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Tin sulfide semiconductor nanowires (NWs) have been widely investigated for photodetection applications because of their good optical and electrical properties. Herein, we synthesized n-type SnS2 NWs and then fabricated SnS2 NW photodetectors with a ferroelectric polymer side-gate. The strong electric field induced by ferroelectric polymer can effectively suppress the dark current and improve the detectivity in SnS2 NW photodetectors. The photodetectors after polarization depletion exhibit a high photoconductive gain of 4.0 × 105 and a high responsivity of 2.1 × 105 A W−1. Compared with devices without polarization depletion, the detectivity of polarization-depleted photodetectors is improved by at least two orders of magnitude, and the highest detectivity is 1.3 × 1016 Jones. Further, the rise and fall time are 56 and 91 ms respectively, which are about tens of times faster than those without polarization depletion. The device also shows a good spectral response from ultraviolet to near-infrared. This study demonstrates that ferroelectric materials can enhance optoelectronic properties of low-dimensional semiconductors for high-performance photodetectors.

We propose an efficient scheme to manipulate the Goos–Hänchen (GH) shift of a reflected beam from a metal-clad waveguide, where a coherent atomic medium with a Λ -type configuration is employed as the substrate. Using experimentally achievable parameters, we identify the conditions under which spontaneously generated coherence (SGC) allows us to enhance the spatial and angular GH shifts of the reflected beam. With the help of SGC, the relative phases of the probe and control fields can alter the absorption gain and refractive index of the atomic medium, thereby manipulating the magnitudes, signs, and positions of the spatial and angular shifts. Furthermore, the spatial and angular GH shifts can be coherently controlled via adjusting the incoherent pumping rate and the intensity of the control field. Our proposal provides an avenue for the manipulation of spatial and angular GH shifts and potential applications in optical switching and optical steering.

We investigate the effect of doped Er3+ ion concentration on the Goos–Hänchen (GH) shift of a reflected beam in a Kretschmann–Raether structure, where an Er3+-doped yttrium aluminum garnet crystal is employed as the substrate. Due to the difference in the electric dipole moment and spontaneous emission decay induced by Er3+ ion concentration, the reflected GH shift is sensitively dependent upon Er3+ ion concentration. Furthermore, it is demonstrated that the intensity and detuning of the control field have different effects on the magnitude, sign, and position of the GH shift under different concentrations of Er3+ ion. Therefore, our scheme may provide a basis for selecting suitable concentrations to realize high-performance optical devices in future integrated systems.

We propose an effective scheme to enhance the efficiency of optical second-order sideband (OSS) via optomechanically induced absorption (OMIA) in a double-cavity optomechanical system. In this double-cavity optomechanical configuration, the optomechanical cavity is driven by a strong control field and a weak probe pulse, while the assisted cavity is excited by another strong control field. Using experimentally achievable parameters, we identify that the present optomechanical system can create the OMIA effect and improve the efficiency of the upper OSS beyond that is achieved by employing optomechanically induced transparency (OMIT). With the aid of OMIA, we also report that the maximum efficiency and linewidth of the upper OSS peak can be modulated by the double-cavity coupling strength and the detuning of the driving field. The present proposal offers a new path to optimize optical nonlinearity and design chip-scale signal processing.

We theoretically propose a scheme to measure the topological charge (TC) of a mid-infrared vortex beam via observing the intensity distribution of the four-wave mixing (FWM) field in an asymmetric semiconductor double quantum well. Due to the existence of Fano-type interferences, the special inherent interference takes place, and thus generates the interference-type phase and intensity patterns for the FWM field. Furthermore, it is demonstrated that the intensity and visibility of the interference-type intensity pattern can be drastically manipulated by adjusting the intensity and detuning the control field. Subsequently, we perform the TC measurement of the vortex driving field via directly monitoring the number of light spots of the FWM field. By choosing the suitable control parameters, the detectable value of the TC can reach to 120 with the visibility exceeding 0.97. Our scheme may provide the possibility for the realization of a mid-infrared OAM detector in a compact solid-state system.

