CN113517625A - Ultrafast laser - Google Patents
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- CN113517625A CN113517625A CN202010278600.XA CN202010278600A CN113517625A CN 113517625 A CN113517625 A CN 113517625A CN 202010278600 A CN202010278600 A CN 202010278600A CN 113517625 A CN113517625 A CN 113517625A
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- FRNOGLGSGLTDKL-UHFFFAOYSA-N thulium atom Chemical compound [Tm] FRNOGLGSGLTDKL-UHFFFAOYSA-N 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 description 2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
- H01S3/1106—Mode locking
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
- H01S3/06745—Tapering of the fibre, core or active region
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Abstract
The invention provides an ultrafast laser which comprises a nonlinear amplification ring mirror and a main oscillation cavity, wherein the nonlinear amplification ring mirror is connected with the main oscillation cavity through a coupler, the main oscillation cavity comprises a first gain optical fiber connected with the coupler, a beam combiner connected with the first gain optical fiber and a first pumping light source, the thin end and the thick end of the first gain optical fiber are respectively connected with the coupler and the beam combiner, a light beam emitted by the first pumping light source enters the first gain optical fiber after being reflected by the beam combiner, the nonlinear amplification ring mirror processes the light beam and outputs signal light, and the signal light sequentially passes through the first gain optical fiber and the beam combiner and then is output. The ultrafast laser of the invention can ensure the long-term stability of the product by adopting the nonlinear amplification ring mirror and the tapered optical fiber, and keep the single-mode characteristic to obtain high beam quality, thereby obtaining high-energy and high-power laser output.
Description
Technical Field
The invention belongs to the technical field of lasers, and particularly relates to an ultrafast laser.
Background
The pulse width of the ultrafast laser is in the ps or even fs level, and passive mode locking schemes are commonly used for the generation of the ultrafast laser, and generally, the passive mode locking schemes include a saturable absorber passive mode locking scheme (SESAM), graphene, topological insulator, black scale, etc.), a Nonlinear Polarization Rotation (NPR) scheme, a Nonlinear Amplified ring Mirror (NALM) scheme, and the like. Among them, the mode locking scheme based on the SESAM has low damage threshold value and can generate gradual permanent damage in long-term use. Therefore, this scheme is not suitable for generating high-power pulses with large energy and long-term reliability is difficult to guarantee. Based on the nonlinear polarization rotation passive mode locking scheme, the passive mode locking device is greatly influenced by the vibration of the external environment temperature, has poor stability and cannot output high power. Although the traditional nonlinear amplification ring mirror NALM scheme and the improved 8-shaped cavity and 9-shaped cavity schemes can realize stable work, the traditional nonlinear amplification ring mirror NALM scheme and the improved 8-shaped cavity and 9-shaped cavity schemes also cannot realize uJ (micro-focus) level and watt level high-power large-energy output.
Disclosure of Invention
An embodiment of the present invention provides an ultrafast laser, so as to solve a technical problem that a laser in the prior art is difficult to simultaneously achieve high stability and high average output power.
In order to achieve the purpose, the invention adopts the technical scheme that: providing an ultrafast laser, comprising a nonlinear amplification ring mirror and a main oscillation cavity, wherein the nonlinear amplification ring mirror and the main oscillation cavity are connected through a coupler, and the main oscillation cavity comprises a first gain fiber connected with the coupler, a beam combiner connected with the first gain fiber and a first pump light source used for inputting light beams to the first gain fiber;
the first gain fiber is a tapered fiber, the end with the smaller diameter of the first gain fiber is defined as a thin end, the end with the larger diameter of the first gain fiber is defined as a thick end, the thin end of the first gain fiber is connected with the coupler, and the thick end of the first gain fiber is connected with the beam combiner;
and the light beam emitted by the first pumping light source enters the first gain optical fiber after being reflected by the beam combiner, the nonlinear amplification ring mirror processes the light beam and outputs signal light, and the signal light is output after sequentially passing through the coupler, the first gain optical fiber and the beam combiner.
Optionally, the beam combiner includes a focusing lens and a dichroic mirror, and the light beam emitted by the first pump light source is reflected by the dichroic mirror after passing through the focusing lens, and then passes through the focusing lens and the first gain fiber in sequence.
