Optical resonant cavity and laser

Abstract

The utility model relates to the field of lasers, and particularly discloses an optical resonant cavity and a laser, and the optical resonant cavity comprises a first reflection part, a second reflection part and an optical fiber assembly. A resonant cavity is defined by the first reflecting part and the second reflecting part; the optical fiber assembly is located in the resonant cavity, one end of the optical fiber assembly is connected with the first reflector, one end of the optical fiber assembly away from the first reflector is connected with the second reflector, and the optical fiber assembly is bent. The conventional technical scheme is of a single-core line type, and the effective gain effect cannot be achieved due to the short length, so that the gain effect is improved by bending the optical fiber assembly to increase the length, and under the condition that the same gain effect is achieved, the bent optical fiber assembly is shorter in length and smaller in occupied space.

Description

Technical Field

[0001] The present application relates to the field of lasers, and in particular to an optical resonant cavity and a laser. Background Art

[0002] With the rapid development of fiber laser and fiber amplifier technology, rare earth element-doped optical fibers, as their core gain medium, have been widely used in fields such as communications, materials processing, medical treatment, and scientific research. By precisely controlling the doping of rare earth elements such as ytterbium and erbium, these optical fibers can efficiently absorb pump light energy and convert it into signal light output at a specific wavelength, exhibiting excellent gain characteristics. To achieve efficient optical signal amplification, traditional designs often use high-reflectivity and low-reflectivity gratings fused at both ends of rare earth element-doped optical fibers to construct an optical resonant cavity. This promotes multiple reflections and interference of light within the fiber core, significantly enhancing the intensity and energy density of the optical signal, ultimately outputting a high-performance laser beam with good monochromaticity, high brightness, concentrated energy, and adjustable power.

[0003] The currently widely used design based on single-core linear optical fiber still has some problems. For example, since the transmission distance of light in a single-core linear optical fiber is limited, in order to achieve sufficient gain effect, it is often necessary to increase the length of the optical fiber, which increases the difficulty of preparation. Utility Model Content

[0004] In view of this, the purpose of this application is to overcome the deficiencies in the prior art and to provide an optical resonant cavity and a laser.

[0005] To achieve the above objectives, the technical solutions adopted in this application are as follows:

[0006] This application provides:

[0007] An optical resonant cavity, comprising:

[0008] a first reflective member;

[0009] a second reflecting member, wherein the first reflecting member and the second reflecting member define a resonant cavity;

[0010] An optical fiber assembly is located in the resonant cavity, one end of the optical fiber assembly is connected to the first reflector, and the end of the optical fiber assembly away from the first reflector is connected to the second reflector, and the optical fiber assembly is bent.

[0011] Furthermore, the first reflective element is a reflective grating or a reflective film, and the second reflective element is a reflective grating or a reflective film.

[0012] Furthermore, the optical fiber assembly has n fiber cores, satisfying n≥1; when n≥2, the fiber cores are independent of each other.

[0013] Furthermore, the fiber core is a doped optical fiber.

[0014] Furthermore, the optical fiber assembly is arranged in a spiral manner.

[0015] Furthermore, the outer surface of the optical fiber component is covered with a first cladding, the outer surface of the first cladding is covered with a second cladding, and the refractive index of the second cladding is smaller than the refractive index of the first cladding.

[0016] Furthermore, the first cladding is circular, elliptical or polygonal.

[0017] Furthermore, the second cladding is circular.

[0018] Furthermore, the outer surface of the second cladding is coated with a protective layer.

[0019] The present application also provides a laser, comprising any of the optical resonant cavities described above.

[0020] The conventional technical solution of this application is a single-core line type. Due to its short length, it cannot achieve an effective gain effect. Therefore, the optical fiber component is bent to increase its length, thereby improving the gain effect. While achieving the same gain effect, the length of the bent optical fiber component is shorter and occupies less space.

[0021] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 The schematic diagram of the overall structure of the optical resonant cavity of the present application is shown;

[0024] Figure 2 The figure shows the overall structure of the optical fiber assembly of the present application;

[0025] Figure 3 It shows a cross-sectional schematic diagram of the optical fiber assembly of the present application having four fiber cores and a first cladding in a circular state;

[0026] Figure 4 A cross-sectional schematic diagram of the optical fiber assembly of the present application is shown, which has four fiber cores and a first cladding layer in a regular octagonal shape;

[0027] Figure 5 A cross-sectional schematic diagram of the optical fiber assembly of the present application having four fiber cores and an elliptical first cladding is shown;

[0028] Figure 6 It shows a cross-sectional schematic diagram of the optical fiber assembly of the present application having three fiber cores and a first cladding in a circular state;

[0029] Figure 7 It shows a cross-sectional schematic diagram of the optical fiber assembly of the present application having five fiber cores and a first cladding in a circular state.

