Ultrashort pulse measurement device and method based on transient grating modulation sampling

Abstract

The present invention relates to a pulse measurement device and a method for using the same, and in particular to an ultrashort pulse measurement device and a method based on transient grating modulation sampling, in order to solve the shortcomings of the prior art that the measurement method is complex and difficult, or that ultrashort pulse lasers in the visible light and near-infrared bands are difficult to simply and effectively measure due to the limitation of the waveband. The present invention includes a beam splitter, a first reflector, a delay line, and a pair of wedges, a three-hole aperture, a focusing mirror, a transient grating crystal, and a detector sequentially arranged along the optical path; the beam splitter is located on the output optical path of the femtosecond laser to be measured, and is used to divide the output light of the femtosecond laser to be measured into a fundamental frequency beam and a beam to be measured; the wedge pair combines the fundamental frequency beam and the beam to be measured, and the combined light finally passes through the transient grating crystal; the delay line can be adjusted to obtain transient grating signal lights of different intensities, and the spectrum, pulse width, and phase information of the femtosecond laser to be measured are obtained after simple conversion.

Description

Technical Field

[0001] The invention relates to a pulse measuring device and a use method thereof, and in particular to an ultrashort pulse measuring device and a measuring method based on transient grating modulation sampling. Background Art

[0002] As a powerful tool for exploring the microscopic material world, ultrashort pulse lasers are widely used in the fields of chemistry, biomedicine, and materials science. Therefore, the various properties of ultrashort pulse lasers need to be characterized very accurately so that they can be used as a tool to detect microscopic physical phenomena at the atomic and molecular levels.

[0003] In recent years, the time-domain electric field measurement method (TIPTOE) based on the tunneling ionization perturbation theory can measure pulsed lasers of any wavelength greater than 2.5 times the fluorescence wavelength, and can obtain information such as the wavelength, pulse width, and phase of ultrashort laser pulses without complex inversion calculations. At present, the scheme using TIPTOE usually includes two types of media, gas or solid. The fluorescence band of the gas medium is in the extreme ultraviolet, and the entire measurement device needs to work in a vacuum. The fluorescence detector is relatively complex, which makes the operation difficult. The energy band fluorescence of the solid medium can be close to 400nm, which is easy to detect, but the band limitation of more than 2.5 times makes it impossible to simply and effectively measure the commonly used ultrashort pulse lasers in the visible light and near-infrared bands. Summary of the invention

[0004] In order to solve the shortcomings of the prior art that the measurement method is complicated and difficult, or that ultrashort pulse lasers in the visible light and near-infrared bands are difficult to measure simply and effectively due to the limitation of the band, the present invention provides an ultrashort pulse measurement device and measurement method based on transient grating modulation sampling.

[0005] To achieve the above objectives, the technical solutions provided by the present invention are as follows:

[0006] The invention discloses an ultrashort pulse measurement device based on transient grating modulation sampling, which is special in that it comprises a beam splitter, a first reflector, a delay line, and a wedge pair, a three-hole aperture, a focusing mirror, a transient grating crystal and a detector which are sequentially arranged along the optical path; the beam splitter is located on the exit optical path of a femtosecond laser to be measured, and is used to split the exit light of the femtosecond laser to be measured into a fundamental frequency beam and a beam to be measured; the first reflector and the delay line are respectively located on the reflection optical path and the transmission optical path of the beam splitter, and are used to reflect the fundamental frequency beam and the beam to be measured; the wedge pair is located at the intersection of the reflection optical paths of the first reflector and the delay line, and is used to combine the fundamental frequency beam and the beam to be measured, and the energy ratio of the fundamental frequency beam to the beam to be measured in the combined beam is between 1:100 and 1:1000; the combined beam is divided into three laser beams with the same parameters through the three-hole aperture, and is focused into the transient grating crystal through the focusing mirror to generate signal light of the transient grating; the detector is used to measure the signal light intensity of the transient grating.

[0007] Furthermore, the transient grating crystal is amorphous fused quartz with a thickness of 50 μm.

[0008] Furthermore, the ratio of reflected light to transmitted light of the beam splitter is 1:1, and the reflected and transmitted energies are consistent.

[0009] Furthermore, the delay line includes piezoelectric ceramics, and a second reflector and a third reflector arranged on the piezoelectric ceramics along the optical path.

[0010] Furthermore, the first reflector, the second reflector and the third reflector are high-reflection mirrors with a reflectivity greater than 99%.

[0011] Furthermore, the connecting line of the three holes of the three-hole aperture forms an isosceles right triangle.

[0012] Furthermore, the focusing mirror is a concave silver mirror with a focal length of 100 mm.

[0013] Furthermore, the detector is a silicon-based camera or a spectrometer.

