Programmable acousto-optic spectrum reconstruction device and reconstruction method based on titanium diffusion lithium niobate optical waveguide

Abstract

The invention discloses a programmable acousto-optic spectrum reconstruction device and method based on a titanium diffusion lithium niobate optical waveguide. The reconstruction device comprises a lithium niobate substrate; the S-shaped double-turn-back titanium diffusion lithium niobate optical waveguide integrated on the substrate is formed by connecting at least three parallel linear waveguide sections through large-angle bending sections, and a compact plane turn-back optical path is formed; the plurality of independent acousto-optic coupling units are arranged corresponding to the straight line segments, and each unit comprises an interdigital transducer and an action area formed by exciting surface sound waves of the interdigital transducer; and the multi-channel programmable radio frequency driving system can independently control the driving signal parameters of each transducer. Multi-section independent adjustable acousto-optic coupling is achieved on a single chip, the freedom degree and flexibility of spectrum regulation and control are remarkably improved, the functions of programmable filtering, wavelength tuning, dispersion management, complex spectrum shaping and the like are achieved, the advantages of being high in integration level, high in tuning speed, flexible in reconstruction and the like are achieved, and the application range is wide. The method is suitable for the fields of ultrafast laser, optical communication, spectral processing and the like.

Description

Technical Field

[0001] This invention relates to the fields of photonics and integrated acousto-optic modulation technology, specifically to a programmable acousto-optic spectral reconstructor and reconstruction method based on a titanium diffused lithium niobate optical waveguide. Background Technology

[0002] Programmable acousto-optic spectral reconstructors are devices that utilize the interaction between sound and light waves to achieve spectral modulation, enabling controllable group delay or phase adjustment of different wavelength components. These devices have important applications in ultrafast laser pulse shaping, spectral control, optical communication, and dispersion compensation. By adjusting parameters such as the frequency and amplitude of the driving sound wave, programmable spectral reconstruction of the spectral waveform, pulse width, and phase can be achieved.

[0003] Currently, common programmable acousto-optic spectral reconstructors mainly include structures based on bulk acousto-optic effects, such as the acousto-optic programmable dispersion filter (AOPDF) proposed by Pierre Tournois. These devices typically employ acousto-optic crystals such as TeO2, utilizing the interaction between sound waves and light waves propagating longitudinally along the crystal in the bulk material to achieve spectral modulation. While these structures possess high spectral control capabilities, their reliance on acousto-optic interactions within the bulk material results in large size and low integration density, making it difficult to meet the demands for on-chip integration and miniaturization.

[0004] With the development of integrated photonics technology, on-chip acousto-optic filters based on lithium niobate have gradually become a research hotspot. For example, optical waveguides can be formed on lithium niobate substrates using titanium diffusion processes, and polarization-independent structures can be achieved by combining Mach-Zehnder (MZI) structures to realize certain tunable spectral filtering. In this type of structure, surface acoustic waves typically propagate along the substrate surface, while the path of the optical waveguide is determined by the topology of the MZI. The propagation directions of the two are not strictly collinear, which limits the effective length of the acousto-optic interaction region due to geometric constraints. Furthermore, most of these devices employ single-segment acousto-optic coupling structures, which have limitations in structural design for achieving pulse dispersion modulation, multi-segment coupling, or programmable spectral function modulation.

[0005] In summary, while some acousto-optic spectral modulation structures exist in the prior art, there is still room for improvement in achieving efficient on-chip acousto-optic coupling, multi-segment acousto-optic interaction regions, and programmable spectral reconstruction. Unlike existing single-segment Ti:LiNbO3 acousto-optic filters and TeO2 crystal-type AOPDFs, the S-shaped multi-segment foldback structure of this invention can achieve multi-point acousto-optic modulation on the same substrate and significantly increases the acousto-optic interaction distance to meet the application requirements of ultrafast laser spectral shaping and dispersion control. Furthermore, the "straight waveguide segment" mentioned in this invention refers to a functional unit that forms independent acousto-optic coupling and programmable modulation along the light propagation direction. Its geometry can be a completely straight line or an approximately straight line structure, and its length and boundaries are not limiting conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a programmable acousto-optic spectral reconstructor and reconstruction method based on a titanium-diffused lithium niobate optical waveguide. This addresses the difficulties in achieving on-chip integration of existing crystal-based programmable acousto-optic spectral reconstructors, as well as the challenges in achieving programmable spectral reconstruction due to the non-strictly aligned propagation directions of surface acoustic waves and optical waveguides in some on-chip acousto-optic filter structures, and the prevalence of single-segment acousto-optic coupling. This invention aims to improve the transmission path of the on-chip optical waveguide and the configuration of the acousto-optic coupling, enabling the device to possess multi-segment acousto-optic capabilities and flexible programmable control characteristics, making it suitable for applications such as ultrafast laser spectral shaping, dispersion compensation, and on-chip spectral processing.

