A laser that outputs a uniform beam of light

Abstract

The application provides a laser device for outputting uniform light beams, which comprises a power supply, a pump source, a gain medium, a beam shaping system, a cavity mirror set and a water cooling machine, the pump source is arranged at the side of the cavity mirror set, the pump light generated by the pump source is irradiated into the gain medium after shaping and forms laser light; the cavity mirror set comprises a cavity mirror I and a cavity mirror II, the gain medium is arranged between the cavity mirror I and the cavity mirror II, the laser light generated by the gain medium generates laser oscillation at the position of the optical axis, and the power and the light spot are amplified along the direction perpendicular to and away from the optical axis to obtain output laser light, and the output laser light is emitted along the direction parallel to the optical axis after being reflected by the cavity mirror I and the cavity mirror II. The application adopts the cavity type design of off-axis unstable cavity, combines the characteristics of off-axis emission and the structural characteristics of the pump source, and effectively avoids the non-uniformity of the laser output light spot caused by the non-uniformity of the pump source.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more specifically to a laser that outputs a uniform beam. Background Technology

[0002] The uniformity of the near-field spot is a crucial indicator of a laser's output characteristics. A significant factor influencing near-field spot uniformity is the inhomogeneity of the laser pump and the choice of the optical cavity. Generally, a lower active particle concentration or a longer pump length can effectively improve pump uniformity. Typical examples include large-aperture side or end-face pumping slabs and end-face pumping disks. The former reduces the power absorbed per unit volume of the pump light propagating in the medium by using a lower gain medium concentration, but still obeys the Lambert-Beer law, so the pump light still decays exponentially along the propagation direction. Only in a small local area, due to the lower active particle concentration, is the absorption less, resulting in a more uniform absorption power density. The latter, due to the thinner disk itself, has less absorption per single pass. Therefore, multi-pass pumping is typically used to achieve sufficient pump light absorption. The pump light propagates in opposite directions between adjacent passes, allowing a higher absorption power density to be obtained at a location with lower power density at the end of the previous pass. The characteristics of this structure are: the lower the single-pass absorption, the larger the number of pump passes, and the more uniform the overall pump light.

[0003] In the selection of optical cavities, stable cavities, due to the inherent existence of their spatial modes, typically contain higher-order modes in their output beam, resulting in spatial power non-uniformity. In contrast, unstable cavities have higher mode discrimination capability and a larger fundamental mode size, making their output beam generally more uniform.

[0004] The actual output beam of a laser is affected by the pumping technique and also limited by the cavity shape. Therefore, the selection of a suitable pump and cavity shape is particularly important. Summary of the Invention

[0005] To address the aforementioned technical problems, a laser that outputs a uniform beam is provided.

[0006] The technical means employed in this invention are as follows:

[0007] A laser that outputs a uniform beam, the laser comprising a power supply, a pump source, a gain medium, a beam shaping system, a cavity mirror assembly, and a water cooler;

[0008] The pump source is located on the side of the cavity mirror assembly, and the pump source generates pump light under the action of the power supply. The pump light is irradiated into the gain medium after being shaped by the beam shaping system. After absorbing the pump light, the gain medium realizes the inversion of upper energy level particles to form laser. The water chiller delivers circulating cooling medium to the gain medium, and the circulating cooling medium removes the heat generated by the gain medium due to light emission.

[0009] The cavity mirror assembly includes cavity mirror I and cavity mirror II, which form a laser resonant cavity. The gain medium is disposed between cavity mirror I and cavity mirror II. The optical axes of cavity mirror I and cavity mirror II coincide with the incident surface of the gain medium that absorbs the pump light. The transmission direction of the pump light intersects the optical axis.

[0010] The laser generated by the gain medium oscillates at the optical axis position and amplifies its power and spot size in a direction perpendicular to and away from the optical axis to obtain an output laser. The output laser is then emitted in a direction parallel to the optical axis after being reflected by cavity mirror I and cavity mirror II.