Optionally, the dichroic mirror is configured to perform total reflection on a light beam with a wavelength range of 900nm to 1000nm, and perform partial reflection and partial transmission on a light beam with a wavelength range of 1020nm to 1100 nm; the central wavelength of the light beam emitted by the first pumping light source is 915-980 nm.
Optionally, the beam combiner further includes a first sleeve, a second sleeve, and an end cap, the second sleeve and the end cap are sequentially arranged along an axial direction of the second sleeve, the first sleeve is sleeved outside the second sleeve and the end cap, the second sleeve is sleeved outside the focusing lens and the dichroic mirror, the dichroic mirror is disposed on one side of the focusing lens far away from the end cap, and a thick end of the first gain fiber is connected to the end cap.
Optionally, the ultrafast laser includes a pump fiber having two ends respectively connected to the end cap and the first pump light source, and a light beam emitted by the first pump light source is input to the beam combiner after passing through the pump fiber and is reflected by the beam combiner.
Optionally, the first gain fiber includes a core and an outer cladding layer wrapped around the core, the first gain fiber includes a first segment, and a diameter variation formula of the outer cladding layer of the first segment is as follows:
wherein D isz1Is the diameter of the outer cladding of the first section in millimeters; a is a variable coefficient of shape, DL1And D0The diameter of the thick end and the diameter of the thin end of the outer cladding of the first section are respectively, and the unit is millimeter; l is1Is the length of the outer cladding of the first section in meters; z is a radical of1Is the distance in meters of the corresponding position from the thin end of the outer cladding of the first section.
Optionally, the first gain fiber further comprises a second section smoothly connected to the first section, and the diameter variation formula of the outer cladding of the second section is as follows:
wherein D isz2Is the diameter of the outer cladding of the second section in millimeters; dL2The diameter of the thick end of the outer cladding of the second section is millimeter; l is2Is the length of the outer cladding of the second section in meters; z is a radical of2Is the distance in meters between the corresponding position and the thin end of the outer cladding of the second section.
Optionally, a has a value range of 0-2, and D0The value range of (A) is 0.07 mm-0.1 mm, DL1The value range of (A) is 0.28 mm-0.3 mm, DL2The value range of (A) is 0.38-0.4 mm, L is not less than 1.5 m1+L2Less than or equal to 3 meters.
Optionally, the coupling ratio of the coupler ranges from 10:90 to 90: 10.
Optionally, one side of the coupler is provided with a first port and a second port, and the other side of the coupler is provided with a third port and a fourth port; the nonlinear amplification ring mirror comprises a second pumping light source, a wavelength division multiplexer and a second gain optical fiber, the wavelength division multiplexer is connected to a third port of the coupler, two ends of the second gain optical fiber are respectively connected to a fourth port of the coupler and the wavelength division multiplexer, and the wavelength division multiplexer is used for coupling energy of the second pumping light source into the second gain optical fiber.
The ultrafast laser provided by the invention has the beneficial effects that: compared with the prior art, on one hand, the mode locking mechanism is provided by the nonlinear amplification ring mirror, and the nonlinear amplification ring mirror can bear high power, so that the long-term stability of a product is ensured; on the other hand, the tapered optical fiber is used as the first gain optical fiber, after the signal light is output by the nonlinear amplification annular mirror, the signal light is input from the thin end of the first gain optical fiber and then is output from the thick end of the first gain optical fiber, in the process, the single-mode characteristic can be kept, high beam quality can be obtained, meanwhile, the light spot is gradually enlarged, the nonlinear effect is greatly weakened, and accordingly high-energy and high-power ultrafast optical fiber laser output is obtained.
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 an ultrafast laser provided in an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a main oscillation cavity provided in an embodiment of the present invention;
fig. 3 is a graph illustrating a diameter variation of a first gain fiber according to an embodiment of the present invention.
Wherein, in the figures, the respective reference numerals:
1-a main oscillation cavity; 110-a first gain fiber; 120-a combiner; 121-a first sleeve; 122-an end cap; 123-a second sleeve; 124-a focusing lens; 125-dichroic mirror; 130-a first pump light source; 140-pump fibers; 2-a non-linear amplifying ring mirror; 210-a wavelength division multiplexer; 220-a second gain fiber; 230-a coupler; 231 — a first port; 232-a second port; 233-a third port; 234-a fourth port; 240-second pump light source.
