CN217362137U - Laser amplifier, laser, and optical system - Google Patents

Abstract

The present application relates to a laser amplifier, a laser and an optical system, wherein the laser amplifier includes: a pump for outputting pump light; a gain fiber of the superior amplifier outputting signal light; the optical fiber combiner MPC is manufactured based on the output optical fiber of the pump and the gain optical fiber, and couples the pump light to the gain optical fiber for output; the input end of the collimation end cap is connected with the output section of the gain optical fiber, and the collimation end cap is used for collimating the pump light and the signal light and then outputting the collimated pump light and signal light; and the single crystal optical fiber is connected with the output end of the collimation end cap and is used for amplifying the signal light power under the excitation of the pump light. Through the application, the problems of complex structure, difficulty in assembly and adjustment and poor stability in the related technology are solved, and the laser amplifier is simple in structure, easy to assemble and adjust and high in stability.

Description

Laser amplifier, laser, and optical system

Technical Field

The present application relates to the field of fiber lasers, and in particular, to a laser amplifier, a laser, and an optical system based on single crystal fibers.

Background

The single crystal optical fiber is an optical fiber made of single crystal materials, has the physical and chemical properties of single crystal and the light guide property of fiber, simultaneously has the properties of single crystal and fiber, and belongs to the front edge crossing field of traditional solid state laser and fiber laser. The single crystal optical fiber is mainly made of single crystal materials with high gain, high thermal conductivity, high stability and excellent optical performance, the advantages of the high length-diameter ratio of the optical fiber materials and the advantages of optical waveguide conversion efficiency are integrated, and compared with the traditional glass optical fiber, the single crystal optical fiber has the advantages of high thermal conductivity, high laser damage threshold, small nonlinear effect and the like, so that the single crystal optical fiber is expected to generate higher-power output and transmit higher-energy laser.

Fig. 1 is a schematic diagram of a single crystal optical fiber optical path, and referring to fig. 1, the single crystal optical fiber is a gain medium with a length of tens of millimeters and a diameter of tens of micrometers to one millimeter. When the single crystal fiber is used, the signal light needs to pass through the center of the single crystal fiber, and the pump light needs to be totally reflected on the side interface of the single crystal fiber for multiple times.

A laser amplifier is a device that amplifies energy (power) of light using stimulated radiation of light. By using a laser amplifier, the quality of the laser (including pulse width, line width, polarization characteristics, etc.) can be maintained while achieving high laser energies or powers. Fig. 2 is a schematic view showing the principle of a laser amplifier based on a single crystal optical fiber according to the related art, and referring to fig. 2, a signal beam of the conventional laser amplifier based on a single crystal optical fiber needs to be adjusted in beam diameter and divergence angle through a first optical path, and to strictly control the propagation of the beam so that it passes through the center of the single crystal optical fiber. On the other hand, the pump light needs to pass through a second optical path for beam shaping, pass through a dichroic mirror, and then be focused into the single crystal fiber. That is, the signal beam and the pump beam of the conventional laser amplifier are shaped by two optical paths respectively.

In addition, the laser amplifier shown in fig. 2 also has the disadvantages of complex structure, high precision requirement, difficult installation and adjustment, and poor stability caused by a space optical structure, and has a large number of space optical paths, high requirement on environment, and high cleanliness.

Disclosure of Invention

The embodiment of the application provides a laser amplifier, a laser and an optical system based on a single crystal optical fiber, and aims to at least solve the problems of complex structure, difficulty in installation and adjustment and poor stability in the related technology.

In a first aspect, an embodiment of the present application provides a laser amplifier, including:

a pump for outputting pump light;

a gain fiber of the superior amplifier outputting signal light;

a fiber Combiner MPC (Multi-Mode Pump Combiner), the MPC being fabricated based on the output fiber of the Pump and the gain fiber, the MPC coupling the Pump light to the gain fiber for output; the optical fiber combiner MPC does not generate a welding point in the manufacturing and using processes, so that the damage risk is reduced, and the structure of the optical fiber combiner MPC does not contain passive signal fibers, so that the nonlinear effect generated by the transmission of signal light in the passive signal fibers is reduced.

