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In this paper, we propose an N -bit optical digital-to-analog converter (DAC) by integrating N pairs of 2 × 2 phase change based on-chip photonic switches and 2 × 2 multimode interference (MMI) splitters. An on-chip photonic switch is constructed by integrating a wavelength-selectable racetrack micro-ring resonator with the phase change chalcogenide Ge2Sb2Se4Te (GSST). The GSST-integrated switch utilizes a racetrack resonator configuration for performing the accurate modulation of the resonant wavelength to prevent intercoupling between adjacent units. In order for electrothermal heating of the GSST film to trigger its phase transition for switchable control, an indium tin oxide heater with a bowtie-shaped structure is integrated into the racetrack resonator. Using numerical calculations, we demonstrate that an 8 V voltage pulse at a duration of 300 ns, with an energy consumption of 18.45 nJ, could change the optical state from an OFF state to an ON state. Another 6 V voltage pulse of 250 ns duration, followed by a 4 V pulse of varying duration, with a total energy consumption of 34.78 nJ, can switch the optical state from an ON state to an OFF state. The asymmetric structure of the 2 × 2 MMI shows ultra-high transmittance approaching 50% in the through port (connected to the next order of MMI), enabling the creation of multistage cascaded MMI splitters with an output light power ratio close to 50%. Our results show that this configuration potentially offers a feasible solution for applications of optical DACs. [ABSTRACT FROM AUTHOR]

A monolayer metamaterial consisting of a rectangle graphene strip and four L-shaped graphene blocks was proposed to achieve a quintuple plasmon-induced transparency (quintuple-PIT). The numerical simulation results based on the finite difference time domain method agree well with the calculated results of the coupled mode theory. By modulating the Fermi energy level of graphene, an octuple-frequency asynchronous switch and a sextuple-frequency synchronous switch are designed and studied, which have excellent amplitude modulation degree (up to 97.7%), extinction ratio (up to 16.41 dB), insertion loss (low to 5.4%), and dephasing time(low to 3.86 ps). Furthermore, the results show that the proposed metamaterials has polarization-sensitive characteristics due to their non-central symmetry. Further research shows that the group index is as high as 604 which has a good slow light effect and can be used for optical storage. Hence, the quintuple-PIT proposed structure in this paper has good application value in the expansion of multi-function optical switches and the research of high-quality optical memory. [ABSTRACT FROM AUTHOR]

Self-powered broadband photodetectors have attracted great interest due to their applications in biomedical imaging, integrated circuits, wireless communication systems, and optical switches. Recently, significant research is being carried out to develop high-performance self-powered photodetectors based on thin 2D materials and their heterostructures due to their unique optoelectronic properties. Herein, a vertical heterostructure based on p-type 2D WSe2 and n-type thin film ZnO is realized for photodetectors with a broadband response in the wavelength range of 300–850 nm. Due to the formation of a built-in electric field at the WSe2/ZnO interface and the photovoltaic effect, this structure exhibits a rectifying behavior with a maximum photoresponsivity and detectivity of ∼131 mA W−1 and ∼3.92 × 1010 Jones, respectively, under an incident light wavelength of λ = 300 nm at zero voltage bias. It also shows a 3-dB cut-off frequency of ∼300 Hz along with a fast response time of ∼496 μ s, making it suitable for high-speed self-powered optoelectronic applications. Furthermore, the facilitation of charge collection under reverse voltage bias results in a photoresponsivity as high as ∼7160 mA W−1 and a large detectivity of ∼1.18 × 1011 Jones at a bias voltage of −5 V. Hence, the p-WSe2/n-ZnO heterojunction is proposed as an excellent candidate for high-performance, self-powered, and broadband photodetectors. [ABSTRACT FROM AUTHOR]

A terahertz constant frequency reconfigurable metasurface based on tunable electromagnetically induced transparency (EIT)-like property was designed, whose transparency window frequency did not vary with Fermi energy. This structure was composed of two single-layer graphene resonators, namely, left double big rings and right double small rings. An evident transparency window (EIT-like phenomenon) was caused by the near-field coupling between bright modes of the two resonators in the transmission spectrum, in which amplitude over 80% was acquired at 1.98 THz. By individually reconfiguring the Fermi energy of each resonator, the EIT-like effects, transparency window amplitude, modulation speed and group delay could be actively controlled while the frequency of EIT-like window remained constant. Significantly, the transparency window was fully modulated without changing the frequency, and the maximum modulation depth reached 78%. Furthermore, the modulation speed also increased because the total graphene area A was effectively reduced in the proposed structure. Compared with other metasurface structures, the modulation properties of the proposed structure showed higher performance while the EIT-like window frequency remained static. This research provides an alternative method for developing constant frequency reconfigurable modulation terahertz devices (such as optical switches and modulators), as well as a potential approach for miniaturization of terahertz devices. [ABSTRACT FROM AUTHOR]

