Ultra-short pulse dynamic regulation and control device and method based on double acousto-optic deflectors

Abstract

The invention discloses an ultrashort pulse dynamic regulation and control device and method based on double acousto-optic deflectors, and belongs to the technical field related to laser. The device comprises an acousto-optic deflector group and a 4f optical system, the 4f optical system is formed by biconvex lenses with two times of focal length, and the optical axis is parallel to the horizontal plane; the 4f optical system changes the positive and negative of the symbols of acousto-optic effect group delay dispersion and improves the range of group delay dispersion; the acousto-optic deflector group is composed of two acousto-optic deflectors which are arranged in parallel and in opposite directions, and the two acousto-optic deflectors are located on the two sides of the 4f optical system respectively and are both perpendicular to the optical axis. First polarized light of an input light beam is converted into second polarized light through the first acousto-optic deflector, the second polarized light is converted into first polarized parallel light beams through the 4f optical system and the second acousto-optic deflector, and an output light beam is obtained. The acousto-optic deflector group provides continuously adjustable group delay dispersion and regulates and controls the pulse width of an output light beam. The device is low in cost, is simple to operate, and dynamically regulates and controls the pulse width of the output light beam.

Description

Technical Field

[0001] This invention belongs to the field of laser-related technology, and more specifically, relates to an ultrashort pulse dynamic control device and method based on dual acousto-optic deflectors. Background Technology

[0002] Ultrashort pulse lasers have extremely small pulse widths, even shorter than the characteristic times of many physical and chemical processes. Therefore, ultrashort pulse laser technology enables precise control of the interaction between laser and matter, playing a significant role in precision machining, biomedicine, basic scientific research, and the fabrication of micro and nanostructures. Furthermore, achieving flexible control over the pulse width of the beam, building upon the foundation of ultrashort pulses, will bring enormous benefits.

[0003] Currently, the most commonly used ultrashort pulse stretchers include the 4f type stretcher (Martinez type), the aberration-enhancing stretcher (Barty type), and the aberration-free stretcher (Offner type).

[0004] A common structure for Martinez-type stretchers is to place two gratings in opposite directions, with two focal lengths in the middle. f The converging lens with a spacing of 2 f The array is configured to form a telescope system, with the grating positioned between the front and rear focal planes of the telescope and the lenses. The pulse passes through the grating multiple times, generating sufficient positive group velocity dispersion to broaden the pulse. However, the use of lenses in the telescope system introduces aberrations that lead to higher-order dispersion.

[0005] The Barty-type beam stretcher telescope system consists of two identical cylindrical mirrors placed parallel to each other. This design effectively reduces spatial chirp due to its relatively large angle of incidence. The use of cylindrical mirrors allows the beam to travel off-axis, and the light returning from the roof mirror is spatially offset from the incoming light, allowing the light to pass through the stretcher multiple times in the vertical direction. The use of mirrors effectively eliminates spatial inhomogeneities in the beam. However, this structure of the stretcher is relatively complex, requires high adjustment precision, and is not easy to adjust.

[0006] The Offner-type expander consists of a telescope system with a concave mirror and a confocal convex mirror, and the ratio of the radii of curvature of the two spherical mirrors is 2:1. The Offner-type expander can completely eliminate aberrations and axial dispersion in the telescope system, but it requires very high precision in the spherical mirror and adjustment, making it inconvenient to adjust.

[0007] The parallel and symmetrical placement of dual acousto-optic deflectors can achieve active modulation of pulse width and is easy to operate. However, the group delay dispersion caused by the acousto-optic effect and the group delay dispersion caused by the acousto-optic crystal have opposite signs. Moreover, the group delay dispersion caused by the acousto-optic crystal is greater within a limited distance, and the pulse width modulation range is limited, which leads to the problem of limited applicability.

[0008] In summary, the Martinez-type, Barty-type, and Offner-type pulse stretchers currently used for pulse stretching have certain drawbacks, and can only passively modulate the pulse width, unable to achieve active control. Although dual acousto-optic deflectors can achieve active pulse width control, their applicability is limited. Therefore, it is necessary to overcome the many technical difficulties in existing pulse stretching technologies and research more applicable and flexible active pulse stretching technologies. Summary of the Invention

[0009] In view of the shortcomings of related technologies, the purpose of this invention is to provide an ultra-short pulse dynamic control device and method based on dual acousto-optic deflectors, which aims to solve the problems that commonly used pulse broadening technology is not flexible enough in modulating pulse width and has a limited scope of application.

