Femtosecond light-induced plasmon wide-spectrum ultrafast regulation and control based on black phosphorus

Abstract

The invention discloses femtosecond light-induced plasmon wide-spectrum ultrafast regulation and control based on black phosphorus. An exemplary black phosphorus-based spectrum modulation method comprises the following steps: emitting pump light and probe light to black phosphorus; 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 of the time delay between the pump light and the probe light and the plasmon frequency based on the time delay between the pump light and the probe light and the monitored spectrum of the black phosphorus plasmon response. According to the invention, the core defects of narrow dynamic range, limited response speed and single regulation dimension in the existing plasmon spectrum regulation technology are overcome, and broadband and high-speed spectrum dynamic reconstruction is realized through a photoinduced non-equilibrium state carrier injection mechanism.

Description

Technical Field

[0001] The present invention belongs to the field of laser technology, and in particular relates to ultrafast broad-spectrum control of femtosecond photoinduced plasmons based on black phosphorus, as well as related methods and equipment. Background Art

[0002] Plasmon response, a collective oscillation effect of free carriers coupled to electromagnetic fields in metals or semiconductors, interacts with light spectrum to provide a unique mechanism for nanoscale light field manipulation. Plasmon-based spectral properties stem from the synergistic effect of local electromagnetic field enhancement and resonant modes: when the incident photon frequency matches the material's carrier oscillation frequency, surface plasmon resonance is stimulated at a specific wavelength, manifesting as a significant light absorption peak or enhanced scattering.

[0003] Traditional spectral modulation technologies mainly rely on the static dielectric properties or fixed geometric structures of materials, and achieve spectral shifts within a limited range through means such as localized plasmon resonance of metal nanostructures and semiconductor carrier concentration adjustment. However, such methods generally have bottlenecks such as limited modulation speed (milliseconds to seconds), narrow dynamic range (wavelength shift <100nm), and difficulty in achieving multi-dimensional coordinated control. Summary of the Invention

[0004] 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.

[0005] In a first aspect, a black phosphorus-based spectral modulation method is provided, which may include: emitting pump light and probe light into black phosphorus; 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 based on the time delay between the pump light and the probe light and the monitored spectrum of the black phosphorus plasmon response.

[0006] Secondly, another black phosphorus-based spectral modulation method is provided, including: emitting pump light and probe light into black phosphorus; 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 based on the pump light power density and the monitored spectrum of the black phosphorus plasmon response.

[0007] In a third aspect, a high-performance black phosphorus-based spectral modulation system is provided, which may include: a pump light source module for outputting pump light; a detection light source module for outputting detection light; a pump light delay module for adjusting the delay of the pump light; a detection light delay module for adjusting the delay of the detection light; a near-field optical microscope module for carrying black phosphorus and coupling the pump light and the detection light; and a Fourier transform spectroscopy module for real-time monitoring of the spectrum.

[0008] In a fourth aspect, another black phosphorus-based spectral modulation method is provided, comprising: emitting pump light and probe light into black phosphorus; adjusting the time delay between the pump light and the probe light and / or adjusting the pump light power density to achieve modulation of the spectrum of the black phosphorus plasmon response.

[0009] In a fifth aspect, a tunable optoelectronic device is provided, comprising: black phosphorus; wherein the output characteristics 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The following will be described in more detail with reference to the embodiments and drawings, wherein:

[0011] 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.

[0012] 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.

[0013] Figure 3 A schematic diagram showing a black phosphorus flake sample according to an exemplary embodiment of the present disclosure placed on a microscope stage.

[0014] Figure 4A A schematic diagram showing the normalized intensity spectrum of the transient evolution law of the plasmon response under typical time delay of an exemplary embodiment of the present disclosure.

[0015] Figure 4B A schematic diagram of a phase response spectrum showing the transient evolution law of plasmon response under typical time delay of an exemplary embodiment of the present disclosure is shown.

[0016] Figure 5A A schematic diagram showing the normalized intensity spectrum of the plasmon near-field response spectrum evolution when the pump energy varies continuously according to an exemplary embodiment of the present disclosure.

