Optical device and method for enhancing spin coherent signals of perovskite quantum dots
By using an optical device with three pulsed light in perovskite quantum dots, electron-hole pairs are excited and interactions are weakened, and the problem of difficult spin-coherent signals at room temperature is solved, and effective enhancement and measurement of hole spin-coherent signals is achieved.
Patent Information
- Application Number
- CN202510357038.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2025-05-30
AI Technical Summary
The prior art is difficult to effectively measure spin-coherent signals in perovskite quantum dots at room temperature, especially hole spin-coherent signals, because these signals are very weak or even difficult to observe at room temperature.
An optical device using three beams of pulsed light is pump pulse, detection pulse and pre-pump pulse. The electron-hole pair is excited through the linearly polarized pre-pump pulse, which weakens the electron-hole exchange interaction, thereby enhancing the hole spin coherence signal.
The hole spin coherence signals in perovskite quantum dots are significantly enhanced, allowing these signals to be detected effectively at room temperature and improving measurement accuracy.
Smart Images
Figure CN120064146A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of spin research of perovskite materials, and is used to enhance the spin coherence signal in perovskite quantum dots with weak spin signals. In particular, it relates to an optical device and method for enhancing the hole spin coherence signal of perovskite quantum dots. Background Art
[0002] In recent years, lead halide perovskite quantum dots (APbX3; A = organic molecule or inorganic ion; X = Cl, Br, I) have been considered the most promising optoelectronic materials. They have a high luminescence quantum yield, a narrow spectral width, and excellent charge transfer characteristics, and are widely used in light-emitting diodes, lasers, and solar cells. By adjusting the composition and quantum size effect, their emission wavelength can be tuned within the entire visible light spectrum (410 nm - 700 nm). At the same time, lead halide perovskite quantum dots have a strong spin-orbit coupling effect due to the presence of lead and halides, which makes it easy to manipulate spins and spin-polarized currents, and is conducive to promoting the application of perovskite quantum dots in spintronics and quantum information. Currently, the common method for studying spins in perovskite quantum dots is two-beam pump-probe. Since the band structure of perovskite quantum dots is opposite to that of ordinary III-V and II-VI semiconductors, the spin-orbit coupling in perovskite materials mainly affects the conduction band rather than the valence band. At the same time, there is an electron-hole exchange interaction in perovskite quantum dots, which makes the spin coherence signal of neutral perovskite quantum dots measured by the two-beam pump-probe method at room temperature very weak or even undetectable. However, for the application of actual devices, it is very important to study the spin characteristics of perovskite quantum dots at room temperature. Summary of the Invention
[0003] The object of the present invention is to provide an optical device and method for enhancing the spin coherence signal of perovskite quantum dots in view of the deficiencies of the prior art. The present invention uses three pulsed lights, namely a pump pulse, a probe pulse, and a prepump pulse. With the device of the present invention, before the pump pulse and the probe pulse reach the sample, the linearly polarized prepump pulse first excites electron-hole pairs on the sample. Due to the presence of surface defect states in perovskite quantum dots, electrons transfer, the influence of the electron-hole exchange interaction on the spin signal weakens, and compared with the two-beam pump-probe, the number of quantum dots with a net positive charge increases, making the detected hole spin coherence signal in perovskite quantum dots further enhanced.