[0011] Furthermore, the gain medium is a solid, which is a crystal, ceramic, or glass material doped with Nd or Yb ions;

[0012] Alternatively, the gain medium may be a gas, specifically an optical pump gas material using alkali metals, copper atoms, or inert gases as active particles.

[0013] Furthermore, the pump source is an LD, LED, or xenon lamp with light-emitting capability, and its output wavelength can be absorbed by the activated particles in the gain medium to achieve population inversion.

[0014] Furthermore, the radii of curvature of the endoscope I and the endoscope II are R1 and R2, respectively, and the center distance between them is L. The endoscope I and the endoscope II satisfy the unstable cavity condition |g1g2|>1, where g1=1-L / R1 and g2=1-L / R2.

[0015] Preferably, cavity mirror I and cavity mirror II are confocal unstable cavities, in which case L = (R1 + R2) / 2, and the output laser beam of the laser is parallel light.

[0016] Furthermore, the dimension a of the gain medium in the optical axis direction is less than L, and satisfies... N eff λ is the effective Fresnel number of the laser along the optical axis within the laser resonant cavity; λ is the wavelength of the laser.

[0017] Furthermore, the incident surface of the gain medium absorbing the pump light is coated with an antireflection film I that matches the wavelength of the pump light, and the surface of the gain medium intersecting the optical axis is coated with an antireflection film II that matches the wavelength of the output laser.

[0018] Furthermore, both cavity mirror I and cavity mirror II are reflective mirrors, and their reflective surfaces are coated with a high-reflectivity film layer that matches the wavelength of the output laser.

[0019] Alternatively, the cavity mirror I may be a concave mirror and the cavity mirror II may be a convex mirror;

[0020] The radius of curvature R2 of cavity mirror II is greater than the radius of curvature R1 of cavity mirror I. The optical axes of cavity mirror I and cavity mirror II are located at their ends near the gain medium, and the optical axes are perpendicular to the propagation direction of the pump light.

[0021] The end of the cavity mirror II away from the gain medium is cut in a direction parallel to the optical axis. The ratio of the cut portion to the uncut portion in the direction perpendicular to the optical axis is (M-1):1, where M = |R2 / R1|, and M is the amplification rate of the laser during each round trip in the laser resonant cavity.

[0022] The light emitted by the pump source under the power supply is irradiated onto the gain medium by the beam shaping system. The pump light absorbed by the gain medium attenuates exponentially along the propagation direction of the pump light, while the seed light of the laser is generated at the optical axis and begins to oscillate and amplify. The laser spot size amplifies exponentially along the pump light propagation direction, with the base being the amplification factor M. The exponential attenuation of the absorbed pump light power and the exponential amplification of the laser size along the propagation direction of the pump light form an effective method for homogenizing the laser intensity. In the dimension perpendicular to the pump light propagation direction, the resonant cavity is a parallel planar cavity, and the smaller Fresnel number is beneficial for achieving single transverse mode laser output, avoiding the non-uniform spatial intensity distribution of the output laser caused by higher-order modes, thus achieving a more uniform laser output.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. In this invention, an off-axis unstable cavity design is adopted, which combines the characteristics of off-axis emission with the characteristics of pump source structure, effectively avoiding the non-uniformity of laser output spot caused by pump source non-uniformity.

[0025] 2. In this invention, the structure design of single-sided pumping of the pump source is adopted, which greatly simplifies the problem of structural complexity caused by the need to improve pump uniformity.

[0026] 3. In this invention, the laser output spot is a solid spot, which effectively improves the brightness and focus of the laser in the far field.

[0027] Based on the above reasons, this invention can be widely applied in fields such as lasers. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of a laser structure that outputs a uniform beam in a specific embodiment of the present invention.

[0030] Figure 2 This is a front view of the pump source and endoscope assembly structure in a specific embodiment of the present invention. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0035] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0036] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0037] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0038] like Figures 1-2As shown, a laser that outputs a uniform beam includes a power supply 1, a pump source 2, a gain medium 3, a beam shaping system 4, a cavity mirror assembly 5, and a water cooler 6.