[0017] Figure 5B A schematic diagram showing the phase response spectrum of the plasmon near-field response spectrum evolution when the pump energy varies continuously according to an exemplary embodiment of the present disclosure.

[0018] Figure 6 A flow chart of an exemplary method 600 according to an exemplary embodiment of the present disclosure is shown.

[0019] Figure 7 A flow chart of an exemplary method 700 according to an exemplary embodiment of the present disclosure is shown.

[0020] Figure 8 A flow chart of an exemplary method 800 according to an exemplary embodiment of the present disclosure is shown.

[0021] Figure 9 An example block diagram of a system 900 including a tunable optoelectronic device according to an example embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0022] 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.

[0023] 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.

[0024] 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".

[0025] In the existing technology, the spectral regulation of plasmons mainly relies on the combination of inherent material properties and external static control methods. Metal nanostructures (such as gold and silver nanoparticles) can achieve field enhancement and scattering control at specific wavelengths in the visible to near-infrared band through the localized surface plasmon resonance effect, but their resonant frequency is limited by the fixed design of geometric shape and size. Dynamic regulation requires relying on complex micro-control systems or macroscopic deformation methods such as mechanical stretching, resulting in low response speed and limited wavelength displacement range. Semiconductor materials (such as silicon and germanium) control the carrier concentration through electrochemical gate voltage. Although they can achieve active regulation of the dielectric constant in the mid-infrared band, they are limited by the electrical response speed, and the control bandwidth is limited to the kilohertz to megahertz level, and an integrated electrode structure is required, which makes it difficult to meet the needs of high-speed photonic devices. In recent years, the combination of ultrafast optical excitation and two-dimensional van der Waals materials has provided a new path for dynamic spectral control: using femtosecond laser pulses to induce transient non-equilibrium carriers in transition metal sulfides, the active shift of the polariton resonance wavelength can be achieved through the dynamic reconstruction of the dielectric function on the picosecond time scale. However, the resonance wavelength control range is usually less than 1000 cm -1 In addition, although plasmon control based on novel materials such as topological insulators has shown the potential for wide-spectrum response, the competition mechanism between surface and bulk carriers has not been fully clarified, which restricts the accuracy and stability of spectral control. The current technological frontier focuses on the collaborative innovation of ultrafast pump-probe technology and near-field optical imaging, aiming to break through the bottlenecks of traditional control methods in speed, range and coordinated control of multi-dimensional parameters through spatiotemporal resolution of carrier dynamics and visualization of nanoscale plasmon field distribution.

[0026] The purpose of this invention is to overcome the core defects of existing plasmon spectral control technologies, such as narrow dynamic range, limited response speed, and single control dimension, and to achieve wide-band, high-speed spectral dynamic reconstruction through a photoinduced non-equilibrium carrier injection mechanism. In view of the limitations of traditional metal / semiconductor materials that rely on static structures or slow electrical control, a light-controlled switching strategy based on black phosphorus plasmon modes is proposed. By utilizing the transient change characteristics of the dielectric function induced by femtosecond lasers, a spectral shift of more than 1500 cm in the mid-infrared to terahertz band (6-300μm) is achieved in a single sample system. -1 By precisely controlling the pump light power, polarization state, and time delay parameters, this method breaks through the traditional method's reliance on a single control dimension (wavelength or intensity), providing a new control paradigm with both wide spectral adaptability and nanometer spatial precision for super-resolution spectral imaging, reconfigurable photonic chips, and high-speed optical interconnect systems.

[0027] Figure 1A 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.

[0028] 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.

[0029] 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.