[0004] The specific technical solution for achieving the object of the present invention is as follows: An optical device for enhancing the spin coherence signal of perovskite quantum dots, characterized in that it includes a laser amplifier, a first optical parametric amplifier, a second optical parametric amplifier, a beam splitter, a first high reflector, a second high reflector, a third high reflector, a fourth high reflector, a first Glan prism, an electro-optic modulator, a quarter-wave plate, a first lens, a first mechanical delay line, a second Glan prism, a second lens, a second mechanical delay line, a third lens, an electromagnet system, a sample, a fourth lens, a half-wave plate, a Wollaston prism, a photoelectric balanced detector, a lock-in amplifier, a computer, a pump pulse, a probe pulse, and a prepump pulse; The laser amplifier, the first optical parametric amplifier and the beam splitter are optically connected; The beam splitter divides the optical path into two beams. One beam is that the probe pulse is optically connected to the third high reflector, the first mechanical delay line, the second Glan prism and the second lens in sequence, and finally enters the sample. The other beam is that the prepump pulse is optically connected to the first high reflector, the fourth high reflector, the second mechanical delay line and the third lens in sequence, and finally enters the sample; The laser amplifier, the second optical parametric amplifier, the second high reflector, the first Glan prism, the electro-optic modulator, the quarter-wave plate and the first lens are optically connected, and finally enter the sample; The probe pulse passes through the third high reflector, the first mechanical delay line, the second Glan prism and the second lens and is incident on the sample horizontally along the optical path; The pump pulse is generated after the light generated by the laser amplifier is modulated by the second optical parametric amplifier; it passes through the second high reflector and is incident on the sample at an inclination of 5 - 10°; The prepump pulse passes through the fourth high reflector and is incident on the sample at an inclination of 5 - 10°; the focusing points of the prepump pulse and the pump pulse on the sample coincide with the focusing point of the probe pulse on the sample; The fourth lens, the half-wave plate and the Wollaston prism are optically connected, and the Wollaston prism divides the light into two beams with perpendicular polarizations and enters the photoelectric balanced detector; The photoelectric balanced detector and the lock-in amplifier are connected by a data line; The first mechanical delay line, the second mechanical delay line, the lock-in amplifier and the computer are connected by data lines; The electromagnet system is located on both sides of the sample, and the generated magnetic field direction is perpendicular to the probe pulse direction. The method for enhancing the spin coherence signal of perovskite quantum dots by using the above optical device includes the following steps: (a) Place the perovskite quantum dots contained in a 1 mm optical path cuvette at the sample position in the center of the electromagnet system; (b) The light generated by the laser amplifier is modulated by the first optical parametric amplifier to emit laser pulses. The laser pulses are split by a beam splitter into probe pulses and prepump pulses. The light generated by the laser amplifier is modulated by the second optical parametric amplifier to generate pump pulses. The probe pulses are horizontally incident on the sample after passing through the third high reflector, the first mechanical delay line, the second Glan prism, and the second lens. The pump pulses are obliquely incident on the sample at an angle of 5-10° after passing through the second high reflector, the first Glan prism, the electro-optic modulator, the quarter-wave plate, and the first lens. The prepump pulses are obliquely incident on the sample at an angle of 5-10° after passing through the first high reflector, the fourth high reflector, the second mechanical delay line, and the third lens. The wavelengths of the pump pulses, probe pulses, and prepump pulses are modulated by the first optical parametric amplifier and the second optical parametric amplifier so that they are all in the absorption band region of the perovskite quantum dots. The pump pulses are circularly polarized light with left-handed and right-handed periodic modulation, and the average power is 100-1000 μW. The probe pulses are linearly polarized light, and the average power is 10-100 μW. The average power of the pump pulses is 10 times that of the probe pulses. The prepump pulses are linearly polarized pulses, and the average power is 1-5 mW. The spot size of the prepump pulses incident on the sample is 200-250 μm, the spot size of the pump pulses incident on the sample is 150-180 μm, and the spot size of the probe pulses incident on the sample is 100-130 μm. (c) Measurement of the spin coherence signal of perovskite quantum dots: The transmitted light of the probe pulses after passing through the sample passes through the fourth lens, the half-wave plate, and the Wollaston prism and is incident on the photoelectric balanced detector. The photoelectric balanced detector is connected to the lock-in amplifier by a data cable, and the experimental data is read through the lock-in amplifier. The lock-in amplifier, the first mechanical delay line, and the second mechanical delay line are connected to the computer by data cables. The computer controls the first mechanical delay line and the second mechanical delay line and reads the data on the lock-in amplifier in real time. Before detection, block the pump pulses and prepump pulses, adjust the half-wave plate so that the reading on the lock-in amplifier is zero, then release the pump pulses so that the pump pulses and the probe pulses are focused on the same point on the sample. Synchronously control the first mechanical delay line by the computer to adjust the time delay between the pump pulses and the probe pulses, and collect the data of the lock-in amplifier in real time to obtain the spin coherence signal of the perovskite quantum dots. (d) Enhancing the spin coherence signal of perovskite quantum dots: Release the pump pulses, probe pulses, and prepump pulses so that the three pulses are focused on the same point on the sample. Use the computer to control the second mechanical delay line so that the prepump pulses arrive at the sample before the pump pulses and the probe pulses. The specific time delay is adjusted as needed. After the time delay of the prepump pulses is fixed, use the computer to control the first mechanical delay line while collecting the data on the lock-in amplifier to obtain the enhanced spin coherence signal of the perovskite quantum dots.
