Heterogeneous integrated optical waveguide amplifier chip based on thin film lithium niobate and preparation method thereof

Abstract

The invention relates to a thin film lithium niobate-based heterogeneous integrated optical waveguide amplifier chip and a preparation method thereof, the thin film lithium niobate-based heterogeneous integrated optical waveguide amplifier chip comprises a silicon substrate layer, a lower cladding layer, a thin film lithium niobate waveguide layer, an interval cladding layer and a rare earth ion doped gain thin film layer which are sequentially stacked from bottom to top, and the interval cladding layer extends to the lower cladding layer; and the thin-film lithium niobate waveguide layer is coated by the interval cladding. The heterogeneous integrated optical waveguide amplifier chip comprises a thin film lithium niobate (TFLN) waveguide layer and a rare earth ion doped gain thin film layer on the top of the TFLN waveguide layer, and an interval wrapping layer is arranged between the TFLN waveguide layer and the rare earth ion doped gain thin film layer for separation. Wherein the rare earth ion doped gain thin film layer provides optical gain, the TFLN waveguide layer can realize mode constraint, most optical modes can be switched between the rare earth ion doped gain thin film layer and the TFLN waveguide layer only by changing the width of a TFLN strip-shaped waveguide, and high-performance broadband amplification is realized. The photonic integrated circuit has the advantages of wide gain bandwidth, high gain efficiency and good compatibility with the existing photonic integrated circuit.

Description

Technical Field

[0001] This invention relates to the field of optical waveguide amplifier technology, and in particular to a heterogeneous integrated optical waveguide amplifier chip based on thin-film lithium niobate and its fabrication method. Background Technology

[0002] Photonic integrated circuits (PICs) based on thin-film lithium niobate (TFLN) have rapidly become a hot topic due to their excellent nonlinear optical properties, ultra-low transmission loss, and superior electro-optic effects. However, as TFLN systems evolve from single-function devices to complex photonic integrated circuits, a key technological bottleneck has emerged: the lack of efficiently integrated on-chip optical amplification. The high insertion loss (≥20dB) associated with cascaded devices typically necessitates off-chip semiconductor optical amplifiers or erbium-doped fiber amplifiers, which significantly reduces integration density and stability, while limiting the development of high-density integration and low-power applications on the TFLN platform.

[0003] To address this issue, researchers have proposed various on-chip optical amplification schemes based on thin-film lithium niobate platforms in recent years. One major approach is to directly dope erbium ions into lithium niobate crystals to form erbium-doped lithium niobate waveguides. Cai, M et al. (IEEE Journal of Selected Topics in Quantum Electronics 28, (2022)) achieved an internal net gain of 16 dB with their erbium-doped lithium niobate thin-film (Er:LNOI) waveguide amplifier, but it is still fundamentally limited by the crystal structure, resulting in a limited gain bandwidth (approximately 5 nm) and spectral inhomogeneity, making it unsuitable for dense wavelength division multiplexing systems requiring broadband amplification. J. Zhou, Y. Liang, Z. Liu et al. (Laser Photonics Rev. 15, 2100221 (2021)) implemented an Er-doped LNOI-based waveguide amplifier, achieving net gain across the entire C-band, but its gain spectrum flatness was poor, with disordered peaks. Furthermore, erbium-doped thin-film lithium niobate exhibits significant polarization dependence, greatly diminishing its inherent electro-optic properties. Most importantly, smart-cut lithium niobate films are temperature-limited (requiring temperatures below 600°C), making it difficult to achieve locally doped films for hybrid passive and active photonic integrated circuits.

[0004] To date, the integration of active and passive regions in erbium-doped thin-film lithium niobate devices has primarily relied on chip-to-chip coupling or flip-chip bonding techniques, thus limiting scalability to a limited number of components. There is an urgent need to research a novel optical waveguide amplifier chip to overcome the limitations of gain, bandwidth, and integration density, thereby improving the scalability of photonic integrated circuits based on thin-film lithium niobate. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects and shortcomings of existing photonic integrated circuits based on thin-film lithium niobate, and to provide a heterogeneous integrated optical waveguide amplifier chip with wide gain bandwidth, high gain efficiency and good compatibility with existing photonic integrated circuits.

