataract. For further laser performance, the use of a photonic crystal device as an output coupler of the laser source has been also demonstrated. With this system, pulse width shortening and polarization control of the laser output could be achieved simultaneously. This paper presents these recent ophthalmic laser developments.

Depolarization of the supercontinuum induced by linearly and circularly polarized femtosecond laser pulses in water

The supercontinuum (SC) is generally assumed to inherit the polarization of the incident pulse in isotropic media. In this study, we experimentally investigated the polarization properties of SC spectra induced by different polarized femtosecond lasers in water. The results show that the extent of depolarization of the SC induced by a quasicircularly polarized pulse is more pronounced than that of a quasilinearly polarized pulse. In terms of the different spectral components, the long-wavelength components experienced more depolarization, and the short-wavelength components tended to be linearly polarized for both polarized input femtosecond lasers. The depolarization mechanism can be attributed to two factors, namely, the energy coupling between the two polarized components of the input femtosecond pulse, and the various degrees of nonlinear birefringence experienced by different spectral components of the SC during propagation.

Polarization control of attosecond pulses using bi-chromatic elliptically polarized laser

We study the high harmonic generation (HHG) using elliptically polarized two-color driving fields. The HHG via bi-chromatic counter-rotating laser fields is a promising source of circularly polarized ultrashort XUV radiation at the attosecond time scale. The ellipticity or the polarization of the attosecond pulses (APs) can be tweaked by modifying the emitted harmonics’ ellipticity, which can be controlled by varying the driver fields. A simple setup is used to control the polarization of the driving fields, which eventually changes the ellipticity of the APs. A well-defined scaling for the ellipticity of the AP as a function of the rotation angle of the quarter-wave plate is also deduced by solving the time-dependent Schrödinger equation in two dimensions. The scaling can further be explored to obtain the APs of the desired degree of polarization, ranging from linear to elliptical to circular polarization.

Forward terahertz wave generation from liquid gallium in the non-relativistic regime

We characterize a terahertz (THz) source based on plasma in liquid gallium. The dependence of the emitted THz pulse energy on second-order phase, pump pulse energy, and polarization of the short laser pulse is demonstrated. Our study suggests that the THz emission mechanism is due to the ponderomotive force and is aided by a direct-field driven term. The proposed source and accompanying generation mechanism are studied under a non-relativistic regime ( 1 0 15 < I < 1 0 18 W / c m 2 ) for forward directed THz under a single pump excitation scheme.

Research on the characteristics of atmospheric air dielectric barrier discharge under different square wave pulse polarities

Energy efficiency limits the application of atmospheric pressure dielectric barrier discharge (DBD), such as air purification, water treatment and material surface modification. This article focuses on the electrical and optical effects of the DBD under three square wave pulses polarities-positive, negative and bipolar. The result shows that under the same voltage with the quartz glass medium, the discharge efficiency of bipolar polarity pulse is the highest due to the influence of deposited charge. With the increase of air gap distance from 0.5 to 1.5 mm, average power consumed by the discharge air gap and discharge efficiency decrease obviously under alumina, and increase, and then decrease under quartz glass and polymethyl methacrylate (PMMA). Through spectrum diagnosis, in the quartz glass medium, the vibration temperature is the highest under negative polarity pulse excitation. Under bipolar pulse, the vibration temperature does not change significantly with the change of air gap distance. For the three dielectric materials of quartz glass, alumina and PMMA, the molecular vibration temperature is the highest under the quartz glass medium with the same voltage. When the gap spacing, pulse polarity or dielectric material are changed, the rotational temperature does not change significantly.

Ultrafast Photon-Induced Tunneling Microscopy.

