Output type optical isolator

Abstract

The utility model relates to the technical field of optical equipment, in particular to an output type optical isolator, which comprises an optical rotation sheet with a groove mechanism and a small-hole diaphragm. When returning light appears, the plano-convex lens converges light spots of the returning light for the first time, the small-hole diaphragm partially blocks the converged light spots, and the energy of the returning light is reduced; the biconcave lens is used for carrying out secondary convergence on the blocked light spots; the second polarization splitting prism divides the secondarily converged light spots into reverse P light and reverse S light; under the combined action of the magnetic rotation crystal and an external magnetic field, the reverse P light and the reverse S light rotate anticlockwise; the optical rotation sheet performs first clockwise rotation on the reverse P light after counterclockwise rotation, and the groove mechanism of the optical rotation sheet completely blocks the reverse S light after counterclockwise rotation; finally, the rotated reverse P light and the blocked reverse S light cannot pass through the first polarization splitting prism to be combined, so that the reverse P light and the blocked reverse S light are isolated, and the damage of the returned light to a front-end laser element is avoided.

Description

Technical Field

[0001] This utility model relates to the field of optical equipment technology, specifically to an output-type optical isolator. Background Technology

[0002] Optical isolators are key passive optical devices widely used in optical communication and laser systems. Their main function is to allow optical signals to travel in a single direction while blocking the propagation of reflected light, thereby protecting lasers and other optical components from damage caused by reflected light and improving optical transmission efficiency and system stability.

[0003] Existing fiber-to-free-space optical isolators, as an important branch of output-type optical isolators, while enabling unidirectional light transmission, have significant shortcomings when handling reflected light incident at extreme angles. When the reflected light is obliquely incident, some energy directly acts on the collimator and returns to the fiber, posing a potential threat to the optical components inside the laser. For example, assuming a reflected light power of 10W and an isolation of 13dB, the power returning to the fiber is approximately 0.5W, which is still a potential threat to internal laser components. Currently, the dynamic isolation of such optical isolators on the market is generally between 13-20dB, which is insufficient to meet the higher isolation requirements of high-power laser systems.

[0004] Therefore, there is an urgent need for a new type of optical isolator that can effectively isolate incident light returning at extreme angles and improve dynamic isolation. Utility Model Content

[0005] In view of this, the present invention provides an output-type optical isolator to solve the problem that when existing fiber-free space type optical isolators handle return light incident at extreme angles, some energy will directly act on the collimator and return to the optical fiber through the collimator, posing a potential threat to the optical components inside the laser.

[0006] This utility model provides an output type optical isolator, which includes: a first polarizing beam splitter, a rotator, a magneto-optical rotator crystal, an external magnetic field, a second polarizing beam splitter, a biconcave lens, a pinhole aperture, and a plano-convex lens arranged sequentially along the forward optical path; the rotator is provided with a non-light-transmitting groove mechanism.

[0007] In the reverse optical path:

[0008] The plano-convex lens is used to converge the reflected light spot of the optical isolator once;

[0009] The pinhole aperture is used to partially block the returning light spot after one convergence.

[0010] The biconcave lens is used to refocus the reflected light spot after partial obstruction.

[0011] The second polarizing beam splitter is used to split the returned light spot after secondary focusing into reverse P-beam and reverse S-beam;

[0012] The magneto-optical crystal, together with the applied magnetic field, is used to rotate the reverse P-beam and the reverse S-beam counterclockwise.

[0013] The optical rotator is used to perform a first clockwise rotation on the reverse P-beam after counterclockwise rotation, and the groove mechanism on the optical rotator is used to completely block the reverse S-beam after counterclockwise rotation; the reverse P-beam after the first clockwise rotation and the reverse S-beam after complete blocking are isolated outside the first polarizing beam splitter.

[0014] The above scheme effectively isolates the reflected light signal through the synergistic effect of a plano-convex lens, a pinhole aperture, a biconcave lens, and a second polarizing beam splitter, preventing it from returning to the optical fiber and protecting the front-end laser components. Firstly, the pinhole aperture partially blocks the reflected light spot, and the groove mechanism on the rotator completely blocks the reflected S-beam, further enhancing the isolation effect. This prevents reflected light incident at extreme angles from recoupling back into the optical fiber, achieving the effect of isolating reflected light incident at extreme angles and significantly reducing the risk of damage to the front-end laser components.

[0015] In one optional embodiment, the groove mechanism includes a first groove, which is disposed at the middle position of the right light-transmitting surface of the optical rotor.

[0016] In the reverse optical path, the first groove is used to completely block the reverse S-beam at the first extreme incident angle after counterclockwise rotation; the reverse P-beam after the first clockwise rotation and the reverse S-beam after the first complete blocking are isolated outside the first polarizing beam splitter.

[0017] The above scheme further clarifies the specific structure of the groove mechanism. By setting the first groove, it is possible to completely block the reverse S-ray at the first extreme incident angle after counterclockwise rotation, thereby enhancing the isolation capability for light returning at a specific angle and further improving the isolation effect of the optical isolator.

[0018] In one optional embodiment, the groove mechanism further includes a second groove, which is disposed at the middle position of the left light-transmitting surface of the optical rotor.

[0019] In the reverse optical path, the second groove is used to completely block the reverse S-beam at the second extreme incident angle after counterclockwise rotation; the reverse P-beam after the first clockwise rotation and the reverse S-beam after the second complete blocking are isolated outside the first polarizing beam splitter; the second extreme incident angle is greater than the first extreme incident angle.

