Three-mirror ring cavity laser mode converter

Abstract

The utility model discloses a three-mirror annular cavity laser mode converter, which comprises a plano-concave high-reflectivity mirror, a first output mirror, a second output mirror and a laser, the plano-concave high-reflectivity mirror, the first output mirror and the second output mirror form a three-mirror annular cavity, and a fundamental mode light beam emitted by the laser enters the three-mirror annular cavity through the first output mirror. A closed circulating light path is formed in the three-mirror annular cavity; the position of the plano-concave high-reflectivity mirror is adjustable in the direction perpendicular to a fundamental mode light beam, the position of the laser can translate or incline relative to the three-mirror annular cavity, and after any one of the position of the plano-concave high-reflectivity mirror or the position of the laser is adjusted, a cavity mode with a target cavity length is formed in the three-mirror annular cavity by a circulating light path. Therefore, the output of the target high-order mode laser matched with the cavity mode is realized.

Description

Technical Field

[0001] The utility model belongs to the field of laser mode converters, and in particular relates to a three-mirror ring cavity laser mode converter. Background Art

[0002] High-order mode lasers have rich information content and have important applications in the fields of life sciences, laser measurement, optical communications, etc. They can be converted into vortex lasers through cylindrical lenses and have received increasing attention in recent years. Methods for obtaining high-order modes include direct intracavity generation and laser mode conversion. Among them, the direct intracavity generation method uses the oscillation of high-order mode lasers in the laser resonant cavity and outputs high-order mode lasers. However, due to the high proportion of fundamental mode lasers in the laser, the conditions for high-order mode oscillations are harsh and the mode order cannot be precisely controlled, so the laser mode purity obtained by the direct intracavity generation method is low and the laser output efficiency is low. The laser mode conversion method uses a mode converter to convert the laser fundamental mode (TEM 00 ) into a higher-order Hermitian Gaussian mode or Laguerre Gaussian mode, resulting in lasers of different modes. Currently, laser mode conversion methods typically employ laser mode converters. Common laser mode converters utilize optical phase matching technology to create liquid crystal polymer films with different fast-axis distributions on the surface of a glass substrate. The optical path difference (or phase difference) between ordinary light (o-light) and extraordinary light (e-light) is controlled by precisely controlling the thickness of the liquid crystal polymer, thereby achieving conversion between different modes. However, this type of laser mode converter can only be applied to high-order mode lasers of a specific wavelength and order, and cannot achieve compatibility with multiple wavelengths and multiple high-order mode lasers.

[0003] The development of laser mode converters that are compatible with multiple wavelengths and multiple high-order mode lasers is of great significance to the progress in fields such as laser communications and life sciences. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a three-mirror ring cavity laser mode converter. By adjusting the position of the plano-concave high-reflection mirror or the laser, and then adjusting the cavity length and structure of the three-mirror ring cavity, the circulating light path forms a cavity mode with a target cavity length in the three-mirror ring cavity, so as to achieve the output of the target high-order mode laser that matches the cavity mode, thereby solving the laser mode conversion problem in the existing technology that is not compatible with multiple wavelengths and multiple high-order mode lasers, and improving the efficiency of laser mode conversion.

[0005] The present application provides a three-mirror ring cavity laser mode converter, comprising a plano-concave high-reflection mirror, a first output mirror, a second output mirror, and a laser. The plano-concave high-reflection mirror, the first output mirror, and the second output mirror form a three-mirror ring cavity. A fundamental mode beam emitted by the laser is incident into the three-mirror ring cavity through the first output mirror, forming a closed circulating optical path in the three-mirror ring cavity. The position of the plano-concave high-reflection mirror is adjustable in a direction perpendicular to the fundamental mode beam, and the position of the laser is capable of translation or tilt relative to the three-mirror ring cavity. After either the position of the plano-concave high-reflection mirror or the position of the laser is adjusted, the circulating optical path forms a cavity mode with a target cavity length in the three-mirror ring cavity, thereby achieving output of a target high-order mode laser that matches the cavity mode.