[0010] To achieve the above objectives, in a first aspect, the present invention provides an ultrashort pulse dynamic control device based on dual acousto-optic deflectors, comprising: an acousto-optic deflector group and 4 f Optical system; The 4 f The optical system consists of biconvex lenses spaced twice the focal length apart, with the optical axis parallel to the horizontal plane; the 4 f Optical systems are used to change the sign of the group delay dispersion of the acousto-optic effect in order to improve the range of the group delay dispersion of the device. The acousto-optic deflector group consists of two parallel and oppositely placed acousto-optic deflectors, located respectively at the 4th... f The optical system is located on both sides, and both are perpendicular to the optical axis. The input beam is an ultrashort pulse parallel to the optical axis. After passing through a first acousto-optic deflector, the first polarized light is converted into second polarized light, which then passes through the 4... f The optical system and the second acousto-optic deflector then transform the beam into a parallel beam with the first polarization, resulting in the output beam; the acousto-optic deflector group is used to provide continuously adjustable group delay dispersion and control the pulse width of the output beam. The pulse width of the output beam is:

[0011] in, This is the driving frequency of the acousto-optic deflector. The pulse width of the input beam. For the group delay dispersion of the ultrashort pulse dynamic control device, LThe effective distance of the ultra-short pulse dynamic control device, , and These are the distances from the first and second acousto-optic deflectors to the adjacent lenses, respectively.

[0012] Optionally, the group delay dispersion is:

[0013] in, Group velocity dispersion of the acousto-optic crystal material for the acousto-optic deflector. and The thickness of the acousto-optic crystal in the acousto-optic deflector. The center wavelength of the incident laser. At the speed of light, The focal length of the lens. L The effective distance of the ultra-short pulse dynamic control device.

[0014] Optionally, when the group delay dispersion of the ultrashort pulse dynamic control device is positive, the ultrashort pulse dynamic control device is an ultrashort pulse stretcher; when the group delay dispersion of the ultrashort pulse dynamic control device is negative, the ultrashort pulse dynamic control device is an ultrashort pulse compressor.

[0015] Optional features also include roof mirrors; The ridge mirror is positioned on the optical axis and behind the second acousto-optic deflector. It is used to make the output beam return along a path parallel to the original optical path, doubling the group delay dispersion that the device can provide, and to compensate for spatial chirp so that the output light spot is a circular light spot.

[0016] Optionally, the 4 f In the optical system, both the first and second convex lenses are standard lenses, with the same material and focal length. After the above 4 f The relationship between the outgoing and incoming light in an optical system is as follows:

[0017] In the formula, The angle of the emitted light. The angle of the incident light.

[0018] In a second aspect, the present invention also provides a method for dynamic control of ultrashort pulses based on dual acousto-optic deflectors, applied to the ultrashort pulse dynamic control device based on dual acousto-optic deflectors as described in any one of the first aspects, comprising: Adjusting the distance between the acousto-optic deflector and the adjacent lens in the ultrashort pulse dynamic control device is used to control the effective distance of the ultrashort pulse dynamic control device, and select it as an ultrashort pulse stretcher or an ultrashort pulse compressor. The pulse width adjustment range of the output beam is calculated based on the pulse width of the input beam and the group delay dispersion range of the ultrashort pulse dynamic control device; the pulse width of the output beam is dynamically controlled within the pulse width adjustment range by adjusting the driving frequency of the acousto-optic deflector.

[0019] Optionally, it also includes: fine-tuning the relative position and angle between the first and second acousto-optic deflectors so that they remain perpendicular to the horizontal plane, are placed parallel and opposite to each other, and use the same driving frequency, so that the spatial dispersion generated by the second acousto-optic deflector compensates for the spatial dispersion generated by the first acousto-optic deflector, thereby achieving a parallel beam output.

[0020] Optionally, when the effective distance of the ultrashort pulse dynamic control device is fixed and not zero, the driving frequency of the acousto-optic deflector is adjusted to change the group delay dispersion. This allows for the control of the pulse width of the output beam; The change in pulse width of the output beam is:

[0021] in, The original driving frequency. The adjusted drive frequency, The pulse width of the input beam.

