Light reflection suppression type optical isolation system and preparation method thereof, optical transmitting device

Abstract

A reflection-suppressing optical isolation system, its fabrication method, and an optical emitting device are disclosed. The optical isolator includes: a light source, a source-side mode selection structure, an angle-selective metasurface grating, a target-side working channel, and a return light processing structure. The source-side mode selection structure constrains the emission mode of the working light. The angle-selective metasurface grating deflects the working light, which meets the incident conditions, to the target diffraction order with high diffraction efficiency and emits it along the target-side working channel. Simultaneously, it couples the return light back to the source port mode of the light source with low efficiency and guides it to the return light processing structure. This invention achieves system-level reflection suppression without magneto-optical materials through diffraction order channel allocation and source port mode constraint. It also covers both normal-incident to oblique-out and oblique-incident to normal-out working paths, making it suitable for optical emitting devices such as laser ranging, Time-of-Flight (ToF), structured light projection, and free-space communication.

Description

Technical Field

[0001] This invention relates to the field of optical isolation technology, and in particular to a reflective suppression optical isolation system based on an angle-selective metasurface grating, its fabrication method, and an optical emitting device. Background Technology

[0002] Optical isolators or backlight suppressors are mainly used to reduce the feedback effects of target reflected light, ambient reflected light, or parasitic reflected light from within the system returning to the light source. For laser ranging, time-of-flight (ToF) ranging, structured light projection, free-space communication, collimated emission, and fiber-coupled emission modules, excessively strong feedback can easily lead to laser operating point drift, increased phase noise, decreased emission stability, and lifespan risks.

[0003] Traditional optical isolators often employ a combination of Faraday rotators, polarizers, and waveplates to achieve non-reciprocal transmission. While this approach is mature, it is typically bulky, involves a large number of components, and relies on magneto-optical materials, hindering ultra-thin designs and modular integration. In transmitter modules that prioritize miniaturization, planarization, and low-cost packaging, traditional magneto-optical isolators have become a bottleneck restricting system integration.

[0004] While existing publicly available solutions include volume Bragg gratings, angle-selective filter films, and asymmetric transmission metasurfaces, these solutions often only describe the selective transmission or reflection behavior at the device level, without integrating source-port mode constraints, angle-selective metasurfaces, and return light guiding paths into a unified system-level design. Although ordinary gratings or metasurfaces can achieve beam deflection, they are difficult to directly translate into a system-level effect of "high-efficiency forward operation and low-coupling return to the source port."

[0005] Research has identified at least the following problems in existing technologies: First, traditional magneto-optical isolators are large in size and have a large number of components, making them difficult to integrate directly into ultra-thin emission modules. Second, while existing ordinary gratings or metasurfaces can achieve deflection, they lack a system-level design that jointly optimizes forward operating efficiency and return suppression effects. Third, when the target return light exhibits angular spectral broadening, wavefront variation, spatial misalignment, or partial polarization variation, existing structures lack targeted system-level feedback suppression methods. Fourth, normal incident and oblique incident operating links are usually designed separately, making it difficult to form a unified protection framework within the same invention.

[0006] In view of this, it is necessary to provide a reflective suppression optical isolation system based on an angle-selective metasurface grating, its fabrication method, and an optical emitting device, in order to solve the above-mentioned technical problems. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a reflective suppression optical isolation system based on an angle-selective metasurface grating, its preparation method, and an optical emitting device.

[0008] To achieve one of the above-mentioned objectives, the present invention adopts the following technical solution.

[0009] In a first aspect, a reflective suppression type optical isolation system is provided, comprising: a light source configured to output working light; a source-side mode selection structure disposed downstream of the light source and configured to constrain the emission mode of the working light to form a forward working light having a set divergence angle, aperture distribution, and spatial mode; and an angle-selective metasurface grating disposed downstream of the source-side mode selection structure, the angle-selective metasurface grating comprising a substrate and a supercell array disposed on the substrate, the supercell array comprising asymmetric supercell structures arranged along at least one periodic direction or quasi-periodic direction; wherein... The asymmetric supercell structure is configured to: deflect the forward working light at a target diffraction angle to the target diffraction order direction, and deflect the reverse return light to a non-source diffraction order channel that deviates from the incident angle domain of the forward working light, the non-source diffraction order channel being spatially offset from the incident angle domain of the forward working light by at least a predetermined angular interval; a target-side working channel, located downstream of the angle-selective metasurface grating, is configured to transmit the working light deflected by the angle-selective metasurface grating to the target surface; and a return light processing structure is configured to receive the return light that has not been recoupled back to the light source.

[0010] In some embodiments, the angle-selective metasurface grating is any one of a transmissive metasurface grating, a reflective metasurface grating, a hybrid transmissive-reflective metasurface grating, or a multi-cascaded metasurface grating.

[0011] In some embodiments, the angle-selective metasurface grating is configured to: receive the forward working light incident at a normal angle, diffract and deflect the forward working light at an oblique diffraction angle and guide it to the target-side working channel, so that it reaches the target surface along the target-side working channel; and receive the return light reflected from the target surface, and deflect the return light to the non-source diffraction order channel.

[0012] In some embodiments, the angle-selective metasurface grating is configured to: receive the forward working light incident at a preset oblique angle, shape the forward working light into a near-normal emission and guide it to the target-side working channel, so that it reaches the target surface along the target-side working channel; and receive the return light reflected by the target surface, and deflect the return light to the non-source diffraction order channel that deviates from the original oblique incident source mode.