[0030] After the pump light and the detection light are collimated and optimized by the collimation module, they need to be coupled to a scattering near-field optical microscope system (spatial resolution <20nm) and pass through an infrared Fourier transform spectroscopy module. The collimation optimization process can adjust the position of the collimating lens to make the divergence angle of the light beam less than 1 milliradian, ensuring efficient light coupling in the near-field region. In some embodiments, the spatial overlap of the pump and detection light spots at the tip of the near-field probe can be achieved by adjusting the built-in parabolic objective lens of the near-field optical microscope. The parabolic objective lens has a spherical aberration design that can focus the two beams of light onto the sub-wavelength scale of the probe tip. Finally, as Figure 3 As shown, the prepared black phosphorus flake sample can be placed on a microscope stage and positioned below the needle tip through the system's built-in near-field optical microscope. Preferably, 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 a 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 spectral modulation effect. 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] Figure 4A and Figure 4B The transient evolution of plasmon response under typical time delay is shown, where S 3,BPis the signal strength of black phosphorus, S 3,Au is the signal strength of the gold substrate, Φ 3,BP is the phase of black phosphorus, Φ 3,Au is the phase of the gold substrate. Figure 4A The dynamic evolution of the intensity spectrum with the delay time is presented. Figure 4B The resonance characteristics are quantified by the phase spectrum, showing the corresponding relationship between the near-field phase peak position (dashed line mark) and the plasmon resonance frequency. 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 the carrier concentration and lattice dynamics, becoming a key indicator for accurately tracking the drift of the plasmon resonance frequency. It can be seen that 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The spectrum of the black phosphorus plasmon response can then be monitored. Figure 5A and Figure 5B The evolution of the plasmon near-field response spectrum when the pump energy continuously changes from 0 to 30 mW is shown. Figure 5A and Figure 5B They correspond to the normalized intensity spectrum and phase response spectrum respectively, and the dotted line in the phase response spectrum shows the phase peak displacement trajectory. Figure 5A and Figure 5B As shown in Figure 2, when the pump power density increases in a gradient, the plasmon resonance peak exhibits a significant blue shift characteristic, and its spectral control range covers 0-1400 cm -1 The 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Before implementing the black phosphorus-based femtosecond photo-induced plasmon wide-spectrum ultrafast control technology solution provided by the present invention, it is necessary to prepare a suitable black phosphorus material. As a two-dimensional material with a layered structure, black phosphorus is extremely sensitive to the environment in its physical and chemical properties, especially in the air, where it is very susceptible 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 performed in a high-purity nitrogen or inert gas glove box (O2 / H2O concentration is strictly controlled to <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 that an inert environment is continuously maintained by a gas circulation system and a desiccant in the glove box. In some embodiments, an online gas analyzer can also be provided to monitor the oxygen and water vapor concentrations in real time to ensure the stability of the preparation environment.

[0043] Then, mechanical exfoliation technology is used to directionally exfoliate the bulk black phosphorus crystal to form black phosphorus crystal flakes. The mechanical exfoliation 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 can be achieved by repeatedly sticking and exfoliating with sticky tape. The lattice directions of the black phosphorus flakes include armchair and zigzag directions. Among them, the atomic arrangement in the armchair direction presents a periodic and relatively flat pattern similar to the armchair edge, and its electronic structure has specific properties. The electron transport in this direction shows isotropic characteristics, and the carrier mobility is less affected by the direction; while the atomic arrangement in the zigzag direction is zigzag-shaped, and compared with the armchair direction, its electronic properties (such as spin polarization, edge states, etc.) often show obvious differences. Unique spin-related edge states are easily formed at the zigzag edges, which are more sensitive to magnetic field responses. This anisotropic electronic property is of great significance in plasmon regulation applications. 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. Peeling along the long axis 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 peeling medium. The bulk crystal is pressed on the tape and quickly torn off. The crystal thickness is gradually thinned by repeating the peeling process many times until a nanoscale flake that meets the requirements is obtained. In this process, the thickness and edge morphology of the flake can be observed in real time with the help of a near-field optical microscope to ensure the accuracy of the peeling direction.

[0044] 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.

[0045] The thin films prepared in this way can display clear morphological features under optical bright-field microscopy. The edge morphology and color contrast of the thin films can be observed by near-field optical microscopy to intuitively determine their lattice orientation, providing a basis for subsequent device preparation and performance control.