The input end of the collimation end cap is connected with the output section of the gain optical fiber, and the collimation end cap is used for collimating the pump light and the signal light and then outputting the collimated pump light and signal light;

and the single crystal optical fiber is connected with the output end of the collimation end cap and is used for amplifying the signal light power under the excitation of the pump light.

In some embodiments, the cladding NA of the gain fiber is configured to be 1.2 to 2 times the core NA, and after the output signal light of the gain fiber is diverged, the mode field diameter of the pump light at the end cap is 1.2 to 2 times that of the signal light.

In some embodiments, due to chromatic aberration of the collimating end cap and a slight difference between the emission positions of the pump light and the signal light, the signal light output by the collimating end cap is in a collimated state, and the output pump light is in a collimated state with a divergence angle β, wherein the divergence angle β is smaller than a complementary angle of a total reflection critical angle of the inner surface of the single crystal fiber, so that the pump light is subjected to multiple total reflection at the side wall of the single crystal fiber.

In some of these embodiments, the single crystal optical fiber is directly connected to the output end of the collimating end cap.

In some embodiments, the collimating end cap is connected with the single crystal optical fiber through an optical cement process, and a coating, a glue and an air gap are avoided, so that the damage threshold of the embodiment of the application is higher, and the structure is more stable.

In some of these embodiments, the collimating end cap is a curved lens and/or a graded index lens.

In some of these embodiments, the substrate of the single crystal optical fiber is YAG (yttrium aluminum garnet crystal Y3Al5O12, YAG for short), YVO4 (yttrium vanadate), ceramic, and/or quartz; the doping element of the single crystal fiber is Yb (Ytterbium, Ytterbrium), Nd (Neodymium ), Er (Erbium, Erbium) and/or Tm (Thulium ).

In some of these embodiments, the pump is a semiconductor laser coupled through an optical fiber.

Based on the structure, the pump light output by the pump is combined with the signal light output by the gain fiber of the superior amplifier through the fiber combiner MPC, wherein, in the output section of the gain fiber, the pump power is absorbed by a part, the signal light power is amplified, and the amplification gain of the laser amplifier is improved; then, the signal light and the pump light are directly input into the single crystal fiber through the collimating end cap, the diameter of the collimated signal light is a proper size capable of completely passing through the single crystal fiber, the diameter of the collimated pump light is smaller than that of the single crystal fiber, but the collimated pump light has a larger divergence angle, the signal light and the pump light are shaped simultaneously through the collimating end cap, and the use requirements of the single crystal fiber are met; in the single crystal fiber, the pumping light is absorbed by the single crystal fiber through multiple total reflection, and the signal light passes through the center of the single crystal fiber and is amplified.

In a second aspect, embodiments of the present application provide a laser formed on the basis of a laser amplifier as described in the first aspect above.

In a third aspect, embodiments of the present application provide an optical system, which includes a laser light source, a first-stage laser amplifier, and the laser amplifier according to the first aspect.

Compared with the prior art, the laser amplifier, the laser and the optical system based on the single crystal optical fiber provided by the embodiment of the application realize the structural design of the laser amplifier which is simple in structure, easy to assemble and adjust and high in stability by fusing the gain optical fiber and the single crystal optical fiber, and realize the effects of reducing damage risks, reducing nonlinear effects, reducing requirements on environment and the like.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the application.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

fig. 1 is a schematic diagram of an optical path of a single crystal optical fiber according to the related art;

FIG. 2 is a schematic diagram of a principle of a single crystal fiber based laser amplifier according to the related art;

FIG. 3 is a schematic diagram of a laser amplifier according to an embodiment of the present application;

fig. 4 is a schematic diagram of a partial optical path of a laser amplifier according to an embodiment of the present application.

