Method for analyzing coupling relation between optical phonons and carriers based on transient observation technology

Abstract

The invention relates to the technical field of ultrafast detection, in particular to a method for analyzing the coupling relation between optical phonons and carriers based on a transient observation technology. According to the specific technical scheme, the method comprises the following steps: (1) testing few-layer two-dimensional transition metal selenide by using super-continuous white light transmission type pumping detection to obtain wide-spectrum transient absorption data; (2) extracting dynamic curves at different detection wavelengths from the wide-spectrum transient absorption data; (3) performing deconvolution three-exponential fitting on dynamics at different detection wavelengths, and subtracting fitting data from original data to extract coherent optical phonon oscillation signals; (4) performing periodic damped oscillation fitting on the coherent optical phonon oscillation signal to extract coherent optical phonon frequency and amplitude; and (5) making a detection wavelength dependency graph for the coherent optical phonon amplitudes of the same frequency. According to the invention, the coupling strength of optical phonons with different frequencies and carriers with different energy levels is obtained through analysis of optical phonon amplitude detection wavelength dependence.

Description

Technical Field

[0001] The present invention relates to the field of ultrafast detection technology, and specifically relates to a method for analyzing the coupling relationship between optical phonons and carriers based on transient observation technology. Background Art

[0002] Two-dimensional transition metal selenides generally have good stability, optoelectronic and mechanical properties. For example, palladium diselenide and platinum diselenide have been proven to have multiple coherent phonons inside the materials. The coupling relationship between carriers and phonons makes them have great potential in the application of optoelectronic devices such as high-frequency communication and ultrafast topological switches, and has attracted wide attention from scientists in recent years. In traditional technologies, the coupling between coherent phonons and carriers in materials cannot be directly observed, resulting in extremely poor understanding of the complex transient coupling processes of light, sound, electricity, and force in two-dimensional transition metal selenides, which severely limits the development of optoelectronic devices based on two-dimensional transition metal selenides. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a method for analyzing the coupling relationship between optical phonons and carriers based on transient observation technology.

[0004] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0005] The present invention discloses a method for analyzing the coupling relationship between optical phonons and carriers based on transient observation technology, including the following steps:

[0006] (1) Grow or transfer a few-layer two-dimensional selenide sample on a substrate; the substrate is made of transparent silica, so that the transmission pump-probe experiment in step (2) can be carried out.

[0007] (2) Use supercontinuum white light transmission pump-probe to test the few-layer two-dimensional transition metal selenide to obtain broadband transient absorption data; among them, the detection range of the supercontinuum white light is 380 - 800 nm.

[0008] (3) Extract the kinetic curves at different detection wavelengths from the broadband transient absorption data, and the kinetics at different detection wavelengths correspond to the carrier behaviors at different excitation energy levels;

[0009] (4) Perform deconvolution three-exponential fitting on the kinetics at different detection wavelengths, and subtract the fitting data from the original data to extract the coherent optical phonon oscillation signal;

[0010] (5) Perform periodic damped oscillation fitting on the coherent optical phonon oscillation signal to extract the coherent optical phonon frequency and amplitude;

[0011] (6) Plot the detection wavelength dependence of the coherent optical phonon amplitude at the same frequency and analyze as follows: The amplitude of the coherent optical phonon represents the coupling strength between the coherent optical phonon and carriers at different energy levels. The larger the oscillation amplitude, the higher the coupling degree.

[0012] The present invention has the following beneficial effects:

[0013] 1. The present invention uses supercontinuum white light pump-probe to perform transient absorption tests on two-dimensional transition metal dichalcogenides, and then obtains the phonon oscillation dynamics curve through exponential fitting residuals. The coupling relationship between optical phonons and carriers is analyzed by comparing the phonon amplitudes at different detection wavelengths. This method provides a simple, accurate and rigorous test analysis scheme for determining the coupling relationship between optical phonons and carriers in two-dimensional transition metal dichalcogenide films under various conditions, and is universal for two-dimensional transition metal dichalcogenides.