[0030] Description of main component symbols:

[0031] 100, first reflector; 200, second reflector; 300, optical fiber assembly; 400, first cladding; 500, second cladding; 600, protective layer. DETAILED DESCRIPTION

[0032] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0033] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0035] In this application, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components or interactions between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

[0036] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0037] Example:

[0038] The basic operating principle of fiber lasers involves the absorption, conversion, and amplification of pump light within optical fibers doped with rare earth elements. For example, the doping of rare earth elements such as ytterbium and erbium within the fiber creates an energy level structure that allows the pump light to excite electrons to a high-energy state. These electrons then return to a low-energy state through spontaneous or stimulated emission, emitting laser light at a different wavelength than the pump light but with a single frequency. In this process, the fiber acts as a gain medium, and factors such as its length, doping concentration, and pump light power all have a significant impact on the gain effect.

[0039] Optical fiber doped with rare earth elements is the core gain medium of the fiber laser. For example, rare earth elements such as ytterbium and erbium are doped in the optical fiber, which can absorb pump light and convert it into laser (signal light) output, thereby achieving a gain effect. High-reflectivity and low-reflectivity optical fibers are also arranged on both sides of the optical fiber to construct an optical resonant cavity, which promotes light to be reflected in the optical fiber. However, the existing optical fiber usually has only a single fiber body when achieving the gain effect. Due to its short length, the gain effect is correspondingly poor. Therefore, in order to improve the gain effect, the length needs to be increased to meet the need of the gain effect. However, the increase in length will inevitably increase the space occupied. For example, the increase in length will increase the volume of the optical fiber disk, and the production cost will also increase. For this reason, the present application bends the optical fiber assembly 300, that is, the fiber body length of the optical fiber assembly 300 is longer under the same length, thereby better achieving the need for the gain effect.

[0040] Specifically, the present application provides an optical resonant cavity, including a first reflective element 100 , a second reflective element 200 and an optical fiber assembly 300 .

[0041] The first reflector 100 and the second reflector 200 define a resonant cavity, the optical fiber assembly 300 is located in the resonant cavity, one end of the optical fiber assembly 300 is connected to the first reflector 100, and the end of the optical fiber assembly 300 away from the first reflector 100 is connected to the second reflector 200, and the optical fiber assembly 300 is bent.

[0042] This application mainly uses the doped medium in the optical fiber component 300 to absorb pump light and excite it into laser output, and the specific process is as follows.

[0043] See Figure 1 As shown, the optical fiber component 300 is the fiber core, and the number of fiber cores is not limited here. Specifically, the pump light enters the optical fiber component 300 through the first reflector 100, and the pump light is absorbed by the optical fiber component 300. After the medium absorbs the pump light, the electrons transition to a high energy level. The high energy level is an unstable state and will spontaneously or stimulatedly return to a stable low energy state. During this transition process, laser light will be released. The laser light is reflected by the second reflector 200 into the optical fiber component 300, and is reflected again into the optical fiber component 300 through the first reflector 100, and then reflected again through the optical fiber component 300 to the first reflector 100, and the above operation is repeated. Finally, the laser light is output through the optical fiber component 300 at a higher energy state.

[0044] It should be noted that after the gain fiber absorbs the pump light and is excited into laser, most of the laser light is transmitted from the optical fiber component 300 and finally output from 200. A small part of the laser light repeats the above reflection operation, that is, the laser light passes through the first reflector 100 → optical fiber component 300 → second reflector 200 → optical fiber component 300 → first reflector 100 → optical fiber component 300 → second reflector 200... and other circular paths. In this path, the energy of the laser light continues to increase, thereby realizing gain accumulation, and finally output through the second reflector 200 in a higher energy state.

[0045] The first reflective element 100 is a reflective grating or a reflective film, and the second reflective element 200 is a reflective grating or a reflective film.