[0014] The present invention also provides a method for measuring ultrashort pulses based on transient grating modulation sampling, using the above-mentioned ultrashort pulse measurement device based on transient grating modulation sampling, which is special in that:

[0015] Step 1: Use a beam splitter to split the laser into a fundamental frequency beam and a beam to be measured with equal energy, introduce the beam to be measured into a delay line, and after the fundamental frequency beam is reflected by a first reflector, use a wedge pair to combine the fundamental frequency beam and the beam to be measured, and adjust the wedge pair to control the energy ratio of the combined fundamental frequency beam to the beam to be measured to be between 1:100 and 1:1000;

[0016] Step 2: by adjusting the delay line, the combined light beam passes through the transient grating crystal to generate signal light of different intensities, the signal light intensity data is obtained by measuring with the detector, and a curve of the intensity of the signal light changing with the delay line modulation is drawn;

[0017] Step three, after Fourier transforming the modulation change curve, the spectrum, pulse width and phase information of the laser to be measured are obtained.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The ultrashort pulse measurement device of the present invention is provided with a beam splitter, which divides the laser to be measured into a fundamental frequency beam and a beam to be measured, and then combines the beams through a wedge and adjusts the intensity ratio of the fundamental frequency beam and the beam to be measured in the combined beam, so as to measure the intensity of the signal light generated by the combined beam. The detector is simple and only needs to capture and measure the signal light intensity. The present invention obtains the signal light intensity under different delays by adjusting the delay line, and draws a curve of the signal light intensity changing with the delay line modulation. It does not require a complex iterative algorithm, and only needs a simple Fourier transform to obtain the spectrum, pulse width and phase information of the laser to be measured, and the measurement method is also simple.

[0020] 2. The present invention measures ultrashort pulses based on a transient grating modulation sampling method, and utilizes the characteristic that the signal light generated by the transient grating effect has the same wavelength as the femtosecond laser to be measured, so that ultrashort pulse lasers in the visible and near-infrared bands can be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural principle diagram of an embodiment of an ultrashort pulse measurement device based on transient grating modulation sampling of the present invention;

[0022] Figure 2 is a curve diagram of the signal light intensity measured by an embodiment of the present invention as a function of delay line modulation;

[0023] Figure 3 Yes Figure 2 The curve shown is a curve diagram of the femtosecond laser spectrum to be measured and the phase obtained after Fourier transformation (the solid line in the figure is the laser spectrum, and the dotted line is the phase);

[0024] Figure 4 Yes Figure 2 The pulse width curve of the laser to be measured is obtained after Fourier transformation of the curve shown;

[0025] Description of reference numerals:

[0026] 1- femtosecond laser, 2- beam splitter, 3- first reflector, 4- second reflector, 5- third reflector, 6- delay line, 7- wedge pair, 8- three-hole aperture, 9- focusing mirror, 10- transient grating crystal, 11- detector. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0028] The present invention provides an ultrashort pulse measurement device based on transient grating modulation sampling, such as Figure 1 As shown, it includes a pair of wedges 7, a three-hole aperture 8, a focusing mirror 9, a transient grating crystal 10 and a detector 11, as well as a beam splitter 2, a first reflector 3 and a delay line 6; the ratio of reflected light to transmitted light of the beam splitter 2 is 1:1, and the reflected and transmitted energies are consistent. The beam splitter 2 is located on the outgoing light path of the femtosecond laser to be measured generated by the femtosecond laser 1, and is used to split the outgoing light of the femtosecond laser to be measured into a fundamental frequency beam and a beam to be measured.

[0029] The first reflector 3 and the delay line 6 are respectively located on the reflection light path and the transmission light path of the beam splitter 2, and are used to reflect the fundamental frequency light beam and the light beam to be measured; the delay line 6 includes a piezoelectric ceramic, and a second reflector 4 and a third reflector 5 arranged on the piezoelectric ceramic along the light path; the first reflector 3, the second reflector 4 and the third reflector 5 are high-reflection mirrors with a reflectivity greater than 99%.

[0030] The wedge pair 7 is located at the intersection of the reflection light path of the first reflector 3 and the delay line 6, and is used to combine the fundamental frequency light beam and the light beam to be measured. The wedge pair is used to compensate for the dispersion introduced by the beam splitter 2. At the same time, the energy ratio of the fundamental frequency light beam to the light beam to be measured can be adjusted by adjusting the angle of the beam combination, so that the energy ratio of the fundamental frequency light beam to the light beam to be measured is between 1:1000 and 1:100. The combined light beam is divided into three beams of laser light with consistent parameters through a three-hole aperture 8, and the connection line of the three holes of the three-hole aperture 8 is an isosceles right triangle; the three beams of laser light with consistent parameters are focused into a transient grating crystal 10 through a focusing mirror 9 to generate signal light of a transient grating; the focusing mirror 9 is a concave silver mirror with a focal length of 100 mm. The transient grating crystal 10 in this embodiment is amorphous fused quartz with a thickness of 50 μm. Other third-order nonlinear crystals also have a transient grating effect and can produce the same effect.