[0006] Another objective of this invention is to provide a method for fabricating a heterogeneous integrated optical waveguide amplifier chip.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] This invention protects a heterogeneous integrated optical waveguide amplifier chip, comprising, from bottom to top, a silicon substrate layer, a lower cladding layer, a thin-film lithium niobate waveguide layer, a spacer cladding layer, and a rare-earth ion-doped gain thin film layer, wherein the spacer cladding layer extends to the lower cladding layer, thereby covering the thin-film lithium niobate waveguide layer.

[0009] This invention discloses a heterogeneous integrated optical waveguide amplifier chip, comprising a TFLN waveguide layer and a top rare-earth ion-doped gain thin film layer, separated by a spacer cladding. The rare-earth ion-doped gain thin film layer provides optical gain, while the TFLN waveguide layer transmits signals and performs mode constraint, achieving high-performance broadband amplification. Simultaneously, the TFLN waveguide layer remains unmodified, retaining the excellent electro-optical properties of TFLN, and possessing advantages such as a wide gain bandwidth, high gain efficiency, and good compatibility with existing photonic integrated circuits.

[0010] Preferably, the TFLN waveguide layer is an embedded ridge waveguide layer, which is beneficial for balancing optical field confinement and pump absorption efficiency.

[0011] In some embodiments, the top-view layout of the thin-film lithium niobate waveguide layer includes a strip structure, a circular spiral structure, or a rectangular spiral structure.

[0012] In some embodiments, when the thin-film lithium niobate waveguide layer has a rectangular spiral structure, its bending radius is ≥100μm.

[0013] In some embodiments, the width of the thin-film lithium niobate waveguide layer is 0.1-4 μm, and its width-to-thickness ratio is (0.2-10):1. The spacer cladding of the present invention covers the thin-film lithium niobate waveguide layer in a bend radius-embedded manner. This large mode area (LMA) waveguide design greatly improves the mode overlap factor, ensuring that the optical mode is always concentrated in the gain region, thereby maximizing the interaction between light and the gain medium.

[0014] Preferably, the thickness of the thin-film lithium niobate waveguide layer is 0.3-1 μm.

[0015] Preferably, the width of the thin-film lithium niobate waveguide layer is 0.2-2.6 μm.

[0016] Preferably, the thin-film lithium niobate waveguide layer has a rectangular spiral structure, with a straight waveguide width of 0.2-1 μm, a curved waveguide width of 0.6-2.6 μm, and a minimum bending radius ≥100 μm, more preferably 100-300 μm.

[0017] Preferably, the thickness of the lower cladding layer is 2-5 μm.

[0018] Preferably, the thickness of the spacer cladding is 0.1-1.2 μm;

[0019] Preferably, the thickness of the rare earth ion-doped gain thin film layer is 0.3-2 μm.

[0020] In some embodiments, the upper surface of the spacer cladding is a flat surface.

[0021] In some embodiments, the host material of the rare earth ion-doped gain thin film layer is selected from at least one of alumina, tellurium oxide, or tantalum oxide; the rare earth ions doped in the rare earth ion-doped gain thin film layer are selected from at least one of erbium, ytterbium, thulium, dysprosium, or holmium ions. Preferably, the host material is alumina, and the rare earth ion is erbium ion. This invention can select appropriate rare earth elements according to the gain characteristics at different wavelengths, wherein erbium is mainly used for optical amplification around 1550nm, which is compatible with the C-band of current optical communication systems.

[0022] In some embodiments, the rare earth ion doping concentration in the rare earth ion-doped gain thin film layer is 10. 18 ~10 22 ions / cm 3 .

[0023] In some embodiments, the refractive index of the thin-film lithium niobate waveguide layer is greater than the refractive index of the rare-earth ion-doped gain thin film layer, the refractive index of the lower cladding layer is less than the refractive indices of the rare-earth ion-doped gain thin film layer and the thin-film lithium niobate waveguide layer, and the refractive index of the spacer cladding layer is less than the refractive indices of the rare-earth ion-doped gain thin film layer and the thin-film lithium niobate waveguide layer.