[0020] The above solution adds a second groove to the first groove, which can completely block the reverse S-ray at the second extreme incident angle after counterclockwise rotation, further expanding the isolation range for light returning from different extreme incident angles, improving the isolation capability of the optical isolator for light returning from extreme incident angles, and making the performance of the optical isolator even better.

[0021] In one alternative embodiment, the groove width of the groove mechanism is determined by the upper and lower light-transmitting apertures of the first polarizing beam splitter.

[0022] The above scheme clarifies that the groove width of the groove mechanism is determined by the upper and lower light-passing apertures of the first polarizing beam splitter, making the groove width design more reasonable and better matching the structure of the first polarizing beam splitter, ensuring the normal operation of the optical isolator, and at the same time ensuring effective blocking of the reflected light.

[0023] In one optional embodiment, the groove width of the groove mechanism is less than the difference between the light speed splitting distance of the first polarizing beam splitter and the upper and lower light-passing apertures.

[0024] The above scheme further limits the groove width of the groove mechanism to be smaller than the beam splitting distance of the first polarizing beam splitter and the difference between the upper and lower light-passing apertures. This maximizes the groove width while ensuring normal light transmission of the optical isolator, thereby improving the blocking effect on the backlight and further enhancing the isolation performance of the optical isolator.

[0025] In one optional embodiment, the optical isolator further includes an optical fiber and a lens; the optical fiber is located at the starting end of the optical isolator; the lens is located between the optical fiber and the first polarizing beam splitter.

[0026] In the forward optical path:

[0027] The optical fiber is used to introduce the forward optical signal into the optical isolator;

[0028] The lens is used to collimate the forward light signal output from the optical fiber once, and the collimated forward light signal enters the first polarizing beam splitter.

[0029] The above solution, by adding optical fiber and lens at the starting end of the optical isolator, can effectively introduce the forward optical signal into the optical isolator and collimate it once, so that the optical signal can better enter the subsequent optical components, thereby improving the transmission quality and stability of the optical signal and enhancing the overall performance of the optical isolator.

[0030] In one alternative implementation, in the forward optical path:

[0031] The first polarizing beam splitter is used to split the forward light signal after it has been collimated by the lens into forward P-beam and forward S-beam;

[0032] The optical rotator is used to perform a second clockwise rotation on the positive P-beam and the positive S-beam;

[0033] The magneto-optical crystal, together with the applied magnetic field, is used to perform a third clockwise rotation on the positive P-beam and positive S-beam after the second clockwise rotation;

[0034] The second polarizing beam splitter is used to re-bend the positive P-beam and the positive S-beam after the third clockwise rotation;

[0035] The biconcave lens is used to expand the combined beam.

[0036] The pinhole aperture is used to limit the quality of the combined beam after beam expansion.

[0037] The plano-convex lens is used to perform secondary collimation on the mass-limited combined beam to form a collimated and magnified outgoing light spot.

[0038] The above scheme uses various components in the forward optical path to split, rotate, combine, expand, quality limit, and collimate the forward optical signal, ultimately forming a collimated and amplified outgoing light spot. This improves the transmission quality and stability of the optical signal and ensures the efficient transmission and stable operation of the optical isolator in the forward optical path.

[0039] In one optional implementation, the counterclockwise rotation angle is the same as the first clockwise rotation angle;

[0040] The second clockwise rotation angle is the same as the third clockwise rotation angle.

[0041] The above scheme limits the rotation angle of counterclockwise rotation to be the same as the first clockwise rotation angle, and the rotation angle of second clockwise rotation to be the same as the third clockwise rotation angle, ensuring that the polarization rotation effect of the optical signal is consistent in the forward and reverse optical paths, thus guaranteeing the performance stability of the optical isolator.

[0042] In one optional embodiment, the optical isolator further includes a light-passing aperture located between the second polarizing beam splitter and the biconcave lens;

[0043] In the reverse optical path, the light-passing aperture is used to reverse-limit the returned light spot after the secondary convergence of the biconcave lens, and the reverse-limited returned light spot enters the second polarizing beam splitter.

[0044] In the forward optical path, the light-passing aperture is used to forward confine the combined beam after the second polarizing beam splitter has combined the beams, and the forward-confined combined beams enter the biconcave lens.

[0045] The above scheme, by setting a light-passing hole between the second polarizing beam splitter and the biconcave lens, can reverse the backlight spot in the reverse optical path and forward the combined beam in the forward optical path, thereby improving the optical isolator's control over optical signals and enhancing its isolation effect and performance stability.

[0046] In one optional embodiment, the applied magnetic field includes a first magnet and a second magnet; the first magnet is located below the magneto-optical crystal, and the second magnet is located above the magneto-optical crystal.

[0047] The first magnet and the second magnet provide an external magnetic field for the magneto-optical crystal, causing the magneto-optical crystal to produce the Faraday effect.

[0048] The above scheme provides a stable external magnetic field for the magneto-optical crystal by setting a first magnet and a second magnet, ensuring that the magneto-optical crystal can stably generate the Faraday effect, thereby improving the reliability and performance stability of the optical isolator.

