A one-dimensional virtual confocal unstable laser resonator with partial transmittance

Abstract

This invention provides a one-dimensional virtual confocal unstable laser resonator with partial transmittance. The invention includes a convex cylindrical mirror and a concave cylindrical mirror. The convex cylindrical mirror has a convex cylindrical surface facing the cavity interior, and the concave cylindrical mirror has a concave cylindrical surface facing the cavity interior. The convex cylindrical surface of the convex cylindrical mirror and the concave cylindrical surface of the concave cylindrical mirror are opposite each other. A dielectric film with partial transmittance for the laser wavelength is partially deposited on the convex cylindrical surface of the convex cylindrical mirror, and a dielectric film with a preset reflectivity for the laser wavelength is deposited on the concave cylindrical surface of the concave cylindrical mirror. When both satisfy the cavity formation conditions of the laser resonator, energy is extracted from the laser gain medium to form laser light, which is then output from the convex cylindrical mirror. The one-dimensional unstable laser resonator provided by this invention has advantages such as simple and compact structure, easy collimation adjustment, and convenient application in practical engineering.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more particularly to a one-dimensional virtual confocal unstable laser resonator with partial transmittance. Background Technology

[0002] The laser resonator is a crucial component in a laser for energy extraction, and its design significantly impacts key performance indicators such as output power, efficiency, and beam quality. To achieve good output beam quality while balancing output power and efficiency, designers often employ unstable cavity designs in lasers. The virtual confocal unstable cavity, a type of laser resonator, produces a parallel beam with excellent beam quality. Furthermore, the absence of a real focal point in this resonator helps protect the laser and prevents damage to the laser gain medium caused by laser focusing.

[0003] In lasers utilizing this cavity type, the laser energy is typically output through an in-cavity scraper mirror. As a coupling output element, the introduction of the scraper mirror often complicates the fabrication and collimation adjustment of the actual device. Furthermore, as an optical element with a tilted aperture, the scraper mirror is often difficult to fabricate; and maintaining the working surface profile during fabrication is challenging, potentially compromising the beam quality of the virtual confocal unstable cavity.

[0004] A typical two-dimensional virtual confocal unstable cavity uses a spherical surface as the working surface of the laser resonator, exhibiting equal amplification in all dimensions. This makes it unsuitable for laser media requiring different amplification in different directions. In conventional virtual confocal unstable cavities, both the convex and concave spherical surfaces are coated with a high-reflectivity dielectric film specific to the laser wavelength. The equivalent coupling ratio of the laser output light is entirely determined by the ratio of the radii of curvature of the two mirrors, lacking adjustability. In some lasers where different amplification in two dimensions is desired, the traditional virtual confocal unstable cavity, with its equal amplification, is clearly unsuitable.

[0005] For low-gain lasers, to achieve high power and high beam quality output, conventional virtual confocal unstable cavities can only be designed with a lower amplification. In this case, the output light is a thin hollow ring. Due to the diffraction effect, the energy concentration is greatly reduced, which will lead to insufficient brightness of the far-field spot of the laser and limit the practical application of the laser. Summary of the Invention

[0006] To address the shortcomings of traditional two-dimensional amplified virtual confocal unstable laser resonators in terms of fabrication, adjustment, and applicability, this invention provides a one-dimensional virtual confocal unstable laser resonator with partial transmittance. This invention aims to solve the problems of difficult scraper mirror fabrication, high adjustment difficulty, and potential beam quality degradation due to poor surface shape in existing two-dimensional virtual confocal unstable cavities. The technical means employed in this invention are as follows:

[0007] A one-dimensional virtual confocal unstable laser resonator with partial transmittance includes a convex cylindrical mirror and a concave cylindrical mirror. The convex cylindrical mirror has a convex cylindrical surface facing the cavity interior, and the concave cylindrical mirror has a concave cylindrical surface facing the cavity interior. The convex cylindrical surface of the convex cylindrical mirror and the concave cylindrical surface of the concave cylindrical mirror are opposite each other. A dielectric film with partial transmittance for the laser wavelength is partially deposited on the convex cylindrical surface of the convex cylindrical mirror, and a dielectric film with a preset reflectance for the laser wavelength is deposited on the concave cylindrical surface of the concave cylindrical mirror. When both satisfy the cavity formation conditions of the laser resonator, energy is extracted from the laser gain medium to form laser light, which is then output from the convex cylindrical mirror.

