Ultrafast all-optical plasmon optical switch based on black phosphorus

Abstract

The invention discloses an ultrafast all-optical plasmon optical switch based on black phosphorus and a related method and equipment. An exemplary optical switch effect control method based on black phosphorus comprises the following steps: emitting pump light and probe light to black phosphorus; adjusting and fixing the time delay between the pump light and the probe light; performing scanning detection on the black phosphorus edge to obtain the state of the black phosphorus surface; and the energy density of the pump light is adjusted, so that plasmon propagation exists on the surface of the black phosphorus. Based on femtosecond laser pumping, the dielectric constant of the black phosphorus is regulated and controlled through an all-optical means, and picosecond-level dynamic response of a propagation state plasmon switch function can be achieved.

Description

Technical Field

[0001] The present invention belongs to the field of laser technology, and in particular relates to an ultrafast all-optical plasmon switch based on black phosphorus and related methods and devices. Background Art

[0002] Polaritons are a typical quasiparticle in condensed matter physics systems. Their physical essence stems from the strong coupling effect between the electromagnetic field and various quasiparticles (such as collective electron oscillations, excitons, optical phonons, etc.). When an electromagnetic wave propagates in a medium, if its frequency is close to the resonant frequency of a certain electric dipole in the medium, the electromagnetic field will polarize the medium. This polarization effect is particularly significant near the resonant frequency. This process can be regarded as a strong interaction between photons and the medium. As a product of photon-medium coupling, polaritons inherit the physical properties of both photons and media. This unique hybrid property enables it to exhibit many novel physical phenomena, such as significantly enhanced light-matter interaction strength, subwavelength electromagnetic field localization capability that breaks the diffraction limit, and controllable dispersion relations. Summary of the Invention

[0003] According to some aspects, the subject matter of the independent claims is provided. Some further aspects are defined in the dependent claims. Embodiments that do not fall within the scope of the claims should be interpreted as examples that help understand the present disclosure.

[0004] In a first aspect, a method for controlling an optical switching effect based on black phosphorus is provided, which may include: emitting pump light and probe light into black phosphorus; adjusting and fixing the time delay between the pump light and the probe light; performing scanning detection at the edge of black phosphorus to obtain the state of the black phosphorus surface; and adjusting the energy density of the pump light so that plasmon propagation occurs on the black phosphorus surface.

[0005] In a second aspect, a method for preparing black phosphorus flakes is provided, which may include: placing black phosphorus crystals in a glove box; using mechanical exfoliation technology to directionally exfoliate the black phosphorus crystals to form black phosphorus crystal flakes; and transferring the black phosphorus crystal flakes to the surface of a silicon substrate.

[0006] In a third aspect, a method for controlling an optical switching effect based on black phosphorus is provided, which may include: emitting pump light with a specific energy density into black phosphorus to allow optical signals to propagate through the black phosphorus; turning off the pump light to prevent the optical signal from propagating through the black phosphorus; wherein the pump light with a specific energy density can cause plasmon propagation on the surface of the black phosphorus.

[0007] In a fourth aspect, a black phosphorus-based optical switching device is provided, which may include: black phosphorus; the optical switching device has an on state and an off state; when pump light with a specific energy density is emitted to the black phosphorus to allow the optical signal to propagate through the black phosphorus, the optical switching device is in the on state; when the pump light is turned off to prevent the optical signal from propagating through the black phosphorus, the optical switching device is in the off state; wherein the pump light with a specific energy density can cause plasmon propagation on the surface of the black phosphorus. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The following will be described in more detail with reference to the embodiments and drawings, wherein:

[0009] Figure 1 A schematic diagram of an ultrafast pump-probe light black phosphorus spectral modulation system according to an exemplary embodiment of the present disclosure is shown.

[0010] Figure 2 A schematic diagram of a mid-infrared hundred-femtosecond detection laser generation system according to an exemplary embodiment of the present disclosure is shown.

[0011] Figure 3 A schematic diagram of a black phosphorus flake according to an exemplary embodiment of the present disclosure under an optical bright field microscope is shown.

[0012] Figure 4 A schematic diagram showing the time evolution of the near-field intensity signal of excited-state black phosphorus according to an exemplary embodiment of the present disclosure is shown.

[0013] Figure 5A A schematic diagram showing the intensity spectrum of the near-field spectral response of photoplasmons in black phosphorus at different pump light energy densities according to an exemplary embodiment of the present disclosure.

[0014] Figure 5B A schematic diagram showing the phase spectrum of the near-field spectral response of photoplasmons in black phosphorus at different pump light energy densities according to an exemplary embodiment of the present disclosure.

[0015] Figure 6 A schematic diagram illustrating near-field optical imaging of a propagating-state plasmon optical switch in black phosphorus according to an exemplary embodiment of the present disclosure is shown.

[0016] Figure 7 A schematic diagram showing the plasmon interference fringe morphology obtained under optical pumping conditions according to an exemplary embodiment of the present disclosure is shown.

[0017] Figure 8 A flow chart of an exemplary method 800 according to an exemplary embodiment of the present disclosure is shown.

[0018] Figure 9 A flow chart of an exemplary method 900 according to an exemplary embodiment of the present disclosure is shown.

[0019] Figure 10 A flow chart of an exemplary method 1000 according to an exemplary embodiment of the present disclosure is shown.

[0020] Figure 11 An example block diagram of a system 1100 including an optical switching device according to an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0021] Below, example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Note that the drawings may not be drawn to scale. Obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments of the present application, and the present application is not limited to the example embodiments described herein.

[0022] Although the specification mentions "one", "an", or "some" embodiments at some locations in the text, this does not necessarily mean that each mention refers to the same embodiment, or that a particular feature only applies to a single embodiment. The individual features of different embodiments may also be combined to provide other embodiments. Moreover, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, whether or not explicitly described, it is within the knowledge of those skilled in the art to apply such feature, structure, or characteristic in conjunction with other embodiments. It should be understood that although terms such as "first" and "second" may be used to describe various elements, these elements should not be limited by these terms. These terms are merely used to distinguish one element from another.