[0049] The technical solution provided by this utility model can include the following beneficial effects:

[0050] This invention effectively isolates the reflected light signal by utilizing the synergistic effect of a plano-convex lens, a pinhole aperture, a biconcave lens, and a second polarizing beam splitter, preventing it from returning to the optical fiber and protecting the front-end laser components. Firstly, the pinhole aperture partially blocks the reflected light spot, and the groove mechanism on the rotator completely blocks the reflected S-beam, further enhancing the isolation effect. This prevents reflected light incident at extreme angles from recoupling back into the optical fiber, achieving the effect of isolating reflected light incident at extreme angles and significantly reducing the risk of damage to the front-end laser components. Attached Figure Description

[0051] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1 A schematic diagram of the forward transmission optical path of an existing fiber-to-free space isolator is shown.

[0053] Figure 2 This illustrates the reverse isolation optical path of an existing fiber-to-free-space isolator;

[0054] Figure 3 This diagram illustrates the reverse transmission optical path when the return beam is obliquely incident on the fiber-free space isolator.

[0055] Figure 4 This is a schematic diagram of the structure of an output-type optical isolator according to an embodiment of the present utility model;

[0056] Figure 5 This is a schematic diagram of the groove depth and groove width of the groove mechanism according to an embodiment of the present utility model;

[0057] Figure 6 This is a schematic diagram illustrating the setting of the pinhole aperture according to an embodiment of the present utility model;

[0058] Among them, there are optical fiber-1, lens-2, first polarizing beam splitter-3, optical rotator-4, magneto-optical rotator-7, first magnet-5, second magnet-6, second polarizing beam splitter-8, light-passing aperture-9, biconcave lens-10, pinhole aperture-11, plano-convex lens-12, reflected light spot-13, collimator-14, optical rotator-15, collimated light spot-16, and reflected light spot-17. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0060] An optical isolator is a passive optical device that allows only unidirectional light to pass through. Its operating principle is based on the non-reciprocity of Faraday rotation. Light reflected back from an optical fiber can be effectively isolated by the optical isolator. Optical isolators primarily utilize the Faraday effect of magneto-optical crystals. The characteristics of an optical isolator are: low forward insertion loss, high reverse isolation, and high return loss. An optical isolator is a passive device that allows light to pass in one direction while blocking light from passing in the opposite direction. Its function is to restrict the direction of light, ensuring that light can only propagate in one direction. Light reflected back from an optical fiber can be effectively isolated by the optical isolator, improving optical wave transmission efficiency.

[0061] The basic components of an optical isolator consist of two birefringent crystals, an optical rotator, a magneto-optical rotator, and an external magnetic field. The optical axes of the two birefringent crystals are at a 45° angle. Its forward transmission path includes: a beam of positively linearly polarized light passes through the first birefringent crystal and is split into o-rays and e-rays for separate transmission. After passing through the optical rotator, both beams rotate clockwise by 45° simultaneously (when viewed against the direction of forward propagation, the same applies below). Then, under the influence of the magneto-optical rotator and the external magnetic field, they rotate clockwise again by 45°. At this point, the two beams have rotated by 90° respectively, and their polarization states have interchanged; the o-ray becomes the e-ray, and the e-ray becomes the o-ray. After passing through the second birefringent crystal, the beams are combined and emitted. Its reverse isolation optical path includes: a beam of reverse linearly polarized light is split into o-ray and e-ray after passing through the first birefringent crystal and transmitted separately. Under the action of the magneto-optical rotator crystal and the external magnetic field, it rotates counterclockwise by 45° (when viewed against the direction of light propagation, the same below). Then, after passing through the optical rotator, the two beams rotate clockwise by 45° simultaneously. At this time, the two beams have rotated by 0° respectively, and their polarization states have not changed. The o-ray is still the o-ray, and the e-ray is still the e-ray. After passing through the second birefringent crystal, they cannot be combined and are deviated, thus achieving the effect of isolating the reverse light.

[0062] Currently, existing fiber-to-free-space isolators are passive devices consisting of a collimator, a polarizing beam splitter (PBS), an optical rotator crystal, a magneto-optical rotator crystal (TGG), an external magnetic field, and a beam expander. They enable light to be expanded and output from the fiber to free space, while blocking the return light (its blocking capability is judged by the degree of isolation). The output beam is characterized by a large spot diameter and a small divergence angle. A schematic diagram of the forward transmission optical path of this existing fiber-to-free-space isolator is shown below. Figure 1As shown. Fiber 1 introduces a light source, and collimator 14 converts the light emitted from the light source into collimated light. This light is then split into positive P-beams and positive S-beams by the first polarizing beam splitter 3. The positive S-beam is transmitted, and the positive P-beam is reflected. Under the action of optical rotator crystal 15, both beams rotate 45° clockwise. Then, under the action of an external magnetic field (including the first magnet 5 and the second magnet 6) and the magneto-optical rotator crystal 7, they rotate 45° clockwise again. At this point, the two beams have rotated 90°, and their polarization states have interchanged. They are then combined and emitted by the second polarizing beam splitter 8. After further beam expansion and collimation by the biconcave lens 10 and the plano-convex lens 12, a collimated and magnified collimated spot 16 is formed.

[0063] The reverse isolation optical path of the existing fiber-to-free space isolator is as follows: Figure 2 As shown, the reflected light spot 17 is converged into a small spot by the plano-convex lens 12 and the biconcave lens 10. It is then split into a reverse P-beam and a reverse S-beam by the second polarizing beam splitter. The reverse S-beam is transmitted, and the reverse P-beam is reflected. Under the action of the external magnetic field (including the first magnet 5 and the second magnet 6) and the magneto-optical oscillator crystal 7, the two beams rotate counterclockwise by 45°. Then, under the action of the optical oscillator crystal 15, they rotate clockwise by 45°. At this point, the two beams have rotated by 0°, and their polarization states have not changed. Finally, they cannot be coupled back to the collimator 14 by the first polarizing beam splitter 3, thus achieving the effect of isolating the reverse light.