[0046] Based on the pump-probe light system of the present invention, a technical solution for determining the energy density of the pump light that activates the propagation of plasmons in black phosphorus can be implemented, thereby providing a technical path that can be implemented in an engineering way for the development of plasmon optical switches. The basic principle is to utilize the dynamic process of photoinduced electron transitions in the band structure of black phosphorus. 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: the electrons at the top of the valence band absorb the photon energy and then 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.

[0047] First, it is necessary to ensure that the pump light intensity is sufficient to support the plasmon response of the probe light in the mid-infrared band. 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 it has an extremely short pulse width and extremely high peak power, which can transfer a large amount of energy to black phosphorus in an instant, stimulating enough electron transitions to produce a significant change in carrier concentration. The pump light and the probe light can be emitted into black phosphorus. After ensuring that the pump light and the probe light are focused on the probe tip of the near-field optical microscope where the black phosphorus is placed, the time delay between the pump light and the probe light can be adjusted and fixed. First, adjust the time delay between the pump light and the probe light. When the time delay of the probe light precedes that of the pump light (>0ps), a curve showing the rapid change of the near-field signal intensity with the delay can be detected. By precisely adjusting the optical delay line, the pump light and the probe light pulses are time-coincident at 0ps, resulting in a near-field signal intensity enhancement effect lasting about 1ps. In particular, the S3-order near-field signal intensity is observed to double (increase by about 100%) in the 0-0.2ps time (corresponding to the complete overlap of the pump and probe pulse times). This phenomenon originates from 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: a rapid decay of the signal is observed in the 0.2-6ps range (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 probe light can be fixed at 0.2 ps, because a significant enhancement of the near-field signal occurs at a delay of about 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 probe light, and can ensure that subsequent experiments are carried out under conditions of sufficient carrier concentration.

[0048] Next, we can use the near-field Fourier transform spectroscopy module to further verify the adequacy of the pump light intensity. Near-field Fourier transform spectroscopy directly reflects the plasmon response in the material through the positions of intensity and phase peaks. The normalized Fourier transform spectrum of the probe light shows that at zero pump energy density, due to the extremely low intrinsic carrier concentration of black phosphorus, both the intensity and phase spectra are flat, with no plasmon response characteristics. When the pump energy density reaches 0.42 mJ / cm², the intensity spectrum exhibits a significant tilt, with the low-wavenumber near-field signal intensity significantly higher than the high-wavenumber near-field signal intensity. Similarly, the phase spectrum undergoes a significant change: a distinct Lorentzian line peak appears, and the phase peak occurs within the probe light frequency range, indicating that the photoinduced carrier concentration is sufficient to support plasmon response within the observed wavenumber range. The presence of the Lorentzian line peak indicates resonance in the system, i.e., resonant plasmon resonance with the probe light. This directly confirms that the carrier concentration is sufficient to modulate the plasmon frequency to the probe light frequency band, establishing an effective interaction.

[0049] After ensuring that the carrier concentration is sufficient, the optical control switching of the propagation state plasmons in black phosphorus can be realized. However, the spectrum alone cannot directly determine whether the carrier concentration is sufficient for optical control switching. In some embodiments, a near-field optical scanning microscope can be used to directly characterize the optical switching phenomenon of the propagation state plasmons in black phosphorus. First, the time delay needs to be adjusted to the time delay at the peak of the near-field signal. Then, a scanning detection is performed 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 black phosphorus. Next, the pump light energy density is adjusted so that plasmon propagation exists on the black phosphorus surface. In one embodiment, after injecting 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; under the condition of 0mJ / cm2 pump light (i.e., no pump light injection), the surface of the black phosphorus sample does not support plasmon propagation, which corresponds to the "off" state of the plasmon optical switch. This significant on / off ratio characteristic (ON / OFF ratio) confirms the effective manipulation of the propagation state of black phosphorus plasmons by optical regulation. When pump light is injected, the carrier concentration increases, and the plasmon frequency is modulated to match the detection light, thus forming propagation conditions; when there is no pump light, the carrier concentration is low and cannot support plasmon propagation in this frequency band, thus realizing the switching function.