[0022] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: 1. This invention provides an ultrashort pulse dynamic control device based on dual acousto-optic deflectors, employing dual acousto-optic deflectors and 4... f The combination of optical systems enables dynamic control of the femtosecond laser pulse width. By changing the driving frequency of the acousto-optic deflector array, the group delay dispersion of the system is altered, allowing for active and continuous adjustment of the output laser pulse width while maintaining a parallel output beam; and through 4 f The optical system alters the sign of the group delay dispersion in the acousto-optic effect, increasing the range of group delay dispersion that the device can provide, thereby expanding the adjustment range of the laser pulse width. Using acousto-optic deflectors and lenses as core optical components, both commonly available commercial components, enhances practicality and eliminates the need for multiple systems or customized optical components, thus controlling system costs. This solves the problems of limited applicability and high customization costs associated with ultrashort pulse modulation devices.

[0023] 2. This invention provides an ultrashort pulse dynamic control device based on dual acousto-optic deflectors. Because this invention uses an acousto-optic deflector array to avoid spatial distortion of the light spot, the output laser pulse width is continuously adjustable while the output beam remains parallel, offering flexible adjustment and a wide range of applications. Once the positions of the acousto-optic deflectors and lens are determined, continuous adjustment of the pulse width can be achieved within the acousto-optic driving frequency range, provided the acousto-optic diffraction conditions are met. This solves the problems of limited applicability and high customization costs associated with ultrashort pulse control devices, while significantly reducing the difficulty of debugging. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of an ultrashort pulse dynamic control device based on dual acousto-optic deflectors provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another ultrashort pulse dynamic control device based on dual acousto-optic deflectors provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the single-pass ultrashort pulse dynamic control device for widening ultrashort pulses provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the two-way ultrashort pulse dynamic control device for widening ultrashort pulses provided in the embodiment of the present invention; wherein, (a) is a front view and (b) is a top view; Figure 5 This is a schematic diagram of the single-pass ultrashort pulse dynamic control device for compressing ultrashort pulses provided in an embodiment of the present invention; Figure 6 The 4 provided in the embodiments of the present invention f A schematic diagram of light deflection in an optical system; Figure 7 This is a spatial dispersion schematic diagram of a single acousto-optic deflector unit provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the time dispersion of a single acousto-optic deflector unit provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of the single-pass ultrashort pulse dynamic control device provided in an embodiment of the present invention to broaden ultrashort pulses; Figure 10 This is a schematic diagram of the two-way ultrashort pulse dynamic control device provided in an embodiment of the present invention to broaden ultrashort pulses; In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is a prism group, 1.1 and 1.2 are two convex lenses, 2 is an acousto-optic deflector group, 2.1 is the first acousto-optic deflector, 2.2 is the second acousto-optic deflector, 3 is a roof mirror, 4.1 is the first diffracted light, 4.2 is the second diffracted light, 5 is an elliptical light spot, 6.1 is the input pulse, and 6.2 is the output pulse. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0027] like Figure 1 As shown, the present invention provides an ultrashort pulse dynamic control device based on dual acousto-optic deflectors, comprising: 4 f Optical system 1 and acousto-optic deflector group 2; The 4 f The optical system consists of biconvex lenses spaced twice the focal length apart, with the optical axis parallel to the horizontal plane; the 4 f Optical systems are used to change the sign of the group delay dispersion of the acousto-optic effect in order to improve the range of the group delay dispersion of the device. The acousto-optic deflector group 2 consists of two parallel and oppositely placed acousto-optic deflectors, located respectively at the 4th... f Optical system 1 is located on both sides and is perpendicular to the optical axis; The input beam is an ultrashort pulse parallel to the optical axis. After passing through a first acousto-optic deflector, the first polarized light is converted into second polarized light, which then passes through the 4... f The optical system and the second acousto-optic deflector then transform the beam into a parallel beam with the first polarization, resulting in the output beam; the acousto-optic deflector group 2 is used to provide continuously adjustable group delay dispersion and control the pulse width of the output beam. The pulse width of the output beam is:

[0028] in, This is the driving frequency of the acousto-optic deflector. The pulse width of the input beam. For the group delay dispersion of the ultrashort pulse dynamic control device, L The effective distance of the ultra-short pulse dynamic control device, , and These are the distances from the first and second acousto-optic deflectors to the adjacent lenses, respectively.

