A polarization-maintaining beam combining device for multiple lasers of the same wavelength

Abstract

This invention discloses a polarization-maintaining beam combining device for multiple lasers of the same wavelength, relating to the field of laser technology. It arranges two or more intracavity frequency-doubled lasers with the same wavelength in series, ensuring that the generated frequency-doubled lasers propagate along the same straight line. A mirror at one end of the device ensures that all the frequency-doubled lasers propagate in the same direction, and at the other end, all the frequency-doubled lasers are reflected out of the laser resonant cavity optical path. This invention offers advantages such as high-power polarization-maintaining output, good beam quality, and a small spatial divergence angle.

Description

Technical Field

[0001] This utility model relates to the field of laser technology, and more specifically to a polarization-maintaining beam combining device for multiple lasers of the same wavelength. Background Technology

[0002] High-power linearly polarized laser sources are urgently needed equipment in high-end manufacturing and precision inspection fields. For example, in semiconductor defect detection, their important applications are reflected in several aspects: 1. Photoluminescence imaging: Linearly polarized lasers excite semiconductor materials to produce photoluminescence. By analyzing the polarization characteristics of the emitted light, impurities, stress, or crystal defects in the material can be detected. This technology has high sensitivity for defect location and property analysis. 2. Interferometry and surface roughness analysis: When linearly polarized lasers are used for interferometry, minute deformations or roughness of semiconductor surfaces can be accurately detected by changes in polarization state. For example, in the inspection of patternless wafers, polarization analysis of laser scattering can effectively distinguish surface particles from environmental noise. 3. Polarization scattering measurement in patterned wafer inspection: For wafers with circuit patterns, linearly polarized lasers combined with scattering measurement methods can identify submicron-level defects, such as scratches or pattern deviations. The difference in polarization signals helps to enhance the signal-to-noise ratio and improve detection accuracy. 4. Polarized Light Detection in Low-Dimensional Semiconductors: Novel low-dimensional semiconductor materials (such as two-dimensional materials) exhibit anisotropic responses to linearly polarized light, which can be used in highly integrated polarization-sensitive detectors, providing new ideas for defect detection. Furthermore, the wavelength stability and narrow linewidth characteristics of linearly polarized lasers further improve the reliability and resolution of detection. In the future, with the development of low-dimensional semiconductor technology, the application of polarized light detection in defect detection will become even more widespread.

[0003] To improve laser output power while ensuring monochromaticity, it is usually necessary to combine multiple laser beams of the same wavelength into a single beam transmitted coaxially. Currently, the "fiber optic beam combining" method is commonly used. However, there are differences in the specific implementation path, such as: (1) using a mirror to combine the beams emitted by different lasers into parallel directions with similar spatial positions, and then using a coupling lens to uniformly superimpose these beams into an optical fiber; (2) configuring a coupling lens for each laser beam, focusing all lasers onto a spatial point, placing an optical fiber at this common focal point, and coupling the output; (3) using a lens to couple the output beam of each laser into an optical fiber, and then bundling these optical fibers to form a honeycomb-shaped output. Regardless of the scheme, after coupling with ordinary optical fiber, the combined laser is no longer linearly polarized, and the linear polarization state of the original single laser beam cannot be preserved. In addition, the beam quality will also deteriorate significantly, and the M2 factor will change from single digits to tens or even hundreds. In recent years, a relatively expensive polarization-maintaining fiber has appeared on the market, which can provide linearly polarized coupled output. However, due to the small aperture of the polarization-maintaining fiber (typical value 5~15), Due to issues such as difficulty in alignment and susceptibility to damage, it can only couple low-level laser power (typically 10~100mW), which cannot meet the beam combining requirements of high-power lasers above the watt level.

[0004] Therefore, how to achieve high-power, high-beam-quality, and linearly polarized multi-beam same-wavelength laser combining is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a polarization-maintaining beam combining device for multiple lasers with the same wavelength, which can combine multiple lasers with the same wavelength, taking into account characteristics such as high power, high beam quality, and linear polarization.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A polarization-maintaining beam combining device for multiple lasers of the same wavelength includes at least two lasers of the same wavelength and three mirrors; The laser outputs left-propagating frequency-doubled light and right-propagating frequency-doubled light; the right-propagating frequency-doubled light from all lasers propagates in series along the same straight line to the first reflecting mirror, and the left-propagating frequency-doubled light propagates in series along the same straight line to the second reflecting mirror. The first mirror reflects the right-hand frequency-doubled light to the second mirror, the second mirror reflects all the frequency-doubled light to the third mirror, and the third mirror outputs polarization-maintaining combined light.

[0007] This invention arranges at least two intracavity frequency-doubled lasers with the same wavelength in series, so that the frequency-doubled lasers they generate can propagate in the same straight line. At one end of the entire device, a reflector is used to make all the frequency-doubled lasers propagate in the same direction. At the other end of the entire device, all the frequency-doubled lasers are reflected out of the laser resonant cavity optical path and reflected to the desired direction, thus realizing polarization-maintaining beam combining of multiple lasers with the same wavelength.

[0008] Preferably, the first reflector is a 0° total reflection mirror, and the second and third reflectors are 45° total reflection mirrors; the first and second reflectors are disposed on the same horizontal plane as the frequency-doubled light output by the laser; the first reflector is disposed perpendicular to the frequency-doubled light transmission optical path, and the second and third reflectors are at a 45° angle to the frequency-doubled light transmission optical path, and the second and third reflectors are perpendicular to each other.

[0009] Preferably, the lasers of the same wavelength include a pump source, a pump light focusing coupling system, and a resonant cavity arranged sequentially along the optical path transmission direction; the resonant cavities of all lasers output left-propagating frequency-doubled light and right-propagating frequency-doubled light. Each laser has identical optical elements and structure, the fundamental frequency light oscillating within the cavity has the same wavelength, and the generated frequency-doubled light has the same wavelength.

[0010] Preferably, the resonant cavity includes a crystal, a left-end output mirror, and a right-end output mirror, which are located on the same horizontal plane as the first reflector and the second reflector. The laser emitted by the pump source is transmitted to the crystal through the pump light focusing coupling system, generating left-propagating frequency-doubled light that is transmitted to the second reflector through the left-end output mirror, and generating right-propagating frequency-doubled light that is transmitted to the first reflector through the right-end output mirror.