[0024] Preferably, the refractive index of the lower cladding layer is 1.3-1.6.

[0025] Preferably, the refractive index of the passive transmission waveguide layer is 2.13-2.21.

[0026] Preferably, the refractive index of the spacer cladding is 1.3-1.6.

[0027] Preferably, the refractive index of the rare earth ion-doped gain layer is 1.65-2.1.

[0028] A method for fabricating a heterogeneous integrated optical waveguide amplifier chip includes the following steps:

[0029] S1, Photolithography is performed on the thin film lithium niobate layer in the preset substrate to pattern the waveguide structure, and the thin film lithium niobate waveguide layer is obtained after etching; the preset substrate includes a silicon substrate layer, a lower cladding layer and a thin film lithium niobate layer stacked sequentially from bottom to top.

[0030] S2, spin-coating or depositing a spacer cladding layer on the preset substrate surface after step S1, so that the spacer cladding layer covers the thin film lithium niobate waveguide layer;

[0031] S3, a rare earth ion-doped gain thin film layer is deposited on the surface of the spacer cladding, laminated by wafer bonding or other hybrid integration methods, to obtain the heterogeneous integrated optical waveguide amplifier chip.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention provides a heterogeneous integrated optical waveguide amplifier chip, comprising a TFLN waveguide layer and a top rare-earth ion-doped gain thin film layer, separated by a spacer cladding. The rare-earth ion-doped gain thin film layer provides optical gain, while the TFLN waveguide layer transmits signals and implements mode constraint. By simply changing the width of the TFLN strip waveguide, most optical modes (greater than 90%) can be switched between the rare-earth ion-doped gain thin film layer and the TFLN waveguide layer, achieving high-performance broadband amplification. Simultaneously, the TFLN waveguide layer remains unmodified, retaining the excellent electro-optical properties of TFLN, and possessing advantages such as a wide gain bandwidth, high gain efficiency, and good compatibility with existing photonic integrated circuits.

[0034] It can achieve a broadband gain of over 30dB in the 1525-1565nm band; when monolithically integrated with the TFLN microresonator, it achieves a uniform amplification of over 12dB for all frequency components in the C-band and significantly improves spectral flatness. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a heterogeneous integrated waveguide amplifier chip according to Embodiment 1 of the present invention.

[0036] Figure 2 This is a schematic diagram of the manufacturing process of a heterogeneous integrated waveguide amplifier chip according to Embodiment 1 of this patent.

[0037] Figure 3 This is a structural and mode field distribution diagram of a heterogeneous integrated waveguide amplifier chip according to Embodiment 1 of the present invention. Figure 3 (a) is a schematic diagram of the thin-film lithium niobate waveguide layer in the heterogeneous integrated waveguide amplifier chip; (b) is a simulated mode field distribution at pump wavelengths of 1480 nm and signal wavelengths of 1533 nm.

[0038] Figure 4 This is a simulated mode field distribution diagram of a heterogeneous integrated waveguide amplifier chip at pump wavelengths of 1480nm and signal wavelengths of 1533nm, according to Embodiment 2 of the present invention.

[0039] Figure 5 This is a simulated mode field distribution diagram of a heterogeneous integrated waveguide amplifier chip in Embodiment 3 of the present invention at pump wavelengths of 1480nm and signal wavelengths of 1533nm.

[0040] Figure 6 The graph shows the relationship between the effective mode index and waveguide width of the thin-film lithium niobate waveguide layer in Embodiment 1 of the present invention for the fundamental transverse magnetic (TM0) and first-order transverse magnetic (TM1) modes at wavelengths of 1480 nm and 1533 nm.

[0041] Figure 7 This is a simulated bending loss versus radius graph for the thin-film lithium niobate waveguide layer of Embodiment 1 of the present invention. Figure 2 This is a simulated top-down view of the optical field distribution in a curved waveguide with a radius of 200 μm.

[0042] Figure 8 This is a graph showing the relationship between the internal net gain and on-chip pump power of a heterogeneous integrated waveguide amplifier chip according to Embodiment 1 of the present invention.