[0029] In the embodiments of the invention, there are two cases. The first case involves the first polarized light being e-polarized light and the second polarized light being o-polarized light. Specifically, the input beam passes through a first acousto-optic deflector to convert the e-polarized light into o-polarized light, and then passes through 4... f The optical system and the second acousto-optic deflector convert the o-polarized light into an e-polarized parallel beam, resulting in the output beam. In the second case, the first polarized light is o-polarized, and the second polarized light is e-polarized. Specifically, the input beam is converted from o-polarized to e-polarized by the first acousto-optic deflector, and then... f The optical system and the second acousto-optic deflector then convert the e-polarized light into an o-polarized parallel beam, resulting in the output beam. In the subsequent description of this invention, the first scenario will be used as an example.

[0030] Using the laser beam emitted from the ultrashort pulse dynamic control device as a parallel beam constraint, the acousto-optic deflector group and 4 f The relative spatial positions of the optical systems are configured to control the horizontal incidence of the laser beam to 4 f Optical system 1 achieves spatial dispersion cancellation by finely adjusting the angles of the acousto-optic deflector and lens to the desired angles. Specifically, it includes: a reference... Figure 3 4 f Optical system 1 consists of a first convex lens 1.1 and a second convex lens 1.2 spaced twice the focal length apart. Acousto-optic deflector group 2 consists of a first acousto-optic deflector 2.1 and a second acousto-optic deflector 2.2. The two acousto-optic deflectors are placed parallel to each other and in opposite directions at position 4. f On both sides of the optical system 1; the second acousto-optic deflector 2.2 compensates for the spatial dispersion of the first acousto-optic deflector 2.1, ensuring that the output beam remains a parallel beam.

[0031] like Figure 3 As shown, 4 f Group delay dispersion provided by the inversion device of optical system 1 The symbol, together with the acousto-optic deflector group 2, provides continuously adjustable group time delay dispersion. When spatial dispersion cancellation is achieved by adjusting the spatial position and angle of the acousto-optic deflector group to be parallel and symmetrical, the shape of the light spot is observed. If the shape of the light spot does not change with the distance, it can be determined that spatial dispersion cancellation has been achieved.

[0032] In this embodiment of the invention, the ultrashort pulse dynamic control device based on dual acousto-optic deflectors is a single-pass ultrashort pulse dynamic control device; when the group delay dispersion of the ultrashort pulse dynamic control device is positive, the ultrashort pulse dynamic control device is an ultrashort pulse stretcher; when the group delay dispersion of the ultrashort pulse dynamic control device is negative, the ultrashort pulse dynamic control device is an ultrashort pulse compressor. In this embodiment, this can be achieved by adjusting the spatial position of the acousto-optic deflector group so that the distance between the acousto-optic deflector and the adjacent lens is a preset distance. The distances from the first acousto-optic deflector and the second acousto-optic deflector to the adjacent lens are respectively... and Effective distance of the ultrashort pulse dynamic control device ;like Figure 3 As shown, when the effective distance is positive, the group delay dispersion provided by the ultrashort pulse dynamic control device in this embodiment of the invention is positive, thus acting as an ultrashort pulse stretcher; after an ultrashort pulse laser beam with a circular spot passes through this device, its pulse width will be broadened, and the spot shape will become slightly elliptical; as... Figure 5 As shown, when the effective distance is negative and large enough, the group delay dispersion provided by the ultrashort pulse dynamic control device in this embodiment of the invention is negative, which is an ultrashort pulse compressor; after the ultrashort pulse laser beam with a circular spot passes through the device, its pulse width will be compressed and the spot shape will become slightly elliptical.

[0033] After the ultrashort pulse dynamic control device was built, 4 f The optical system provides a wide range of group delay dispersion for the device. The controller then changes the driving frequency of the acousto-optic deflectors to adjust the group delay dispersion provided by the acousto-optic deflector group, thereby achieving dynamic control of the pulse width of the output beam.

[0034] Based on the above embodiments, optionally, the 4 f The first convex lens 1.1 and the second convex lens 1.2 in the optical system are both standard lenses, with the same material and focal length; After the above 4 f The relationship between the outgoing and incoming light in an optical system is as follows:

[0035] In the formula, The angle of the emitted light. The angle of the incident light.