[0008] Furthermore, on the convex cylindrical surface of the mirror, an optical thin film with a certain transmittance for the laser wavelength is deposited in a rectangular area of ​​a certain width in the middle, and laser dielectric films with a preset transmittance are deposited on both sides.

[0009] Furthermore, the radius of curvature R2 of the concave cylindrical surface of the concave cylindrical mirror is related to the radius of curvature R1 of the convex cylindrical surface of the convex cylindrical mirror in that half the difference between the two is equal to the cavity length L of the laser resonant cavity.

[0010] Furthermore, the convex cylindrical reflector and the concave cylindrical reflector include rectangular shapes.

[0011] Furthermore, the amplification M of the laser resonant cavity satisfies the following relationship:

[0012]

[0013] Wherein, R2 is the radius of curvature of the concave cylindrical surface of the concave cylindrical mirror, and R1 is the radius of curvature of the convex cylindrical surface of the convex cylindrical mirror.

[0014] The width of the laser dielectric film with transmittance in the rectangular region of the convex cylindrical surface of the convex cylindrical mirror is a. The width A of the concave cylindrical mirror is not less than Ma, that is, A≥Ma.

[0015] Furthermore, the non-working surface of the convex cylindrical reflector facing outwards from the cavity is a plane or a curved surface of equal thickness to the cylindrical surface, and its surface is not coated or is coated with a dielectric film with a preset transmittance for the laser wavelength.

[0016] Furthermore, the convex cylindrical reflector and the concave cylindrical reflector are aligned along the same spatial dimension, that is, the cylindrical surface of the convex cylindrical reflector is vertical, and the cylindrical surface of the concave cylindrical reflector is also vertical; or, the cylindrical surface of the convex cylindrical reflector is horizontal, and the cylindrical surface of the concave cylindrical reflector is also horizontal; the spatial dimension includes, but is not limited to, the horizontal and vertical directions.

[0017] Furthermore, unstable laser resonators can be used in solid-state laser gain media, gaseous laser gain media, or liquid laser gain media.

[0018] In this invention, a one-dimensional virtual confocal unstable laser resonator, when pre-defined cavity formation conditions are met, exhibits a beam width amplified by reflection from a convex cylindrical mirror. Upon transmission to a concave cylindrical mirror, the beam is reflected again. Part of the light irradiates a partially transmissive thin film on the mirror surface, part is reflected back into the laser resonator, and the remaining energy is output outside the cavity. Light irradiating the convex cylindrical mirror beyond the partially transmissive film is directly output outside the cavity via an anti-reflection film, serving as the laser output. Therefore, the output laser beam consists of two parts: one part is formed by the partially transmissive laser dielectric film at the center of the convex cylindrical mirror, and the other part is formed by the anti-reflection films on both sides of the convex cylindrical mirror. This invention reduces the intracavity power density of the laser, which is beneficial for protecting the laser's safe operation. Converting the output light into a solid spot improves the far-field brightness of this type of laser, facilitating its further practical application. Attached Figure Description

[0019] 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.

[0020] Figure 1 The embodiment of the present invention provides a one-dimensional virtual confocal unstable laser resonator structure with partial transmittance.

[0021] Figure 2 This is a schematic diagram of the convex cylindrical surface in the one-dimensional virtual confocal unstable laser resonator of the present invention.