Reconfigurable waveguide components are promising building blocks for photonic neural networks and as an optical analogue to field-programmable gate arrays. By changing the effective index of the waveguide, reconfigurable waveguide components can achieve on-chip light routing and modulation. In this paper, we design and demonstrate an Sb2S3-reconfigurable InP membrane Machâ€"Zehnder interferometer (MZI) on a silicon substrate. Sb2S3, which has tunable refractive index and low absorption in the near-infrared spectrum, was patterned on the InP waveguide MZIs to make an optical switch in the telecoms conventional-band. By laser induced crystallisation of the Sb2S3, it was possible to control interference in the MZI and achieve 18 dB on/off switching at 1540 nm. Laser reamorphisation and reversible switching of the Sb2S3 layer resulted in damage to the waveguide structure. However, simulations show that transition metal di-chalcogenide two-dimensional crystal layers can act as efficient thermal barriers that prevent thermal damage to the waveguide during laser amorphisation. Therefore, combining Sb2S3 with InP waveguides seems to be a feasible approach to achieve low-loss reprogrammable waveguide components for on-chip photonics routing and neural networks. [ABSTRACT FROM AUTHOR]

The interaction between quantum emitters and photons in the strong coupling regime has received much attention in recent years due to its important position in fundamental and applied physics. Transition metal dichalcogenides (TMDs) have become ideal candidates for the study of strong light-matter interactions due to the formation of in-plane excitons exhibiting giant oscillator strength with narrow-band, well-pronounced optical transitions, which can be readily coupled to various optical excitations. The study of TMD-based strong coupling are leading to striking discoveries in many applications such as polariton condensation, lasing, all-optical switches and quantum information processing. This review summarizes the recent advances in strong coupling of TMD excitons with different types of nanostructures including traditional optical cavities, plasmonic nanocavities and all-dielectric nanoresonators. We finally discuss the future perspectives and possible directions on the TMD-based strong excitonâ€"photon interactions in strong coupling regime. [ABSTRACT FROM AUTHOR]

The magnitudes of coupling strength play an important role in various resonant phenomena such as Fano resonances (FRs). However, the coupling strength within the FRs using dielectric metasurfaces cannot be easily manipulated once they have been made. In this paper, toroidal FR is excited using the silicon metasurface with symmetry-breaking nanocylinders. Inserting a graphene layer with an ion-gel top gate onto the silicon metasurface, actively tunable response of a toroidal FR resulting from the manipulated coupling strength and the phase shift between two states. The hybrid graphene-silicon metasurface realize tunable Fano parameter (q) from âˆ'1.38 to âˆ'1.85 with applied voltage ranging from 0 to 2 v. Theoretical results predicted that higher q values are reachable relying on the hybrid graphene-silicon metasurface. The high-quality(Q)-factor (∼444) tunable FR of metasurface in the near-infrared region is observed. By applying a bias voltage to graphene obtain a blueshift of resonant wavelength (∼4 nm) with a maximum change of transmission spectrum peak up to 30%. These results have potential in high-efficient tunable electro-optic modulators, near-infrared optical switches, etc. [ABSTRACT FROM AUTHOR]

Traditional optical switches relying on the weak, volatile thermo-optic or electro-optic effects of Si or SiN waveguides show a high consumption and large footprint. In this paper, we reported an electric-driven phase change optical switch consisting of a Si waveguide, Ge2Sb2Te5 (GST) thin film and graphene heater suitable for large-scale integration and high-speed switching. The reversible transition between the amorphous and crystalline states was achieved by applying two different voltage pulses of 1.4 V (SET) and 4 V (RESET). The optical performance of the proposed switch showed a high extinction ration of 44–46 dB in a wide spectral range (1525–1575 nm), an effective index variation of Δneff = 0.49 and a mode loss variation of Δα = 15 dB μm−1 at the wavelength of 1550 nm. In thermal simulations, thanks to the ultra-high thermal conductivity of graphene, the proposed switch showed that the consumption for the SET process was only 3.528 pJ with a 1.4 V pulse of 5 ns, while a 4 V pulse of 1.5 ns was needed for RESET process with a consumption of 1.05 nJ. Our work is helpful to analyze the thermal-conduction phase transition process of on-chip phase change optical switches, and the design of the low-energy-consumption switch is conducive to the integrated application of photonic chips. [ABSTRACT FROM AUTHOR]

We investigate magneto-optical rotation (MOR) of surface plasmon polaritons (SPPs) at the interface of a metal and a four-level atomic system. The MOR of SPPs can be controlled and modified with the intensity and frequency of the applied fields. We show the birefringence enhancement of the weak probe fields propagating through the atomic medium in the presence of the static magnetic field. The external magnetic field has a vital role in the generation and control over the MOR of SPPs. The MOR completely stops when either the external magnetic field or the probe field or both are tuned to resonance. A pretty behavior of MOR of SPPs is observed for a specific set of control field frequency. The enhanced MOR of SPP has significant applications in atomic spectroscopy, optical communication, nano-photonics, optical switches, and precise measurement. [ABSTRACT FROM AUTHOR]

The all-optical switch is one of the key elements of all-optical high speed information networks and computing systems. Their bending behavior, actuated by optical gradient forces, dramatically influences their switching performance and is therefore the research topic of this paper. The coupled behavior between optical gradient forces and the bending deflection is taken into account in the present model. The effects of the effective refractive index and the stretching induced by bending are included and their influences on the resonance wavelength shift of the signal light are discussed. Results show that the resonance wavelength shift increases almost linearly at first, and then increases suddenly as the circulating power increases. The resonance wavelength shift increases as the central angle of the suspended part increases, while it decreases with the initial gap. The present theoretical model may be helpful when designing all-optical switches. [ABSTRACT FROM AUTHOR]