[0050] In addition, the propagating plasmons in black phosphorus also exhibit excellent low-loss transmission characteristics, and their propagation distance exceeds 8μm. Through fringe fitting calculations, 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 the plasmon during the propagation process. The higher the Q value, the lower the loss. Traditional precious 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.

[0051] 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.

[0052] 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.

[0053] Figure 6 FIG. 6 is a flow chart showing an exemplary method 600 according to an exemplary embodiment of the present disclosure. Figure 6Method 600 may include: step 610, emitting pump light and probe light into a black phosphorus material; step 620, adjusting the time delay between the pump light and the probe light; step 630, monitoring the spectrum of the black phosphorus plasmon response; and step 640, establishing a quantitative mapping model between the time delay between the pump light and the probe light and the plasmon frequency. Method 600 may be performed using the aforementioned system and may include the method steps described in any of the aforementioned embodiments.

[0054] In some embodiments, Fourier transform spectroscopy can be used to monitor the transient spectrum of the plasmon response in black phosphorus in real time.

[0055] 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.

[0056] Figure 7 FIG. 7 is a flow chart showing an exemplary method 700 according to an exemplary embodiment of the present disclosure. Figure 7 Method 700 may include: step 710, emitting pump light and probe light into the black phosphorus material; step 720, adjusting the pump light power density; step 730, monitoring the spectrum of the black phosphorus plasmon response; and step 740, establishing a quantitative mapping model between pump light power density and plasmon frequency. Method 700 may be performed using the aforementioned system and may include the method steps described in any of the aforementioned embodiments.

[0057] 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, transmitting pump light and probe light to the black phosphorus material; step 820, adjusting the time delay between the pump light and the probe light and / or adjusting the pump light power density. Method 800 may be performed using the aforementioned system, and may include the method steps involved in any of the aforementioned embodiments.

[0058] 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.

[0059] Figure 9 FIG. 8 shows an example block diagram of a system 900 including a tunable optoelectronic device according to an exemplary embodiment of the present disclosure. Figure 9As shown, the system includes a tunable optoelectronic device 902, black phosphorus 904 located in the tunable optoelectronic device 902, a pump light source 910, and a probe light source 920. As a light source for activating the black phosphorus 904, the pump light source 910 can be located inside or outside the tunable optoelectronic device; similarly, the probe light source 920 can also be located inside or outside the tunable optoelectronic device. The tunable optoelectronic device 900 has an output 906, and the characteristics of the output 906 of the optoelectronic device are adjusted by adjusting the time delay between the pump light 912 and the probe light 922 irradiated on the black phosphorus and / or adjusting the power density of the pump light 912.

[0060] According to an exemplary embodiment of the present disclosure, a method for controlling the optical switching effect based on black phosphorus may include: emitting pump light and probe light into the black phosphorus material; adjusting and fixing the time delay between the pump light and the probe light; performing scanning detection at the edge of the black phosphorus to obtain the state of the black phosphorus surface; and adjusting the energy density of the pump light to allow plasmon propagation on the black phosphorus surface. This method may be performed using the aforementioned system and may include the method steps involved in the system of any of the aforementioned embodiments.

[0061] 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.

[0062] In some embodiments, the time delay between the pump light and the probe light can be adjusted and fixed to 0.2 picoseconds.

[0063] In some embodiments, the pump light may include a hundred-femtosecond pulsed pump light.

[0064] According to an exemplary embodiment of the present disclosure, a method for preparing a black phosphorus flake may include: placing a black phosphorus crystal in a glove box; using a mechanical exfoliation technique to directionally exfoliate the black phosphorus crystal to form a black phosphorus crystal flake; and transferring the black phosphorus crystal flake to the surface of a silicon substrate. This method may be performed using the aforementioned system and may include the method steps described in any of the aforementioned embodiments.

[0065] In some embodiments, the glove box may include a high purity nitrogen or inert gas glove box.