A coherently prepared Er3+-doped yttrium aluminum garnet (YAG) crystal with a four-level ionic configuration is exploited for realizing one-dimensional (1D) and two-dimensional (2D) electromagnetically induced gratings (EIGs). Owing to the probe gain induced by the incoherent pump, the diffraction efficiency of the crystal grating, especially the first-order diffraction, can be significantly improved via increasing the incoherent pumping rate or decreasing the probe detuning. The enhancement of the grating diffraction efficiency originates from the interference between the gain and phase gratings. It is also demonstrated that the diffraction of the crystal grating can be dynamically controlled via tuning the intensity and detuning of the standing-wave driving field or the concentration of Er3+ ion. More importantly, the probe energy of the diffraction side lobes around the central principle maximum is comparable to that of the first-order diffraction field for small driving intensity or large driving detuning. Our scheme may provide a possibility for the active all-optical control of optical switching, routing and storage in fiber communication wavelengths.

A scheme for the coherent control of perfect optical vortex (POV) in an asymmetric semiconductor double quantum well (SDQW) nanostructure is proposed by exploiting the tunneling-induced highly efficient four-wave mixing (FWM). The orbital angular momentum (OAM) is completely transferred from a unique POV mode to the generated FWM field. Using experimentally achievable parameters, we identify the conditions under which resonant tunneling allows us to improve the quality of the vortex FWM field and engineer helical phase wave front beyond what is achievable in the absence of resonant tunneling. Furthermore, we find that the intensity and phase patterns of the vortex FWM field are sensitive to the detuning of the probe field but rather robust against the detuning of the coupling field. Subsequently, we perform the coaxial interference between the vortex FWM field and a same-frequency POV beam and show interesting interference properties, which allow us to measure the topological charge of the output POV beam. Our result may find potential applications in quantum technologies based on POV in solids.

A scheme for magnetic-free optical nonreciprocity in an ensemble of four-level cold atoms is proposed by exploiting the directional four-wave mixing effect. Using experimentally achievable parameters, the nonreciprocal optical responses of the system can be observed and the conversion on nonreciprocal transmission and nonreciprocal phase shift can be implemented. These nonreciprocal phenomena originate from the directional phase matching, which breaks the time-reversal symmetry and dynamic reciprocity of the cold atomic system. Moreover, by embedding the cold atoms into a Mach-Zehnder interferometer and choosing proper parameters, a two-port optical isolator with an isolation ratio of 79.70 dB and an insertion loss of 0.35 dB and a four-port optical circulator with a fidelity of 0.9985 and a photon survival probability of 0.9278 can be realized, which shows the high performance of isolation and circulation. The proposal may enable a new class of optically controllable cavity-free nonreciprocal devices in optical signal processing at the low light level.

Low-dimensional tin selenide nanoribbons (SnSe NRs) show a wide range of applications in optoelectronics fields such as optical switches, photodetectors, and photovoltaic devices due to the suitable band gap, strong light–matter interaction, and high carrier mobility. However, it is still challenging to grow high-quality SnSe NRs for high-performance photodetectors so far. In this work, we successfully synthesized high-quality p-type SnSe NRs by chemical vapor deposition and then fabricated near-infrared photodetectors. The SnSe NR photodetectors show a high responsivity of 376.71 A W−1, external quantum efficiency of 5.65 × 104%, and detectivity of 8.66 × 1011 Jones. In addition, the devices show a fast response time with rise and fall time of up to 43 μs and 57 μs, respectively. Furthermore, the spatially resolved scanning photocurrent mapping shows very strong photocurrent at the metal-semiconductor contact regions, as well as fast generation-recombination photocurrent signals. This work demonstrated that p-type SnSe NRs are promising material candidates for broad-spectrum and fast-response optoelectronic devices.

We propose a potentially practical scheme for realizing ultrasensitive size sensor of a single metallic nanoparticles (MNP) in a hybrid nonlinear microcavity. This is achieved by exploiting a well-established microcavity-engineered plasmonic resonance, where a degenerate parametric amplifier (DPA) is embedded into the microcavity driven by a strong pump field and a weak probe pulse. It is shown that the transmission spectrum of the probe pulse exihibits a two-peak splitting and the splitting width depends on the radius. The radius of a single MNP can be inferred from the transmission spectrum by monitoring the width between two peaks. Using experimentally achievable parameters, we identify the detection sensitivity of the sensor can reach approximately 0.198 THz/nm for detecting and sizing of individual MNPs as small as 10 nm in radius.