In the figure:

1. a gain fiber; 2. pumping; 3. an optical fiber combiner MPC; 4. an alignment end cap;

5. a single crystal optical fiber; 31. an output section; 11. a signal light; 21. a pump light.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments provided in the present application without any inventive step are within the scope of protection of the present application.

It is obvious that the drawings in the following description are only examples or embodiments of the present application, and that it is also possible for a person skilled in the art to apply the present application to other similar contexts on the basis of these drawings without inventive effort. Moreover, it should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.

Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of ordinary skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments without conflict.

Unless defined otherwise, technical or scientific terms referred to herein shall have the ordinary meaning as understood by those of ordinary skill in the art to which this application belongs. Reference to "a," "an," "the," and similar words throughout this application are not to be construed as limiting in number, and may refer to the singular or the plural. The present application is directed to the use of the terms "including," "comprising," "having," and any variations thereof, which are intended to cover non-exclusive inclusions; for example, a process, method, system, article, or apparatus that comprises a list of steps or modules (elements) is not limited to the listed steps or elements, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. Reference to "connected," "coupled," and the like in this application is not intended to be limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The term "plurality" as referred to herein means two or more. "and/or" describes an association relationship of associated objects, meaning that three relationships may exist, for example, "A and/or B" may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. Reference herein to the terms "first," "second," "third," and the like, are merely to distinguish similar objects and do not denote a particular ordering for the objects.

Pumping is a process of using light to raise (or "pump") electrons from a lower energy level in an atom or molecule to a higher energy level. Commonly used in laser construction, the laser medium is pumped to achieve population inversion.

Optical fiber numerical aperture NA: the optical fiber is an important parameter of a multimode optical fiber, is used for representing the light receiving capacity of the end face of the optical fiber and also influences the divergence angle of emergent light of the end face of the optical fiber, and the value of the optical fiber has the influence on the mode dispersion and the light receiving capacity of the optical fiber. Numerical aperture is expressed as

Wherein n is_core Representing the core refractive index, n_clad Indicating the cladding refractive index.

The laser amplifier is commonly used for high-power laser systems in the important technologies of controllable nuclear fusion, nuclear explosion simulation, ultra-far laser ranging and the like. Since the single crystal fiber has the advantages of both the crystal and the fiber in structure, higher average power and single pulse energy can be obtained in a simple and compact structure, and therefore, the laser amplifier is designed by adopting the single crystal fiber in the embodiment of the application.

The embodiment provides a laser amplifier based on a single crystal fiber. Fig. 3 is a schematic structural diagram of a laser amplifier according to an embodiment of the present application, and as shown in fig. 3, the laser amplifier includes: gain fiber 1, pump 2,fiber combiner 3,collimation end cap 4 andsingle crystal fiber 5. Those skilled in the art will appreciate that the laser amplifier configuration shown in fig. 3 does not constitute a limitation of the laser amplifier, and may include more or fewer components than shown, or some components in combination, or a different arrangement of components.

The following describes the components of the laser amplifier in detail with reference to fig. 3:

a pump 1outputting pump light 21; optionally, in the embodiment of the present application, two pumps 1 are selected, and the pump 1 is a semiconductor laser coupled through an optical fiber.

A gain fiber 1 of a higher-level amplifier that outputssignal light 11; specifically, the cladding NA of the gain fiber 1 is configured to be 1.2 times to 2 times of the core NA, so that after theoutput signal light 11 of the gain fiber 1 is diffused, the mode field diameter of the pump light 21 at the end cap is 1.2 times to 2 times of thesignal light 11, and the configuration can be realized by controlling the refractive indexes of the core, the cladding and the coating.

