All-optical time-domain pulse width measurement device and method based on perturbation self-diffraction effect

Abstract

The application discloses a kind of full-optical time-domain pulse width measuring device and method based on perturbation self-diffraction effect, existing frequency domain measurement technique is difficult in the technical problem of measuring periodicity order pulse, specifically including beam splitter, delay unit, beam combiner, light splitter, first focusing mirror, nonlinear grating, filter plate and spectrometer;Beam splitter is used to divide the light to be measured into reflected light and transmitted light;Delay unit is arranged on the light path where the transmitted light is, for delaying the transmitted light;Beam combiner is used to combine the reflected light and the transmitted light after the action of delay unit, to form combined light;Light splitter, first focusing mirror, nonlinear grating, filter plate and spectrometer are sequentially arranged on the light path where the combined light is along the emission direction;Nonlinear grating is used to make focused light beam produce self-diffraction signal;Filter plate is used to extract first-order self-diffraction signal from self-diffraction signal to spectrometer, so that the spectrometer obtains corresponding self-diffraction spectrum intensity data.

Description

Technical Field

[0001] This invention relates to a pulse width measurement device and method, specifically to an all-optical time-domain pulse width measurement device and method based on perturbation self-diffraction effect. Background Technology

[0002] Since the 1990s, ultrashort laser pulse technology has made significant progress. Currently, the temporal width of laser pulses can be controlled within a few or even a single optical cycle. Against this backdrop, both the development of ultrafast laser technology itself and its applications in cutting-edge fields such as physics, chemistry, biology, and materials science have placed higher demands on the precise measurement of the temporal characteristics of laser pulses. High-precision temporal information measurement makes it possible to directly observe ultrafast processes such as charge transfer, photoelectric emission delay, and semiconductor bandgap dynamics, providing a powerful experimental tool for a deeper understanding of the fundamental laws of the material world.

[0003] For ultrashort pulses on the femtosecond scale, their duration is far shorter than the response time of electronic detectors, making it difficult to directly obtain crucial information such as pulse width and phase. To address this challenge, researchers have developed various measurement techniques, typically performed in the frequency or time domain. Frequency-domain methods, such as frequency-resolved optical switching (FROG) and dispersive scanning, indirectly reconstruct the temporal envelope and phase of the pulse by measuring spectral information generated by nonlinear processes. However, these methods face difficulties when measuring pulses on the order of periods and rely on complex inversion and reconstruction algorithms, failing to accurately reconstruct ultrashort pulses with complex spectral structures. Time-domain methods, on the other hand, construct ultrafast time gates to directly sample the pulse under test, thereby obtaining its photoelectric field information. For example, perturbation tunneling ionization (TIPTOE) methods for time-domain electric field observation typically achieve time-domain sampling based on higher-order nonlinear processes such as ionization or multiphoton effects. However, these methods are limited in terms of the intensity and wavelength of the pulse under test, making it difficult to meet the compatibility requirements of different wavelength bands. Summary of the Invention

[0004] To address the challenges of existing frequency domain measurement techniques in measuring pulses on the order of period, which rely on complex inversion and reconstruction algorithms and cannot accurately reconstruct ultrashort pulses with complex spectral structures, and the limitations of time domain measurement methods in terms of the intensity and band of the pulse under test, making it difficult to meet the compatibility requirements of different bands, this invention provides an all-optical time domain pulse width measurement device and method based on the perturbation self-diffraction effect.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A fully optical time-domain pulse width measurement device based on perturbation self-diffraction effect, characterized by: It includes a beam splitter, a delay unit, a beam combiner, a beam splitter, a first focusing lens, a nonlinear grating, a filter, and a spectrometer; The aforementioned beam splitter is used to separate the light to be measured into reflected light and transmitted light; The aforementioned delay unit is set in the optical path of the transmitted light and is used to delay the transmitted light; The aforementioned beam combiner is used to combine the reflected light and the transmitted light after the delay unit to form a combined beam. The aforementioned beam splitter, first focusing lens, nonlinear grating, filter plate, and spectrometer are arranged sequentially along the output direction in the optical path of the combined beam; The aforementioned beam splitter is used to separate multiple beams of light with identical parameters from a combined beam; The first focusing lens described above is used to focus all the split beams onto the nonlinear grating; The aforementioned nonlinear grating is used to cause the focused beam to self-diffract, generating a self-diffracted signal; The aforementioned filter is used to extract the first-order self-diffraction signal from the self-diffraction signal and send it to the spectrometer; The aforementioned spectrometer is used to acquire the corresponding self-diffraction spectral intensity data.