[0007] The technical solution adopted in this invention is: A programmable acousto-optic spectral reconstructor based on a titanium-diffused lithium niobate optical waveguide, characterized by comprising: Lithium niobate substrate; A titanium-diffused lithium niobate optical waveguide, integrated on the lithium niobate substrate, is used to conduct optical signals. The titanium-diffused lithium niobate optical waveguide adopts an S-shaped double-foldback structure, which consists of at least three spatially parallel straight waveguide segments and two bend waveguide segments with bending angles in the range of 150° to 210° connecting adjacent straight waveguide segments, so that the optical signal can pass through the at least three straight waveguide segments sequentially along the foldback path in a single plane. Multiple acousto-optic coupling units are spatially arranged in a one-to-one correspondence with the at least three straight waveguide segments; each acousto-optic coupling unit includes: an interdigital transducer disposed in the adjacent region of its corresponding straight waveguide segment, used to excite and generate surface acoustic waves propagating in a predetermined direction in the adjacent region of the straight waveguide segment; and an acousto-optic coupling region formed by the interaction between the surface acoustic waves excited by the interdigital transducer and the guided wave light in the corresponding straight waveguide segment, each acousto-optic coupling region being spatially independent; A multi-channel programmable radio frequency drive system includes multiple radio frequency signal output channels; the multiple radio frequency signal output channels are electrically connected one-to-one with the interdigital transducers in the multiple acousto-optic coupling units, and are used to apply a radio frequency drive signal to each interdigital transducer with at least one parameter of frequency, amplitude and phase that can be independently programmed and controlled.

[0008] Furthermore, the number of the at least three straight waveguide segments is an odd number of segments greater than or equal to three, in order to form a folded-back propagation optical path.

[0009] Furthermore, the angle between the propagation direction of the surface acoustic wave and the propagation direction of light in the straight waveguide segment it acts upon is less than 30°.

[0010] Furthermore, the plurality of interdigital transducers are arranged on the surface of the lithium niobate substrate in a single row, a double row, or an alternating arrangement.

[0011] Furthermore, the multi-channel programmable radio frequency drive system is configured to perform time-division multiplexing control, frequency-division multiplexing control, or arbitrary waveform independent programming control on each interdigital transducer, so as to generate sound field distributions with different time-frequency characteristics in different acousto-optic coupling regions.

[0012] Furthermore, it also includes an auxiliary acoustic structure, which comprises: An auxiliary acoustic waveguide layer, disposed above or adjacent to the optical waveguide, is used to constrain and guide the propagation path of the surface acoustic waves; and / or A sound-absorbing structure is disposed at the end of the sound wave propagation path in the acoustic-optical coupling zone to absorb residual sound wave energy.

[0013] Furthermore, the material of the auxiliary acoustic waveguide layer is selected from silicon oxide, silicon nitride, titanium oxide, or a combination thereof; the material of the sound-absorbing structure includes polydimethylsiloxane (PDMS), aluminum, gold reflective structures, or other media materials that can limit the propagation of surface acoustic waves.

[0014] Furthermore, the titanium-diffused lithium niobate optical waveguide is formed through thermal diffusion, proton exchange, or ion doping processes, and its cross-sectional shape supports TE and TM fundamental mode transmission.

[0015] Furthermore, the surface acoustic wave is a Rayleigh wave, a Love wave, a Lamb wave, or a combination thereof.