[0022] In the figure: 1. Convex cylindrical mirror; 2. Concave cylindrical mirror; 1.1. Working surface of convex cylindrical mirror; 1.2. Non-working surface of convex cylindrical mirror. Detailed Implementation

[0023] 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, not all embodiments. 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.

[0024] This invention overcomes the shortcomings of conventional virtual confocal unstable laser resonators, such as the difficulty in processing the scraper mirror, inconvenient adjustment, difficulty in ensuring surface accuracy, and easy damage to beam quality. It provides a virtual confocal unstable laser resonator with partial output coupling and a pair of cylindrical mirrors to achieve one-dimensional laser amplification. Figure 1 , Figure 2 This is a structural diagram of a one-dimensional virtual confocal unstable laser resonator provided in an embodiment of the present invention. For ease of explanation, only the cavity structure portion relevant to the present invention is shown, and is described in detail below:

[0025] This embodiment discloses a one-dimensional virtual confocal unstable laser resonator with partial transmittance, comprising a convex cylindrical mirror 1 and a concave cylindrical mirror 2. The surface of the convex cylindrical mirror facing the cavity interior is a convex cylindrical surface 1.1, and the surface of the concave cylindrical mirror facing the cavity interior is a concave cylindrical surface. The convex and concave cylindrical surfaces are one of the working surfaces. The convex cylindrical surface of the convex cylindrical mirror and the concave cylindrical surface of the concave cylindrical mirror are opposite each other. A dielectric film with partial transmittance for the laser wavelength is partially deposited on the convex cylindrical surface of the convex cylindrical mirror to allow the laser to pass through. A dielectric film with a preset reflectivity for the laser wavelength is deposited on the concave cylindrical surface of the concave cylindrical mirror. When both satisfy the cavity formation conditions of the laser resonator, energy is extracted from the laser gain medium to form a laser beam, which is output from the convex cylindrical mirror. The output beam is a solid beam.

[0026] On the convex cylindrical surface of the mirror, different laser dielectric films are deposited in different areas. Specifically, a laser dielectric film with a certain transmittance for the laser wavelength is deposited in a rectangular area of ​​a certain width in the middle of the cylindrical surface, and laser dielectric films with a preset transmittance are deposited on both sides.

[0027] The convex cylindrical mirror and the concave cylindrical mirror satisfy the cavity formation condition as follows: (1) The radius of curvature of the concave cylindrical surface of the concave cylindrical mirror is R2, and its relationship with the radius of curvature of the convex cylindrical surface of the convex cylindrical mirror is: half of the difference between the two is equal to the cavity length L of the laser resonant cavity, that is

[0028] The shapes of the convex cylindrical reflector and the concave cylindrical reflector include, but are not limited to, rectangles.

[0029] The amplification M of the laser resonant cavity satisfies the following relationship:

[0030]

[0031] Wherein, R2 is the radius of curvature of the concave cylindrical surface of the concave cylindrical mirror, and R1 is the radius of curvature of the convex cylindrical surface of the convex cylindrical mirror.

[0032] The width of the laser dielectric film with transmittance in the rectangular region of the convex cylindrical surface of the convex cylindrical mirror is a. The width A of the concave cylindrical mirror is not less than Ma, that is, A≥Ma.

[0033] The non-working surface 1.2 of the convex cylindrical reflector facing outwards from the cavity is a plane or a curved surface of equal thickness to the cylindrical surface. Its surface is not coated or is coated with a dielectric film with a preset transmittance for the laser wavelength, so that the laser can pass through.

[0034] (2) The convex cylindrical reflector and the concave cylindrical reflector are along the same spatial dimension, that is, the cylindrical surface of the convex cylindrical reflector is along the vertical direction, and the cylindrical surface of the concave cylindrical reflector is also along the vertical direction; or, the cylindrical surface of the convex cylindrical reflector is along the horizontal direction, and the cylindrical surface of the concave cylindrical reflector is also along the horizontal direction; the spatial dimension includes, but is not limited to, the horizontal direction and the vertical direction.

