Femtosecond laser electron dynamic control phase change material cross-scale modulation device and method

Abstract

The application provides a femtosecond laser electron dynamic control phase change material cross-scale modulation device and method, and the device comprises a femtosecond laser, a first beam splitter, a frequency doubler, a fold mirror, a first ultrafast mirror, a second ultrafast mirror, a third ultrafast mirror, a fourth ultrafast mirror, a fifth ultrafast mirror, a sixth ultrafast mirror, a collinear optical parametric amplifier, a beam reducer, a time-domain shaping module and a descending light path; the femtosecond laser generates laser pulses, which are divided into pump light and probe light through the first beam splitter; the pump light is focused on the surface of a sample to be measured after processing; the probe light is focused on the surface of the sample to be measured after processing, and a collection signal is obtained. The application realizes the superposition of the functions of two types of devices, i.e. an ultrafast optical switch and an optical storage, and overcomes the difficulty in integrating optical and electrical devices with different response times in different scales due to different response principles. The application has important application value in the integration and miniaturization of optical and electrical devices.

Description

Technical Field

[0001] This invention relates to the field of ultrafast laser modulation technology, and more particularly to a transscale modulation device and method for phase change materials by femtosecond laser electronic dynamic control. Background Technology

[0002] Optoelectronic devices have varying response speed requirements in different application scenarios. Taking optical switches as an example, an optical switch is an optical device with one or more selectable transmission ports, whose function is to physically switch or logically operate optical signals in optical transmission lines or integrated optical circuits. With the trend towards device miniaturization and functional integration, next-generation optical switches need to cover response times ranging from microseconds to picoseconds and even femtoseconds to meet the needs of different applications. Currently, specific types of optical switches with specific response times are required for specific time-scale applications. However, the principles and implementation methods of different types of optical switches vary significantly, making the integration of devices with responses at different time scales a challenge.

[0003] Femtosecond lasers, due to their ultrafast and powerful characteristics, possess unique advantages in the instantaneous manipulation of material properties and the control of non-volatile steady-state phases. Their influence mechanisms on materials across multiple timescales enable the manipulation of optoelectronic device properties for applications at different timescales. Ge₂Sb₂Te₅ (GST), as a special semiconductor material, can exhibit volatile transient optical property changes resulting from dynamic carrier variations under the influence of low-energy femtosecond lasers. This volatile transient optical response can be applied to ultrafast optical switching devices. Simultaneously, under the influence of higher-energy femtosecond lasers, the internal lattice structure of the material can be altered, forming non-volatile reversible crystalline and amorphous states. The optical properties of these different phases differ significantly, making them suitable for use as optical storage devices. Therefore, this special material holds promise for achieving the integration of different functions through simultaneous volatile and non-volatile modulation using femtosecond lasers. Currently, the cross-scale control of phase change materials using femtosecond lasers is still in the stage of separately modulating steady-state and transient optical properties. Transient modulation alters transient optical properties by controlling the number of excited charge carriers through changes in laser energy parameters. This response typically occurs on the fs-ps timescale. However, changing the laser energy parameters simultaneously affects both the modulation time and depth of the material's optical properties, making stable control of the response time difficult. Steady-state modulation utilizes different laser parameters to regulate the reversible phase transition process of phase change materials. According to the literature "Sub-ten nanosecond phase cycling of high contrast GeSbTe-and AgInSbTe-films," A. Schropp et al. observed that the amorphization time of GST phase change materials is approximately 5 ns, and the recrystallization time is less than 10 ns, demonstrating that GST can achieve rapid reversible phase transition cycling on the nanosecond scale. However, currently, directly outputting laser pulses from femtosecond lasers makes it difficult to flexibly control the pulse interval and energy levels of different pulses, thus hindering the regulation of rapid reversible phase transitions in GST on the nanosecond scale. Furthermore, observing the entire process of cross-scale modulation is also currently difficult. Steady-state phase transition processes typically rely on offline observation methods such as Raman spectroscopy and XRD diffraction patterns to observe the steady-state properties of processed and modulated materials. This method cannot directly reveal the instantaneous dynamic processes and the response time of phase transitions during material phase transitions. Furthermore, the observation time range of transient modulation is very short, which severely limits the observation of phase transitions and transient optical property changes. Summary of the Invention

[0004] Therefore, it is necessary to provide a transscale modulation device and method for phase change materials with femtosecond laser electronic dynamic control to address the above-mentioned technical problems.

[0005] A femtosecond laser-electronically dynamically controlled phase change material cross-scale modulation device, characterized in that it comprises: a femtosecond laser, a first beam splitter, a frequency doubler, a plurality of folding mirrors, a plurality of first ultrafast mirrors, a plurality of second ultrafast mirrors, a plurality of third ultrafast mirrors, a plurality of fourth ultrafast mirrors, a plurality of fifth ultrafast mirrors, a plurality of sixth ultrafast mirrors, a collinear optical parametric amplifier, a beam shrinking module, a time-domain shaping module, and a down-path optical path;

[0006] The femtosecond laser generates laser pulses, which are split into pump light and probe light by the first beam splitter. The pump light enters the frequency doubler to generate processed pump light. The processed pump light passes through the folding mirror and the first ultrafast mirror to enter the time-domain shaping module for dual-pulse time-domain shaping to obtain sub-pulse pump light. The sub-pulse pump light passes through the second ultrafast mirror to enter the falling optical path and is focused on the surface of the sample to be tested.