[0006] Furthermore, both the beam splitter and beam combiner mentioned above are wedge-shaped mirrors with an apex angle ranging from 2° to 4°.

[0007] Furthermore, it also includes a first reflecting mirror group; The first set of reflecting mirrors is positioned in the optical path of the reflected light and is used to reflect the reflected light to the beam combiner.

[0008] Furthermore, the aforementioned delay unit includes a second reflector group and a displacement platform; The aforementioned second set of reflecting mirrors is positioned in the optical path of the transmitted light and is used to reflect the transmitted light to the beam combiner. The aforementioned displacement platform is located at the bottom of the second reflector group, and is used to delay the transmitted light by moving the second reflector group.

[0009] Furthermore, the aforementioned beam splitter is a baffle with two first light-passing holes, used to separate two beams of light with identical parameters from the combined beam; The aperture of the first light-transmitting hole mentioned above ranges from 0.5mm to 1.5mm.

[0010] Furthermore, the aforementioned nonlinear grating is made of fused silica with a thickness ranging from 50 to 100 μm.

[0011] Furthermore, the aforementioned filter plate is a baffle plate with a second light-transmitting hole; The aperture of the second light-transmitting hole mentioned above ranges from 0.5mm to 1.5mm.

[0012] Furthermore, it also includes a second focusing lens; The aforementioned second focusing mirror is positioned between the filter plate and the spectrometer to focus the beam corresponding to the first-order self-diffraction signal onto the spectrometer.

[0013] Furthermore, it also includes dispersion balancing mirrors; The aforementioned dispersion balancing mirror is positioned between the beam splitter and the first reflecting mirror group to balance the dispersion introduced when the light to be measured passes through the beam splitter.

[0014] An all-optical time-domain pulse width measurement method based on perturbation self-diffraction effect, employing the aforementioned all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect, is characterized by including the following steps: Step 1: The beam splitter receives the light to be measured and splits it into reflected light and transmitted light. The reflected light is used as a perturbation pulse and the transmitted light is used as a driving pulse. The beam combiner combines the reflected light and transmitted light to form a combined beam. The beam splitter separates multiple beams with the same parameters from the combined beam. These beams are then focused by the first focusing lens onto a nonlinear grating, where self-diffraction occurs, generating a self-diffraction signal. The filter extracts the first-order self-diffraction signal from the self-diffraction signal and sends it to the spectrometer. The spectrometer obtains the corresponding self-diffraction spectral intensity data. Step 2: The transmitted light is delayed multiple times by the delay unit, thereby adjusting the relative delay of the perturbation pulse and the driving pulse, so that the spectrometer can obtain self-diffraction spectral intensity data under different delays. Step 3: Integrate the self-diffraction spectral intensity data under different delays to obtain the original modulation signal; Step 4: Perform a Fourier transform on the original modulation signal to obtain the spectral amplitude and phase information of the light to be measured. Step 5: Perform inverse Fourier transform on the above spectral amplitude and phase information to obtain the pulse width of the light to be measured, thus completing the all-optical time-domain pulse width measurement based on the perturbation self-diffraction effect.

[0015] The beneficial effects of this invention are: 1. Significantly reduces the measurement intensity threshold: This invention provides an all-optical time-domain pulse width measurement device and method based on perturbation self-diffraction effect. It utilizes the self-diffraction effect to construct an ultrafast time gate to achieve time-domain sampling measurement of laser pulse width. Compared with traditional time-domain sampling measurement techniques based on high-order nonlinear processes such as material photoionization or multiphoton effects, the self-diffraction effect used in this invention is a third-order nonlinear optical process, which significantly reduces the intensity requirement of the pulse under test and effectively expands the energy range of measurable pulses.

[0016] 2. The optical path structure is simple, requiring no polarization or beam splitting components: The present invention provides an all-optical time-domain pulse width measurement device and method based on perturbation self-diffraction effect. Through the interaction between self-diffraction effect and non-collinearity, the generated self-diffraction signal is consistent with the center wavelength of the pulse to be measured. Therefore, the measurement device only needs to be equipped with a filter plate to achieve signal separation, without the need for additional polarization or beam splitting elements, which significantly simplifies the device structure and improves system stability and ease of assembly and adjustment.

[0017] 3. Highly efficient data processing, requiring no complex inversion iterative algorithms: As a time-domain sampling measurement technique, this invention only requires Fourier transform operations to obtain the time-domain and frequency-domain information of the pulse under test, avoiding the time-consuming inversion and iteration process in frequency-domain measurement methods, and significantly improving computational efficiency.