[0006] Furthermore, the plano-concave high-reflection mirror is a total-reflection mirror used to totally reflect lasers of different modes. The plano-concave high-reflection mirror is constructed as a plano-concave mirror with a flat first side and a concave second side. The concave surface is coated with a film system with high reflectivity to lasers. The concave surface of the plano-concave high-reflection mirror is arranged facing the inside of the three-mirror annular cavity, and the first side and the second side are two opposite sides.

[0007] Furthermore, the first output mirror and the second output mirror are both plane mirrors.

[0008] Furthermore, the first output mirror and the second output mirror have the same amplitude reflectivity.

[0009] Furthermore, the first output mirror and the second output mirror have different transmittances for lasers of different modes, and the transmittances of the first output mirror and the second output mirror are related to the material of the output mirrors and the degree of translation of the incident laser.

[0010] Furthermore, when the position of the laser is translated or tilted relative to the three-mirror ring cavity, the fundamental mode beam emitted by the laser excites a high-order Hermite-Gaussian mode under the three-mirror ring cavity. When the fundamental mode beam emitted by the laser is incident with an offset distance d, the fundamental mode beam is incident on the Hermite-Gaussian coordinate basis vector {u n (x)}, it is expressed as:

[0011]

[0012] In the formula is the proportional coefficient of the excited n-th order mode.

[0013] The condition for the excited mode to resonate in the three-mirror ring cavity is that the total phase shift around one circle is an integer multiple of 2π, that is, the total phase shift φ n , meeting the conditions:

[0014]

[0015] Where m is an integer, L n is the length of the resonant cavity, Z = L n / 2 is half of the length of the resonant cavity, is the sharp length, λ is the laser wavelength, is the waist spot of the fundamental mode in the laser cavity, R is the curvature radius of the concave mirror, and L is the cavity length corresponding to the fundamental mode.

[0016] Furthermore, according to the principle of multi-beam interference and Gaussian beam mode matching, it can be obtained that after the fundamental mode beam emitted by the laser is translated, the transmittance of the first output mirror and the second output mirror is:

[0017]

[0018] Where T n is the projection ratio coefficient of the n-th order mode, and r is the amplitude reflectivity of the light field.

[0019] Furthermore, the layout of the three-mirror annular cavity is a straight line, a triangle or other geometric shapes that allow the laser to form a stable circulating closed path in the cavity.

[0020] Furthermore, the converter also includes a first laser detector and a second laser detector, the first laser detector is configured close to the first output mirror, and the second laser detector is configured close to the second output mirror, and the first laser detector and the second laser detector are used to detect the light field distribution and laser power of the output high-order mode laser.

[0021] Furthermore, the converter further includes a position regulator, which is arranged facing the plane of the plano-concave high-reflection mirror, and is used to adjust the position of the plano-concave high-reflection mirror along a direction perpendicular to the incident laser.

[0022] The utility model adopts a phase mismatch excitation method to generate Hermite-Gaussian mode laser, and utilizes the principle that the phase mismatch of the fundamental mode Gaussian beam will excite the higher-order Hermite-Gaussian mode. By adjusting the position of the plano-concave high-reflection mirror or the laser, the cavity length and structure of the three-mirror ring cavity are adjusted, so that the circulating light path forms a cavity mode with a target cavity length in the three-mirror ring cavity, so as to realize the output of the target high-order mode laser that matches the cavity mode. This solves the laser mode conversion problem of the prior art that is incompatible with multiple wavelengths and multiple high-order mode lasers, and improves the efficiency of laser mode conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0024] Figure 1 This is the schematic diagram of a three-mirror ring cavity laser mode converter;

[0025] Figure 2 This is a structural diagram of a three-mirror ring cavity laser mode converter;

[0026] In the figure, 1 is a plano-concave high-reflection mirror, 2 is a first output mirror, 3 is a second output mirror, 4 is a laser, 5 is a first laser detector, 6 is a second laser detector, and 7 is a position regulator. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The present application provides a three-mirror ring cavity laser mode converter. By adjusting the position of the plano-concave high-reflection mirror 1 or the laser 4, and then adjusting the structure of the three-mirror ring cavity, the circulating light path forms a cavity mode with a target cavity length in the three-mirror ring cavity, so as to achieve the output of the target high-order mode laser that matches the cavity mode. This solves the laser mode conversion problem in the prior art that is incompatible with multiple wavelengths and multiple high-order mode lasers, and improves the efficiency of laser mode conversion.