[0043] Figure 9 This is a gain spectrum of a heterogeneous integrated waveguide amplifier chip as a function of wavelength, according to Embodiment 1 of the present invention.

[0044] Figure 10 This is a graph showing the relationship between the gain and output power of a heterogeneous integrated waveguide amplifier chip and the input signal power, as described in Embodiment 1 of the present invention.

[0045] Figure 11 The image shows the ASE noise power spectrum of a heterogeneous integrated waveguide amplifier chip at different wavelengths, according to Embodiment 1 of the present invention.

[0046] Figure 12 This is a graph showing the relationship between ASE noise power and pump power of a heterogeneous integrated waveguide amplifier chip according to Embodiment 1 of the present invention.

[0047] Figure 13 This is a hybrid integration diagram of a heterogeneous integrated waveguide amplifier chip and a TFLN microresonator according to Embodiment 1 of the present invention. Figure 11(a) is a schematic diagram of the integrated optical system, including a Kerr optical frequency comb generator and a heterogeneous integrated waveguide amplifier; (b) shows the generated Kerr optical frequency comb with a spectral span of 1480-1620 nm; (c) shows the amplified output spectrum; and (d) shows a comparison of the power of the Kerr optical frequency comb before and after amplification. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way.

[0049] Example 1

[0050] A heterogeneous integrated optical waveguide amplifier chip based on thin-film lithium niobate, such as Figure 1 As shown, from bottom to top, it includes a silicon substrate layer 1, a lower cladding layer 2, a thin-film lithium niobate waveguide layer 3, a spacer cladding layer 4, and a rare earth ion doped gain thin film layer 5.

[0051] The refractive indices of the lower cladding layer 2, the thin-film lithium niobate waveguide layer 3, the spacer cladding layer 4, and the rare-earth ion-doped gain thin film layer 5 are denoted as n1, n2, n3, and n4, respectively, and their specific measured values ​​are: n1 = 1.45, n2: (n e =2.13, n o =2.21), n3=1.45, n4=1.663.

[0052] The lower cladding layer 2 is made of silicon dioxide (SiO2) and has a thickness of 3μm.

[0053] like Figure 3 As shown in (a), the thin-film lithium niobate (TFLN) waveguide layer 3 is made of lithium niobate and has a thickness (h1) of 0.9 μm. The thin-film lithium niobate waveguide has a rectangular spiral layout, specifically including: a narrow straight waveguide with a width (w1) of 0.2 μm, and a curved waveguide with a width of 0.8 μm (minimum bending radius of 200 μm). The narrow straight waveguide and the curved waveguide are connected by a taper structure.

[0054] The spacer cladding 4 is made of silicon dioxide, and the thickness (h2) of the spacer cladding 4 between the thin-film lithium niobate waveguide layer 3 and the rare earth ion doped gain thin film layer 5 is 0.4 μm.

[0055] The rare earth ion-doped gain thin film layer 5 is made of erbium-doped aluminum oxide (Er). 3+ Al₂O₃), with an erbium ion doping concentration of 4.9 × 10⁻⁶. 20 ions / cm 3 The thickness (h3) of the rare earth ion doped gain thin film layer 5 is 1.6 μm.

[0056] The fabrication method of the heterogeneous integrated optical waveguide amplifier chip based on thin-film lithium niobate, such as... Figure 2 As shown, it includes the following steps:

[0057] (1) Patterning is performed on the preset substrate;

[0058] Specifically, the preset substrate includes a silicon substrate layer, a lower cladding layer and a thin-film lithium niobate layer stacked sequentially from bottom to top; Ma-N 2405 electron beam resist is spin-coated on the surface of the thin-film lithium niobate, and then electron beam lithography (EBL) exposure, development and photoresist reflow are performed to pattern the waveguide.

[0059] (2) Etching to form a thin-film lithium niobate waveguide layer;

[0060] Specifically, the patterned material obtained in step (1) is used to precisely transfer the pattern onto a lithium niobate film using inductively coupled plasma reactive ion etching (ICP-RIE). After etching, RCA-1 wet cleaning is performed to thoroughly remove residual photomask and sidewall deposits, ensuring a clean and smooth waveguide surface.