[0064] Currently, the dynamic isolation of fiber-to-free space isolators on the market is between 13-20 dB. Dynamic isolation refers to the isolator's ability to block return light from all directions. Using current technology, for extreme customer applications, assuming a return light power P1 of 10W, if the dynamic isolation ISO of the optical isolator is 13 dB, according to the isolation calculation formula:

[0065] ISO = 10log(P1 / P2);

[0066] P1 represents the returned light power, and P2 represents the power returning to the collimator. Therefore, P2 can be calculated to be 0.5W, meaning that approximately 0.5W of power returns to the fiber optic cable. This poses a potential threat to the optical components inside the laser. Therefore, please refer to [further details needed]. Figure 3The diagram shows the reverse transmission optical path when the reflected light spot 13 is obliquely incident on the fiber-free space isolator. If the reflected light (i.e., the backlight) is obliquely incident on the fiber-free space isolator, some of its energy will directly act on the collimator 14 as it passes through the isolator, and then return to the fiber, thereby damaging the optical components inside the customer's laser. Based on this, this invention provides an output-type optical isolator that partially blocks the reflected light spot 13 through a small aperture 11, and the groove mechanism on the optical rotator 4 can completely block the reverse S-ray, further enhancing the isolation effect on the reflected light. This prevents the reflected light incident at extreme angles from recoupling back to the fiber 1, achieving the effect of isolating the reflected light incident at extreme angles and greatly reducing the risk of damage to the front-end laser components caused by the reflected light.

[0067] This embodiment provides an output-type optical isolator. Figure 4 This is a schematic diagram of the structure of an output-type optical isolator according to an embodiment of the present utility model, as shown below. Figure 4 As shown, the optical isolator includes: a first polarizing beam splitter 3, a rotator 4, a magneto-optical rotator crystal 7, an external magnetic field, a second polarizing beam splitter 8, a biconcave lens 10, a pinhole aperture 11, and a plano-convex lens 12 arranged sequentially along the forward optical path; the rotator 4 is provided with a non-light-transmitting groove mechanism.

[0068] In the reverse optical path:

[0069] The plano-convex lens 12 is used to converge the reflected light spot 13 of the optical isolator once;

[0070] The pinhole aperture 11 is used to partially block the returning light spot 13 after one convergence.

[0071] The biconcave lens 10 is used to refocus the partially blocked return light spot 13;

[0072] The second polarizing beam splitter 8 is used to split the returned light spot 13 after secondary focusing into reverse P-beam and reverse S-beam;

[0073] The magneto-optical crystal 7, together with the applied magnetic field, is used to rotate the reverse P-ray and the reverse S-ray counterclockwise.

[0074] The optical rotator 4 is used to perform a first clockwise rotation on the reverse P-beam after counterclockwise rotation. The groove mechanism on the optical rotator 4 is used to completely block the reverse S-beam after counterclockwise rotation. The reverse P-beam after the first clockwise rotation and the reverse S-beam after complete blocking are isolated outside the first polarizing beam splitter 3.

[0075] Furthermore, in the forward optical path of the optical isolator, the forward optical signal sequentially passes through the first polarizing beam splitter 3, the optical rotator 4, the magneto-optical rotator crystal 7, the applied magnetic field, the second polarizing beam splitter 8, the biconcave lens 10, the pinhole aperture 11, and the plano-convex lens 12. These components work together to ensure the smooth transmission of the forward optical signal, completing the beam expansion output from fiber 1 to free space, and meeting requirements such as a large spot diameter and a small divergence angle. Specifically, the first polarizing beam splitter 3 splits the light into forward P-beams and forward S-beams. The optical rotator 4 and the magneto-optical rotator crystal 7 change the polarization state of the forward optical signal under the action of the magnetic field. The second polarizing beam splitter 8 combines the beams, and the subsequent lens 2 adjusts the beam. The non-light-passing groove mechanism on the optical rotator 4 does not affect light propagation during normal transmission in the forward optical path, but plays a crucial role in the reverse optical path. In the reverse optical path of the optical isolator, after the reverse light enters the isolator, the plano-convex lens 12 first converges the returned light spot 13, making the spot smaller and the energy more concentrated, facilitating subsequent processing. Next, the pinhole aperture 11 partially blocks the converged spot, reducing the energy of the returned light and mitigating its potential harm to front-end components. The returned light spot 13, after being blocked by the pinhole aperture 11, is then converged a second time by the biconcave lens 10, further altering the light propagation direction and spot characteristics. Then, the second polarizing beam splitter 8 separates the secondary converged returned light spot 13 into reverse P-beams and reverse S-beams, preparing for subsequent processing of light with different polarization states. The magneto-optical rotator crystal 7, acting in conjunction with an external magnetic field, causes the reverse P-beams and reverse S-beams to rotate counterclockwise. The optical rotator 4 then performs a first clockwise rotation on the counterclockwise rotated reverse P-beam, while its groove mechanism completely blocks the counterclockwise rotated reverse S-beam. Since the polarization state and propagation path of the reverse P-beam and the reverse S-beam change after these operations, the reverse P-beam after the first clockwise rotation and the completely blocked reverse S-beam cannot be combined through the first polarization beam splitter 3, thus being isolated outside the first polarization beam splitter 3, achieving the purpose of isolating the reflected light and protecting the front-end laser components from damage by the reflected light.