[0029] Specifically, such as Figures 1 to 2 As shown, the converter includes a plano-concave high-reflection mirror 1, a first output mirror 2, a second output mirror 3 and a laser 4. The plano-concave high-reflection mirror 1, the first output mirror 2 and the second output mirror 3 form a three-mirror ring cavity. The fundamental mode light beam emitted by the laser 4 is incident on the three-mirror ring cavity through the first output mirror 2, forming a closed circulating light path in the three-mirror ring cavity. The position of the plano-concave high-reflection mirror 1 is adjustable in a direction perpendicular to the fundamental mode light beam, and the position of the laser 4 can be translated or tilted relative to the three-mirror ring cavity. When either the position of the plano-concave high-reflection mirror 1 or the position of the laser 4 is adjusted, the circulating light path forms a cavity mode with a target cavity length in the three-mirror ring cavity, thereby achieving the output of a target high-order mode laser that matches the cavity mode.

[0030] It is understood that the principle of laser mode selection and conversion is based on the interference effect of light. In a three-mirror ring cavity, the fundamental mode beam will produce superposition during multiple reflections within the cavity, forming stable standing wave patterns. These modes are determined by factors such as the cavity length, the curvature and position of the plano-concave high-reflectivity mirrors, etc. Therefore, by adjusting the geometric parameters of the three-mirror ring cavity, the phase matching conditions of different modes can be changed, thereby selectively enhancing or suppressing certain modes. The circulating light path forms a cavity mode with a target cavity length in the three-mirror ring cavity, thereby achieving the target high-order mode laser output that matches the cavity mode.

[0031] Furthermore, the plano-concave high-reflection mirror 1 is a total reflective mirror. In some embodiments, the plano-concave high-reflection mirror 1 is constructed as a plano-concave mirror with a flat first side and a concave second side. The concave surface of the plano-concave high-reflection mirror 1 is arranged facing the three-mirror annular cavity, and the concave surface is coated with a film system with high reflectivity to laser, which is used to totally reflect lasers of different modes; wherein the first side and the second side are two opposite sides. It can be understood that by coating the concave surface of the plano-concave high-reflection mirror 1 with a film system with high reflectivity to laser, high reflectivity of lasers of different modes can be achieved, thereby reducing laser loss.

[0032] In some embodiments, the first output mirror 2 and the second output mirror 3 are both plane mirrors.

[0033] In some embodiments, the amplitude reflectivity of the first output mirror 2 and the second output mirror 3 are the same.

[0034] In some embodiments, the first output mirror 2 and the second output mirror 3 have different transmittances for lasers of different modes. The transmittances of the first output mirror 2 and the second output mirror 3 are related to the material of the output mirrors and the degree of translation of the incident fundamental mode light beam.

[0035] In some embodiments, combined Figure 1 The transmittance of the first output mirror 2 and the second output mirror 3 is calculated as follows: when the position of the laser 4 is translated or tilted relative to the three-mirror ring cavity, the fundamental mode beam emitted by the laser 4 excites a high-order Hermite-Gaussian mode in the three-mirror ring cavity. When the fundamental mode beam emitted by the laser 4 is incident with an offset distance of d, it is expanded in the Hermite-Gaussian coordinate basis vector and expressed as:

[0036]

[0037] In the formula is the proportional coefficient of the excited n-th order mode.

[0038] The condition for the excited mode to resonate in the three-mirror ring cavity is that the total phase shift around one circle is an integer multiple of 2π, that is, the total phase shift φ n , meeting the conditions:

[0039]

[0040] Where m is an integer, L n is the length of the resonant cavity, Z = L n / 2 is half of the length of the resonant cavity, is the sharp length, λ is the laser wavelength, is the waist spot of the fundamental mode in the laser cavity, R is the curvature radius of the concave mirror, and L is the cavity length corresponding to the fundamental mode.

