Waveguide structure for laser speckle suppression, laser display device and speckle suppression method

Abstract

The invention relates to the technical field of laser display, in particular to a laser speckle suppression waveguide structure, a laser display device and a speckle suppression method. The laser speckle suppression waveguide structure comprises a substrate layer, a lower cladding, a waveguide core area and an upper cladding which are stacked from bottom to top. Wherein the waveguide core region comprises an input section, an arc turning section and an output section; the arc turning section is used for combining laser beams from different input sections and outputting the combined laser beams from different output sections in parallel; the waveguide structure is also provided with a waveguide phase disturbance part used for destroying laser transmission coherence and / or an electrically tunable phase modulation part used for destroying laser dynamic coherence. The invention provides a waveguide structure for laser speckle suppression, a laser display device and a speckle suppression method, and aims to solve the problems that a speckle suppression scheme in the prior art is poor in suppression effect, large in system size, low in integration level, high in optical loss and incapable of dynamically adapting to different display scenes.

Description

Technical Field

[0001] This invention relates to the field of laser display technology, and in particular to waveguide structures for laser speckle suppression, laser display devices, and speckle suppression methods. Background Technology

[0002] Laser displays, with their wide color gamut, high brightness, and long lifespan, are considered the next-generation technology to replace existing display solutions. However, the inherent high coherence of lasers, when illuminating diffuse reflective surfaces, produces random interference, forming a pattern of random bright and dark spots known as "speckle." This physical effect severely reduces image sharpness and uniformity, leading to visual fatigue, and has become a key technical obstacle that must be overcome for laser display technology to achieve large-scale market adoption.

[0003] To suppress speckle, existing technologies mainly fall into two categories: mechanical and optical approaches, but both have limitations. Mechanical methods disrupt coherence through physical motion, such as rotating frosted glass, vibrating optical fibers, or using MEMS micromirrors. These solutions generally result in complex system structures, large sizes, and problems such as low reliability, easy wear, and potential noise and vibration caused by moving parts. Furthermore, the mechanical devices themselves introduce significant additional optical losses. Optical methods attempt to address the light field itself, primarily including polarization combining and wavelength combining. Polarization combining relies on the incoherent superposition of lasers with different polarization states, but its polarization control flexibility is insufficient, often requiring discrete waveplates, polarization beam splitters, and other optical components, leading to low system integration, complex assembly and adjustment, and high costs. Wavelength combining uses multiple lasers with different wavelengths, utilizing wavelength differences to disrupt temporal coherence. However, existing solutions face challenges in precise control of wavelength spacing, low-loss beam combining of multiple wavelengths, and miniaturized integration, making it difficult to achieve efficient speckle suppression within the cost constraints of consumer products.

[0004] In summary, existing technologies struggle to achieve a balance across multiple key performance dimensions, including speckle suppression, system size and integration, manufacturing cost, optical loss, and dynamic adaptability to different display scenarios. They cannot simultaneously meet the dual demands of high-performance image quality, extreme miniaturization, and high reliability for consumer-grade laser display products. Therefore, the industry urgently needs an innovative technological solution that can fundamentally overcome the limitations of existing approaches and solve this multi-objective optimization challenge through a new system architecture. Summary of the Invention

[0005] The purpose of this invention is to provide a waveguide structure, a laser display device, and a speckle suppression method for laser speckle suppression, in order to solve the problems of poor suppression effect, large system size, low integration, high optical loss, and inability to dynamically adapt to different display scenarios in existing speckle suppression schemes.

[0006] The technical solution of this invention is: a waveguide structure for laser speckle suppression, comprising: The substrate, lower cladding, waveguide core region, and upper cladding are stacked from bottom to top. The waveguide core region includes an input segment, an arc-shaped turning segment, and an output segment. The arc-shaped turning segment is used to combine laser beams from different input segments and output them in parallel from different output segments. The waveguide structure is further provided with a waveguide phase perturbation section for disrupting laser transmission coherence and / or an electrically tunable phase modulation section for disrupting laser dynamic coherence.

[0007] Preferably, the waveguide phase disturbance section is located between the arc turning section and the output section, and is a periodic groove structure fabricated on the surface of the waveguide core region.

[0008] Preferably, the periodic groove structure is configured to generate a phase difference within ±π / 4 for light beams of different wavelengths and polarization states transmitted through it, thereby achieving waveguide phase perturbation.

[0009] Preferably, the electrically tunable phase modulation section is a resistive electrode fabricated above the output section.

[0010] Preferably, the input segment has a tapered transition structure, the width of its input front end is greater than the width of its output rear end, and the tapered angle formed by the inclination of its sidewall is 5° to 10°.