[0011] Preferably, the resonant cavity in the laser includes one or more of the following: a four-mirror Z-type cavity, a three-mirror V-type cavity, and a two-mirror linear cavity. Under the principle of connecting the frequency-doubled light propagation optical paths of multiple lasers of the same wavelength in series, the resonant cavities of multiple lasers can be selected from four-mirror Z-type cavities, three-mirror V-type cavities, two-mirror linear cavities, or combinations of different cavity types, such as multiple four-mirror Z-type cavities and multiple two-mirror linear cavities.

[0012] Preferably, when a four-mirror Z-shaped cavity is selected as the resonant cavity, it includes a first end mirror, a laser crystal, a second end mirror, a third end mirror, a frequency doubling crystal, and a fourth end mirror arranged along the optical path transmission direction. The second and third end mirrors are inclined. The first end mirror receives the laser transmitted from the pump light focusing coupling system and transmits it to the laser crystal. The laser output from the laser crystal is refracted by the second end mirror to the third end mirror below. The third end mirror refracts the laser onto the frequency doubling crystal, which is horizontally positioned. The left-propagating frequency-doubled light output from the left end of the frequency doubling crystal is output through the third end mirror, and the right-propagating frequency-doubled light output from the right end is output through the fourth end mirror. The third end mirror serves as the left-end output mirror, and the fourth end mirror serves as the right-end output mirror. The first mirror, the third end mirror, the frequency doubling crystal, the fourth end mirror, and the second mirror are located on the same horizontal line. The left-propagating frequency-doubled light output from the left end of the frequency doubling crystal is transmitted to the second mirror through the third end mirror, and the right-propagating frequency-doubled light output from the right end is output through the fourth end mirror and then reflected by the first mirror to the second mirror.

[0013] Preferably, the pump source emits a 444nm laser; the first end mirror is a plane mirror, with a 444nm anti-reflection coating deposited on the side near the pump light focusing coupling system and a 444nm anti-reflection and 522nm high-reflection dielectric coating deposited on the side near the laser crystal; both ends of the laser crystal are coated with 444nm and 522nm anti-reflection dielectric coatings; the second end mirror is a plano-concave mirror, with a 522nm high-reflection and 640nm anti-reflection dielectric coating deposited on the concave side near the laser crystal; the third end mirror is a plane mirror, with a 522nm high-reflection and 261nm anti-reflection dielectric coating deposited on the side near the frequency doubling crystal and a 261nm anti-reflection coating deposited on the side away from the frequency doubling crystal; both ends of the frequency doubling crystal are coated with 522nm and 261nm anti-reflection dielectric coatings; the fourth end mirror is a plane mirror, with a 522nm high-reflection and 261nm anti-reflection dielectric coating deposited on the side near the frequency doubling crystal and a 261nm anti-reflection coating deposited on the side away from the frequency doubling crystal.

[0014] Preferably, when a three-mirror V-shaped cavity is selected as the resonant cavity, it includes a first end mirror, a laser crystal, a second end mirror, a frequency doubling crystal, and a third end mirror arranged along the optical path transmission direction; the pump source, the pump light focusing coupling system, the first end mirror, the laser crystal, and the second end mirror are all tilted; the first end mirror receives the laser light transmitted by the pump light focusing coupling system and transmits it to the laser crystal, and the laser light output by the laser crystal is refracted by the second end mirror to the frequency doubling crystal; the left-propagating frequency-doubled light output from the left end of the frequency doubling crystal is output through the third end mirror, and the right-propagating frequency-doubled light output from the right end is output through the second end mirror. The first mirror, the second end mirror, the frequency doubling crystal, the third end mirror, and the second mirror are located on the same horizontal line. The left-propagating frequency-doubled light output from the left end of the frequency doubling crystal is transmitted to the second mirror through the third end mirror, and the right-propagating frequency-doubled light output from the right end is output through the second end mirror and then reflected by the first mirror to the second mirror.

[0015] Preferably, the pump source emits a 444nm laser; the first end mirror is a plane mirror, with a 444nm anti-reflection coating deposited on the side near the pump light focusing coupling system and a 444nm anti-reflection and 522nm high-reflection dielectric coating deposited on the side near the laser crystal; both ends of the laser crystal are coated with 444nm and 522nm anti-reflection dielectric coatings; the second end mirror is a plano-concave mirror, with a 522nm high-reflection and 640nm anti-reflection dielectric coating deposited on the concave surface near the laser crystal and a 261nm anti-reflection coating deposited on the planar surface away from the laser crystal; both ends of the frequency doubling crystal are coated with 522nm and 261nm anti-reflection dielectric coatings; the third end mirror is a plane mirror, with a 522nm high-reflection and 261nm anti-reflection dielectric coating deposited on the side near the frequency doubling crystal and a 261nm anti-reflection coating deposited on the side away from the frequency doubling crystal.

[0016] Preferably, when a two-mirror single-cavity resonator is selected, the laser includes two sets of pump sources and two sets of pump beam focusing coupling systems. The resonator includes a first pump beam reflector, a self-frequency doubling laser crystal, and a second pump beam reflector. The laser output from one set of pump sources and pump beam focusing coupling systems is transmitted to the self-frequency doubling laser crystal via the first pump beam reflector, and the laser output from the other set of pump sources and pump beam focusing coupling systems is transmitted to the self-frequency doubling laser crystal via the second pump beam reflector. The left-propagating frequency-doubled light output from the left end of the self-frequency doubling laser crystal is output via the first pump beam reflector, and the right-propagating frequency-doubled light output from the right end is output via the second pump beam reflector. The first pump beam reflector serves as the left-end output mirror, and the second pump beam reflector serves as the right-end output mirror.