[0005] Further description of the working process of the present invention: The prepump pulse is used to generate electron-hole pairs in the perovskite quantum dots, and the pump pulse is used to excite the spin polarization in the perovskite quantum dots. Since the refractive indices of the sample generating spin polarization for left-handed and right-handed circularly polarized light are different, the polarization direction of the linearly polarized probe pulse changes after passing through the sample. This change is reflected on the photoelectric balanced detector after passing through a half-wave plate and a Wollaston prism, and is finally collected by a lock-in amplifier. The delay of the prepump pulse is adjusted and fixed by a mechanical delay line, and the spin coherence signal in the perovskite quantum dots is detected by changing the delay between the pump pulse and the probe pulse. After the prepump pulse generates electron-hole pairs, due to the existence of surface defect states in the perovskite quantum dots, electrons transfer, leaving holes inside the perovskite quantum dots, which not only weakens the influence of the electron-hole exchange interaction on the spin signal, but also increases the number of quantum dots with a net positive charge, enabling the detection of a stronger hole spin coherence signal.
[0006] The present invention has the following advantages compared with common measurement techniques: high precision, simple experimental conditions, and can be used to detect the spin coherence signal in perovskite quantum dots with very weak signals or even undetectable signals at room temperature. Description of the Drawings
[0007] Figure 1 is a schematic structural diagram of the device of the present invention; Figure 2 is a schematic diagram of the spin coherence signal of perovskite quantum dots under different prepump pulse - pump pulse delays of the present invention. Detailed Embodiment
[0008] Referring to Figure 1 , the device of the present invention includes a laser amplifier 1, a first optical parametric amplifier 2, a second optical parametric amplifier 3, a beam splitter 4, a first high reflector 5, a second high reflector 6, a third high reflector 7, a fourth high reflector 8, a first Glan prism 9, an electro-optic modulator 10, a quarter-wave plate 11, a first lens 12, a first mechanical delay line 13, a second Glan prism 14, a second lens 15, a second mechanical delay line 16, a third lens 17, an electromagnet system 18, a sample 19, a fourth lens 20, a half-wave plate 21, a Wollaston prism 22, a photoelectric balanced detector 23, a lock-in amplifier 24, a computer 25, a pump pulse 26, a probe pulse 27, and a prepump pulse 28; The laser amplifier 1, the first optical parametric amplifier 2 and the beam splitter 4 are optically connected; The beam splitter 4 divides the optical path into two beams. One beam of light is that the detection pulse 27 is sequentially connected to the third high reflector 7, the first mechanical delay line 13, the second Glan prism 14, and the second lens 15 in the optical path, and finally enters the sample 19. The other beam of light is that the prepump pulse 28 is sequentially connected to the first high reflector 5, the fourth high reflector 8, the second mechanical delay line 16, and the third lens 17 in the optical path, and finally enters the sample 19; The laser amplifier 1, the second optical parametric amplifier 3, the second high reflector 6, the first Glan prism 9, the electro-optic modulator 10, the quarter-wave plate 11, and the first lens 12 are connected in the optical path and finally enter the sample 19; The detection pulse 27 passes through the third high reflector 7, the first mechanical delay line 13, the second Glan prism 14, and the second lens 15 and is incident on the sample 19 horizontally along the optical path; The pump pulse 26 is generated after the light generated by the laser amplifier 1 is modulated by the second optical parametric amplifier 3; it passes through the second high reflector 6 and is incident on the sample 19 at an inclination of 5 - 10°; The prepump pulse 28 passes through the fourth high reflector 8 and is incident on the sample 19 at an inclination of 5 - 10°; the focus points of the prepump pulse 28 and the pump pulse 26 on the sample 19 coincide with the focus point of the detection pulse 27 on the sample 19; The fourth lens 20, the half-wave plate 21, and the Wollaston prism 22 are connected in the optical path. The Wollaston prism 22 divides the light into two beams with perpendicular polarizations and enters the photoelectric balanced detector 23; The photoelectric balanced detector 23 and the lock-in amplifier 24 are connected by a data line; The first mechanical delay line 13, the second mechanical delay line 16, the lock-in amplifier 24, and the computer 25 are connected by data lines; The electromagnet system 18 is located on both sides of the sample 19, and the generated magnetic field direction is perpendicular to the direction of the detection pulse 27.