[0014] 2. By extracting the exponential fitting residuals of the transient absorption dynamics in the present invention, the oscillation dynamics of optical phonons is obtained; furthermore, fitting the oscillation dynamics can obtain information such as the amplitude and frequency of optical phonons, realizing a method for simply, quickly and accurately determining the optical phonon parameters inside the material.

[0015] 3. By analyzing the detection wavelength dependence of the optical phonon amplitude in the present invention, the coupling strength between optical phonons of different frequencies and carriers at different energy levels is obtained, making the analysis method of the present invention more scientific and rigorous. At the same time, the present invention is universal for various two-dimensional transition metal dichalcogenides. Description of the Drawings

[0016] Figure 1 For testing palladium diselenide using supercontinuum white light transmission pump-probe to obtain a broadband transient absorption map;

[0017] Figure 2 The optical phonon oscillation curve extracted from the exponential fitting residuals of the transient absorption dynamics;

[0018] Figure 3 The dependence diagram of the amplitudes of two optical phonons at 4.5 THz and 0.38 THz on the detection wavelength. Detailed Embodiments

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0021] Example 1

[0022] Palladium diselenide was tested using supercontinuum white light transmission pump-probe. The excitation wavelength was selected as 700 nm, and the detection wavelength range was between 380 nm and 800 nm, obtaining a broadband transient absorption spectrum, as Figure 1 shown. The test principle is as follows: Using the excitation wavelength will excite carriers from the ground state to different excited states. Subsequently, when using the probe light at the wavelength corresponding to the excited state energy level for detection, a negative signal will be obtained at the corresponding wavelength in the transient spectrum.

[0023] Extract the kinetic curve at the peak position of the negative signal at 390 nm for exponential fitting. Subtract the fitting data from the original data to obtain the kinetic curves of two coherent phonon oscillations at the kinetic rising edge from 0 - 2 ps and the kinetic falling edge from 2 - 10 ps, as Figure 2 shown. Use the periodic damped oscillation model to fit these two kinetic curves respectively to obtain two optical coherent phonon frequencies: 4.5 THz and 0.38 THz. At the same time, the amplitude at the detection wavelength of 390 nm can be obtained.

[0024] Extract the kinetic curves at multiple wavelengths of 390 nm, 411 nm, 458 nm, 525 nm, 580 nm, 639 nm, and 672 nm respectively, and repeat the above fitting process to obtain the amplitude at each detection wavelength, thereby obtaining the variation curve of the two optical phonon amplitudes with the detection wavelength, as Figure 3 shown. The larger the amplitude, the stronger the coupling between the optical phonon and the carriers at the energy level corresponding to the detection wavelength.

[0025] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for analyzing the coupling relationship between optical phonons and carriers based on transient observation technology, characterized in that: Including the following steps: (1) Using supercontinuum white light transmission pump-probe to test few-layer two-dimensional transition metal selenides to obtain broadband transient absorption data; (2) Extracting kinetic curves at different probe wavelengths from the broadband transient absorption data, and the kinetics at different probe wavelengths correspond to the carrier behavior at different excitation energy levels; (3) Performing deconvolution three-exponential fitting on the kinetics at different probe wavelengths, and subtracting the fitting data from the original data to extract the coherent optical phonon oscillation signal; (4) Performing periodic damped oscillation fitting on the coherent optical phonon oscillation signal to extract the coherent optical phonon frequency and amplitude; (5) Making a probe wavelength dependence plot of the coherent optical phonon amplitude at the same frequency, and the greater the oscillation amplitude, the higher the coupling strength between the coherent optical phonon and carriers at different energy levels.

2. The method for analyzing the coupling relationship between optical phonons and carriers based on transient observation technology according to claim 1, wherein: The few-layer two-dimensional transition metal selenides are grown on a substrate or transferred to a substrate.

3. The method for analyzing the coupling relationship between optical phonons and carriers based on transient observation technology according to claim 2, wherein: The substrate is made of transparent silica.

4. The method for analyzing the coupling relationship between optical phonons and carriers based on transient observation technology according to claim 1, wherein: In step (1), the detection range of the supercontinuum white light is 380 - 800 nm.

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