[0011] A laser display device, comprising: The waveguide structure for laser speckle suppression; Multiple semiconductor lasers, whose output beams are respectively coupled to different input segments; The control unit is signal-connected to the electrically tunable phase modulation unit.

[0012] Preferably, the plurality of said semiconductor lasers are configured to output at least two primary colors for display, and the number of said semiconductor lasers for outputting the same primary color is at least two, and the center wavelengths of said semiconductor lasers are different.

[0013] Preferably, the semiconductor lasers used to output the same primary color light are configured such that the interval between each pair of adjacent center wavelengths is capable of disrupting the temporal coherence of the primary color light.

[0014] Preferably, the semiconductor laser is configured to output beams with different polarization states.

[0015] A laser speckle suppression method includes the following steps: S1. Provide multiple semiconductor lasers with different center wavelengths, corresponding to output at least two primary colors of light, and the number of said semiconductor lasers used to output the same primary color of light is at least two, and the center wavelengths are different; S2. Control the polarization state of the beam output by the semiconductor laser so that the beam entering the subsequent optical path has multiple polarization states; S3. Couple the laser beam emitted by the semiconductor laser into a waveguide structure, the waveguide structure including an input section, a circular arc turning section and an output section; S4. Apply a preset waveguide phase perturbation to the beam using the waveguide phase perturbation part disposed on the waveguide structure; S5. The phase of the output beam is dynamically modulated using an electrically tunable phase modulation unit integrated on the output section; By leveraging the synergistic effects of the diversity of wavelength and polarization state of semiconductor lasers, waveguide phase perturbation, and electrically tunable phase modulation, the temporal coherence, spatial coherence, transmission coherence, and dynamic coherence of the laser are disrupted, thereby achieving speckle suppression.

[0016] Preferably, the loss of the waveguide structure is less than 0.1 dB / cm, and the loss of the semiconductor laser directly coupled to the waveguide structure is less than 0.5 dB.

[0017] Preferably, when the laser speckle suppression method is applied in an ambient temperature range of -40℃ to 85℃, the speckle contrast fluctuation does not exceed ±0.5%.

[0018] Preferably, the diversity of wavelength and polarization state of semiconductor laser, waveguide phase perturbation, and electrically tunable phase modulation work together to suppress the speckle contrast of the emitted laser to below 5%.

[0019] Compared with the prior art, the advantages of the present invention are: (1) By combining the effects of multiple wavelengths, multiple polarization states, waveguide phase perturbation, and electrically tunable phase modulation, the temporal coherence, spatial coherence, transmission coherence, and dynamic coherence of the laser are disrupted. This combined effect can stably suppress the speckle contrast of the output laser to below 5%.

[0020] (2) Based on silicon-based waveguide integration technology, the multi-input section, output waveguide core area, circular arc turning section, waveguide phase disturbance part (periodic groove) and electrically tunable phase modulation part (resistive electrode) are integrated on the waveguide core area. No mechanical moving parts are required, the structure is compact and the reliability is high.

[0021] (3) The transmission loss of the waveguide structure is less than 0.1 dB / cm, the direct coupling loss between the semiconductor laser and the waveguide structure is less than 0.5 dB, and the overall loss from the laser to the beam combiner output is less than 1 dB. The low-loss design provides a sufficient power basis for the synergistic effect, ensuring the power requirements of the high-brightness laser display.

[0022] (4) The control unit adjusts the signal output to the electrically adjustable phase modulation unit according to the feedback information of the display scene (such as brightness and color changes) to achieve real-time and dynamic phase modulation. This mechanism can compensate for the coherence fluctuation caused by scene changes, keep the speckle suppression effect stable in the ambient temperature range of -40℃ to 85℃ (speckle contrast fluctuation does not exceed ±0.5%), and can be adapted to display scenes with different brightness and resolution, from micro-projection to laser TV. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of a waveguide core region structure according to the present invention; Figure 2 This is a cross-sectional view of the waveguide structure of the present invention; Figure 3 This is a schematic diagram showing the connection between the input segment, the arc turning segment, and the output segment of the present invention; Figure 4 A schematic diagram of a semiconductor laser with different polarization outputs for this invention; Figure 5 This is a schematic diagram of the polarization controller used in this invention; Figure 6 This is a schematic diagram of the electrode orientation of the present invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments: This embodiment provides a waveguide structure for laser speckle suppression, a laser display device, and a speckle suppression method. The laser display device includes a waveguide structure for laser speckle suppression, multiple semiconductor lasers, and a control unit.

[0025] like Figure 2 As shown, the waveguide structure for laser speckle suppression will be described in detail below. The waveguide structure consists of a substrate layer, a lower cladding layer, a waveguide core region, and an upper cladding layer stacked sequentially from bottom to top. The upper cladding layer covers the waveguide core region and wraps around its sidewalls.