[0016] Second, the present invention also provides a spectral reconstruction method based on the above-mentioned programmable acousto-optic spectral reconstructor, characterized in that it includes: The input optical signal is coupled into an S-shaped double-foldback titanium diffused lithium niobate optical waveguide; A set of pre-programmed radio frequency drive signals is generated by a multi-channel programmable radio frequency drive system and applied to each interdigital transducer, so that surface acoustic waves with specific frequency, amplitude and / or phase characteristics are independently generated in the adjacent area of ​​each corresponding straight waveguide segment. The input optical signal is sequentially passed through each acousto-optic coupling region along the folding path, and segmented spectral modulation is performed under the action of surface acoustic waves generated independently in each region; The output is a spectral reconstruction signal obtained after multi-segment programmable acousto-optic modulation.

[0017] Furthermore, by independently adjusting the parameters of the radio frequency drive signals applied to different interdigital transducers, at least one of the following control functions can be achieved: (a) Independently adjust the filtering depth of one or more specific wavelength components in the output spectrum; (b) Tune the center wavelength of the spectral filter continuously or discretely; (c) Program the phase response of the spectrum to achieve programmable dispersion compensation or pulse shaping; (d) A complex spectral filtering function is generated by coherently synthesizing multiple acousto-optic responses.

[0018] Third, an on-chip acousto-optic spectral processing system, characterized in that it integrates the above-mentioned programmable acousto-optic spectral reconstructor, and further includes: An input / output optical coupling interface is used to couple external optical signals to the reconfigurator and to couple processed optical signals out. A polarization beam splitter unit is disposed at the optical output end of the reconstructor or integrated into the optical waveguide, and is used to separate light of different polarization states after acousto-optic mode conversion; The control and processing unit is communicatively connected to the multi-channel programmable radio frequency drive system and is used to receive the spectral reconstruction objective function, calculate and send the drive parameters for each interdigital transducer.

[0019] The beneficial effects of this invention are: 1. Achieving multi-segment acousto-optic interaction and improving structural flexibility. Multiple straight optical waveguide segments are formed by an S-shaped double-folded waveguide structure, and a discrete three-segment acousto-optic coupling structure is adopted, enabling surface acoustic waves to act sequentially in multiple independent coupling segments, thereby achieving multi-segment acousto-optic interaction capability and providing greater structural freedom for spectral manipulation.

[0020] 2. Compared with waveguide structures that use only a single bend or less than three segments, the structure described in this invention can form multiple independent acousto-optic regions, enabling multi-point programmable acousto-optic control, thereby significantly improving the freedom, accuracy, and complexity of spectral reconstruction.

[0021] 3. Supports segmented programmable acousto-optic control. Multiple interdigital transducers form a segmented acousto-optic programmable driver array. Each acousto-optic coupling segment is driven by an independent RF output channel and can be controlled separately or in combination as needed to achieve programmable control of the acousto-optic action position, intensity, and mode.

[0022] 4. Supports multiple types of spectral reconstruction characteristics. Since each acousto-optic coupling segment is independent of each other, different radio frequency driving signals can be applied to different coupling segments to form a single-segment, dual-segment, or multi-segment combination acousto-optic grating distribution, supporting multi-frequency point modulation or spectral modulation of specific shapes.

[0023] 5. The structure is highly scalable and easy to integrate on-chip. This invention uses an on-chip titanium-diffused lithium niobate optical waveguide to achieve acousto-optic coupling. An auxiliary acoustic waveguide layer can be added as needed to improve the acoustic wave propagation path, giving the overall device structure good scalability and making it suitable for on-chip integration. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the programmable acousto-optic spectral reconstructor according to an embodiment of the present invention. Figure 2 The above is an S-shaped folded-back optical waveguide structure in an embodiment of the present invention, wherein (a) is a top view, (b) is a side view, and (c) is a perspective view.

[0025] Figure 3 This is a top view schematic diagram of the three-segment acoustic-optical coupling structure in an embodiment of the present invention.

[0026] Figure 4 This is a top view of the segmented acousto-optic programmable driver array in an embodiment of the present invention.

[0027] Figure 5 This is a schematic diagram of the multi-channel radio frequency driving logic structure in an embodiment of the present invention.

[0028] Figure 6 This describes the workflow of the programmable acousto-optic spectral reconstructor in this embodiment of the invention.