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, an embodiment of the present invention provides an ultrafast laser, including a nonlinear amplification ring mirror 2 and a main oscillation cavity 1, where the nonlinear amplification ring mirror 2 is used to provide a mode locking mechanism and provide mode locking self-start for a system; the main oscillation cavity 1 is used for generating and amplifying laser pulses; the nonlinear amplification ring mirror 2 and the main oscillation cavity 1 are connected through the coupler 230, so that the nonlinear amplification ring mirror 2 and the main oscillation cavity 1 form a 9-shaped cavity, wherein the nonlinear amplification ring mirror 2 is the head of the 9-shaped cavity, and the main oscillation cavity 1 is the tail of the 9-shaped cavity;
the main oscillator cavity 1 includes a first gain fiber 110 connected to the coupler 230, a beam combiner 120 connected to the first gain fiber 110, and a first pump light source 130 for inputting a light beam toward the first gain fiber 110;
the first gain fiber 110 is a tapered fiber, the end with the smaller diameter of the first gain fiber 110 is defined as a thin end, the end with the larger diameter of the first gain fiber 110 is defined as a thick end, the thin end of the first gain fiber 110 is connected with the coupler 230, and the thick end of the first gain fiber 110 is connected with the beam combiner 120;
the light beam emitted by the first pump light source 130 is reflected by the beam combiner 120 and enters the first gain fiber 110, the nonlinear amplification ring mirror 2 processes the light beam and outputs signal light, and the signal light sequentially passes through the coupler 230, the first gain fiber 110 and the beam combiner 120 and is then output.
The ultrafast laser of the embodiment of the invention has the beneficial effects that: compared with the prior art, on one hand, the mode locking mechanism is provided by the nonlinear amplification ring mirror 2, so that soliton mode locking can be realized, the cost is reduced, and the nonlinear amplification ring mirror 2 can bear high power, so that the long-term stability of a product is ensured; on the other hand, a tapered optical fiber is adopted as the first gain optical fiber 110, after the nonlinear amplification ring mirror 2 outputs the signal light, the signal light is input from the thin end of the first gain optical fiber 110 and then output from the thick end of the first gain optical fiber 110, in the process, the signal light is subjected to adiabatic amplification, and the single-mode characteristic can be maintained to obtain a high-quality light beam; meanwhile, the light spot of the signal light can be gradually enlarged, the mode field area of the optical fiber is increased along with the gradual enlargement of the light spot, the maximum energy which can be carried by each laser pulse in the output pulse laser is improved by utilizing the inhibiting effect of the tapered optical fiber on the nonlinear effect (such as stimulated Raman scattering, stimulated Brillouin scattering and spontaneous radiation amplification), the contradiction between the large mode field area and the beam quality in the amplification stage of the high-power large-pulse-energy ultrafast optical fiber laser is solved, and the ultrashort pulse laser (such as femtosecond pulse laser and picosecond pulse laser) with high energy, high power (micro-focus stage and watt stage) and strong single mode is finally output.
Specifically, in an embodiment of the present invention, with reference to fig. 1 and fig. 2, the beam combiner 120 includes a focusing lens 124 and a dichroic mirror 125, a light beam emitted by the first pump light source 130 passes through the focusing lens 124 and is reflected by the dichroic mirror 125, then passes through the focusing lens 124 and the first gain fiber 110 in sequence, the nonlinear amplification ring mirror 2 processes the light beam and outputs a signal light, and the signal light passes through the first gain fiber 110, the focusing lens 124 and the dichroic mirror 125 in sequence and outputs an ultrashort pulse laser.
Specifically, the combiner 120 further includes a first sleeve 121, a second sleeve 123, and an end cap 122, the second sleeve 123 and the end cap 122 are sequentially disposed along an axial direction of the second sleeve 123, the first sleeve 121 is sleeved outside the second sleeve 123 and the end cap 122, and the end cap 122 specifically includes a quartz material, that is, the end cap 122 is a quartz material; the second sleeve 123 is sleeved outside the focusing lens 124 and the dichroic mirror 125, the dichroic mirror 125 is disposed on one side of the focusing lens 124 far away from the end cap 122, and the thick end of the first gain fiber 110 is connected to the end cap 122, so that the coupler 230, the first gain fiber 110 and the beam combiner 120 are sequentially connected.