[0013] In some embodiments, the diffraction channel relationship of the angle-selective metasurface grating satisfies: ,in The refractive index of the incident medium is... λ is the incident angle, m is the diffraction order, λ is the operating wavelength, and P is the grating period. The refractive index of the exit-side medium. Let be the emission angle. The phase gradient of the angle-selective metasurface grating satisfies: ,in Let λ be the phase gradient along the metasurface plane and λ be the operating wavelength. Let be the refractive index of the medium on the incident side. The refractive index of the medium on the exit side, Angle of incidence The angle of departure is denoted as .

[0014] In some embodiments, the angle-selective metasurface grating includes a first working window and a second working window, the first working window and the second working window respectively corresponding to different target angles or different working wavelengths; the return light processing structure includes a first return light trap disposed in the return angle domain of the first working window and a second return light trap disposed in the return angle domain of the second working window.

[0015] In some embodiments, the angle-selective metasurface grating further includes a polarization-sensitive supercell, which is a supercell structure of complementary geometric units, mirror arrangement, and high symmetry composite, in order to reduce the diffraction efficiency difference between different polarization states in the working angular domain.

[0016] In some embodiments, the non-source diffraction order channel is spatially offset from the source diffraction order channel by at least a preset angular interval, the preset angular interval being larger than the angular aperture range of the light source's exit port, so that the returned light is deflected to a region that does not spatially overlap with the angular region of the exit port.

[0017] In some embodiments, the set operating wavelength is selected from at least one of 850nm, 905nm, 940nm, 1310nm or 1550nm.

[0018] In some embodiments, the source-side mode selection structure includes at least one of a first aperture stop, a single-mode fiber end, a micro-aperture, a collimating lens, a waveguide, or a combination thereof.

[0019] In some embodiments, the return light processing structure includes at least one of an absorption groove, a light-blocking plate, a blackening structure, a non-source diffraction level receiving surface, or a light trap; and / or, the return light processing structure is disposed in front of, behind, beside, or between cascaded structures of the angle-selective metasurface grating.

[0020] Secondly, the present invention also provides a method for manufacturing a reflective suppression type optical isolation system, comprising:

[0021] Determine the divergence angle and aperture of the light source; The period of the angle-selective metasurface grating is calculated based on the target diffraction angle and the working wavelength. Establish a phase-size mapping library for supercells; Based on the phase-size mapping library, the forward working efficiency and return suppression ratio are jointly optimized to determine the structural parameters of the supercell, so that the non-source diffraction order subchannels are spatially offset from the source diffraction order subchannels. The angle-selective metasurface grating is fabricated based on the structural parameters; A return light processing structure is set at the location of the non-source diffraction order secondary channel.

[0022] In some embodiments, the diffraction channel relationship of the angle-selective metasurface grating satisfies: ,in The refractive index of the incident medium is... λ is the incident angle, m is the diffraction order, λ is the operating wavelength, and P is the grating period. The refractive index of the exit-side medium. The angle of departure is denoted as .

[0023] The phase gradient of the angle-selective metasurface grating satisfies: ,in Let λ be the phase gradient along the metasurface plane and λ be the operating wavelength. Let be the refractive index of the medium on the incident side. The refractive index of the medium on the exit side, Angle of incidence The angle of departure is denoted as .

[0024] Thirdly, the present invention also provides an optical transmitting device, including the aforementioned reflective suppression type optical isolation system, wherein the optical transmitting device is one of a laser ranging transmitting module, a time-of-flight transmitting module, a structured light projection module, a free-space communication transmitting module, or an optical fiber coupled transmitting module.

[0025] One of the above technical solutions has the following advantages or beneficial effects: The reflective suppression type optical isolation system of the present invention is a system architecture designed in collaboration with a source-side mode selection structure, an angle-selective metasurface grating, a target-side working channel, and a return light processing structure. The source-side mode selection structure constrains the emission mode of the working light, and the angle-selective metasurface grating deflects the working light that meets the incident conditions to the target diffraction order with high diffraction efficiency and emits it along the target-side working channel. At the same time, it couples the return light back to the source port mode of the light source with low efficiency and guides it to the return light processing structure.

[0026] This invention enables the forward working light to efficiently enter the target working channel, while the return light, due to angle mismatch and mode mismatch, is guided by the angle-selective metasurface grating to the non-source diffraction order sub-channel and is absorbed or dissipated. This overcomes the limitations of traditional magneto-optical isolators being large in size and existing metasurface schemes lacking system-level feedback suppression design. In this way, it achieves the function of backlight suppression without magneto-optical materials, suitable for planar integration, and simultaneously covering both normal and oblique incidence working links. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall framework of a reflective suppression type optical isolation system according to one embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of two optional module types in one embodiment of the present invention, wherein (a) corresponds to a single-chip transmissive module and (b) corresponds to a dual-cascaded enhancement module.

[0029] Figure 3 This is a comparative schematic diagram of a conventional Faraday isolator (a), a common deflection grating (b), and the reflective suppression optical isolation system (c) of the present invention.

[0030] Figure 4 The diagram shows the principle of two working links in this invention, where (a) corresponds to the working link from normal incidence to oblique emission, and (b) corresponds to the working link from oblique incidence to normal emission.

[0031] Figure 5 This is a schematic diagram of the channel allocation of different diffraction orders in the system in this invention, where the working order (+1 order), zero order (0 order), and trap order (-1 order, trap) correspond to different response-wavelength trends.

[0032] Figure 6 This is a schematic diagram of the phase-feature size relationship of the metasurface structure family in this invention.

[0033] Figure 7 This is an angle-selective response curve diagram in the present invention, showing the response differences between the normal and oblique incidence schemes near the incident and return angles. "Forward, normal" represents normal incidence, "Forward, oblique" represents oblique incidence, "Back-coupling, normal" represents normal return coupling, and "Back-coupling, oblique" represents oblique return coupling.