[0039] The pump source 2 is located on the side of the cavity mirror assembly 5, and the pump source 2 generates pump light under the action of the power supply 1. The pump light is irradiated into the gain medium 3 after being shaped by the beam shaping system 4. After absorbing the pump light, the gain medium 3 realizes the inversion of the upper energy level particles to form laser. The water chiller 6 delivers circulating cooling medium to the gain medium 3, and the circulating cooling medium removes the heat generated by the light emission of the gain medium 3.

[0040] The cavity mirror assembly 5 includes cavity mirror I7 and cavity mirror II8, which form a laser resonant cavity. The gain medium 3 is disposed between cavity mirror I7 and cavity mirror II8. The optical axis 9 of cavity mirror I7 and cavity mirror II8 (e.g., Figure 2 (As shown by the dashed line) coincides with the incident surface of the pump light absorbed by the gain medium 3; the transmission direction of the pump light intersects with the optical axis 9, which is perpendicular in this embodiment;

[0041] The laser generated by the gain medium 3 oscillates at the optical axis 9 and amplifies its power and spot size in a direction perpendicular to and away from the optical axis 9 to obtain an output laser. The output laser is then emitted in a direction parallel to the optical axis 9 after being reflected by the cavity mirror I7 and the cavity mirror II8.

[0042] The gain medium 3 can be a solid or a gas; in this embodiment, a solid is used, and the gain medium 3 is a Yb:YAG crystal. The Yb:YAG crystal is a flat, elongated cuboid with dimensions of 100mm × 10mm × 5mm, and the Yb particle doping concentration is 0.6 at.%. The incident surface (10mm × 5mm) of the pump light of the gain medium 3 is coated with an antireflection film I with a center wavelength of 940nm, and the surface (100mm × 10mm) intersecting the optical axis of the laser resonator is coated with an antireflection film II with an output laser wavelength of 1030nm.

[0043] The center distance between cavity mirrors I7 and II8 is L = 1000 mm, and their curvatures are R1 = -2000 mm and R2 = 4000 mm respectively, satisfying the unstable cavity condition |g1g2| > 1. Where g1 = 1 + 1000 / 2000 = 3 / 2, and g2 = 1 - 1000 / 4000 = 3 / 4, this constitutes a confocal unstable cavity. In this case, the laser output beam is parallel.

[0044] In this embodiment, the laparoscope I7 is a concave mirror and the laparoscope II8 is a convex mirror;

[0045] The radius of curvature R2 of cavity mirror II8 is greater than the radius of curvature R1 of cavity mirror I7. The optical axis 9 of cavity mirror I7 and cavity mirror II8 is located at one end near the gain medium 3, and the optical axis 9 is perpendicular to the propagation direction of the pump light. The end of cavity mirror II8 away from the gain medium 4 is cut in a direction parallel to the optical axis 9. The ratio of the cut part to the uncut part in the direction perpendicular to the optical axis is (M-1):1, where M=|R2 / R1|=|4000 / 2000|=2, and M is the amplification rate of the laser during each round trip in the laser resonant cavity.

[0046] The gain medium has a dimension a = 0.5 mm less than L = 1000 mm along the optical axis, and satisfies the following conditions: N eff λ is the effective Fresnel number of the laser along the optical axis within the laser resonant cavity; λ is the wavelength of the laser.

[0047] The pump source described in this embodiment is a bar array composed of InGaAs semiconductor lasers, with the array size being 5x20 and arranged horizontally.

