Spatial light coupling device and method

Abstract

This invention provides a spatial optical coupling device and method, belonging to the field of spatial optical coaxial coupling technology. It includes: a ring light generating unit for refracting a first parallel beam with a first frequency band to generate a parallel ring beam; and a first parallel light generating unit, coaxially arranged with the ring light generating unit along the principal optical axis, and located in the hollow region of the parallel ring beam, for generating a second parallel beam with a second frequency band. The second parallel beam and the parallel ring beam constitute a parallel solid beam with both the first and second frequency bands. Beneficial effects: Enables unobstructed, low-loss, high-precision, and scalable coaxial beam combining of multiple spatial light beams.

Description

Technical Field

[0001] This invention relates to the field of spatial optical coaxial coupling technology, and more particularly to a spatial optical coupling device and method. Background Technology

[0002] Beam-splitter / polarizer-level beam combining technology mainly consists of collimating elements, beam-combining elements, polarization control elements, reflection elements, and adjustment mechanisms. The collimating elements typically employ convex lenses or off-axis parabolic mirrors, and their number matches the number of beams to be combined. Each collimating element is aligned with its corresponding divergent light source, ensuring that the divergent light output from the source can be incident on the collimating element and converted into parallel light. The beam-combining elements use semi-transparent, semi-reflective beam splitters, one fewer than the number of beams to be combined. All beam splitters are arranged in a stepped configuration, with each beam splitter tilted at 45°. This allows one path of parallel light to pass through the beam splitter along its original propagation direction, while the other path of parallel light is reflected by the beam splitter and its propagation direction is changed. The beams are initially combined with the transmitted light. Subsequent beam splitters are cascaded along the propagation path of the previously combined beams, combining the newly added parallel light with the previous beams through transmission and reflection. The reflection and transmission axes of all beam splitters must be strictly collinear to ensure the coaxiality of the final output combined beam, achieving composite beam combining of transmission and reflection. Polarization control elements are configured with polarizers or waveplates as needed to adjust the polarization state of each beam to improve beam combining efficiency. The reflection element is a plane mirror used to change the beam propagation direction to adapt to the cascaded beam combining structure. The adjustment mechanism uses multiple two-dimensional or three-dimensional adjustment frames to fine-tune the angles of each element to ensure the coaxiality of the beams during beam combining.

[0003] Based on the aforementioned beam-splitting mirror-level combined beam technology, there are many inherent problems in its practical applications. These problems stem from the limitations of the technical architecture design and working principle, and cannot be avoided through local optimization. The specific manifestations and underlying reasons are as follows: First, beam obstruction is severe and energy loss accumulates significantly. The core reason lies in the semi-transparent and semi-reflective working principle of the beam splitter, which needs to be placed directly in the beam propagation path. Each stage of beam combining will distribute the incident light through transmission and reflection, which not only fails to achieve 100% energy transfer, but also generates additional losses due to mirror reflection, absorption, and polarization mismatch. At the same time, the cascaded structure causes the losses to accumulate step by step. The more beams combined, the higher the total loss. In essence, this technology sacrifices energy for beam combining function, which contradicts the requirement of high energy utilization.

[0004] Secondly, the number of beams that can be combined is limited. On the one hand, the beam splitter in the later stage needs to carry both the beams combined in the previous stage and the newly added beams. Increasing the number of beams inevitably requires the size of the beam splitter to be increased accordingly. Due to limitations in equipment installation space and manufacturing costs, the actual number of beams combined is difficult to exceed 4. On the other hand, each additional beam requires an additional set of collimating and combining elements. The cumulative error of optical axis calibration increases exponentially, making it impossible to guarantee the coaxiality of multiple beams. This is an inherent defect of the stepped cascade architecture.

[0005] Third, coaxiality control is difficult and unstable. Because there is no unified optical axis reference, the installation angle and position of each beam splitter need to be calibrated independently. Small deviations are amplified after being transmitted through multiple stages, and environmental vibrations and temperature changes can easily cause component displacement, further damaging coaxiality. At the same time, the adjustment mechanism can only achieve fine adjustment of individual components and lacks a global calibration mechanism, which cannot compensate for accumulated errors. The root cause lies in the decentralized design of the cascaded structure.

[0006] Fourth, it has poor adaptability to special bands such as terahertz. The transmission / reflection efficiency of a beam splitter is strongly related to the material and coating process. Existing optical materials and coating technologies are difficult to achieve efficient energy transfer in the terahertz band, and are prone to severe attenuation. Moreover, the wavelength of terahertz beams is relatively long, and the size of the beam splitter needs to be further increased, which exacerbates the contradiction between installation space and coaxiality control. Essentially, this technology is designed for visible and near-infrared light and is not adapted to the characteristics of special bands. Summary of the Invention

[0007] To address the above technical problems, the present invention provides a spatial optical coupling device; on the other hand, it also provides a spatial optical coupling method.

[0008] The technical problem solved by this invention can be achieved by the following technical solutions: A spatial optical coupling device, comprising: A ring light generating unit is used to refract a first parallel beam with a first frequency band to generate a parallel ring beam. A first parallel light generating unit is arranged coaxially with the ring light generating unit along the main optical axis, and the first parallel light generating unit is located in the hollow region of the parallel ring beam. It is used to generate a second parallel beam with a second frequency band. The second parallel beam and the parallel ring beam constitute a parallel solid beam with the first frequency band and the second frequency band.

[0009] The spatial optical coupling device of the present invention comprises a first-order beam combiner group consisting of a ring light generating unit and a first parallel light generating unit. The beam combiner group includes multiple orders, all of which have the same structure. Adjacent beam combiner groups also include: The beam shrinking mirror group is located between the output end of the first parallel light generating unit of the previous beam combiner group and the input end of the ring light generating unit of the next beam combiner group. It is used to refract the parallel solid beam generated by the previous beam combiner group to generate a beam combined with a reduced beam. The ring light generating unit in the next-order beam combiner is used to refract the combined beam to generate a corresponding parallel ring beam.

[0010] In the spatial optical coupling device of the present invention, the second parallel beam generated by the first parallel light generating unit in the multi-stage beam combining mirror group has different frequency bands.