[0009] Refer to Figure 1 , the method of the present invention includes the following steps: (a) Place the perovskite quantum dots contained in a 1 mm optical path cuvette at the position of the sample 19 located at the center of the electromagnet system 18; (b)The light generated by the laser amplifier 1 is modulated by the first optical parametric amplifier 2 to emit laser pulses. The laser pulses are split by the beam splitter 4 into a probe pulse 27 and a prepump pulse 28. The light generated by the laser amplifier 1 is modulated by the second optical parametric amplifier 3 to generate a pump pulse 26. The probe pulse 27 is horizontally incident on the sample 19 after passing through the third high reflector 7, the first mechanical delay line 13, the second Glan prism 14, and the second lens 15. The pump pulse 26 is obliquely incident on the sample at an angle of 5-10° after passing through the second high reflector 6, the first Glan prism 9, the electro-optic modulator 10, the quarter-wave plate 11, and the first lens 12. The prepump pulse 28 is obliquely incident on the sample 19 at an angle of 5-10° after passing through the first high reflector 5, the fourth high reflector 8, the second mechanical delay line 16, and the third lens 17. The wavelengths of the pump pulse 26, the probe pulse 27, and the prepump pulse 28 are modulated by the first optical parametric amplifier 2 and the second optical parametric amplifier 3 so that they are all in the absorption band region of the perovskite quantum dots. The pump pulse 26 is a circularly polarized light with left-handed and right-handed periodic modulation, and the average power is 100-1000 μW. The probe pulse 27 is a linearly polarized light, and the average power is 10-100 μW. The average power of the pump pulse 26 is 10 times that of the probe pulse 27. The prepump pulse 28 is a linearly polarized pulse, and the average power is 1-5 mW. The spot size of the prepump pulse 28 incident on the sample is 200-250 μm, the spot size of the pump pulse 26 incident on the sample is 150-180 μm, and the spot size of the probe pulse 27 incident on the sample is 100-130 μm. (c)Measurement of the perovskite quantum dot spin coherence signal: The transmitted light of the probe pulse 27 through the sample passes through the fourth lens 20, the half-wave plate 21, and the Wollaston prism 22 and is incident on the photoelectric balanced detector 23. The photoelectric balanced detector 23 is connected to the lock-in amplifier 24 by a data cable. The experimental data is read through the lock-in amplifier 24. The lock-in amplifier 24, the first mechanical delay line 13, and the second mechanical delay line 16 are connected to the computer 25 by data cables. The computer 25 controls the first mechanical delay line 13 and the second mechanical delay line 16 and reads the data on the lock-in amplifier 24 in real time. Before detection, block the pump pulse 26 and the prepump pulse 28, adjust the half-wave plate 21 so that the reading on the lock-in amplifier 24 is zero, and then release the pump pulse 26 so that the pump pulse 26 and the probe pulse 27 are focused on the same point on the sample 19. Synchronously control the first mechanical delay line 13 by the computer 25 to adjust the delay between the pump pulse 26 and the probe pulse 27, and collect the data on the lock-in amplifier 24 in real time to obtain the spin coherence signal of the perovskite quantum dots. (d) Enhancing the spin coherence signal of perovskite quantum dots: Release the pump pulse 26, the probe pulse 27, and the prepump pulse 28, and focus the three pulses onto the same point on the sample 19. Use the computer 25 to control the second mechanical delay line 16 so that the prepump pulse 28 arrives at the sample 19 prior to the pump pulse 26 and the probe pulse 27. The specific delay time can be adjusted as needed. After the delay time of the prepump pulse 28 is fixed, use the computer 25 to control the first mechanical delay line 13 while collecting data on the lock-in amplifier 24 to obtain an enhanced spin coherence signal of perovskite quantum dots. Example