We propose a scheme for achieving magnon antibunching in a hybrid ferromagnet–superconductor system, where the magnons excited in two yttrium iron garnet (YIG) spheres couple the different levels of a cyclic three-level superconducting qubit by eliminating two perpendicular microwave cavity modes. With the aid of the three-level system, we find that the magnon antibunching can be achieved in a weak coupling regime via the degenerate three-wave mixing process. Moreover, it is found that the magnon antibunching inside a YIG2 sphere can be effectively regulated by manipulating the YIG1 sphere, for instance, the coupling strength of the YIG1 sphere and qubit and the driving strengths of the system. This work provides an alternative scheme for constructing the single magnon source based on the ferromagnet–superconductor technology and is conducive to studying the quantum properties of magnons.

An efficient route for detecting time-dependent acceleration (TDA) is performed by employing electromechanically induced phononic sidebands in coupled frequency-mismatched electromechanical resonators. Based on the effects of difference frequency mixing and cascaded phonon-scattering in the electromechanical system, the nonlinear responses of normal and anomalous phononic sidebands are generated and enhanced in the strong inter-modal coupling regime. In the detection scheme, the information of TDA can be delivered to the spectral responses of acceleration-induced sidebands (AISs) since there is the piezoelectric coupling between the electromechanical resonators and a test mass that perceives external acceleration. Additionally, the amplitude of TDA could be separately detected by observing the amplitude variation of AISs, while the variation period of TDA could be read by monitoring the frequency of the prominent peak in the AIS signals. The distinctive nature of the electromechanical system in the environment of the cryogenic cooling enables an acceleration resolution of 12 µg (g = 9.8 m s−2) and a frequency resolution of 0.06 Hz.

In this paper, toroidal localized spoof surface plasmons (LSSPs) based on homolateral double-split ring resonators is proposed and experimentally demonstrated at microwave frequencies. By introducing a new split in the conventional single-split ring resonator, the magnetic field in resonator is locally modified. The double-split ring resonator can create the mixed coupling in the structure, leading to the enhancement of magnetic field. Both numerical simulations and experiments are in good agreement. Compared with traditional toroidal LSSPs based on the single-split ring resonators, the imperfection of toroidal LSSPs is resolved, the intensity of toroidal resonance and the figure of merit (FoM) are significantly enhanced. To understand and clarify the enhanced magnetic field phenomena, we analyze the role of the double-split ring resonator. The effect of location of source and spacing between two splits on the resonance intensity are also discussed. A higher intensity of toroidal LSSPs resonance could be achieved by changing the spacing between two splits. Additionally, it is experimentally demonstrated that the enhanced toroidal LSSPs resonance is sensitivity to the background medium. The results of our research provide a new idea for exciting the enhanced toroidal dipole.

We investigate the enhanced generation of the optical second-order sideband (OSS) via magnon Kerr nonlinearity from a cavity magnonical hybrid system consisting of a single small yttrium iron garnet (YIG) crystal sphere and a three-dimensional (3D) rectangular cavity driven with a weak probe and a strong control field. Beyond the linear approximation, we solve the nonlinear Heisenberg–Langevin equations for achieving the analytical solutions by employing the perturbation technique. Using the experimentally achievable parameter settings, we demonstrate that the OSS generation can be significantly enhanced via increasing the magnon Kerr nonlinearity even if the coupling between the cavity and magnon is weak. Interestingly, two-color OSS generation can be observed when the cavity-magnon coupling is in the strong-coupling regime, which results from the magnonical polaritons induced by the hybrid of cavity and magnon modes. The present results illustrate the potential to utilize magnon Kerr nonlinearity for enhancing optical higher-order sidebands and controlling optical frequency combs, as well as to guide the design of experimental implementation.

The electronic, optical, and photocatalytic properties of Au-adsorbed MoSi2N4 systems are predicted by first-principles calculations. Electronic structure analysis shows that the band gap is reduced from 1.89 eV (intrinsic MoSi2N4) to 0 eV (MoSi2N4–9Au). Calculation results of density of states indicate that the valence band edge is mainly contributed by the Mo 4d state, whereas the conduction band edge is contributed by both the Mo 4d and Si 3p states. As the number of adsorbed Au atoms is increased, the absorption coefficient increases from 3.0 × 104 cm−1 to 5.6 × 104 cm−1, meaning that more photons can be absorbed. Indeed, Au-adsorbed MoSi2N4 monolayer shows greater potential for applications such as water splitting and CO2 reduction based on redox potential analysis. The Au-adsorbed MoSi2N4 structures can effectively change the properties of materials, offering great potential in different fields.