In this work, we propose a 10 μm-scale spin-based sensor structure, which mainly consists of a nanowire (NW) ring resonator laser, nitrogen-vacancy (NV) defects in a nanodiamond (ND) and a microwave (MW) antenna. The NW laser was bent into a ring with a gap to pump the NV defects in the ND which was assembled in the gap with the diameter of ∼8 μm. And the fluorescent light of NV defects was enhanced by the NW ring resonator about 8 times. Furthermore, the NW laser pulse was produced by the optical switch and a simple plus-sequences was designed to get the Rabi oscillation signal. Based on the Rabi oscillation, a Ramsey-type sequence was used to detect the magnetic field with the sensitivity of 83 nT √Hz−1 for our 10 μm-scale spin-based sensor structure. It proves the spin state in our structure allows for coherent spin manipulation for more complex quantum control schemes. And our structure fulfills the fundamental requirements to develop chip-scale spin-based sensors. [ABSTRACT FROM AUTHOR]

We investigate a graphene-coated nanowire waveguide (GCNW) composed of two suspended wedge porous silicon nanowires and a thin Ag partition. The plasmonic characteristics of the proposed structure in terahertz (THz) frequency band are simulated by the finite element method (FEM). The parameters including the gap between the nanowires and Ag partition, the height of the nanowire, the thickness of the Ag partition, and the Fermi level of graphene, are optimized. The simulation results show that a normalized mode field area of ∼ 10−4 and a figure of merit of ∼ 100 can be achieved. Compared with the cylindrical GCNW and isolated GCNW, the proposed wedge GCNW has good electric field enhancement. A waveguide sensitivity of 32.28 is obtained, which indicates the prospects of application in refractive index (RI) sensing in THz frequency band. Due to the adjustable plasmonic characteristics by changing the Fermi level (EF), the proposed structure has promising applications in the electro-optic modulations, optical interconnects, and optical switches. [ABSTRACT FROM AUTHOR]

All-optical modulation is experimentally demonstrated in a microfibre coil resonator (MCR) functionalized with black phosphorus (BP) nanosheets (BP-MCR). The BP nanosheets is deposited onto microfibre and then microfibre is wrapped on a PMMA rod covered with UV-curable low refractive index polycarbonate (PC) resin. The BP-MCR modulation properties are regulated based on BP absorption, photo-thermal and optical Kerr effects. The resonance wavelength and extinction ratio responsivity to incident pump power can attain ∼0.033 nm mW−1 and ∼0.180 dBm mW−1, while the averaged rising/falling response time is ∼9.58/8.53 ms. The device could find applications as all-optical modulator, optical switch or tunable optical filter. [ABSTRACT FROM AUTHOR]

On-chip photonics devices relying on the weak, volatile thermo-optic or electro-optic effects of silicon usually suffer from high insertion loss (IL) and a low refractive index coefficient. In this paper, we designed two novel 1 × 1 and 1 × 2 phase-change optical switches based on a signal-mode Si waveguide integrated with a Ge2Sb2Te5 (GST) top clad layer, respectively. The three-state switch including amorphous GST (a-GST), face centered cubic crystalline phase (FCC-GST) and hexagonal crystalline phase (HCP-GST) operated by utilizing the dramatic difference in the optical constants between the amorphous and two crystalline phases of GST. In the case of the 1 × 1 optical switch, an extinction ratio (ER) of 8.9 dB and an extremely low IL of 0.8 dB were achieved using an optimum GST length of only 2 μm. While for the 1 × 2 optical switch, low ILs in the range of 0.15 ∼ 0.35 dB for both 'cross' (a-GST) and 'bar' (FCC-GST and HCP-GST) states were also obtained. Additionally, we found that both ILs and mode losses of the switch with HCP-GST were about half lower than those with FCC-GST, which means FCC-GST could be instituted by HCP-GST in the traditional ovonic switch with the consideration of low loss. This research provides the fundamental understanding for the realization of low loss and non-volatile Si-GST hybrid optical switches, with potential for future communication networks. [ABSTRACT FROM AUTHOR]

We report the diversiform propagation of hollow Gaussian beam clusters in non-linear media with self-induced parabolic potentials. It is found that the beam cluster can present various periodically varying propagation forms by tuning the initial incident conditions. We roughly classify the initial incident cases into five types—parallel incidence, spiraling incidence, convergent incidence, divergent incidence, and mixed incidence—ground on the introduced transverse velocity parameter. The propagation characteristics, such as the evolutions of the intensity patterns, the projection trajectories, the rotating angle, the angular velocity, the center distance, the size and the phase distribution of the beam cluster, are illustrated graphically in detail. These novel forms of beam clusters presented in this paper possess complicated and unique spatial distribution and controllable propagation parameters for their potential applications in all-optical networks, optical switch, optical tweezers, multi-particle trapping, and other related fields. [ABSTRACT FROM AUTHOR]