[0034] Figure 8This is a tolerance and robustness curve in the present invention, showing the curve of reflection suppression efficiency as a function of process deviation under ideal conditions (Reference), thickness deviation (Thinkness error), size deviation (CD error), or refractive index deviation (Index error).

[0035] Figure 9 This is a schematic diagram of the metasurface structure in this invention.

[0036] Figure 10 This is a schematic diagram of the supercell arrangement from a top-down view of the present invention.

[0037] Figure 11 This is a schematic diagram of the matching between the transverse coordinate at the source plane and the normalized field amplitude in this invention. The source acceptance mode represents the source-end acceptable mode, Returned mode A represents return mode A, and Returned mode B represents return mode B.

[0038] Figure 12 This is a schematic diagram of the oblique incidence to normal exit structure of Embodiment 2 of the present invention.

[0039] Figure 13 This is a schematic diagram of the response curves of the dual work windows and dual back-coupling windows extended structure in different angular domains according to Embodiment 4 of the present invention.

[0040] Figure 14 This is a schematic diagram of the polarization-sensitive supercell structure of Embodiment 5 of the present invention. (a) corresponds to the working link from normal incident to oblique outgoing, and (b) corresponds to the working link from oblique incident to normal outgoing.

[0041] The reference numerals in the attached figures are explained as follows: 1-light source, 2-source-side mode selection structure, 3-angle-selective metasurface grating, 31-first working window, 32-second aperture stop, 33-second working window, 34-substrate, 35-micro / nano structure, 36-supercell, 4-target-side working channel, 5-target surface, 6-return optical path, 7-non-source diffraction order channel, 8-return optical processing structure. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0043] In the various figures of this invention, for ease of illustration, some dimensions of structures or parts may be exaggerated relative to other structures or parts; therefore, only the basic structure of the subject matter of this invention is used to illustrate the invention.

[0044] For ease of description, the terms "upstream," "downstream," "forward," "positive," "return," and "reverse" are defined relative to the direction of light propagation. The direction from the light source towards the target surface is considered positive, and the direction returning from the target surface is considered reverse. Light propagates from upstream to downstream along the propagation direction.

[0045] Please refer to Figures 1 to 14 As shown, the present invention provides a reflection suppression type optical isolation system, which defines the reflection suppression target from the system-level optical path.

[0046] The overall structure of the anti-reflection type optical isolation system includes at least a light source 1, a source-side mode selection structure 2, an angle-selective metasurface grating 3, a target-side working channel 4, a target surface 5, and a return light processing structure 8.

[0047] Please refer to Figure 1 , Figure 12 As shown, the working light output from light source 1, after being constrained by the source-side mode selection structure 2, reaches the angle-selective metasurface grating 3 under the set incident conditions. After being deflected by the angle-selective metasurface grating 3, it exits along the target-side working channel 4 to the target surface 5. The return light from the target surface 5 acts on the angle-selective metasurface grating 3 again along the return light path 4. Due to the difference in its angle and mode compared to the forward working light, it is guided into the non-source diffraction order channel 7 and finally falls into the return light processing structure 8.

[0048] After the returned light is deflected to the non-source diffraction order channel 7, it is then guided or absorbed by the returned light processing structure 8. This prevents the returned light from coupling back to the source 1 along its original path, effectively preventing frequency drift, power fluctuations, and even device damage caused by the returned light. This is especially important for light sources such as lasers that are sensitive to returned light.

[0049] The light source 1 can be one of the following: semiconductor laser, narrow linewidth laser, vertical-cavity surface-emitting laser (VCSEL), edge-emitting laser (EEL), fiber laser, or light-emitting diode (LED).

[0050] The operating wavelength of light source 1 can cover multiple emission bands, including at least 850nm, 905nm, 940nm, 1310nm or 1550nm, to adapt to different application scenarios such as laser ranging, ToF, structured light and optical communication.

[0051] The source-side mode selection structure 2 is located downstream of the light source 1. The source-side mode selection structure 2 is configured to constrain the emission mode of the working light, so that it forms a forward working light with a set divergence angle, aperture distribution and spatial mode, and the forward working light is incident on the angle-selective metasurface grating 3.

[0052] By pre-constraining the output mode, divergence angle, and aperture distribution of the light source 1 through the source-side mode selection structure 2, it can filter stray light and edge-scattered light from the light source, eliminate spatial noise of the original beam, and significantly improve the beam quality and spatial consistency of the forward working light. This ensures that the forward working light can efficiently match the incident conditions of the angle-selective metasurface grating 3, avoiding problems such as decreased diffraction efficiency and deflection angle shift caused by beam mode disorder. On the other hand, it also defines the receiving mode of the source port, making it difficult for the returned light to be efficiently recoupled into the light source 1.

[0053] Specifically, the source-side mode selection structure 2 may include at least one of a first aperture stop, a single-mode fiber end, a micro-aperture, a collimating lens, a waveguide (e.g., a waveguide transmitting end), or a combination thereof.

[0054] An angle-selective metasurface grating 3 is disposed downstream of the source-side mode selection structure 2. The angle-selective metasurface grating 3 includes a substrate 34 and micro / nano structures 35 disposed on the substrate 34. The micro / nano structures 35 are arranged periodically or quasi-periodically in the form of a supercell array 36.

[0055] The substrate can be any of silicon, silicon dioxide, or glass.