An optical fiber combiner MPC3, which is manufactured into an optical fiber combiner MPC3 by using an output optical fiber of a pump 1 and a gain optical fiber 1, wherein the optical fiber combiner MPC3 couples pump light 21 to the gain optical fiber 1 for output; the optical fiber combiner MPC3 does not generate a fusion point in the manufacturing and using processes, the damage risk is reduced, the optical fiber combiner MPC3 does not contain passive signal fibers in the structure, and the nonlinear effect generated by the transmission of thesignal light 11 in the passive signal fibers is reduced.

The input end of thecollimation end cap 4 is connected with theoutput section 31 of the gain fiber 1, and thecollimation end cap 4 is used for collimating thepump light 21 and thesignal light 11 and then outputting the collimated pump light and the signal light; optionally, thecollimating end cap 4 is a curved lens and/or a graded index lens, and may also be other collimating devices, and it can be understood that a device capable of collimating signal light output by an optical fiber may be used as an alternative to the embodiment of the present application.

The single crystaloptical fiber 5 is directly connected with the output end of thecollimation end cap 4, the single crystaloptical fiber 5 is used for amplifying the power of thesignal light 11 under the excitation of thepump light 21, and a space optical structure does not need to pass between thecollimation end cap 4 and the single crystaloptical fiber 5 in the embodiment of the application. Optionally, thecollimating end cap 4 is connected with thesingle crystal fiber 5 through a photoresist process, specifically, the photoresist process is connected through molecular diffusion, and has no coating film, no glue and no air gap, so that the damage threshold of the embodiment of the application is higher and the structure is more stable. Optionally, the base material of the single crystaloptical fiber 5 is YAG, YVO4, ceramic and/or quartz, or may be a base material of other gain media; the doping elements of thesingle crystal fiber 5 are Yb, Nd, Er and/or Tm, and may also be other laser gain medium doping elements, which are not specifically exemplified herein.

It should be noted that, due to the chromatic aberration of thecollimating end cap 4 and the slight difference between the pumpinglight 21 and the signal light emitting position, thesignal light 11 output by thecollimating end cap 4 is in a collimated state, theoutput pumping light 21 is in a collimated state with a divergence angle β, and the divergence angle β is smaller than the complementary angle of the critical angle of total reflection of the inner surface of thesingle crystal fiber 5, so that the pumpinglight 21 is totally reflected on the sidewall of thesingle crystal fiber 5 for multiple times. Based on this, thepump light 21 can be reflected by the sidewall multiple times in thesingle crystal fiber 5 to form a higher mode overlap with thesignal light 11, thereby obtaining a higher amplification gain.

Based on the above structure, referring to fig. 2 in combination, the pump light 21 output by the pump 1 is combined with the signal light 11 output by the gain fiber 1 of the upper-level amplifier through the fiber combiner MPC3, wherein, in the output section 31 of the gain fiber 1, a part of the pump power is absorbed, the signal light power is amplified, and the amplification gain of the laser amplifier is improved; then, the signal light 11 and the pump light 21 are directly input into the single crystal fiber 5 through the collimating end cap 4, the diameter of the collimated signal light 11 is a proper size capable of completely passing through the single crystal fiber 5, the diameter of the collimated pump light 21 is smaller than that of the single crystal fiber 5, but has a larger divergence angle based on the reasons of chromatic aberration, larger mode field of the pump light 21 and the like, the signal light 11 and the pump light 21 are shaped simultaneously through the collimating end cap 4, and the use requirements of the single crystal fiber 5 are met; in the single crystal fiber 5, the pump light 21 is absorbed by the single crystal fiber 5 through multiple total reflections, and the signal light 11 passes along the center of the single crystal fiber 5 and is amplified.

The laser amplifier adopting the structure realizes the structural design of the laser amplifier with simple structure, easy assembly and adjustment and high stability by fusing the gain optical fiber 1 and the single crystaloptical fiber 5, and the optical fiber beam combiner MCU is directly manufactured by using the active optical fiber of the superior amplifier, namely the gain optical fiber 1, so that the passive optical fiber between two stages is saved, and the nonlinear effect is reduced; the laser amplifier of this application is approximate full fiber structure, compares in prior art and adopts the technical scheme of a large amount of space optical structures, and this application is lower to the requirement of environment.