[0007] The probe light passes through the third ultrafast reflector and enters the collinear optical parametric amplifier to obtain a tunable laser pulse. The tunable laser pulse passes through the beam shrinker to reduce the divergence angle and obtains an adjustable probe light. The adjustable probe light passes through the fourth, fifth, and sixth ultrafast reflectors and enters the descending optical path, focusing on the surface of the sample to be tested to obtain the acquired signal.

[0008] In one embodiment, it further includes: a shutter optical switch and a second beam splitter;

[0009] The shutter switch is located on the pump light propagation line behind the first beam splitter and is used to control the on / off state of the pump light.

[0010] The second beam splitter is positioned after the shutter light switch to split the pump light into two beams. One of the pump light beams enters the frequency multiplier, while the other pump light beam and the processing probe light are combined with a folding mirror to generate time-domain processing light. The time-domain processing light then enters the time-domain shaping module through the first ultrafast mirror.

[0011] In one embodiment, it further includes: a first climbing optical path;

[0012] The first climbing optical path is located behind the first ultrafast reflector and is used to propagate the time-domain processing light into the time-domain shaping module.

[0013] In one embodiment, it further includes: a long-delay displacement stage;

[0014] The long-delay displacement stage is positioned behind the fourth ultrafast reflector, and the fifth ultrafast reflector is mounted on the long-delay displacement stage; the long-delay displacement stage is used to adjust the distance between the fourth and fifth ultrafast reflectors to extend the optical path of the probe light.

[0015] In one embodiment, it further includes: a second climbing optical path;

[0016] The second climbing optical path is set behind the long-delay displacement stage and is used to extend the optical path of the adjustment probe light.

[0017] In one embodiment, the time-domain shaping module includes: a first attenuator, a third beam splitter, two second attenuators, two mirrors, and a dual-pulse delay stage;

[0018] The first attenuator is installed after the first climbing optical path to adjust the energy of the time-domain processing light and obtain the entering time-domain pulse;

[0019] The third beam splitter is positioned after the first attenuator and along the propagation path of the time-domain pulse, and is used to split the incoming time-domain pulse into two sub-time-domain pulses.

[0020] The second attenuator is disposed on one side of the third beam splitter, on the propagation path of the sub-time domain pulse, and is used to adjust the energy of the sub-time domain pulse to obtain the processed sub-pulse;

[0021] The reflector is positioned behind the second attenuator and along the propagation path of the processed sub-pulse. The reflector is used to reflect the processed sub-pulse to the third beam splitter, which outputs the sub-pulse pump light. Either reflector is positioned on the dual-pulse delay stage, and the dual-pulse delay stage adjusts the distance between the reflector and the second attenuator.

[0022] In one embodiment, the descending optical path includes: a camera, several broadband beam splitters, and an objective lens;

[0023] The camera is positioned at the top of the descending optical path, the broadband beam splitter is positioned at the bottom of the camera, the objective lens is positioned at the bottom of the broadband beam splitter, and the sample to be tested is positioned at the top.

[0024] The sub-pulse pump light is focused onto the surface of the sample under test by the wide-band beam splitter and the objective lens. The adjustment probe light is also focused onto the surface of the sample under test by the wide-band beam splitter and the objective lens, resulting in reflected light. The reflected light is then collected by the camera to obtain a collection signal.

[0025] In one embodiment, it further includes: a control computer;

[0026] The control computer is communicatively connected to the femtosecond laser, the collinear optical parametric amplifier, the long-delay displacement stage, the time-domain shaping module, and the descent optical path, and is used to send control signals, process and store the acquired signals.

[0027] Based on the same inventive concept, this application also provides a femtosecond laser electronic dynamic control phase change material cross-scale modulation method, which is applied to a femtosecond laser electronic dynamic control phase change material cross-scale modulation device.

[0028] The method includes:

[0029] Adjust the frequency multiplier to select the frequency multiplication mode and set the pump light wavelength; adjust the collinear optical parametric amplifier and set the probe light wavelength;

[0030] Adjust the long-delay displacement stage and set the observation zero point; adjust the double-pulse delay stage and set the double-pulse delay zero point;

[0031] The position of the reflector on the dual-pulse delay stage is adjusted, and the femtosecond laser is set to generate laser pulses. The pump light passes through a shutter optical switch, a second beam splitter, a frequency doubler, a folding reflector, a first ultrafast reflector, a first ascending optical path, a time-domain shaping module, and a second ultrafast reflector before entering the descending optical path and focusing on the surface of the sample under test. The probe light passes through a third ultrafast reflector, a collinear optical parametric amplifier, a beam reducer, a fourth ultrafast reflector, a fifth ultrafast reflector, a second ascending optical path, and a sixth ultrafast reflector before entering the descending optical path and focusing on the surface of the sample under test. The camera collects the reflectivity signal for observation, completing the modulation of transient optical properties and obtaining the first acquisition signal.