[0056] The micro / nanostructure 35 can be a nanopillar, nanofin, or other subwavelength structure. The design process of the micro / nanostructure 35 can be guided by establishing a supercell phase-size mapping library, which correlates the geometric parameters of the micro / nanostructure (such as the diameter, height, and spacing of the nanopillars) with their introduced phase delay. Based on the target diffraction angle and diffraction channel relationship, a supercell arrangement scheme that meets the phase gradient requirements can be selected from the supercell phase-size mapping library.

[0057] The supercell array 36 includes an asymmetric supercell structure arranged along at least one periodic or quasi-periodic direction. The asymmetric supercell structure is configured to: deflect the forward working light at a target diffraction angle to a target diffraction order direction, and deflect the reverse return light to a non-source diffraction order channel 7 that deviates from the incident angle domain of the forward working light, the non-source diffraction order channel 7 being spatially offset from the incident angle domain of the forward working light by at least a predetermined angular interval.

[0058] This scheme uses angle-selective metasurface grating 3 for angle-selective diffraction to achieve spatial optical path separation. The forward light is efficiently deflected to the target order, while the return light is guided to the non-source order direction, which fundamentally avoids absorption loss in the forward optical path and can achieve lower insertion loss while maintaining high isolation.

[0059] The preset angle interval is set according to the actual application scenario, generally not less than 5°, preferably not less than 10°, and in implementations with higher requirements for reflective isolation, it can be not less than 15°.

[0060] At the set operating wavelength, the angle-selective metasurface grating 3 deflects the operating light that meets the incident conditions to the target diffraction order with a target diffraction efficiency higher than the first preset threshold, so that the operating light exits along the target-side operating channel 4. At the same time, the angle-selective metasurface grating 3 couples the return light back to the source port mode of the light source 1 with an efficiency lower than the second preset threshold.

[0061] It is understood that the specific values ​​of the first preset threshold and the second preset threshold can be set according to the application scenario. For example, the first preset threshold can be set to 80% (preferably 90% or 95%) or higher, and the second preset threshold can be set to 10% (preferably 8% or 5%) or lower.

[0062] The angle-selective metasurface grating 3 utilizes its selective response to the incident angle to achieve differentiated processing between the forward working light and the return light. After being constrained by the source-side mode selection structure 2, the incident angle and spectral broadening of the forward working light are precisely controlled within the high-efficiency working window of the angle-selective metasurface grating 3, thus enabling it to be deflected to the target diffraction order with high diffraction efficiency. After being reflected or scattered by the target surface 5, the return light propagates in the opposite direction, and its incident angle and spectral distribution have deviated from the set conditions of the forward working light. Therefore, it cannot efficiently match the target diffraction order of the angle-selective metasurface grating 3 again, and most of the return light is allocated to the zeroth order or other non-source diffraction orders and guided to the return light processing structure 8.

[0063] It should be noted that the angular spectral broadening or wavefront change of the returned light may originate from scattering by the target surface 5, the tilt of the target surface 5, system assembly errors, aberrations during propagation, or source-port mode selection constraints, etc., and does not require the target surface 5 to be a rough, non-smooth surface. Even if the target surface 5 is a high-quality reflector, as long as the returned state experiences a mismatch in angle, wavefront, azimuth, or mode relative to the forward operating state when it reaches the angle-selective metasurface grating 3 and the light source 1 again, the system can still achieve backlight suppression.

[0064] The diffraction channel relationship of angle-selective metasurface grating 3 satisfies: ,in The refractive index of the incident medium is... λ is the incident angle, m is the diffraction order, λ is the operating wavelength, and P is the grating period. The refractive index of the exit-side medium. The angle of departure is denoted as .

[0065] This formula is used to back-calculate the required grating period P and diffraction channel m from the target working angle, and is the basic optical geometry relationship for designing the angle-selective metasurface grating 3.

[0066] The phase gradient of angle-selective metasurface grating 3 satisfies: ,in Let λ be the phase gradient along the metasurface plane and λ be the operating wavelength. Let be the refractive index of the medium on the incident side. The refractive index of the medium on the exit side, Angle of incidence The angle of departure is denoted as .

[0067] This formula converts the target emission angle into the phase gradient distribution required by the metasurface, providing a basis for the selection and arrangement of supercells.

[0068] Reflection rejection ratio (IR) is a core indicator for evaluating the performance of the reflective-suppressing optical isolation system of this invention. The reflection rejection ratio (IR) is defined as: ,in Forward operating optical power, This represents the effective feedback optical power returned to light source 1. A higher IR value indicates stronger backlight suppression capability.

[0069] In one embodiment, the angle-selective metasurface grating 3 is configured to maintain a backlight suppression ratio (IR) of not less than a third preset threshold within a preset manufacturing tolerance range. The backlight suppression ratio (IR) can be set to a target value according to the application scenario; in some embodiments, it is preferably not less than 10 dB, and in more preferred embodiments, it can reach more than 15 dB. The embodiment in this case achieves a backlight suppression ratio of approximately 18 dB at a working wavelength of 940 nm. Manufacturing tolerances include at least one of the following: thickness deviation, unit size deviation, refractive index deviation, or periodicity deviation of the metasurface structure layer. For example... Figure 8 As shown, by incorporating manufacturing tolerances into the optimization model during the design phase, it can be ensured that the present invention can maintain relatively stable backlight suppression performance within the processing accuracy range of standard CMOS compatible processes, and the backlight suppression performance of the device remains at an acceptable level.

[0070] By coordinating the design of the source-side mode selection structure 2, the angle-selective metasurface grating 3, and the return light processing structure 8, joint optimization can be achieved between forward working efficiency and return light suppression ratio.

[0071] The angle-selective metasurface grating 3 can be any one of a transmissive metasurface grating, a reflective metasurface grating, a transmissive-reflective hybrid metasurface grating, or a multi-cascaded metasurface grating.