[0026] like Figure 1 As shown, the waveguide core region includes the input segment ( Figure 1 Horizontal sections at different entrances), and circular turning sections ( Figure 1 (Middle turning section) and output section ( Figure 1 The vertical segments are arranged in parallel. The arc-shaped turning segments are used to combine laser beams from different input segments and output them in parallel from different output segments. The spacing between each pair of adjacent parallel output segments is configured to avoid crosstalk between adjacent channels, and the parallel output waveguides provide the basis for the miniaturized integration of electrically tunable phase modulation and waveguide structures.

[0027] In this embodiment, the angle of the arc turning segment is 90°. The interval between two adjacent parallel output segments is 10-30μm, which is sufficient to avoid optical crosstalk between adjacent channels, and the arrangement order of the lasers of each color in the output segment can be flexibly arranged according to the display requirements.

[0028] The input section has a tapered transition structure, with the width of the input front end being greater than the width of the output rear end, and the cone angle formed by the inclination of its sidewalls being 5° to 10°. This controls the increase in coupling loss caused by the dimensional tolerance of the external semiconductor laser to within 0.1dB, and the overall loss from the semiconductor laser output to the input section is less than 1dB, thereby ensuring high utilization of laser power.

[0029] The waveguide structure is further provided with a waveguide phase perturbation part for disrupting the laser transmission coherence (i.e., the coherence characteristics of the beam maintained by mode consistency during waveguide transmission) and / or an electrically modulated phase modulation part for disrupting the laser dynamic coherence (i.e., the time coherence of the beam).

[0030] The waveguide phase disturbance section is located between the arc-shaped bend and the output section. It is a periodic groove structure fabricated on the surface of the waveguide core. The dimensions of the periodic groove structure are configured to generate a phase difference within ±π / 4 for beams of different wavelengths and polarization states passing through it, thus achieving waveguide phase disturbance and disrupting the propagation coherence of the laser. In this embodiment, to achieve optimal speckle suppression, the groove depth is controlled to generate a phase shift of approximately ±π / 4 for beams of different wavelengths. Specifically, as... Figure 3 As shown, the periodic groove has a period of 2±0.5μm, a depth of 50-100nm, and a width of 4±1μm.

[0031] To avoid color shift caused by excessive phase shift differences between different wavelengths, the groove depth is set to 80-100 nm for short wavelengths to ensure a phase shift close to π / 4; for long wavelengths, the groove depth is set to 50-70 nm to ensure a phase shift close to π / 4. For example, for 450 nm blue light, a groove depth of 80 nm can produce a π / 4 phase shift; for 625 nm red light, a groove depth of 60 nm can produce a π / 4 phase shift. The fabrication process for the periodic grooves is selected from one or more combinations of electron beam lithography, nanoimprint lithography, and reactive ion etching.

[0032] The electrically tunable phase modulation section consists of resistive electrodes fabricated above the output section, used to modulate the phase delay of each waveguide by applying electricity. For example... Figure 6 As shown, in this embodiment, each output segment corresponds to an independent electrode. This resistive electrode is fabricated using metal (such as Cr / Au) deposition and photolithography processes, with a driving voltage range of 0.2-1.5V and a phase modulation response time less than or equal to 10ms. After power-on, the phase delay of the waveguide is dynamically changed primarily through the thermo-optic effect (the current generates heat, changing the waveguide's refractive index). Its preset "voltage-phase calibration curve" is as follows: When powered on at 0.2-0.5V, the phase delay is ±π / 6, which is suitable for the small coherent fluctuations in "static scenes (such as image display)". With a power-on voltage of 0.5-1.0V, the phase delay is ±π / 4, which is suitable for moderate coherent fluctuations in dynamic scenarios (such as video playback). With a power-on voltage of 1.0-1.5V, the phase delay is ±π / 3, which is suitable for severe coherent fluctuations in "high-brightness scenarios (such as outdoor projection)".

[0033] The core function of this electrically tunable phase modulation unit is to perform scene-specific dynamic collaborative compensation. For example, in dynamic display scenarios (such as movie playback), when the screen brightness switches from a dark field to a bright field, the increased power of multi-wavelength lasers may lead to residual coherence recovery (increased speckle contrast). At this time, the electrically tunable system automatically increases the applied voltage, increasing the phase delay to ±π / 4, which can bring the contrast back to below 5% within 10ms. Simultaneously, this modulation can also compensate for the "uneven light intensity caused by the increased power of multi-polarized beams." In high-brightness outdoor projection scenarios, the laser power increases to the hundreds of milliwatts level, and the "wavelength drift" of multiple wavelengths may weaken the phase perturbation effect. In this case, the electrically tunable electrodes apply a higher voltage, increasing the phase delay to ±π / 3, while simultaneously adjusting the phase difference of different color waveguides. This compensates for the effect of wavelength drift and optimizes the color mixing uniformity of the RGB three colors, achieving a dual synergy of speckle suppression and color optimization. The electrically tunable phase modulation can also be implemented using electro-optic or acousto-optic effects.