[0061] (3) Depositional spacer blanket;

[0062] Specifically, a layer of SiO2 material is deposited by plasma-enhanced chemical vapor deposition (PECVD), and the SiO2 surface is precisely planarized using chemical mechanical polishing (CMP) technology to meet the requirements of subsequent coupling structures for mode overlap accuracy.

[0063] (4) Prepare erbium-doped alumina gain thin film layer;

[0064] Specifically, erbium-doped alumina (Er) was deposited by magnetron sputtering. 3+ The heterogeneous integrated optical waveguide amplifier chip is obtained by depositing Al2O3 thin films with precise control of deposition parameters and annealing treatment.

[0065] Example 2

[0066] A heterogeneous integrated optical waveguide amplifier chip based on thin-film lithium niobate differs from Embodiment 1 in that: the rare-earth ion-doped gain film of Embodiment 2 has a thickness of 2μm, and the thin-film lithium niobate waveguide layer has a rectangular spiral layout, specifically including: a straight waveguide with a thickness of 0.4μm and a width of 0.5μm, a curved waveguide with a width of 1.2μm, and a minimum bending radius of 200μm. The narrow straight waveguide and the curved waveguide are connected by a taper structure.

[0067] Example 3

[0068] A heterogeneous integrated optical waveguide amplifier chip based on thin-film lithium niobate differs from Embodiment 1 in that: the rare-earth ion-doped gain film of Embodiment 3 has a thickness of 1.8 μm, and the thin-film lithium niobate waveguide layer has a rectangular spiral layout, specifically including: a straight waveguide with a thickness of 0.45 μm and a width of 0.35 μm, a curved waveguide with a width of 1 μm, and a minimum bending radius of 200 μm. The narrow straight waveguide and the curved waveguide are connected by a taper structure.

[0069] Performance testing

[0070] 1. Simulation of mode field distribution and determination of single-mode cutoff conditions based on the Eigenmode Expansion (EME) method

[0071] The mode field distribution of a heterogeneous integrated optical waveguide amplifier chip based on thin-film lithium niobate in Example 1 was simulated by using the signal wavelength (λ = 1533 nm) and pump wavelength (λ = 1480 nm).

[0072] The results are as follows Figure 3 As shown, the TFLN waveguide width (w1) is designed to be 0.2 to 0.8 μm to selectively switch optical power between the upper gain layer and the lower guide layer. In the active amplification region (w1 = 200 nm), 94% of the TM mode is confined to erbium-doped aluminum oxide (Er) 3+ Within the Al2O3 gain thin film layer. This extremely high mode overlap factor is primarily attributed to the large mode area (LMA) waveguide design of this embodiment, which ensures that the optical mode is always concentrated in the gain region, thereby maximizing the interaction between light and the gain medium. As the waveguide width continues to expand from 0.2 μm, the effective refractive index increases accordingly, causing the mode to transition downwards through the taper structure to the curved portion of the low-loss TFLN passive transmission layer.

[0073] Similarly, the simulated model field distribution results of Examples 2 and 3 are as follows: Figure 4 , Figure 5 As shown, the TFLN waveguide width (w1) in Example 2 is designed to be 0.5 to 1.2 μm, and the TFLN waveguide width (w1) in Example 3 is designed to be 0.35 to 1 μm, which can also ensure that the mode field selectively switches between the upper gain layer and the lower guide layer.

[0074] To determine the single-mode cutoff condition of the TFLN passive waveguide, Figure 6 The effective mode refractive index and waveguide width for the fundamental transverse magnetic (TM0) and first-order transverse magnetic (TM1) modes at wavelengths of 1480 nm and 1533 nm are presented. The figure shows that the single-mode cutoff condition for the TFLN passive waveguide is 0.8 μm to ensure low-loss passive transmission. For ease of fabrication, the width of the TFLN passive transmission layer is set to 0.8 μm.

[0075] 2. Bending loss

[0076] In this embodiment, the width of the curved waveguide in the spiral-structured thin-film lithium niobate waveguide layer is 0.8 μm.