Unification of the techniques of ultrafast science and scanning tunneling microscopy (STM) has the potential of tracking electronic motion in molecules simultaneously in real space and real time. Laser pulses can couple to an STM junction either in the weak-field or in the strong-field interaction regime. The strong-field regime entails significant modification (dressing) of the tunneling barrier of the STM junction, whereas the weak-field or the photon-driven regime entails perturbative interaction. Here, we describe how photons carried in an ultrashort pulse interact with an STM junction, defining the basic fundamental framework of ultrafast photon-induced tunneling microscopy. Selective dipole coupling of electronic states by photons is shown to be controllable by adjusting the DC bias at the STM junction. An ultrafast tunneling microscopy involving photons is established. Consolidation of the technique calls for innovative approaches to detect photon-induced tunneling currents at the STM junction. We introduce and characterize here three techniques involving dispersion, polarization, and frequency modulation of the laser pulses to lock-in detect the laser-induced tunneling current. We show that photon-induced tunneling currents can simultaneously achieve angstrom scale spatial resolution and sub-femtosecond temporal resolution. Ultrafast photon-induced tunneling microscopy will be able to directly probe electron dynamics in complex molecular systems, without the need of reconstruction techniques.

Generation of quantum vortices in photodetachment: The role of the ground-state wave function

Formation of quantum vortices in laser-induced photodetachment from negative ions is analyzed. The driving laser field consists of a single ultrashort pulse of circular polarization and the unperturbed ground-state wave function of the anion is found in either the $s$ or $p$ state. In particular, numerical illustrations for the photodetachment from ${\mathrm{H}}^{\ensuremath{-}},$ ${\mathrm{O}}^{\ensuremath{-}},$ ${\mathrm{K}}^{\ensuremath{-}},$ and a model ${\mathrm{A}}^{\ensuremath{-}}$ anion are presented. Special attention is paid to the symmetry of the ground-state wave function and ionization potential over the final vortex pattern. It is shown that the two-dimensional spectra of photoelectrons in momentum space comprise three well-defined regions: The low-energy (central) region, multiphotonlike zone, and supercontinuum. While the supercontinuum does not contribute to vorticity and the multiphoton zone depends only on the laser field characteristics, vortices in the low-energy region strongly depend on the bound-state wave function and its ionization potential.

The self-powered artificial synapse mechanotactile sensing system by integrating triboelectric plasma and gas-ionic-gated graphene transistor

The emulation of biological nerves to develop artificial synapse tactile sensing system has great application potentials in the fields of Internet of Things and artificial intelligence. Novel sensing strategies to achieve low power consumption, low cost, low complexity and high efficiency still face challenges. Here, a self-powered tactile sensing system has been developed by integrating a triboelectric plasma and a gas-ions-gated (GIG) graphene transistor, in which the GIG transistor is served as the artificial synapse, and the triboelectric plasma is served as both a tactile sensor and the driving signals of the GIG transistor. The N2+ ions in the triboelectric plasma are directly adsorbed on the graphene surface, acting as a floating gate of the GIG transistor to regulate its electrical transport characteristics. The adsorption density of N2+ ions reach up to 3.96 × 1012 cm−2 with a measured desorption energy of 196 meV. The theoretical simulation shows that the N2+ ion is adsorbed at the site of carbon vacancy on the graphene surface. By regulating the number, frequency and polarization of the discharge pulse, various synaptic behaviors are achieved, such as short-term depression, long-term depression, long-term potentiation, paired-pulse facilitation, etc. Also, the neural functions of learning and temporal decoding have been demonstrated in experiments. By combining triboelectric plasma and GIG transistor, a facile experimental scheme for a self-powered, integrated, and simple structured intelligent tactile sensing system has been proposed, which is highly expected to promote the development of intelligent sensing fields in the future.

Ultrafast valley polarization in bilayer graphene

We study theoretically the interaction of a bilayer graphene with a circularly polarized ultrafast optical pulse of a single oscillation at an oblique incidence. The normal component of the pulse breaks the inversion symmetry of the system and opens up a dynamical bandgap due to which a valley-selective population of the conduction band becomes sensitive to the angle of incident of the pulse. We show that the magnitude of the valley polarization can be controlled by the angle of incidence, the amplitude, and the angle of in-plane polarization of the chiral optical pulse. Subsequently, a sequence of a circularly polarized pulse followed by a linearly polarized femtosecond-long pulse can be used to control and probe the valley polarization created by the preceding pulse. Our protocol provides a favorable platform to design ultrafast all-optical valleytronic information processing.