[0023] In the present disclosure, the terms "at least one of A or B", "at least one of A and B", and "A and / or B" mean "A", "B", or "A and B". In the present disclosure, "A, B, and / or C" means "A", "B", "C", "A and B", "A and C", "B and C", or "A, B, and C".

[0024] Metal plasmons (such as gold and silver) can achieve local field enhancement through nanostructure design, but their losses result in a propagation distance of less than 10μm, and the resonant frequency is relatively fixed, with insufficient flexible modulation capabilities; although phonon polariton material systems (such as hexagonal boron nitride and α-molybdenum trioxide (α-MoO3, etc.)) have low loss and hyperbolic dielectric characteristics, their optical properties are determined by the natural frequency of lattice vibration and lack dynamic control methods; traditional semiconductor materials (such as indium arsenide) regulate carrier concentration through chemical doping, but there is the problem of irreversible doping, the control dimension is single and lacks real-time performance; graphene plasmons developed in the past decade regulate carrier concentration through chemical doping or gate voltage, but there are problems such as relatively slow electrical response speed and high plasmon propagation loss.

[0025] The present invention aims to provide an all-optical modulated propagation-state plasmon optical switch based on black phosphorus semiconductor materials and a control method thereof. This technology breaks through the limitations of static dielectric response characteristics and single carrier concentration control of traditional materials through the dynamic control mechanism of non-equilibrium carriers induced by ultrafast optical pumping, and realizes the optically controlled reconfigurable characteristics of plasmon devices. Specifically, the transient high-concentration carriers generated by femtosecond laser pulse excitation can induce the negative real part of the dielectric constant of black phosphorus material along the z-axis of the lattice (εz<0), thereby realizing on-demand excitation of propagation-state plasmons. Thanks to the high carrier mobility characteristics of black phosphorus, the constructed plasmon waveguide exhibits ultra-low propagation loss and excellent field localization characteristics. The dynamic optical control means of the present invention realizes real-time modulation of plasmon transmission characteristics through full optical field manipulation, and its response speed can reach the order of picoseconds, providing an innovative solution for the development of a new generation of reconfigurable photonic integrated circuits, ultrafast all-optical signal processing devices and high-performance mid-infrared optoelectronic systems. In particular, based on femtosecond laser pumping, the dielectric constant of black phosphorus can be controlled by all-optical means, which can achieve picosecond dynamic response of the propagating state plasmon switching function.

[0026] Figure 1 A schematic diagram of an ultrafast pump-probe light black phosphorus spectral modulation system 100 according to an exemplary embodiment of the present disclosure is shown. As shown, the system 100 may include: a pump light source module 102 for outputting pump light, wherein the pump light serves as an excitation light source, and its core function is to induce interband electronic transitions in the black phosphorus material through photon energy injection; a probe light source module 104 for outputting probe light; a pump light delay module 106 for adjusting the delay of the pump light. This module, based on the principle of adjustable optical path, achieves precise control of the excitation timing by changing the transmission path length of the pump light; a near-field optical microscope module 114 for carrying black phosphorus and coupling the pump light and probe light. This module integrates a high-precision optical coupling system that can precisely focus the pump light and probe light onto the surface of the black phosphorus sample and simultaneously achieve visual positioning of the sample; and a Fourier transform spectroscopy module 116 for real-time monitoring of the spectrum. This module, based on the Michelson interferometer principle, achieves high-resolution real-time acquisition of mid-infrared spectra by fast Fourier transforming the interference pattern. In some embodiments, the system 100 may further include a pump light collimation module 110 for reducing the divergence of the pump light. This module is typically composed of a collimating lens assembly and can convert the divergent beam output by the pump light source into a nearly parallel beam. Furthermore, a probe light collimation module 112 for reducing the divergence of the probe light is employed. This module employs an optical design similar to that of the pump light collimation module to ensure good directionality of the probe beam. In some embodiments, an atomic force microscope can be used in place of a near-field optical microscope.

[0027] According to some embodiments of the present invention, the pump light source uses a near-infrared femtosecond laser with a central wavelength of 1560nm (nanometers), a corresponding photon energy of 0.8eV, and a pulse width of about 100fs (femtoseconds). This energy value is greater than the intrinsic band gap of black phosphorus (~0.3eV), which can effectively stimulate inter-band electron transitions. Its physical mechanism is that when the photon energy exceeds the material band gap, the valence band electrons absorb the photon energy and then transition to the conduction band to form electron-hole pairs. In some embodiments, the near-infrared femtosecond laser may include an erbium-doped fiber, which serves as a gain medium and generates laser pulses of a specific wavelength through the stimulated emission process of erbium ions. It has the characteristics of high stability and good beam quality. The detection light source uses a hundred-femtosecond laser in the mid-infrared band (central wavelength ~10μm (micrometers)). This band covers the characteristic absorption region of black phosphorus material and is suitable for sensitive detection of changes in carrier concentration. The pump light delay module 106 can use a high-precision linear displacement platform. The high-precision linear displacement platform can include at least one reflector and can adjust the time delay by moving. Its displacement accuracy usually reaches the nanometer level to ensure that the adjustment accuracy of the time delay meets the measurement requirements of the femtosecond level. Preferably, the high-precision linear displacement platform can include four reflectors. By arranging the reflectors in combination, long optical path adjustment can be achieved in a limited space, thereby increasing the time delay adjustment range. In some embodiments, the mid-infrared band of the detection light source can be generated by nonlinear difference frequency technology. This technology uses the second-order nonlinear effect of nonlinear optical crystals to make two beams of lasers with different wavelengths interact in the crystal to generate the required mid-infrared wavelength.