[0046] In this embodiment, the first reflector 100 has a relatively high reflectivity, which is above 99%. Its main function is to reflect the laser and reflect the laser into the resonant cavity formed by the first reflector 100 and the second reflector 200, that is, it can be reflected into the optical fiber assembly 300 for enhancement, thereby improving the output power and stability of the laser; the second reflector 200 is the output section of the laser and has a relatively low reflectivity, that is, only part of the laser can be reflected by the second reflector 200 into the optical fiber assembly 300, and most of the laser passes through the second reflector 200 and is output. Usually, only about 10% of the laser can be reflected, that is, the laser can be reflected by the second reflector 200 into the optical fiber assembly 300.

[0047] For example, the reflectivity of the first reflector 100 and the second reflector 200 can be designed and selected according to actual needs, that is, the reflection of light of different wavelengths can be selected according to actual needs. In this embodiment, the first reflector 100 and the second reflector 200 are both selected as reflection gratings. Of course, they can also be selected according to needs, for example: the first reflector 100 is selected as a reflection grating, and the second reflector 200 is selected as a reflection film; or, the first reflector 100 is selected as a reflection film, and the second reflector 200 is selected as a reflection grating; or, the first reflector 100 is selected as a reflection film, and the second reflector 200 is selected as a reflection grating.

[0048] The optical fiber assembly 300 has n fiber cores, where n≥1. When n≥2, the fiber cores are independent of each other.

[0049] In this embodiment, the two ends of the optical fiber assembly 300 are respectively connected to the first reflector 100 and the second reflector 200 by fusion splicing. The existing fiber core is usually only arranged in a single straight line. There is a certain probability that the pump light cannot enter the fiber core and cannot be excited into a laser by the fiber core, thereby reducing the gain effect. In addition, the gain effect is further reduced because the existing single fiber core is arranged in a straight line.

[0050] See Figure 1 and Figure 2 As shown, since the optical fiber assembly 300 has at least one fiber core and is bent, when there are multiple fiber cores, the multiple fiber cores can enable more pump light to be more fully absorbed and can stimulate more lasers, thereby improving the gain effect.

[0051] The cross-sectional shape of the fiber core may be circular, elliptical, square or other achievable shapes. In this embodiment, in order to facilitate production and manufacturing, the shape of the fiber core is circular.

[0052] See Figures 3 to 5As shown, for example, the number of fiber cores can be 1, 2, 3, 4, 5, etc. In this embodiment, there are 4 fiber cores, and the diameter of each fiber core is 20 microns. The diameter of the fiber core can be designed according to needs and is not limited here.

[0053] See Figure 3 、 Figure 6 and Figure 7 As shown, Figure 3 The cross-sectional diagram is shown when there are 4 fiber cores. Figure 6 The cross-sectional diagram of the fiber core with 3 fibers is shown. Figure 7 Shown is a cross-sectional diagram of a state where there are 5 fiber cores.

[0054] In order to prevent the influence between the fiber cores, when the number of fiber cores is greater than 2, the fiber cores are independent of each other and do not affect each other, that is, the fiber cores do not intersect with each other.

[0055] The fiber core is a doped fiber. It should be noted here that doped fiber can be understood as a fiber with added impurities. In order to be able to excite the pump light into laser, it is necessary to dope some existing fiber cores with rare earth elements. For example, rare earth elements such as ytterbium and erbium are added to the optical fiber, so that it can efficiently absorb the pump light energy and excite laser light of a specific wavelength, thereby achieving a gain effect. In this embodiment, the treatment can be doped with the above two rare earth elements, or other rare earth elements that can achieve a gain effect. There is no specific limitation here, that is, as long as the element can achieve a gain effect under the premise of meeting the needs, it can be used.

[0056] The optical fiber assembly 300 is spirally arranged; see Figure 1 and Figure 2 As shown, each fiber core in the optical fiber assembly 300 is spirally bent. In practice, other bending forms can be used as needed, which are not specifically limited here.

[0057] The outer surface of the optical fiber assembly 300 is covered with a first cladding 400 , and the outer surface of the first cladding 400 is covered with a second cladding 500 . The refractive index of the second cladding 500 is lower than that of the first cladding 400 .

[0058] See Figure 1 and Figure 2 As shown, in this embodiment, the refractive index of the optical fiber component 300 is greater than the refractive index of the first cladding 400, the refractive index of the first cladding 400 is greater than the refractive index of the second cladding 500, and the second cladding 500 is arranged on the outer surface of the first cladding 400. The second cladding 500 and the first cladding 400 form a refractive index difference, which can totally reflect the pump light, so that the pump light is transmitted through the first cladding 400.

[0059] The first cladding 400 is circular, elliptical or polygonal; the second cladding 500 is circular.

