阅读说明：本技术 一种激光脉冲时域展宽器及激光装置 (Laser pulse time domain stretcher and laser device ) 是由 谢晓华 吴朝辉 李云亭 吴光辉 陈乐� 岳超瑜 于 2020-04-23 设计创作，主要内容包括：本发明提供了一种激光脉冲时域展宽器,包括第一准直器、与第一准直器空间耦合对接的第二准直器、设于第一准直器和第二准直器之间的相位延迟器、一端与第二准直器连接且用于光束的脉冲展宽的时域展宽光纤以及与时域展宽光纤的远离第二准直器的一端连接且用于反射光束的法拉第旋转镜,相位延迟器用于使光束的相位延迟四分之一波长。与现有技术相比,一方面,本发明的激光脉冲时域展宽器可以在保持偏振态不变的情况下对光束进行时域展宽；另一方面,采用本发明的激光脉冲时域展宽器对光束进行时域展宽时,光束需要经过时域展宽光纤两次,因此在达到相同的时域展宽效果的前提下,本发明的时域展宽光纤更短,故可以有效降低成本。(The invention provides a laser pulse time domain stretcher which comprises a first collimator, a second collimator, a phase delayer, a time domain stretching optical fiber and a Faraday rotator mirror, wherein the second collimator is in coupling butt joint with the first collimator in a space mode, one end of the phase delayer is arranged between the first collimator and the second collimator, one end of the time domain stretching optical fiber is connected with the second collimator and is used for stretching pulses of light beams, one end of the Faraday rotator mirror is connected with one end, far away from the second collimator, of the time domain stretching optical fiber and is used for reflecting the light beams, and the phase delayer is used for delaying the phase of the light beams by one quarter wavelength. Compared with the prior art, on one hand, the laser pulse time domain stretcher can perform time domain stretching on a light beam under the condition of keeping the polarization state unchanged; on the other hand, when the laser pulse time domain stretcher is used for time domain stretching of a light beam, the light beam needs to pass through the time domain stretching optical fiber twice, so that the time domain stretching optical fiber is shorter on the premise of achieving the same time domain stretching effect, and the cost can be effectively reduced.)

1. A laser pulse time domain stretcher, comprising:

the phase delay assembly comprises a first collimator, a second collimator in space coupling butt joint with the first collimator, and a phase delay device arranged between the first collimator and the second collimator, wherein the phase delay device is used for delaying the phase of a light beam by a quarter wavelength;

one end of the time domain broadening optical fiber is connected with the second collimator and is used for pulse broadening of the light beam; and

the Faraday rotator mirror is connected with one end of the time domain broadening optical fiber, which is far away from the second collimator, and is used for reflecting the light beam;

when the laser pulse time domain stretcher works, an incident beam sequentially passes through the first collimator, the phase delayer and the second collimator and then reaches the time domain stretching optical fiber to perform first time domain stretching to obtain a first beam; the first light beam reaches the time domain broadening optical fiber after being reflected by the Faraday rotator and undergoes second time domain broadening to obtain a second light beam; and the second light beam sequentially passes through the second collimator, the phase retarder and the first collimator and then is emitted out, so that a third light beam is obtained.

2. The laser pulse time domain stretcher of claim 1 wherein a set of the phase delay elements is disposed in the laser pulse time domain stretcher, the laser pulse time domain stretcher further comprising a circulator having a first port for the incoming optical beam, a second port connected to an end of the first collimator distal from the phase delay elements, and a third port for the outgoing third optical beam.

3. The laser pulse time domain stretcher of claim 1 wherein two sets of the phase delay assemblies are provided in the laser pulse time domain stretcher, the laser pulse time domain stretcher further comprising a circulator having a first port connected to an end of the second collimator of one of the sets of the phase delay assemblies distal from the corresponding phase delay, a second port connected to an end of the time domain stretching fiber distal from the faraday rotator mirror, and a third port connected to an end of the second collimator of the other set of the phase delay assemblies distal from the corresponding phase delay.