[0072] Normal incidence and oblique incidence working links can correspond to different embodiments or different installation and usage scenarios. In this case, it is not required that the same metasurface simultaneously complete both types of links under the same working state. Of course, in scalable implementations, compatibility with both types of working links can also be achieved through area reuse or multifunctional metasurface design.

[0073] In one embodiment, the angle-selective metasurface grating 3 is configured to receive forward working light incident at a normal angle, diffract and deflect the forward working light at an oblique diffraction angle and guide it to the target-side working channel 4, so that it reaches the target surface 5 along the target-side working channel 4; and to receive the return light reflected by the target surface 5, deflect the return light to the non-source diffraction order channel 7, and finally intercept it by the return light processing structure 8.

[0074] The angle-selective metasurface grating 3 is configured to operate in a working link from normal incident to oblique exit. In this link, the working light is incident on the angle-selective metasurface grating 3 at a near-normal angle, deflected by the target diffraction order, and then exits along the oblique working channel to the target surface. This working link is suitable for scenarios requiring lateral emission, such as lidar and ToF.

[0075] In another embodiment, a forward working light incident at a preset oblique angle is received, the forward working light is shaped into a near-normal emission and guided to the target-side working channel 4, so that it reaches the target surface 5 along the target-side working channel 4; and a return light reflected from the target surface 5 is received, the return light is deflected to a non-source diffraction order channel 7 that deviates from the original oblique incident source mode, and finally intercepted by the return light processing structure 8.

[0076] The angle-selective metasurface grating 3 is configured to operate in a working link from oblique incidence to normal emission. In this link, the working light is incident on the angle-selective metasurface grating 3 at a preset oblique angle, shaped, and then emitted along a near-normal working channel to the target surface 5. This working link is suitable for scenarios requiring frontal emission.

[0077] It should be noted that both working links can be implemented under the same core optical architecture.

[0078] In one embodiment, the angle-selective metasurface grating 3 includes a first working window 31 and a second working window 33. A second aperture stop 32 may also be disposed between the first working window 31 and the second working window 33.

[0079] The first working window 31 and the second working window 33 correspond to different target angles or different working wavelengths, respectively. Accordingly, the return light processing structure 8 includes a first return light trap and a second return light trap, which correspond to the return angle domains of the first working window 31 and the second working window 33, respectively.

[0080] The dual working window and dual reflection trap structure expands the present invention from a single working window to a multi-channel platform, which can simultaneously adapt to two types of forward working modes and configure dedicated reflection traps for the two types of return corner domains, further improving the system-level reflection suppression capability.

[0081] Understandably, the dual-window structure can be further extended into a multi-window structure, corresponding to multiple target angles or multiple light source ports.

[0082] In one embodiment, the angle-selective metasurface grating 3 further includes a polarization-sensitive supercell. By introducing a polarization-sensitive supercell, the reflection suppression performance can be made robust to changes in the polarization state of the incident light without increasing the system complexity. This is of great significance for practical applications where the polarization state may change with time, temperature, or mechanical stress.

[0083] The polarization-sensitive supercell is a supercell structure with complementary geometric units, mirror arrangement, and high symmetry, designed to reduce the difference in diffraction efficiency between different polarization states within the working angular domain.

[0084] Polarization-sensitive supercells are configured to reduce the difference in diffraction efficiency between different polarization states within the working angular domain. Specifically, polarization sensitivity can be reduced through complementary rectangular pillar pairs, orthogonally arranged symmetrical units, or highly symmetrical composite supercell structures.

[0085] In one embodiment, the non-source diffraction order channel 7 is spatially offset from the source diffraction order channel by at least a predetermined angular interval. The predetermined angular interval is larger than the angular aperture range of the light source's exit port, causing the returned light to be deflected to a region that does not spatially overlap with the exit port's angular domain.

[0086] The returned light is deflected to a spatial region that does not overlap with the light output angle of light source 1, thus cutting off the path of the returned light coupling into the resonant cavity of light source 1 from a physical spatial level. Even if the energy of the returned light is not absorbed, it cannot return to light source 1 due to directional mismatch, which is infinitely close to the true meaning of zero backcoupling and full-dimensional reflection suppression.

[0087] The target-side working channel 4 is a directional transmission unit that can perform constrained transmission of the forward working light after it has been precisely deflected by the angle-selective metasurface grating 3. This effectively isolates stray light and air-scattered light from entering the optical path, preventing external optical noise from interfering with the working accuracy of the target surface 5. At the same time, it can fix the transmission path of the forward working light, correct minor beam deviations, and ensure that the working light is accurately and stably projected onto the target surface 5, thus guaranteeing the accuracy of optical detection, processing, and sensing operations.

[0088] The return light processing structure 8 is configured to receive return light that has not been recoupled back to the light source 1. The return light processing structure 8 can eliminate residual return light inside the system, preventing it from re-entering the optical path due to secondary reflection and multiple scattering; it can also prevent light energy from accumulating inside the system, preventing optical path devices from aging, performance degradation, and local overheating due to long-term exposure to stray light.

[0089] The return light processing structure 8 may include at least one of an absorption groove, a light-blocking plate, a blackening structure (e.g., a blackening structure surface), a non-source diffraction level receiving surface, or an optical trap (e.g., a multi-stage optical trap).

[0090] The return light processing structure 8 can be positioned in front of, behind, on the side of, or between multiple cascaded structures of the angle-selective metasurface grating 3, depending on the specific optical path layout. By guiding the return light energy to a dissipation region far from the light source 1, it is possible to effectively prevent the return light from re-entering the receiving cone angle of the light source 1 after multiple reflections or scatterings.