[0035] (3) The collimation condition between the working surfaces of the two cylindrical mirrors is met, that is, in addition to the two working cylindrical surfaces having a common virtual confocal focus, the optical axes of the two lenses coincide.

[0036] Unstable laser resonators can be used in solid-state laser gain media, gaseous laser gain media, or liquid laser gain media.

[0037] In practical applications, when this cavity operates under the aforementioned cavity formation conditions, the spontaneously generated laser beam within the cavity is partially reflected by a partially transmissive reflective film on the convex cylindrical mirror 1, amplifying the beam width. The width of this partially transmissive reflective film is 'a'. When transmitted to the concave cylindrical mirror 2, its longitudinal width becomes 'A'. The light, reflected again by the concave cylindrical mirror and irradiating onto the convex cylindrical mirror 1, is partially reflected back into the laser resonant cavity, while the remaining portion serves as the laser output outside the cavity. The portion of the light irradiating onto the convex cylindrical mirror 1, located outside the middle portion of the transmissive film, is directly output through the antireflective film and also serves as the laser output. Therefore, the output laser consists of two parts: one part is formed by transmission through the middle portion of the convex cylindrical mirror, and the other part is directly formed through the antireflective films on both sides of the cylindrical mirror.

[0038] 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 one-dimensional virtual confocal unstable laser resonator with partial transmission, characterized in that, The convex cylindrical mirror and the concave cylindrical mirror, the convex cylindrical mirror is convex cylindrical towards the cavity inner surface, the concave cylindrical mirror is concave cylindrical towards the cavity inner surface, the convex cylindrical surface of the convex cylindrical mirror is opposite to the concave cylindrical surface of the concave cylindrical mirror, the convex cylindrical surface of the convex cylindrical mirror is partially coated with a dielectric film with partial transmittance for laser wavelength, the concave cylindrical surface of the concave cylindrical mirror is coated with a dielectric film with preset reflectivity for laser wavelength, when both satisfy the cavity condition of laser resonator, energy is extracted from the laser gain medium, laser is formed and output from the convex cylindrical mirror; The convex cylindrical surface of the convex cylindrical mirror is coated with optical film with certain transmittance for laser wavelength in a middle certain width rectangular area, both sides are coated with laser dielectric film with preset transmittance; The concave cylindrical surface of the concave cylindrical mirror has a radius of curvature R 2. The relationship between the convex cylindrical surface radius of curvature of the convex cylindrical mirror R 1 is that half the difference between the two is equal to the resonator cavity length of the laser L i.e. ; The magnification M of the laser resonator satisfies the following relationship: wherein R 2 is the radius of curvature of the concave cylindrical surface of the concave cylindrical mirror, R 1 is the convex cylindrical radius of the convex cylindrical mirror; The convex cylindrical mirror has a convex cylindrical middle rectangular area plated with a partial-transmittance laser medium film with a width of a, and the width A of the concave cylindrical mirror is not less than Ma, i.e. ; The convex cylindrical mirror and the concave cylindrical mirror include rectangular shape; The non-working surface of the convex cylindrical mirror towards the cavity outer surface is planar or curved surface with equal thickness with the cylindrical surface, the surface is not coated or coated with dielectric film with preset transmittance for laser wavelength; The convex cylindrical mirror surface and the concave cylindrical mirror surface are along the same spatial dimension direction, i.e. the cylindrical surface of the convex cylindrical mirror is along the vertical direction, the cylindrical surface of the concave cylindrical mirror is also along the vertical direction, or the cylindrical surface of the convex cylindrical mirror is along the horizontal direction, the cylindrical surface of the concave cylindrical mirror is also along the horizontal direction, the spatial dimension direction includes but is not limited to the horizontal direction and the vertical direction; The unstable laser resonator is used for solid laser gain medium, gaseous laser gain medium or liquid laser gain medium.

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