[0036] Lenses have a refractive effect on incident light, such as Figure 6 As shown, the beam has an incident angle of... Enter 4 f Optical systems, the beam will be Angle of incidence and the angle of departure They are equal in size but have opposite signs.

[0037] Furthermore, femtosecond lasers exhibit spatial dispersion when passing through an acousto-optic deflector, such as... Figure 7 As shown, taking the first acousto-optic deflector 2.1 as an example, light incident on the first acousto-optic deflector 2.1 is deflected by an angle. , can be represented as:

[0038] in, The sound field frequency of the acousto-optic deflector. For the speed of sound, λ is the wavelength.

[0039] Because femtosecond lasers have a certain bandwidth in their spectrum, the deflection angles of different spectral components are different, such as... Figure 7 The second diffracted light 4.2, with a longer wavelength, has a difference angle relative to the first diffracted light 4.1, with a shorter wavelength. , can be represented as:

[0040] in, The wavelength difference between the second diffracted light 4.2 and the first diffracted light 4.1.

[0041] Therefore, the spatial dispersion of the acousto-optic deflector can be expressed as:

[0042] Because the diffracted light deflection angles are different, the heights on the receiving surface are different. After the femtosecond laser passes through the acousto-optic deflector 2.1, it obtains an elliptical spot 5 on the receiving surface. Therefore, it is necessary to compensate for the spatial dispersion of the acousto-optic deflector so that the output beam of the deflector is a parallel beam and the spot size does not change with the distance.

[0043] refer to Figure 9 , due to 4 f The optical system changes the sign of the beam angle. When the second acousto-optic deflector 2.2 provides spatial dispersion of the same magnitude as the first acousto-optic deflector 2.1, it can compensate for the spatial dispersion of the first acousto-optic deflector 2.1.

[0044] Group delay dispersion introduced by acousto-optic deflectors Time-delay dispersion of acousto-optic crystal materials Group time delay dispersion of the acousto-optic effect The composition can be represented as:

[0045] like Figure 8As shown, after the ultrashort pulse passes through the first acousto-optic deflector 2.1, due to the different propagation speeds of each spectral component in the acousto-optic crystal, group velocity dispersion is introduced, causing the input pulse 6.1 to broaden into the output pulse 6.2.

[0046] Group velocity dispersion of acousto-optic crystals It can be represented as:

[0047] in, The center wavelength of the incident light At the speed of light, is the refractive index of the acousto-optic crystal.

[0048] The time-delay dispersion of the acousto-optic crystal material group caused by the acousto-optic deflector 2.1 This can be represented as the group velocity dispersion of an acousto-optic crystal. Product with the thickness of the acousto-optic crystal:

[0049] in, The thickness of the acousto-optic crystal.

[0050] Acousto-optic group velocity dispersion It can be represented as:

[0051] in, The center wavelength of the incident light At the speed of light, For driving frequency, The velocity of sound in the material.

[0052] Acousto-optic group delay dispersion and This can be represented as the acousto-optic group velocity dispersion. and effective transmission distance L The product of:

[0053] The group delay dispersion produced by the device is:

[0054] in, Group velocity dispersion of the acousto-optic crystal material for the acousto-optic deflector. and The thickness of the acousto-optic crystal in the acousto-optic deflector. The center wavelength of the incident laser. At the speed of light, The focal length of the lens. L The effective distance of the ultra-short pulse dynamic control device.

[0055] Group delay dispersion generated by acousto-optic deflectors Will affect pulse width τ This has an effect; therefore, the pulse width of the output beam is:

[0056] Based on the above embodiments, when the effective distance L is fixed and not zero, the driving frequency of the acousto-optic deflector is changed from... Change to At that time, by changing the group delay dispersion of the device This controls the pulse width, and the change in pulse width is:

[0057] In one specific embodiment, if a femtosecond laser with a center wavelength of 1034 nm and a pulse width of 212 fs is used, an acousto-optic deflector with a TeO2 crystal material and a crystal thickness of 20 mm is used with 4 f An optical system is used to construct a single-pass ultrashort pulse dynamic modulation device to control the pulse width. The group velocity dispersion of light at a wavelength of 1034 nm is observed in the acousto-optic crystal material TeO2. The speed of sound is 613 m / s; the driving frequency range is 65 MHz to 89 MHz. At an effective distance of 25 cm, the pulse width of the output laser can be dynamically adjusted from 305 fs to 368 fs; at an effective distance of 56 cm, the pulse width of the output laser can be dynamically adjusted from 410 fs to 543 fs.