[0018] 4. Low-cost dielectric material with wide applicability across various frequency bands: This invention uses fused silica as the medium for generating the self-diffraction effect, which is low in cost and readily available. In addition, fused silica has high optical transmittance in the ultraviolet to mid-infrared bands, making this invention suitable for pulse width measurement over a wide band and giving it good versatility. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an embodiment of the all-optical time-domain pulse width measurement device based on the perturbation self-diffraction effect of the present invention; Figure 2 This is a schematic diagram of the structure of the beam splitter in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the filter plate in an embodiment of the present invention; Figure 4 This is a graph showing the intensity of the self-diffraction signal under different delays obtained in step 2 of this embodiment of the invention. Figure 5 This is a normalized time-domain intensity curve of the light to be measured in an embodiment of the present invention.

[0020] The attached figures are labeled as follows: 1. Beam splitter; 2. Delay unit; 3. Beam combiner; 4. Beam splitter; 41. First aperture; 5. First focusing lens; 6. Nonlinear grating; 7. Filter plate; 71. Second aperture; 8. Spectrometer; 9. First mirror group; 10. Second mirror group; 11. Second focusing lens; 12. Dispersion balancing mirror; 13. Laser. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides an all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect, such as... Figure 1 As shown, the pulse width measurement device includes a beam splitter 1, a beam combiner 3, a beam splitter 4, a first focusing mirror 5, a nonlinear grating 6, a filter 7, a spectrometer 8, a first reflecting mirror group 9, a second focusing mirror 11, and a dispersion balancing mirror 12; the delay unit 2 includes a displacement platform and a second reflecting mirror group 10.

[0023] Beam splitter 1 is used to split the light under test into reflected light and transmitted light, wherein the reflected light serves as a perturbation pulse and the transmitted light serves as a driving pulse; in this embodiment, the light under test is emitted from laser 13. Beam splitter 1 is a wedge-shaped mirror with an apex angle ranging from 2° to 4°. In this embodiment, beam splitter 1 is an uncoated fused silica wedge-shaped mirror with an apex angle of 2.8°, a size of 20*30mm, and a reflectivity of 8%.

[0024] The first reflector group 9 is disposed in the optical path of the reflected light and is used to reflect the reflected light to the beam combiner 3. Specifically, the first reflector group 9 includes two reflectors with their reflective surfaces arranged at 90°; in other embodiments, a right-angle prism or a corner prism may also be used.

[0025] A dispersion balancing mirror 12 is disposed between the beam splitter 1 and the first reflecting mirror group 9 to balance the dispersion introduced by the light to be measured when it passes through the beam splitter 1. In this embodiment, the dispersion balancing mirror 12 is made of a fused silica sheet with a thickness of 1 mm and a diameter of 25.4 mm.

[0026] The second reflector group 10 is disposed in the optical path of the transmitted light and is used to reflect the transmitted light to the beam combiner 3. Specifically, like the first reflector group 9, the second reflector group 10 includes two reflectors with their reflective surfaces arranged at 90°; in other embodiments, a right-angle prism or a corner prism may also be used.

[0027] A displacement platform is located at the bottom of the second reflector group 10, used to delay transmitted light by moving the second reflector group 10. In this embodiment, the displacement platform is a piezoelectric ceramic displacement stage.

[0028] The beam combiner 3 is used to combine the reflected light and the transmitted light after the delay unit 2 to form a combined beam. The beam combiner 3 is a wedge-shaped mirror with a vertex angle ranging from 2° to 4°. In this embodiment, the beam combiner 3 is also an uncoated fused silica wedge-shaped mirror with a vertex angle of 2.8°, a size of 20*30mm, and a reflectivity of 8%.

[0029] The beam splitter 4, the first focusing lens 5, the nonlinear grating 6, the filter plate 7, and the spectrometer 8 are arranged sequentially along the output direction on the optical path of the combined beam.

[0030] like Figure 2 As shown, the beam splitter 4 is used to separate multiple beams of light with identical parameters from the combined beam. In this embodiment, the beam splitter 4 is a baffle with two first light-transmitting holes 41, used to separate two beams of light with identical parameters from the combined beam. The aperture range of the first light-transmitting holes 41 is 0.5mm to 1.5mm. In this embodiment, the diameter of the beam splitter 4 is 25.4mm, and the aperture of the first light-transmitting holes 41 is a 1mm pinhole, spaced 2mm apart.

[0031] The first focusing lens 5 is used to focus all the split beams onto the nonlinear grating; in this embodiment, the first focusing lens 5 is a concave silver-plated reflector with a focal length of 100mm.