[0010] Refer to Figure 1 , the spin coherence signal of CsPbCl3 quantum dots was measured using the device of the present invention, and the specific steps are as follows: (a) Place the CsPbCl3 perovskite quantum dots contained in a 1-mm optical path cuvette at the position of the sample 19 in the center of the electromagnet system 18. (b) The light generated by the laser amplifier 1 is modulated by the first optical parametric amplifier 2 (picosecond optical parametric amplifier) to emit a laser pulse with a wavelength of 403 nm. The laser pulse is split into a probe pulse 27 and a prepump pulse 28 by the beam splitter 4. The light generated by the laser amplifier 1 is modulated by the second optical parametric amplifier 3 (femtosecond optical parametric amplifier) to generate a pump pulse 26 with a wavelength of 407 nm. The probe pulse 27 is horizontally incident on the sample 19 after passing through the third high reflector 7, the first mechanical delay line 13, the second Glan prism 14, and the second lens 15. The pump pulse 26 is obliquely incident on the sample at an angle of 5° after passing through the second high reflector 6, the first Glan prism 9, the electro-optic modulator 10, the quarter-wave plate 11, and the first lens 12. The prepump pulse 28 is obliquely incident on the sample 19 at an angle of 10° after passing through the first high reflector 5, the fourth high reflector 8, the second mechanical delay line 16, and the third lens 17. The pump pulse 26 is a circularly polarized light with left-handed and right-handed periodic modulation, and the average power is 500 μW. The probe pulse 27 is a linearly polarized light with an average power of 50 μW, and the average power of the pump pulse 26 is 10 times that of the probe pulse 27. The prepump pulse 28 is a linearly polarized pulse with an average power of 3 mW. The spot size of the prepump pulse 28 incident on the sample is 220 μm, the spot size of the pump pulse 26 incident on the sample is 180 μm, and the spot size of the probe pulse 27 incident on the sample is 110 μm. (c) Measurement of the spin coherence signal of perovskite quantum dots: The transmitted light of the probe pulse 27 passing through the sample passes through the fourth lens 20, the half-wave plate 21, and the Wollaston prism 22 and is incident on the photoelectric balanced detector 23. The photoelectric balanced detector 23 is connected to the lock-in amplifier 24 by a data cable, and the experimental data is read through the lock-in amplifier 24. The phase-locked amplifier 24, the first mechanical delay line 13, and the second mechanical delay line 16 are connected to the computer 25 via data lines. The computer 25 is used to control the first mechanical delay line 13 and the second mechanical delay line 16 and read the data on the phase-locked amplifier 24 in real time; Before detection, block the pump pulse 26 and the prepump pulse 28. Adjust the half-wave plate 21 so that the reading on the phase-locked amplifier 24 is zero. Then release the pump pulse 26 so that the pump pulse 26 and the probe pulse 27 are focused on the same point on the sample 19. Synchronously control the first mechanical delay line 13 by the computer 25 to adjust the delay between the pump pulse 26 and the probe pulse 27, and collect the data of the phase-locked amplifier 24 in real time to obtain the spin coherence signal of the perovskite quantum dots; (d) Enhancing the spin coherence signal of perovskite quantum dots: Release the pump pulse 26, the probe pulse 27, and the prepump pulse 28 so that the three pulses are focused on the same point on the sample 19. Use the computer 25 to control the second mechanical delay line 16 so that the prepump pulse 28 arrives at the sample 19 before the pump pulse 26 and the probe pulse 27 (the prepump light arrives at the sample 50 ps and 300 ps earlier than the pump light). After the delay of the prepump pulse 28 is fixed, use the computer 25 to control the first mechanical delay line 13 while collecting the data on the phase-locked amplifier 24 to obtain the enhanced spin coherence signal of the perovskite quantum dots.