We propose a potentially practical scheme for the controllable single-photon transport via waveguides which are coupled to a microcavity–emitter system. The microcavity–emitter system consists of a V-type three-level emitter and two or one single-mode microcavity. A driving field is used to drive a hyperfine transition between two upper excited states of the V-type three-level emitter. Beyond chiral coupling between waveguides and microcavity–emitter system, we show that the perfectly nonreciprocal single-photon transport in a single waveguide and the single-photon router with 100% routing probability in two waveguides can be achieved. Interesting enough, whether the nonreciprocal single-photon transport or the single-photon router can be switched periodically by adjusting the phase associated with microcavity–emitter coupling strength and the driving field. The complete physical explanation of the underlying mechanism is presented.

Single-layer MoSi2N4, a high-quality two-dimensional material, has recently been fabricated by chemical vapor deposition. Motivated by this latest experimental work, herein, we apply first principles calculations to investigate the electronic, optical, and photocatalytic properties of alkali-metal(Li, Na, and K)-adsorbed MoSi2N4 monolayer. The electronic structure analysis shows that pristine MoSi2N4 monolayer exhibits an indirect bandgap (E g = 1.89 eV). By contrast, the bandgaps of one Li-, Na-, and K-adsorbed MoSi2N4 monolayer are 1.73 eV, 1.61 eV, and 1.75 eV, respectively. Moreover, the work function of MoSi2N4 monolayer (4.80 eV) is significantly reduced after the adsorption of alkali metal atoms. The work functions of one Li-, Na-, and K-adsorbed MoSi2N4 monolayer are 1.50 eV, 1.43 eV, and 2.03 eV, respectively. Then, optical investigations indicate that alkali metal adsorption processes substantially increase the visible light absorption range and coefficient of MoSi2N4 monolayer. Furthermore, based on redox potential variations after alkali metals are adsorbed, Li- and Na-adsorbed MoSi2N4 monolayers are more suitable for the water splitting photocatalytic process, and the Li-adsorbed case shows the highest potential application for CO2 reduction. In conclusion, alkali-metal-adsorbed MoSi2N4 monolayer exhibits promising applications as novel optoelectronic devices and photocatalytic materials due to its unique physical and chemical properties.

The photon router plays an essential role in the optical quantum network. However, conventional routers generally couple photons chirally into waveguides to achieve complete transmission from the input port to the required port. Here, we use non-chiral photon-atom interactions for targeted routing. The system consists of two V-type three-level atoms and two parallel waveguides. In addition, the two atoms are driven by external coherent fields, respectively. With a real-space Hamiltonian, the probability of photon transmitted to four ports can be obtained. The study shows that a single photon input from the left port of the waveguide-a can be deterministically transferred to any of the four ports of the two waveguides by adjusting the detuning of the atom and the driving field on the atom, as well as the distance between the two atoms.

We analyze the destructive interference in monolayer graphene under Landau quantization in a time-dependent way by using the Bloch-Maxwell formalism. Based on this analysis, we investigate the dynamics control of an infrared probe and a terahertz (THz) switch pulses in graphene. In presence of the THz switch pulse, the destructive interference take places and can be optimized so that the monolayer graphene is completely transparent to the infrared probe pulse. In absence of the THz switch pulse, however, the infrared probe pulse is absorbed due to such a interference does not take place. Furthermore, we provide a clear physics insight of this destructive interference by using the classical dressed-state theory. Conversely, the present model may be rendered either absorbing or transparent to the THz switch pulse. By choosing appropriate wave form of the probe and switch pulses, we show that both infrared probe and THz switch pulses exhibit the steplike transitions between absorption and transparency. Such steplike transitions can be used to devise a versatile quantum interference-based solid-state optical switching with distinct wave-lengths for optical communication devices.

A coherently prepared Er3+-doped yttrium aluminum garnet (YAG) crystal with a four-level ionic configuration is exploited for realizing one-dimensional (1D) and two-dimensional (2D) electromagnetically induced gratings (EIGs). Owing to the probe gain induced by the incoherent pump, the diffraction efficiency of the crystal grating, especially the first-order diffraction, can be significantly improved via increasing the incoherent pumping rate or decreasing the probe detuning. The enhancement of the grating diffraction efficiency originates from the interference between the gain and phase gratings. It is also demonstrated that the diffraction of the crystal grating can be dynamically controlled via tuning the intensity and detuning of the standing-wave driving field or the concentration of Er3+ ion. More importantly, the probe energy of the diffraction side lobes around the central principle maximum is comparable to that of the first-order diffraction field for small driving intensity or large driving detuning. Our scheme may provide a possibility for the active all-optical control of optical switching, routing and storage in fiber communication wavelengths.