We theoretically explore optical bistability for the possible signature of all-optical switching and their performance in a hybrid quantum optomechanical system comprising of two semiconductor microcavities coupled optically. One of the cavity is driven by an external amplitude-modulated pump laser while the second cavity, which contains a quantum dot (QD), is indirectly driven by light transmitted from the first cavity and a transverse optical field. The generated bistable behavior due to optomechanical nonlinearity shows a typical optical switching behavior and it can be controlled by changing the laser power, QD cavity coupling, modulating amplitude/frequency and the optomechanical coupling. A clear signature of energy exchange between the mechanical and optical modes is visible from the mechanical displacement spectrum. These results suggest that the present system can be used in sensitive optical switches and optical sensors. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) with different geometry have been extensively investigated for several decades owing to their unique optical properties which provide efficient focusing, absorption, scattering, waveguiding and directivity at the nanoscale. The development of an efficient photonic device requires good antenna, as well as resonator properties, that is where hybrid metal-semiconductor nanostructure comes in to play. This work is devoted to the numerical modeling of the optical properties of GaP nanowire (NW) with Ga plasmonic droplet. The modeling results demonstrate that such a self-assembled hybrid nanostructure provides polarization switchable focusing of light at the metal–semiconductor interface, effective beam steering, and emission confinement. Numerical simulation estimates that the field can be focused tenfold at the metal–semiconductor interface providing pathway for excitation of the quantum emitter or hot electron injection. The hybrid structure can also be used to turn the light efficiently without the need to bend the NW acting as a waveguide providing four times more efficient beam steering compare to the NW without the Ga NP. We demonstrate that the light intensity varies 16 times at the interface for S and P polarization which can be utilized for optical switching in photonic or data processing applications. Finally, we discuss the architecture of the devices for the future applications based on the investigated hybrid structure. [ABSTRACT FROM AUTHOR]

We propose a slot waveguide metal Bragg grating, which can continuously convert the phase difference between two beams of light into their varying reflectivity and transmittivity. Two types of switches based on two-beam interference were designed by optimizing the geometric parameters of metal gratings. Thanks to the localized surface plasmon resonance and the strong optical confinement in slot, both types of switches are very compact. The finite element method simulation result shows the grating's good performance to controlling light reflection and transmission, especially for Type II switches. The on-state reflectivity and off-state transmittivity of Type II switches are more than 75% and 88% respectively, with both the reflection and transmission switching depths more than 93%, in a 120 nm wide wavelength range centered at 1550 nm. Moreover, slot waveguide metal Bragg gratings combined with phase modulators can be used as reflectivity-adjustable reflectors, which are expected to be promising elements for on-chip laser Q-switching. The proposed slot waveguide metal Bragg grating is expected to be used for photonic integrated circuits and applications which require broadband and high-efficiency on-chip optical switching and adjustable reflections. [ABSTRACT FROM AUTHOR]

We provide an approach to realize an optical switch using an induced transparency phenomenon in double-cavity structures. Our system consists of two directly coupled cavities, each coupled to a different waveguide. The system is pumped by a control field and a signal field propagating in the waveguides. We analyze the excitation spectra of the cavities, as well as corresponding transmission and reflection coefficients for the signal field. We find that induced transparency or an absorption phenomenon for the signal field can be established in this system, depending on the parameters of the control field. Thus, the transport properties for the signal field are highly controllable. Under appropriate parameters the system can behave as a nearly perfect optical switch for the signal field. The influence of dissipations on the efficiency of the switch is also discussed. The device studied here is suitable for on-chip integrations, and may have broad applications in future quantum networks. [ABSTRACT FROM AUTHOR]

Cd3As2, as a three-dimensional (3D) topological Dirac semimetal, has attracted wide attention due to its unique physical properties originating from the 3D massless Dirac fermions. While many efforts have been devoted to the exploration of novel physical phenomena such as chiral anomaly and phase transitions by using bulk crystals, the development of high-quality and large-scale thin films becomes necessary for practical electronic and optical applications. Here, we report our recent progress in developing single-crystalline thin films with improved quality and their optical devices including Cd3As2-based heterojunctions and ultrafast optical switches. We find that a post-annealing process can significantly enhance the crystallinity of Cd3As2 in both intrinsic and Zn-doped thin films. With excellent characteristics of high mobility and linear band dispersion, Cd3As2 exhibits a good optical response in the visible-to-mid-infrared range due to an advantageous optical absorption, which is reminiscent of 3D graphene. It also behaves as an excellent saturable absorber in the mid-infrared regime. Through the delicate doping process in this material system, it may further open up the long-sought parameter space crucial for the development of compact and high-performance mid-infrared ultrafast sources. [ABSTRACT FROM AUTHOR]

A computer simulation has been carried out to analyze and explain the specific features of the switch-on process in super-high-voltage (18 kV class) optically triggered 4H-SiC thyristors. It is shown that the previously experimentally observed two-stage character of the switch-on processes can be understood in a one-dimensional approach. The two-stage turn-on of the 18 kV structures is accounted for by the rather slow current rise in the structure with a very wide (160 µm) blocking base. In full agreement with the experimental results, a simulation in the frame of the same approximations demonstrated that, in the 12 kV class thyristor structures with a blocking base thickness of 90 µm, the current increases monotonically during the switch-on process. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the optical transmission properties of perfect and defective two-segment-connected triangular waveguide networks (2SCTWNs) and find that after introducing defects in networks, many groups of transparent extreme narrow photonic passbands (ENPPs) will be created in the middle of the transmission spectra, the number for each group and the group number of ENPPs can be adjusted by the matching ratios of waveguide length (MRWLs), the number of defects, and the number of unit cells of 2SCTWNs. The influences of MRWL, number of defects, and number of unit cells on the number, width, and position of these ENPPs are researched and a series of quantitative rules and properties are obtained. It may be useful for the designing of high-sensitive optical switches, wavelength division multiplexers, extreme-narrowband filters, and other correlative waveguide network devices. [ABSTRACT FROM AUTHOR]