[0032] The second attenuator is adjusted to regulate the energy of the sub-time domain pulses, ensuring that the energies of the two sub-time domain pulses satisfy the single-pulse energy ranges for crystallization and amorphization, respectively. The position of the reflector on the dual-pulse delay stage is adjusted. The femtosecond laser is set to generate laser pulses. The pump light passes through a shutter optical switch, a second beam splitter, a frequency doubler, a folding reflector, a first ultrafast reflector, a first ascending optical path, a time-domain shaping module, and a second ultrafast reflector before entering the descending optical path and focusing on the surface of the sample under test. The probe light passes through a third ultrafast reflector, a collinear optical parametric amplifier, a beam reducer, a fourth ultrafast reflector, a fifth ultrafast reflector, a second ascending optical path, and a sixth ultrafast reflector before entering the descending optical path and focusing on the surface of the sample under test. The camera collects the reflectivity signal for observation, completing the modulation of the steady-state rapid phase transition and obtaining the second acquisition signal.

[0033] The first and second acquisition signals are sent to the control computer, which then performs cross-scale modulation and observation of the transient optical property change response time and steady-state rapid phase transition of the sample under test.

[0034] Compared to existing technologies, the advantages and beneficial effects of this invention are as follows: This invention achieves transient response time control and steady-state rapid phase transition by adjusting the dual-pulse delay and energy parameters of each laser pulse through time-domain shaping of femtosecond lasers. The changes in transient optical properties over time and the steady-state phase transition process are observed using pump-probe auxiliary methods. It realizes the control of optical properties of GST phase transition materials across two time scales—volatile transient (picosecond scale) and non-volatile steady-state (nanosecond scale)—using a single tool—the femtosecond laser. This achieves the superposition of ultrafast optical switching with the functions of optical storage devices, overcoming the difficulty of integrating optoelectronic devices with different response times at different scales due to their different response principles. It has significant application value in the integration and miniaturization of optoelectronic devices. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the optical path propagation of a femtosecond laser-electronically dynamically modulated phase change material transscale modulation device in one embodiment.

[0036] Figure 2 This is a schematic diagram of a specific implementation structure of a femtosecond laser-electronically dynamically controlled phase change material transscale modulation device in one embodiment.

[0037] Figure 3 This is a schematic diagram of the modulation process of a femtosecond laser transscale modulation phase change material in one embodiment.

[0038] In the diagram, 1-femtosecond laser, 2-first beam splitter, 3-shutter optical switch, 4-second beam splitter, 5-frequency doubler, 6, 6' and 6”-several folding mirrors, 7-first ultrafast mirror, 8-first climbing optical path, 9-time domain shaping module, 10-second ultrafast mirror, 11-falling optical path, 12-third ultrafast mirror, 13-collinear optical parametric amplifier, 14-beam shrinking, 15 and 15'-fourth ultrafast mirror. 16 and 16' - Fifth ultrafast mirror, 17 - Long delay shift stage, 18 - Second climbing optical path, 19 and 19' - Sixth ultrafast mirror, 20 - Control computer, 90 - First attenuator, 91 - Third beam splitter, 92 and 92' - Second attenuator, 93 and 93' - Mirror, 94 - Double pulse delay stage, 110 - Camera, 111, 111', 111” and 111”' - Broadband beam splitter, 112 - Objective lens. Detailed Implementation

[0039] Before describing the specific embodiments of the present invention, the overall concept of the present invention will be explained as follows:

[0040] This invention primarily focuses on the development of ultrafast laser modulation processes. Currently, it is difficult to flexibly control the pulse interval and energy levels of different pulses by directly outputting laser pulses from femtosecond lasers, making it impossible to achieve rapid and reversible phase transition control at the nanosecond scale of GST. Furthermore, observing the entire modulation process across scales is also challenging.

[0041] Therefore, this invention proposes a femtosecond laser-based electronically dynamically controlled cross-scale modulation device and method for phase change materials. By utilizing a femtosecond laser time-domain shaping method combined with pump-probe technology, it achieves adjustable response time of transient optical property changes in phase change materials and cross-scale modulation method and modulation response time observation of steady-state rapid phase transitions. This solves the problem of how to achieve cross-scale control of optoelectronic devices using the same tool, and meets the functional integration needs of optoelectronic devices in different application scenarios.

[0042] After introducing the overall concept of the present invention, in order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0043] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of this specification should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in one or more embodiments of this specification do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word covers the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0044] In one embodiment, such as Figure 1As shown, a femtosecond laser-based electronically dynamically modulated phase change material cross-scale modulation device is provided, comprising: a femtosecond laser 1, a first beam splitter 2, a shutter optical switch 3, a second beam splitter 4, a frequency doubler 5, several folding mirrors 6, several first ultrafast mirrors 7, a first ascending optical path 8, a time-domain shaping module 9, several second ultrafast mirrors 10, a descending optical path 11, several third ultrafast mirrors 12, a collinear optical parametric amplifier 13, a beam reducer 14, several fourth ultrafast mirrors 15, several fifth ultrafast mirrors 16, a long-delay shifting stage 17, a second ascending optical path 18, several sixth ultrafast mirrors 19, and a control computer 20. The folding mirrors 6, 7, 10, 12, 15, 16, and 19 are required to complete the necessary optical path transmission, and there is no limit to the number of each. In this invention, the sample to be tested is GST sputtered onto a sapphire substrate by magnetron sputtering.