[0028] Figure 2A schematic diagram of a mid-infrared femtosecond probe laser generation system 200 according to an exemplary embodiment of the present disclosure is shown. The probe light source module 104 can use system 200 to generate probe light. As shown, system 200 may include: a first probe light source module 202, which provides a fundamental frequency laser source, typically a solid-state laser with good stability; a second probe light source module 204, which provides a tunable laser source to meet the needs of different difference frequency wavelengths; and a difference frequency module 208, which integrates a nonlinear optical crystal, such as a periodically poled lithium niobate crystal. This module performs nonlinear difference frequency processing on the lasers emitted by the first and second probe light source modules 202 and 204 to output mid-infrared probe light. When generating probe light using nonlinear difference frequency technology, a probe light delay module 108 may be provided after the first probe light module 202 to adjust the probe light's delay. This implementation is similar to that of the pump light delay module 106. This design ensures that the difference frequency-generated probe light maintains a precise relative delay relationship with the pump light in time series. In some embodiments, the first detection light source module can use a laser with a central wavelength of 980 to 2200 nm. Optionally, the laser includes a nonlinear optical fiber and an erbium-doped optical fiber, wherein the nonlinear optical fiber is used to achieve wavelength conversion, and the erbium-doped optical fiber is used for signal amplification to provide input light of sufficient power for the difference frequency process, and the second detection light source module can use a laser with a central wavelength of 1560 nm. Optionally, the laser includes an erbium-doped optical fiber, and the gain characteristics of the erbium-doped optical fiber are used to generate stable fundamental frequency light.

[0029] After the pump and probe beams are collimated and optimized by the collimation module, they are coupled to a scattering near-field optical microscope (spatial resolution <20nm) and passed through an infrared Fourier transform spectroscopy module. The collimation optimization process can be achieved by adjusting the position of the collimating lens to reduce the beam divergence angle to less than 1 milliradian, ensuring efficient optical coupling in the near-field region. In some embodiments, the spatial overlap of the pump and probe beams at the near-field probe tip can be achieved by adjusting the parabolic objective lens built into the near-field optical microscope. The parabolic objective lens has a spherical aberration design that can focus the two beams onto the subwavelength-scale probe tip region.

[0030] Before implementing the excitation and switching control technology scheme based on black phosphorus non-equilibrium hyperbolic plasmon provided by the present invention, it is necessary to prepare a suitable black phosphorus material. As a two-dimensional material with a layered structure, the physical and chemical properties of black phosphorus are extremely sensitive to the environment, especially in the air, which is very prone to oxidative degradation. Therefore, environmental control during the material preparation process is crucial. The first step is to place the black phosphorus crystal to be treated in a glove box. In one embodiment, in order to effectively suppress environmental oxidation, all operations can be carried out in a high-purity nitrogen or inert gas glove box (O2 / H2O concentration is strictly controlled at <0.1ppm). Because the interlayer van der Waals force of black phosphorus crystals is weak and there are a large number of dangling bonds on the surface, when exposed to an environment containing water vapor and oxygen, a chemical reaction will occur rapidly, resulting in lattice destruction. Therefore, it is preferred to continuously maintain an inert environment through a gas circulation system and a desiccant in the glove box. In some embodiments, an online gas analyzer can also be equipped to monitor the oxygen and water vapor concentrations in real time to ensure the stability of the preparation environment.

[0031] Then, mechanical stripping technology is used to directionally strip the bulk black phosphorus crystal to form black phosphorus crystal flakes. The mechanical stripping method is based on the weak van der Waals interaction between adjacent layers in the black phosphorus layered structure, and the stratification of the crystal is achieved by repeatedly sticking and stripping with sticky tape. By controlling the cleavage direction (along the long axis of the crystal), regular rectangular flakes with edges parallel to the zigzag direction can be obtained. This is because black phosphorus crystals have anisotropic cleavage characteristics, and stripping along the long axis direction can maintain the integrity of the crystal lattice to the greatest extent and reduce the generation of edge defects. In some embodiments, transparent tape can be used as a stripping medium, and the bulk crystal is pressed on the tape and then quickly torn off. The crystal thickness is gradually thinned by repeatedly repeating the stripping process until a nanoscale flake that meets the requirements is obtained. In this process, optionally, the thickness and edge morphology of the flake can be observed in real time with the aid of a near-field optical microscope to ensure the accuracy of the stripping direction.

[0032] Finally, the black phosphorus crystal flakes are transferred to the surface of the substrate. In some embodiments, silicon with a smooth surface, high chemical stability and strong compatibility with micro-nano processing technology can be used as a substrate. The transfer process usually adopts wet transfer or dry transfer technology. Taking wet transfer as an example, a layer of supporting medium (such as polymethyl methacrylate, PMMA) can be spin-coated on the peeled thin slice, and then the underlying silicon wafer is corroded by hydrofluoric acid solution. The thin slice-support layer complex suspended in the solution is transferred to the target silicon substrate surface, and finally the supporting medium is removed by dissolving with an organic solvent to complete the precise transfer of the thin slice. Optionally, the solution temperature and operating speed can be strictly controlled throughout the transfer process to avoid wrinkling or contamination of the thin slice.

[0033] like Figure 3 As shown, the thin slices prepared in this way exhibit clear morphological features under an optical bright field microscope. Figure 3 The arrows in the figure indicate the armchair and zigzag directions of the black phosphorus flakes, which are the lattice directions of the black phosphorus flakes. The atomic arrangement in the armchair direction presents a periodic, relatively flat pattern similar to the armchair edge, and its electronic structure has specific properties. Electron transport in this direction exhibits isotropic characteristics, and carrier mobility is less affected by direction. The atomic arrangement in the zigzag direction is zigzag-shaped, and its electronic properties (such as spin polarization and edge states) often show significant differences compared to the armchair direction. Unique spin-related edge states are easily formed at the zigzag edges, which are more sensitive to magnetic fields. This anisotropic electronic property is of great significance in plasmon control applications. The lattice direction can be intuitively judged by observing the edge morphology and color contrast of the flakes through near-field optical microscopy, providing a basis for subsequent device preparation and performance control.