[0076] In one alternative embodiment, the groove mechanism includes a first groove, which is disposed at the middle position of the right light-transmitting surface of the optical rotor 4.

[0077] In the reverse optical path, the first groove is used to completely block the reverse S-beam at the first extreme incident angle after counterclockwise rotation; the reverse P-beam after the first clockwise rotation and the reverse S-beam after the first complete blocking are isolated outside the first polarizing beam splitter 3.

[0078] Furthermore, the groove mechanism includes a first groove, which is positioned in the middle of the light-transmitting surface on the right side of the optical rotator 4. This groove precisely intercepts reverse S-beams at specific angles, preventing them from interfering with the forward light path. In the reverse light path, the direction of light propagation is opposite to that of the forward light path. After passing through the magneto-optical rotator crystal 7 and the applied magnetic field, the reverse S-beams rotate counterclockwise by a certain angle (e.g., 45°). When these reverse S-beams enter the optical rotator 4 at the first limiting incident angle, the first groove plays a crucial role. Because the first groove is located in a specific middle position and has non-transmitting properties, it can completely block the reverse S-beams at the first limiting incident angle after counterclockwise rotation. This means that as long as the reverse S-beams are incident at this limiting angle, they will be intercepted by the first groove and cannot continue to propagate. After the reverse P-beams undergo counterclockwise rotation by the magneto-optical rotator crystal 7 and the applied magnetic field, they are then rotated clockwise by the optical rotator 4. The reverse S-beams are completely blocked by the first groove. Because the polarization state and propagation path of the two beams are changed after such processing, the reverse P beam after the first clockwise rotation and the reverse S beam after the first complete blockage cannot be combined through the first polarization beam splitter 3. They are successfully isolated outside the first polarization beam splitter 3, thereby effectively avoiding damage to the front-end optical components (such as lasers) by the reflected light, and ensuring the normal operation of the optical isolator and the stability of the optical system.

[0079] In one alternative embodiment, the groove mechanism further includes a second groove, which is disposed at the middle position of the left light-transmitting surface of the optical rotor 4;

[0080] In the reverse optical path, the second groove is used to completely block the reverse S-beam at the second extreme incident angle after counterclockwise rotation; the reverse P-beam after the first clockwise rotation and the reverse S-beam after the second complete blocking are isolated outside the first polarizing beam splitter 3; the second extreme incident angle is greater than the first extreme incident angle.

[0081] Furthermore, in addition to the first groove, a second groove is added to the groove mechanism, and the second groove is located in the middle of the light-transmitting surface on the left side of the optical rotator 4. In the reverse light path, the direction of light propagation is opposite to that of the forward light path. After passing through the magneto-optical rotator crystal 7 and the applied magnetic field, the reverse S-beam will rotate counterclockwise by a certain angle. When the reverse S-beam enters the optical rotator 4 at the second limiting angle of incidence, the second groove plays a crucial role. Because the second groove is located in a specific middle position and has non-transmitting characteristics, it can completely block the reverse S-beam at the second limiting angle of incidence after counterclockwise rotation. That is to say, as long as the reverse S-beam is incident at this larger limiting angle, it will be intercepted by the second groove and cannot continue to propagate. It can be seen that the first groove mainly blocks the reverse S-beam at the first limiting angle of incidence (relatively small), while the second groove blocks the reverse S-beam at the second limiting angle of incidence (greater than the first limiting angle of incidence). The two work together to form an all-round interception of reverse S-beams at different angles. This synergistic effect enables the optical isolator to handle a wider range of return beams, greatly improving its ability to isolate reverse S-beams.

[0082] In one optional embodiment, the groove width of the groove mechanism is determined by the upper and lower light-transmitting apertures of the first polarizing beam splitter 3. The groove width of the groove mechanism is less than the difference between the optical speed splitting distance of the first polarizing beam splitter 3 and the upper and lower light-transmitting apertures. The groove depth is between 0.1 mm and 0.5 mm, and the groove width is between 0.45 mm and 0.05 mm.

[0083] Furthermore, the groove width of the groove mechanism is determined by the upper and lower apertures of the first polarizing beam splitter prism 3. The first polarizing beam splitter prism 3 is responsible for polarizing and splitting light in the optical isolator. The size of the upper and lower apertures (including the upper and lower apertures) limits the propagation path and spatial range of light within the prism. To ensure the normal operation of the optical isolator, the groove width of the groove mechanism needs to be designed based on the upper and lower apertures of the first polarizing beam splitter prism 3 to avoid interfering with the normal light path while effectively blocking reflected light. The groove width of the groove mechanism is less than the difference between the beam splitting distance of the first polarizing beam splitter prism 3 and the upper and lower apertures. The beam splitting distance refers to the distance between the light rays passing through the upper aperture and the lower aperture of the first polarizing beam splitter prism 3. If the groove width is too large, exceeding this difference, some light in the normal light path may be cut off, affecting the light transmission efficiency; conversely, if the groove width is too small, it may not be able to adequately block reflected light, reducing the isolation performance of the optical isolator.