[0011] The spatial light coupling device of the present invention includes a ring light generating unit comprising a conical lens group, wherein the conical lens group consists of lenses with different front and rear cone angles.

[0012] The spatial optical coupling device of the present invention comprises a conical mirror group, which is either a single conical mirror or a double conical mirror group consisting of a convex conical mirror and a concave conical mirror.

[0013] The spatial optical coupling device of the present invention, wherein the first parallel light generating unit comprises: A diverging light source, used to output a diverging beam of light to be combined; A collimating element, which is coaxially arranged along the principal optical axis, is used to collimate the diverging beam to generate the second parallel beam.

[0014] The spatial optical coupling device of the present invention comprises a diverging beam that is any one of terahertz light, infrared light, or visible light.

[0015] The spatial optical coupling device of the present invention comprises a collimating element being an off-axis reflector group, wherein the reflected optical axis of the off-axis reflector group is coaxial with the principal optical axis, and is used to reflect the diverging beam to generate a collimated second parallel beam.

[0016] In the spatial optical coupling device of the present invention, the first parallel beam is generated by a second parallel beam generating unit, and the structure of the second parallel beam generating unit is the same as that of the first parallel beam generating unit.

[0017] On the other hand, a spatial optical coupling method is also provided, applied to the spatial optical coupling device as described above, comprising: A first parallel beam with a first frequency band is refracted to produce a parallel ring beam. A second parallel beam with a second frequency band is generated in the hollow region of the parallel annular beam. The second parallel beam is coaxial with the parallel annular beam along the principal optical axis. The second parallel beam and the parallel annular beam constitute a parallel solid beam with the first frequency band and the second frequency band.

[0018] The advantages or beneficial effects of the technical solution of this invention are as follows: This invention uses a ring light generating unit to refract a first parallel beam with a first frequency band to generate a parallel ring beam. The first parallel light generating unit generates a second parallel beam with a second frequency band in the hollow region of the parallel ring beam. The second parallel beam and the parallel ring beam form a parallel solid beam with the first and second frequency bands, realizing unobstructed, low-loss, high-precision, and scalable coaxial beam combining of multiple spatial beams. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a spatial optical coupling device in a preferred embodiment of the present invention; Figure 2 A schematic diagram of a dual-beam spatial optical coupling device in a preferred embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a dual-beam spatial optical coupling device in a preferred embodiment of the present invention; Figure 4 A schematic diagram of a multi-beam spatial optical coupling device in a preferred embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of a multi-beam spatial optical coupling device in a preferred embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of a three-beam spatial optical coupling device in a preferred embodiment of the present invention. Detailed Implementation

[0020] The purpose of this invention is to provide a spatial optical coupling device and method to solve the inherent defects of existing beam splitter-level beam combining technology. It addresses the problems of severe beam obstruction, high cumulative energy loss, limited expansion of the number of combined beams, difficulty in coaxiality control, and poor adaptability to special bands such as terahertz.

[0021] Specifically, the core objectives of this invention are: First, to abandon the semi-transparent and semi-reflective cascade architecture, fundamentally eliminating beam obstruction problems, reducing energy loss during beam combining, and meeting the requirements for high energy utilization; Second, to break through the limitation on the number of beams combined, constructing a flexibly expandable beam combining structure to achieve coaxial beam combining of multiple beams (theoretically unlimited); Third, to establish a unified optical axis reference, simplify the calibration process, improve the coaxiality and environmental stability of the combined beam, and reduce the impact of accumulated errors; Fourth, to adapt to the coupling requirements of special wavelength beams such as terahertz waves, broadening the applicable wavelength range of the technology.

[0022] Ultimately, through architectural innovation, we have achieved unobstructed, low-loss, high-precision, and scalable coaxial beam combining of multiple spatial beams, providing reliable technical support for terahertz spectroscopy detection, laser processing, and other scenarios, and filling the application gaps of existing technologies.

[0023] 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. 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] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0026] In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a spatial optical coupling device and method are provided, which are suitable for unobstructed beam combining of multiple beams of special wavelengths such as terahertz waves, and are primarily applied in scenarios such as spectral detection and laser processing.

[0027] like Figure 1 As shown, the device includes: The ring light generating unit 10 is used to refract the first parallel beam L1 with the first frequency band to generate a parallel ring beam L2. The first parallel light generating unit 20 is coaxially arranged with the ring light generating unit 10 along the main optical axis, and the first parallel light generating unit 20 is located in the hollow region of the parallel ring beam L2. It is used to generate a second parallel beam L3 with a second frequency band. The second parallel beam L3 and the parallel ring beam L2 constitute a parallel solid beam with a first frequency band and a second frequency band.

[0028] Specifically, existing beam-splitting mirror-level beam combining technology, based on its core architecture of semi-transparent and semi-reflective cascade, cannot simultaneously meet the requirements of multi-beam combining, low loss, high precision, and wide-band compatibility. This invention addresses these issues by using a ring light generation unit 10 to receive incident parallel light and refract and shape it, converting the incident parallel light into a parallel ring beam with a ring-shaped cross-section. This parallel ring beam has preset inner diameter, outer diameter, and ring width parameters. Furthermore, the first parallel light generation unit 20 enables new parallel light to be combined to enter through the hollow region of the parallel ring beam, thereby achieving coaxial coupling and beam combining of spatial light. This invention abandons the semi-transparent and semi-reflective cascade architecture, fundamentally eliminating beam obstruction problems, reducing energy loss during beam combining, and meeting the requirements of high energy utilization. It innovates at the architectural level to completely solve the aforementioned pain points.

[0029] The spatial optical coupling device of the present invention, such as Figure 2 As shown, the first parallel beam L1 is generated by the second parallel beam generating unit 30, and the structure of the second parallel beam generating unit 30 is the same as that of the first parallel beam generating unit 20.

[0030] Furthermore, the spatial optical coupling device of the present invention includes N parallel light generating units, serving as N divergent spatial light sources, where N is a positive integer greater than 1. Each parallel light generating unit is used to collimate the divergent beams to be combined into parallel beams. Using the spatial optical coupling architecture of the present invention, the combining of N divergent beams can be achieved.