Two-dimensional (2D) optical lattices of driven cold atoms can provide a useful platform to construct 2D electromagnetically induced grating (EIG) with parity-time (PT) antisymmetry. This atomic grating is achieved by the spatial modulations of the atomic density and frequency detunings in the four-level double-Λ atomic system. Gain-assisted PT antisymmetry allows us to realize lop-sided Raman–Nath diffraction with high diffraction efficiency at the exception point. It is shown that the nontrivial phenomenon originates from non-Hermitian degeneracy of PT antisymmetry. Our scheme may provide the possibility for active all-optical control and conversion of the spatial beam in optics.

We investigate the effect of doped E r 3 + ion concentration on an electromagnetically induced grating in an E r 3 + -doped yttrium aluminum garnet (YAG) crystal. Due to the change of electric dipole moment and spontaneous emission decay induced by E r 3 + ion concentration, the Fraunhofer diffraction of the solid-state grating is sensitively dependent upon E r 3 + ion concentration. The three-level E r 3 + ion system with a closed loop leads to probe gain appearing in some concentrations of the E r 3 + ion, which significantly improves the first-order diffraction efficiency of the solid-state grating. Furthermore, it is demonstrated that the relative phase, signal detuning, and grating thickness have different effects on the first-order diffraction efficiency of the solid-state grating under different concentrations of the E r 3 + ion. Therefore, our scheme may provide a basis for selecting a suitable concentration to realize high-efficiency optical switching and routing in future integrated systems.

In this Letter, numerical and experimental studies for the spoof-anapole effect are presented. Different from the anapole modes, when electric and toroidal dipole intensities are minimized, the spoof-anapole effect can be generated. The spoof-anapole effect can reduce the radiation losses with a high Q -factor. The concept is valid in various frequency bands from microwave range for millimeter-sized objects to visible range for nanoparticles. The spoof-anapole modes are first experimentally realized in microwave metamaterials. Almost perfect spoof-anapole behavior is observed, which produces an extremely high Q -factor at the resonance frequency. The experimental results agree well with the analytical ones and pave way to excite the non-radiating electromagnetic sources.

We propose an efficient scheme to control Goos–Hänchen (GH) shifts of the reflected and transmitted beams in a cavity containing Er3 + -doped yttrium-aluminum-garnet (YAG) crystal with a four-level Er3 + ionic system. It is found that both the values and signs of the reflected and transmitted GH shifts can be coherently controlled by tuning the relevant optical parameters, such as the incoherent pumping rate, and the intensity and detuning of the driving field. Furthermore, we propose a scheme for such a configuration of the reflected GH shift as a family of reflection-type optical switchings. It is shown that the average port spacing and reflectivity of the optical switching can reach approximately 1.03 mm and 16.88, respectively, which indicate the high performance of switching function. Our proposal may provide a possibility to implement optically tuned optical switching.

The sign of quantum interference (constructive or destructive) based on cavity optomechanics is crucial for observing quantum phenomena and designing high-sensitivity sensors with an integrable structure. Here, we propose an efficient scheme to generate constructive interference and optomechanically induced absorption (OMIA) in a hybrid atom–cavity optomechanical system. Using experimentally achievable parameters, we theoretically demonstrate that a gain-type OMIA dip with the extremely narrow linewidth and the enhanced spectral intensity can be modulated by an assisted atom that is excited by an external control field. More importantly, we report that a precise mass sensor is achieved by employing an observable correlation between the OMIA dip and the added mass deposited on the mechanical object. With the help of the back-action cooling of the mechanical object, we identify that the detection sensitivity and minimum resolution of the mass sensor can reach 3.14 MHz / ng and 1 fg, respectively.

We propose a potentially practical scheme for constructing a quantum network based on a system where three waveguides are coupled to two two-level atoms. In the case of chiral couplings between the waveguides and atoms, we realize a directed single-photon router and the efficiency of single-photon routing reaches 100%. In addition, in this network, the photon input from one port of the channel can be fully routed to any outport of the other two channels by modulating the coupling strength of the waveguides and atoms and the frequency of the incident photon. Thus, a quantum network can be constructed based on our scheme. The influence of the ratio of chiral coupling strength on the properties of the single-photon router is also shown. We also show how the efficiency of routing is affected by system dissipation.