4. The laser pulse time-domain stretcher of claim 1 wherein the optical axis of the phase retarder is 45 ° to the polarization direction of the incident beam.

5. The laser pulse time-domain stretcher of claim 1 wherein the phase retarder is rotatable in a direction perpendicular to an optical axis of the phase retarder.

6. The laser pulse time-domain stretcher of claim 1, wherein the time-domain stretching fiber is a passive non-polarization-maintaining fiber comprising a core, a cladding wrapped outside the core, and a coating coated outside the cladding.

7. The laser pulse time-domain stretcher of claim 6 wherein the core has a diameter in the range of 6 μm to 10 μm, the cladding has a diameter in the range of 100 μm to 150 μm, and the coating has a diameter in the range of 220 μm to 280 μm.

8. The laser pulse time-domain stretcher of any one of claims 1 to 7, wherein a pigtail is provided on the first collimator, the pigtail of the first collimator being a polarization maintaining fiber; the second collimator is provided with a tail fiber, and the tail fiber of the second collimator is a non-polarization-maintaining fiber.

9. The laser pulse time-domain stretcher of any one of claims 1 to 7, wherein the Faraday rotator mirror comprises a third collimator, a Faraday rotator, and a mirror arranged in that order along the optical path; alternatively, the first and second electrodes may be,

the Faraday rotator comprises an optical fiber type Faraday rotator and an optical fiber Bragg grating which are sequentially arranged along an optical path; alternatively, the first and second electrodes may be,

the Faraday rotator mirror comprises an optical fiber type Faraday rotator and an optical fiber Sagnac interferometer which are sequentially arranged along an optical path.

10. A laser device comprising the laser pulse time-domain stretcher of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of laser, and particularly relates to a laser pulse time domain stretcher and a laser device.

Background

Since the last 80 s, the Chirped Pulse Amplification (CPA) technology has gradually become an important means for obtaining high-power large-pulse energy output of fiber lasers. The CPA technology principle is that by using a dispersion technology (different wavelength speeds are different), laser pulses are firstly broadened in a time domain, then are amplified through a multi-stage pulse amplifier, and finally are compressed in the time domain, so that optical damage of ultrashort pulses in the amplification process can be avoided, and gain can be obtained more effectively. Therefore, in the application of the CPA technology, the broadening of the laser pulse in the time domain becomes a key step. Traditionally, chirped fiber grating or polarization maintaining fiber with a certain length is utilized to widen laser pulse in a time domain, and full fiber is realized, so that the structure is compact and the performance is stable.

However, chirped fiber grating stretchers suffer from large optical energy losses due to their mechanism of operation, and provide an amount of stretching that is proportional to the length of the grating, with higher costs associated with longer grating lengths. Once the chirped grating is written, the dispersion amount is fixed, and although the dispersion amount can be adjusted by changing temperature or stress, the adjustment range of the dispersion amount is limited. The pulse is widened by using a common polarization maintaining optical fiber (such as Nufern-PM980-XP), the energy loss is small, the dispersion amount is determined by the length of the optical fiber, and the adjustment flexibility is strong. The required length is from several tens of meters to several kilometers due to the small dispersion coefficient of the fiber itself, resulting in high cost.

Disclosure of Invention

An embodiment of the present invention provides a laser pulse time domain stretcher, so as to solve the technical problem that a chirped fiber grating stretcher in the prior art is expensive in cost.

In order to achieve the purpose, the invention adopts the technical scheme that: provided is a laser pulse time domain stretcher including:

the phase delay assembly comprises a first collimator, a second collimator in space coupling butt joint with the first collimator, and a phase delay device arranged between the first collimator and the second collimator, wherein the phase delay device is used for delaying the phase of a light beam by a quarter wavelength;

one end of the time domain broadening optical fiber is connected with the second collimator and is used for pulse broadening of the light beam; and

the Faraday rotator mirror is connected with one end of the time domain broadening optical fiber, which is far away from the second collimator, and is used for reflecting the light beam;

when the laser pulse time domain stretcher works, an incident beam sequentially passes through the first collimator, the phase delayer and the second collimator and then reaches the time domain stretching optical fiber to perform first time domain stretching to obtain a first beam; the first light beam reaches the time domain broadening optical fiber after being reflected by the Faraday rotator and undergoes second time domain broadening to obtain a second light beam; and the second light beam sequentially passes through the second collimator, the phase retarder and the first collimator and then is emitted out, so that a third light beam is obtained.