As a preferred embodiment, end cap 122, focusing lens 124 and dichroic mirror 125 are coaxially disposed, and in this embodiment, first ferrule 121 is coaxially disposed with second ferrule 123 to ensure the coaxiality of end cap 122, focusing lens 124 and dichroic mirror 125.
Specifically, in an embodiment of the present invention, referring to fig. 1 and fig. 2, the ultrafast laser includes a pump fiber 140 having two ends respectively connected to the end cap 122 and the first pump light source 130, the pump fiber 140 is used for transmitting a light beam emitted by the first pump light source 130, the light beam emitted by the first pump light source 130 passes through the pump fiber 140, then is input to the beam combiner 120, and is reflected by the beam combiner 120, and the reflected light beam sequentially passes through the first gain fiber 110, so as to form a reverse pumping structure.
It can be understood that, according to the choice of practical situation, a forward pumping structure may also be formed, in which both ends of the pump fiber 140 are respectively connected to the thin end of the first gain fiber 110 and the first pump light source 130, and the light beam emitted by the first pump light source 130 directly enters and exits the first gain fiber 110 after passing through the pump fiber 140.
Optionally, the dichroic mirror 125 is configured to perform total reflection on the light beam with a wavelength range of 900nm to 1000nm, and perform partial reflection and partial transmission on the light beam with a wavelength range of 1020nm to 1100 nm; the central wavelength of the light beam emitted by the first pump light source 130 is 915nm to 980nm, so that the light beam emitted by the first pump light source 130 can be reflected to the first gain fiber 110 by the dichroic mirror 125, the nonlinear amplification ring mirror 2 processes the light beam and outputs signal light, and the signal light sequentially passes through the coupler 230, the first gain fiber 110, the focusing lens 124 and the dichroic mirror 125 and is output.
As a preferred embodiment, the first pump light source 130 is specifically a multimode pump light source with a locking wavelength with a central wavelength of 976 nm; the pump fiber 140 is a multimode pump fiber 140, and the pump fiber 140 may specifically adopt a multimode fiber of 105/125 or 200/220, so as to improve the conversion efficiency of the pump light.
Optionally, the thick end of the first gain fiber 110 is laser-welded to the end of the end cap 122 far from the focusing lens 124, the end of the pump fiber 140 far from the first pump light source 130 is laser-welded to the end of the end cap 122 far from the focusing lens 124, and the first gain fiber 110 and the pump fiber 140 are connected to the end cap 122 by laser welding, so that the number of optical meter interfaces on the optical paths of the signal light and the pump light can be reduced, the loss of the pump light and the signal light on the optical meter interfaces can be reduced, and the light intensity of the signal light output by the beam combiner 120 can be improved; in addition, the first gain fiber 110, the beam combiner 120, and the pump fiber 140 may be integrally disposed, so as to realize full optical fiber of the ultrafast laser.
Optionally, the first gain fiber 110 of the embodiment of the present invention is a polarization maintaining fiber, the first gain fiber 110 includes a core and an outer cladding layer wrapped outside the core, the core may be doped with rare earth ions such as ytterbium (Yb) ions, neodymium (Nd) ions, erbium (Er) ions, thulium (Tm) ions, and holmium (Ho) ions, and the core is preferably doped with ytterbium ions, so that the first gain fiber 110 becomes an active fiber. In this embodiment, the outer cladding may include two cladding layers wrapped around the core, or may include three cladding layers sequentially wrapped around the core, that is, the outer cladding layer may be a double cladding layer or a triple cladding layer, that is, the first gain fiber 110 is a double cladding layer or a triple cladding fiber.
Specifically, in one embodiment of the present invention, the first gain fiber 110 may adopt a segmented design, and the diameter of the core increases synchronously with the diameter of the outer cladding, and the diameter of the outer cladding is 8 to 12 times of the diameter of the core, and preferably, the diameter of the outer cladding is 10 times of the diameter of the core.