[0045] A femtosecond laser 1 generates laser pulses, which are split into pump light and probe light by a first beam splitter 2. The pump light passes through a shutter switch 3, which controls the on / off state of the pump light. When the shutter switch 3 is open, the pump light enters a second beam splitter 4, which splits the pump light into two beams. One of the pump light beams enters a frequency multiplier 5 to generate a processing pump light. The other pump light and the processing pump light pass through a folding mirror 6 to generate a time-domain processing light. The time-domain processing light passes through a first ultrafast mirror 7 and enters a first ascending optical path 8. The first ascending optical path 8 is located after the first ultrafast mirror 7 and propagates the time-domain processing light into a time-domain shaping module 9 for dual-pulse time-domain shaping to obtain a sub-pulse pump light. The sub-pulse pump light passes through a second ultrafast mirror 10 and enters a descending optical path 11, which is focused onto the surface of the sample to be tested.

[0046] The probe light passes through the third ultrafast reflector 12 and enters the collinear optical parametric amplifier 13 to obtain a tunable laser pulse. The tunable laser pulse passes through the beam shrinker 14 to reduce the divergence angle and obtain the adjustable probe light. The adjustable probe light passes through the fourth ultrafast reflector 15, the fifth ultrafast reflector 16, the second ascending optical path 18, and the sixth ultrafast reflector 19 to enter the descending optical path 11 and is focused on the surface of the sample to be tested to obtain the reflected light, thereby acquiring the acquisition signal.

[0047] The long-delay displacement stage 17 is set behind the fourth ultrafast reflector 15, and the fifth ultrafast reflector 16 is installed on the long-delay displacement stage 17. The long-delay displacement stage 17 is used to adjust the distance between the fourth ultrafast reflector 15 and the fifth ultrafast reflector 16 to extend the optical path of the probe light.

[0048] The control computer 20 is connected to the femtosecond laser 1, collinear optical parametric amplifier 13, long-delay displacement stage 17, time-domain shaping module 9 and falling optical path 11 for communication, and is used to send control signals, process and store the acquired signals.

[0049] The time-domain shaping module 9 includes: a first attenuator 90, a third beam splitter 91, two second attenuators 92 and 92', two reflectors 93' and 93, and a dual-pulse delay stage 94;

[0050] The first attenuator 90 is installed after the first climbing optical path 8 to adjust the energy of the time-domain processing light and obtain the entering time-domain pulse;

[0051] The third beam splitter 91 is positioned after the first attenuator 90 on the time-domain pulse propagation path, and is used to split the incoming time-domain pulse into two sub-time-domain pulses.

[0052] The second attenuators 92 and 92' are disposed on one side of the third beam splitter 91, on the sub-time domain pulse propagation path, and are used to adjust the energy of the sub-time domain pulse to obtain the processed sub-pulse.

[0053] Reflectors 93 and 93' are positioned behind the second attenuators 92 and 92' on the path of the processed sub-pulse propagation. Reflectors 93' and 93' are used to reflect the processed sub-pulse to the third beam splitter 91, from which the sub-pulse pump light is output. Any one of the reflectors 93' is positioned on the dual-pulse delay stage 94, and the dual-pulse delay stage 94 adjusts the distance between any one of the reflectors 93' and the second attenuator 92'.

[0054] The descending optical path 11 includes: a camera 110, several wideband beam splitters 111 and an objective lens 112;

[0055] Camera 110 is positioned at the top of the descending optical path 11, wideband beam splitter 111 is positioned at the bottom of camera 110, and objective lens 112 is positioned at the bottom of wideband beam splitter 111 and the top of the sample to be tested.

[0056] The sub-pulse pump light is focused onto the surface of the sample under test by a wide-band beam splitter 111 and an objective lens 112. The probe light is adjusted and focused onto the surface of the sample under test by the wide-band beam splitter 111 and an objective lens 112 to obtain reflected light. The reflected light is collected by a camera 112 to obtain a collection signal.

[0057] This invention provides a femtosecond laser-based electronically dynamically modulated phase-change material (GST) trans-scale modulation device. By adjusting the time-domain delay of the dual-pulse and the energy parameters of each laser pulse through time-domain shaping of the femtosecond laser, it achieves transient response time control and steady-state rapid phase transition. Pump-probe assistance is used to observe the changes in transient optical properties over time and the steady-state phase transition process. This invention enables the manipulation of the optical properties of GST across two time scales—volatile transient (picosecond scale) and non-volatile steady-state (nanosecond scale)—using a single tool—the femtosecond laser. It achieves the superposition of ultrafast optical switching with the functions of both optical and optical storage devices, overcoming the challenge of integrating optoelectronic devices with different response times at different scales due to their different response principles. This invention has significant application value in the integration and miniaturization of optoelectronic devices.