[0041] According to the principle of multi-beam interference and Gaussian beam mode matching, it can be obtained that after the fundamental mode beam emitted by laser 4 is translated, the transmittance of the first output mirror 2 and the second output mirror 3 is:

[0042]

[0043] Where T n is the projection ratio coefficient of the n-th order mode, and r is the amplitude reflectivity of the light field.

[0044] In the above embodiment, combined with Figure 1 The principle of the three-mirror ring cavity laser mode converter to form a cavity mode with a target cavity length and achieve the target high-order mode laser output matching the cavity mode is as follows:

[0045] A plano-concave high-reflection mirror 1, a first output mirror 2 and a second output mirror 3 form a three-mirror ring cavity. The first output mirror 2 and the second output mirror 3 are arranged up and down, the plano-concave high-reflection mirror 1 is arranged on one side of the output mirror, and the concave surface of the plano-concave high-reflection mirror 1 is arranged facing the three-mirror ring cavity. A laser 4 is arranged below the first output mirror 2. The fundamental mode light beam emitted by the laser 4 enters the three-mirror ring cavity through the first output mirror 2. The fundamental mode light beam is circularly reflected between the first output mirror 2, the second output mirror 3 and the plano-concave high-reflection mirror 1, and then forms a closed circular optical path in the three-mirror ring cavity. When the laser 4 is translated to cause the fundamental mode light beam emitted by the laser to be translated by a distance d, the fundamental mode originally matched with the cavity mode excites a high-order Hermite Gauss mode in the eigensystem of the cavity. By locking the target cavity length, the Hermite Gauss mode of the target order is obtained, and the output of the target high-order mode laser matching the cavity mode is achieved.

[0046] In another embodiment, the converter further includes a position regulator 7, which is arranged facing the plane of the plano-concave high-reflection mirror 1 and is used to adjust the position of the plano-concave high-reflection mirror 1 along a direction perpendicular to the fundamental mode light beam.

[0047] In the above embodiment, combined with Figure 2 The principle of the three-mirror ring cavity laser mode converter to form a cavity mode with a target cavity length and achieve the target high-order mode laser output matching the cavity mode is as follows:

[0048] A plano-concave high-reflection mirror 1, a first output mirror 2 and a second output mirror 3 form a three-mirror ring cavity. The first output mirror 2 and the second output mirror 3 are arranged up and down, the plano-concave high-reflection mirror 1 is arranged on one side of the output mirror, and the concave surface of the plano-concave high-reflection mirror 1 faces the three-mirror ring cavity. A position regulator 7 is provided on the plane side of the plano-concave high-reflection mirror 1. A laser 4 is provided below the first output mirror 2. The fundamental mode light beam emitted by the laser 4 enters the three-mirror ring cavity through the first output mirror 2. The fundamental mode light beam is circularly reflected between the first output mirror 2, the second output mirror 3 and the plano-concave high-reflection mirror 1, and then forms a closed circular optical path in the three-mirror ring cavity. When the position of the plano-concave high-reflection mirror 1 is adjusted in a direction perpendicular to the fundamental mode light beam by the position regulator 7, the cavity length and structure of the three-mirror ring cavity can be adjusted. By locking the target cavity length, the target order Hermite-Gauss mode is obtained, and the output of the target high-order mode laser matching the cavity mode is achieved.

[0049] Furthermore, in the above embodiment, continue to refer to Figure 2 The converter also includes a first laser detector 5 and a second laser detector 6. The first laser detector 5 is configured close to the first output mirror 2, and the second laser detector 6 is configured close to the second output mirror 3. The first laser detector 5 and the second laser detector 6 are used to detect the light field distribution and laser power of the output high-order mode laser.

[0050] Furthermore, the layout of the three-mirror annular cavity is a straight line, a triangle or other geometric shapes that allow the laser to form a stable circulating closed path in the cavity.

[0051] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and improvements fall within the scope of the present invention as claimed.