Specifically, the first gain fiber 110 may include a first segment and a second segment smoothly connected in sequence, wherein the diameter variation formula of the outer cladding corresponding to the first segment is:
in the formula (1), Dz1The diameter of the outer cladding of the first section in millimeters; a is a shape variable coefficient, and the value range of a is 0-2; dL1And D0The diameter of the thick end and the diameter of the thin end of the outer cladding of the first section are respectively, and the unit is millimeter; l is1The length of the outer cladding of the first section in meters; z is a radical of1Is the distance in meters between the corresponding position and the thin end of the outer cladding of the first section;
the variation formula of the outer cladding diameter corresponding to the second section is as follows:
in the formula (2), Dz2The diameter of the outer cladding of the second section is in millimeters; dL2The diameter of the thick end of the outer cladding layer of the second section is millimeter; l is2The length of the outer cladding of the second section is meter; z is a radical of2Is the distance in meters of the corresponding position from the thin end of the outer cladding of the second section. In this embodiment, sinceThe first and second sections are joined smoothly so that the butt diameter of the overwrap of the first section is equal to the butt diameter of the overwrap of the second section.
Optionally, the diameter of the thin end of the core ranges from 0.007 mm to 0.01 mm, and the diameter of the thick end of the core ranges from 0.038 mm to 0.04 mm; the diameter of the thin end of the outer cladding is in the range of 0.07 mm to 0.1 mm, D0The value range of (A) is 0.07 mm-0.1 mm; dL1The value range of (A) is 0.28 mm-0.3 mm; the diameter of the butt of the outer cladding is in the range of 0.38 mm to 0.4 mm, DL2The value range of (A) is 0.38 mm-0.4 mm; the length of the first gain optical fiber is 1.5-3 m, namely L is more than or equal to 1.5 m1+L2Less than or equal to 3 meters.
As an alternative, as shown in FIG. 3, a is 0.1 and D is0Is 0.075 mm, DL1Is 0.3 mm, DL2Is 0.4 mm, L1Is 1 m, L2The diameter variation formula of the outer cladding corresponding to the first section can be obtained by substituting the data into the formula (1) and the formula (2) respectively, wherein the diameter variation formula is 0.8 m:
the formula for the diameter variation of the outer cladding corresponding to the second section:
in this embodiment, the diameter of the thin end of the core is 0.0075 mm, the diameter of the thick end is 0.04 mm, the diameter of the thin end of the outer cladding is 0.075 mm, and the diameter of the thin end of the outer cladding is 0.4 mm; the length of the first gain optical fiber is 1.8 meters, and under the structure, single pulse energy with the pulse width of 10ps and more than 10 muJ can be obtained.
It should be noted that in the ultrafast laser according to the embodiment of the present invention, the thin end of the first gain fiber 110 may be pulled to the size of the common fiber, so as to ensure the single-mode transmission and facilitate the fusion with the common fiber, thereby implementing an all-fiber system and improving the stability and consistency of the product.
Specifically, in one embodiment of the present invention, as shown in fig. 1, the coupler 230 may be specifically a 2 × 2 polarization maintaining coupler 230, and a birefringent crystal is disposed inside the polarization maintaining coupler 230, so that the laser pulse transmits linearly polarized light in the system. A first port 231 and a second port 232 are arranged on one side of the coupler 230, and a third port 233 and a fourth port 234 are arranged on the other side; the thin end of the first gain fiber 110 is connected to the first port 231, the nonlinear amplification ring mirror 2 includes a second pump light source 240, a wavelength division multiplexer 210 and a second gain fiber 220, the wavelength division multiplexer 210 is connected to the third port 233 of the coupler 230, two ends of the second gain fiber 220 are respectively connected to the fourth port 234 of the coupler 230 and the wavelength division multiplexer 210, and the wavelength division multiplexer 210 is configured to couple energy of the second pump light source 240 into the second gain fiber 220. In this embodiment, in order to prevent the return light from interfering with the system, the end face of the pigtail connected to the second port 232 may be cut at an angle of 8 °, and of course, a PD detector for monitoring the performance of the system may be connected to the second port 232 or other amplification system may be connected to the second port 232 according to the choice of the actual situation.