[0029] In the picture: 1-Lithium niobate substrate; 2-Input straight waveguide; 3-S-shaped folded-back optical waveguide; 4-First section of acoustic-optic coupling region; 5-Second section of acoustic-optic coupling region; 6-Third section of acoustic-optic coupling region; 7-Left interdigital transducer (IDT); 8-Right interdigital transducer; 9-Optical input port; 10-Optical output port; 11-Signal RF pad; 12-Ground RF pad; 13-Receiver-end PDMS sound-absorbing strip; 14-Transmitter-end PDMS sound-absorbing strip. Detailed Implementation

[0030] The embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the invention. Without conflict, those skilled in the art will understand that the technical features of the following embodiments can be combined with each other.

[0031] A programmable acousto-optic spectral reconstructor based on a titanium-diffused lithium niobate optical waveguide includes a titanium-diffused lithium niobate optical waveguide, multiple interdigital transducers (IDTs), and multiple IDT radio frequency interfaces for driving surface acoustic waves (SAWs). As needed, an auxiliary acoustic waveguide layer can be provided in the structure to provide propagation constraints for the SAWs. The titanium-diffused lithium niobate optical waveguide employs an S-shaped double-folded waveguide structure. This waveguide is formed by sequentially connecting multiple straight waveguide segments and two bent waveguide segments. Both bent waveguide segments are approximately 180° folded back, resulting in three (or more) substantially parallel straight optical waveguide segments. These three straight waveguide segments are located on the same substrate surface and arranged at a preset spacing. Each segment is positioned in an adjacent region of the SAW propagation path, allowing the light wave to propagate sequentially within these three straight segments.

[0032] The linear optical waveguide segment employs a discrete three-segment acousto-optic coupling structure. Multiple interdigital transducers are disposed on the surface of the optical waveguide or its adjacent region to excite surface acoustic waves (SAWs) to propagate collinearly with the optical waveguide along a predetermined direction. During propagation, the SAWs sequentially pass through the three linear optical waveguide segments, forming spatially independent acousto-optic coupling regions for each segment. If necessary, an auxiliary acoustic waveguide layer for SAW transmission can be included in the structure. This auxiliary waveguide layer, made of silicon oxide strips, is positioned above or adjacent to the optical waveguide to provide propagation constraints and improve the effective propagation path of the SAWs. The multiple interdigital transducers employ a segmented acousto-optic programmable driver array. Each interdigital transducer in this array is positioned above or adjacent to its corresponding linear optical waveguide segment and is electrically connected to an independent RF output channel of the RF control circuit. The RF control circuit provides each interdigital transducer with an tunable RF drive signal of adjustable frequency, amplitude, or phase to form independent SAW distributions in the corresponding acousto-optic coupling segments. By independently driving each interdigital transducer in the array, multiple acousto-optic coupling segments can be individually or in combination as needed, thereby achieving segmented acousto-optic modulation.

[0033] The programmable acousto-optic spectral reconstructor of this invention forms multiple straight optical waveguide segments through an S-shaped double-folded-back waveguide structure of a titanium-diffused lithium niobate optical waveguide. Interdigital transducers are placed in the vicinity of each straight optical waveguide segment to form a discrete, multi-segment acousto-optic coupling structure. These multiple interdigital transducers constitute a segmented acousto-optic programmable driver array, each electrically connected to an independent RF output channel of the RF control circuit to drive and control each acousto-optic coupling segment. The overall structure of this invention supports multi-segment acousto-optic action and programmable acousto-optic modulation.

[0034] Example 1: Overall Structure of Programmable Acousto-Optical Spectrum Reconstructor like Figure 1 As shown, this embodiment provides a programmable acousto-optic spectral reconstructor based on a titanium diffused lithium niobate optical waveguide, including a lithium niobate substrate 1, an input straight waveguide 2, an S-shaped folded-back optical waveguide 3, a first acousto-optic coupling region 4, a second acousto-optic coupling region 5, a third acousto-optic coupling region 6, a left interdigital transducer 7, a right interdigital transducer 8, an optical input port 9, an optical output port 10, a signal RF pad 11, and a ground RF pad 12.

[0035] The lithium niobate substrate 1 is x-cut, 500 μm thick, with a surface roughness of less than 2.5 nm, and a chip size of 10 mm × 5 mm. The lithium niobate substrate 1 supports the on-chip optical waveguide structure and interdigital transducer. The input straight waveguide 2 is located at the left end of the lithium niobate substrate 1 and guides external input optical signals into the device. The input straight waveguide has a width of 7 μm, a diffusion depth of 2.4 μm, and corresponds to an operating wavelength of 1053 nm.