Effects of electrical pulse polarity shape on intra cochlear neural responses in humans: Triphasic pulses with anodic and cathodic second phase

Modern cochlear implants employ charge-balanced biphasic and triphasic pulses. However, the effectiveness of electrical pulse shape and polarity is still a matter of debate. For this purpose, a previous study (Bahmer & Baumann, 2013) conducted electrophysiological and psychophysical measurements following triphasic pulse stimulation with constant cathodic second phase and varying anodic first and third phases. Pulse stimulation with constant anodic second phase was not investigated.Therefore, in this study, pulse stimulation with cathodic and anodic second phase was applied for the recording of electrically evoked compound action potentials (ECAPs) as well as for psychophysical thresholds in cochlear implant (CI) recipients. First it was investigated whether the temporal polarity distribution has a different effect on neuronal stimulation when the second phase is cathodic or anodic; second, whether the electrophysiological and psychophysical results show a comparable difference between triphasic stimulation with anodic and cathodic second phases.The results showed that variation of the temporal polarity distribution of the triphasic pulse had a smaller effect on the ECAP response when the second phase was anodic compared to when it was cathodic, whereas for psychophysical detection thresholds this variation had a similar effect for both polarities. While electrophysiological responses and psychophysical detection thresholds showed a high correlation for variations of the triphasic pulse with cathodic second phase, the results for variations of the triphasic pulse with anodic second phase showed only moderate correlation. Furthermore, the difference between triphasic stimulation with cathodic and anodic second phases did not correlate between the electrophysiological and psychophysical results.In summary, after stimulation with different configurations of triphasic pulses used in the present study, the polarity of the second phase has an effect on electrophysiological response at suprathreshold level but not on the psychophysical detection thresholds. Thus, at different stimulation levels a possible substitution of the psychophysical test by an electrophysiological measurement (e.g. neural health measurement of the cochlea) could not be corroborated by the present results.

Demonstration of Threshold Switching and Bipolar Resistive Switching in Ag/SnOx/TiN Memory Device

In this work, we observed the duality of threshold switching and non-volatile memory switching of Ag/SnOx/TiN memory devices by controlling the compliance current (CC) or pulse amplitude. The insulator thickness and chemical analysis of the device stack were confirmed by transmission electron microscope (TEM) images of the Ag/SnOx/TiN stack and X-ray photoelectron spectroscopy (XPS) of the SnOx film. The threshold switching was achieved at low CC (50 μA), showing volatile resistive switching. Optimal CC (5 mA) for bipolar resistive switching conditions with a gradual transition was also found. An unstable low-resistance state (LRS) and negative-set behavior were observed at CCs of 1 mA and 30 mA, respectively. We also demonstrated the pulse operation for volatile switching, set, reset processes, and negative-set behaviors by controlling pulse amplitude and polarity. Finally, the potentiation and depression characteristics were mimicked by multiple pulses, and MNIST pattern recognition was calculated using a neural network, including the conductance update for a hardware-based neuromorphic system.

Coherent control of asymmetric spintronic terahertz emission from two-dimensional hybrid metal halides

Next-generation terahertz (THz) sources demand lightweight, low-cost, defect-tolerant, and robust components with synergistic, tunable capabilities. However, a paucity of materials systems simultaneously possessing these desirable attributes and functionalities has made device realization difficult. Here we report the observation of asymmetric spintronic-THz radiation in Two-Dimensional Hybrid Metal Halides (2D-HMH) interfaced with a ferromagnetic metal, produced by ultrafast spin current under femtosecond laser excitation. The generated THz radiation exhibits an asymmetric intensity toward forward and backward emission direction whose directionality can be mutually controlled by the direction of applied magnetic field and linear polarization of the laser pulse. Our work demonstrates the capability for the coherent control of THz emission from 2D-HMHs, enabling their promising applications on the ultrafast timescale as solution-processed material candidates for future THz emitters.

Intramolecular photo-driven charge transfer in a series of pyridyl substituted phenyloxazoles. Structural relaxation in meta-substituted ethylpyridinium derivative of phenyloxazole.