[0077] like Figure 7 As shown, bending loss decreases rapidly with increasing radius of curvature, and drops below 1 dB / cm when the radius exceeds 100 μm. Therefore, the bending radius of this embodiment 1 is 200 μm, ensuring high integration of the PIC.

[0078] 3. Relationship between internal net gain and on-chip pump power

[0079] from Figure 8 It can be seen that when the pump light wavelength is 1480nm and the amplified signal light wavelength is 1533nm, the internal net gain rapidly increases to about 25dB as the pump power increases from 0mW to 100mW. As the power further increases to 300mW, the gain gradually saturates, eventually reaching about 37dB. This phenomenon is due to the effective population inversion of erbium ions at lower pump powers, while at higher pump powers, the saturation of population inversion slows down the increase in gain.

[0080] 4. Gain as a function of wavelength

[0081] Figure 9 The image shows the simulated optical amplification gain spectrum of this embodiment. The amplifier reaches an internal net gain peak of approximately 37 dB near 1533 nm, which corresponds to the characteristic emission band of erbium ions.

[0082] In this embodiment 1, the bandwidth with a gain greater than 30dB is extended by approximately 40nm, essentially covering the entire spectral range from 1525nm to 1565nm, completely spanning the entire C-band. This wide gain bandwidth is ideally suited for wavelength division multiplexing (WDM) applications, effectively overcoming the limitation of narrow gain spectrum in traditional erbium-doped lithium niobate waveguides.

[0083] 5. Relationship between gain and output power and input signal power function

[0084] Figure 10 The saturation characteristics of the amplifier in Example 1 were further revealed. When the pump light wavelength was 1480 nm and the amplified signal light wavelength was 1533 nm, the internal net gain remained stable at approximately 37 dB within the linear range when the input power was below -40 dBm. As the input power increased, the gain gradually decreased, dropping to approximately 5 dB at an input power of 10 dBm. Correspondingly, the output signal power increased linearly at low input power levels, then gradually saturated, eventually reaching an output power of approximately 50 mW.

[0085] 6. Amplify spontaneous emission (ASE) noise power

[0086] like Figure 11 As shown, amplified spontaneous emission (ASE) noise exhibits a significant peak near the maximum gain wavelength (1533 nm), while it decreases significantly at wavelengths far from this peak, thereby improving the signal-to-noise ratio of long-wavelength signals.

[0087] like Figure 12 As shown, the ASE noise power saturates with increasing pump power, reaching a maximum at approximately 300 mW, at which point erbium ions approach complete population inversion. The results demonstrate that the heteroguide amplifier of this invention exhibits excellent gain performance throughout the C-band, which is crucial for photonic integrated circuits based on thin-film lithium niobate.

[0088] 7. PIC compatibility

[0089] To verify the compatibility of the optical waveguide amplifier in Embodiment 1 with large-scale thin-film lithium niobate photonic integrated circuits, a microring resonator was introduced into the thin-film lithium niobate layer to generate a microcomb for subsequent spectral amplification.

[0090] like Figure 13 As shown in (a), 1550 nm light is coupled into a TFLN microring resonator, generating a broadband optical frequency comb via Kerr nonlinearity. The generated comb light is then coupled into the optical waveguide amplifier of this invention via a tapered passive waveguide. Simultaneously, a 1480 nm pump is coupled into the amplifier to activate the gain.

[0091] like Figure 13 As shown in (b), the input comb-like spectral range is from 1480 nm to 1620 nm; Figure 13 As shown in (c), the amplified output spectrum has a significant gain in both the C-band and L-band.

[0092] like Figure 13 As shown in (d), a comparison of the input and amplified microcomb reveals a gain exceeding 12 dB across the entire C-band. The shortened waveguide amplifier length (4 cm) increases its saturation input power, preventing premature saturation and achieving efficient and uniform amplification over a wide spectral range. These results demonstrate the feasibility of active-passive monolithic integration and highlight the invention's ability to achieve broadband amplification for multi-wavelength signal processing. The potential of broadband, high-gain, and compatible waveguide amplifiers in TFLN photonic integrated circuits is demonstrated. Furthermore, compared to existing erbium-doped lithium niobate thin-film waveguide amplifiers, the flatness of the C-band gain spectrum in this invention is significantly improved.