[0011] Experimental results of enhancing the spin coherence signal of CsPbCl3 perovskite quantum dots: Refer to Figure 2 , which are the experimental results of enhancing the spin coherence signal of CsPbCl3 perovskite quantum dots. When the prepump pulse arrives at the perovskite quantum dots 50 ps earlier than the pump pulse, the spin coherence signal of the perovskite quantum dots is enhanced by 6 times. When the prepump pulse arrives at the perovskite quantum dots 300 ps earlier than the pump pulse, the spin coherence signal of the perovskite quantum dots is enhanced by 8.6 times.
Claims
1. An optical device for enhancing the spin coherence signal of perovskite quantum dots, characterized in that: It comprises a laser amplifier (1), a first optical parametric amplifier (2), a second optical parametric amplifier (3), a beam splitter (4), a first high reflective mirror (5), a second high reflective mirror (6), a third high reflective mirror (7), a fourth high reflective mirror (8), a first Glan prism (9), an electro-optic modulator (10), a quarter wave plate (11), a first lens (12), a first mechanical delay line (13), a second Glan prism (14), a second lens (15), a second mechanical delay line (16), a third lens (17), an electromagnet system (18), a sample (19), a fourth lens (20), a half wave plate (21), a Wollaston prism (22), a photoelectric balanced detector (23), a phase-locked amplifier (24), a computer (25), a pump pulse (26), a detection pulse (27) and a pre-pump pulse (28); The laser amplifier (1), the first optical parametric amplifier (2) and the beam splitter (4) are optically connected; The beam splitter (4) divides the optical path into two beams, one beam of light is a detection pulse (27) which is sequentially connected to the optical path of the third high-reflection mirror (7), the first mechanical delay line (13), the second Glan prism (14) and the second lens (15), and finally incident on the sample (19), and the other beam of light is a pre-pump pulse (28) which is sequentially connected to the optical path of the first high-reflection mirror (5), the fourth high-reflection mirror (8), the second mechanical delay line (16) and the third lens (17), and finally incident on the sample (19); The laser amplifier (1), the second optical parametric amplifier (3), the second high-reflection mirror (6), the first Glan prism (9), the electro-optic modulator (10), the quarter-wave plate (11) and the first lens (12) are optically connected and finally incident on the sample (19); The detection pulse (27) passes through the third high-reflection mirror (7), the first mechanical delay line (13), the second Glan prism (14) and the second lens (15) and is horizontally incident on the sample (19) along the optical path; The pump pulse (26) is generated by light generated by the laser amplifier (1) after being modulated by the second optical parametric amplifier (3); it passes through the second high-reflection mirror (6) and is incident on the sample (19) at an angle of 5-10 degrees; The pre-pump pulse (28) passes through the fourth high-reflection mirror (8) and is incident on the sample (19) at an angle of 5-10 degrees; the focusing point of the pre-pump pulse (28) and the pump pulse (26) on the sample (19) coincides with the focusing point of the detection pulse (27) on the sample (19); The fourth lens (20), the half wave plate (21), and the Wollaston prism (22) are connected in an optical path, and the Wollaston prism (22) divides the light into two beams of light with perpendicular polarizations and enters a photoelectric balance detector (23); The photoelectric balance detector (23) and the lock-in amplifier (24) are connected by a data line; The first mechanical delay line (13), the second mechanical delay line (16), the phase-locked amplifier (24) and the computer (25) are connected by a data line; The electromagnet system (18) is located on both sides of the sample (19), and the direction of the generated magnetic field is perpendicular to the direction of the detection pulse (27).