[0058] This invention employs dual acousto-optic deflectors and 4 f The combination of optical systems enables dynamic control of the femtosecond laser pulse width. By changing the driving frequency of the acousto-optic deflector array, the group delay dispersion of the system is altered, allowing for active and continuous adjustment of the output laser pulse width while maintaining a parallel output beam; and through 4 f The optical system alters the sign of the group delay dispersion in the acousto-optic effect, increasing the range of group delay dispersion that the device can provide, thereby expanding the adjustment range of the laser pulse width. Using acousto-optic deflectors and lenses as core optical components, both commonly used commercial components, enhances practicality and eliminates the need for multiple systems or customized optical components, thus controlling system costs. This solves the problems of limited applicability and high customization costs in ultrashort pulse modulation devices. A low-cost, simple-to-operate, and wide-range pulse width modulation device has been achieved.

[0059] Example 2 like Figure 2 As shown, optionally, the ultrashort pulse dynamic control device also includes a roof mirror 3; The ridge mirror is positioned on the optical axis and behind the second acousto-optic deflector. It is used to make the output beam return along a path parallel to the original optical path, doubling the group delay dispersion that the device can provide, and to compensate for spatial chirp so that the output light spot is a circular light spot.

[0060] like Figure 10 As shown, the dual-path ultra-short pulse dynamic control device includes 4 f Optical system 1, acousto-optic deflector group 2, and roof mirror 3. An e-polarized femtosecond laser is perpendicularly incident on the first acousto-optic deflector 2.1, becoming o-polarized light, which then passes through 4... f After being deflected by the optical system, the light enters the second acousto-optic deflector 2.2 and becomes an e-polarized parallel beam. After passing through the roof mirror 3, the beam returns along a path parallel to the original optical path.

[0061] like Figure 4 As shown, the roof mirror 3 allows the beam output from the second acousto-optic deflector 2.2 to return along a path parallel to the original optical path, forming a two-way ultra-short pulse dynamic control device. This improves the modulation range and compensates for spatial chirp, resulting in a circular output beam. (Refer to...) Figure 4 From (a), we can see that the acousto-optic deflector and 4 f The optical system is spatially reversible; the beam can pass through the device twice to compensate for spatial chirp, eliminate distortion, and produce a circular beam shape. It also offers stronger pulse control over the beam. (Refer to...) Figure 4 As shown in (b), the roof mirror introduces beam translation, which allows the output beam and input beam to be separated in space.

[0062] The acousto-optic deflector array is used to provide continuously adjustable group delay dispersion, controlling the pulse width of ultrashort pulses; 4 f Optical system 1 is used to change the sign of the group time delay dispersion of the stretcher system; second acousto-optic deflector 2.2, which is parallel and symmetrical to the first acousto-optic deflector 2.1, is used to provide spatial dispersion compensation to ensure that the output beam is a parallel beam; the roof mirror is used to make the beam emitted from the second acousto-optic deflector return along a path parallel to the original optical path, compensate for spatial chirp, and keep the emitted light spot circular.

[0063] The laser beam is controlled to be horizontally incident on the first acousto-optic deflector 2.1. By changing the driving frequency of the acousto-optic deflector group 2, the pulse width of the femtosecond laser can be flexibly controlled.

[0064] 4 f Optical system 1, acousto-optic deflector group 2, and roof mirror 3 form a two-way ultrashort pulse dynamic control device, providing group time delay dispersion. It can be represented as:

[0065] in, For the material group velocity dispersion of the acousto-optic deflector, and The thickness of the acousto-optic crystals of the two acousto-optic deflectors. The center wavelength of the incident laser. The speed of sound in the acousto-optic deflector. At the speed of light, The focal length of the lens. and These are the distances from the first acousto-optic deflector 2.1 and the second acousto-optic deflector 2.2 to the adjacent lenses, respectively.