[0066] In some embodiments, rectangular black phosphorus crystal flakes can be obtained by directional exfoliation by controlling the cleavage direction.

[0067] In some embodiments, the thickness of the black phosphorus crystal flakes may be between 100 nm and 500 nm.

[0068] According to an exemplary embodiment of the present disclosure, a method for controlling an optical switch effect based on black phosphorus may include: emitting pump light with a specific energy density to black phosphorus to allow an optical signal to propagate through the black phosphorus; and shutting off the pump light to prevent the optical signal from propagating through the black phosphorus. In some embodiments, the pump light of a specific energy density may be a pump light that can cause plasmon propagation on the surface of black phosphorus. The method can be performed using the aforementioned system, and the method steps involved in any of the aforementioned embodiments may be included in the method. Those skilled in the art will understand that the two steps in the method are methods for adjusting the two states of the optical switch, and there is no strict sequential relationship.

[0069] According to an exemplary embodiment of the present disclosure, a system including a black phosphorus-based optical switch device may include: an optical switch device, black phosphorus located in the optical switch device, and a pump light source. As a light source for activating black phosphorus, the pump light source can be placed inside the optical switch device or outside it. The optical switch device has an on state and an off state. When pump light with a specific energy density is emitted to black phosphorus to allow an optical signal 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 from propagating through the black phosphorus, the optical switch device is in the off state. The pump light of a specific energy density can cause plasmon propagation on the surface of black phosphorus.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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 spectrum modulation method based on black phosphorus, comprising: launching pump light and probe light into black phosphorus; Adjust the time delay between pump light and probe light; Spectra monitoring the plasmon response of black phosphorus; Based on the time delay between the pump light and the probe light and the monitored spectrum of the black phosphorus plasmon response, a quantitative mapping model of the time delay between the pump light and the probe light and the plasmon frequency was established.

2. The spectrum modulation method according to claim 1, wherein: The spectrum for monitoring the black phosphorus plasmon response includes: Fourier transform spectroscopy is used to monitor the transient spectrum of the plasmon response in black phosphorus in real time.

3. The spectrum modulation method according to claim 1, wherein: The spectrum for monitoring the black phosphorus plasmon response includes: The time delay parameters are scanned, the time domain interference signals at different delay moments are synchronously collected and the normalized spectral characteristics are demodulated.

4. A spectrum modulation method based on black phosphorus, comprising: launching pump light and probe light into black phosphorus; Adjust the pump light power density; Spectra monitoring the plasmon response of black phosphorus; Based on the pump light power density and the monitored spectrum of black phosphorus plasmon response, a quantitative mapping model between pump light power density and plasmon frequency was established.

5. A black phosphorus-based spectral modulation system, comprising: A pump light source module, used for outputting pump light; A detection light source module, used for outputting detection light; Pump light delay module, used to adjust the delay of pump light; a near-field optical microscope module, configured to carry black phosphorus and couple the pump light and the probe light; Fourier transform spectroscopy module, used for real-time monitoring of the spectrum.

6. The spectrum modulation system according to claim 5, wherein: The black phosphorus is located on a gold substrate.

7. The spectrum modulation system according to claim 5 or 6, further comprising: Pump light collimation module, used to reduce the divergence of pump light; as well as The detection light collimation module is used to reduce the divergence of the detection light.

8. The spectrum modulation system according to claim 5 or 6, wherein: The detection light source module includes a first detection light source module, a second detection light source module and a difference frequency module; The difference frequency module performs nonlinear difference frequency processing on the lasers emitted by the first detection light source module and the second detection light source module to output mid-infrared detection light.

9. A spectrum modulation method based on black phosphorus, comprising: launching pump light and probe light into black phosphorus; The time delay between the pump light and the probe light and / or the power density of the pump light are adjusted to achieve modulation of the spectrum of the black phosphorus plasmon response.

10. A tunable optoelectronic device, comprising: Black phosphorus; The output characteristics of the optoelectronic device are adjusted by adjusting the time delay between the pump light and the detection light irradiating the black phosphorus and / or adjusting the power density of the pump light.

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