[0031] The transient grating crystal 10 generates signal light, and the intensity of the signal light is measured by a detector 11 . The detector can be a silicon-based camera or a spectrometer, which has the same effect.

[0032] In combination with the specific embodiment, in the process of measuring femtosecond laser, by adjusting the delay line 6, the combined light beam finally passes through the transient grating crystal 10 to generate signal light of different intensities, and after being measured by the detector 11, the measurement results are used to draw the following diagram: Figure 2 The intensity of the signal light shown in FIG. 1 changes with the modulation of the delay line 6; the signal light generated by the transient grating effect has the same wavelength as the femtosecond laser to be measured. Figure 2After Fourier transformation, the curve shown can be obtained as follows Figure 3 The spectral curves and phase curves shown, as well as Figure 4 According to the pulse width curve shown in the figure, the wavelength range of the femtosecond laser to be tested is 0.75-0.85 μm, the phase is less than 20 rad, and the pulse width is 32 femtoseconds (fs).

[0033] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. An ultrashort pulse measurement device based on transient grating modulation sampling, characterized in that: It comprises a beam splitter (2), a first reflector (3), a delay line (6), and a pair of wedges (7), a three-aperture aperture (8), a focusing mirror (9), a transient grating crystal (10) and a detector (11) which are sequentially arranged along the optical path; The beam splitter (2) is located on the outgoing light path of the femtosecond laser to be measured, and is used to split the outgoing light of the femtosecond laser to be measured into a reflected fundamental frequency light beam and a transmitted light beam to be measured; The first reflector (3) and the delay line (6) are respectively located on the fundamental frequency light path and the light path to be measured of the beam splitter (2), and are used to reflect the fundamental frequency light beam and the light beam to be measured; The wedge pair (7) is located at the intersection of the reflection light path of the first reflector (3) and the delay line (6), and is used to combine the fundamental frequency light beam and the light beam to be measured, and the energy ratio of the fundamental frequency light beam to the light beam to be measured in the combined light beam is between 1:100 and 1:1000; the combined light beam is divided into three laser beams with the same parameters through a three-hole aperture (8), and is focused into a transient grating crystal (10) through a focusing lens (9) to generate signal light of the transient grating; the connecting line of the three holes of the three-hole aperture (8) forms an isosceles right triangle; The detector (11) is used to measure the signal light intensity of the transient grating.

2. The ultrashort pulse measurement device based on transient grating modulation sampling according to claim 1 is characterized in that: The transient grating crystal (10) is amorphous fused quartz and has a thickness of 50 μm.

3. The ultrashort pulse measurement device based on transient grating modulation sampling according to claim 2 is characterized in that: The ratio of the reflected light to the transmitted light of the beam splitter (2) is 1:1, and the reflected and transmitted energies are consistent.

4. The ultrashort pulse measurement device based on transient grating modulation sampling according to any one of claims 1 to 3, characterized in that: The delay line (6) comprises piezoelectric ceramics, and a second reflector (4) and a third reflector (5) arranged on the piezoelectric ceramics along an optical path.

5. The ultrashort pulse measurement device based on transient grating modulation sampling according to claim 4 is characterized in that: The first reflector (3), the second reflector (4) and the third reflector (5) are high-reflection mirrors with a reflectivity greater than 99%.

6. The ultrashort pulse measurement device based on transient grating modulation sampling according to claim 5, characterized in that: The focusing mirror (9) is a concave silver mirror with a focal length of 100 mm.

7. The ultrashort pulse measurement device based on transient grating modulation sampling according to claim 6 is characterized in that: The detector (11) is a silicon-based camera or a spectrometer.

8. A method for measuring ultrashort pulses based on transient grating modulation sampling, using the ultrashort pulse measurement device based on transient grating modulation sampling according to any one of claims 1 to 7, characterized in that: Step 1: Use a beam splitter (2) to split the laser into a fundamental frequency beam and a beam to be measured with equal energy, introduce the beam to be measured into a delay line (6), and after the fundamental frequency beam is reflected by a first reflector (3), use a wedge pair (7) to combine the fundamental frequency beam and the beam to be measured, and adjust the wedge pair (7) to control the energy ratio of the combined fundamental frequency beam to the beam to be measured to be between 1:100 and 1:1000; Step 2, by adjusting the delay line (6), the combined light beam passes through the transient grating crystal (10) to generate signal light of different intensities, the signal light intensity data is measured by the detector (11), and a curve of the intensity of the signal light changing with the modulation of the delay line (6) is drawn; Step three, after Fourier transforming the modulation change curve, the spectrum, pulse width and phase information of the femtosecond laser to be measured are obtained.

Images