Optionally, a set of the phase delay components is disposed in the laser pulse time domain stretcher, and the laser pulse time domain stretcher further includes a circulator, where the circulator has a first port for the incident light beam to enter, a second port connected to an end of the first collimator far from the phase delay, and a third port for the third light beam to exit.

Optionally, two sets of the phase delay assemblies are disposed in the laser pulse time domain stretcher, the laser pulse time domain stretcher further includes a circulator, the circulator has a first port, a second port and a third port, the first port is connected to one end of the second collimator of one set of the phase delay assemblies, which is far away from the corresponding phase delay, the second port is connected to one end of the time domain stretching optical fiber, which is far away from the faraday rotator, and the third port is connected to one end of the second collimator of the other set of the phase delay assemblies, which is far away from the corresponding phase delay.

Optionally, the optical axis of the phase retarder is 45 ° to the polarization direction of the incident light beam.

Alternatively, the phase retarder may be rotatable in a direction perpendicular to an optical axis of the phase retarder.

Optionally, the time-domain broadening fiber is a passive non-polarization-maintaining fiber, and the passive non-polarization-maintaining fiber includes a fiber core, a cladding wrapped outside the fiber core, and a coating layer coated outside the cladding.

Optionally, the diameter of the core is in a range of 6 μm to 10 μm, the diameter of the cladding is in a range of 100 μm to 150 μm, and the diameter of the coating is in a range of 220 μm to 280 μm.

Optionally, a tail fiber is arranged on the first collimator, and the tail fiber of the first collimator is a polarization maintaining fiber; the second collimator is provided with a tail fiber, and the tail fiber of the second collimator is a non-polarization-maintaining fiber.

Optionally, the faraday rotator comprises a third collimator, a faraday rotator and a reflector which are sequentially arranged along the optical path; alternatively, the first and second electrodes may be,

the Faraday rotator comprises an optical fiber type Faraday rotator and an optical fiber Bragg grating which are sequentially arranged along an optical path; alternatively, the first and second electrodes may be,

the Faraday rotator mirror comprises an optical fiber type Faraday rotator and an optical fiber Sagnac interferometer which are sequentially arranged along an optical path.

It is another object of the present invention to provide a laser apparatus comprising a laser pulse time-domain stretcher as described above.

The invention provides a laser pulse time domain stretcher, which comprises a first collimator, a second collimator in spatial coupling butt joint with the first collimator, a phase delay device arranged between the first collimator and the second collimator, a time domain stretching optical fiber with one end connected with the second collimator and used for pulse stretching of a light beam, and a Faraday rotator mirror connected with one end of the time domain stretching optical fiber, which is far away from the second collimator and used for reflecting the light beam, wherein the phase delay device is used for delaying the phase of the light beam by a quarter wavelength; when the laser pulse time domain stretcher works, an incident beam sequentially passes through the first collimator, the phase delayer and the second collimator and then reaches the time domain stretching optical fiber to perform first time domain stretching to obtain a first beam; the first light beam reaches the time domain broadening optical fiber after being reflected by the Faraday rotator and is subjected to second time of time domain broadening to obtain a second light beam; the second light beam sequentially passes through the second collimator, the phase retarder and the first collimator and then is emitted out, and a third light beam is obtained. Compared with the prior art, on one hand, the laser pulse time domain stretcher can perform time domain stretching on a light beam under the condition of keeping the polarization state unchanged; on the other hand, when the laser pulse time domain stretcher is adopted to stretch the time domain of the light beam, the light beam needs to pass through the time domain stretching optical fiber twice, so that the time domain stretching optical fiber is shorter on the premise of achieving the same time domain stretching effect, and the cost can be effectively reduced; the time domain broadening fiber can be a single-mode passive non-polarization-maintaining fiber, is lower in cost and has great advantages compared with a polarization-maintaining fiber or a chirped grating scheme.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

Fig. 1 is a schematic structural diagram of a laser pulse time domain stretcher according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a laser pulse time domain stretcher according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a faraday rotator provided in an embodiment of the present invention.