[0034] Fabrication of waveguide structures: A1. Substrate and Cladding Fabrication: High-resistivity silicon wafers were selected as the substrate. The lower cladding, waveguide core region, and upper cladding were fabricated using chemical vapor deposition (CVD) technology. The material was silicon dioxide.

[0035] A2. Waveguide Patterning: Using photolithography (such as deep ultraviolet lithography), a waveguide pattern including an input segment, a circular bend segment, and an output segment is defined on the waveguide core area coated with photoresist. Then, reactive ion etching (RIE) technology is used to transfer the pattern onto the waveguide core area, forming an etched area consisting of an input segment, a circular bend segment, and an output segment.

[0036] A3. Waveguide phase perturbation section fabrication: A periodic groove structure is fabricated between the arc turning section and the output section using a process of electron beam lithography combined with reactive ion etching.

[0037] A4. Fabrication of electrically tunable phase modulation section (resistor electrode): The resistor electrode is fabricated above the output section using photolithography and metal deposition processes.

[0038] The following section provides a detailed description of the various semiconductor lasers and control units of the laser display device. For example... Figure 1 As shown in the figure, LD1-LD10 represent semiconductor lasers (LDs) of different wavelengths. The output beams of different semiconductor lasers are coupled to different input segments of the waveguide structure. To achieve low speckle and high image quality display, the laser display device in this embodiment suppresses laser coherence in both time and space dimensions.

[0039] Decreased temporal coherence: Each semiconductor laser is configured to output at least two primary colors for display, and at least two semiconductor lasers are used to output the same primary color, with different center wavelengths. The output power of the selected semiconductor lasers ranges from tens of milliwatts to hundreds of milliwatts, a power range sufficient to meet the needs of display applications with varying brightness, from micro-projection to laser television.

[0040] Multiple semiconductor lasers outputting the same primary color light are configured with a spacing between each pair of adjacent center wavelengths that effectively disrupts the temporal coherence of that primary color light. By setting the center wavelength spacing of adjacent lasers to 3-5 nm, a significant optical path difference can be introduced into a silicon-based silica waveguide (refractive index ≈ 1.45). This results in the interference period of different wavelength components being shortened to the micrometer level. At the output end, bright and dark spots of adjacent wavelengths overlap, failing to form a stable speckle pattern, thus effectively reducing temporal coherence and initially suppressing speckle formation. This 3-5 nm wavelength spacing range was determined through theoretical calculations and experimental optimization based on the effective refractive index (≈ 1.45) of the silicon-based waveguide to ensure that the introduced optical path difference is sufficient to overcome the threshold for disrupting temporal coherence.

[0041] Reduction in spatial coherence: To further disrupt the spatial coherence of the laser, semiconductor lasers are configured to output beams with different polarization states. For example... Figure 4 and 5 As shown, the polarization state is controlled by using a polarization controller or selecting semiconductor lasers with different polarization outputs (e.g., TE / TM / 45° linear polarization). This results in beams entering the waveguide structure having different polarization states, forming orthogonally polarized or non-linearly polarized light at the output, thus utilizing polarization diversity to disrupt spatial coherence.

[0042] For selected multi-wavelength lasers, polarization states are allocated according to the principle of "orthogonal polarization as the primary mode and non-linear polarization as the secondary mode." If the laser's own polarization is fixed (typically TE mode), a miniature polarization controller (volume < 1 mm³, compatible with waveguide integration) is selected to ensure that part of the laser beam can be converted to TM mode before coupling, avoiding insufficient spatial coherence destruction caused by single polarization. When orthogonally polarized (TE / TM) beams propagate in the waveguide, their electric field vibration directions are perpendicular due to the orthogonal polarization states, preventing interference. "45° linear polarization" is applied to some wavelengths to form a three-dimensional polarization distribution with TE / TM polarization, avoiding the uniformity of polarization distribution caused by only orthogonal polarization and making spatial coherence destruction more thorough.

[0043] Experiments show that using only a single wavelength (e.g., 620nm) with polarization modulation results in a speckle contrast higher than 20% because temporal coherence is not disrupted. However, this solution, through a dual mechanism of "multi-wavelength + multi-polarization," synergistically disrupts both temporal and spatial coherence, improving speckle suppression by more than 30%.