[0031] Specifically, the N parallel light generation units include one second parallel light generation unit 30 and N-1 first parallel light generation units 20. Each parallel light generation unit consists of a diverging light source and a collimating element. The diverging light source can be, but is not limited to, a terahertz quantum cascade laser (QCL), an infrared laser, or a visible light source, used to output the diverging beam to be combined. This diverging beam can be terahertz light, infrared light, or visible light. The diverging light sources of the N parallel light generation units form N diverging spatial light sources. The divergence angle of each source can be independently adjusted to adapt to the coupling requirements of beams in different wavelength bands, solving the problem of poor adaptability to special wavelength bands in existing technologies. The collimating elements are coaxially arranged along the principal optical axis, and their number matches the number of beams to be combined. Each collimating element is aligned with its corresponding diverging light source, ensuring that the diverging beam output from the laser can be incident on the collimating element and converted into a parallel beam.

[0032] The spatial optical coupling device of the present invention uses an off-axis reflector group as the collimating element. The reflected optical axis of the off-axis reflector group is coaxial with the principal optical axis and is used to reflect the diverging beam to generate a collimated second parallel beam.

[0033] In this embodiment, the off-axis reflector group uses off-axis parabolic reflectors instead of traditional beam splitters. In the N-beam spatial light coupling architecture, N diverging spatial light sources correspond to N off-axis parabolic reflectors. The off-axis angle and installation height of each off-axis parabolic reflector are set as needed, and all of them remain coaxial with the subsequent parallel annular beam. The off-axis parabolic reflectors will not extend into the propagation path of the parallel annular beam, eliminating the risk of obstruction.

[0034] The N off-axis parabolic mirrors include a first off-axis parabolic mirror 2a and second to Nth off-axis parabolic mirrors. The first off-axis parabolic mirror 2a is aligned with the first diverging spatial light source to collimate the diverging beam into a parallel beam, providing a basis for the ring conversion. The second to Nth off-axis parabolic mirrors are respectively aligned with the corresponding diverging spatial light source and installed outside the hollow region of the preceding parallel ring beam. Their reflected optical axes are collinear with the central axis of the preceding parallel ring beam to collimate the corresponding diverging light into parallel light and allow the parallel light to pass through the hollow region of the parallel ring beam, fundamentally eliminating beam obstruction and reducing energy loss.

[0035] Of course, this is not the only option; in other embodiments, other collimating elements can be used to achieve collimation of the diverging beam. For example, a convex lens can be used as the collimating element, with both the convex lens and the laser coaxial with the principal optical axis.

[0036] Furthermore, such as Figure 2 As shown, the second parallel light generating unit 30 is composed of a first diverging light source 301 and a first collimating element 302; wherein, the first diverging light source 301 serves as a first diverging spatial light source and is used to generate a first diverging beam L01 to be combined; the first collimating element 302 is coaxially arranged along the principal optical axis and is used to collimate the first diverging beam L01 to generate a first parallel beam L1.

[0037] The spatial optical coupling device of the present invention, such as Figure 2 As shown, the first parallel light generating unit 20 includes: The second diverging light source 201 is used to output the second diverging beam L02 to be combined; The second collimating element 202 is coaxially arranged along the principal optical axis and is used to collimate the second diverging beam L02 to generate the second parallel beam L3.

[0038] The spatial optical coupling device of the present invention emits a diverging beam of any one of terahertz light, infrared light, or visible light.

[0039] Specifically, a single laser can generate terahertz light, infrared light, or visible light. By combining beams of different frequencies generated by multiple lasers, the coupling requirements of special wavelength beams such as terahertz waves can be met, thus broadening the applicable wavelength range of the technology.

[0040] The spatial light coupling device of the present invention includes a ring light generating unit 10 comprising a conical lens group, wherein the conical lens group consists of lenses with different front and rear cone angles.

[0041] Specifically, the conical mirror group is sequentially positioned at the output end of the off-axis mirror group along the optical path of the principal optical axis. It receives the incident parallel light and refracts and shapes it, converting the incident parallel light into a parallel annular beam with a ring-shaped cross-section. This parallel annular beam has preset parameters for its inner diameter, outer diameter, and width. The inner diameter is the inner diameter of the hollow region of the parallel annular beam, the outer diameter is the outer diameter of the outer edge of the parallel annular beam, and the width is the difference between the outer diameter and the inner diameter. Furthermore, the inner diameter satisfies the requirements for the entry and transmission of the subsequent parallel light to be combined.

[0042] The inner and outer diameters of the parallel annular beam can be adjusted using the cone angles of the front and rear conical surfaces of the conical mirror assembly. The front cone angle controls the initial refraction direction of the incident parallel light, while the rear cone angle calibrates the parallelism of the refracted beam and defines the radial range of the annular beam. By synergistically optimizing the angle values ​​of the front and rear cone angles, the inner and outer diameters of the parallel annular beam can be flexibly adjusted, thereby forming an unobstructed transmission channel that meets the preset penetration requirements in the hollow region of the parallel annular beam.

[0043] This unobstructed transmission channel provides an independent space for the subsequent parallel beams to be combined to enter and transmit, effectively avoiding mutual occlusion between the beams to be combined and the already shaped parallel annular beams, and supporting the lateral expansion of the number of combined beams. Compared with the traditional beam combining structure, which is limited by the number of beams occupied by the beam space, this application, through the adjustable cone angle design of the conical mirror group, can dynamically match the size of the hollow region of the parallel annular beam according to the number of beams to be combined, and construct a modular beam combining structure that can be flexibly expanded, breaking through the limitation of the number of combined beams. Theoretically, it can achieve coaxial coupling beam combining with an unlimited number of beams, improving the scalability and adaptability of the beam combining.

[0044] like Figure 3 As shown, the dual-beam spatial optical coupling architecture includes a first laser 1a, a first off-axis parabolic mirror 2a, a first conical mirror 3a, a second laser 1b, and a second off-axis parabolic mirror 2b. The first off-axis parabolic mirror 2a, the first conical mirror 3a, and the second off-axis parabolic mirror 2b are arranged collinearly along the propagation direction of the principal optical axis. The first laser 1a is aligned with the first off-axis parabolic mirror 2a, and the second laser 1b is aligned with the second off-axis parabolic mirror 2b.