[0032] The nonlinear grating 6 is used to induce self-diffraction of the focused beam, generating a self-diffraction signal. The nonlinear grating 6 is made of fused silica with a thickness ranging from 50 to 100 μm. In this embodiment, the nonlinear grating 6 is a thin sheet of fused silica with a diameter of 12.7 mm and a thickness of 50 μm.

[0033] like Figure 3 As shown, the filter plate 7 extracts the first-order self-diffraction signal from the self-diffraction signal and sends it to the spectrometer 8; the filter plate 7 is a baffle with a second light-transmitting hole 71; the aperture of the second light-transmitting hole 71 ranges from 0.5 mm to 1.5 mm. In this embodiment, the diameter of the filter plate 7 is 25.4 mm, and the aperture of the second light-transmitting hole 71 is 1 mm.

[0034] The second focusing mirror 11 is disposed between the filter plate 7 and the spectrometer 8, and is used to focus the light beam corresponding to the first-order self-diffraction signal onto the spectrometer 8. In this embodiment, the focal length of the second focusing mirror 11 is 50mm.

[0035] Spectrometer 8 is used to acquire the corresponding self-diffraction spectral intensity data.

[0036] First, this device utilizes the interaction between self-diffraction and non-collinearity, generating a self-diffraction signal that matches the center wavelength of the pulse under test. Therefore, no polarization or beam-splitting elements are required; only a transparent nonlinear medium and a suitable detector are needed to achieve ultrashort pulse measurements in the ultraviolet to mid-infrared bands. Second, this device is based on time-domain sampling measurements, eliminating the need for inversion iterative algorithms and resulting in high computational efficiency. Finally, due to the high third-order nonlinear polarizability of the medium, the required light intensity is significantly reduced compared to traditional time-domain sampling techniques, improving the device's practicality.

[0037] This invention provides an all-optical time-domain pulse width measurement method based on perturbation self-diffraction effect, employing the aforementioned all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect, specifically including the following steps: Step 1: Beam splitter 1 receives the light to be tested and splits it into reflected and transmitted light. The reflected light serves as a perturbation pulse, and the transmitted light serves as a driving pulse. The reflected light passes through dispersion balancing mirror 12 to balance the dispersion introduced into the light when passing through beam splitter 1, and then undergoes two reflections by the first reflecting mirror group 9 before entering beam combiner 3. The transmitted light undergoes two reflections by the second reflecting mirror group 10 before entering beam combiner 3. Beam combiner 3 combines the reflected and transmitted light to form a combined beam. After combination, the energy of the perturbation pulse is approximately 0.8 times that of the driving pulse. The beam splitter 4 separates two beams from the combined beam, each with identical parameters (i.e., spot size, energy, wavelength, pulse width, etc.). These beams are then focused by the first focusing lens 5 (focal length 100mm) onto the nonlinear grating 6, where self-diffraction occurs, generating a self-diffraction signal (i.e., SD signal). The filter 7 extracts the first-order self-diffraction signal from the self-diffraction signal, and the second focusing lens 11 (focal length 50mm) focuses the beam corresponding to the first-order self-diffraction signal onto the spectrometer 8. The spectrometer 8 then obtains the corresponding self-diffraction spectral intensity data.

[0038] It should be noted that the position of the filter plate 7 can be manually adjusted so that the beam corresponding to the first-order self-diffraction signal can pass accurately through the second light-transmitting aperture 71.

[0039] Step 2: The transmitted light is delayed multiple times using delay unit 2, thereby adjusting the relative delay between the perturbation pulse and the driving pulse, such as... Figure 4 As shown, the modulation of the SD signal spectral intensity can be observed, enabling the spectrometer 8 to obtain self-diffraction spectral intensity data under different delays.

[0040] Step 3: Integrate the self-diffraction spectral intensity data under different delays to obtain the original modulation signal.

[0041] Step 4: Perform a Fourier transform on the original modulation signal to obtain the spectral amplitude and phase information of the light to be measured.

[0042] Step 5: Perform inverse Fourier transform on the spectral amplitude and phase information to obtain the electric field amplitude and phase information of the light under test. The modulus square of the electric field amplitude is the time-domain intensity of the electric field. Normalize it and calculate the pulse width of the light under test, thus completing the all-optical time-domain pulse width measurement based on the perturbation self-diffraction effect; Figure 5 As shown, the pulse width of laser 13 is 42 fs.