[0017] Preferably, the pump source emits a 444nm laser; the first pump light reflector and the second pump light reflector are both plane mirrors, with a 530nm anti-reflection film deposited on the side away from the self-frequency doubling laser crystal and an 810nm high-reflectivity and 530nm anti-reflection dielectric film deposited on the side closer to the self-frequency doubling laser crystal; and 530nm anti-reflection, 810nm anti-reflection, and 1060nm high-reflectivity dielectric films deposited at both ends of the self-frequency doubling laser crystal.

[0018] Preferably, a first reflecting mirror is placed vertically near the right-end output mirror of the rightmost laser. The first reflecting mirror is a plane mirror, and the side closest to the laser is coated with a highly reflective dielectric film for frequency-doubled light incident at a 0° angle. For lasers with four mirrors (Z-type cavity) or three mirrors (V-type cavity), the second reflecting mirror is coated with a 522nm high-transmittance, 261nm high-reflection dielectric film. For lasers with two mirrors (straight cavity), the second reflecting mirror is coated with a 1060nm high-transmittance, 530nm high-reflection dielectric film.

[0019] Preferably, a second reflecting mirror is tilted on the side of the left-hand output mirror of the leftmost laser, away from the laser. The second reflecting mirror is a plane mirror. The frequency-doubled light reflected by the first reflecting mirror is refracted by the second reflecting mirror to the third reflecting mirror, and then the frequency-doubled light is extracted by the third reflecting mirror. The side of the second reflecting mirror closest to the laser is coated with a highly reflective dielectric film. The second reflecting mirror can be tilted at 45° relative to the horizontal plane. The frequency-doubled light reflected by the first reflecting mirror is incident at a 45° angle with the second reflecting mirror, and then refracted by the second reflecting mirror into perpendicular light that is transmitted to the third reflecting mirror. For lasers with four mirrors (Z-type cavity) or three mirrors (V-type cavity), the second reflecting mirror is coated with a 522nm high-transmittance, 261nm high-reflection dielectric film. For lasers with two mirrors (straight cavity), the second reflecting mirror is coated with a 1060nm high-transmittance, 530nm high-reflection dielectric film.

[0020] Preferably, the third reflecting mirror is located vertically below the second reflecting mirror, receiving and exporting the frequency-doubled light reflected by the second reflecting mirror; the third reflecting mirror is a plane mirror, and a highly reflective dielectric film is coated on the side closest to the second reflecting mirror. For lasers with four mirrors (Z-type cavity) or three mirrors (V-type cavity), the second reflecting mirror is coated with a 522nm high-transmittance, 261nm high-reflection dielectric film; for lasers with two mirrors (straight cavity), the second reflecting mirror is coated with a 1060nm high-transmittance, 530nm high-reflection dielectric film.

[0021] Preferably, an active or passive optical modulation device is added to the resonant cavity of the laser, thereby switching from continuous operation to pulsed operation modes such as Q-switching and mode-locking to meet different application requirements. The optical modulation device can be placed in the non-frequency-doubled light transmission path to avoid loss to the frequency-doubled light, or in the transmission path with a smaller cavity mode.

[0022] As can be seen from the above technical solution, compared with the prior art, this utility model discloses a polarization-maintaining beam combining device and method for multiple lasers of the same wavelength, overcoming the shortcomings of the prior art. For beam combining multiple lasers of the same wavelength, it combines the characteristics of linear polarization, high power, and high beam quality. While increasing power, it has significant advantages such as polarization-maintaining output, good beam quality, and small spatial divergence angle, which can meet the urgent needs of precision measurement, high-definition imaging, biomedicine, and other fields for high monochromaticity, high power, high beam quality, and high coherence laser sources. This utility model differs from laser amplification technology, which is characterized by the entire device containing only one laser resonator to generate seed light, and is not essentially a beam combining of multiple lasers. Furthermore, laser amplification devices output the fundamental frequency wavelength and need to operate in pulsed mode. This utility model involves the coupling between three or more laser resonators and their outputs, addressing the beam combining problem of multiple solid-state lasers, outputting frequency-doubled light wavelengths, and operating in either continuous or pulsed mode. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 A schematic diagram of the polarization-maintaining beam combining device for multiple lasers of the same wavelength in the first embodiment provided by this utility model; Figure 2 A schematic diagram of the polarization-maintaining beam combining device for multiple lasers of the same wavelength in the second embodiment provided by this utility model; Figure 3 A schematic diagram of the polarization-maintaining beam combining device for multiple lasers of the same wavelength in the third embodiment provided by this utility model. Detailed Implementation

[0025] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0026] This utility model discloses a polarization-maintaining beam combining device for multiple lasers of the same wavelength, including at least two lasers of the same wavelength and three mirrors; the lasers output left-propagating frequency-doubled light and right-propagating frequency-doubled light; the right-propagating frequency-doubled light of all lasers propagates in series along the same straight line to the first mirror, and the left-propagating frequency-doubled light propagates in series along the same straight line to the second mirror; the first mirror reflects the right-propagating frequency-doubled light to the second mirror, the second mirror reflects all the frequency-doubled light to the third mirror, and the third mirror outputs the polarization-maintaining beam combining light.

[0027] Furthermore, the first reflector is a 0° total reflection mirror, while the second and third reflectors are tilted total reflection mirrors with an angle that can be set to 45°. The first and second reflectors are positioned on the same horizontal plane as the frequency-doubled light output from the laser. The first reflector is positioned perpendicular to the frequency-doubled light transmission path, while the second and third reflectors are at a certain angle to the frequency-doubled light transmission path. When the tilt angle of the second and third reflectors is 45°, they form a 45° angle with the frequency-doubled light transmission path, and the second and third reflectors are perpendicular to each other. Each solid-state laser adopts a dual-end output design for the frequency-doubled light. By connecting the frequency-doubled light paths of all lasers in series, all the frequency-doubled light propagates along the same straight line. Then, the combination of total reflection mirrors is used to guide all the frequency-doubled light out of the entire device in the same direction. This technology achieves coaxial and same-polarization transmission from the very beginning of the generation of the frequency-doubled laser, solving the coaxial and polarization-preserving beam combining problem of multiple lasers of the same wavelength mentioned above.