[0084] In one optional embodiment, the optical isolator further includes an optical fiber 1 and a lens 2; the optical fiber 1 is located at the starting end of the optical isolator; the lens 2 is located between the optical fiber 1 and the first polarizing beam splitter 3.

[0085] In the forward optical path:

[0086] The optical fiber 1 is used to introduce the forward optical signal into the optical isolator;

[0087] The lens 2 is used to collimate the forward optical signal output from the optical fiber 1 once, and the collimated forward optical signal enters the first polarizing beam splitter 3.

[0088] Furthermore, fiber 1 is positioned at the beginning of the optical isolator, serving as the entry point for the optical signal. Lens 2 is located between fiber 1 and the first polarizing beam splitter 3, ensuring that the optical signal undergoes necessary processing before entering the core optical component (first polarizing beam splitter 3) of the optical isolator. In the forward optical path, the primary function of fiber 1 is to introduce external forward optical signals into the optical isolator. Fiber 1 possesses excellent optical transmission characteristics, effectively transmitting optical signals from the light source to the optical isolator, providing optical input for subsequent optical processing. Lens 2 receives the forward optical signal output from fiber 1 and performs collimation on it. Since the light emitted from fiber 1 is typically divergent, it hinders the precise processing of light by subsequent optical components. Lens 2 performs collimation by converting the divergent light into parallel light. After collimation, the forward optical signal has a more consistent propagation direction and a more regular beam pattern, allowing it to enter the first polarizing beam splitter 3 more effectively.

[0089] In one alternative implementation, in the forward optical path:

[0090] The first polarizing beam splitter 3 is used to split the forward light signal collimated by the lens 2 into forward P light and forward S light;

[0091] The optical rotator 4 is used to perform a second clockwise rotation on the positive P-beam and the positive S-beam;

[0092] The magneto-optical crystal 7, together with the applied magnetic field, is used to perform a third clockwise rotation on the positive P-beam and positive S-beam after the second clockwise rotation;

[0093] The second polarizing beam splitter 8 is used to re-bend the positive P-beam and the positive S-beam after the third clockwise rotation;

[0094] The biconcave lens 10 is used to expand the combined beam;

[0095] The pinhole aperture 11 is used to limit the quality of the combined beam after beam expansion;

[0096] The plano-convex lens 12 is used to perform secondary collimation on the mass-limited combined beam to form a collimated and magnified outgoing light spot.

[0097] Furthermore, in the forward optical path, the first polarizing beam splitter 3 receives the forward light signal collimated by the lens 2 and, based on the polarization characteristics of the light, splits it into forward P-beams (parallel polarized light) and forward S-beams (perpendicular polarized light). The optical rotator 4 simultaneously performs a second clockwise rotation on the forward P-beams and forward S-beams split from the first polarizing beam splitter 3, changing the polarization direction of the light. This is a crucial step in adjusting the polarization state of the light in the optical path; after rotation, the polarization state of the light changes. The magneto-optical rotator crystal 7, together with the applied magnetic field, performs a third clockwise rotation on the forward P-beams and forward S-beams after the second clockwise rotation by the optical rotator 4. The applied magnetic field provides the necessary magnetic field environment for the magneto-optical rotator crystal 7, enabling it to produce the magneto-optical rotator effect. After these two rotation operations, the polarization states of the forward P-beams and forward S-beams are further changed, ultimately achieving a polarization state interchange. This polarization state interchange is key to the smooth passage of light through subsequent optical elements and the completion of beam combining. The second polarizing beam splitter 8 receives the positive P-beam and positive S-beam, whose polarization states have been interchanged after being processed by the magneto-optical crystal 7 and an external magnetic field, and re-combines these two beams into a single beam. The combined light signal is restored to a unified whole and continues to propagate along the forward optical path. The biconcave lens 10 expands the beam after it has been combined by the second polarizing beam splitter 8, increasing the beam diameter and changing the divergence angle accordingly. The pinhole aperture 11 limits the quality of the combined beam after it has been expanded by the biconcave lens 10, blocking some stray light that does not meet the requirements and allowing only light within a specific range to pass through, thus improving the beam quality and reducing interference factors in the optical path. The plano-convex lens 12, through secondary collimation, readjusts the light after a series of processes back into parallel light and further increases the size of the light spot, forming a collimated and magnified output light spot.

[0098] In one alternative implementation, the counterclockwise rotation angle is the same as the first clockwise rotation angle (exemplarily, the rotation angle is 45°);

[0099] The second clockwise rotation angle is the same as the third clockwise rotation angle (for example, the rotation angle is 45°).

[0100] Furthermore, the magneto-optical rotator crystal 7 and the applied magnetic field cause the reverse P-beam and reverse S-beam to rotate counterclockwise. This counterclockwise rotation angle is the same as the angle at which the optical rotator 4 performs the first clockwise rotation on the counterclockwise rotated reverse P-beam. This allows the polarization state of the reverse P-beam to be restored as much as possible to its initial state (but ultimately, they cannot be combined). Simultaneously, the reverse S-beam is blocked by the groove mechanism, ensuring the stability and regularity of the reverse light isolation and preventing it from interfering with the front-end components. The optical rotator 4 performs a second clockwise rotation on the forward P-beam and forward S-beam, and the magneto-optical rotator crystal 7 and the applied magnetic field perform a third clockwise rotation on the forward P-beam and forward S-beam after the rotation by the optical rotator 4. These two rotation angles are the same. This angular consistency ensures that the polarization state of the forward light changes gradually according to the design, achieving polarization state interchange and successful beam combining, guaranteeing stable forward light transmission and normal operation of the optical isolator.

