Nonlinear optical switching and all-figures of merit in Bi2S3-xSex/PMMA nanocomposite films investigated by Z scan under visible CW laser

Bi2S3-xSex/poly(methyl methacrylate)(PMMA)nanocomposite films were prepared using microwave assisted synthesis with different compositions of x.Crystal structure,surface morphology,and optical properties were investigated to characterize the prepared nanocomposite films.The crystallinity and optical band gap of the prepared Bi2S3-xSex/PMMA were affected by x.The prepared samples showed a blue shift in the absorption edge.The laser power dependent nonlinear refraction and absorption of Bi2S3-xSex/PMMA nanocomposite films were investigated by using the Z-scan technique.The optical nonlinearity of the nanocomposite films exhibited switchover from negative nonlinear refraction to positive nonlinear refraction to negative nonlinear refraction effects,and from saturable absorption to reverse saturable absorption to saturable absorption with an increase and decrease in the composition.An interesting all-optical figure of merit was reported to assess the nanocomposite films for a practical device.It was calculated that the device all-figures of merit were based on the nonlinear response,which is important for the all-optical switching device.The results demonstrate that the optimized all-optical figures of merit can be achieved by adjusting the composition and input laser power,which can be used for the design of different all-photonic devices,and the results of nonlinear switching behavior can open new possibilities for using the nanocomposite films in laser Q-switching and mode-locking.     

Three-Wave Resonant Interaction in Optical Fibres on a Continuous-Wave Background

We predict that a three-wave resonant interaction (TWRI) for the excitations created from a continuous-wave background is possible in nonlinear optical fibres with a centro-symmetry. We show that in normal dispersion regime and near the zero-dispersion point of a single-mode optical fibre, the phase-matching condition for the TWRI can be satisfied by suitably choosing the wavevectors and frequencies of the exciting waves. The nonlinear envelope equations for the TWRI are derived by using a method of multiple-scales, and their explicit solutions for sum- and difference-frequency mixing are provided and discussed.     

An all-optical comparison scheme between two multi-bit data with optical nonlinear material

Over the last few decades,several all-optical circuits have been proposed to meet the need of high-speed data processing.In some information processing architectures,the role of various analog and digital data comparisons is very important.In this letter,we proposed a multi-bit data comparison scheme.The scheme is based on the switching property of optical nonlinear material.Ultrafast operational speed larger than gigahertz can be expected from this all-optical scheme.     

Design of ultrafast all-optical PolSK DMUX based on semiconductor optical amplifiers

A novel ultrahigh-speed all-optical demultiplexer (DMUX) with polarization-shift-keying (PolSK) modulation input signals is proposed. This design is based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). For analyzing each amplifier, we use finite-difference method (FDM) based on solution of the traveling wave coupled equations. Using numerical simulation, the all-optical DMUX is theoretically realized at 40 Gb/s. We also study the relation between optical confinement factor and thickness of active layer of the SOA section successfully, and investigate the increasing effect of confinement factor on the DMUX optical output power. With this work, the confinement factor is increased from 0.3 to 0.48, and as a result, the output power approximately twice of its initial value is achieved. Moreover, the effects of polarization dependence of SOA on the output performance of all-optical DMUX for PolSK signal are theoretically investigated in detail.     

Designing of an all-optical time division multiplexing scheme with the help of nonlinear material based tree-net architecture

In the field of optical interconnecting network and in super fast photonic computing system, the tree architecture and optical nonlinear materials can play a significant role. Nonlinear optical material may find important uses in optical switching. Optical switch using nonlinear material makes it possible for one optical signal to control and switch another optical signal through nonlinear interaction in a material. In this communication such materials have been successfully exploited to design an all-optical tree-net architecture, which can be utilized for time division multiplexing scheme in all-optical domain.     

Ccontrolling the Transition Between "Higher" and "Lower" State of OB in Coherent Atomic Medium

We present a new experimental demonstration that the threshold points and shape of OB hysteresis curve in a four-level Rb atomic system inside an optical cavity were controllably changed by optical signals.Tuning the triggering optical signal to two different transitions of the atomic system we found that the OB threshold points shift toward different direction and at the same time the shape of the OB curve is also changed.For a given intensity of probe laser the OB system can be reliably inversed from its lower stable state to upper state under the triggering of a suitably tuned optical pulse signal (we named it up-controlling signal).More interesting, the inversed OB state does not drop to its initial lower stable state after the triggering pulse signal has passed, but moves to the upper branch of the initial OB curve and stably stays there until another optical signal tuned on other atomic transition (named down-controlling signal) coming.The result shows that there is the ability of information storage in the OB system.The experiments are reasonably explained with the change of cavity resonant condition resulting from the enhanced third-order nonlinearity in multilevel atomic system owing to atomic coherence.     