[0044] In this embodiment, to achieve full-color display, three primary colors—red (R), green (G), and blue (B)—are configured. For each primary color, at least two semiconductor lasers with different center wavelengths are configured, with lasers of the same color differing in wavelength by 3-5 nm to disrupt the temporal coherence of that primary color. Experimental verification shows that when the wavelength difference is <3 nm, the disruption of temporal coherence is insufficient, and the speckle contrast is still relatively large (≥8%); when the wavelength difference is >5 nm, the color gamut deviation is large (ΔE > 1.5), which does not meet display standards.

[0045] In this embodiment, the full-color display configuration is as follows: Red channel: Equipped with two semiconductor lasers with center wavelengths of 620nm and 623nm respectively.

[0046] Green channel: Configure two semiconductor lasers with center wavelengths of 523nm and 525nm respectively.

[0047] Blue channel: Configured with two semiconductor lasers with center wavelengths of 450nm and 453nm respectively.

[0048] The 620nm red and 523nm green lasers are semiconductor lasers that output TE mode; the 623nm red and 450nm blue lasers are devices that output TM mode; while the 525nm green and 453nm blue lasers integrate a miniature polarization controller at the output end to adjust their polarization state to 45° linear polarization. This results in a mixed polarization state distribution of TE, TM, and 45° linear polarization.

[0049] The output beam (which has only undergone multi-wavelength and multi-polarization processing, without waveguide phase disturbance and electrically tunable phase modulation) is connected to the display module and detected by a speckle measurement system (based on CCD camera shooting and grayscale analysis) to ensure that the speckle contrast is reduced to 12%-15%, proving that the basic synergistic effect of "multi-wavelength + multi-polarization" of this solution is effective.

[0050] To construct a complete laser display device, the semiconductor laser needs to be coupled and packaged with the waveguide structure. To ensure sufficient beam power for subsequent collaborative processing, the coupling loss must be controlled to be less than 0.5dB. The specific process is as follows: B1. Waveguide preprocessing and alignment reference establishment: The input section of the waveguide structure is polished at the end face (roughness < 5nm) to reduce Fresnel reflection and scattering loss. Subsequently, alignment marks are made on the waveguide by photolithography to clarify the coupling channels of multi-wavelength beams (e.g., pre-define the red laser to correspond to waveguide channels 1-3, green to correspond to 4-6, and blue to correspond to 7-9).

[0051] B2. High-precision active alignment: Using a high-precision six-axis alignment platform (positioning accuracy ±0.1μm), the multi-wavelength semiconductor laser array is actively aligned with the waveguide channel one-to-one with the photolithographic marks on the waveguide as a reference. This ensures that the center of each laser beam and the center of the corresponding waveguide core area are deviated by less than 0.5μm, so as to avoid additional losses caused by mode mismatch.

[0052] B3. Coupling and coordination of multi-polarization beams: Different coupling strategies are adopted for lasers with different polarization states: For TE mode lasers (such as 620nm red light), they are directly coupled to the TE mode transmission channel of the waveguide; For TM mode lasers (such as 623nm red light), a "mode converter" integrated into the input section (structure as follows) is used. Figure 5 As shown, an adaptation is performed to avoid coupling loss greater than 1dB due to polarization mode mismatch with waveguide.

[0053] B4. Real-time Monitoring and Optimization: During the coupling process, an optical power meter is installed at the output end to monitor the output power of each channel in real time. By fine-tuning the position and angle of the laser, it is ensured that the coupling loss of each channel is less than 0.5dB, and the total coupling efficiency of the "multi-wavelength + multi-polarization" beam is greater than 90%, thereby reserving sufficient power for subsequent waveguide phase perturbation and electrically tunable phase modulation.

[0054] The laser display device in this embodiment also includes a control unit (such as a microcontroller MCU or FPGA) which is signal-connected to the electrically tunable phase modulation unit (i.e., the resistive electrode).

[0055] The core function of the control unit is to apply a specific driving voltage to each resistive electrode based on external signals (such as brightness and color signals from the projector's main control system), thereby achieving dynamic modulation of the output beam phase.

[0056] A laser speckle suppression method, employing the aforementioned laser speckle suppression device, specifically includes the following steps: S1. Provide multiple semiconductor lasers with different center wavelengths, corresponding to output at least two primary colors of light, and the number of semiconductor lasers used to output the same primary color of light is at least two, and the center wavelengths are different; wherein, the center wavelength interval is configured to be 3-5nm to destroy the temporal coherence of the laser.

[0057] S2. Control the polarization state of the beam output from the semiconductor laser so that the beam entering the subsequent optical path has multiple polarization states; specifically, make the beam entering the waveguide structure contain at least two of TE, TM and 45° linear polarization to destroy the spatial coherence of the laser.

[0058] S3. The laser beam emitted by the semiconductor laser is coupled into a waveguide structure, which includes an input section, a circular arc turning section, and an output section; after the beam is combined through the circular arc turning section, it is output by multiple parallel output sections.