Focusing and guiding light into semiconductor nano-structures can deliver revolutionary concepts for photonic devices, which offer a practical pathway towards next-generation power-efficient optical networks. In this review, we consider the prospects for photonic switches using semiconductor quantum dots (QDs) and photonic cavities which possess unique properties based on their low dimensionality. The optical nonlinearity of such photonic switches is theoretically analysed by introducing the concept of a field enhancement factor. This approach reveals a drastic improvement in both power-density and speed, which is able to overcome the limitations that have beset conventional photonic switches for decades. In addition, the overall power consumption is reduced due to the atom-like nature of QDs, as well as the nano-scale footprint of photonic cavities. Based on this theoretical perspective, the current state-of-the-art QD/cavity switches are reviewed in terms of various optical nonlinearity phenomena that have been utilized to demonstrate photonic switching. Emerging techniques, enabled by cavity nonlinear effects such as wavelength tuning, Purcell-factor tuning and plasmonic effects, are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, illusion optics theory is employed to form Bragg gratings in an optical waveguide in order to design an optical switch. By using an illusion device at a certain distance from the waveguide, the effective refractive index of the waveguide is remotely modulated, turning the waveguide into a distributed Bragg reflector (DBR) which blocks the waves at a stop band. By removing the illusion device, the waves propagate through the waveguide again. In addition, this method is used to remotely tune DBR optical properties such as resonant frequency and bandwidth in a wide range, which leads to a tunable filter for optical switching applications. Finally, using an illusion device at a distance, an optical cavity is created by inserting defects remotely in a DBR without any physical damage in the primary device. [ABSTRACT FROM AUTHOR]

The phase properties of the transmitted light from one-dimensional coupled-cavity photonic crystal structures with the form (HLκ A(LH)κ, where A contains N micro-cavities, are studied. It is found, for κ ≥ 1, that the transmission phase changes drastically around each transmitted peak and the corresponding phase shift is approximately equal to π. Moreover, the transmitted power is almost zero during the π phase transition between neighboring transmission maxima. These properties show great promise for inverse phase devices, optical switches, and, in particular, binary differential phase-shift-keying (2DPSK) format data transmission, where a π phase transition is required. As an example, a 2DPSK modulator is demonstrated. [ABSTRACT FROM AUTHOR]

We propose a new type of optical switch based on a ferroelectric. It is based on the gap which exists for waves propagating from a dielectric to a ferroelectric material. This gap depends on the polarization of the ferroelectric. We show that it can be shifted by means of a control electromagnetic pulse in such a way that the material becomes transparent. This device would produce a shift in a time much shorter than the relaxation time of the ferroelectric (1 ns). Estimates are given for a real material. [ABSTRACT FROM AUTHOR]

Two kinds of plasmonic lenses are proposed based on phase compensation. Each kind of plasmonic lens is comprised of four sets of nanohole arrays, and two sets of face-to-face nanohole arrays are planar symmetric. The adjustment of separation and the rotation angle of holes compensates, respectively, for the phase difference of the surface plasmon polaritons reaching to the focal spot. The different design principles make the proposed plasmonic lenses show the different polarization dependence focusing. Two or four foci of the first kind of plasmonic lens and two controllable foci focusing of the second kind of plasmonic lens can be utilized as optical switch and logic judgment. Theoretic analysis, numerical calculations and experiment measurement verify the focusing performance of our proposed plasmonic lenses. The focusing functionality and versatility of our proposed structures are helpful for extending the applications of plasmonic lenses in integrated optics. [ABSTRACT FROM AUTHOR]

We describe optical switching in solutions of semiconductor nanocrystals illuminated by a 404 nm continuous wave laser source, driven by the formation of a micro-bubble of solvent vapor in the solution. Low boiling solvents such as hexane show an oscillatory modulation of transmitted light intensity (period ∼4 s) while solvents with intermediate boiling points such as toluene give a stable switching response. An on/off ratio of 83% is observed in the transmitted pump beam. Using this, a pump beam (404 nm, 80 mW continuous wave) was shown to reversibly switch the state of a probe laser (630 nm, 5 mW continuous wave). This switch thus serves as an optical analog of an electronic transistor and demonstrates the potential for all optical switching of low power light beams. Further, all optical universal logic gates, NAND and NOR, were also demonstrated using the micro-bubble switch. [ABSTRACT FROM AUTHOR]