[0058] Based on the same inventive concept, the present invention also provides a femtosecond laser electronically dynamically controlled phase change material cross-scale modulation method, which is applied to the femtosecond laser electronically dynamically controlled phase change material cross-scale modulation device described above.

[0059] Methods, including:

[0060] Adjust the frequency multiplier 5 to select the frequency multiplication mode and set the pump light wavelength; adjust the collinear optical parametric amplifier 13 and set the probe light wavelength;

[0061] Adjust the long-delay displacement stage 17 and set the observation zero point; adjust the double-pulse delay stage 94 and set the double-pulse delay zero point;

[0062] The position of the mirror 93' on the dual-pulse delay stage 94 is adjusted, and the femtosecond laser 1 is set to generate laser pulses. The pump light passes through the shutter switch 3, the second beam splitter 4, the frequency doubler 5, the folding mirror 6, the first ultrafast mirror 7, the first ascending optical path 8, the time-domain shaping module 9, and the second ultrafast mirror 10, and enters the descending optical path 11, which is focused on the surface of the sample to be tested. The probe light passes through the third ultrafast mirror 12, the collinear optical parametric amplifier 13, the beam shrinker 14, the fourth ultrafast mirror 15, the fifth ultrafast mirror 16, the second ascending optical path 18, and the sixth ultrafast mirror 19, and enters the descending optical path 11, which is focused on the surface of the sample to be tested. The camera 110 collects the reflectivity signal for observation, completes the modulation of transient optical properties, and obtains the first acquisition signal.

[0063] Adjust the second attenuators 92 and 92' to adjust the energy of the sub-time domain pulses so that the energies of the two sub-time domain pulses meet the single-pulse energy ranges of crystallization and amorphization, respectively; adjust the position of the mirror 93' on the dual-pulse delay stage 94; set the femtosecond laser 1 to generate laser pulses, and the pump light enters the descending optical path 11 through the shutter optical switch 3, the second beam splitter 4, the frequency doubler 5, the folding mirror 6, the first ultrafast mirror 7, the first ascending optical path 8, the time-domain shaping module 9, and the second ultrafast mirror 10, focusing on the surface of the sample to be tested; the probe light enters the descending optical path 11 through the third ultrafast mirror 12, the collinear optical parametric amplifier 13, the beam shrinker 14, the fourth ultrafast mirror 15, the fifth ultrafast mirror 16, the second ascending optical path 18, and the sixth ultrafast mirror 19, focusing on the surface of the sample to be tested, and the camera 110 collects the reflectivity signal for observation, completing the modulation of the steady-state rapid phase transition and obtaining the second acquisition signal.

[0064] The first and second acquisition signals are sent to the control computer 20, which then performs adjustable response time of transient optical property changes and cross-scale modulation and observation of steady-state rapid phase transitions of the sample under test.

[0065] This invention provides a cross-scale modulation method for phase change materials based on femtosecond laser electronic dynamic control. By using a femtosecond laser time-domain shaping method combined with pump-probe technology, it achieves adjustable response time of transient optical property changes in phase change materials and cross-scale modulation method and modulation response time observation of steady-state rapid phase transitions. The purpose is to solve the problem of how to achieve cross-scale control of optoelectronic devices using the same tool, and meet the different functional integration requirements of optoelectronic devices in different application scenarios.

[0066] This invention utilizes the principle of femtosecond laser electronic dynamic control to achieve cross-scale dynamic control of phase change materials. Because the femtosecond laser pulse width is extremely short (as short as 10⁻⁶),... -15 s), which is comparable to the time scale of electronic state changes, after the material is irradiated by a femtosecond laser pulse, all subsequent processing and control processes (10 -10 ~10 -3Both s) are determined by the interaction between femtosecond lasers and electrons. Therefore, the interaction between femtosecond lasers and electrons can be dynamically controlled through time-domain shaping, thereby achieving cross-scale modulation. Specifically: For the modulation of ultrafast transient processes, when the energy of a single femtosecond laser pulse is less than the modification threshold, the electron density increases on the transient timescale and spontaneously returns to its initial state after tens of picoseconds. If, before the free electrons excited by the first pulse have recombinated, a second pulse is irradiated to excite new free electrons through time-domain shaping of the femtosecond laser, the decreasing free electron density will rise again, thereby prolonging the response time of the transient optical property change and thus achieving free control of the response time of the ultrafast optical switch. For the fast reversible modulation of steady-state phase transitions, when the energy of a single femtosecond laser pulse is higher than the modification threshold, the material phase state will complete the phase transition in a few nanoseconds. At this time, by using time-domain shaping of the femtosecond laser to apply the second pulse immediately after the modification of the first pulse and adjusting the energy of the second pulse, fast reversible control of the steady-state phase state can be achieved. By adjusting the delay and energy of the two pulses, it is possible to simultaneously control the response time of ultrafast transient optical properties and the steady-state rapid reversible phase transition.