[0059] S4. Apply a preset waveguide phase disturbance to the beam using a waveguide phase disturbance part disposed on the waveguide structure; the waveguide phase disturbance part is a periodic groove structure fabricated on the surface of the waveguide core region, the size of which is configured to cause different phase shifts in beams of different wavelengths, so as to destroy the transmission coherence of the laser.

[0060] S5. The phase of the output beam is dynamically modulated using an electrically tunable phase modulation unit integrated on the output section; the dynamic modulation is adjusted in real time according to the external signal to destroy the dynamic coherence of the laser.

[0061] By leveraging the synergistic effects of the diversity of wavelength and polarization state of semiconductor lasers, waveguide phase perturbation, and electrically tunable phase modulation, the temporal coherence, spatial coherence, transmission coherence, and dynamic coherence of the laser are disrupted, thereby achieving speckle suppression.

[0062] The waveguide structure loss is less than 0.1 dB / cm, and the loss from direct coupling between the semiconductor laser and the waveguide structure is less than 0.5 dB. A laser speckle suppression method, when applied in an ambient temperature range of -40℃ to 85℃, exhibits speckle contrast fluctuations of no more than ±0.5%. Through the synergistic effect of the diversity of wavelength and polarization state of the semiconductor laser, waveguide phase perturbation, and electrically tunable phase modulation, the speckle contrast of the emitted laser is suppressed to below 5%.

[0063] To quantify and dynamically control the synergistic suppression effect of speckle, a correlation equation between speckle contrast C and parameters of each dimension was established:

[0064] in: The speckle contrast is for a single wavelength and a single polarization (>30%). The center wavelength spacing of the semiconductor laser is 3-5 nm. P represents the number of polarization states (2-3); The amplitude of the waveguide phase perturbation (±π / 4). The phase delay for electrically tunable phase modulation is (±π / 6 - ±π / 3). K1-K4 are the synergy coefficients (calibrated experimentally to be 0.05-0.1; the specific calibration experimental procedure for the synergy coefficients K1-K4 is to measure the contrast change by changing a single variable and then fit the coefficients).

[0065] This approach addresses the technical challenges of laser speckle one by one through a hierarchical and collaborative approach: Firstly, there is the fundamental synergy, which uses the different center wavelengths of semiconductor lasers to disrupt temporal coherence and combines the diversity of polarization states to disrupt spatial coherence. This bidirectional complementary approach addresses the problems of static speckle and poor large-area uniformity, reducing the initial speckle contrast from over 30% to below 10-15%, thus laying the foundation for subsequent enhancement and suppression.

[0066] Secondly, the amplification synergy is achieved by introducing differentiated phase shifts using the periodic grooves of the waveguide phase perturbation section, which solves the residual coherence problem that still exists after the basic synergy and further reduces the speckle contrast to below 10%. This step amplifies the effect of the basic synergy.

[0067] Furthermore, dynamic coordination involves adjusting the phase delay in real time through an electrically tunable phase modulation unit to resolve dynamic coherence fluctuations caused by changes in the display scene, ensuring that speckle contrast remains stable below 5%. At the same time, this modulation can also compensate for color shift and uneven light intensity, achieving a dual synergy of "suppressing speckle" and "optimizing image quality".

[0068] Finally, there is the synergistic support of structure. The low-loss silicon-based silicon dioxide waveguide structure provides a high-power signal foundation for all-dimensional technical solutions, solving the problems of volume, cost and loss caused by the superposition of multiple functions, and forming a synergistic support of "structure-function".

[0069] To achieve optimal synergy, iterative optimization of four-dimensional parameters can be employed. For example, first, the center wavelength spacing and polarization state parameters of the semiconductor laser are fixed, and the size of the periodic groove is optimized to reduce the speckle contrast to 8%. Then, based on this result, the driving voltage-phase delay curve of the electrically tunable phase modulation unit is optimized, ultimately reducing the speckle contrast to below 5%. This step provides a clear engineering basis for customizing module parameters in different application scenarios.

[0070] Furthermore, for specific display application scenarios, this solution achieves deeper performance optimization by adjusting the collaboration strategy: (1) High-brightness synergistic mode (e.g., outdoor projection): When the laser power is increased to the level of several hundred milliwatts, the basic suppression effect of multiple wavelengths and multiple polarizations will be slightly reduced due to the power increase, resulting in a speckle contrast that may rise to 8%. At this time, two aspects of synergistic optimization are used: by adjusting the polarization state combination to a hybrid mode of "orthogonal + non-linear polarization", the ability to destroy spatial coherence is further enhanced; by applying a higher voltage of 1-1.5V through electrical phase modulation, the phase perturbation amplitude is further increased. The synergistic effect of the two can reduce the speckle contrast back to 4-5%, while the low-loss design of the waveguide ensures that the high-brightness output is not significantly attenuated.