Wherein, in the figures, the respective reference numerals:

100-phase delay elements; 110-a first collimator; 120-a second collimator; 130-a phase retarder; 200-time domain broadening fiber; 300-faraday rotator mirror; 310-a third collimator; 320-a faraday rotator; 330-a mirror; 340-a housing; 400-a circulator; 410-a first port; 420-a second port; 430-third port.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is 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 of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, as used herein, refer to an orientation or positional relationship indicated in the drawings, which is solely for the purpose of facilitating the description and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and is therefore not to be construed as limiting the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

Referring to fig. 1 and fig. 2, an embodiment of the invention provides a laser pulse temporal stretcher, including:

a phase delay assembly 100 including a first collimator 110, a second collimator 120 spatially coupled and interfaced with the first collimator 110, and a phase retarder 130 disposed between the first collimator 110 and the second collimator 120, the phase retarder 130 for delaying a phase of the light beam by a quarter wavelength;

a time domain broadening fiber 200 having one end connected to the second collimator 120 and used for pulse broadening of the light beam; and

a Faraday rotator mirror 300 connected to an end of the time domain broadening fiber 200 away from the second collimator 120 for reflecting the light beam;

when the laser pulse time domain stretcher works, an incident beam sequentially passes through the first collimator 110, the phase delayer 130 and the second collimator 120 and then reaches the time domain stretching optical fiber 200 to perform first time domain stretching to obtain a first beam; the first light beam is reflected by a Faraday rotator mirror 300 and then reaches the time domain broadening optical fiber 200, and the time domain broadening is carried out for the second time, so that a second light beam is obtained; the second light beam sequentially passes through the second collimator 120, the phase retarder 130 and the first collimator 110 and then is emitted out, so as to obtain a third light beam. The polarization direction of the incident beam and the polarization direction of the third beam form an included angle of 90 degrees. In this embodiment, the phase delay assembly 100 may be, but is not limited to, a quarter-wave plate.

It should be noted that the light beam is linearly polarized before entering the laser pulse time domain stretcher, and the light beam needs to sequentially pass through the first collimator 110, the phase retarder 130 and the second collimator 120 after entering the laser pulse time domain stretcher, at this time, the phase of the light beam is delayed by a quarter wavelength, that is, the light beam is converted into circularly polarized light or elliptically polarized light; in the process of carrying out first time domain broadening and second time domain broadening on the light beam, the light beam is also circularly polarized light or elliptically polarized light all the time; after the second time domain broadening, the light beam needs to pass through the second collimator 120, the phase retarder 130 and the first collimator 110 in sequence, at this time, the phase of the light beam is delayed by a quarter wavelength again, that is, the light beam is converted into linearly polarized light, and then, the light beam is output from the laser pulse time domain broadening device. Therefore, when the laser pulse time domain stretcher provided by the embodiment of the invention is used for time domain stretching of the light beam, the polarization state of the light beam cannot be changed.

Compared with the prior art, the laser pulse time domain stretcher provided by the embodiment of the invention at least has the following beneficial effects:

(1) the laser pulse time domain stretcher can be used for stretching the time domain of a light beam under the condition of keeping the polarization state unchanged;

(2) when the time domain broadening is performed on the light beam, the light beam needs to pass through the time domain broadening fiber 200 twice, so that on the premise of achieving the same time domain broadening effect, the time domain broadening fiber 200 of the embodiment of the invention is shorter, so that the cost can be effectively reduced, and the laser pulse time domain stretcher of the embodiment of the invention has low cost; in addition, the time-domain broadened optical fiber 200 may be a single-mode passive non-polarization-maintaining optical fiber, which is lower in cost and has a great advantage over a polarization-maintaining optical fiber or a chirped grating scheme.