[0093] The gain bandwidth and PIC compatibility of the heterogeneous integrated optical waveguide amplifier chips in Examples 2-3 are comparable to those in Example 1, and will not be described again.

[0094] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A heterogeneous integrated optical waveguide amplifier chip, characterized in that, It includes, from bottom to top, a silicon substrate layer, a lower cladding layer, a thin-film lithium niobate waveguide layer, a spacer cladding layer, and a rare-earth ion-doped gain thin film layer, wherein the spacer cladding layer extends to the lower cladding layer, so that the spacer cladding layer covers the thin-film lithium niobate waveguide layer.

2. The heterogeneous integrated optical waveguide amplifier chip according to claim 1, characterized in that, The thin-film lithium niobate waveguide layer structure includes a strip structure, a circular spiral structure, or a rectangular spiral structure.

3. The heterogeneous integrated optical waveguide amplifier chip according to claim 2, characterized in that, When the thin-film lithium niobate waveguide layer has a square spiral structure, its bending radius is ≥100μm.

4. The heterogeneous integrated optical waveguide amplifier chip according to claim 1, characterized in that, The width of the thin-film lithium niobate waveguide layer is 0.1-4 μm, and its width-to-thickness ratio is (0.2-10):

1.

5. The heterogeneous integrated optical waveguide amplifier chip according to claim 1 or 4, characterized in that, The thickness of the lower cladding layer is 2-5 μm; the thickness of the spacer cladding layer is 0.1-1.2 μm; and the thickness of the rare earth ion doped gain thin film layer is 0.3-2 μm.

6. The heterogeneous integrated optical waveguide amplifier chip according to claim 1, characterized in that, The main material of the rare earth ion doped gain thin film layer is selected from at least one of alumina, tellurium oxide or tantalum oxide; the rare earth ions doped in the rare earth ion doped gain thin film layer are selected from at least one of erbium, ytterbium, thulium, dysprosium or holmium ions.

7. The heterogeneous integrated optical waveguide amplifier chip according to claim 1 or 6, characterized in that, The rare earth ion doping concentration in the rare earth ion-doped gain thin film layer is 10. 18 ~10 22 ions / cm 3 .

8. The heterogeneous integrated optical waveguide amplifier chip according to claim 1, characterized in that, The refractive index of the thin-film lithium niobate waveguide layer is greater than that of the rare-earth ion-doped gain thin film layer, the refractive index of the lower cladding layer is less than that of the rare-earth ion-doped gain thin film layer and the thin-film lithium niobate waveguide layer, and the refractive index of the spacer cladding layer is less than that of the rare-earth ion-doped gain thin film layer and the thin-film lithium niobate waveguide layer.

9. The heterogeneous integrated optical waveguide amplifier chip according to claim 1 or 8, characterized in that, The refractive index of the lower cladding layer is 1.3-1.6; the refractive index of the thin-film lithium niobate waveguide layer is 2.13-2.21; the refractive index of the spacer cladding layer is 1.3-1.6; and the refractive index of the rare earth ion doped gain layer is 1.65-2.

1.

10. A method for fabricating a heterogeneous integrated optical waveguide amplifier chip according to any one of claims 1-9, characterized in that, Includes the following steps: S1, Photolithography is performed on the thin film lithium niobate layer in the preset substrate to pattern the waveguide structure, and the thin film lithium niobate waveguide layer is obtained after etching; the preset substrate includes a silicon substrate layer, a lower cladding layer and a thin film lithium niobate layer stacked sequentially from bottom to top. S2, spin-coating or depositing a spacer cladding layer on the preset substrate surface after step S1, so that the spacer cladding layer covers the thin film lithium niobate waveguide layer; S3, a rare earth ion-doped gain thin film layer is deposited on the surface of the spacer cladding, laminated by wafer bonding or other hybrid integration methods, to obtain the heterogeneous integrated optical waveguide amplifier chip.

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