[0036] The S-shaped folded-back waveguide 3 is composed of multiple parallel straight segments and 180° bends, enabling light to achieve a longer propagation path within a limited chip area, thereby improving the acousto-optic interaction length and modulation efficiency. The radius of the S-shaped bend in the waveguide is 6 mm, and the total propagation length is approximately 240 mm. The first acousto-optic coupling region 4, the second acousto-optic coupling region 5, and the third acousto-optic coupling region 6 are respectively located at different straight segments of the S-shaped folded-back waveguide 3 to achieve segmented acousto-optic modulation. The left interdigital transducer 7 and the right interdigital transducer 8 are respectively arranged at the left and right ends of the waveguide structure to excite, receive, or reverse propagate surface acoustic wave signals. The optical input port 9 and the optical output port 10 are located at the left and right ends of the chip, respectively, for optical signal input and output. The signal RF pad 11 and the ground RF pad 12 are connected to the interdigital transducers through microstrip lines or coplanar waveguide structures to inject external RF drive signals.

[0037] Example 2: S-shaped folded-back waveguide structure like Figure 2As shown, this embodiment presents a top view, side view, and perspective view of the S-shaped folded-back optical waveguide structure. The lithium niobate substrate 1 forms the substrate of the overall device. The input straight waveguide 2 is located on the left side of the substrate and is used to couple external optical signals into the chip. The S-shaped folded-back optical waveguide 3 consists of at least two U-shaped bends and a middle straight segment, forming a reciprocating folded-back waveguide structure, thereby achieving a longer transmission distance within a limited area. The spacing between each parallel straight segment is 12 mm, and the U-shaped bend connection angle is 180°. Optical input port 9 is located at the left end of the input straight waveguide 2; optical output port 10 is located at the rightmost end of the straight segment of the folded-back waveguide, used to output the output optical signal generated after multi-segment acousto-optic modulation. Both optical input and output ports use PM980 polarization-maintaining fiber coupling with a coupling angle of 8° to reduce reflection loss. Figure 2 (a) shows the overall shape of the folded-back waveguide in the plane and the location of the bends; Figure 2 (b) is a side view of the lithium niobate substrate 1, including the positional relationship of the optical input port 9 on the bottom surface; Figure 2 (c) shows the three-dimensional structure of the folded-back waveguide 3.

[0038] Example 3: Three-segment acoustic-optical coupling structure like Figure 3 As shown, the acousto-optic modulation structure in this embodiment adopts a three-segment arrangement, including a first acousto-optic coupling region 4, a second acousto-optic coupling region 5, and a third acousto-optic coupling region 6. The effective working lengths of the three acousto-optic coupling regions are L1=L2=L3=80mm, respectively; the corresponding center driving frequency is f=259MHz, and it is adjusted according to different reconstruction wavelengths.

[0039] Each acousto-optic coupling region consists of an acousto-optic interaction zone covering the surface of a straight segment of the waveguide, and its extent is marked with a dashed box. The three acousto-optic coupling regions are distributed along the folded-back waveguide 3, allowing the surface acoustic wave (SAW) to undergo polarization mode conversion or phase modulation with the guided wave light within each coupling segment. The waveguide cross-section is Gaussian, with a diffusion depth of 2.4 μm, supporting both TE0 and TM0 modes. Waveform arrows within the coupling regions indicate the propagation direction of the SAW, signifying the driving direction of the acoustic wave and its positional relationship with the optical path. By changing the frequency, amplitude, or phase of the acoustic wave, programmable control of the spectral response can be achieved.

[0040] Example 4: Segmented Acousto-Optical Programmable Driver Array like Figure 4As shown, this embodiment provides a segmented acousto-optic programmable driver array structure, including a left interdigital transducer 7, a right interdigital transducer 8, a signal RF pad 11, a ground RF pad 12, a receiving-end PDMS sound-absorbing strip 13, and a transmitting-end PDMS sound-absorbing strip 14. The interdigital transducers use aluminum electrodes with a thickness of 400 nm, and both the finger width and finger spacing are 4.4 μm, corresponding to an acoustic wavelength of 17.6 μm. The left interdigital transducer 7 is located near the acousto-optic coupling region on the left side of the waveguide structure and is used to excite surface acoustic wave signals propagating along the folded-back waveguide direction. The right interdigital transducer 8 is located at the right end of the waveguide and can be used to reverse-excite surface acoustic waves or receive acoustic wave signals from the left side. Each IDT contains 20 pairs of interdigits, with a length of approximately 600 μm.