[0045] The spatial optical coupling device of the present invention uses a conical mirror group that is either a single conical mirror or a double conical mirror group consisting of a convex conical mirror and a concave conical mirror.

[0046] Specifically, in this embodiment, a single conical mirror can be used, or a combination of two conical mirrors consisting of a convex conical mirror and a concave conical mirror can be used to replace the single conical mirror, so as to more accurately adjust the ratio of the inner diameter to the outer diameter of the ring beam, adapt to beams of different spot sizes, and is especially suitable for the ring conversion of long wavelength beams such as terahertz, without affecting the beam combining accuracy.

[0047] In the spatial light coupling device of the present invention, the ring light generating unit 10 and the first parallel light generating unit 20 constitute a first-order beam combiner group 100. The beam combiner group 100 includes multiple orders, and the structures of the multiple-order beam combiner groups 100 are the same.

[0048] Specifically, in this embodiment, in the N-beam spatial light coupling architecture, such as Figure 4 As shown, the beam combiner group 100 includes N-1 beam combiners, namely the first beam combiner group 1001, the second beam combiner group 1002, ..., the N-1th beam combiner group. All beam combiner groups 100 have the same structure and can refract and shape the received incident parallel light into a parallel ring beam with a ring-shaped cross-section. The parallel ring beam has preset inner diameter, outer diameter and ring width parameters, and new parallel light to be combined is inserted into the hollow region of the parallel ring beam to realize the coupling and beam combining of multiple spatial light beams.

[0049] The spatial optical coupling device of the present invention further includes, between adjacent two-order beam combiner groups 100: The beam shrinking mirror 40 is positioned between the output end of the first parallel light generating unit of the previous beam combiner group and the input end of the ring light generating unit of the next beam combiner group. It is used to refract the parallel solid beam generated by the previous beam combiner group to generate a beam combined with a reduced beam. The ring light generating unit in the next-order beam combiner is used to refract the combined beam to generate a corresponding parallel ring beam.

[0050] Specifically, to optimize beam compatibility during multi-order beam combining, this embodiment sets a beam shrinking mirror 40 between two adjacent beam combining mirror groups 100. The beam shrinking mirror 40 is coaxially arranged with the two beam combining mirror groups 100 before and after it. It is used to receive the combined beam output by the previous beam combining mirror group 100 and to perform beam shrinking processing on the combined beam so that the beam size and divergence angle of the beam after shrinking are matched with the incident parameters of the next beam combining mirror group 100. The beam after shrinking is sent to the ring light generation unit of the next beam combining mirror group. The ring light generation unit refracts the beam to generate a corresponding parallel ring beam. Then, a new parallel light to be combined is inserted into the hollow region of the ring beam to complete the coupling and beam combining of this order. Through multi-order iteration, more beams of spatial light are coaxially combined.

[0051] Each beam shrinking lens 40 is composed of two or more achromatic convex lenses and concave lenses. It is used to reduce the size of the beam after beam combining, optimize the ratio of the inner diameter to the outer diameter of the annular beam, adapt to the light transmission aperture of the subsequent off-axis parabolic reflector, and improve the beam energy density. This solves the problems of fixed beam size and insufficient energy density in the existing technology. In addition, the lens material can be selected from terahertz band or other special band-compatible materials as needed to broaden the scope of application.

[0052] The number of conical mirror groups is one less than the number of light sources. In the N-beam spatial light coupling architecture, the conical mirror group includes a first conical mirror 3a and second to N-1 conical mirror groups; wherein, the first conical mirror 3a is located on the light output path of the first off-axis parabolic reflector 2a, and is used to receive the first parallel light and convert it into a parallel annular beam through refraction; the second to N-1 conical mirror groups are respectively set on the light output path of the spot beam-shrinking mirror group, receive the beam-shrinking combined light, convert it into a higher-order parallel annular beam, reserve space for the entry of the next light, and realize multi-level extended beam combining.

[0053] The number of beam-constricting mirrors 40 is one less than the number of conical mirror groups. The N-beam spatial light coupling architecture is as follows: Figure 5 As shown, it includes a first beam reducer 4a, a second beam reducer 4b, ..., a (N-2)th beam reducer group, wherein the first beam reducer 4a is located between the first beam combiner group 1001 and the second beam combiner group 1002, the second beam reducer 4b is located between the second beam combiner group 1002 and the third beam combiner group, and so on, and the (N-2)th beam reducer group is located between the (N-2)th beam combiner group and the (N-1)th beam combiner group.

[0054] In the spatial optical coupling device of the present invention, the second parallel beam generated by the first parallel beam generating unit in the multi-order beam combining mirror group 100 has a different frequency band.

[0055] Furthermore, the frequency band of the parallel light to be combined generated by each parallel light generating unit 20 can be flexibly configured as needed. It can select the same frequency band or different frequency bands, with the specific frequency band combination determined by the application scenario and performance requirements of the target combined light. For example, when it is necessary to enhance the coverage of a specific frequency band, new parallel light to be combined with the same frequency band can be introduced into two or more beam combining mirror groups 100, enabling the target frequency band light coverage to be increased during multi-stage beam combining. If it is necessary to generate multi-band combined light, parallel light to be combined with different frequency bands can be introduced into each stage of the beam combining mirror group 100 to form a multi-band combined light output.

[0056] Furthermore, the device also includes a beam calibration unit, composed of multiple one-dimensional or two-dimensional high-precision adjustment frames, which are connected to the conical mirror group and the off-axis mirror group respectively, for fine-tuning the pitch angle, deflection angle, and position of the corresponding components. By establishing a unified optical axis reference, the coaxiality of each off-axis mirror group and the conical mirror group is calibrated, compensating for installation errors and environmental disturbances, ensuring precise overlap of the annular beam and the parallel beam, improving beam combining stability, and solving the problem of difficult coaxiality control in existing technologies.

[0057] Furthermore, the one-dimensional or two-dimensional high-precision adjustment frame in the beam calibration unit can be replaced with a three-dimensional electric adjustment frame to achieve automated fine-tuning, improve calibration efficiency, and adapt to large-scale multi-beam coupling scenarios, while the connection method with optical components and the calibration benchmark remain unchanged.