[0028] Furthermore, lasers of the same wavelength include a pump source, a pump light focusing coupling system, and a resonant cavity arranged sequentially along the optical path propagation direction; the resonant cavity outputs left-propagating frequency-doubled light and right-propagating frequency-doubled light from all lasers. Each laser has identical optical elements and structure, the fundamental frequency light oscillating within the cavity has the same wavelength, and the resulting frequency-doubled light has the same wavelength.

[0029] Furthermore, the resonant cavity includes a crystal, a left-end output mirror, and a right-end output mirror, which are located on the same horizontal plane as the first and second reflectors. The laser emitted by the pump source is transmitted to the crystal through the pump light focusing coupling system, generating left-propagating frequency-doubled light that is transmitted to the second reflector through the left-end output mirror, and generating right-propagating frequency-doubled light that is transmitted to the first reflector through the right-end output mirror.

[0030] Furthermore, the resonant cavity in the laser includes one or more of the following: a four-mirror Z-type cavity, a three-mirror V-type cavity, and a two-mirror linear cavity. Under the principle of connecting the frequency-doubled light propagation optical paths of multiple lasers of the same wavelength in series, the resonant cavities of multiple lasers can be selected from four-mirror Z-type cavities, three-mirror V-type cavities, two-mirror linear cavities, or combinations of different cavity types, such as multiple four-mirror Z-type cavities and multiple two-mirror linear cavities.

[0031] Furthermore, a first reflecting mirror is placed vertically near the right-end output mirror of the rightmost laser. The first reflecting mirror is a plane mirror, and the side closest to the laser is coated with a highly reflective dielectric film for frequency-doubled light incident at a 0° angle.

[0032] Furthermore, a second reflecting mirror is tilted on the side of the left-hand output mirror of the leftmost laser, away from the laser itself. This second reflecting mirror is a plane mirror. The frequency-doubled light reflected by the first reflecting mirror is refracted by the second reflecting mirror to the third reflecting mirror, from which the frequency-doubled light is extracted. The side of the second reflecting mirror closest to the laser is coated with a highly reflective dielectric film. The second reflecting mirror can be tilted at 45° relative to the horizontal plane. The frequency-doubled light reflected by the first reflecting mirror is incident at a 45° angle with the second reflecting mirror, and then refracted by the second reflecting mirror into perpendicular light that is transmitted to the third reflecting mirror.

[0033] Furthermore, the third reflecting mirror is located vertically below the second reflecting mirror, receiving and exporting the frequency-doubled light reflected by the second reflecting mirror; the third reflecting mirror is a plane mirror, and a high-reflectivity dielectric film is coated on the side closest to the second reflecting mirror.

[0034] Furthermore, by adding active or passive optical modulation devices to the laser's resonant cavity, the operation can be switched from continuous operation to pulsed operation modes such as Q-switching and mode-locking to meet different application requirements. The optical modulation devices can be placed in the non-frequency-doubled light transmission path to avoid loss in the frequency-doubled light, or in the transmission path with a smaller cavity mode.

[0035] The working principle is as follows: The resonant cavity of the first laser contains fundamental frequency lasers propagating to the left and right. When passing through the frequency doubling crystal, correspondingly, frequency-doubled lasers propagating to the left and right are generated. The frequency-doubled lasers propagating to the left pass directly through the left frequency-doubled output mirror of the first laser to the 45° total reflection mirror. The frequency-doubled lasers propagating to the right pass sequentially through the frequency-doubled output mirrors of the second, third, and so on lasers, and after reaching the frequency-doubled total reflection mirror at the right end of the device, they return along the original path and are reflected out by the 45° total reflection mirror together with the frequency-doubled lasers propagating to the left. Other lasers have the same frequency-doubled light propagation principle. All right-propagating frequency-doubled lasers are adjusted to propagate in the opposite direction (i.e., left-hand) coaxially by the 0° total reflection mirror at the right end of the device. In this way, all frequency-doubled light with the same wavelength and the same linear polarization generated by three or more lasers is reflected out of the cavity in the same direction by the 45° frequency-doubled total reflection mirror at the left end of the device, and then reflected to the desired direction by the external total reflection mirror, realizing polarization-maintaining beam combining of multiple lasers with the same wavelength.

[0036] Example 1: A polarization-maintaining beam combiner employing multiple co-wavelength, four-mirror Z-type, intracavity frequency-doubled deep ultraviolet lasers is shown in the attached diagram. Figure 1 As shown, three or more four-mirror Z-type intracavity frequency-doubled lasers with the same wavelength are arranged in series so that the frequency-doubled lasers they generate can propagate in the same straight line. At the right end of the entire device, a mirror 4 is used to make all the frequency-doubled lasers propagate in the same direction, and at the left end of the entire device, a mirror 5 is used to reflect all the frequency-doubled lasers out of the laser resonant cavity optical path.

[0037] The optical components of the first laser are as follows: pump source 1-1, pump beam focusing and coupling system 1-2, first end mirror of resonant cavity 1-3, laser crystal 1-4, second end mirror of resonant cavity 1-5, third end mirror of resonant cavity 1-6, frequency doubling crystal 1-7, and fourth end mirror of resonant cavity 1-8; the optical components of the second laser are as follows: pump source 2-1, pump beam focusing and coupling system 2-2, first end mirror of resonant cavity 2-3, laser crystal 2-4, second end mirror of resonant cavity 2-5, third end mirror of resonant cavity 2-6, frequency doubling crystal 2-7, and fourth end mirror of resonant cavity 2-8; the optical components of the third laser are as follows: pump source 3-1, pump beam focusing and coupling system 3-2, first end mirror of resonant cavity 3-3, laser crystal 3-4, second end mirror of resonant cavity 3-5, third end mirror of resonant cavity 3-6, frequency doubling crystal 3-7, and fourth end mirror of resonant cavity 3-8; the component numbers of the remaining lasers follow the same pattern. Outside the laser, mirror 4 is a 0° total reflection mirror with frequency doubling, mirror 5 is a 45° total reflection mirror with frequency doubling, and mirror 6 is used to guide the light reflected from the laser resonator cavity. Mirror 6 is a 45° total reflection mirror with frequency doubling.