[0091] This invention also provides a method for manufacturing a reflective suppression type optical isolation system, comprising: S1 determining the divergence angle and light-emitting aperture (or source aperture) of the light source 1; S2 calculating the period of the angle-selective metasurface grating 3 based on the target diffraction angle and the working wavelength; S3 establishing a phase-size mapping library for the supercell; S4 determining the structural parameters of the supercell by jointly optimizing the forward working efficiency and the return suppression ratio based on the phase-size mapping library, such that the non-source diffraction order channel 7 is spatially angularly offset from the source diffraction order channel; S5 fabricating the angle-selective metasurface grating based on the structural parameters; and S6 setting a return light processing structure at the location of the non-source diffraction order channel 7.

[0092] Step S1 collects the core native parameters of the light source 1, such as the divergence angle and the aperture of the light outlet, and uses them as design inputs to ensure that the design of the angle-selective metasurface grating 3 is precisely matched with the characteristics of the light source 1.

[0093] Step S2 quantitatively calculates the grating period using the target diffraction angle and operating wavelength, thus achieving the formulaic and quantitative design of core optical parameters. This accurately matches the system's preset forward optical path diffraction deflection requirements and reverse return angle separation requirements, ensuring that the angle-selective metasurface grating 3 has optimal diffraction efficiency and angle selectivity at the target operating wavelength. This effectively avoids optical path distortion and isolation performance degradation caused by wavelength shift and angle deviation, improving the optical stability and operational adaptability of the device in the rated operating band.

[0094] Step S3 establishes a mapping database between supercell phase and structural size. Compared with the traditional single-style supercell iterative trial and error design, this process can quickly retrieve the unit structure size that matches the target phase requirement, which can significantly shorten the device simulation and design iteration cycle and reduce the R&D design cost.

[0095] Step S4 employs a dual-objective optimization strategy targeting both forward operating efficiency and return rejection ratio. This overcomes the limitations of traditional optical device designs that prioritize transmission efficiency at the expense of isolation performance, or excessively enhance isolation while sacrificing forward light energy. By iteratively optimizing parameters to select the optimal supercell structure parameters, the system maximizes the suppression and isolation capability of the reverse return light while ensuring high forward operating light transmission efficiency and high beam fidelity. This achieves the optimal balance between transmission and isolation performance, significantly improving the overall optical performance of the product.

[0096] Steps S5 and S6 employ an angle-selective metasurface grating 3 fabrication process and a fixed-point integration process for the return light processing structure 8. The return light processing structure 8 is precisely positioned according to the fixed optical path position of the non-source diffraction order, achieving precise alignment between the return light offset path and the return light processing structure 8.

[0097] The diffraction channel relationship and phase gradient of the angle-selective metasurface grating satisfy the above description and will not be repeated here.

[0098] The manufacturing method of the reflective suppression type optical isolation system of the present invention can be used to prepare any of the above-mentioned reflective suppression type optical isolation systems, and can also be used to prepare other similar reflective suppression type optical isolation systems.

[0099] The present invention also provides an optical emitting device, including any of the above-described reflective suppression type optical isolation systems.

[0100] The optical transmitting device is one of the following: laser ranging transmitting module, time-of-flight transmitting module, structured light projection module, free-space communication transmitting module, or fiber optic coupling transmitting module.

[0101] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0102] Example 1: A reflective light-suppressing optical isolation system with normal incident light to oblique exit light.

[0103] Please refer to Figure 1 The light source 1 is a VCSEL operating at a wavelength of 940nm. The source-side mode selection structure 2 includes a collimating lens, which collimates the diverging beam output from the light source 1 into a near-parallel beam. The forward working beam constrained by the collimating lens is incident on the angle-selective metasurface grating 3 at a near-normal angle.

[0104] The angle-selective metasurface grating 3 is a transmission-type metasurface grating, constructed from a silicon nanopillar array arranged in a rectangular lattice on a silicon dioxide substrate. The grating period P is designed using the diffraction channel relationship formula, such that the deflection angle of the target diffraction order (m=+1 order) of the working light is approximately 30 degrees. In the forward path, the working light is deflected to the m=+1 order with a diffraction efficiency higher than 85%, and exits along the working channel 4 obliquely towards the target side to the target surface 5. The returned light comes from reflection or scattering from the target surface 5, and its angle, angular spectrum, or wavefront may deviate from the original forward working state due to the state of the target surface, perturbation of the propagation path, or system assembly deviation. As a result, most of the returned light is distributed by the angle-selective metasurface grating 3 to the zero order (m=0 order) or other non-target diffraction orders, and is guided to the returned light processing structure 8 located on the side of the angle-selective metasurface grating 3.

[0105] The backlight suppression ratio (IR) of this embodiment reaches approximately 18 dB at a working wavelength of 940 nm. This value is used to illustrate the backlight suppression effect of this embodiment at a specific working wavelength.

[0106] Example 2: A reflective light-suppressing optical isolation system with oblique incidence to normal emission.

[0107] Please refer to Figure 12 Light source 1 at a preset angle An angle-selective metasurface grating 3 is incident at approximately 30 degrees. The source-side mode selection structure 2 includes a collimating lens. The angle-selective metasurface grating 3 is designed such that, under 30-degree oblique incidence, the working light is efficiently deflected (diffraction efficiency >80%) to the m=-1 order, which corresponds to near-normal emission. The light (approximately 0 to 3 degrees) exits along the normal target-side working channel 4. After being reflected by the target surface 5, the returning light propagates in the opposite direction. Due to the reflection characteristics of the target surface 5 and the beam diffusion during free-space propagation, the incident angle of the returning light when it reaches the angle-selective metasurface grating 3 again has deviated by 30 degrees, and the angular distribution of the returning light no longer matches the source port receiving mode defined by the source-side mode selection structure 2. Therefore, the returning light cannot efficiently recover the original obliquely incident source mode and is dissipated by the returning light processing structure 8.