[0058] The device of this invention employs an off-axis mirror group, a conical mirror group, and a beam-shrinking mirror group in synergy. Each component is arranged sequentially according to the direction of light propagation. The central optical axes of all off-axis mirror groups, conical mirror groups, and beam-shrinking mirror groups are collinear with the overall principal optical axis of the device, with precise positional matching to ensure coaxiality. A first laser 1a, a first off-axis parabolic mirror 2a, and a first conical mirror 3a constitute the initial annular beam generation optical path. A second laser 1b and a second off-axis parabolic mirror 2b constitute a parallel light incident optical path, with their output ends aligned with the hollow region of the parallel annular beam output by the first conical mirror 3a. The combined beam passes through the beam-shrinking mirror group and the second conical mirror 3b to form a secondary annular beam generation optical path. Subsequent beams to be combined and their corresponding off-axis parabolic mirrors are sequentially connected to the hollow region of a higher-order annular beam, forming an expandable closed-loop optical path. By constructing a unified optical axis reference, and using an architecture of collimation, annular conversion, coaxial insertion, beam contraction, and multi-level expansion, the pain points of existing technologies are addressed at the architectural level.

[0059] For scenarios requiring a fixed number of beams, subsequent beam reduction and higher-order annular conversion can be omitted. The preset number of beams can be combined directly by using multiple sets of off-axis parabolic mirrors and single-stage conical mirrors, simplifying the operation process and achieving unobstructed and low-loss operation.

[0060] This invention provides a spatial optical coupling method, applied to the spatial optical coupling device as described above, comprising: A first parallel beam with a first frequency band is refracted to produce a parallel ring beam. A second parallel beam with a second frequency band is generated in the hollow region of the parallel annular beam. The second parallel beam and the parallel annular beam are coaxial along the principal optical axis. The second parallel beam and the parallel annular beam constitute a parallel solid beam with a first frequency band and a second frequency band.

[0061] Specifically, existing beam-splitting mirror-level beam combining technology, based on its core architecture of semi-transparent and semi-reflective cascade, cannot simultaneously meet the requirements of multi-beam combining, low loss, high precision, and wide-band compatibility. This invention addresses this by refraction and shaping the incident parallel light, converting it into a parallel annular beam with a pre-defined inner diameter, outer diameter, and width. New parallel light to be combined is then allowed to enter through the hollow region of the parallel annular beam, thereby achieving coaxial coupling and beam combining of spatial light. This invention abandons the semi-transparent and semi-reflective cascade architecture, fundamentally eliminating beam obstruction problems, reducing energy loss during beam combining, and meeting the requirements of high energy utilization. It innovates at the architectural level to completely solve the aforementioned pain points.

[0062] Based on the above apparatus, the coupling method of the present invention follows an iterative expansion and includes the following steps: Step 1, Initial ring beam generation: Start the first divergent light source, adjust the first off-axis parabolic reflector 2a to collimate the divergent light into parallel light, and ensure stable beam propagation; incident the parallel light onto the first conical mirror 3a, and fine-tune the cone angle and angle of the conical mirror by adjusting the beam calibration unit to output a parallel ring beam with preset inner and outer diameters, reserving space for subsequent beams to pass through and laying the foundation for unobstructed beam combining.

[0063] Step 2, Coaxial beam combining of dual beams: Activate the second divergent light source, adjust the off-axis angle and installation height of the second off-axis parabolic reflector 2b so that the reflected parallel light axis is collinear with the central axis of the aforementioned annular beam, and the parallel light passes through the hollow area of ​​the annular beam without obstruction; finely adjust the angle of the first conical mirror 3a through the beam calibration unit so that the annular area of ​​the annular beam precisely coincides with the edge of the second parallel light spot, completing the low-loss beam combining of dual beams and solving the obstruction and loss problems of traditional technology.

[0064] Step 3, beam combining and high-order ring beam generation: The combined beam is incident on the first spot beam reducing mirror 4a, and the beam reducing magnification is optimized by adjusting the mirror group spacing to reduce the size of the combined beam spot; the combined beam after beam reduction is incident on the second conical mirror 3b to generate a second-order parallel ring beam, the size of which is adapted to the light transmission requirements of the third light path, providing structural support for beam number expansion.

[0065] Step 4, iterative beam combining of multiple beams: Start the third and subsequent light sources. For each new light source, install an off-axis parabolic reflector. Repeat the adjustment method in Step 2 to make the parallel light coaxially enter the hollow region of the corresponding order ring beam. Fine-tune the angle of the corresponding conical mirror group through the beam calibration unit to achieve precise overlap of the light spots.

[0066] If more beams need to be combined, repeat steps 3 and 4 of beam shrinking, higher-order ring conversion, and coaxial insertion until the preset number of beams is combined, achieving theoretically unlimited beam expansion.

[0067] Step 5, beam combining calibration and optimization: The coaxiality, energy loss rate and beam uniformity of the final beam combining are detected by the beam quality analyzer. If the parameters do not meet the standards, the angle of the corresponding off-axis parabolic mirror or conical mirror is finely adjusted by the beam calibration unit to compensate for the displacement error caused by environmental vibration and temperature changes, so as to ensure the beam combining accuracy and stability.

[0068] Specific embodiments are provided below to further illustrate this technical solution. Example 1 This embodiment uses the coaxial beam combining of three terahertz quantum cascade laser (QCL) chip outputs as an example, and describes in detail the specific implementation process of the present invention in conjunction with the optical path layout. All components used are commercially available and mature products, and those skilled in the art can reproduce them based on the following content.

[0069] This embodiment employs the collaborative architecture described above, consisting of a divergent light source, an off-axis mirror group, a conical mirror group, and a beam-shrinking mirror group. It performs unobstructed coaxial beam combining of the output beams from three 2.3THz, 2.7THz, and 3.2THz terahertz quantum cascade laser chips. The combined beam is then used for terahertz multi-band spectral detection. The overall optical path is arranged horizontally, with all components having collinear optical axes to form a unified optical axis reference. The total optical path length is approximately 50mm, suitable for laboratory desktop installation and industrial system packaging after debugging.