[0038] Each intracavity frequency-doubled laser has identical components and structure. Its frequency-doubled light propagation paths are arranged in series. The fundamental frequency light oscillating within the cavity has the same wavelength of 522nm, and the generated frequency-doubled light has the same wavelength of 261nm. Pump sources 1-1, 2-1, and 3-1 are 444nm blue laser LDs. Pump light focusing and coupling systems 1-2, 2-2, and 3-2 are lenses with a focal length of 100mm, coupling the pump light into laser crystals 1-4, 2-4, and 3-4 through the first end mirrors 1-3, 2-3, and 3-3 of the resonant cavity, respectively. The first end mirrors 1-3, 2-3, and 3-3 of the resonant cavity are plane mirrors, with a 444nm anti-reflection coating on the end facing the pump source and a 444nm anti-reflection and 522nm high-reflectivity dielectric coating on the end facing the laser resonant cavity. Laser crystals 1-4, 2-4, and 3-4 are Pr:YLF. 3+ The doping concentration is 0.3 at.%, and the size is 3. 3 8mm 3 Both the front and rear light-transmitting end faces are coated with 444nm and 522nm anti-reflection films. The second end mirrors 1-5, 2-5, and 3-5 of the resonant cavity are plano-concave mirrors. The radius of curvature of the concave surface facing the inside of the resonant cavity is 200mm, and they are coated with a 522nm high-reflectivity, 640nm anti-reflection dielectric film, used to change the propagation direction of the laser within the cavity and adjust the cavity mode size. The third end mirrors 1-6, 2-6, and 3-6 of the resonant cavity are plane mirrors. Their right end face is coated with a 522nm high-reflectivity, 261nm anti-reflection dielectric film, and their left end face is coated with a 261nm anti-reflection dielectric film. They serve as high-reflectivity cavity mirrors for the fundamental frequency laser and also as the left-end output mirrors for the frequency-doubled beam of each laser. The frequency-doubled crystals 1-7, 2-7, and 3-7 are all BBO, with a chamfer angle of (…). =48.8°, =0°), with a size of 3 3 10mm 3 Both the front and rear light-transmitting end faces are coated with 522nm and 261nm anti-reflection films. The fourth end mirrors of the resonant cavity, 1-8, 2-8, and 3-8, are plane mirrors. Their right end faces are coated with a 261nm anti-reflection dielectric film, and their left end faces are coated with a 522nm high-reflectivity and 261nm anti-reflection dielectric film. They serve as high-reflectivity cavity mirrors for the fundamental frequency laser and also as the right-end output mirrors for the frequency-doubled beam of each laser. The 0° total reflection mirror for the frequency-doubled beam is placed vertically to the right of the right-end output mirror of the frequency-doubled beam of the rightmost laser. For 0° normal incident light, it is coated with a 522nm high-transmittance dielectric film for the fundamental frequency and a 261nm high-reflectivity dielectric film for the frequency-doubled beam. The reflector 5 is placed at a 45° angle to the left of the left-end output mirror of the frequency-doubled beam of the leftmost laser. For 45° oblique incident light, it is coated with a 522nm high-transmittance dielectric film for the fundamental frequency and a 261nm high-reflectivity dielectric film for the frequency-doubled beam. The reflector 6 is placed after the optical path of the reflector 5. It is coated with a dielectric film that is highly transparent to 522nm fundamental frequency light and highly reflective to 261nm double frequency light for oblique incident light at a 45° angle.

[0039] This polarization-maintaining beam combiner for a four-mirror Z-type, intracavity frequency-doubled deep ultraviolet laser of the same wavelength operates on the following principle: the resonant cavity of the first laser contains a fundamental frequency laser propagating in both forward and reverse directions, with a wavelength... With a wavelength of 522nm, when passing through frequency doubling crystals 1-7, it will generate frequency-doubled laser light propagating to the left and right respectively. With a wavelength of 261nm, the left-directed frequency-doubled laser beam travels directly through resonant cavity end mirrors 1-6 to reflector 5. The right-directed frequency-doubled laser beam travels through mirrors 1-8, 2-6, 2-8, 3-6, 3-8... to reflector 4, is positively reflected, and returns along the original path, coaxial and in the same direction as the left-directed frequency-doubled light. They are then reflected together at reflector 5 and further reflected by another reflector 6 to the desired direction. The frequency-doubled outputs of other lasers (2nd, 3rd, etc.) follow the same transmission principle. In this way, all frequency-doubled laser beams with the same wavelength and linear polarization generated by multiple lasers are reflected in the same direction by reflector 5, achieving polarization-maintaining beam combining of multiple lasers with the same wavelength. The output light is located in the deep ultraviolet band with a wavelength of... The wavelength is 261nm. After deducting the minimal losses of each optical element in the frequency-doubled propagation path (all of which are anti-reflective at 261nm), the output power is basically equal to the frequency-doubled power P generated by each laser. S The sum of these is P. S1 +P S2 +P S3 + P Si This represents the frequency doubling power of the i-th laser.

[0040] Example 2: A polarization-maintaining beam combiner employing multiple same-wavelength, three-mirror V-shaped, intracavity frequency-doubled deep ultraviolet lasers is shown in the attached diagram. Figure 2 As shown, three or more three-mirror V-cavity frequency-doubled lasers with the same wavelength are arranged in series so that the frequency-doubled lasers they generate can propagate in the same straight line. A mirror 7 is used at the right end of the entire device to make all the frequency-doubled lasers propagate in the same direction, and a 45° mirror 8 is used at the left end of the entire device to reflect all the frequency-doubled lasers out of the laser resonant cavity optical path.

[0041] The optical components of the first laser are as follows: pump source 4-1, pump light focusing and coupling system 4-2, first end mirror of resonant cavity 4-3, laser crystal 4-4, second end mirror of resonant cavity 4-5, frequency doubling crystal 4-6, and third end mirror of resonant cavity 4-7; the optical components of the second laser are as follows: pump source 5-1, pump light focusing and coupling system 5-2, first end mirror of resonant cavity 5-3, laser crystal 5-4, second end mirror of resonant cavity 5-5, frequency doubling crystal 5-6, and third end mirror of resonant cavity 5-7; the optical components of the third laser are as follows: pump source 6-1, pump light focusing and coupling system 6-2, first end mirror of resonant cavity 6-3, laser crystal 6-4, second end mirror of resonant cavity 6-5, frequency doubling crystal 6-6, and third end mirror of resonant cavity 6-7; the component numbers of the remaining lasers follow the same pattern. Outside the laser, mirror 7 is a frequency-doubled 0° total reflection mirror, while mirrors 8 and 9 are frequency-doubled 45° total reflection mirrors.