Electromagnetically induced absorption (EIA) of cesium atoms exposed to counter-propagating light waves with orthogonal linear polarizations is studied. Probe beam transmission through a buffer gas-filled vapor cell is monitored as a function of a static magnetic field applied parallel to the wave vectors. The light waves are tuned to a single dipole transition Fg → Fe in the D1 line (λ = 894.6 nm). The proposed magneto-optical configuration helps overcome a long-standing problem in obtaining high-contrast EIA resonances in conjunction with narrow linewidths. Our experiments demonstrate EIA contrast with respect to a broad Doppler absorption background (CD) as high as 1630%. Thus, a high value of CD means that background absorption is almost absent, and the vapor cell transmission profile represents only a single narrow resonance. This result is unique for EIA as well as for electromagnetically induced transparency (EIT) effects, because usually in a resonant medium, narrow EIT or EIA resonances are accompanied by natural-linewidth or other broad spectral features, even in the case of cold atoms. The resonance contrast with respect to the light transmission background (Cback) is also high enough, reaching 75% in the experiments. The full width at half maximum of the narrowest observed EIA is approximately 0.77 mG (0.7 × 0.77 = 540 Hz in the frequency domain). The considered simple scheme has good prospects for the development of various quantum magneto-optical devices such as optical switches and atomic magnetometers. [ABSTRACT FROM AUTHOR]

We theoretically investigate the strong coupling in silver-molecular J-aggregates-silver structure sandwiched between two dielectric media by using classical methods. Fresnel equations are employed to solve our proposed structure. The results show that both the reflection and transmission spectra show a Rabi splitting-like line shape, revealing the strong coupling phenomenon. Furthermore, the radiative angle versus incident wavelength exhibits a Fano line shape. The strong coupling phenomenon can be well tuned by controlling the surface plasmon excitation, such as the incident angle and the thickness of the silver films. Our structure has potential applications in quantum networks, optical switches, and so on. [ABSTRACT FROM AUTHOR]

As a unique two-dimensional material, few-layered black phosphorus (BP) nanosheets have shown promising applications in electronics and optoelectronics. Black phosphorus quantum dots (BPQDs) have attracted attention due to the unique properties of BP combined with the edge effects. In this paper, we report on the all-optical application of BPQD based on its nonlinear Kerr effect. BPQDs were synthesized using a liquid exfoliation method combined with probe sonication and bath sonication. BPQD deposited on the microfiber as an optical device was demonstrated as the Kerr switcher with extinction ratio of 20 dB and four-wave mixing based wavelength converter with −40 dB conversion efficiency. These findings suggest that BPQD-based novel nonlinear photonics devices could be further developed in the applications of next generation high-speed optical communication. [ABSTRACT FROM AUTHOR]

In this study, we aimed at optimizing the nonlinear properties of the guiding structure of graphene surface plasmon polaritons. The structure is a graphene–metal hybrid waveguide with applicable mode confinement. Focusing electromagnetic power in the graphene sheet improves the harmonic conversion efficiency (0.2% (−27 dB)) and high self-phase modulation. The third harmonic generation phase-matching condition was satisfied in three-dimensional simulations for longer harmonic generation length. Low loss performance is vital for devices that operate in the terahertz regime (0.3–30 THz), because of the low efficiency offered by the available terahertz pulse generation methods. In this study, low loss propagation was achieved by engineering the chemical potential of graphene. Finally, a frequency-selective all-optical switch was designed by placing a subwavelength resonator in the waveguide. Self-phase modulation enabled optical control of the frequency-selective switch. [ABSTRACT FROM AUTHOR]

Atom–nanowire coupling system is a promising platform for optical quantum information processing. Unlike the previous designing of optical switch and transistor requiring a dedicated multi-level emitter and high fineness microcavity, a new proposal is put forward which contains a single two-level atom asymmetrically coupled with two nanowires. Single-emitter manipulation of photonic signals for bilateral coherent incident is clear now, since we specify atomic saturation nonlinearity into three contributions which brings us a new approach to realizing light-controlled-light at weak light and single-atom levels. An efficient optically controllable switch based on self-matching-induced-block and a concise optical transistor are proposed. Our findings show potential applications in full-optical devices. [ABSTRACT FROM AUTHOR]

We investigate the tunable bistable behavior of a hybrid nano-electro-optomechanical system (NEOMS) composed of S-shaped in the presence of two-level atoms, trapped inside a Fabry–Pérot cavity, and driven by a strong driving field and a weak probe field. The bistable behavior of the steady-state photon number and the mechanical steady-state positions are discussed. Further, we tune bistability by tuning all the coupling frequencies involved in the system and amplitude of the driving field. The present study provides the possibility of realization of a controllable optical switch depending on atom-field coupling, optomechanical coupling, electrostatic Coulomb coupling, and threshold power. In addition, we discuss that the non-linear effect of the hybrid NEOMS generates the four-wave mixing (FWM) process. Moreover, we show that the FWM process can be suppressed by the atom-field detuning and cavity-field detuning, which exhibits low photon transmission. [ABSTRACT FROM AUTHOR]

Multiphoton excitations and nonlinear optical properties of exciton states in GaAs/AlxGa1−xAs coupled quantum well structure have been theoretically investigated under the influence of a time-varying high-intensity terahertz (THz) laser field. Non-perturbative Floquet theory is employed to solve the time-dependent equation of motion for the laser-driven excitonic quantum well system. The response to the field parameters, such as intensity and frequency of the laser electric field on the state populations, can be used in various optical semiconductor device applications, such as photodetectors, sensors, all-optical switches, and terahertz emitters. [ABSTRACT FROM AUTHOR]