[0034] After the prepared black phosphorus flake sample is placed on the microscope stage, it can be positioned under the needle tip through the system's built-in near-field optical microscope. In one embodiment, the substrate material of black phosphorus can be a gold substrate that has strong reflectivity to the pump laser. In this way, the absorption of the black phosphorus sample to the pump laser can be enhanced. This is because the gold substrate has high reflectivity in the near-infrared band and can form a standing wave field, which enhances the light intensity at the black phosphorus sample, thereby better improving the effect of spectral modulation. Preferably, the thickness of the black phosphorus sample is in the range of 100nm to 500nm. This thickness range can not only ensure sufficient carrier generation efficiency, but also avoid the problem of light absorption saturation caused by too thick samples.

[0035] The spectral modulation system induces the collective transition of valence band electrons to the conduction band through transient photoexcitation of near-infrared pump pulses. This inter-band transition process significantly increases the carrier concentration to 10 within a time scale of hundreds of femtoseconds. 19 cm -3 (Indicates that the number of particles per cubic centimeter is about 10 19 The dynamic process includes photon absorption, electron excitation, and hot electron relaxation. The peak power density of the pump pulse is sufficient to achieve efficient excitation. The mid-infrared probe light uses the near-field scattering effect and Fourier transform spectrometer to perform ultrafast spectral detection of transient changes in carrier concentration. The near-field scattering effect utilizes the local electromagnetic field enhancement at the probe tip to convert the change in dielectric constant caused by the change in carrier concentration into a change in scattered light intensity. The Fourier transform spectrometer collects the spectral information of the scattered light in real time.

[0036] Based on the pump-probe light system of the present invention, a technical solution for determining the energy density of the pump light activated by the propagation of plasmons in black phosphorus can be implemented, thereby providing a technical path that can be implemented in an engineering manner for the development of plasmon optical switches.

[0037] The basic principle of this invention is to utilize the dynamic process of photoinduced electron transitions in the black phosphorus band structure. When irradiated with a hundred-femtosecond pulse pump light with an energy of 0.8eV (corresponding to a wavelength of 1560nm), a significant inter-band electron transition effect is triggered: electrons at the top of the valence band absorb the photon energy and transition to the bottom of the conduction band, resulting in a transient change in the free carrier concentration in black phosphorus. This process can be quantitatively described by the Drude model: a sharp increase in carrier concentration will significantly change the plasmon frequency of the material. This directly affects the resonant properties of plasmons. It is particularly noteworthy that this light-induced dielectric constant control has non-equilibrium characteristics, and its time evolution process is closely related to the relaxation dynamics of carriers, providing a physical basis for the dynamic switching control of plasmons. Due to the ultra-short duration of the hundred-femtosecond pulse, high energy can be injected in a very short time, instantly breaking the equilibrium state of carriers in black phosphorus and creating a carrier concentration far higher than the thermal equilibrium state. This non-equilibrium state is the key to achieving dynamic control.

[0038] First, it is necessary to ensure that the pump light intensity is sufficient to support the detection light in the mid-infrared band to produce a plasmon response. The determination process uses a hundred-femtosecond pulse pump light, whose instantaneous energy injection can produce a non-equilibrium high carrier concentration distribution in black phosphorus. The hundred-femtosecond pulse is chosen because its pulse width is extremely short and the peak power is extremely high. It can transfer a large amount of energy to black phosphorus in an instant, stimulate enough electron transitions, and thus produce a significant change in carrier concentration. The pump light and the detection light can be emitted to black phosphorus. After ensuring that the pump light and the detection light are focused on the probe tip of the near-field optical microscope where black phosphorus is placed, the time delay between the pump light and the detection light can be adjusted and fixed. First, adjust the time delay between the pump light and the detection light. When the detection light time delay is ahead of the pump light (>0ps), the following can be detected: Figure 4 The curve of the near-field signal intensity changing rapidly with the delay is shown, where S3 represents the near-field signal intensity. By precisely adjusting the optical delay line, the pump light and the detection light pulse time coincide at 0ps, and a near-field signal intensity enhancement effect lasting about 1ps appears. In particular, the S3 order near-field signal intensity is observed to double (increase by about 100%) during the time of 0-0.2ps (corresponding to the complete coincidence of the pump and detection pulse times). This phenomenon is due to the instantaneous modulation of the plasmon mode by the light-injected carriers. In the subsequent time evolution process, the system exhibits typical non-equilibrium relaxation characteristics: rapid signal decay is observed in the range of 0.2-6ps (reflecting the carrier relaxation process, at which time the high concentration of carriers gradually returns to the equilibrium state through mechanisms such as scattering), followed by a slow recovery over a long time scale of more than 60ps. In one embodiment, the time delay between the pump light and the detection light can be fixed at 0.2ps, because according to Figure 4It can be seen that a significant enhancement of the near-field signal occurs at a delay of approximately 0.2 ps. This is because the carrier concentration reaches a relative peak at 0.2 ps. At this time, the plasmon frequency is modulated to the optimal state, which can produce the most significant response to the detection light, ensuring that subsequent experiments are carried out under conditions of sufficient carrier concentration.

[0039] Next, we can combine the near-field Fourier transform spectroscopy module to further verify whether the pump light intensity is sufficient. The near-field Fourier transform spectroscopy can directly reflect the plasmon response in the material through the intensity and phase peak position. Figure 5A and 5B The figure shows the energy density of the pump light at different pump light densities (0.2ps, Figure 4 The normalized Fourier transform spectrum of the detection light at the peak of the near-field optical signal, where S 3,BP is the signal strength of black phosphorus, S 3,Si is the signal strength of the silicon substrate, Φ 3,BP is the phase of black phosphorus, Φ 3,Si is the phase of the silicon substrate, and arb.units means no unit. When the pump energy density is 0, due to the extremely low intrinsic carrier concentration of black phosphorus itself, its intensity spectrum ( Figure 5A ) and phase spectrum ( Figure 5B ) are all flat, with no plasmon response characteristics. When the pump energy density is 0.42mJ / cm2, Figure 5A The intensity spectrum of shows an obvious tilt, and the low-wavenumber near-field signal intensity is significantly higher than the high-wavenumber near-field signal intensity; similarly, Figure 5B The phase spectrum also undergoes significant changes: a distinct Lorentzian-like peak appears, occurring within the probe light frequency range, indicating that the photoinduced carrier concentration is sufficient to generate a plasmon response within the observed wavenumber range. The presence of the Lorentzian peak indicates resonance in the system, meaning that the plasmons resonate with the probe light. This directly demonstrates that the carrier concentration is sufficient to modulate the plasmon frequency to the probe light frequency range, resulting in effective interaction.