[0070] like Figure 6 As shown, the three-beam spatial optical coupling device includes: The diverging light source comprises three independent terahertz quantum cascade laser chips. The specific technical parameters and models of each chip are as follows: the first terahertz quantum cascade laser chip, model THz-QCL-0.3, operates at 2.3THz, has an output power of 10mW, and a beam divergence angle of 15°; the second terahertz quantum cascade laser chip, model THz-QCL-0.6, operates at 2.7THz, has an output power of 8mW, and a beam divergence angle of 12°; and the third terahertz quantum cascade laser chip, model THz-QCL-1.0, operates at 3.2THz, has an output power of 5mW, and a beam divergence angle of 10°. Each terahertz quantum cascade laser chip is fixedly mounted on a dedicated heat sink, which provides a stable heat dissipation channel for the corresponding chip, ensuring long-term stable operation under preset power output conditions. The output end face of each chip faces its corresponding off-axis parabolic reflector, and the central axis of each chip is set at the same height as the incident center point of the corresponding off-axis parabolic reflector. The distance between the chip output end face and the incident center point of the corresponding off-axis parabolic reflector is set to 5mm to ensure that the diverging light emitted by each chip can completely cover the effective incident area of ​​the corresponding off-axis parabolic reflector, avoiding light energy loss caused by beam overflow.

[0071] Off-axis mirror assembly: This assembly comprises three off-axis parabolic mirrors, each with an 8mm aperture, a 5mm focal length, and a 90° off-axis angle. Their structural parameters are identical to ensure consistent optical performance and optical path compatibility. The first off-axis parabolic mirror 2a is located directly in front of the 2.3THz quantum cascade laser chip, with a 5mm gap between it and the chip's output surface. Its reflective surface faces the chip, collimating the 2.3THz divergent light into parallel light. This parallel light is then reflected by the first conical mirror 3a to form a parallel annular beam. The second off-axis parabolic mirror 2b is mounted behind the first conical mirror 3a, with a 5mm gap between it and the first conical mirror. Its reflective surface faces downward and is aligned with the 2.7THz quantum cascade laser chip. The 2.7THz divergent light emitted by this chip is reflected... After collimation, parallel light is formed. This parallel light propagates along the central axis of the main optical path and enters the hollow region of the parallel annular beam generated by the first conical mirror 3a, achieving coaxial coupling with the annular beam. The third off-axis parabolic reflector 2c is installed behind the first beam-shrinking mirror 4a, with a distance of 2mm between it and the first beam-shrinking mirror 4a. The reflective surface is set downward and aligned with the 3.2THz quantum cascade laser chip. The 3.2THz divergent light emitted by the chip is reflected and collimated to form parallel light. This parallel light enters the hollow region of the second-order parallel annular beam generated by the second conical mirror 3b.

[0072] All three off-axis parabolic mirrors are fixed by a dedicated bracket, which is connected to the beam calibration unit. Through the adjustment function of the beam calibration unit, the attitude calibration and position fine adjustment of each off-axis parabolic mirror can be realized to ensure that the optical center of each mirror is aligned with the axis of the corresponding optical path.

[0073] Conical Mirror Assembly: Composed of two conical mirrors, each with an aperture of 8mm, a front cone angle of 20°, and a rear cone angle of 40°. The first conical mirror 3a is coaxially positioned on the center line of the main optical path and directly in front of the first off-axis parabolic reflector 2a, with a distance of 5mm between them. The first conical mirror 3a receives the first 2.3THz parallel light collimated from the first off-axis parabolic reflector 2a and converts it into a parallel annular beam. The second conical mirror 3b is coaxially positioned on the center line of the main optical path and directly behind the first beam-shrinking mirror 4a, with a distance of 3mm between them. On the center line of the main optical path, the second conical mirror 3b receives the combined beam after beam shrinking and converts it into a second-order parallel annular beam.

[0074] The beam-shrinking lens assembly consists of two coaxial achromatic lenses. The convex lens has a focal length of 50mm and is made of high-density polyethylene; the concave lens has a focal length of 25mm and is made of polytetrafluoroethylene (PTFE), suitable for the terahertz band. The first beam-shrinking lens 4a is coaxially positioned between the dual-beam combining point and the second conical lens 3b along the main optical path, with a distance of 5mm between it and the dual-beam combining point. The beam-shrinking ratio is preset to 1:3. The first beam-shrinking lens 4a is used to reduce the size of the combined dual-beam beam spot and optimize the proportion of the annular beam.

[0075] All components are connected by a cylindrical structure to ensure that the light path is not obstructed. The structural components are fixed on the same optical platform with a flatness ≤0.02mm / m. The first quantum cascade laser chip, the first off-axis parabolic reflector 2a, and the first conical mirror 3a form the initial annular beam path. The second quantum cascade laser chip and the second off-axis parabolic reflector 2b reflect the beam and then enter the main optical path, coaxial with the annular beam. The combined beam is generated into a second-order annular beam by the first spot shrinking mirror 4a and the second conical mirror 3b. The third quantum cascade laser chip and the third off-axis parabolic reflector 2c reflect the beam and then enter the main optical path, coaxial with the second-order annular beam. Finally, the combined beam is output to the detection equipment.

[0076] This embodiment executes the steps in the following order: initial annular beam generation, dual-beam combining, beam contraction and secondary annular beam generation, and triple-beam combining. The steps cannot be arbitrarily interchanged. The specific details are as follows: The first step is the initial generation of the annular beam: turn on the 2.3THz quantum cascade laser chip and preheat it for 10 minutes to stabilize the output light; adjust the first off-axis parabolic reflector 2a to collimate the divergent light into parallel light with a parallelism of ≤0.05mrad; adjust the first conical mirror 3a to refract the parallel light to generate a 2.3THz parallel annular beam with an inner diameter of 10mm and an outer diameter of 20mm. Observe the beam spot morphology using a beam quality analyzer to ensure that the annular shape is uniform and distortion-free.