Optionally, the second gain fiber 220 according to the embodiment of the present invention is a polarization maintaining fiber, the second gain fiber 220 includes a core and an outer cladding layer wrapped outside the core, and the core may be doped with rare earth ions such as ytterbium (Yb) ions, neodymium (Nd) ions, erbium (Er) ions, thulium (Tm) ions, and holmium (Ho) ions, so that the second gain fiber 220 becomes an active fiber. In this embodiment, the outer cladding may include a cladding layer surrounding the core, or may include two cladding layers sequentially surrounding the core, and the invention is not limited thereto.
As an alternative implementation manner, in the second gain fiber 220 according to the embodiment of the present invention, in order to maintain the single mode characteristic, the diameter of the core is in a range of 0.006 mm to 0.01 mm, the diameter of the outer cladding is in a range of 0.12 mm to 0.13 mm, and the length of the second gain fiber 220 is in a range of 0.3 m to 1.5 m. For example, in the second gain fiber 220 according to the embodiment of the present invention, the core is doped with ytterbium ions, the diameter of the core is 0.006 mm, the diameter of the outer cladding is 0.125 mm, and the length of the second gain fiber 220 is 1 m.
Optionally, the coupling ratio of the coupler 230 is in a range of 10:90 to 90:10, for example, the coupling ratio may be 50:50, 60: 40 or 80:20, and the coupling ratio can be adjusted appropriately according to the choice of the actual situation, and the invention is not limited thereto.
In the ultrafast laser of the embodiment of the present invention, the coupler 230 splits the incident light into two beams of light clockwise and counterclockwise according to the coupling ratio and transmits the two beams of light in the loop, and the second gain fiber 220 is close to the coupler 230, so that the clockwise optical path is amplified when entering the nonlinear amplification loop mirror 2, and the counterclockwise optical path is amplified before leaving the nonlinear amplification loop mirror 2, so that the two beams of light obtain different nonlinear phase shifts after going back and forth once in the nonlinear amplification loop mirror 2. The nonlinear phase shift is related to the light intensity, the stronger the light intensity, the larger the accumulated phase shift difference, the two beams meet at the coupler 230 and generate coherent superposition after going back and forth once, when the position phase shift difference with high intensity in the middle of the pulse is equal to pi, the transmittance of the light is 1, and the two sides of the pulse are weak in intensity, so the transmittance is low, in the running process of the laser, the central energy of the pulse is continuously amplified, the energy of the two sides of the pulse is continuously inhibited, and after multiple cycles, stable ultrashort pulse is finally formed and input into the first gain fiber 110.
In a preferred embodiment of the present invention, in order to reduce the difficulty of mode locking and improve the self-starting capability of mode locking of the system, sufficient nonlinear phase shift can be accumulated quickly by increasing the coupling ratio, for example, the coupling ratio of the coupler 230 can be designed to be 80:20 to reduce the difficulty of mode locking. It is understood that, according to the choice of actual conditions, other ways to reduce the difficulty of mode locking may be adopted, for example, the length of the second gain fiber 220 in the nonlinear amplification ring mirror 2 may be increased, or a non-reciprocal phase shifter for actively providing a certain initial phase shift difference may be added to the nonlinear amplification ring mirror 2, and the invention is not limited thereto.
Compared with the existing laser, the ultrafast laser provided by the embodiment of the invention has the characteristics of high energy output, small nonlinear effect and good single-mode beam quality, the first gain fiber 110 has the advantage of a double-clad fiber with a large mode field area, the first gain fiber 110 and a common fiber can be directly welded to form a light path, the defects of complexity, instability and the like of a solid amplifier are overcome, the advantage of full-fiber integration of a high-power ultrashort pulse laser is kept, and the scheme has the advantages of low cost, good reliability and easiness in mass production, and is beneficial to promoting the commercialization of the high-power ultrashort pulse laser.
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.