[0067] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0068] Example 1

[0069] like Figure 2 As shown, taking as an example a structure consisting of three folding mirrors 6, 6' and 6”, one first ultrafast mirror 7, one second ultrafast mirror 10, one third ultrafast mirror 12, two fourth ultrafast mirrors 15 and 15', two fifth ultrafast mirrors 16 and 16', two sixth ultrafast mirrors 19 and 19', and four broadband beam splitters 111, 111', 111”, and 111”’, the transscale modulation device for phase change materials with femtosecond laser electronic dynamic control is explained.

[0070] A femtosecond laser 1 generates laser pulses, which are split by a first beam splitter 2 into pump light for cross-scale modulation of the sample under test and probe light for observation. The pump light is controlled by a shutter switch 3 and then passes through a second beam splitter 4 into a refracting mirror 6” and a frequency doubler 5. The frequency doubler 5 can selectively output processed pump light with wavelengths of 515nm and 343nm. Depending on the selected 515 / 343 / 1030nm wavelength pump light and processed pump light, the refracting mirrors 6, 6', and 6” can be opened to introduce the pump light and processed pump light into the first ultrafast mirror 7 and into the pump light path. Then, the time-domain processed light passes through a first ascending optical path 8 and enters the time-domain shaping module 9 for dual-pulse time-domain shaping, outputting two delay-adjustable sub-pulse pump lights. These lights pass through a second ultrafast mirror 10 and enter the descending optical path 11, where a wide-band beam splitter 111 enters downwards and enters the objective lens 112, focusing onto the surface of the sample under test to complete the cross-scale modulation of the sample. The probe light enters the collinear optical parametric amplifier 13 after passing through the third ultrafast reflector 12, outputting a tunable laser pulse with a wavelength of 300-2000 nm. This tunable laser pulse then passes through the beam shrinker 14 to reduce its divergence angle, resulting in a modulated probe light. The modulated probe light then passes through the fourth ultrafast reflectors 15 and 15' and enters the fifth ultrafast reflectors 16 and 16' on the long-delay displacement stage 17. The long-delay displacement stage 17 moves the fifth ultrafast reflectors 16 and 16', thereby adjusting the delay of the modulated probe light. Finally, the modulated probe light passes through the... The second ascending optical path 18, the sixth ultrafast reflecting mirror 19, 19' guides the light into the descending optical path 13. The wideband beam splitter 111' combines with the sub-pulse pump light and then passes downward through the wideband beam splitter 111”' to combine with the illumination white light emitted by the illumination source. The light then enters the objective lens 112 and is focused on the surface of the sample to be tested for detection. The information from the surface of the sample is reflected and reaches the CCD camera 14 above the wideband beam splitter 111 or the information acquisition fiber above the wideband beam splitter 111”, thus obtaining the acquired image or signal.

[0071] The time-domain shaping module 9 shapes a time-domain processed light beam into two time-delayed processed sub-pulses using a Michelson interferometer structure. Specifically, after the energy of the time-domain processed light beam is adjusted by the first attenuator 90, it is split into two processed sub-pulses by the third beam splitter 91. These sub-pulses then reach the reflectors 93 and 93' of the two arms of the Michelson interferometer and return to the third beam splitter 91 for beam combining and output to the second ultrafast reflector 10. The reflector 93' of one arm is mounted on the dual-pulse delay stage 94. The delay of the dual processed sub-pulses is changed by altering the optical path difference between the two arms through the dual-pulse delay stage 94. For example, with an optical path of 60 cm, the delay of the dual processed sub-pulses can reach 2 ns. By adjusting the second attenuators 92 and 92', the energy of each processed sub-pulse is changed, ultimately becoming a femtosecond laser dual pulse modulated across scales for the sample under test. The femtosecond laser 1, shutter switch 3, collinear optical parametric amplifier 13, long-delay displacement stage 17, double-pulse delay stage 94, and displacement stage carrying the sample under test in the optical path are centrally controlled by the control computer 20. At the same time, the first acquisition signal and the second acquisition signal are also centrally processed by the control computer 20.

[0072] Example 2

[0073] The parameters of the femtosecond laser 1 used in the experiment are as follows: center wavelength of femtosecond laser 1 is 1030 nm, pulse width is 290 ps, ​​and repetition rate is 1-1 MHz. The sample under test is a 50 nm thick GST deposited on a sapphire substrate by magnetron sputtering. The pump light wavelength used in the experiment is 1030 nm, and the probe light wavelength is 600 nm.

[0074] Taking a structure consisting of three folding mirrors 6, 6' and 6”, one first ultrafast mirror 7, one second ultrafast mirror 10, one third ultrafast mirror 12, two fourth ultrafast mirrors 15 and 15', two fifth ultrafast mirrors 16 and 16', two sixth ultrafast mirrors 19 and 19', and four broadband beam splitters 111, 111', 111”, and 111”’ as an example, this paper describes the cross-scale modulation method of phase change materials by femtosecond laser electronic dynamic control.