[0071] (2) Low-resolution adaptation mode (e.g., automotive display): To adapt to small-sized display panels, the wavelength arrangement of the output waveguide is adjusted to a compact arrangement of "red-green-blue-red-green-blue". At this time, the basic synergy of multiple wavelengths and multiple polarizations ensures basic speckle suppression under small size; the micro phase difference introduced by waveguide phase perturbation effectively compensates for optical crosstalk that may be caused by the compact arrangement; finally, fine-tuning is performed by electronic phase adjustment (0.2-0.3V) to optimize the image quality uniformity at the display edge. The three work together to achieve the comprehensive effect of "miniaturization-low speckle-high uniformity".

[0072] Actual tests show that, through the above-mentioned synergistic regulation, this method can stably reduce the speckle contrast to below 5% in various display scenarios, and the overall waveguide loss is <1dB, fully meeting the stringent power and image quality requirements of high-brightness laser displays.

[0073] To ultimately apply the aforementioned synergistic effects to display products, this solution provides a specific process for adapting and implementing product-specific synergistic models: C1. Laser beam combining and module access: Multi-wavelength, multi-polarization lasers, after being electrically modulated, are output from multiple parallel output segments of a waveguide structure and directly connected to the optical engine of a display module (such as a DMD chip or LCD panel).

[0074] The arrangement order of the lasers in the output section can be flexibly adjusted: for example, micro projectors need to be arranged compactly, using the order of "red-green-blue-red-green-blue"; laser TVs need low crosstalk, using the order of "red-red-green-green-blue-blue" to ensure that there is no channel crosstalk after output (crosstalk < 0.1%).

[0075] C2. Product-based collaborative model adaptation: (1) Miniature projector (volume < 20cm³): Prioritize "miniaturization + low power consumption", adopt a collaborative mode of "multi-wavelength (2 colors) + orthogonal polarization + fixed phase perturbation (groove depth 70nm) + low voltage electronic control (0.2-0.5V)", speckle contrast < 5% and power consumption < 5W.

[0076] (2) Laser TV (brightness > 3000 lumens): Prioritize "high brightness + low loss", adopt the collaborative mode of "multi-wavelength (3 / color) + TE / TM / 45° polarization mixing + deep groove (100nm) + medium voltage electric adjustment (0.5-1.0V)", with overall loss < 1dB and brightness utilization rate > 90%.

[0077] (3) Vehicle display (low temperature -40℃ to high temperature 85℃): Prioritize "environmental adaptability" and adopt a collaborative mode of "multi-wavelength (2 colors) + temperature-resistant polarization controller + shallow groove (50nm) + wide voltage adjustment (0.3-1.2V)" to maintain speckle contrast <5% even under extreme temperatures.

[0078] C3. Final Result Acceptance: Display product standard testing: speckle contrast ≤5% (industry-leading level), light loss ≤1dB, color gamut coverage (DCI-P3) ≥95%, no performance degradation after 1000 hours of continuous operation, confirming that the final effect of the four-dimensional collaboration meets product requirements.

[0079] Based on the above-mentioned speckle suppression capability, the device and method of this embodiment further integrate multiple functions to improve the overall performance of the system: (1) Color and brightness optimization function: By electrically modulating the phase delay of each waveguide, the phase difference of red, green and blue can be adjusted to make the color gamut coverage (DCI-P3) ≥95% and the brightness uniformity ≥90%.

[0080] (2) Wavelength drift adaptive compensation function: If the wavelength of the semiconductor laser drifts (e.g. ±1nm) after long-term operation, the phase delay is adjusted by the electrically tunable phase modulation unit (e.g., additional compensation ±π / 8) to counteract the effect of wavelength drift on coherence and ensure that the speckle contrast is still ≤5%.

[0081] (3) Linkage calibration function between groove size and electrically tunable phase: For example, when the periodic groove depth of the waveguide phase disturbance part is too shallow (e.g., designed 80nm but actually 70nm), the problem of insufficient phase disturbance can be compensated by increasing the driving voltage applied to the electrically tunable phase modulation part by 0.1-0.2V.

[0082] (4) Fault tolerance mechanism for polarization state control: If the polarization controller is not accurate enough (e.g., polarization state deviation ±5°), the phase is finely adjusted (±π / 12) by the electrically tunable phase modulation unit to compensate for the insufficient destruction of spatial coherence caused by the incomplete orthogonality of polarization states.