Claims (10)
1. An ultrafast laser, comprising a nonlinear amplification ring mirror and a main oscillation cavity, wherein the nonlinear amplification ring mirror and the main oscillation cavity are connected through a coupler, and the main oscillation cavity comprises a first gain fiber connected with the coupler, a beam combiner connected with the first gain fiber and a first pumping light source for inputting light beams to the first gain fiber;
the first gain fiber is a tapered fiber, the end with the smaller diameter of the first gain fiber is defined as a thin end, the end with the larger diameter of the first gain fiber is defined as a thick end, the thin end of the first gain fiber is connected with the coupler, and the thick end of the first gain fiber is connected with the beam combiner;
and the light beam emitted by the first pumping light source enters the first gain optical fiber after being reflected by the beam combiner, the nonlinear amplification ring mirror processes the light beam and outputs signal light, and the signal light is output after sequentially passing through the coupler, the first gain optical fiber and the beam combiner.
2. The ultrafast laser of claim 1, wherein the beam combiner comprises a focusing lens and a dichroic mirror, and the light beam emitted from the first pump light source is transmitted through the focusing lens, reflected by the dichroic mirror, and then sequentially passes through the focusing lens and the first gain fiber.
3. The ultrafast laser of claim 2, wherein the dichroic mirror is for total reflection of a light beam having a wavelength ranging from 900nm to 1000nm, partial reflection and partial transmission of a light beam having a wavelength ranging from 1020nm to 1100 nm; the central wavelength of the light beam emitted by the first pumping light source is 915-980 nm.
4. The ultrafast laser as claimed in claim 2, wherein the beam combiner further comprises a first sleeve, a second sleeve and an end cap, the second sleeve and the end cap are sequentially disposed along an axial direction of the second sleeve, the first sleeve is sleeved outside the second sleeve and the end cap, the second sleeve is sleeved outside the focusing lens and the dichroic mirror, the dichroic mirror is disposed on a side of the focusing lens away from the end cap, and a thick end of the first gain fiber is connected to the end cap.
5. The ultrafast laser as claimed in claim 4, wherein the ultrafast laser includes a pump fiber having two ends respectively connected to the end cap and the first pump light source, and a light beam emitted from the first pump light source is input to the beam combiner after passing through the pump fiber and reflected by the beam combiner.
6. The ultrafast laser of claim 1, wherein the first gain fiber comprises a core and an outer cladding surrounding the core, the first gain fiber comprising a first section, the outer cladding of the first section having a diameter variation formula of:
wherein D isz1Is the diameter of the outer cladding of the first section in millimeters;a is a variable coefficient of shape, DL1And D0The diameter of the thick end and the diameter of the thin end of the outer cladding of the first section are respectively, and the unit is millimeter; l is1Is the length of the outer cladding of the first section in meters; z is a radical of1Is the distance in meters of the corresponding position from the thin end of the outer cladding of the first section.
7. The ultrafast laser of claim 6, wherein the first gain fiber further comprises a second segment smoothly connected to the first segment, a diameter variation formula of an outer cladding of the second segment being:
wherein D isz2Is the diameter of the outer cladding of the second section in millimeters; dL2The diameter of the thick end of the outer cladding of the second section is millimeter; l is2Is the length of the outer cladding of the second section in meters; z is a radical of2Is the distance in meters between the corresponding position and the thin end of the outer cladding of the second section.
8. The ultrafast laser of claim 7, wherein a has a value in the range of 0 to 2, D0The value range of (A) is 0.07 mm-0.1 mm, DL1The value range of (A) is 0.28 mm-0.3 mm, DL2The value range of (A) is 0.38-0.4 mm, L is not less than 1.5 m1+L2Less than or equal to 3 meters.
9. The ultrafast laser as claimed in any one of claims 1 to 8, wherein the coupler has a coupling ratio in a range of 10:90 to 90: 10.
10. The ultrafast laser as claimed in any one of claims 1 to 8, wherein the coupler has a first port and a second port on one side and a third port and a fourth port on the other side; the nonlinear amplification ring mirror comprises a second pumping light source, a wavelength division multiplexer and a second gain optical fiber, the wavelength division multiplexer is connected to a third port of the coupler, two ends of the second gain optical fiber are respectively connected to a fourth port of the coupler and the wavelength division multiplexer, and the wavelength division multiplexer is used for coupling energy of the second pumping light source into the second gain optical fiber.
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| CN114605078A (en) * | 2022-03-02 | 2022-06-10 | 哈尔滨工程大学 | Based on Ho3+/Pr3+Co-doped ZBYA glass fiber and laser thereof |
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