(3) The dispersion of the laser pulse time domain stretcher of the embodiment of the invention is mainly determined by the length of the time domain stretched optical fiber 200, and the dispersion can be flexibly adjusted by adjusting the length of the time domain stretched optical fiber 200.

As an alternative embodiment of the present invention, as shown in fig. 1, a set of phase delay elements 100 is disposed in the laser pulse time domain stretcher, and the laser pulse time domain stretcher further includes a circulator 400, where the circulator 400 has a first port 410 for supplying an incident light beam, a second port 420 connected to an end of the first collimator 110 away from the phase delay 130, and a third port 430 for supplying a third light beam. In this embodiment, the optical transmission direction of circulator 400 is such that the light beam incident on first port 410 exits from second port 420 and the light beam incident on second port 420 exits from third port 430.

The working process of the laser pulse time domain stretcher shown in fig. 1 is as follows: an incident beam enters from a first port 410 of the circulator 400, then exits from a second port 420 of the circulator 400, and reaches the time domain broadening fiber 200 after sequentially passing through the first collimator 110, the phase retarder 130 and the second collimator 120, and performs first time domain broadening to obtain a first beam; the first light beam is reflected by a Faraday rotator mirror 300 and then reaches the time domain broadening optical fiber 200, and the time domain broadening is carried out for the second time, so that a second light beam is obtained; the second light beam sequentially passes through the second collimator 120, the phase retarder 130 and the first collimator 110 and then is emitted out, so as to obtain a third light beam; the third beam is incident from second port 420 of circulator 400 and exits from third port 430 of circulator 400.

Specifically, in the laser pulse time-domain stretcher shown in fig. 1, the first port 410, the second port 420, and the third port 430 of the circulator 400 are all provided with corresponding pigtails, wherein the pigtail of the first port 410, the pigtail of the second port 420, and the pigtail of the third port 430 are all polarization-maintaining fibers, which can ensure the polarization state of an incident light beam before time-domain stretching, and also ensure the polarization state of a third light beam emitted from the third port 430 of the circulator. Specifically, the pigtail of the first port 410, the pigtail of the second port 420, and the pigtail of the third port 430 each include a core and a cladding wrapped around the core, wherein the core has a diameter in a range of 6 μm to 10 μm, the cladding has a diameter in a range of 100 μm to 150 μm, for example, the core may have a diameter of 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, and the cladding may have a diameter of 125 μm. In particular, the slow axis direction of the pigtail of the first port 410 is perpendicular to the slow axis direction of the pigtail of the third port 430, which ensures that the light beam is transmitted along the same axis in the fiber before and after pulse spreading. It is understood that the diameters of the core and the cladding may be appropriately adjusted according to the choice of the actual conditions, and the present invention is not particularly limited thereto.

As another alternative embodiment of the present invention, as shown in fig. 2, two sets of phase delay assemblies 100 are disposed in the laser pulse time domain stretcher, the laser pulse time domain stretcher further includes a circulator 400, the circulator 400 has a first port 410, a second port 420 and a third port 430, the first port 410 is connected to one end of the second collimator 120 of one set of phase delay assemblies 100, which is far from the corresponding phase delay 130, the second port 420 is connected to one end of the time domain stretching optical fiber 200, which is far from the faraday rotator 300, and the third port 430 is connected to one end of the second collimator 120 of the other set of phase delay assemblies 100, which is far from the corresponding phase delay 130. In this embodiment, the optical transmission direction of circulator 400 is such that the light beam incident on first port 410 exits from second port 420 and the light beam incident on second port 420 exits from third port 430.