We propose a scheme for realizing high-precision three-dimensional (3D) atom localization by using V-type three-level atoms in which atoms interact with a weak probe field, a weak control field together with three mutually perpendicular standing-wave fields. Our numerical results show that the precision of 3D atom localization in volumes can be improved via three-wave mixing (TWM) in the presence of the control switch field but made instead to be reduced when the TWM channel is off in absence of the switch field. As a result, assisting with TWM, a single position information of the atom in the 3D space can be achieved, and the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength. The effect of spontaneously generated coherence (SGC) as well as the relative phase of the applied fields on the precision of 3D atom localization are also discussed.

We investigate the coherent control of the transmission spectrum in a cavity magnetomechanical system consisting of microwave photon, magnon, and phonon modes, where the microwave cavity is driven by a strong pump field and a weak probe field, and the magnon is driven by a weak microwave source. Different from a single transparency window in the absence of the phonon–magnon interaction, two transparency windows and three absorption dips can be observed in the presence of the phonon–magnon interaction, which originates from the joint interaction of phonon–magnon and photon–magnon. In addition, two absorption dips located at both sides of the central absorption dip can be modulated asymmetrically into amplification and absorption by varying the magnetic field amplitude of the magnon driving field. Interestingly enough, the relative phase of applied fields could have profound effects on both the transmission spectrum and the group delay of the output field by choosing the appropriate magnetic field amplitude of the magnon driving field. The transmission group delay can be switched between positive to negative and vice versa by adjusting the relative phase between the applied fields. The present results illustrate the potential to utilize the relative phase for controlling the microwave signal in the cavity magnomechanical system, as well as guidance in the design of information transduction and quantum sensing.

Precision measurement plays a very important role in many field including optics, astronomy, biochemistry, atmospheric science, environmental engineering, dusty plasma, etc. Here, we propose an efficient scheme to investigate the relationship between linewidth and radius of the metal nanoparticle (MNP) in a hybrid optical microcavity system that included a quantum emitters interacting with a MNP. By using detailed numerical simulations and analytical modeling, we find that the linewidth of the amplification window is sensitive to the radius of MNP. Subsequently, we discuss the application of such a hybrid optical microcavity system as a family of high-sensitivity sensor for measuring the tiny radius of the MNP. Using experimentally achievable parameters, we identify the detection sensitivity of the sensor can arrive at approximately 2.6 GHz nm−1. The present investigation provides a route toward guiding the design of sensitive devices.

We propose an effective scheme for high-precision three dimensional(3D) atom localization via measuring the population of excited state in a four-level atomic system driven by a probe field and three orthogonal standing-wave fields. In this scheme, the position-dependent multiphoton quantum destructive interference leads to multiphoton excitation of the excited state and enhances the fluorescence emission. We show that adjusting the frequency detuning and phase shifts associated with the standing-wave fields can modify the multiphoton quantum destructive interference and lead to a redistribution of the atoms. The maximal probability of finding the atom at the certain position in one period of the standing-wave fields can be 100% and the highest spatial precision is about 0.02λ.

This study investigates the photocatalytic activity of a novel Mn-doped Bi4O5Br2 material prepared via a facile synthesis process. The experimental and theoretical results confirm that Mn doping enhances the efficiency of NO removal over a Bi4O5Br2 catalyst under visible light irradiation. The SEM (scanning electron microscopy), BET (Brunauer-Emmet-Teller), XRD (X-ray diffraction) analyses show that neither the surface morphology nor the phase of the photocatalytic material changes after the incorporation of Mn. The ESR (electron spin resonance) and UPS (Ultraviolet photoelectron spectroscopy) results show that the electrons in the CBM (conduction band minimum) can be directly captured by O2 to produce large amounts of •O2 radicals, and •OH radicals are formed via the route of •O2−→H2O2→•OH. The higher efficiency of Mn-doped Bi4O5Br2 is driven by the reduced band gap, widened visible light absorption range, higher intensity of visible light absorption, and enhanced separation efficiency of electrons and holes in this material compared with those of pristine Bi4O5Br2.