[0040] After ensuring that the carrier concentration is sufficient, the optical switching of the propagating state plasmon in black phosphorus can be realized. However, the spectrum alone cannot directly determine whether the carrier concentration is sufficient for optical switching. In some embodiments, a near-field optical scanning microscope can be used to directly characterize the optical switching phenomenon of the propagating state plasmon in black phosphorus. First, the time delay needs to be adjusted to Figure 4 The corresponding near-field signal peak is then detected at the edge of the black phosphorus to obtain the state of the black phosphorus surface. In some embodiments, a scanning detection can be performed near the sample boundary to obtain a detection interference fringe pattern of plasmons in the black phosphorus. Next, the pump light energy density is adjusted so that plasmon propagation occurs on the black phosphorus surface. Figure 6As shown, when 0.42mJ / cm 2 Under the condition of pump light, clear plasmon propagation stripes can be seen in the near-field scanning results, which corresponds to the "on" state of the plasmon optical switch. In addition, the energy density is equal to the pump light energy density at which the plasmon resonance peak can be measured in the Fourier spectrum experiment in Figure 5, which also confirms the effectiveness of this energy density; at 0mJ / cm 2 Under pump light conditions (i.e., without pump light injection), the surface of the black phosphorus sample does not support plasmon propagation, corresponding to the "off" state of the plasmon optical switch. This significant on / off ratio confirms the effective manipulation of the propagation state of black phosphorus plasmons by optical modulation. When pump light is injected, the carrier concentration increases, and the plasmon frequency is modulated to match the probe light, thus creating propagation conditions. In the absence of pump light, the carrier concentration is low and cannot support plasmon propagation in this frequency band, thus achieving the switching function.

[0041] In addition, the propagating plasmons in black phosphorus also exhibit excellent low-loss transmission characteristics. Figure 7 As shown, the plasmon interference fringe morphology obtained under optical pumping conditions shows that its propagation distance exceeds 8μm. Through fringe fitting calculation, its transmission quality factor (Q value) can reach 20, which is significantly better than the traditional noble metal-based plasmon system, confirming the unique advantages of black phosphorus in the field of electromagnetic waveguides. The quality factor Q value reflects the energy loss of plasmons during propagation. The higher the Q value, the lower the loss. Traditional noble metals such as gold and silver have low Q values ​​due to factors such as electron scattering, while black phosphorus achieves high Q value transmission with its unique electronic structure and low defect characteristics. In one embodiment, the plasmon wavelength is compressed to the submicron scale (λ<1μm). This characteristic parameter reveals that the material system has a strong field localization capability that breaks the diffraction limit. This strong field localization capability gives black phosphorus huge application potential in optical integrated devices, super-resolution imaging and other fields, and can achieve efficient manipulation of light within an extremely small spatial scale.

[0042] After obtaining the energy density of the pump light that can excite the propagating state plasmons in black phosphorus, a control scheme for the optical switching effect based on black phosphorus can be implemented based on this. In one embodiment, pump light with a specific energy density can be emitted to black phosphorus as needed to allow the optical signal to propagate through the black phosphorus; and the pump light can be turned off as needed to prevent the optical signal from propagating through the black phosphorus. In one embodiment, the pump light of this specific energy density can cause plasmon propagation on the surface of black phosphorus, and the specific specific energy density can be determined according to the aforementioned relevant embodiments of the present invention. This technical solution provides an engineering-implementable solution for the development of optical switching devices based on black phosphorus. For example, in optical communication systems, this optical switch can be used to quickly switch the optical signal path, with faster response speed and lower power consumption compared to traditional mechanical switches or other optical switching technologies.

[0043] In some embodiments, such an optical switch device may include black phosphorus, such as the aforementioned black phosphorus flakes, and the optical switch device may have an on state and an off state. Specifically, when pump light with a specific energy density is emitted into the black phosphorus to allow optical signals to propagate through the black phosphorus, the optical switch device is in the on state; when the pump light is turned off to prevent the optical signal from propagating through the black phosphorus, the optical switch device is in the off state. The pump light with the specific energy density can cause plasmon propagation on the black phosphorus surface. Similarly, the specific specific energy density can be determined according to the aforementioned related embodiments of the present invention. In practical applications, the black phosphorus flakes can be integrated into optical chips, and the emission and shutoff of the pump light can be controlled by external circuits to achieve high-speed switching of optical signals, providing key device support for next-generation optical communications and optical computing technologies.

[0044] Based on the pump-probe light system of the present invention, a technical solution for establishing a quantitative mapping model of time delay parameters and plasmon frequencies can be implemented, thereby providing a technical path that can be implemented in an engineering manner for the development of ultrafast light control devices. The core of the pump-probe technology is to use pump light to excite the material to produce a transient response, and then perform time-resolved measurement of this dynamic process, wherein the precise control of the time delay parameter is the key to capturing the ultrafast response characteristics of the material. After the pump light and the probe light are emitted to black phosphorus and the pump light and the probe light are focused to the probe tip, the time delay between the pump light and the probe light is adjusted, and a curve of the near-field signal intensity that changes rapidly with time delay can be detected when the probe light time delay precedes the pump light (>0ps). The focusing design of the probe tip can utilize the near-field enhancement effect to highly confine the light field energy to the nanoscale region, thereby significantly improving the detection sensitivity of the black phosphorus plasmon response, which is crucial for capturing weak signals at the femtosecond time scale.