The working process of the laser pulse time domain stretcher shown in fig. 2 is as follows: an incident light beam sequentially passes through the first collimator 110, the phase retarder 130 and the second collimator 120 of the first set of phase delay elements 100, enters from the first port 410 of the circulator 400 and exits from the second port 420 of the circulator 400; then, the incident beam reaches the time domain broadening fiber 200 and carries out the first time of time domain broadening to obtain a first beam; the first light beam is reflected by a Faraday rotator mirror 300 and then reaches the time domain broadening optical fiber 200, and the time domain broadening is carried out for the second time, so that a second light beam is obtained; the second light beam enters from the second port 420 of the circulator 400 and exits from the third port 430 of the circulator 400, and then exits after passing through the second collimator 120, the phase retarder 130 and the first collimator 110 of the second set of phase delay element 100 in sequence, so as to obtain a third light beam.

Specifically, in the laser pulse time domain stretcher shown in fig. 2, the first port 410, the second port 420, and the third port 430 of the circulator 400 are all provided with corresponding pigtails, wherein the pigtail of the first port 410, the pigtail of the second port 420, and the pigtail of the third port 430 are all non-polarization-maintaining fibers. Specifically, the pigtail of the first port 410, the pigtail of the second port 420, and the pigtail of the third port 430 each include a core and a cladding wrapped around the core, wherein the core has a diameter in a range of 6 μm to 10 μm, the cladding has a diameter in a range of 100 μm to 150 μm, for example, the core may have a diameter of 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, and the cladding may have a diameter of 125 μm. In particular, the lengths of the tail fiber of the first port 410 and the tail fiber of the third port 430 of the circulator 400 are the same, so that the optical paths of the light beams transmitted back and forth in the non-polarization-maintaining fiber are the same, and the total phase shift difference of the two orthogonal polarization states of the light beams transmitted in the non-polarization-maintaining fiber is zero. It is understood that the diameters of the core and the cladding may be appropriately adjusted according to the choice of the actual conditions, and the present invention is not particularly limited thereto.

Specifically, in an embodiment of the present invention, as shown in fig. 1 and fig. 2, an optical axis of the phase retarder 130 and a polarization direction of an incident light beam form 45 °, the incident light beam sequentially passes through the first collimator 110, the phase retarder 130, and the second collimator 120, and then reaches the time domain broadening fiber 200, and performs a first time domain broadening to obtain a first light beam, in the above process, the incident light beam is linearly polarized light, and when the incident light beam passes through the phase retarder 130, the linearly polarized light is converted into circularly polarized light, because two orthogonal polarization components Ex and Ey of the circularly polarized light are equal, a total phase shift difference after two orthogonal polarization states of the incident light beam are transmitted back and forth in the fiber once is zero, and the polarization state of the light beam is insensitive to the environment. The first light beam is reflected by a Faraday rotator mirror 300 and then reaches the time domain broadening optical fiber 200, and the time domain broadening is carried out for the second time, so that a second light beam is obtained; the second light beam sequentially passes through the second collimator 120, the phase retarder 130 and the first collimator 110 and then is emitted out, so as to obtain a third light beam. In the above process, the second light beam is circularly polarized light, and when the second light beam passes through the phase retarder 130, the circularly polarized light is converted into linearly polarized light, so that the polarization state of the third light beam is the same as that of the incident light beam, and the polarization states before and after the broadening of the light beam pulse are kept unchanged.

Specifically, in one embodiment of the present invention, as shown in fig. 1 and 2, the phase retarder 130 can be rotated in a direction perpendicular to the optical axis of the phase retarder 130, and by rotating the phase retarder 130, the angle of the polarization direction of the incident light beam of the optical axis of the phase retarder 130 can be adjusted such that the optical axis of the phase retarder 130 is 45 ° to the polarization direction of the incident light beam.

Specifically, in an embodiment of the present invention, as shown in fig. 1 and fig. 2, the time-domain broadening fiber 200 may be a single-mode passive non-polarization-maintaining fiber, where the passive non-polarization-maintaining fiber includes a fiber core, a cladding layer wrapped outside the fiber core, and a coating layer coated outside the cladding layer, and the single-mode passive non-polarization-maintaining fiber is used as a medium for broadening optical pulses, so that the cost is lower, and the single-mode passive non-polarization-maintaining fiber has a great advantage over a polarization-maintaining fiber or a chirped grating scheme.