A series of pyridyl (pyridinium) substituted benzoxazoles were studied by steady state absorption, fluorescence spectroscopy, time-resolved fluorescence spectroscopy, fs pulse absorption and polarization spectroscopy, and quantum-chemical calculations. The spectral and kinetic parameters of the fluorophores in MeCN and EtOAc were obtained experimentally and were calculated by means of DFT and TDDFT methods. A scheme including four transient excited states was proposed for the interpretation of differential absorption kinetics of the charged fluorophores. Expressions describing the actual kinetics graphs, the decay associated spectra, and the species-associated spectra were derived. The charge shift step was found to be dependent on average solvation times. A charge shift followed by the formation of the twisted conformer was found for the excited 1-ethyl-3-(5-phenyloxazol-2-yl)pyridinium 4-methyl-1-benzenesulfonate in MeCN and EtOAc. Conformational analysis confirms a large amplitude motion of the meta-substituted ethylpyridinium group as an additional structural relaxation path producing an abnormally large fluorescence Stokes shift.

Co-effect of dielectric layer material and driving pulse polarity on the spatial emission intensity distributions of micro dielectric barrier discharge

A micro concentric ring device with asymmetric dielectrics (glass and n-silicon) is driven by a bipolar pulse generator with 20 kHz frequency, 1 μs pulse width, 50 ns rising/falling time, and 3.6 kV peak-to-peak voltage, and the spatial emission intensity distributions in the device are investigated. The experiments are operated at 133 mbar pure argon. The spatial-temporal microplasma evolution recorded by intensified charge-coupled device illustrates that ‘edge emission’ arises in the microchannels when the electrode (indium tin oxide) on which the glass dielectric is located acts as the cathode. However, when the electrode (conductive silver paste) adjacent to the n-silicon acts as the cathode, ‘center emission’ is induced. The dielectric materials’ properties (relative permittivity and secondary electron emission coefficient), synergistically with the pulse polarity, which determines the influence of the residual long-living particles generated by previous discharge on the subsequent discharge, are inferred to be responsible for the distinct spatial emission intensity distributions at different pulse polarities. When the n-silicon is situated on the cathode, the high permittivity of n-silicon repels the electric field into plasma, which means that the electrons can obtain more energy in the first half of their journey. Furthermore, the high secondary electron yield of n-silicon makes it possible to provide more seed electrons for microdischarge. This mechanism of electrons dynamics leads to the occurrence of ‘center emission’. When the positive half period of the bipolar pulse arrives at the n-silicon, the residual charged particles generated by the previous discharge will induce a reversed electric field in the channel center to impair the applied electric field and bring about the ‘edge emission’, but this cannot emerge in the microdischarge powered by the unipolar pulse. Investigation of spatial emission intensity distributions of microplasmas is important for the comprehension of devices based on micro-structure techniques.

Highly stable sub-nanosecond Nd:YAG pump laser for optically synchronized optical parametric chirped-pulse amplification.

We developed an optically synchronized highly stable frequency-doubled Nd:YAG laser with sub-nanosecond pulse duration. The 1064 nm seed pulses generated by soliton self-frequency shift in a photonic crystal fiber from Ti:sapphire oscillator pulses were stabilized by controlling input pulse polarization. The seed pulses were amplified to 200 mJ by diode-pumped amplifiers with a high stability of only <0.2% (rms). With an external LBO doubler, the system generated 330 ps green pulse energy of 130 mJ at 532 nm with a conversion efficiency of 65%. The pulse duration was further extended to 490 ps by adjusting Nd:YAG crystal temperature. To the best of our knowledge, these results present a longer pulse duration with higher stability than previous Nd:YAG lasers with sub-nanosecond optical synchronization.

Role of resident electrons in the manifestation of a spin polarization memory effect in Mn delta-doped GaAs heterostructures

The spin-memory effect in the GaAs / InGaAs heterostructures with $\delta$<Mn> layer in GaAs barrier have been investigated. The effect consists in spin polarization of Mn atoms due to interaction with photogenerated spin-polarized holes. The investigation of the effect was carried out by analyzing the polarization of the probe photoluminescence pulse in the pump-probe technique. It was shown that the circular polarization degree of probe pulse generated photoluminescence is strongly affected by the interaction of hole spins with spins of Mn atoms polarized by the pump pulse. The latter leads to decrease of circular polarization degree as compared with single pulse excitation ($\delta P$ effect). The amplitude of $\delta P$-effect is most strongly affected by the concentration of resident electrons in the quantum well which is believed to be due the specific compliance with selection rules for optical transition with the participation of unpolarized resident electrons. The rest of the sample's parameters including the spatial separation between $\delta$<Mn> layer and InGaAs quantum well ($d_s$) have a minor effect on the $\delta P$ value which leads to a paradoxical situation of decreasing $\delta P$-effect with the decrease of $d_s$. The proposed experimental technique consisting in creating the significant concentration of resident electrons in the QW may serve as a reliable photoluminescence method determining the strength of this effect as well as the Mn spin relaxation time in a particular nanostructure.