[0042] Each intracavity frequency-doubled laser has identical components and structure. Its frequency-doubled light propagation paths are arranged in series. The fundamental frequency light oscillating within the cavity has the same wavelength of 522nm, and the generated frequency-doubled light has the same wavelength of 261nm. Pump sources 4-1, 5-1, and 6-1 are 444nm blue laser LDs. Pump light focusing and coupling systems 4-2, 5-2, and 6-2 are lenses with a focal length of 100mm, coupling the pump light into laser crystals 4-4, 5-4, and 6-4 through the first end mirrors 4-3, 5-3, and 6-3 of the resonant cavity, respectively. The first end mirrors 4-3, 5-3, and 6-3 of the resonant cavity are plane mirrors, with a 444nm anti-reflection coating on the end facing the pump source and a 444nm anti-reflection and 522nm high-reflectivity dielectric coating on the end facing the laser resonant cavity. Laser crystals 4-4, 5-4, and 6-4 are Pr:YLF. 3+ The doping concentration is 0.3 at.%, and the size is 3. 3 8mm 3Both the front and rear light-transmitting end faces are coated with 444nm and 522nm anti-reflection films. The second end mirrors of the resonant cavity, 4-5, 5-5, and 6-5, are plano-concave mirrors. The concave surface facing the inside of the resonant cavity has a radius of curvature of 200mm and is coated with a 522nm high-reflectivity, 261nm anti-reflection dielectric film. The planar surface facing the outside of the resonant cavity is coated with a 261nm anti-reflection dielectric film. These mirrors serve as both high-reflectivity cavity mirrors for the fundamental frequency laser and right-end output mirrors for the frequency-doubled beam of each laser. The frequency-doubled crystals 4-6, 5-6, and 6-6 are all BBO (Brown-Bonded) with a chamfer angle of (…). =48.8°, =0°), with a size of 3 3 10mm 3 Both the front and rear light-transmitting end faces are coated with 522nm and 261nm anti-reflection films. The third end mirrors 4-7, 5-7, and 6-7 of the resonant cavity are plane mirrors, with their right end faces coated with a 522nm high-reflectivity, 261nm anti-reflection dielectric film, and their left end faces coated with a 261nm anti-reflection dielectric film. They serve as both high-reflectivity cavity mirrors for the fundamental frequency laser and left-end output mirrors for the frequency-doubled beam of each laser. Reflector 7 is placed vertically to the right of the right-end output mirror for the frequency-doubled beam of the rightmost laser, and is coated with a 522nm high-transmittance dielectric film for 0° normal incident light and a 261nm high-reflectivity dielectric film for the frequency-doubled beam. Reflector 8 is placed at a 45° angle to the left of the left-end output mirror for the frequency-doubled beam of the leftmost laser, and is coated with a 522nm high-transmittance dielectric film for 45° oblique incident light and a 261nm high-reflectivity dielectric film for the frequency-doubled beam. The reflector 9 is placed after the optical path of the reflector 8. It is coated with a dielectric film that is highly transparent to 522nm fundamental frequency light and highly reflective to 261nm double frequency light for oblique incident light at a 45° angle.

[0043] This polarization-maintaining beam combiner for a three-mirror V-shaped, intracavity frequency-doubled deep ultraviolet laser of the same wavelength operates on the following principle: The first laser resonant cavity contains a fundamental frequency laser propagating in both forward and reverse directions, with a wavelength... With a wavelength of 522nm, when passing through frequency doubling crystals 4-6, it will generate frequency-doubled laser light propagating to the left and right respectively. With a wavelength of 261nm, the left-directed frequency-doubled laser beam travels directly through resonant cavity end mirrors 4-7 to reflector 8. The right-directed frequency-doubled laser beam travels through mirrors 4-5, 5-7, 5-5, 6-7, 6-5... before reaching reflector 7. After being positively reflected, it returns along the original path, coaxially and in the same direction as the left-directed frequency-doubled light, and is reflected together at reflector 8, then reflected by another reflector 9 to the desired direction. The frequency-doubled outputs of other lasers (2nd, 3rd, etc.) follow the same transmission principle. In this way, all frequency-doubled laser beams with the same wavelength and linear polarization generated by multiple lasers are reflected in the same direction by reflector 8, achieving polarization-maintaining beam combining of multiple lasers with the same wavelength. The output light is located in the deep ultraviolet band with a wavelength of... The wavelength is 261nm. After deducting the minimal losses of each optical element in the frequency-doubled propagation path (all of which are anti-reflective at 261nm), the output power is basically equal to the frequency-doubled power P generated by each laser. S The sum of these is P. S1 +P S2 +P S3 + .

[0044] Example 3: A polarization-maintaining beam combiner employing multiple integrated, frequency-doubled green lasers of the same wavelength is shown in the attached diagram. Figure 3 As shown, three or more integrated self-frequency doubling lasers with the same wavelength are arranged in series so that the frequency-doubled lasers they generate can propagate in the same straight line. A mirror 10 is used at the right end of the entire device to make all the frequency-doubled lasers propagate in the same direction, and a mirror 11 is used at the left end of the entire device to reflect all the frequency-doubled lasers out of the laser resonator optical path.