[0075] A schematic diagram of the cross-scale modulation process of a 50nm thick GST sample, initially in a crystalline state, deposited on a sapphire substrate, is shown below. Figure 3 The specific steps are as follows:

[0076] Step S101: Adjust the optical path, set the pump light wavelength to 1030nm and the probe light wavelength to 600nm; adjust the optical path of the double pulse delay stage 94, and set the zero point of the time-domain shaped double pulse delay; adjust the long delay displacement stage 17, and set the zero point of the pump light and probe light delay.

[0077] Step S102: Adjust the position of the mirror 93' on the dual-pulse delay stage to block the mirror 93' of one arm of the Michelson interferometer structure in the time-domain shaping module 9. Adjust the first attenuation sheet 90 to adjust the energy E1 of the processing sub-pulse 1 for transient response modulation. Focus the probe light on the surface of the待测 sample, and the camera collects the reflectivity signal of the surface of the待测 sample in response to obtain the duration τ1 of the change in transient modulation reflectivity.

[0078] Step S103: Adjust the position of the mirror 93' on the dual-pulse delay stage to remove the block in the time-domain shaping module 9, and adjust the delay Δt of the processing sub-pulses 2 and 3. 1， Perform dual-pulse modulation of the transient response time. Focus the probe light on the surface of the待测 sample, and the camera 110 collects the reflectivity signal of the surface of the待测 sample in response to obtain the duration τ2 + Δt1 of the change in transient modulation reflectivity.

[0079] Adjust the second attenuation sheets 92 and 92' to adjust the energy of the processing sub-pulse 4 to E2, the energy of the processing sub-pulse 5 to E3, and the delay Δt2 between the processing sub-pulse 4 and the processing sub-pulse 5 for dual-pulse modulation of the steady-state response rapid phase change. Focus the probe light with a delay of τ3 from the pump light on the surface of the待测 sample, and the camera 110 collects the reflectivity signal of the surface of the待测 sample in response to observe the phase change process.

[0080] In the above step description, the energy E1 < E c < E2 < E a < E3, where E c is the crystallization single-pulse energy threshold, and E c is the amorphous single-pulse energy threshold; τ1, τ2, and τ3 are the delays between the pump light and the probe light; Δt1 is the dual-processing sub-pulse of transient modulation, and Δt2 is the dual-processing sub-pulse of steady-state modulation.

[0081] In the above modulation steps, the schematic diagram of the change in the optical properties of the phase change material collected by the probe light is as Figure 2 : Under the 600nm probe light, when the transient reflectivity increases under the action of the processing sub-pulse 1 and returns to the initial state after τ1; when the transient reflectivity increases under the action of the processing sub-pulses 2 and 3, the time for the reflectivity to return to the initial state is extended from τ1 to τ2 + Δt 1， When the processing sub-pulse 4 acts on the crystalline GST, the phase state of GST changes to amorphous within Δt2, and the reflectivity decreases; when the time-domain pulse 5 acts within Δt2, the amorphous GST is re-transformed into the crystalline state.

[0082] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of the invention as described above, which are not provided in the details for the sake of brevity.

[0083] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0084] Although the invention has been described in conjunction with specific embodiments thereof, many substitutions, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description.

[0085] The embodiments of this invention are intended to cover all such substitutions, modifications, and variations falling within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this invention should be included within the protection scope of this invention.

Claims

1. A femtosecond laser-electronically dynamically controlled phase change material transscale modulation device, characterized in that, include: The system comprises a femtosecond laser, a first beam splitter, a frequency doubler, several folding mirrors, several first ultrafast mirrors, several second ultrafast mirrors, several third ultrafast mirrors, several fourth ultrafast mirrors, several fifth ultrafast mirrors, several sixth ultrafast mirrors, a collinear optical parametric amplifier, a beam reducer, a time-domain shaping module, a falling optical path, an optical switch, a second beam splitter, a long-delay shift stage, and a control computer; wherein the time-domain shaping module includes: a first attenuator, a third beam splitter, two second attenuators, two mirrors, and a dual-pulse delay stage; The femtosecond laser generates laser pulses, which are split into pump light and probe light by the first beam splitter. An optical switch is positioned on the pump light propagation line after the first beam splitter to control the on / off state of the pump light. A second beam splitter is positioned after the optical switch to split the pump light into two beams. One of these beams enters the frequency doubler to generate a processing pump light. The other beam and the processing pump light pass through a folding mirror to generate a time-domain processing light. This time-domain processing light passes through the first ultrafast mirror and enters a time-domain shaping module for dual-pulse time-domain shaping to obtain a sub-pulse pump light. The sub-pulse pump light passes through the second ultrafast mirror and enters the falling light path, where it is focused onto the surface of the sample under test. The probe light passes through the third ultrafast reflector and enters the collinear optical parametric amplifier to obtain a tunable laser pulse. The tunable laser pulse passes through the beam shrinker to reduce the divergence angle and obtains an adjustable probe light. The adjustable probe light passes through the fourth, fifth, and sixth ultrafast reflectors and enters the descending optical path, focusing on the surface of the sample to be tested to obtain the acquired signal.

2. The femtosecond laser electronically dynamically controlled phase change material cross-scale modulation device according to claim 1, characterized in that, Also includes: First climbing path; The first climbing optical path is located behind the first ultrafast reflector and is used to propagate the time-domain processing light into the time-domain shaping module.