[0041] Multiple transmitting-end PDMS sound-absorbing strips 14 are disposed on the left side to absorb the surface acoustic wave wake excited by the left interdigital transducer 7, reducing interference effects caused by sound wave reflection. Multiple receiving-end PDMS sound-absorbing strips 13 are disposed on the right side to absorb the surface acoustic wave arriving at the right end, suppressing reflected echoes and improving the stability of acousto-optic modulation. The PDMS sound-absorbing strips are 200 μm wide and 50 μm thick, covering the end of sound wave propagation. The signal RF pad 11 and the ground RF pad 12 are connected to each segment of the interdigital transducer via metal wiring to achieve independent drive control of the multi-segment acousto-optic modulation structure.

[0042] Example 5: Multi-channel RF drive logic like Figure 5 As shown, this embodiment provides an interface scheme for multi-channel RF driving, including RF channel 1, RF channel 2, RF channel 3, and corresponding IDT1, IDT2, and IDT3. The RF input uses an arbitrary waveform generator to generate programmable RF signals, which are then output to different RF channels. Each RF channel can provide a frequency, amplitude, or phase-adjustable drive signal to the corresponding interdigital transducer, enabling independent control of the three acousto-optic coupling zones.

[0043] This driving logic can combine the driving signals of the three coupling regions according to the target spectral response function S(Ω) to achieve programmable control of spectral reconstruction.

[0044] like Figure 6 As shown, the programmable acousto-optic spectral reconstructor of the present invention achieves spectral modulation through the following process: Step 1: The incident light enters the input straight waveguide 2 from the optical input port 9 in TE0 mode.

[0045] Step 2: The optical signal is transmitted along the S-shaped folded back optical waveguide 3, passing through the first, second and third acousto-optic coupling zones in sequence.

[0046] Step 3: In each acousto-optic coupling region, an external radio frequency signal is applied to excite surface acoustic waves in the interdigital transducer, which undergo mode conversion or phase modulation with the guided light, so that the output spectrum S2(λ) becomes the convolution relationship between the input spectrum S1(λ) and the acoustic modulation function S(Ω).

[0047] Step 4: The optical signal after three segments of programmable acousto-optic modulation is output from the optical output port 10. Its spectral shape changes according to the driving signals of each segment, thereby realizing programmable reconstruction of the spectrum.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It should be noted that although the present invention preferably employs a folded-back structure composed of three parallel straight waveguide segments, those skilled in the art will understand that as long as multiple independent acousto-optic modulation functional units are formed along the light propagation direction, and a compact folded-back optical path is achieved through bending, any changes in its geometric shape are equivalent modifications of the present invention. Any equivalent substitutions, improvements, or modifications made by those skilled in the art based on the description and drawings of the present invention within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A programmable acousto-optic spectral reconstructor based on a titanium-diffused lithium niobate optical waveguide, characterized in that, include: Lithium niobate substrate (1); A titanium-diffused lithium niobate optical waveguide is integrated on the lithium niobate substrate (1) for transmitting optical signals. The titanium-diffused lithium niobate optical waveguide adopts an S-shaped double-foldback structure, which consists of at least three straight waveguide segments arranged in parallel in space and two bent waveguide segments with bending angles in the range of 150° to 210° connecting adjacent straight waveguide segments, so that the optical signal can pass through the at least three straight waveguide segments sequentially along the foldback path in a single plane. Multiple acousto-optic coupling units are spatially arranged in a one-to-one correspondence with the at least three straight waveguide segments; each acousto-optic coupling unit includes: an interdigital transducer disposed in the adjacent region of its corresponding straight waveguide segment, used to excite and generate surface acoustic waves propagating in a predetermined direction in the adjacent region of the straight waveguide segment; and an acousto-optic coupling region formed by the interaction between the surface acoustic waves excited by the interdigital transducer and the guided wave light in the corresponding straight waveguide segment, each acousto-optic coupling region being spatially independent; A multi-channel programmable radio frequency drive system includes multiple radio frequency signal output channels; the multiple radio frequency signal output channels are electrically connected one-to-one with the interdigital transducers in the multiple acousto-optic coupling units, and are used to apply a radio frequency drive signal to each interdigital transducer with at least one parameter of frequency, amplitude and phase that can be independently programmed and controlled.