2. A method for enhancing the spin coherence signal of perovskite quantum dots based on the optical device of claim 1, characterized in that: The method comprises the following steps: (a) The perovskite quantum dots in a cuvette with an optical path length of 1 mm are placed at the sample (19) located in the center of the electromagnet system (18); (b) The light generated by the laser amplifier (1) is modulated by the first optical parametric amplifier (2) to emit a laser pulse. The laser pulse is divided into a detection pulse (27) and a pre-pump pulse (28) by a beam splitter (4). The light generated by the laser amplifier (1) is modulated by the second optical parametric amplifier (3) to generate a pump pulse (26). The detection pulse (27) is horizontally incident on the sample (19) after passing through the third high-reflection mirror (7), the first mechanical delay line (13), the second Glan prism (14) and the second lens (15). The pump pulse (26) is horizontally incident on the sample (19) after passing through the second high-reflection mirror (6), the first Glan prism (9), the electro-optic modulator (10), the four The one-tenth wave plate (11) and the first lens (12) are incident on the sample at an angle of 5-10 degrees, and the pre-pump pulse (28) is incident on the sample (19) at an angle of 5-10 degrees through the first high-reflection mirror (5), the fourth high-reflection mirror (8), the second mechanical delay line (16) and the third lens (17); the wavelength of the light is modulated by the first optical parametric amplifier (2) and the second optical parametric amplifier (3), so that the wavelengths of the pump pulse (26), the detection pulse (27) and the pre-pump pulse (28) are all in the absorption band region of the perovskite quantum dot; the pump pulse (26) is a circularly polarized light that is periodically modulated in left-handed and right-handed rotation, and the average power is 100-1000 μW; the detection pulse (27) is linearly polarized light with an average power of 10-100 μW, and the average power of the pump pulse (26) is 10 times that of the detection pulse (27); the pre-pump pulse (28) is a linearly polarized pulse with an average power of 1-5 mW, the spot size of the pre-pump pulse (28) incident on the sample is 200-250 μm, the spot size of the pump pulse (26) incident on the sample is 150-180 μm, and the spot size of the detection pulse (27) incident on the sample is 100-130 μm; (c) Measurement of perovskite quantum dot spin coherence signal: After the detection pulse (27) passes through the sample, the transmitted light passes through the fourth lens (20), the half-wave plate (21), and the Wollaston prism (22) and is incident on the photoelectric balance detector (23). The photoelectric balance detector (23) is connected to the phase-locked amplifier (24) by a data line, and the experimental data is read through the phase-locked amplifier (24); The phase-locked amplifier (24), the first mechanical delay line (13), and the second mechanical delay line (16) are connected to a computer (25) via a data line, and the computer (25) is used to control the first mechanical delay line (13), the second mechanical delay line (16), and read the data on the phase-locked amplifier (24) in real time; Before detection, the pump pulse (26) and the pre-pump pulse (28) are blocked, the half wave plate (21) is adjusted so that the reading on the phase-locked amplifier (24) is zero, and then the pump pulse (26) is released so that the pump pulse (26) and the detection pulse (27) are focused on the same point on the sample (19), and the first mechanical delay line (13) is synchronously controlled by a computer (25) to adjust the delay of the pump pulse (26) and the detection pulse (27), and the data of the phase-locked amplifier (24) is collected in real time to obtain the spin coherence signal of the perovskite quantum dot; (d) Enhancement of the spin coherence signal of the perovskite quantum dot: release the pump pulse (26), the detection pulse (27) and the pre-pump pulse (28) so that the three pulses are focused on the same point on the sample (19), and use the computer (25) to control the second mechanical delay line (16) so that the pre-pump pulse (28) arrives at the sample (19) before the pump pulse (26) and the detection pulse (27). The specific delay is adjusted as needed. After the delay of the pre-pump pulse (28) is fixed, use the computer (25) to control the first mechanical delay line (13) while collecting data on the phase-locked amplifier (24) to obtain an enhanced perovskite quantum dot spin coherence signal.