[0077] The second step is coaxial beam combining: turn on the 2.7THz quantum cascade laser chip and preheat for 5 minutes; adjust the second off-axis parabolic reflector 2b, fine-tuning its off-axis angle and installation height, so that the reflected 2.7THz parallel light axis is completely aligned with the central axis of the annular beam generated in the first step, with a coaxiality ≤0.08mrad, and the parallel light passes through the hollow area of ​​the annular beam without obstruction; fine-tune the angle of the first conical mirror 3a using the two-dimensional adjustment frame, so that the annular area of ​​the annular beam is precisely aligned with the edge of the 2.7THz parallel light spot, with an overlap ≥98%, completing the beam combining. At this point, the measured total energy loss is 3.2%.

[0078] The third step is to generate the combined beam and the secondary ring beam: the combined beam is incident on the first spot beam shrinking mirror 4a, and the beam shrinking ratio is confirmed to be 1:3 by fine-tuning the lens spacing. The diameter of the combined beam spot after beam shrinking is 5mm. The combined beam after beam shrinking is incident on the second conical mirror 3b to generate a secondary parallel ring beam with an inner diameter of 10mm and an outer diameter of 20mm, ensuring that the size of the hollow area is adapted to the 3.2THz parallel light and the spot diameter is 8mm.

[0079] Step 4: Coaxial beam combining of the three beams: Turn on the 3.2THz quantum cascade laser chip and preheat for 5 minutes; adjust the installation position and angle of the third off-axis parabolic reflector 2c so that the reflected 3.2THz parallel light axis is collinear with the central axis of the second-order annular beam, and the parallel light passes through the hollow region; fine-tune the second conical mirror 3b so that the edge of the second-order annular beam coincides with the edge of the 3.2THz parallel light spot, completing the coaxial beam combining of the three beams. At this time, the combined beam contains three frequency bands: 2.3THz, 2.7THz, and 3.2THz, without obstruction or intersection.

[0080] Step 5, beam combining calibration and optimization: Turn on the beam quality analyzer to detect the final beam combining parameters. If the coaxiality is >0.1mrad, the energy loss is >5%, or the beam distortion rate is >2%, fine-tune the corresponding components: if the coaxiality does not meet the standard, fine-tune the horizontal position of the third off-axis parabolic mirror 2c; if the energy loss exceeds the standard, check the conical mirror; if the beam distortion is abnormal, calibrate the spacing of the beam shrinking mirror group; until the parameters meet the standards, coaxiality ≤0.1mrad, total energy loss ≤4.5%, and beam distortion rate ≤2%, lock all adjustment frame positions to complete beam combining.

[0081] The sequence of steps in this embodiment is unique: the first step is the foundation; without the initial annular beam, subsequent unobstructed penetration cannot be achieved; the second step requires the annular beam from the first step to complete the dual-beam combining; the third step requires the combined dual-beam beam to be reduced in order to generate a secondary annular beam adapted to the third beam; the fourth step relies on the secondary annular beam from the third step to achieve the three-beam combining; the fifth step is the final calibration, which must be performed after all beams have been combined, as premature calibration will fail due to subsequent component adjustments.

[0082] After the assembly and debugging of the aforementioned optical path structure, the terahertz light emitted from the three terahertz quantum cascade laser chips at different frequency bands is coaxially coupled and combined without obstruction. The beam combining performance of this structure was verified by experimental testing, and the key performance parameters obtained are as follows: the total energy loss is 4.2%, compared to the ≥30% energy loss of traditional beam splitter technology with the same number of beams combined, the beam combining structure of this invention reduces energy loss by 86%, significantly improving the energy utilization rate of terahertz light; the coaxiality of the multi-frequency terahertz light after beam combining reaches 0.09 mrad, and under conditions of environmental vibration amplitude ≤0.05 mm and ambient temperature variation ±5℃, the coaxiality drift of the combined light is only 0.015 mrad, demonstrating excellent stability; it can be directly interfaced with a terahertz spectral detection system to achieve synchronous spectral detection of multi-frequency terahertz light, improving detection efficiency by more than 2 times compared to the traditional single-frequency sequential detection method.

[0083] Example 2 If it is necessary to increase the number of beams, such as 4 or more, taking 4 beams as an example, based on Example 1, one quantum cascade laser chip, one off-axis parabolic mirror, and one conical mirror can be added. The third and fourth steps are repeated, and the three combined beams are further reduced by the beam-shrinking mirror group. The beam is then generated into a three-order annular beam by the newly added conical mirror, and after reflection by the newly added off-axis parabolic mirror, it is connected to the main optical path.

[0084] This invention precisely addresses the core technical pain points of existing beam splitter-level beam combining technologies by using a collaborative architecture design of off-axis mirror group, conical mirror group, and beam shrinking mirror group, combined with a multi-order iterative beam combining method. These pain points include severe beam obstruction, high cumulative energy loss, limited expansion of the number of combined beams, difficulty in coaxiality control, and poor adaptability to special bands such as terahertz.

[0085] The advantages or beneficial effects of adopting the above technical solution are as follows: First, it completely eliminates beam obstruction, significantly reducing energy loss. This invention relies on the unobstructed installation design of an off-axis parabolic mirror and the principle of beam combining through a hollow region of a ring beam. It abandons the traditional beam-splitter's semi-transparent, semi-reflective mode, ensuring no cross-blocking or ineffective energy loss during the coupling and combining of multiple beams. The energy loss of a single beam is ≤2%, compared to the 15%~50% total energy loss of traditional beam-splitter combining technology under the same conditions. This invention reduces energy loss by over 70%. For the terahertz band, the beam combining efficiency of this invention is ≥85%, far exceeding the ≤40% beam combining efficiency of traditional beam-splitter technology in the terahertz band, fully meeting the high energy utilization requirements of various optical systems.

[0086] Secondly, this invention overcomes the limitation on the number of beams, enabling flexible expansion and beam combining. Through a multi-order iterative beam combining process involving beam shrinking and high-order ring transformation, the theoretically unlimited number of beams can be combined. Laboratory tests have verified its stable coaxial beam combining of 10 mid-infrared quantum cascade laser chips. Furthermore, this invention employs a modular optical path design; adding a new beam only requires the addition of a corresponding off-axis parabolic mirror and its beam calibration unit, without requiring reconstruction of the overall optical path. This results in low expansion costs, convenient operation, and suitability for beam combining requirements in multi-source composite systems.