The embodiments of the present application are described and illustrated below by means of preferred embodiments.

The preferred embodiment selects a gain fiber 1 with a core NA of 0.14, a cladding NA of 0.22, acollimating endcap 4 with a focal length of 2mm, and asingle crystal fiber 5 with a length of 60mm and a refractive index of 1.6.

Based on the laser amplifier of the preferred embodiment of the present application obtained by the above configuration, the wavelength of thesignal light 11 of the present embodiment is 1um, and thecollimated signal light 11 with a diameter of 0.56mm is obtained after being collimated by thecollimating end cap 4, and the diameter of the collimated signal light is 0.71mm when the collimated signal light is emitted from the single crystaloptical fiber 5; the wavelength of thepump light 21 of this embodiment is 0.94um, and the pump light with a diameter of 0.9mm is obtained after passing through thecollimating end cap 4, and has a certain convergence, and is totally reflected inside thesingle crystal fiber 5 for multiple times. With the arrangement, the diameter of thepump light 21 is kept 1.2-2 times of that of thesignal light 11, so that when the pump 1 can smoothly enter thesingle crystal fiber 5, the diameter of thesignal light 11 is larger, and the utilization rate of thesignal light 11 to thepump light 21 is improved.

The two pumps 1 respectively output 150W of power, the power after being combined by the fiber combiner MPC3 is about 280W, the length of theoutput section 31 of the gain fiber 1 is short, about 30W of pump light 21 can be absorbed, and the residual 250W ofpump light 21 is absorbed by 90% after passing through thesingle crystal fiber 5; experiments prove that200mW signal light 11 input by the upper-level amplifier is amplified to 8W through theoutput section 31 of the gain optical fiber 1 and then can be amplified to 100W through the single crystaloptical fiber 5, that is, the gain factor of the whole amplification level of the laser amplifier of the embodiment of the application is about 500 times.

In addition, the laser amplifier of the embodiment of the present application described in conjunction with fig. 3-4 can form a new laser.

In addition, in combination with the laser amplifier in the above embodiments, the present application may provide an optical system, specifically, the optical system includes a laser light source, a first-stage laser amplifier, and the laser amplifier in the above embodiments.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (9)

1. A laser amplifier, comprising:

a pump for outputting pump light;

a gain fiber of the superior amplifier outputting signal light;

the optical fiber combiner MPC is manufactured based on the output optical fiber of the pump and the gain optical fiber, and couples the pump light to the gain optical fiber for output;

the input end of the collimation end cap is connected with the output section of the gain optical fiber, and the collimation end cap is used for collimating the pump light and the signal light and then outputting the collimated pump light and signal light;

and the single crystal optical fiber is connected with the output end of the collimation end cap and is used for amplifying the signal light power under the excitation of the pump light.

2. The laser amplifier of claim 1, wherein the gain fiber has a cladding NA configured to be 1.2 times to 2 times the core NA.

3. The laser amplifier of claim 2, wherein the collimating end cap outputs the signal light in a collimated state and outputs the pump light in a collimated state having a divergence angle β smaller than a complementary angle of a critical angle of total reflection of the inner surface of the single crystal optical fiber.

4. A laser amplifier according to claim 3, in which the single crystal fibre is directly connected to the output end of the collimating end cap.

5. The laser amplifier according to any of claims 1-4, wherein the collimating end cap is coupled to the single crystal fiber by a photonic crystal glue process.

6. The laser amplifier according to any of claims 1-4, wherein the collimating end cap is a curved lens and/or a graded index lens.

7. The laser amplifier according to any of claims 1-4, wherein the pump is a semiconductor laser.

8. A laser formed based on the laser amplifier of any of claims 1-7.

9. An optical system comprising a laser light source, a first stage laser amplifier and a laser amplifier according to any one of claims 1 to 7.

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