Claims

1. A three-mirror ring cavity laser mode converter, characterized in that: The invention comprises a plano-concave high-reflection mirror (1), a first output mirror (2), a second output mirror (3) and a laser (4); the plano-concave high-reflection mirror (1), the first output mirror (2) and the second output mirror (3) form a three-mirror ring cavity; a fundamental mode light beam emitted by the laser (4) is incident into the three-mirror ring cavity through the first output mirror (2), and a closed circulating light path is formed in the three-mirror ring cavity; the position of the plano-concave high-reflection mirror (1) is adjustable in a direction perpendicular to the fundamental mode light beam; the position of the laser (4) can be translated or tilted relative to the three-mirror ring cavity; after either the position of the plano-concave high-reflection mirror (1) or the position of the laser (4) is adjusted, the circulating light path forms a cavity mode with a target cavity length in the three-mirror ring cavity, so as to achieve the output of a target high-order mode laser matching the cavity mode.

2. The three-mirror ring cavity laser mode converter according to claim 1, characterized in that: The plano-concave high-reflection mirror (1) is a total reflection mirror used for totally reflecting lasers of different modes. The plano-concave high-reflection mirror (1) is constructed as a plano-concave mirror with a first side surface being a plane and a second side surface being a concave surface. The concave surface is coated with a film system having a high reflectivity for lasers. The concave surface of the plano-concave high-reflection mirror (1) is arranged facing the inside of the three-mirror annular cavity, and the first side surface and the second side surface are two opposite side surfaces.

3. The three-mirror ring cavity laser mode converter according to claim 1 or 2, characterized in that: The first output mirror (2) and the second output mirror (3) are both plane mirrors.

4. The three-mirror ring cavity laser mode converter according to claim 2, characterized in that: The first output mirror (2) and the second output mirror (3) have the same amplitude reflectivity.

5. The three-mirror ring cavity laser mode converter according to claim 4, characterized in that: The first output mirror (2) and the second output mirror (3) have different transmittances for lasers of different modes, and the transmittances of the first output mirror (2) and the second output mirror (3) are related to the material of the output mirrors and the degree of translation of the incident fundamental mode light beam.

6. The three-mirror ring cavity laser mode converter according to claim 5, characterized in that: When the position of the laser (4) is translated or tilted relative to the three-mirror ring cavity, the fundamental mode light beam emitted by the laser (4) excites a high-order Hermite-Gaussian mode under the three-mirror ring cavity, and when the fundamental mode light beam emitted by the laser (4) is incident with an offset distance d, the Hermite-Gaussian coordinate basis vector {u n (x)}, it is expressed as: In the formula is the proportional coefficient of the excited n-th order mode; The condition for the excited mode to resonate in the three-mirror ring cavity is that the total phase shift around one circle is an integer multiple of 2π, that is, the total phase shift φ n , meeting the conditions: Where m is an integer, L n is the length of the resonant cavity, Z = L n / 2 is half of the length of the resonant cavity, is the sharp length, λ is the laser wavelength, is the waist spot of the fundamental mode in the laser cavity, R is the curvature radius of the concave mirror, and L is the cavity length corresponding to the fundamental mode.

7. The three-mirror ring cavity laser mode converter according to claim 1, characterized in that: According to the principle of multi-beam interference and Gaussian beam mode matching, it can be obtained that after the fundamental mode beam emitted by the laser (4) is translated, the transmittance of the first output mirror (2) and the second output mirror (3) is: Where T n is the projection ratio coefficient of the n-th order mode, and r is the amplitude reflectivity of the light field.

8. The three-mirror ring cavity laser mode converter according to claim 1, wherein: The layout of the three-mirror annular cavity is a straight line, a triangle or other geometric shapes that allow the laser to form a stable circulating closed path in the cavity.

9. The three-mirror ring cavity laser mode converter according to claim 2, characterized in that: The converter further comprises a first laser detector (5) and a second laser detector (6), wherein the first laser detector (5) is arranged close to the first output mirror (2), and the second laser detector (6) is arranged close to the second output mirror (3), and the first laser detector (5) and the second laser detector (6) are used to detect the light field distribution and laser power of the output high-order mode laser.

10. The three-mirror ring cavity laser mode converter according to claim 2, characterized in that: The converter further comprises a position regulator (7), which is arranged facing the plane of the plano-concave high-reflection mirror (1), and is used to adjust the position of the plano-concave high-reflection mirror (1) along a direction perpendicular to the incident fundamental mode light beam.

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