We study a two-cavity optomechanical system in which one cavity (A) encloses a mechanical resonator and the other cavity (C) encloses a two-level atom are, respectively, driven by a strong pump and a weak probe fields. In addition to a direct pathway, the excitations in cavity C and the enclosed atom can also be caused through an indirect pathway. The interference between the two possible routs for excitations produces a controllable transparency window in the probe transmission spectrum of cavity C. The coupling strength between cavity C and the atom works as an additional parameter to the coupling strength between the two cavities which helps to manipulate the dynamical properties of the system and hence to control the width of the transparency window. Furthermore, we show that the single setup can be used to produce an optical switch from two different physical behaviors of the model, and to realize subluminal and superluminal behaviors in the output spectrum at probe frequency of cavity C. [ABSTRACT FROM AUTHOR]

Transversely localized low-threshold and adjustable lasers based on self-collimation (SC) modes in two-dimensional photonic crystals (PhCs) have been proposed and investigated. The low-threshold property of lasing is from its slow group velocity, while the transverse-localization property is from the flat SC equal-frequency contour that cuts through the whole Brillouin zone. Numerical results have confirmed that SC lasing modes can be controlled by gain distributions and could be stable with certain cavity lengths. The width of the narrowest lasing mode could be smaller than two lattice constants in the transverse direction. The Q-factor of the lasing modes increases linearly with the PhC length, showing potential for ultra-low-threshold lasing. Such lasing modes could be very robust against different directions of PhC edges. The transversely localized SC lasing modes with low group velocity have versatile usages in photonic circuits, e.g. light sources, signal amplifiers and optical switches. [ABSTRACT FROM AUTHOR]

We present an electrically tunable metasurface which modulates the amplitude of the transmission spectra and works independently of the light polarization. The tunable metasurface comprises circular metal–insulator–metal (MIM) plasmonic resonators, using indium tin oxide (ITO) as a gate-tunable material. The property of the ITO film is tuned by applying a DC bias voltage through a 2D array of DC connections. The transmission amplitude at the resonance wavelength of 1650 nm can be modulated up to 29 dB by applying an electric voltage. The symmetric DC connections on the four sides of the circular MIM resonators enable polarization independence. This active metasurface could work as a signal modulator and an optical switch. [ABSTRACT FROM AUTHOR]

In this paper, the (1+1)-dimensional variable-coefficient complex Ginzburg–Landau (CGL) equation with a parity-time (PT) symmetric potential U(x) is investigated. Although the CGL equations with a PT-symmetric potential are less reported analytically, the analytic solutions for the CGL equation are obtained with the bilinear method in this paper. Via the derived solutions, some soliton structures are presented with corresponding parameters, and the influences of them are analyzed and studied. The single-soliton structure is numerically verified, and its stability is analyzed against additive and multiplicative noises. In particular, we study the soliton dynamics under the impact of the PT-symmetric potential. Results show that the PT-symmetric potential plays an important role for obtaining soliton structures in ultrafast optics, and we can design fiber lasers and all-optical switches depending on the different amplitudes of soliton-like structures. [ABSTRACT FROM AUTHOR]

We theoretically investigate the optical-response properties of the four-mode quadratically coupled optomechanical system (OMS), in which two standard OMSs with quadratic coupling are coupled to each other via a common waveguide. In the presence of a strong control field applied to one cavity and a weak probe field applied to the other, we show that by suitably tuning the system parameters, there appears the normal mode splitting, optomechanically induced absorption, and double or triple electromagnetically induced transparency phenomena in the probe absorption spectrum. In particular, the explicit physical explanations for those fantastic phenomena are detailed discussed. Moreover, we also show that our proposal can be exploited to implement the optical switch as well as the slow and fast light effects. [ABSTRACT FROM AUTHOR]

To promote the future quantum information technologies, we demonstrate an electrically driven optical switch based on quantum interference in a hybrid opto-electromechanical system, which consists of an opto-mechanical cavity and an external electric circuit. The key element of our scheme is a moveable mirror of cavity as a charged mechanical oscillator capacitively coupled to a fixed charged plate in a variable capacitor. By adjusting the voltage of the capacitor, the displacement of the moveable mirror is modulated, then the cavity field can be electrically turned on or off due to the detuning of the cavity. Based on the cavity induced transparency, the transparency window can be electrically switched on or off by turning on or off the cavity field. Therefore, the susceptibility of the medium in the cavity can be electrically controlled, i.e., the scheme of the electrically controlled absorption switching can be demonstrated. This electrically driven optical switch will excite a development trend and implementation prospect towards the integration and miniaturization of quantum module device in a chip. [ABSTRACT FROM AUTHOR]

We present a comprehensive investigation to ascertain the impact of gold and silver films on modifying the quality-factor (Q-factor) of optical Tamm-plasmon (OTP) resonance in a metal-distributed Bragg reflector (M-DBR) geometry. Here, OTP mode is excited using direct incidence of white-light-source at normal incidence as well as oblique incidence on M-DBR geometry. The lifetime of OTP in gold and silver deposited films on DBR mirror was determined from OTP resonance linewidth. The lifetime and the Q-factor of OTP modes are found to depend on DBR bilayers, metal film thickness as well as on different plasmon active metals. This finding would facilitate tuning the Q-factor and consequently, the lifetime of OTP modes for various applications in all-optical switches and modulators. In addition, we discuss the spectral characteristics of OTP modes excited using normal and oblique incident of source. [ABSTRACT FROM AUTHOR]