[0101] In one alternative embodiment, the optical isolator further includes a light-passing aperture 9 located between the second polarizing beam splitter 8 and the biconcave lens 10.

[0102] In the reverse optical path, the light-passing hole 9 is used to reverse the confinement of the returned light spot 13 after the secondary convergence of the biconcave lens 10, and the reverse-confinement returned light spot 13 enters the second polarizing beam splitter 8.

[0103] In the forward optical path, the light-passing aperture 9 is used to confine the combined beam of the second polarizing beam splitter 8 in the forward direction, and the confined combined beam enters the biconcave lens 10.

[0104] Furthermore, in the reverse optical path, the returned light first undergoes secondary focusing through the biconcave lens 10, at which point the state of the light spot changes. The aperture 9 then restricts the returned light spot 13 after secondary focusing, i.e., by filtering through the aperture size of the aperture 9, only light meeting specific conditions is allowed to pass through, while light that does not meet the requirements is blocked. In the forward optical path, the light passes through the second polarizing beam splitter 8 to form a combined beam. The aperture 9 then performs forward restriction on the combined beam, similarly filtering through the aperture size, thereby improving the quality of the combined beam and removing any stray light or undesirable light distributions.

[0105] In one alternative embodiment, the applied magnetic field includes a first magnet 5 and a second magnet 6; the first magnet 5 is located below the magneto-optical crystal 7, and the second magnet 6 is located above the magneto-optical crystal 7.

[0106] The first magnet 5 and the second magnet 6 provide an external magnetic field for the magneto-optical crystal 7, causing the magneto-optical crystal 7 to produce the Faraday effect.

[0107] Furthermore, the first magnet 5 and the second magnet 6 together provide an external magnetic field for the magneto-optical crystal 7. When light passes through the magneto-optical crystal 7 in this magnetic field, a Faraday effect occurs. The Faraday effect refers to the rotation of the polarization plane of light depending on the relationship between the direction of light propagation in the medium and the direction of the magnetic field. In the optical isolator, utilizing this effect, the magneto-optical crystal 7, together with the applied magnetic field, alters the polarization state of light (whether it is forward-biased P- and S-beams or reverse-biased P- and S-beams) according to the design requirements.

[0108] In summary, in the reverse optical path, the reflected light spot 13 of the optical isolator is incident at a limiting angle, converges into a smaller spot by the plano-convex lens 12, and then enters the biconcave lens 10 through the pinhole aperture 11. The spot converges again into a spot close to the output size of the collimator 14, passes through the light aperture 9, and reaches the polarizing beam splitter. At this time, most of the light energy is blocked by the pinhole aperture 11 and the light aperture 9, and a small portion of the light energy is split into reverse S-rays and reverse P-rays by the polarizing beam splitter. Then, the light is reflected by the first magnet 5. Under the action of the second magnet 6 and the magneto-optical crystal 7, the light rotates counterclockwise by 45°. At this time, the reversed s-ray will hit the groove mechanism of the optical rotator 4 (the groove surface of the groove mechanism is a rough surface without anti-reflection coating, and the width can be 0.45mm) and cannot reach the polarizing beam splitter. Meanwhile, the reversed p-ray can pass through the optical rotator 4 after rotating clockwise by 45 degrees, resulting in a total rotation of 0°. Therefore, the polarization state does not change and it also cannot pass through the polarizing beam splitter, thus achieving the isolation effect for the incident light returning at the extreme angle. For details on light transmission without affecting light transmission, please refer to [link to relevant documentation]. Figure 5 The schematic diagram showing the groove depth and width of the groove mechanism illustrates that this embodiment employs a cold-working dicing method to cut a corresponding groove in the middle of the optical rotor 4. The surface of this groove is a rough surface without an anti-reflective coating, completely opaque to light. Its depth can range from 0.1mm to 0.5mm, and its width can be 0.45mm ± 0.05mm. Furthermore, to ensure light transmission, this embodiment adds a small aperture stop 11 behind the biconcave lens 10. The size of this small aperture stop 11 can be 2mm. Figure 5As shown, in this embodiment, a groove (a rough, non-transparent surface) is etched in the middle of the left and right light-transmitting surfaces of the optical rotator 4. Without affecting the normal light transmission path, a wider groove provides greater isolation for reflected light. However, this is limited by the apertures of the first polarizing beam splitter 3 and the magneto-optical crystal 7. Assuming the height of the first polarizing beam splitter 3 is 3mm, the upper and lower light-transmitting apertures are both 1mm, the beam splitting distance is 1.5mm, and the height of the optical rotator 4 is 3mm, the groove width in the middle of the optical rotator 4 cannot exceed 0.5mm. However, to allow for assembly error, it can be set to 0.45mm. For various output-type isolators with different structures, the size of the upper and lower light-transmitting apertures of the first polarizing beam splitter 3 determines the width of the groove in the middle of the optical rotator 4. Please refer to... Figure 6 The schematic diagram of the pinhole aperture 11 shown shows that in this embodiment, a pinhole aperture 11 is added behind the biconcave lens 10, which can block part of the reflected light incident at the extreme angle. This embodiment achieves the effect of isolating the reflected light incident at the extreme angle, which greatly reduces the risk of the reflected light damaging the front-end laser components. The current experimental results show that the dynamic isolation can be improved to between 22dB and 30dB.