[0108] Example 3: Design and Implementation Process.

[0109] Please refer to Figure 11This embodiment provides an executable design and implementation path. The process includes the following steps: First, determine the divergence angle and aperture parameters of the light source 1 as design inputs for the source-side mode selection structure 2. Second, determine the target angle and operating wavelength based on the application scenario, using the diffraction channel relationship formula: The first step is to calculate the required grating period P and diffraction order m. The second step is to establish a supercell phase-size mapping library and obtain the phase delay introduced by nanopillar units with different geometric parameters (such as nanopillar diameter, height, and spacing) through electromagnetic simulation. The third step is to apply the phase gradient formula... The required phase gradient distribution is determined, and a supercell arrangement scheme that meets the phase gradient requirements is selected from the supercell phase-size mapping library. The forward working efficiency and backlight suppression ratio are jointly optimized. In the fifth step, based on the selected supercell arrangement scheme and optical path layout, the position and size of the return light processing structure 8 are set, and the aperture position of the source-side mode selection structure 2 is determined. In the sixth step, the normal incident working link and the oblique incident working link are verified respectively to confirm that both links meet the backlight suppression ratio requirements.

[0110] Example 4: Extended structure with dual working windows and dual reflective traps.

[0111] Please refer to Figure 13 This embodiment extends the angle-selective metasurface grating 3 into a dual-window structure based on Embodiment 1. The first working window 31 corresponds to the working path (working wavelength 940nm) from normal incident to oblique exit at 30 degrees, and the second working window 33 corresponds to the working path (working wavelength 905nm) from normal incident to oblique exit at 45 degrees. The supercell arrangement of the angle-selective metasurface grating 3 is designed in zones, with the first region corresponding to the phase gradient of the first working window 31 and the second region corresponding to the phase gradient of the second working window 33.

[0112] Accordingly, the return light processing structure 8 includes a first return light trap and a second return light trap. The first return light trap is set at a position corresponding to the return corner domain of the first working window 31, and the second return light trap is set at a position corresponding to the return corner domain of the second working window 33.

[0113] With the corresponding design of dual working windows and dual reflective traps, this embodiment can simultaneously adapt to two types of forward working modes, significantly expanding the application range of the device.

[0114] Example 5: Polarization-sensitive supercell.

[0115] Please refer to Figure 14In this embodiment, a polarization-sensitive supercell is used as the micro / nano structure of the angle-selective metasurface grating 3. The micro / nano structure reduces the efficiency difference between x and y polarizations in the working angular domain and enhances engineering tolerance through complementary geometric units, mirror arrangement, and highly symmetric composite supercells.

[0116] Due to the geometric symmetry in both directions, the phase delay difference experienced by TE-polarized and TM-polarized incident light in this supercell is significantly reduced. Within the operating angular domain, the difference in diffraction efficiency between TE-polarized and TM-polarized light is controlled within 5%, thus making the backlight suppression performance highly robust to changes in the polarization state of the incident light. This embodiment is suitable for applications where the polarization state may change with environmental conditions, such as outdoor lidar and free-space optical communication.

[0117] The angle-selective metasurface gratings 3 in the above embodiments can be fabricated using standard CMOS-compatible micro / nano fabrication processes. A typical fabrication process includes: depositing a metasurface material layer (such as amorphous silicon, polycrystalline silicon, or silicon nitride) on a substrate (such as a silicon wafer or glass substrate); defining a nanostructure pattern using electron beam lithography or deep ultraviolet lithography; transferring the pattern to the metasurface material layer using inductively coupled plasma reactive ion etching (ICP-RIE) to form a subwavelength micro / nano structure; and optionally depositing a protective layer or an anti-reflection layer. The first aperture stop and micro-stop in the source-side mode selection structure 2 can be formed using a precision metal mask or a blackening coating. The return light processing structure 8 can be formed using a physical vapor deposition (PVD) blackening coating or a mechanically machined absorption trench.

[0118] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium. When the program is executed, it includes the steps of the above method embodiments. The storage medium can be selected from any one of read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0119] In the above embodiments, Embodiment 1 verifies the basic principle and performance of backlight suppression achieved through angle-selective metasurface gratings and source-side mode selection structures in the normal-incident to oblique-out working link; Embodiment 2 verifies the feasibility of the oblique-incident to normal-out working link, proving that the present invention can cover two working links under the same core architecture; Embodiment 3 provides a complete design and implementation path from light source parameters to supercell selection and then to dual-link verification; Embodiment 4 verifies the effectiveness of the dual working window and dual backlight trap extension structure, proving that the present invention can be extended from a single working window to a multi-channel platform; Embodiment 5 verifies the improvement effect of polarization-sensitive supercell on the robustness of backlight suppression at the microstructure level.

[0120] When the source-side mode selection structure 2 is not set in the system and the deflection is only performed by the angle-selective metasurface grating 3 itself, the mismatch constraint between the returned light and the receiving mode of the source port is weakened, and the return light suppression ratio will decrease significantly; the specific decrease varies with the source port aperture, the state of the target surface 5 and the working angle.