Formation of PEO coating on Al microelectrode under elementary anodic/cathodic pulses

Cathodic sweep and pulse polarization of bare and anodized Al microelectrodes were carried out in alkaline silicate solution. The sweep polarization causes a severe damage to as-polished Al, but reduced and localized damages to the anodized Al. The anodic film resists both cathodic sweep and pulse breakdown. Cathodic pulse polarization can cause capacitive charging and mechanical damage to the oxide film and the substrate depending on the degree of polarization. High cathodic pulse polarization causes sparking and subsequent modification of discharge channels formed by the prior anodic breakdown. The enhancement of plasma formation and sparking during cathodic pulse breakdown is associated with cathodic corrosion of Al, excessive H 2 gas formation and local high electric field. Although sparking cathodic breakdown explodes the discharge channels and causes the loss of coating materials, it does not alter its beneficial role to randomize the sites breakdown by succeeding anodic pulse. The sequential pulses form dense coating materials. • Elementary role of sparking cathodic breakdown on PEO coating growth • Sparking cathodic breakdown causes loss of coating materials. • Sparking during cathodic breakdown does not alter its novel role to randomize anodic breakdown sites.

Role of charge accumulation in guided streamer evolution in helium DBD plasma jets

Experimental data are presented on the evolution of a helium atmospheric pressure plasma jet driven by a tailored voltage waveform generated as bunches of voltage pulses consisting of a superposition of approx 43 kHz bipolar square pulses and approx 300 kHz oscillations. The characteristics of directed ionization waves (guided streamers) are compared for bunches with different first pulse polarities and different bunch duty cycles. The longest and brightest streamers are achieved at the voltage bunch with the first negative pulse and a minimum duty cycle. The dynamics of streamers at the voltage bunch with the first positive pulse are characterized by the shortest length and a lower brightness. The plasma jet length can be smoothly changed by varying the number of pulses in the bunch and the polarity of the first pulse. It is thus possible to precisely localize the region of a strong field in space by combining the parameters of the applied voltage (the duty cycle and polarity of the first pulse of a bunch) with a stepwise propagation mode of a guided streamer.

Elementary tripartite quantum communication photonic network at the telecom wavelength

An elementary tripartite quantum communication network for discrete variables is proposed. In this network three nodes are quantum wired with quantum channel created by a pair of Greenberger–Horne–Zeilinger (GHZ) triplet. We show that in this network by local operations and classical communication an arbitrary two-qubit state can be deterministically teleported from any node to any other node. In this network tripartite teleportation of two-qubit state is achieved by first splitting the qubit into fragments and then at the destination, qubit is re-constructed from the fragments. A high flux source for generation of fully inseparable GHZ photonic quantum channel required for developing an ideal tripartite quantum network is presented. This GHZ source employ a group velocity matched periodically poled potassium titanyl phosphate crystal in pulsed polarization Sagnac interferometer configuration and is based on selecting a three-photon entangled state from the product state of an entangled photon pair and a weak coherent state. This GHZ source generates tripartite entangled photons at telecom wavelength (1584 nm). Genuine entanglement in the generated GHZ state is detected with a witness (W) operator. Complete detail of the experimental apparatus required for developing an ideal tripartite quantum communication photonic network, which employ fully inseparable quantum channel, is presented. This quantum network fully operates at wavelength 1584 nm, which occurs in the L-band of the technologically important third telecom window. Success probability for teleportation of two-qubit photonic state within the tripartite quantum network is determined. We show that such quantum network is experimentally feasible. Experimental procedure to unambiguously verify the teleportation of an arbitrary two-qubit photonic state within the network is discussed. It is shown that our scheme can be implemented in a programmed teleportation system and it paves the way towards a large-scale quantum network.