[0087] Third, it improves coaxiality and stability and simplifies the calibration process. By establishing a unified optical axis reference with the help of the beam calibration unit, the coaxiality of the multiple beams after beam combining is ≤0.1mrad. Under the conditions of environmental vibration amplitude ≤0.05mm and ambient temperature variation of ±5℃, the coaxiality drift is ≤0.02mrad, and the stability is significantly enhanced. Moreover, the calibration time for a single beam is shortened to within 5 minutes. Compared with the cumulative calibration method of traditional beam splitter-level beam combining technology, the calibration efficiency is improved, and the cumulative calibration error caused by multi-stage beam combining in traditional technology is effectively avoided.

[0088] Fourth, it broadens the band adaptation range and has strong compatibility. The beam-shrinking lens assembly of this invention can be made of terahertz-compatible materials such as polytetrafluoroethylene and high-density polyethylene, and can couple and combine multiple band beams such as 0.1-10THz terahertz waves, 400-1700nm visible light and infrared light; and can switch bands without replacing the core optical components. Compared with traditional beam splitters that are dedicated to a single band, the band adaptability of this invention is greatly improved.

[0089] Furthermore, the beam energy density after beam combining according to this invention is significantly improved. After beam combining with a beam-shrinking lens group, the beam shrinkage ratio is adjustable from 1:2 to 1:5. The energy density can reach 80% × N of the original single beam, where N is the number of beams combined. Compared with traditional beam combining technology, the beam combining light energy density of this invention is improved, which can meet the requirements of high-energy-density beams in laser processing and high-precision detection.

[0090] In terms of economic benefits, this invention has significant cost advantages and industrialization value: First, it reduces equipment manufacturing costs, as the core optical components are all commercially available mature products, eliminating the need for customized development; second, it reduces operation and maintenance costs, as the modular design eliminates the need for professional teams for component replacement and calibration; and third, it improves equipment reusability, as the multi-band adaptability avoids the need for repeated purchases of dedicated single-band equipment, saving equipment investment for research institutions and enterprises.

[0091] The device and method of this invention can be widely applied in various fields such as scientific research, industry, and optical communication. In the scientific research field, it can support cutting-edge research such as multi-band terahertz spectral detection and quantum optics experiments, helping to enhance scientific research competitiveness in the field of terahertz technology. In the industrial field, high-energy-density beam combining can improve laser processing efficiency and reduce energy consumption per unit product, which is in line with the industrial development concept of green manufacturing and energy conservation. In the field of optical communication, coaxial beam combining of multiple beams can broaden communication bandwidth and provide core optical technology support for next-generation communication technologies such as 5G / 6G. At the same time, the modular design and easy implementation of this invention can promote the industrialization and popularization of high-precision beam combining technology, and drive the upgrading and product iteration of upstream and downstream industries such as optical detection and laser equipment.

[0092] In summary, this invention transforms incident parallel light into a parallel annular beam with a ring-shaped cross-section through refraction and shaping. Then, new parallel light to be combined can enter through the hollow region of the parallel annular beam, achieving coaxial coupling and beam combining of spatial light. This results in breakthroughs in unobstructed beam combining, low energy loss, high-precision coaxiality, and scalable beam combining capacity, reducing the total lifecycle cost, empowering technological innovation in multiple fields, comprehensively filling existing technological gaps, and showing broad application prospects.

[0093] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present invention.

Claims

1. A spatial optical coupling device, characterized in that, include: A ring light generating unit is used to refract a first parallel beam with a first frequency band to generate a parallel ring beam. A first parallel light generating unit is arranged coaxially with the ring light generating unit along the main optical axis, and the first parallel light generating unit is located in the hollow region of the parallel ring beam. It is used to generate a second parallel beam with a second frequency band. The second parallel beam and the parallel ring beam constitute a parallel solid beam with the first frequency band and the second frequency band.

2. The spatial optical coupling device according to claim 1, characterized in that, The ring light generating unit and the first parallel light generating unit constitute a first-order beam combiner group. The beam combiner group includes multiple orders, and the structures of the multiple orders of beam combiner groups are the same. Adjacent beam combiner groups also include: The beam shrinking mirror group is located between the output end of the first parallel light generating unit of the previous beam combiner group and the input end of the ring light generating unit of the next beam combiner group. It is used to refract the parallel solid beam generated by the previous beam combiner group to generate a beam combined with a reduced beam. The ring light generating unit in the next-order beam combiner is used to refract the combined beam to generate a corresponding parallel ring beam.

3. The spatial optical coupling device according to claim 2, characterized in that, The second parallel beam generated by the first parallel light generating unit in the multi-stage beam combiner group has a different frequency band.

4. The spatial optical coupling device according to claim 1, characterized in that, The ring light generating unit includes a conical lens group, which consists of lenses with different front and rear cone angles.

5. The spatial optical coupling device according to claim 1, characterized in that, The conical mirror group can be any one of a single conical mirror or a double conical mirror group consisting of a convex conical mirror and a concave conical mirror.

6. The spatial optical coupling device according to claim 1, characterized in that, The first parallel light generating unit includes: A diverging light source, used to output a diverging beam of light to be combined; A collimating element, which is coaxially arranged along the principal optical axis, is used to collimate the diverging beam to generate the second parallel beam.

7. The spatial optical coupling device according to claim 6, characterized in that, The diverging beam can be any one of terahertz light, infrared light, or visible light.

8. The spatial optical coupling device according to claim 6, characterized in that, The collimating element is an off-axis mirror assembly, the reflected optical axis of which is coaxial with the principal optical axis, used to reflect the diverging beam to generate the collimated second parallel beam.

9. The spatial optical coupling device according to claim 1, characterized in that, The first parallel beam is generated by a second parallel beam generating unit, and the structure of the second parallel beam generating unit is the same as that of the first parallel beam generating unit.

10. A spatial optical coupling method, applied to the spatial optical coupling device as described in any one of claims 1-9, characterized in that, include: A first parallel beam with a first frequency band is refracted to produce a parallel ring beam. A second parallel beam with a second frequency band is generated in the hollow region of the parallel annular beam. The second parallel beam is coaxial with the parallel annular beam along the principal optical axis. The second parallel beam and the parallel annular beam constitute a parallel solid beam with the first frequency band and the second frequency band.

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