[0060] See Figure 1 and Figure 2 As shown, the second cladding 500 covers the first cladding 400 inside thereof, and the first cladding 400 covers at least one fiber core. According to actual needs, the shape of the first cladding 400 can be set to different shapes as needed, for example, it can be set to a circle, an ellipse or a polygon, etc. It should be noted here that when the first cladding 400 is a polygon, its shape can be a triangle, a quadrilateral, a pentagon, a hexagon, a heptagon, an octagon, etc. In this embodiment, in order to facilitate production and reduce production costs, the first cladding 400 can be designed to be circular and the second cladding 500 can also be set to be circular.

[0061] See Figures 3 to 5 As shown, in this embodiment, Figure 3 A schematic cross-sectional view showing the first cladding layer 400 in a circular state, Figure 4 A schematic cross-sectional view showing the first cladding layer 400 in a regular octagonal state is shown. Figure 5 A schematic cross-sectional view of the first cladding layer 400 in an elliptical state is shown.

[0062] In actual use, in order to prevent the second cladding 500 from being damaged, a protective layer 600 is coated on the outer surface of the second cladding 500; in this embodiment, the protective layer 600 can be epoxy resin, acrylic resin, polyimide, acrylic resin, etc. In practice, other materials can be selected as the protective layer 600 as needed, and the specific materials are not limited here.

[0063] In this embodiment, the first reflector 100 and the second reflector 200 both have almost 100% transmittance to the pump light, that is, the pump light can pass through the first reflector 100 and the second reflector 200. The first reflector 100 has a higher reflectivity to the laser, and the second reflector 200 has a lower reflectivity to the laser. The size of the reflectivity can be designed and selected according to needs.

[0064] See Figure 1 and Figure 2As shown, for ease of understanding, here we take the example of pump light irradiating and transmitting from the first reflector 100 toward the second reflector 200. First, the pump light passes through the first reflector 100 and enters the respective fiber cores doped with rare earth elements in the optical fiber assembly 300. The rare earth elements absorb the pump light and are excited into lasers. When the laser is transmitted to the second reflector 200, most of the laser light passes through the second reflector 200 and is output, and a small part is re-reflected into the fiber core in the optical fiber assembly 300 and transmitted to the first reflector 100. The first reflector 100 continues to reflect the laser light from the fiber core into the fiber core, thereby increasing the intensity of the laser light. Finally, the above process is repeated, and finally a higher energy level laser light is output at the second reflector 200.

[0065] The present application also provides a laser, comprising any of the optical resonant cavities described above.

[0066] The laser provided in this embodiment includes all the beneficial effects of the optical resonant cavity described in any of the above embodiments. The specific beneficial effects will not be elaborated here. For details, please refer to the contents described in the above optical resonant cavity.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0068] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An optical resonant cavity, characterized in that: include: a first reflecting member (100); a second reflecting member (200), wherein the first reflecting member (100) and the second reflecting member (200) define a resonant cavity; An optical fiber assembly (300) is located in the resonant cavity, one end of the optical fiber assembly (300) is connected to the first reflector (100), and one end of the optical fiber assembly (300) away from the first reflector (100) is connected to the second reflector (200), and the optical fiber assembly (300) is bent.

2. The optical resonant cavity according to claim 1, wherein: The first reflecting element (100) is a reflecting grating or a reflecting film, and the second reflecting element (200) is a reflecting grating or a reflecting film.

3. The optical resonant cavity according to claim 1, wherein: The optical fiber assembly (300) has n fiber cores, satisfying n≥1; when n≥2, the fiber cores are independent of each other.

4. The optical resonant cavity according to claim 3, wherein: The fiber core is a doped optical fiber.

5. The optical resonant cavity according to claim 1, wherein: The optical fiber assembly (300) is arranged in a spiral.

6. The optical resonant cavity according to claim 1, wherein: The outer surface of the optical fiber component (300) is covered with a first cladding (400), the outer surface of the first cladding (400) is covered with a second cladding (500), and the refractive index of the second cladding (500) is smaller than the refractive index of the first cladding (400).

7. The optical resonant cavity according to claim 6, wherein: The first cladding (400) is circular, elliptical or polygonal.

8. The optical resonant cavity according to claim 6, wherein: The second cladding (500) is circular.

9. The optical resonant cavity according to claim 8, wherein: The outer surface of the second cladding (500) is coated with a protective layer (600).

10. A laser, characterized in that: The optical resonant cavity comprises the optical resonant cavity according to any one of claims 1 to 9.

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