[0066] Compared to the single-path ultra-short pulse dynamic control device, the dual-path ultra-short pulse dynamic control device uses a roof mirror to make the beam emitted from the second acousto-optic deflector return along a path parallel to the original optical path, thereby compensating for spatial chirp and solving the problems of beam distortion and position shift at different driving frequencies.

[0067] In one specific embodiment, a femtosecond laser with a center wavelength of 1034 nm and a pulse width of 212 fs is used, along with an acousto-optic deflector assembly made of TeO2 crystal material with a crystal thickness of 20 mm, and 4... f An optical system and a roof mirror constitute a two-way ultrashort pulse dynamic control device to flexibly adjust the pulse width. The acousto-optic crystal material TeO2 exhibits group velocity dispersion of light at a wavelength of 1034 nm. The speed of sound is 613 m / s; the driving frequency range is 65 MHz to 89 MHz. At an effective distance of 25 cm, the pulse width of the output laser can be dynamically adjusted from 640 fs to 760 fs; at an effective distance of 56 cm, the pulse width of the output laser can be dynamically adjusted from 780 fs to 1050 fs.

[0068] Example 3 This invention also provides a method for dynamic control of ultrashort pulses based on dual acousto-optic deflectors, characterized in that it is applied to the ultrashort pulse dynamic control device based on dual acousto-optic deflectors as described in Embodiment 1 or Embodiment 2, comprising: Adjusting the distance between the acousto-optic deflector and the adjacent lens in the ultrashort pulse dynamic control device is used to control the effective distance of the ultrashort pulse dynamic control device, and select it as an ultrashort pulse stretcher or an ultrashort pulse compressor. The pulse width adjustment range of the output beam is calculated based on the pulse width of the input beam and the group delay dispersion range of the ultrashort pulse dynamic control device; the pulse width of the output beam is dynamically controlled within the pulse width adjustment range by adjusting the driving frequency of the acousto-optic deflector.

[0069] When the effective distance is positive, the ultrashort pulse dynamic control device provided in this embodiment of the invention is an ultrashort pulse stretcher; when the effective distance is negative and sufficiently large, the ultrashort pulse dynamic control device provided in this embodiment of the invention is an ultrashort pulse compressor.

[0070] Once the ultrashort pulse dynamic control device is built, the range of group delay dispersion values ​​it provides can be determined. Based on the pulse width of the input beam and the range of group delay dispersion values, the pulse width adjustment range of the output beam can be calculated. Within this pulse width adjustment range, the dynamic control of the pulse width of the output beam can be achieved by changing the driving frequency of the acousto-optic deflector.

[0071] Optionally, it also includes: fine-tuning the relative position and angle between the first and second acousto-optic deflectors so that they remain perpendicular to the horizontal plane, are placed parallel and opposite to each other, and use the same driving frequency, so that the spatial dispersion generated by the second acousto-optic deflector compensates for the spatial dispersion generated by the first acousto-optic deflector, thereby achieving a parallel beam output.

[0072] Optionally, when the effective distance of the ultrashort pulse dynamic control device is fixed and not zero, the driving frequency of the acousto-optic deflector is adjusted to change the group delay dispersion. This allows for the control of the pulse width of the output beam; The change in pulse width of the output beam is:

[0073] in, The original driving frequency. The adjusted drive frequency, The pulse width of the input beam.

[0074] This invention employs dual acousto-optic deflectors and dual convex lenses to construct an ultrashort pulse stretcher, which is simpler and more efficient than other pulse width control methods. By changing the driving frequency of the acousto-optic deflector group, the group delay dispersion of the system is altered. While ensuring the output beam is parallel, the pulse width of the output laser can be actively and continuously adjusted, offering flexible adjustment and a wide range of applications. This invention eliminates the need for multiple systems or customized optical components, thus controlling system costs. Furthermore, since this invention only requires meeting the acousto-optic diffraction conditions during debugging to achieve continuously adjustable pulse width within the acousto-optic driving frequency range, it eliminates the need for the fine-tuning required for traditional pulse stretchers, significantly reducing debugging difficulty.