[0045] The spectrum of the black phosphorus plasmon response is then monitored. Preferably, Fourier transform spectroscopy can be used to monitor the transient spectral evolution of the black phosphorus plasmon response in real time. Fourier transform spectroscopy converts the time-domain interference signal into the frequency domain, enabling the simultaneous acquisition of spectral phase and intensity information without sacrificing temporal resolution. This technique is particularly suitable for analyzing the dynamic drift of the plasmon resonance frequency on ultrafast time scales. By regulating the timing relationship between the pump and probe pulses through a high-precision linear displacement platform, the system can accurately scan the time delay parameter in steps of 200 fs, synchronously acquire the time-domain interference signal at different delay moments, and demodulate the normalized spectral characteristics.

[0046] The transient evolution of the plasmon response under typical time delays can be reflected based on the intensity spectrum and phase spectrum. In the intensity spectrum, the comparison of the black phosphorus signal and the gold substrate signal can intuitively reflect the difference between the intrinsic response of the material and the substrate background. The peak position change of the phase spectrum is more sensitive to carrier concentration and lattice dynamics, becoming a key indicator for accurately tracking the drift of the plasmon resonance frequency. When the time delay increases from 0ps, the plasmon resonance phase peak shows a reversible redshift characteristic, and its frequency control range covers 0-1400cm -1 The phase peak shift exhibits a nonlinear response relationship with the time delay parameter across the wavelength band. This redshift phenomenon originates from the dynamic modulation of the black phosphorus Fermi level caused by pump light excitation, which causes the plasmon resonance conditions to change with the carrier relaxation process. The nonlinear response reflects the combined influence of complex ultrafast processes such as multi-phonon scattering and carrier-photon interaction.

[0047] Based on the time delay between the pump and probe beams and the monitored spectrum of the black phosphorus plasmon response, a quantitative mapping model is established to correlate the time delay between the pump and probe beams with the plasmon frequency. In some embodiments, this quantitative mapping model can include a quantitative relationship between the time delay and the plasmon frequency. This model can then be used to predict the plasmon frequencies generated by varying pump-probe delays, providing a foundation for actively manipulating the properties of black phosphorus plasmons.

[0048] By using the established quantitative mapping model of the time delay between the pump light and the probe light and the plasmon frequency, after the pump light and the probe light are emitted into black phosphorus, the time delay between the pump light and the probe light can be adjusted based on the predetermined quantitative mapping model to achieve modulation of the spectrum of the black phosphorus plasmon response. This modulation method is essentially a dynamic regulation of the carrier concentration and energy state of the material through timing control. Compared with traditional temperature or electric field modulation methods, it has significant advantages of femtosecond time resolution and nanometer-scale spatial localization. This modulation method can also be further used to design tunable optoelectronic devices. In the design of optoelectronic devices, the controllable adjustment of the plasmon frequency means that key parameters such as the device's response wavelength and modulation bandwidth can be optimized in real time, thereby meeting the diverse requirements of spectral characteristics in different application scenarios. In some embodiments, such tunable optoelectronic devices can include black phosphorus, such as the aforementioned black phosphorus flakes, and thus adjust the output characteristics of the optoelectronic device by adjusting the time delay between pump light and probe light irradiating the black phosphorus. Similarly, the time delay between the pump light and probe light can be adjusted using a quantitative mapping model between the time delay between the pump light and probe light and the plasmon frequency, established using the aforementioned method. Taking plasmon modulators as an example, by integrating a high-precision delay control module with black phosphorus nanostructures, ultrafast modulation of optical signals can be achieved, with broad application prospects in high-speed optical communications and on-chip optical signal processing.

[0049] Based on the pump-probe light system of the present invention, a technical solution for establishing a quantitative mapping model between pump light power density and plasmon frequency can be implemented, thereby providing a technical path that can be implemented in an engineering way for the development of ultrafast light control devices. As a key control parameter for the interaction between light and matter, the dynamic modulation of pump light power density can directly change the excitation density and energy distribution of carriers in black phosphorus, thereby affecting the resonance conditions of plasmons. First, the pump light and probe light are still emitted to black phosphorus. Then the pump light power density can be adjusted, and the light power density can also be called the light energy density. The adjustment of power density can be achieved by an electrically controlled attenuator combined with real-time closed-loop feedback of a power meter. In some embodiments, the resolution adjustment of 0.1 mW / cm2 can be performed in the range of 0 to 30 mW / cm2. In some embodiments, the pump light power density can be adjusted under fixed pump-probe time delay conditions.

[0050] Next, we can monitor the spectrum of the black phosphorus plasmon response. Based on the normalized intensity spectrum and phase response spectrum of the plasmon near-field response spectrum when the pump energy continuously changes in the range of 0-30mW, it can be seen that when the pump power density increases in a gradient, the plasmon resonance peak shows a significant blue shift characteristic, and its spectral control range covers 0-1400cm -1The physical mechanism of the blueshift phenomenon stems from the fact that high-power-density pump light excites more free carriers, leading to an increase in the Fermi level of black phosphorus and, in turn, an increase in the plasmon oscillation frequency. In particular, the phase peak shift trajectory maintains a strict correspondence with the intensity spectrum, demonstrating the physical consistency of the modulation process. Phase information is more sensitive to carrier-lattice interactions, and its synchronous changes with the intensity spectrum verify the stability of the plasmon resonance mode under power-density modulation.

[0051] Based on the pump light power density and the monitored spectrum of the black phosphorus plasmon response, a quantitative mapping model or relationship between pump light power density and plasmon frequency is established. In some embodiments, the quantitative mapping model can include a quantitative relationship between pump light power density and plasmon frequency. This model can then be used to predict the plasmon frequencies that can be generated by different pump light power densities, providing a basis for actively controlling the properties of black phosphorus plasmons. The model prediction error can be controlled within 3%, meeting the accuracy requirements of engineering applications.