We analyze an efficient scheme to enhance the Goos-H\"anchen (GH) shifts of the reflected and transmitted beams in a cavity containing two-level atomic medium. A broadband squeezed vacuum field is injected into the cavity to interact with the atomic medium. In the bad cavity limit, the Bloch equations for the atomic operators are identical to those in the free space, but with the modification of the system parameters. Using experimentally achievable parameters, we identify the conditions under which the squeezed vacuum allows us to enhance the GH shifts of the reflected and transmitted beams beyond what is achievable in the absence of the squeezed vacuum. The enhanced GH shifts originate from the coherent population oscillations controlled by the squeezed vacuum field. Furthermore, we also find that the GH shifts of the reflected and transmitted beams depend sensitively on the relative phase between the control field and the squeezed vacuum field. Subsequently, we propose a scheme for such a configuration of the GH shift as a family of hypersensitized displacement sensors. Based on the numerical analysis, the detection sensitivity and minimum detectable value for the tiny displacement can reach approximately $2340\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{m}/\mathrm{nm}$ and 14.4 pm, respectively.

We investigate the force measurement sensitivity in a squeezed dissipative optomechanics within the free-mass regime under the influence of shot noise (SN) from the photon number fluctuations, laser phase noise from the pump laser, thermal noise from the environment, and optical losses from outcoupling and detection inefficiencies. Generally, squeezed light could generate a reduced SN on the squeezed quadrature and an enlarged quantum backaction noise (QBA) due to the antisqueezed conjugate quadrature. With an appropriate choice of phase angle in homodyne detection, QBA is cancellable, leading to an exponentially improved measurement sensitivity for the SN-dominated regime. By now, the effects of laser phase noise that is proportional to laser power emerge. The balance between squeezed SN and phase noise can lead to an sub-SQL sensitivity at an exponentially lower input power. However, the improvement by squeezing is limited by optical losses because high sensitivity is delicate and easily destroyed by optical losses.

The properties of two and three two-split-ring-resonators (TSRRs) are investigated in this paper, which shows a remarkable Fano resonance in the microwave frequency. In two TSRRs, the Fano resonance results from the interference between two TSRRs by conductive coupling, both experiments and numerical simulations are in good agreement. The structure shows strong magnetic dipole at the intersection of two TSRRs. In three TSRRs, the double Fano resonances can be excited and double magnetic dipoles produce at two intersections. Because of the interaction between two magnetic dipole, symmetric magnetic dipole and anti-symmetric magnetic dipole (toroidal dipole) modes are presented, respectively. An almost doubled Q factor is observed in the three TSRRs compared to the two TSRRs. In addition, we experimentally demonstrate that the double Fano resonances are sensitivity to the refractive index of background. The sensitivity changes with the change of position of detected material. The highly sensitive areas of double Fano resonances locate at two intersections. This study paves the way to excite the multiple Fano resonances. Such Fano resonance can be applied to the sensors.

We theoretically investigate the enhanced charge-dependent generation of the optical second-order sidebands (OSS) in a gain-cavity-assisted optomechanical (GCAOM) system coupled to a charged object. The hybrid optomechanical system is coherently driven by an external two-tone laser field which consists of a continuous-wave pump field and a pulsed probe field. Beyond the conventional linearized description of optomechanical interactions, the nonlinear optomechanical interactions are included in the Heisenberg-Langevin equations and are treated analytically by means of the perturbation method. It is shown that an assisted gain cavity can significantly enhance the OSS generation and can also lead to higher charge dependence of the output OSS spectrum than that achieved from a lossy cavity optomechanical system. Subsequently we discuss the application of such a GCAOM system as a family of high-sensitivity sensor for measuring the charges. Using experimentally achievable parameters, we identify the conditions under which the assisted gain cavity allows us to enhance the OSS generation and improve sensitivity of the sensor beyond what is achievable in a lossy cavity optomechanical system. The present investigation may provide a route toward modulating the nonlinear optical properties of the electro-optic hybrid system, as well as to guide the design of sensitive devices.

We propose and analyze an efficient scheme for the lopsided Raman-Nath diffraction of one-dimensional ($1\mathrm{D}$) and two-dimensional ($2\mathrm{D}$) atomic gratings with periodic parity-time ($\mathcal{PT}$)-symmetric refractive index. The atomic grating is constructed by the cold-atomic vapor with two isotopes of rubidium, which is driven by weak probe field and space-dependent control field. Using experimentally achievable parameters, we identify the conditions under which $\mathcal{PT}$-symmetric refractive index allows us to observe the lopsided Raman-Nath diffraction phenomenon and improve the diffraction efficiencies beyond what is achievable in a conventional atomic grating. The nontrivial atomic grating is a superposition of an amplitude grating and a phase grating. It is found that the lopsided Raman-Nath diffraction at the exceptional point (EP) of $\mathcal{PT}$-symmetric grating originates from constructive and destructive interferences between the amplitude and phase gratings. Furthermore, we show that the $\mathcal{PT}$-phase transition from unbroken to broken $\mathcal{PT}$-symmetric regimes can modify the asymmetric distribution of the diffraction spectrum and that the diffraction efficiencies in the non-negative diffraction orders can be significantly enhanced when the atomic grating is pushed into a broken $\mathcal{PT}$-symmetric phase. In addition, we also analyze the influence of the grating thickness on the diffraction spectrum. Our scheme may provide the possibility to design a gain-beam splitter with tunable splitting ratio and other optical components in integrated optics.