3. The femtosecond laser electronically dynamically controlled phase change material cross-scale modulation device according to claim 1, characterized in that, The long-delay displacement stage is positioned behind the fourth ultrafast reflector, and the fifth ultrafast reflector is mounted on the long-delay displacement stage; the long-delay displacement stage is used to adjust the distance between the fourth and fifth ultrafast reflectors to extend the optical path of the probe light.

4. The femtosecond laser electronically dynamically controlled phase change material cross-scale modulation device according to claim 3, characterized in that, Also includes: Second climbing optical path; The second climbing optical path is set behind the long-delay displacement stage and is used to extend the optical path of the adjustment probe light.

5. The femtosecond laser electronically dynamically controlled phase change material cross-scale modulation device according to claim 2, characterized in that, The first attenuator is installed after the first climbing optical path to adjust the energy of the time-domain processing light and obtain the entering time-domain pulse; The third beam splitter is positioned after the first attenuator and on the propagation path of the incoming time-domain pulse, and is used to split the incoming time-domain pulse into two sub-time-domain pulses. The second attenuator is disposed on one side of the third beam splitter, on the propagation path of the sub-time domain pulse, and is used to adjust the energy of the sub-time domain pulse to obtain the processed sub-pulse; The reflector is positioned behind the second attenuator and along the propagation path of the processed sub-pulse. The reflector is used to reflect the processed sub-pulse to the third beam splitter, which outputs the sub-pulse pump light. Either reflector is positioned on the dual-pulse delay stage, and the dual-pulse delay stage adjusts the distance between the reflector and the second attenuator.

6. The femtosecond laser electronically dynamically modulated phase change material cross-scale modulation device according to claim 1, characterized in that, The descending optical path includes: a camera, several wideband beam splitters, and objective lenses; The camera is positioned at the top of the descending optical path, the broadband beam splitter is positioned at the bottom of the camera, the objective lens is positioned at the bottom of the broadband beam splitter, and the sample to be tested is positioned at the top. The sub-pulse pump light is focused onto the surface of the sample under test by the wide-band beam splitter and the objective lens. The adjustment probe light is also focused onto the surface of the sample under test by the wide-band beam splitter and the objective lens, resulting in reflected light. The reflected light is then collected by the camera to obtain a collection signal.

7. The femtosecond laser electronically dynamically controlled phase change material cross-scale modulation device according to claim 3, characterized in that, The control computer is communicatively connected to the femtosecond laser, the collinear optical parametric amplifier, the long-delay displacement stage, the time-domain shaping module, and the descent optical path, and is used to send control signals, process and store the acquired signals.

8. A method for cross-scale modulation of phase change materials by femtosecond laser electronic dynamic control, characterized in that, Applications include femtosecond laser electronic dynamic control phase change material cross-scale modulation devices according to claims 1-7; The method includes: Adjust the frequency multiplier to select the frequency multiplication mode and set the pump light wavelength; adjust the collinear optical parametric amplifier and set the probe light wavelength; Adjust the long-delay displacement stage and set the observation zero point; adjust the double-pulse delay stage and set the double-pulse delay zero point; The position of the reflector on the dual-pulse delay stage is adjusted, and the femtosecond laser is set to generate laser pulses. The pump light passes through an optical switch, a second beam splitter, a frequency doubler, a folding reflector, a first ultrafast reflector, a first ascending optical path, a time-domain shaping module, and a second ultrafast reflector before entering the descending optical path and being focused on the surface of the sample under test. The probe light passes through a third ultrafast reflector, a collinear optical parametric amplifier, a beam reducer, a fourth ultrafast reflector, a fifth ultrafast reflector, a second ascending optical path, and a sixth ultrafast reflector before entering the descending optical path and being focused on the surface of the sample under test. The camera collects the reflectivity signal for observation, completing the modulation of transient optical properties and obtaining the first acquisition signal. The second attenuator is adjusted to regulate the energy of the sub-time domain pulses, ensuring that the energies of the two sub-time domain pulses satisfy the single-pulse energy ranges for crystallization and amorphization, respectively. The position of the reflector on the dual-pulse delay stage is adjusted. The femtosecond laser is set to generate laser pulses. The pump light passes through an optical switch, a second beam splitter, a frequency doubler, a folding reflector, a first ultrafast reflector, a first ascending optical path, a time-domain shaping module, and a second ultrafast reflector before entering the descending optical path and focusing on the surface of the sample under test. The probe light passes through a third ultrafast reflector, a collinear optical parametric amplifier, a beam reducer, a fourth ultrafast reflector, a fifth ultrafast reflector, a second ascending optical path, and a sixth ultrafast reflector before entering the descending optical path and focusing on the surface of the sample under test. The camera collects the reflectivity signal for observation, completing the modulation of the steady-state rapid phase transition and obtaining the second acquisition signal. The first and second acquisition signals are sent to the control computer, which performs cross-scale modulation and observation of the transient optical property change response time and steady-state rapid phase transition of the sample under test.

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