[0048] The light emitted from pump source 2 is irradiated onto gain medium 3 by shaping system 4, and the pump light absorbed by gain medium 3 is directed along... Figure 2 The light decays exponentially in the Y direction, and the seed light of the laser happens to be on the pump surface of the gain medium 3 with the optical axis 9 ( Figure 2 The laser beam originates and begins to oscillate and amplify at the point indicated by the dashed line. The laser spot size amplifies exponentially along the pump light propagation direction, with the base being the amplification factor M = 2. In the pump light propagation direction, the exponential attenuation of the absorbed pump light power and the exponential amplification of the laser size form an effective method for homogenizing the laser intensity. In the dimension perpendicular to the pump light propagation direction, the laser resonator is a parallel planar cavity. The smaller Fresnel number facilitates single-transverse mode laser output, avoiding the non-uniform spatial intensity distribution of the output laser caused by higher-order modes, thus achieving a more uniform laser output.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser that outputs a uniform beam, the laser comprising a power supply, a pump source, a gain medium, a beam shaping system, a cavity mirror assembly, and a water cooler, characterized in that: The pump source is located on the side of the cavity mirror assembly, and the pump source generates pump light under the action of the power supply. The pump light is irradiated into the gain medium after being shaped by the beam shaping system. After absorbing the pump light, the gain medium realizes the inversion of upper energy level particles to form laser. The water chiller delivers circulating cooling medium to the gain medium, and the circulating cooling medium removes the heat generated by the gain medium due to light emission. The cavity mirror assembly includes cavity mirror I and cavity mirror II, which form a laser resonant cavity. The gain medium is disposed between cavity mirror I and cavity mirror II, and the optical axes of cavity mirror I and cavity mirror II coincide with the incident surface of the gain medium that absorbs the pump light. The transmission direction of the pump light intersects the optical axis; The pump light absorbed by the gain medium decays exponentially along its transmission direction. The laser oscillates at the optical axis position and achieves exponential amplification of the spot area along the transmission direction of the pump light. This expansion of the spot area compensates for the attenuation of the pump power and achieves uniformity of the output laser intensity. The laser generated by the gain medium oscillates at the optical axis position and amplifies its power and spot size in a direction perpendicular to and away from the optical axis to obtain an output laser. The output laser is then emitted in a direction parallel to the optical axis after being reflected by cavity mirror I and cavity mirror II. The radii of curvature of the laparoscope I and the laparoscope II are respectively and The center distance between the two is L, and the cavity mirror I and the cavity mirror II satisfy the unstable cavity condition. ,in, , .

2. A laser with uniform beam output according to claim 1, characterized in that, The gain medium is a solid, which is a crystal, ceramic or glass material doped with Nd or Yb ions.

3. A laser for outputting a uniform beam according to claim 1, characterized in that, The gain medium is a gas, specifically an optical pump gas material using alkali metals, copper atoms, or inert gases as active particles.

4. A laser with uniform beam output according to claim 1, characterized in that, The pump source is an LD, LED, or xenon lamp with light-emitting capability, and its output wavelength can be absorbed by the activated particles in the gain medium to achieve population inversion.

5. A laser with uniform beam output according to claim 4, characterized in that, The cavity mirror I and the cavity mirror II are confocal unstable cavities. The output laser beam of the laser is parallel light.

6. A laser for outputting a uniform beam according to claim 1, characterized in that, The incident surface of the gain medium that absorbs the pump light is coated with an antireflection film I that matches the wavelength of the pump light, and the surface of the gain medium that intersects the optical axis is coated with an antireflection film II that matches the wavelength of the output laser.

7. A laser for outputting a uniform beam according to claim 1, characterized in that, Both cavity mirror I and cavity mirror II are reflective mirrors, and their reflective surfaces are coated with a high-reflectivity film layer that matches the wavelength of the output laser.

8. A laser for outputting a uniform beam according to claim 1, characterized in that, The cavity mirror I is a concave mirror and the cavity mirror II is a convex mirror, the radius of curvature of the cavity mirror II is... The radius of curvature of the laparoscope I is greater than that of the laparoscope I. The optical axes of cavity mirror I and cavity mirror II are located at their ends near the gain medium, and the optical axes are perpendicular to the propagation direction of the pump light. The end of the cavity mirror II furthest from the gain medium is cut along a direction parallel to the optical axis, and the ratio of the cut portion to the uncut portion in the direction perpendicular to the optical axis is: ,in, , The amplification rate of the laser during each round trip in the laser resonant cavity.

9. A laser for outputting a uniform beam according to claim 1, characterized in that, The size of the gain medium along the optical axis Less than L, and satisfying , The effective Fresnel number of the laser beam along the optical axis within the laser resonant cavity. The wavelength of the laser is denoted as .

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