2. The programmable acousto-optic spectral reconstructor according to claim 1, characterized in that: The number of the at least three straight waveguide segments is an odd number of segments greater than or equal to three, in order to form a folded-back propagation optical path.

3. The programmable acousto-optic spectral reconstructor according to claim 1, characterized in that: The angle between the propagation direction of the surface acoustic wave and the propagation direction of light in the straight waveguide segment it acts on is less than 30°.

4. The programmable acousto-optic spectral reconstructor according to claim 1, characterized in that: The plurality of interdigital transducers are arranged on the surface of the lithium niobate substrate (1) in a single row, a double row, or an alternating arrangement.

5. The programmable acousto-optic spectral reconstructor according to claim 1, characterized in that: The multi-channel programmable radio frequency drive system is configured to perform time-division multiplexing control, frequency-division multiplexing control, or arbitrary waveform independent programming control on each interdigital transducer, so as to generate sound field distributions with different time-frequency characteristics in different acousto-optic coupling regions.

6. The programmable acousto-optic spectral reconstructor according to claim 1, characterized in that: It also includes auxiliary acoustic structures, which include: An auxiliary acoustic waveguide layer, disposed above or adjacent to the optical waveguide, is used to constrain and guide the propagation path of the surface acoustic waves; and / or A sound-absorbing structure is disposed at the end of the sound wave propagation path in the acoustic-optical coupling zone to absorb residual sound wave energy.

7. The programmable acousto-optic spectral reconstructor according to claim 6, characterized in that: The material of the auxiliary acoustic waveguide layer is selected from silicon oxide, silicon nitride, titanium oxide, or a combination thereof; the material of the sound-absorbing structure includes polydimethylsiloxane (PDMS), aluminum, gold reflective structure, or other medium materials that can limit the propagation of surface acoustic waves.

8. The programmable acousto-optic spectral reconstructor according to claim 1, characterized in that: The titanium-diffused lithium niobate optical waveguide is formed through thermal diffusion, proton exchange, or ion doping processes, and its cross-sectional shape supports TE and TM fundamental mode transmission.

9. The programmable acousto-optic spectral reconstructor according to any one of claims 1-8, characterized in that: The surface acoustic wave is a Rayleigh wave, Love wave, Lamb wave, or a combination thereof.

10. A spectral reconstruction method based on the programmable acousto-optic spectral reconstructor according to any one of claims 1 to 9, characterized in that, include: The input optical signal is coupled into an S-shaped double-foldback titanium diffused lithium niobate optical waveguide; A set of pre-programmed radio frequency drive signals is generated by a multi-channel programmable radio frequency drive system and applied to each interdigital transducer, so that surface acoustic waves with specific frequency, amplitude and / or phase characteristics are independently generated in the adjacent area of ​​each corresponding straight waveguide segment. The input optical signal is sequentially passed through each acousto-optic coupling region along the folding path, and segmented spectral modulation is performed under the action of surface acoustic waves generated independently in each region; The output is a spectral reconstruction signal obtained after multi-segment programmable acousto-optic modulation.

11. The spectral reconstruction method according to claim 10, characterized in that, By independently adjusting the parameters of the radio frequency drive signals applied to different interdigital transducers, at least one of the following control functions can be achieved: (a) Independently adjust the filtering depth of one or more specific wavelength components in the output spectrum; (b) Tune the center wavelength of the spectral filter continuously or discretely; (c) Program the phase response of the spectrum to achieve programmable dispersion compensation or pulse shaping; (d) A complex spectral filtering function is generated by coherently synthesizing multiple acousto-optic responses.

12. An on-chip acousto-optic spectroscopy processing system, characterized in that, The integrated programmable acousto-optic spectral reconstructor according to any one of claims 1 to 9 further includes: An input / output optical coupling interface is used to couple external optical signals to the reconfigurator and to couple processed optical signals out. A polarization beam splitter unit is disposed at the optical output end of the reconstructor or integrated into the optical waveguide, and is used to separate light of different polarization states after acousto-optic mode conversion; The control and processing unit is communicatively connected to the multi-channel programmable radio frequency drive system and is used to receive the spectral reconstruction objective function, calculate and send the drive parameters for each interdigital transducer.

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