[0045] The optical components of the first laser are as follows: pump sources 7-1 and 7-2, pump light focusing coupling systems 7-3 and 7-4, pump light reflectors 7-5 and 7-6, and a self-frequency-doubled laser crystal 7-7. The optical components of the second laser are as follows: pump sources 8-1 and 8-2, pump light focusing coupling systems 8-3 and 8-4, pump light reflectors 8-5 and 8-6, and a self-frequency-doubled laser crystal 8-7. The optical components of the third laser are as follows: pump sources 9-1 and 9-2, pump light focusing coupling systems 9-3 and 9-4, pump light reflectors 9-5 and 9-6, and a self-frequency-doubled laser crystal 9-7. The component numbers of the remaining lasers follow the same pattern. Externally, reflector 10 is a 0° total reflection mirror for frequency-doubled light, and reflectors 11 and 12 are 45° total reflection mirrors for self-frequency-doubled light. Reflector 12 is used to guide the light reflected from the laser resonator.

[0046] Each integrated self-frequency-doubled laser has identical components and structure, employs dual-end pumping, and is arranged in series. The fundamental wavelength of the intracavity oscillating light is the same, 1060nm, and the wavelength of the generated frequency-doubled light is the same, 530nm. Pump sources 7-1, 7-2, 8-1, 8-2, 9-1, and 9-2 are LDs with a wavelength of 810nm. Pump light focusing and coupling systems 7-3, 7-4, 8-3, 8-4, 9-3, and 9-4 are lenses with a focal length of 100mm, which couple the pump light into laser crystals 7-7, 8-7, and 9-7 respectively through pump light reflectors 7-5, 7-6, 8-5, 8-6, 9-5, and 9-6. Pump light reflectors 7-5 and 7-6 have an 810nm high-reflectivity, 530nm anti-reflection dielectric film on the side closest to the self-frequency-doubled laser crystal 7-7, and a 530nm anti-reflection dielectric film on the side furthest from the self-frequency-doubled laser crystal 7-7. This is used to change the direction of pump light transmission and allow the generated self-frequency-doubled laser to pass through. Pump light reflectors 8-5 and 8-6 have an 810nm high-reflectivity, 530nm anti-reflection dielectric film on the side closest to the self-frequency-doubled laser crystal 8-7, and a 530nm anti-reflection dielectric film on the side furthest from the self-frequency-doubled laser crystal 8-7. Pump light reflectors 9-5 and 9-6 have an 810nm high-reflectivity, 530nm anti-reflection dielectric film on the side closest to the self-frequency-doubled laser crystal 9-7, and a 530nm anti-reflection dielectric film on the side furthest from the self-frequency-doubled laser crystal 9-7. The self-frequency-doubled laser crystals 7-7, 8-7, and 9-7 are Nd:YCOB. 3+ Doping concentration of 8 at.%, size of 3 3 10mm 3 The chamfer is ( =113°, =35.5°), both the left and right light-transmitting end faces are coated with dielectric films of 530nm and 810nm anti-reflection and 1060nm high reflectivity. These serve as both high-reflectivity cavity mirrors for the fundamental frequency laser and self-frequency-doubled output mirrors for each laser. When outputting sub-frequency-doubled light, the left pump light reflector 7-5 acts as the left output mirror, and the right pump light reflector 7-6 acts as the right output mirror. Reflector 10 is placed vertically to the right of the right pump light reflector of the rightmost laser, and is coated with a dielectric film of 1060nm high transmittance for 0° normal incident light and 530nm high reflectivity for self-frequency-doubled light. Reflector 11 is placed at a 45° angle to the left of the left pump light reflector 7-5 of the leftmost laser, and is coated with a dielectric film of 1060nm high transmittance for 45° oblique incident light and 530nm high reflectivity for self-frequency-doubled light. The reflector 12 is placed after the optical path of the reflector 11, and is coated with a dielectric film that is highly transparent to 1060nm fundamental frequency light and highly reflective to 530nm self-frequency doubling light for oblique incident light at a 45° angle.

[0047] This polarization-maintaining beam combining device for a single-wavelength, integrated self-frequency-doubled green laser operates on the following principle: the first laser's self-frequency-doubled laser crystal 7-7 contains a fundamental frequency laser propagating in both forward and reverse directions, with a wavelength... With a wavelength of 1060nm, it simultaneously generates self-frequency-doubled laser light propagating to both the left and right directions under the self-frequency doubling effect. The self-frequency-doubled laser, with a wavelength of 530nm, travels directly from left to right through pump light reflectors 7-5 to reflector 11. The self-frequency-doubled laser traveling from right to left travels through reflectors 7-6, 8-5, 8-7, 8-6, 9-5, 9-7, 9-6... to reflector 10. After being positively reflected, it returns along the same path, coaxially and in the same direction as the self-frequency-doubled laser traveling from left to right, and is reflected together at reflector 11. It is then reflected again by another reflector 12 to the desired direction. The self-frequency-doubled laser outputs from other lasers (2nd, 3rd, etc.) follow the same transmission principle. In this way, all self-frequency-doubled lasers with the same wavelength and linear polarization generated by multiple lasers are reflected in the same direction by reflector 11, achieving polarization-maintaining beam combining of multiple lasers with the same wavelength. The output light is located in the green light band with a wavelength of... At 530nm, after deducting the minimal losses of each optical element in the self-frequency-doubled propagation optical path (all of which are anti-reflective at 530nm), the output power is essentially equal to the self-frequency-doubled power P generated by each laser. S The sum of these is P. S1 +P S2 +P S3 + .

[0048] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0049] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polarization-maintaining beam combining device for multiple lasers of the same wavelength, characterized in that, It includes at least two lasers of the same wavelength and three mirrors; The laser outputs left-propagating frequency-doubled light and right-propagating frequency-doubled light; the right-propagating frequency-doubled light from all lasers propagates in series along the same straight line to the first reflecting mirror, and the left-propagating frequency-doubled light propagates in series along the same straight line to the second reflecting mirror. The first mirror reflects the right-hand frequency-doubled light to the second mirror, the second mirror reflects all the frequency-doubled light to the third mirror, and the third mirror outputs polarization-maintaining combined light.

2. The polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 1, characterized in that, The first reflector is a 0° total reflection mirror, and the second and third reflectors are 45° total reflection mirrors. The first and second reflectors are positioned on the same horizontal plane as the frequency-doubled light output by the laser. The first reflector is positioned perpendicular to the frequency-doubled light transmission path, and the second and third reflectors are at a 45° angle to the frequency-doubled light transmission path, with the second and third reflectors being perpendicular to each other.