[0121] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0122] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A reflective suppression type optical isolation system, characterized in that, include: The light source is configured to output working light; A source-side mode selection structure is located downstream of the light source and is configured to constrain the emission mode of the working light, so that it forms a forward working light with a set divergence angle, aperture distribution and spatial mode. An angle-selective metasurface grating is disposed downstream of the source-side mode selection structure. The angle-selective metasurface grating includes a substrate and a supercell array disposed on the substrate. The supercell array includes asymmetric supercell structures arranged along at least one periodic direction or quasi-periodic direction. The asymmetric supercell structures are configured to: deflect forward working light at a target diffraction angle to a target diffraction order direction, and deflect backward returning light to a non-source diffraction order channel that deviates from the incident angle domain of the forward working light. The non-source diffraction order channel is spatially angularly offset from the incident angle domain of the forward working light by at least a predetermined angular interval. A target-side working channel, located downstream of the angle-selective metasurface grating, is configured to transmit working light, deflected by the angle-selective metasurface grating, to the target surface; and The return light processing structure is configured to receive return light that is not recoupled back to the light source.

2. The reflective suppression type optical isolation system according to claim 1, characterized in that, The angle-selective metasurface grating is any one of the following: a transmissive metasurface grating, a reflective metasurface grating, a hybrid transmissive-reflective metasurface grating, or a multi-cascaded metasurface grating.

3. The reflective suppression type optical isolation system according to claim 1, characterized in that, The angle-selective metasurface grating is configured to: receive the forward working light incident at a normal angle, diffract and deflect the forward working light at an oblique diffraction angle and guide it to the target-side working channel, so that it reaches the target surface along the target-side working channel; And receive the reflected light from the target surface, and deflect the reflected light to the non-source diffraction order channel.

4. The reflective suppression type optical isolation system according to claim 1, characterized in that, The angle-selective metasurface grating is configured to: receive the forward working light incident at a preset oblique angle, shape the forward working light into a near-normal emission and guide it to the target-side working channel, so that it reaches the target surface along the target-side working channel; And receive the reflected light from the target surface, and deflect the reflected light to the non-source diffraction order channel that deviates from the original oblique incidence source mode.

5. The reflective suppression type optical isolation system according to claim 1, characterized in that, The diffraction channel relationship of the angle-selective metasurface grating satisfies: ,in The refractive index of the incident medium is... λ is the incident angle, m is the diffraction order, λ is the operating wavelength, and P is the grating period. The refractive index of the exit-side medium. The angle of departure; The phase gradient of the angle-selective metasurface grating satisfies: ,in Let λ be the phase gradient along the metasurface plane and λ be the operating wavelength. Let be the refractive index of the medium on the incident side. The refractive index of the medium on the exit side, Angle of incidence The angle of departure.

6. The reflective suppression type optical isolation system according to claim 1, characterized in that, The angle-selective metasurface grating includes a first working window and a second working window, which correspond to different target angles or different working wavelengths, respectively; the return light processing structure includes a first return light trap disposed in the return angle domain of the first working window and a second return light trap disposed in the return angle domain of the second working window.

7. The reflective suppression type optical isolation system according to claim 1, characterized in that, The angle-selective metasurface grating also includes a polarization-sensitive supercell, which is a supercell structure of complementary geometric units, mirror arrangement, and high symmetry composite, in order to reduce the diffraction efficiency difference between different polarization states in the working angular domain.

8. The reflective suppression type optical isolation system according to claim 1, characterized in that, The non-source diffraction order channel is spatially offset from the source diffraction order channel by at least a preset angular interval, the preset angular interval being larger than the angular aperture range of the light source's output port, so that the returned light is deflected to a region that does not overlap with the angular region of the output port in space.

9. The reflective suppression type optical isolation system according to claim 1, characterized in that, The set operating wavelength is selected from at least one of 850nm, 905nm, 940nm, 1310nm or 1550nm.

10. The reflective suppression type optical isolation system according to claim 1, characterized in that, The source-side mode selection structure includes at least one of a first aperture stop, a single-mode fiber end, a micro-aperture, a collimating lens, a waveguide, or a combination thereof.

11. The reflective suppression type optical isolation system according to claim 1, characterized in that, The returned light processing structure includes at least one of an absorption groove, a light-blocking plate, a blackening structure, a non-source diffraction level receiving surface, or an optical trap; And / or, the return light processing structure is disposed in front of, behind, beside, or between cascaded structures of the angle-selective metasurface grating.

12. A method for manufacturing a reflective suppression type optical isolation system, characterized in that, include: Determine the divergence angle and aperture of the light source; The period of the angle-selective metasurface grating is calculated based on the target diffraction angle and the working wavelength. Establish a phase-size mapping library for supercells; Based on the phase-size mapping library, the forward working efficiency and return suppression ratio are jointly optimized to determine the structural parameters of the supercell, so that the non-source diffraction order subchannels are spatially offset from the source diffraction order subchannels. The angle-selective metasurface grating is fabricated based on the structural parameters; A return light processing structure is set at the location of the non-source diffraction order secondary channel.

13. The method according to claim 12, characterized in that, The diffraction channel relationship of the angle-selective metasurface grating satisfies: ,in The refractive index of the incident medium is... λ is the incident angle, m is the diffraction order, λ is the operating wavelength, and P is the grating period. The refractive index of the exit-side medium. The angle of departure; The phase gradient of the angle-selective metasurface grating satisfies: ,in Let λ be the phase gradient along the metasurface plane and λ be the operating wavelength. Let be the refractive index of the medium on the incident side. The refractive index of the medium on the exit side, Angle of incidence The angle of departure.

14. An optical emitting device, characterized in that, The system includes any one of the reflective suppression type optical isolation systems according to claims 1 to 11, wherein the optical transmitting device is one of a laser ranging transmitting module, a time-of-flight transmitting module, a structured light projection module, a free-space communication transmitting module, or an optical fiber coupling transmitting module.

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