[0052] By using a well-established quantitative mapping model between pump light power density and plasmon frequency, after emitting pump and probe light into black phosphorus, the pump light power density can be adjusted based on this predetermined quantitative mapping model to achieve spectral modulation of the black phosphorus plasmon response. This technical solution provides an engineering-implementable solution for the development of tunable optoelectronic devices based on the black phosphorus plasmon effect. This control mechanism can achieve dynamic and reconfigurable spectral modulation by constructing a pump light power density control system. The power density control system can achieve wide-range continuous modulation while maintaining beam quality, which is suitable for the needs of on-chip integrated optoelectronic devices.

[0053] In some embodiments, such a tunable optoelectronic device may include black phosphorus, such as the aforementioned black phosphorus flakes, etc., so that the output characteristics of the optoelectronic device can be adjusted by adjusting the pump light power density irradiated on the black phosphorus. Similarly, when adjusting the pump light power density, the quantitative mapping model of pump light power density and plasmon frequency established by the aforementioned method can be used to adjust it. In addition, those skilled in the art will understand that the quantitative mapping model of time delay and plasmon frequency described in the aforementioned embodiment can be used in conjunction with the quantitative mapping model of pump light power density and plasmon frequency described in this embodiment to modulate the spectrum, so that the time delay between the pump light and the probe light and / or the pump light power density can be adjusted based on the predetermined quantitative mapping model of time delay and plasmon frequency between the pump light and the probe light and / or the quantitative mapping model of pump light power density and plasmon frequency, thereby achieving modulation of the spectrum of the black phosphorus plasmon response or modulation of the output characteristics of the optoelectronic device. This multi-parameter collaborative control strategy can construct more complex plasmon modulation paths in the time-energy two-dimensional space, such as achieving ultrafast spectral switching through time delay scanning at a fixed power density, or achieving spectral amplitude modulation through power density modulation at a fixed delay, providing a flexible control dimension for the design of multifunctional optoelectronic devices.

[0054] Figure 8 FIG. 8 is a flow chart showing an exemplary method 800 according to an exemplary embodiment of the present disclosure. Figure 8 Method 800 may include: step 810, emitting pump light and probe light into the black phosphorus material; step 820, adjusting and fixing the time delay between the pump light and the probe light; step 830, performing scanning detection at the edge of the black phosphorus to obtain the state of the black phosphorus surface; and step 840, adjusting the energy density of the pump light to allow plasmon propagation on the black phosphorus surface. Method 800 may be performed using the aforementioned system, and may include the method steps involved in any of the aforementioned embodiments.

[0055] In some embodiments, the time delay between the pump light and the probe light can be adjusted and fixed to 0 picosecond to 1 picosecond.

[0056] In some embodiments, the time delay between the pump light and the probe light can be adjusted and fixed to 0.2 picoseconds.

[0057] In some embodiments, the pump light may include a hundred-femtosecond pulsed pump light.

[0058] Figure 9 FIG. 9 is a flow chart showing an exemplary method 900 according to an exemplary embodiment of the present disclosure. Figure 9Method 900 may include: step 910, placing a black phosphorus crystal in a glove box; step 920, using a mechanical exfoliation technique to directionally exfoliate the black phosphorus crystal to form a black phosphorus crystal sheet; and step 930, transferring the black phosphorus crystal sheet to a silicon substrate surface. Method 900 may be performed using the aforementioned system, and may include the method steps described in any of the aforementioned embodiments.

[0059] In some embodiments, the glove box may include a high purity nitrogen or inert gas glove box.

[0060] In some embodiments, rectangular black phosphorus crystal flakes can be obtained by directional exfoliation by controlling the cleavage direction.

[0061] In some embodiments, the thickness of the black phosphorus crystal flakes may be between 100 nm and 500 nm.

[0062] Figure 10 FIG. 1 is a flow chart showing an exemplary method 1000 according to an exemplary embodiment of the present disclosure. Figure 10 Method 1000 may include: step 1010, emitting pump light having a specific energy density into black phosphorus to allow optical signals to propagate through the black phosphorus; and step 1020, shutting off the pump light to prevent the optical signals from propagating through the black phosphorus. In some embodiments, the pump light having a specific energy density may be pump light capable of generating plasmon propagation on the black phosphorus surface. Method 1000 may be performed using the aforementioned system, and may include the method steps described in any of the aforementioned embodiments.

[0063] Those skilled in the art will appreciate that step 1010 and step 1020 in method 1000 are methods for adjusting two states of the optical switch and have no strict order.

[0064] Figure 11 FIG. 1 shows an example block diagram of a system 1100 including an optical switching device according to an exemplary embodiment of the present disclosure. Figure 11 As shown, the system includes an optical switch device 1102, black phosphorus 1104 located in the optical switch device 1102, and a pump light source 1110. As a light source for activating the black phosphorus 1104, the pump light source 1110 can be placed inside or outside the optical switch device. The optical switch device 1100 has an on state and an off state. When pump light with a specific energy density is emitted to the black phosphorus to allow the optical signal 1106 to propagate through the black phosphorus, the optical switch device is in the on state; conversely, when the pump light is turned off to prevent the optical signal 1106 from propagating through the black phosphorus, the optical switch device is in the off state. The pump light with a specific energy density can cause plasmon propagation on the black phosphorus surface.

[0065] According to an exemplary embodiment of the present disclosure, a black phosphorus-based spectral modulation method may include: emitting pump light and probe light into the black phosphorus material; adjusting the time delay between the pump light and the probe light; monitoring the spectrum of the black phosphorus plasmon response; and establishing a quantitative mapping model between the time delay between the pump light and the probe light and the plasmon frequency. This method may be performed using the aforementioned system and may include the method steps described in any of the aforementioned embodiments.

[0066] In some embodiments, Fourier transform spectroscopy can be used to monitor the transient spectrum of the plasmon response in black phosphorus in real time.