Designing of an all-optical time division multiplexing scheme with the help of nonlinear material based tree-net architecture

In the field of optical interconnecting network and in super fast photonic computing system, the tree architecture and optical nonlinear materials can play a significant role. Nonlinear optical material may find important uses in optical switching. Optical switch using nonlinear material makes it possible for one optical signal to control and switch another optical signal through nonlinear interaction in a material.In this communication such materials have been successfully exploited to design an all-optical tree-net architecture, which can be utilized for time division multiplexing scheme in all-optical domain.     

A Novel All-optical Wavelength ConverterBased on Self-pump Four-wave Mixing

A novel scheme of all-optical wavelength converter(AOWC) based on dual pump four-wave mixing(DP-FWM) was demonstrated. To suppress the ASE noise of the semiconductor optical amplifier (SOA), one of the two pumps was generated interiorly from a loop laser constructed mainly by tunable optical filter and SOA. The theoretical model and some experimental results were presented.     

All-optical switching and nonlinear optical properties of HBT in ethanol solution

This paper demonstrates an all-optical switching model system comprising a single pulsed pump beam at 355 nm and a CW He--Ne signal beam at 632.8 nm with 2-(2^\prime -hydroxyphenyl)benzothiazole (HBT) in ethanol solution. The origins of the optical switching effect were discussed. By the study of nonlinear optical properties for HBT in ethanol solvent, this paper verified that the excited-state intramolecular proton transfer (ESIPT) effect of HBT and the thermal effect of solvent worked on quite different time scales and together induced the change of the refractive index of HBT solution, leading to the signal beam deflection. The results indicated that the HBT molecule could be an excellent candidate for high-speed and high-sensitive optical switching devices.     

Effect of Quantum Interference from Incoherent Pumping Field and Spontaneous Emission on Controlling the Optical Bistability and Multi-Stability

Optical bistability (OB) and optical multi-stability (OM) of a four-level Λ-type atomic system with two fold lower levels inside a unidirectional ring cavity is investigated. The effect of quantum interference arising from spontaneous emission and incoherent pumping on OB and OM is discussed. It is found that the threshold of OB and OM can be controlled by quantum interference mechanisms. In addition intensity of coupling field and the rate of an incoherent pumping field on behavior of OB and OM are then discussed.     

Controllable Optical Bistability and Multistability in a Four-Level Atomic System with Closed-Loop Configuration

We theoretically investigate optical bistability （OB） and multistability （OM） behaviour of a closed-loop configuration atomic system driven by a degenerate coupling- field and a degenerate probe field inside a unidirectional ring cavity. It is found that the OB and OM behaviour can be controlled by adjusting- the intensity and the frequency detuning of the coupling- field, respectively. Interestingly, our numerical results show that it is easy to realize the transition from OB to OM or vice versa by adjusting- the intensity of the coupling- field under a appropriate frequency detuning. The effect of the atomic cooperation parameter on the OB behaviour is also discussed.     

Dromion Excitations in Self—Defocusing Optical Media

We investigate the nonlinear dynamics of multi-dimensional optical pulses propagating in an isotropic selfdefocusing medium,Using a method of multiple-scales we show that the nonlinear evolution of the pulses is governed by Davey-Stewartson equations.Dromion-like nonlinear localized structures(high-dimensional Optical solitons) excited from a continuous wave badckground and decaying in all spatial directions are predicted through the interaction between a wavepacket superposed by short-wavelength components and a long-wavelength mean field generated by an optical rectification.     

Optimized all-optical amplitude reshaping by exploiting nonlinear phase shift in fiber for degenerated FWM

We describe a novel performance optimization method for all-optical amplitude reshaping via degenerated four-wave mixing(FWM) in highly nonlinear optical fiber.The proposed optimization method is achieved by judiciously configuring the FWM operational condition and exploiting the nonlinear phase shift induced by self-and cross-phase modulations to properly influence the FWM conversion efficiency.Through the proposed scheme,fully functional and prevailing reshaping performance,including significant amplitude jitter suppression and extinction ratio improvement,is obtained within a single FWM stage.Results of the present theoretical calculation and numerical simulation verify the feasibility and advantages of the proposed scheme.     

All-optical scheme for detecting the possible Majorana signature based on QD and nanomechanical resonator systems

Majorana fermions(MFs) are exotic particles that are their own anti-particles. Currently, the search for MFs occurring as quasiparticle excitations in condensed matter systems has attracted widespread interest, because of their importance in fundamental physics and potential applications in topological quantum computation based on solid-state devices. Motivated by recent experimental progress towards the detection and manipulation of MFs in hybrid semiconductor/superconductor heterostructures, in this review, we present a novel proposal to probe MFs in all-optical domain. We introduce a single quantum dot(QD), a hybrid quantum dot-nanomechanical resonators(QD-NR) system, and a carbon nanotube(CNT) resonator implanted in a single electron spin system with optical pump-probe technology to detect MFs, respectively. With this scheme, a possible Majorana signature is investigated via the probe absorption spectrum and nonlinear optical Kerr effect, and the coupling strength between MFs and the QD or the single electron spin is also determined. In the hybrid QD-NR system, vibration of the NR will enhance the nonlinear optical effect, which makes the MFs more sensitive for detection. In the CNT resonator with a single electron, the single electron spin can be considered as a sensitive probe, and the CNT resonator behaved as a phonon cavity is robust for detecting of MFs. This optical scheme will provide another method for the detection MFs and will open the door for new applications ranging from robust manipulation of MFs to quantum information processing based on MFs.     