[0075] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual acousto-optic deflector based ultra-short pulse dynamic steering device, characterized in that, The application comprises: Acousto-optic deflector set and 4 f Optical system; The 4 f The optical system is composed of two convex lenses with a distance of two focal lengths, and the optical axis is parallel to the horizontal plane; The 4 f The optical system is used for changing the positive and negative of the sign of the group time delay dispersion of the acousto-optic effect to improve the range of the group time delay dispersion of the device; The acousto-optic deflector group is composed of two acousto-optic deflectors placed in parallel and reversely, respectively located at the two sides of the 4 f optical system and both perpendicular to the optical axis; The input light beam is an ultrashort pulse parallel to the optical axis, and the first sound-light deflector converts the first polarized light into the second polarized light f The optical system and the second sound-light deflector convert the parallel light beam of the second polarized light into the parallel light beam of the first polarized light, and obtain an output light beam; and the sound-light deflector group is used for providing continuous adjustable group time delay dispersion, and regulating the pulse width of the output light beam. The pulse width of the output light beam is: wherein, is a driving frequency of the acousto-optic deflector, is a pulse width of the input light beam, is a group delay dispersion of the ultra-short pulse dynamic control device, L is an effective distance of the ultra-short pulse dynamic control device, , and are distances from the first acousto-optic deflector and the second acousto-optic deflector to the adjacent lens, respectively.

2. The ultra-short pulse dynamic tuning device of claim 1, wherein, The group delay dispersion is: wherein, group velocity dispersion of acousto-optic crystal material of acousto-optic deflector, and thickness of acousto-optic crystal of acousto-optic deflector, center wavelength of incident laser, speed of light, focal length of lens, L effective distance of ultra-short pulse dynamic regulation device.

3. The ultra-short pulse dynamic tuning device of claim 1, wherein, When the group delay dispersion of the ultra-short pulse dynamic regulation device is positive, the ultra-short pulse dynamic regulation device is an ultra-short pulse stretcher; when the group delay dispersion of the ultra-short pulse dynamic regulation device is negative, the ultra-short pulse dynamic regulation device is an ultra-short pulse compressor.

4. The ultra-short pulse dynamic tuning device of claim 1, wherein, The application further comprises a roof mirror; The roof mirror is arranged on the optical axis and behind the second acousto-optic deflector, and is used for returning the output light beam along a path parallel to the original light path, doubling the group delay dispersion provided by the device, and compensating for the spatial chirp, so that the output light spot is a circular light spot.

5. The ultra-short pulse dynamic tuning device of claim 1, wherein, The 4 f The first convex lens and the second convex lens in the optical system are standard lenses, and the materials and focal lengths are the same. After the 4 f The relationship of the exit light and the incident light of the optical system is: wherein is the angle of the outgoing light, is the angle of the incoming light.

6. A method for dynamic control of ultrashort pulses based on dual acousto-optic deflectors, characterized in that, The application is applied to the ultra-short pulse dynamic regulation device based on the double acousto-optic deflector according to any one of claims 1-5, and comprises: The distance between the acousto-optic deflector and the adjacent lens in the ultra-short pulse dynamic regulation device is adjusted to regulate the effective distance of the ultra-short pulse dynamic regulation device, and the effective distance is selected as an ultra-short pulse stretcher or an ultra-short pulse compressor; The pulse width adjustment range of the output light beam is calculated according to the pulse width of the input light beam and the range of the group delay dispersion of the ultra-short pulse dynamic regulation device; the driving frequency of the acousto-optic deflector is adjusted, so that the pulse width of the output light beam is dynamically regulated in the pulse width adjustment range.

7. The ultra-short pulse dynamic tuning method of claim 6, wherein, The application further comprises: the relative position and angle between the first acousto-optic deflector and the second acousto-optic deflector are finely adjusted, so that the first acousto-optic deflector and the second acousto-optic deflector are kept perpendicular to the horizontal plane, the first acousto-optic deflector and the second acousto-optic deflector are placed in parallel and reversely, the same driving frequency is used, the spatial dispersion generated by the second acousto-optic deflector compensates for the spatial dispersion generated by the first acousto-optic deflector, so that the output light beam is a parallel light beam.

8. The ultra-short pulse dynamic tuning method of claim 6, wherein, When the effective distance of the ultra-short pulse dynamic regulation device is fixed and not zero, the driving frequency of the acousto-optic deflector is adjusted to change the group delay dispersion , so as to regulate the pulse width of the output light beam The pulse width change amount of the output light beam is: wherein, is the drive frequency before adjustment, is the drive frequency after adjustment, is the pulse width of the input light beam.

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