[0067] In some embodiments, when monitoring the spectrum of the black phosphorus plasmon response, the time delay parameter can be scanned, the time domain interference signals at different delay moments can be synchronously collected, and the normalized spectral features can be demodulated.

[0068] According to an exemplary embodiment of the present disclosure, a black phosphorus-based spectral modulation method may include: emitting pump light and probe light into the black phosphorus material; adjusting the pump light power density; monitoring the spectrum of the black phosphorus plasmon response; and establishing a quantitative mapping model between the pump light power density and the plasmon frequency. This method may be performed using the aforementioned system and may include the method steps described in any of the aforementioned embodiments.

[0069] According to an exemplary embodiment of the present disclosure, a black phosphorus-based spectral modulation method may include: emitting pump light and probe light into a black phosphorus material; and adjusting the time delay between the pump light and the probe light and / or adjusting the pump light power density. This method may be performed using the aforementioned system and may include the method steps described in any of the aforementioned embodiments.

[0070] In some embodiments, the time delay between the pump light and the probe light and / or the pump light power density can be adjusted based on a predetermined quantitative mapping model of the time delay between the pump light and the probe light and the plasmon frequency and / or a predetermined quantitative mapping model of the pump light power density and the plasmon frequency. The present invention specifically describes how to create the quantitative mapping model in some embodiments and will not be repeated here.

[0071] According to an exemplary embodiment of the present disclosure, a system based on a tunable optoelectronic device may include: a tunable optoelectronic device, black phosphorus located in the tunable optoelectronic device, and a pump light source and a detection light source. As a light source for activating black phosphorus, the pump light source can be placed inside or outside the tunable optoelectronic device; similarly, the detection light source can also be placed inside or outside the tunable optoelectronic device. The tunable optoelectronic device has an output, and the characteristics of the output of the optoelectronic device are adjusted by adjusting the time delay between the pump light and the detection light irradiated on the black phosphorus and / or adjusting the power density of the pump light.

[0072] In this disclosure, “at least one of: <two or more listed elements>” and “at least one of <two or more listed elements>” and similar expressions, where two or more listed elements are connected with “and” or “or”, mean at least any one of these elements, or at least any two or more of these elements, or at least all of these elements.

[0073] The basic principles of the present disclosure have been described above in conjunction with the embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this disclosure are merely illustrative and not restrictive, and should not be construed as necessarily possessed by each embodiment of the present disclosure. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, rather than as limitations. These details do not limit the present disclosure to necessarily being implemented using these specific details.

[0074] The block diagrams of the devices and systems involved in this disclosure are intended to be illustrative examples only and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "including," "comprising," "having," and the like are open-ended words that mean "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0075] In addition, in the apparatus and method of the present disclosure, each component or each step can be decomposed and / or recombined, and such decomposition and / or recombination should be regarded as equivalent solutions of the present disclosure.

[0076] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0077] The above description has been given for the purpose of illustration and description, and this description is not intended to limit the embodiments of the present disclosure to the form disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

[0078] For those skilled in the relevant art, after reading the specification, claims and drawings of this document, they can recognize the relevance of the multiple embodiments of this document, and thus can obtain other embodiments that are not directly described in the text but have been implied by this document by combining multiple embodiments, or can incorporate all or part of the contents of one or more embodiments into one or more other embodiments to expand the contents of these embodiments.

Claims

1. A method for controlling the optical switching effect based on black phosphorus, comprising: launching pump light and probe light into black phosphorus; Adjust and fix the time delay between pump light and probe light; Scanning detection is performed on the edge of black phosphorus to obtain the state of the black phosphorus surface; Adjust the energy density of the pump light to allow plasmon propagation on the black phosphorus surface.

2. The optical switch effect control method according to claim 1, wherein: The adjusting and fixing the time delay between the pump light and the probe light includes: The time delay between the pump light and the probe light was adjusted and fixed to 0 picosecond to 1 picosecond.

3. The optical switch effect control method according to claim 2, wherein: The adjusting and fixing the time delay between the pump light and the probe light includes: The delay between the pump light and the probe light was adjusted and fixed to 0.2 picoseconds.

4. The optical switch effect control method according to claim 1, wherein: The pump light includes hundred-femtosecond pulse pump light.

5. A method for preparing a black phosphorus flake, comprising: Place the black phosphorus crystals in a glove box; The black phosphorus crystals are directionally exfoliated to form black phosphorus crystal flakes using mechanical exfoliation technology; Transferring a thin sheet of black phosphorus crystals to the surface of a silicon substrate.

6. The method for preparing black phosphorus flakes according to claim 5, wherein: The glove box includes a high-purity nitrogen or inert gas glove box.

7. The method for preparing black phosphorus flakes according to claim 5, wherein: The method of using a mechanical exfoliation technique to directionally exfoliate black phosphorus crystals to form black phosphorus crystal flakes comprises: Rectangular black phosphorus crystal flakes were obtained by controlling the cleavage direction for directional exfoliation.

8. The method for preparing black phosphorus flakes according to claim 5, wherein: The thickness of the black phosphorus crystal sheet is 100 nm to 500 nm.

9. A method for controlling a black phosphorus optical switching effect, comprising: launching pump light with a specific energy density into the black phosphorus to allow the optical signal to propagate through the black phosphorus; as well as Turn off the pump light to prevent the optical signal from propagating through black phosphorus; The pump light of the specific energy density can generate plasmon propagation on the surface of black phosphorus.

10. A black phosphorus-based optical switching device, comprising: Black phosphorus; The optical switch device has an on state and an off state; When pump light with a specific energy density is emitted into the black phosphorus to allow an optical signal to propagate through the black phosphorus, the optical switch device is in an open state; When the pump light is turned off to prevent the optical signal from propagating through the black phosphorus, the optical switch device is in an off state; The pump light of the specific energy density can generate plasmon propagation on the surface of black phosphorus.

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