Alternatively, in the time-domain broadened optical fiber 200 of the embodiment of the present invention, the diameter of the core is in a range of 6 μm to 10 μm, the diameter of the cladding is in a range of 100 μm to 150 μm, and the diameter of the coating is in a range of 220 μm to 280 μm, for example, the diameter of the core may be 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, the diameter of the cladding may be 125 μm, and the diameter of the coating may be 250 μm. It is to be understood that the diameters of the core, the cladding and the coating layer may be appropriately adjusted according to the choice of the actual conditions, and the present invention is not particularly limited thereto.

Specifically, in an embodiment of the present invention, as shown in fig. 1 and fig. 2, a pigtail is disposed on an end of the first collimator 110 away from the corresponding quarter-wave plate, and the pigtail of the first collimator 110 is a polarization maintaining fiber; one end of the quarter-wave plate corresponding to the second collimator 120 is provided with a tail fiber, and the tail fiber of the second collimator 120 is a non-polarization-maintaining fiber, which can ensure that the polarization state of the incident beam is unchanged before entering the phase delay assembly 100 and the polarization state of the third beam emitted by the laser pulse time domain stretcher is also unchanged.

Specifically, in each set of phase delay assemblies 100, the first collimator 110 and the second collimator 120 are coaxially disposed, and the working distances and the spot sizes of the first collimator 110 and the second collimator 120 are equal, so that the coupling efficiency between the first collimator 110 and the second collimator 120 can be improved. In this embodiment, the coupling efficiency between the first collimator 110 and the second collimator 120 is equal to or greater than 95%.

Specifically, in an embodiment of the present invention, as shown in fig. 3, the faraday rotator 300 includes a third collimator 310, a faraday rotator 320, and a reflector 330, which are sequentially disposed along the optical path, and when the laser pulse time-domain stretcher according to the embodiment of the present invention is used with reference to fig. 1 to 3, first, an incident light beam sequentially passes through the first collimator 110, the phase retarder 130, and the second collimator 120, and then reaches the time-domain stretching optical fiber 200, and performs a first time of time-domain stretching to obtain a first light beam; then, the first light beam sequentially passes through the third collimator 310 and the faraday rotator 320 and is reflected by the reflector 330; then, the first light beam reflected by the mirror 330 reaches the time domain broadening fiber 200 and undergoes a second time of time domain broadening to obtain a second light beam; finally, the second light beam sequentially passes through the second collimator 120, the phase retarder 130 and the first collimator 110 and then is emitted out, so as to obtain a third light beam.

Further, as shown in fig. 3, in the faraday rotator 300 according to the embodiment of the present invention, the third collimator 310, the faraday rotator 320, and the reflecting mirror 330 may be integrally disposed, in which case, the faraday rotator 300 further includes a housing 340, and the third collimator 310, the faraday rotator 320, and the reflecting mirror 330 are integrally disposed inside the housing 340. In this embodiment, the housing 340 is a metal piece to better protect the third collimator 310, the Faraday rotator 320, and the mirror 330.

It is understood that, according to the choice of practical situation, the specific structure of the faraday rotator 300 may also be other structures including a faraday rotator, for example, the faraday rotator 300 includes a fiber faraday rotator and a fiber bragg grating arranged in sequence along the optical path, or the faraday rotator 300 includes a fiber faraday rotator and a fiber sagnac interferometer arranged in sequence along the optical path, and the present invention is not limited thereto.

Another embodiment of the present invention provides a laser apparatus, including the laser pulse time domain stretcher described above, and since the laser apparatus of the embodiment of the present invention includes the laser pulse time domain stretcher described above, all the beneficial effects brought by the technical solutions of the above embodiments are also achieved, and are not described in detail herein.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.