[0043] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect, characterized in that: It includes a beam splitter (1), a delay unit (2), a beam combiner (3), a beam splitter (4), a first focusing lens (5), a nonlinear grating (6), a filter plate (7), and a spectrometer (8); The beam splitter (1) is used to split the light to be measured into reflected light and transmitted light; The delay unit (2) is disposed on the optical path of the transmitted light and is used to delay the transmitted light; The beam combiner (3) is used to combine the reflected light and the transmitted light after the delay unit (2) to form a beam combined light; The beam splitter (4), the first focusing lens (5), the nonlinear grating (6), the filter plate (7) and the spectrometer (8) are arranged sequentially along the output direction on the optical path of the combined beam; The beam splitter (4) is used to separate multiple beams of light with the same parameters from the combined beam; The first focusing lens (5) is used to focus all the beams into the nonlinear grating (6). The nonlinear grating (6) is used to cause the focused beam to self-diffract, thereby generating a self-diffracted signal; The filter plate (7) is used to extract the first-order self-diffraction signal from the self-diffraction signal and send it to the spectrometer (8). The spectrometer (8) is used to acquire the corresponding self-diffraction spectral intensity data.

2. The all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect according to claim 1, characterized in that: Both the beam splitter (1) and the beam combiner (3) are wedge-shaped mirrors with an apex angle ranging from 2° to 4°.

3. The all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect according to claim 1 or 2, characterized in that: It also includes the first reflecting mirror group (9); The first reflector group (9) is set in the optical path of the reflected light and is used to reflect the reflected light to the beam combiner (3).

4. The all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect according to claim 3, characterized in that: The delay unit (2) includes a second reflector group (10) and a displacement platform; The second reflector group (10) is set in the optical path of the transmitted light and is used to reflect the transmitted light to the beam combiner (3). The displacement platform is located at the bottom of the second reflector group (10) and is used to delay the transmitted light by moving the second reflector group (10).

5. The all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect according to claim 4, characterized in that: The beam splitter (4) is a baffle with two first light-passing holes (41) for splitting two beams of light with the same parameters from the combined beam; The aperture of the first light-transmitting hole (41) ranges from 0.5 mm to 1.5 mm.

6. The all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect according to claim 5, characterized in that: The nonlinear grating (6) is made of fused silica with a thickness ranging from 50 to 100 μm.

7. The all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect according to claim 6, characterized in that: The filter plate (7) is a baffle with a second light-transmitting hole (71); The aperture of the second light-transmitting hole (71) ranges from 0.5 mm to 1.5 mm.

8. The all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect according to claim 7, characterized in that: It also includes a second focusing lens (11); The second focusing lens (11) is disposed between the filter plate (7) and the spectrometer (8) to focus the beam corresponding to the first-order self-diffraction signal onto the spectrometer (8).

9. The all-optical time-domain pulse width measurement device based on perturbation self-diffraction effect according to claim 8, characterized in that: It also includes a dispersion balancing mirror (12); The dispersion balancing mirror (12) is positioned between the beam splitter (1) and the first reflecting mirror group (9) to balance the dispersion introduced when the light to be measured passes through the beam splitter (1).

10. A method for measuring the pulse width in the entire optical time domain based on the perturbation self-diffraction effect, employing the all-optical pulse width measurement device based on the perturbation self-diffraction effect as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: The beam splitter (1) receives the light to be measured and splits it into reflected light and transmitted light. The reflected light is used as a perturbation pulse and the transmitted light is used as a driving pulse. The beam combiner (3) combines the reflected light and transmitted light to form a combined beam. The beam splitter (4) separates multiple beams with the same parameters from the combined beam. The beams are then focused by the first focusing lens (5) onto the nonlinear grating (6) to generate self-diffraction and a self-diffraction signal. The filter (7) extracts the first-order self-diffraction signal from the self-diffraction signal and sends it to the spectrometer (8). The spectrometer (8) obtains the corresponding self-diffraction spectral intensity data. Step 2: The transmitted light is delayed multiple times by the delay unit (2), thereby adjusting the relative delay of the perturbation pulse and the driving pulse, so that the spectrometer (8) can obtain self-diffraction spectral intensity data under different delays. Step 3: Integrate the self-diffraction spectral intensity data under different delays to obtain the original modulation signal; Step 4: Perform a Fourier transform on the original modulation signal to obtain the spectral amplitude and phase information of the light to be measured; Step 5: Perform inverse Fourier transform on the spectral amplitude and phase information to obtain the pulse width of the light to be measured, thus completing the all-optical time-domain pulse width measurement based on the perturbation self-diffraction effect.

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