3. The polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 1, characterized in that, The lasers of the same wavelength include a pump source, a pump light focusing coupling system, and a resonant cavity arranged sequentially along the optical path transmission direction; the resonant cavities of all lasers output left-propagating frequency-doubled light and right-propagating frequency-doubled light; the resonant cavity includes a crystal, a left-end output mirror, and a right-end output mirror, which are located on the same horizontal plane as the first reflector and the second reflector. The laser emitted by the pump source is transmitted to the crystal through the pump light focusing coupling system, generating left-propagating frequency-doubled light which is transmitted to the second reflector through the left-end output mirror, and generating right-propagating frequency-doubled light which is transmitted to the first reflector through the right-end output mirror.

4. The polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 3, characterized in that, The resonant cavity in a laser includes one or more of the following: a four-mirror Z-type cavity, a three-mirror V-type cavity, and a two-mirror linear cavity.

5. The polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 4, characterized in that, When a four-mirror Z-type resonant cavity is selected, it includes a first end mirror, a laser crystal, a second end mirror, a third end mirror, a frequency doubling crystal, and a fourth end mirror arranged along the optical path transmission direction. The second and third end mirrors are tilted. The first end mirror receives the laser light transmitted from the pump light focusing coupling system and transmits it to the laser crystal. The laser light output from the laser crystal is refracted by the second end mirror to the third end mirror below. The third end mirror refracts the laser light onto the frequency doubling crystal, which is horizontally positioned. The left-propagating frequency-doubled light output from the left end of the frequency doubling crystal is output through the third end mirror, and the right-propagating frequency-doubled light output from the right end is output through the fourth end mirror. The third end mirror serves as the left-end output... The output mirror consists of four mirrors: the fourth mirror serves as the right-end output mirror; the first mirror is a plane mirror with an anti-reflection coating on the side closest to the pump light focusing coupling system and a highly reflective dielectric coating on the side closest to the laser crystal; both ends of the laser crystal are coated with anti-reflection coatings; the second mirror is a plano-concave mirror with a highly reflective dielectric coating on the concave side closest to the laser crystal; the third mirror is a plane mirror with a highly reflective dielectric coating on the side closest to the frequency doubling crystal and an anti-reflection coating on the side furthest from the frequency doubling crystal; both ends of the frequency doubling crystal are coated with anti-reflection coatings; and the fourth mirror is a plane mirror with a highly reflective dielectric coating on the side closest to the frequency doubling crystal and an anti-reflection coating on the side furthest from the frequency doubling crystal.

6. The polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 4, characterized in that, When a three-mirror V-shaped cavity is selected as the resonant cavity, it includes a first end mirror, a laser crystal, a second end mirror, a frequency doubling crystal, and a third end mirror arranged along the optical path transmission direction. The pump source, pump light focusing coupling system, first end mirror, laser crystal, and second end mirror are all tilted. The first end mirror receives the laser light transmitted from the pump light focusing coupling system and transmits it to the laser crystal. The laser light output from the laser crystal is refracted by the second end mirror to the frequency doubling crystal. The left-propagating frequency-doubled light output from the left end of the frequency doubling crystal is output through the third end mirror, and the right-propagating frequency-doubled light output from the right end is output. The output is through the second end mirror; the first end mirror is a plane mirror, with an anti-reflection coating on the side near the pump light focusing coupling system and a high-reflectivity dielectric coating on the side near the laser crystal; both ends of the laser crystal are coated with anti-reflection coatings; the second end mirror is a plano-concave mirror, with a high-reflectivity dielectric coating on the concave side near the laser crystal and an anti-reflection coating on the planar side away from the laser crystal; both ends of the frequency doubling crystal are coated with anti-reflection coatings; the third end mirror is a plane mirror, with a high-reflectivity dielectric coating on the side near the frequency doubling crystal and an anti-reflection coating on the side away from the frequency doubling crystal.

7. The polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 4, characterized in that, When a two-mirror linear cavity is selected as the resonant cavity, the laser includes two sets of pump sources and two sets of pump beam focusing coupling systems. The resonant cavity includes a first pump beam mirror, a self-frequency doubling laser crystal, and a second pump beam mirror. The laser output from one set of pump sources and pump beam focusing coupling systems is transmitted to the self-frequency doubling laser crystal via the first pump beam mirror, and the laser output from the other set of pump sources and pump beam focusing coupling systems is transmitted to the self-frequency doubling laser crystal via the second pump beam mirror. The left-propagating frequency-doubled light output from the left end of the self-frequency doubling laser crystal is output via the first pump beam mirror, and the right-propagating frequency-doubled light output from the right end is output via the second pump beam mirror. The first pump beam mirror serves as the left-end output mirror, and the second pump beam mirror serves as the right-end output mirror. The first and second pump beam mirrors are both plane mirrors, with an anti-reflection coating on the side away from the self-frequency doubling laser crystal and a high-reflectivity dielectric coating on the side closer to the self-frequency doubling laser crystal. High-reflectivity dielectric coatings are applied to both ends of the self-frequency doubling laser crystal.

8. The polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 3, characterized in that, A first reflecting mirror is placed vertically near the right-end output mirror of the rightmost laser. The first reflecting mirror is a plane mirror, and the side closest to the laser is coated with a highly reflective dielectric film for frequency-doubled light incident at a 0° angle.

9. A polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 3, characterized in that, A second reflector is placed at an angle on the left side of the laser output mirror, away from the laser. The second reflector is a plane mirror. The frequency-doubled light reflected by the first reflector is refracted by the second reflector to the third reflector, and the frequency-doubled light is exported by the third reflector. The side of the second reflector closest to the laser is coated with a highly reflective dielectric film.

10. A polarization-maintaining beam combining device for multiple lasers of the same wavelength according to claim 3, characterized in that, The third reflecting mirror is located vertically below the second reflecting mirror. It receives and outputs the frequency-doubled light reflected by the second reflecting mirror. The third reflecting mirror is a plane mirror, and a high-reflectivity dielectric film is coated on the side closest to the second reflecting mirror.

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