[0109] In summary, this embodiment effectively isolates the reflected light signal through the synergistic effect of the plano-convex lens, pinhole aperture, biconcave lens, and second polarizing beam splitter, preventing it from returning to the optical fiber and protecting the front-end laser components. Firstly, the pinhole aperture partially blocks the reflected light spot, and the groove mechanism on the rotator completely blocks the reflected S-beam, further enhancing the isolation effect. This prevents reflected light incident at extreme angles from recoupling back into the optical fiber, achieving the effect of isolating reflected light incident at extreme angles and significantly reducing the risk of damage to the front-end laser components.

[0110] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the defined scope.

Claims

1. An output-type optical isolator, characterized in that, The optical isolator includes: a first polarizing beam splitter, a rotator, a magneto-optical rotator crystal, an external magnetic field, a second polarizing beam splitter, a biconcave lens, a pinhole aperture, and a plano-convex lens arranged sequentially along the forward optical path; the rotator is provided with a non-light-transmitting groove mechanism. In the reverse optical path: The plano-convex lens is used to converge the reflected light spot of the optical isolator once; The pinhole aperture is used to partially block the returning light spot after one convergence. The biconcave lens is used to refocus the reflected light spot after partial obstruction. The second polarizing beam splitter is used to split the returned light spot after secondary focusing into reverse P-beam and reverse S-beam; The magneto-optical crystal, together with the applied magnetic field, is used to rotate the reverse P-beam and the reverse S-beam counterclockwise. The optical rotator is used to perform a first clockwise rotation on the reverse P-beam after counterclockwise rotation, and the groove mechanism on the optical rotator is used to completely block the reverse S-beam after counterclockwise rotation; the reverse P-beam after the first clockwise rotation and the reverse S-beam after complete blocking are isolated outside the first polarizing beam splitter.

2. The optical isolator according to claim 1, characterized in that, The groove mechanism includes a first groove, which is located at the middle position of the right light-transmitting surface of the optical rotor. In the reverse optical path, the first groove is used to completely block the reverse S-beam at the first extreme incident angle after counterclockwise rotation; the reverse P-beam after the first clockwise rotation and the reverse S-beam after the first complete blocking are isolated outside the first polarizing beam splitter.

3. The optical isolator according to claim 2, characterized in that, The groove mechanism further includes a second groove, which is disposed at the middle position of the left light-transmitting surface of the optical rotor; In the reverse optical path, the second groove is used to completely block the reverse S-ray at the second extreme incident angle after counterclockwise rotation; the reverse P-ray after the first clockwise rotation and the reverse S-ray after the second complete blocking are isolated outside the first polarizing beam splitter. The second limiting angle of incidence is greater than the first limiting angle of incidence.

4. The optical isolator according to claim 1, characterized in that, The groove width of the groove mechanism is determined by the upper and lower light-transmitting apertures of the first polarizing beam splitter.

5. The optical isolator according to claim 4, characterized in that, The groove width of the groove mechanism is less than the difference between the light speed splitting distance of the first polarizing beam splitter and the upper and lower light-transmitting apertures.

6. The optical isolator according to claim 1, characterized in that, The optical isolator further includes an optical fiber and a lens; the optical fiber is located at the starting end of the optical isolator; the lens is located between the optical fiber and the first polarizing beam splitter. In the forward optical path: The optical fiber is used to introduce the forward optical signal into the optical isolator; The lens is used to collimate the forward light signal output from the optical fiber once, and the collimated forward light signal enters the first polarizing beam splitter.

7. The optical isolator according to claim 6, characterized in that, In the forward optical path: The first polarizing beam splitter is used to split the forward light signal after it has been collimated by the lens into forward P-beam and forward S-beam; The optical rotator is used to perform a second clockwise rotation on the positive P-beam and the positive S-beam; The magneto-optical crystal, together with the applied magnetic field, is used to perform a third clockwise rotation on the positive P-beam and positive S-beam after the second clockwise rotation; The second polarizing beam splitter is used to re-bend the positive P-beam and the positive S-beam after the third clockwise rotation; The biconcave lens is used to expand the combined beam. The pinhole aperture is used to limit the quality of the combined beam after beam expansion. The plano-convex lens is used to perform secondary collimation on the mass-limited combined beam to form a collimated and magnified outgoing light spot.

8. The optical isolator according to claim 7, characterized in that, The counterclockwise rotation angle is the same as the first clockwise rotation angle; The second clockwise rotation angle is the same as the third clockwise rotation angle.

9. The optical isolator according to claim 7, characterized in that, The optical isolator also includes a light-passing aperture, which is located between the second polarizing beam splitter and the biconcave lens; In the reverse optical path, the light-passing aperture is used to reverse-limit the returned light spot after the secondary convergence of the biconcave lens, and the reverse-limited returned light spot enters the second polarizing beam splitter. In the forward optical path, the light-passing aperture is used to forward confine the combined beam after the second polarizing beam splitter has combined the beams, and the forward-confined combined beams enter the biconcave lens.

10. The optical isolator according to any one of claims 1 to 9, characterized in that, The applied magnetic field includes a first magnet and a second magnet; the first magnet is located below the magneto-optical crystal, and the second magnet is located above the magneto-optical crystal; The first magnet and the second magnet provide an external magnetic field for the magneto-optical crystal, causing the magneto-optical crystal to produce the Faraday effect.

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