We present a theoretical study of an optical cavity coupled with single four-level atoms in closed loop formed via applied control lasers. The transmitted probe field from the cavity is analyzed. We show that the electromagnetically induced transparency (EIT) in the cavity and the normal mode splitting will be very different with changing the closed interaction phase and the intensity of the free-space control laser. This coupled cavity–atom system presents a variational double-EIT that comes from modulating the splitting of the dark state, which means that we could realize the gradual transfer between one EIT peak and two EIT peaks by adjusting the applied control lasers, and the normal mode splitting sidebands will shift slightly by changing the free-space control laser. This means that we could control the output cavity probe field more freely and it is easer to realize optical switch controlled by more parameters. We also depict the angular dispersion of the intracavity probe field in different free-space control laser. The large phase shift () of the reflected intracavity probe field will be very useful for optical temporal differentiation and quantum phase gate. [ABSTRACT FROM AUTHOR]

As the fundamental optical properties and novel photophysics of graphene and related two-dimensional (2D) crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches (or saturable absorbers) for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out. [ABSTRACT FROM AUTHOR]

The concept of coherence switches with nanoparticle platonic networks is introduced and analysed. The platonic networks store an initially injected excitation for extremely long durations via the formation of dark states. Switching is achieved by the nano-mechanical arrangements of one site or some part of the network to remove the trapping thus leading to a highly efficient transfer to the target which is irreversibly connected to one site. We present coherence switches based on controlling a cubic network both in the absence and presence of environment and manufacturing/topological noise. [ABSTRACT FROM AUTHOR]

We investigate the self–Kerr nonlinearity of a four-level N-type atomic system in Rb and observe its reversible property with a unidirectional increase in the switching field. For a laser arrangement in which the probe field interacts with the middle two states, the slope and the sign of the self–Kerr nonlinearity around the atomic resonance not only can be changed from negative to positive but also can be changed to negative again with a unidirectional increase in the switching field. Numerical simulations are consistent with the experimental results, and dressed state analysis is presented to explain the experimental results. [ABSTRACT FROM AUTHOR]

A numerical study of graphene plasmons (GPs) propagating along various doping profiles of the graphene sheet is proposed. We show that the GP reflection at an abrupt doping interface is a simple function of the doping difference, consistent with a Fresnel model. In addition, improved transmission is obtained with a tapered interface and we find an optimal size for the transition zone. By considering localized inhomogeneities we describe a Fabry–Perot type cavity leading to an absorption above 60%. Furthermore, an alternative design of a 6 nm length cavity is proposed achieving 100% absorption. These results may lead to novel optical switches, circuits or nano-sensors. [ABSTRACT FROM AUTHOR]

Optical switch fabric plays an important role in building multiple-user optical quantum communication networks. Owing to its self-routing property and low complexity, a banyan network is widely used for building switch fabric. While, there is no efficient way to remove internal blocking in a banyan network in a classical way, quantum state fusion, by which the two-dimensional internal quantum states of two photons could be combined into a four-dimensional internal state of a single photon, makes it possible to solve this problem. In this paper, we convert the output mode of quantum state fusion from spatial-polarization mode into time-polarization mode. By combining modified quantum state fusion and quantum state fission with quantum Fredkin gate, we propose a practical scheme to build an optical quantum switch unit which is block free. The scheme can be extended to building more complex units, four of which are shown in this paper. [ABSTRACT FROM AUTHOR]

We recently introduced a heuristic method for delimiting the stability regions of a three-mode class A laser with three freedom degrees. Here this method is extended to cover the stability conditions of a three-mode class B laser with five freedom degrees. The diagonal arrays of the stability coefficient determinant are taken equal to zero until the determinant vanishes. It then turns out that the diagonal roots correspond to the laser stability boundaries. They form the different kinds of bifurcations that segregate the above-threshold state, with three simultaneous oscillating modes, from the bistability and below-threshold states, with two and no oscillating modes, respectively. The fast optical switches and high optical memories have been designed by exploiting the bistability properties of bifurcations as reported by Perez et al (2007 Opt. Express15 12941–8). [ABSTRACT FROM AUTHOR]

A reflection-type space-division optical switch is theoretically proposed and experimentally demonstrated based on the electrically tuned Goos–Hänchen effect in a symmetrical metal-cladding waveguide which employs the PMN–PT ceramics as the guiding layer. Owing to the high sensitivity of the ultrahigh-order modes, the variation of refractive index and thickness induced by the exertion of the controlled voltage on the PMN–PT ceramics will easily give rise to a change in the position of the reflected light. In the experiment, a three-pinhole array is put in the reflected light path and a one-to-three optical switch is achieved. The switching time for 10%–90% light intensity change and the optical crosstalk are measured to be lower than 1.63 μs and −29 dB, respectively. Since the Goos–Hänchen shift can reach approximately 1 mm, the number of output ports can be further increased on condition that the utilized incident light has a smaller spot diameter. [ABSTRACT FROM AUTHOR]