We analyze the optical steady-state behaviors based on intersubband transitions in a triple quantum well structure driven coherently by a probe laser field and two control laser fields embedded in a unidirectional cavity. It is shown that the optical bistability behavior can be observed and controlled efficiently through the frequency detuning of the probe field, the intensities of two control fields, the electronic cooperation parameter, and the Fano-type interference. More interestingly, with Fano-type interference, switch from optical bistability to optical multistability or vice versa can be also controlled by adjusting the relative phase between two coherent control fields.

We propose an efficient scheme to generate quadrature squeezing of a higher-order sideband spectrum in an optomechanical system. This is achieved by exploiting a well-established optomechanical circumstance, where a second-order nonlinearity is embedded into the optomechanical cavity driven by a strong control field and a weak probe pulse. Using experimentally achievable parameters, we demonstrate that the second-order nonlinearity intensity and the frequency detuning of a control field allow us to modify the amplitude of higher-order sidebands and improve the amount of squeezing of a higher-order sideband spectrum. Furthermore, in the presence of a strong second-order nonlinearity, an optimizing quadrature squeezing of a higher-order sideband spectrum can be achieved, which provides a practical opportunity to design the squeezed frequency combs and other precision measurements.

We propose an efficient scheme for the controllable amplification of two-phonon higher-order sidebands in a quadratically coupled optomechanical system. In this scheme, a strong control field and a weak probe pulse are injected into the cavity, and the membrane located at the middle position of the cavity is driven resonantly by a weak coherent mechanical pump. Beyond the conventional linearized approximation, we derive analytical expressions for the output transmission of probe pulse and the amplitude of second-order sideband by adding the nonlinear coefficients into the Heisenberg-Langevin formalism. Using experimentally achievable parameters, we identify the conditions under which the mechanical pump and the frequency detuning of control field allow us to modify the transmission of probe pulse and improve the amplitude of two-phonon higher-order sideband generation beyond what is achievable in absence of the mechanical pump. Furthermore, we also find that the higher-order sideband generation depends sensitively on the phase of mechanical pump when the control field becomes strong. The present proposal offers a practical opportunity to design chip-scale optical communications and optical frequency combs.

We propose and analyze an effective scheme to enhance the optical higher-order sideband generation in a three-cavity array with local parity-time ($\mathcal{PT}$) symmetry. In this three-cavity configuration, a single cavity containing a quantum dot (QD) is coupled to an assisted $\mathcal{PT}$-symmetric combination of two cavities. Beyond the weak-excitation approximation, we derive the analytic formulas used to determine the nonlinear coefficient of the optical second-order sideband (OSS) by employing the perturbation technique. Using experimentally achievable parameters, we identify the conditions under which the assisted $\mathcal{PT}$-symmetric double-cavity system allows us to modify the transmission of the probe field and improve the efficiency of OSS generation beyond what is achievable in a loss-only QD-cavity system. We examine the influence of the $\mathcal{PT}$ phase transition from unbroken- to broken-$\mathcal{PT}$ regimes on the OSS generation. It is found that the efficiency of optical second-order sideband generation can be significantly enhanced when the assisted double-cavity system is in $\mathcal{PT}$-symmetric phase, extremely in the vicinity of the transition point. The present results illustrate the potential to utilize $\mathcal{PT}$-symmetric physical systems for enhancing optical higher-order sidebands and controlling optical frequency combs, as well as to guide the design of experimental implementation.

We investigate the generation and the evolution of two-mode continuous-variable (CV) entanglement from system of a microwave-driven V-type atom in a quantum beat laser. By taking into account the effects of spontaneously generated quantum interference between two atomic decay channels, we show that the CV entanglement with large mean number of photons can be generated in our scheme, and the property of the filed entanglement can be adjusted by properly modulating the frequency detuning of the fields. More interesting, it is found that the entanglement can be significantly enhanced by the spontaneously generated interference., 7 pages, 4 figures