[0083] The laser speckle suppression scheme of this invention is based on the deep synergy of four key technologies, rather than a simple linear superposition. Specifically: multi-wavelength and multi-polarization technology constructs a two-dimensional coherence disruption mechanism ("time + space"), solving the core problem of incomplete suppression in a single dimension; waveguide phase perturbation technology amplifies and suppresses the residual coherence characteristics of the beam after disruption, solving the problem of insufficient basic suppression effect; electrically tunable phase modulation technology compensates for coherence fluctuations caused by changes in the display scene in real time, solving the problem that waveguide phase perturbation schemes cannot adapt to complex application scenarios; and the low-loss silicon-based waveguide structure provides high-power support for the entire process of all the above technologies, solving the fundamental problem of synergistic failure due to insufficient power. Through this hierarchical and interlocking synergistic mechanism, this scheme not only achieves a significant gain in speckle suppression effect, but also takes into account the miniaturization, low cost, and high adaptability to different application scenarios.

[0084] The above embodiments are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and thus all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

Claims

1. A waveguide structure for laser speckle suppression, characterized in that, include: The substrate, lower cladding, waveguide core region, and upper cladding are stacked from bottom to top. The waveguide core region includes an input segment, an arc-shaped turning segment, and an output segment. The arc-shaped turning segment is used to combine laser beams from different input segments and output them in parallel from different output segments. The waveguide structure is further provided with a waveguide phase perturbation section for disrupting laser transmission coherence and / or an electrically tunable phase modulation section for disrupting laser dynamic coherence.

2. The waveguide structure for laser speckle suppression according to claim 1, characterized in that: The waveguide phase disturbance section is located between the arc turning section and the output section, and is a periodic groove structure fabricated on the surface of the waveguide core region.

3. The waveguide structure for laser speckle suppression according to claim 2, characterized in that: The periodic groove structure is configured to generate a phase difference within ±π / 4 range for light beams of different wavelengths and polarization states transmitted through it, thereby achieving waveguide phase perturbation.

4. The waveguide structure for laser speckle suppression according to claim 1, characterized in that: The electrically tunable phase modulation section is a resistive electrode fabricated above the output section.

5. The waveguide structure for laser speckle suppression according to claim 1, characterized in that: The input section has a tapered transition structure, with the width of the input front end being greater than the width of the output rear end, and the tapered angle formed by the inclination of its sidewalls being 5° to 10°.

6. A laser display device, characterized in that, include: A waveguide structure for laser speckle suppression as described in any one of claims 1 to 5; Multiple semiconductor lasers, whose output beams are respectively coupled to different input segments; The control unit is signal-connected to the electrically tunable phase modulation unit.

7. A laser display device according to claim 6, characterized in that: The plurality of said semiconductor lasers are configured to output at least two primary colors for display, and the number of said semiconductor lasers for outputting the same primary color is at least two, and the center wavelengths of said semiconductor lasers are different.

8. A laser display device according to claim 7, characterized in that: The semiconductor lasers, which are used to output the same primary color light, are configured such that the interval between each pair of adjacent center wavelengths is capable of destroying the temporal coherence of the primary color light.

9. A laser display device according to claim 8, characterized in that: The semiconductor laser is configured to output beams with different polarization states.

10. A method for suppressing laser speckle, characterized in that, Includes the following steps: S1. Provide multiple semiconductor lasers with different center wavelengths, corresponding to output at least two primary colors of light, and the number of said semiconductor lasers used to output the same primary color of light is at least two, and the center wavelengths are different; S2. Control the polarization state of the beam output by the semiconductor laser so that the beam entering the subsequent optical path has multiple polarization states; S3. Couple the laser beam emitted by the semiconductor laser into a waveguide structure, the waveguide structure including an input section, a circular arc turning section and an output section; S4. Apply a preset waveguide phase perturbation to the beam using the waveguide phase perturbation part disposed on the waveguide structure; S5. The phase of the output beam is dynamically modulated using an electrically tunable phase modulation unit integrated on the output section; By leveraging the synergistic effects of the diversity of wavelength and polarization state of semiconductor lasers, waveguide phase perturbation, and electrically tunable phase modulation, the temporal coherence, spatial coherence, transmission coherence, and dynamic coherence of the laser are disrupted, thereby achieving speckle suppression.

11. A laser speckle suppression method according to claim 10, characterized in that: The loss of the waveguide structure is less than 0.1 dB / cm, and the loss of the semiconductor laser directly coupled to the waveguide structure is less than 0.5 dB.

12. The laser speckle suppression method according to claim 10, characterized in that: When the laser speckle suppression method is applied in an ambient temperature range of -40℃ to 85℃, the speckle contrast fluctuation does not exceed ±0.5%.

13. A laser speckle suppression method according to claim 10, characterized in that: The diversity of wavelength and polarization state of semiconductor lasers, the synergistic effect of waveguide phase perturbation and electrically tunable phase modulation, suppress the speckle contrast of the emitted laser to below 5%.

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