Conditions for formation and trapping of the two-ion Coulomb cluster in the dissipative optical superlattice

Conditions have been studied under which a polychromatic optical superlattice can form and trap the Coulomb cluster of two strongly interacting ions.In our previous work(Krasnov I V and Kamenshchikov L P 2014 Opt.Comm.312 192)this new all-optical method of obtaining and confining the Coulomb clusters was demonstrated by numerical simulations for special values of the optical superlattice parameters and in the case of Yb ions.In the present paper the conditions are explicitly formulated,under which the long-lived two-ion cluster in the superlattice cell is formed.The peculiarity of these conditions is the renormalization of the ion–ion Coulomb interaction.Notably,the renormalized Coulomb force is determined by the effective charge which depends on the light field parameters and can strongly differ from the "bare"ion charge.This result can be accounted for by the combined manifestation of the quantum fluctuations of optical forces,nonlinear dependence of these forces on the velocity,and non-Maxwellian(Tsallis type) velocity distribution of the ions in the optical superlattice.Explicit analytical formulas are also obtained for the parameters of the optical two-ion cluster.     

Theoretical study on controlling nonlinear behaviors of a coupled-cavity VCSEL by external optical injection

A master-slave configuration used to control the nonlinear behaviors arising in a vertical cavity surface emitting laser (VCSEL) with strong external optical feedback is established. In terms of bifurcation diagram, time and frequency domain, the influence of the continuous optical injection from the master VCSEL on the nonlinear characteristics of the slave is investigated theoretically. For relatively weak injection, the slave still keeps its intrinsic nonlinear state. With increasing the injection strength, these nonlinear behaviors evolve to periodic fluctuation, and at last are replaced by the steady-state (e.g. the critical injection parameter for steady-state is 1.2 when external cavity's reflectivity and length are 4% and 4 cm, respectively). During this evolution the bifurcation-contraction phenomena are also observed.     

Periodicity Characteristic of TOAD's Switching Window

1 IntroductionThere are a variety of all-optical demultiplexing schemes for OPtical time divisionmultiplexing (OvuM) system, such as nonlinear optical loop horror (NOLM)[IJ,terahertz optical asyrnxnetric demultiplexer (TOAD)[2], four wave ndking (aaM) offiber or semiconductor optical amplifier (~)[3'4), etc. Axnong them, the terahertzoptical asymmetric demultiplexer (TOAD) has advantages of requirement for shorterlength of fiber and lOWer energy of control pulse, no dispersion and walk…     

Clock recovery from NRZ data at 10 Gb/s using SOA loop mirror and mode-locked fiber ring laser based on SOA

All-optical clock recovery from non-return-to-zero (NRZ) data using an semiconductor optical amplifier(SOA) loop mirror and a mode-locked SOA fiber laser is firstly schematically explained and experimentally demonstrated at 10 Gb/s. Furthermore, the pulse quality of the recovered clock is effectively improved by using a continuous-wave (CW) assist light in the gain region of SOA, through which the amplitude modulation is reduced from 57.2% to 8.47%. This scheme is a promising method for clock recovery from NRZ data in the future all-optical communication networks.     

Clock recovery from NRZ data at 10 Gb/s using SOA loop mirror and mode-locked fiber ring laser based on SOA

All-optical clock recovery from non-return-to-zero (NRZ) data using an semiconductor optical amplifier (SOA) loop mirror and a mode-locked SOA fiber laser is firstly schematically explained and experimentally demonstrated at 10 Gb/s. Furthermore, the pulse quality of the recovered clock is effectively improved by using a continuous-wave (CW) assist light in the gain region of SOA, through which the amplitude modulation is reduced from 57.2% to 8.47%. This scheme is a promising method for clock recovery from NRZ data in the future all-optical communication networks.     

All-optical prefix tree adder with the help of terahertz optical asymmetric demultiplexer

We propose and describe an all-optical prefix tree adder with the help of a terahertz optical asymmetric demultiplexer (TOAD) using a set of optical switches. The prefix tree adder is useful in compound adder implementation. It is preferred over the ripple carry adder and the carry lookahead adder. We also describe the principle and possibilities of the all-optical prefix tree adder. The theoretical model is presented and verified through numerical simulation. The new method promises higher processing speed and accuracy. The model can be extended for studying more complex all-optical circuits of enhanced functionality in which the prefix tree adder is the basic building block.