An erbium-doped aluminum nitride optical amplifier based on a bar-loaded waveguide structure and a preparation method thereof

Abstract

The application provides an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure and a preparation method thereof, and relates to the technical field of active optical waveguide.The erbium-doped aluminum nitride optical amplifier comprises a silicon substrate, a silicon dioxide lower cladding layer, an erbium-doped aluminum nitride active waveguide layer and a silicon dioxide strip-loaded layer; the strip-loaded layer extends along the light propagation direction and, together with the active waveguide layer, forms a strip-loaded waveguide structure to realize propagation mode constraint; the erbium-doped aluminum nitride active waveguide layer serves as a light guide layer and an active gain medium to realize optical signal amplification under the excitation of pump light.The application does not need to etch the active waveguide layer, can reduce transmission loss, enhance the light field and erbium ion overlapping degree, improve the gain efficiency, is compatible with the silicon-based process, and is suitable for the fields of on-chip optical communication and photonic integration.

Description

Technical Field

[0001] This invention relates to the field of active optical waveguide technology, and in particular to an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure and its fabrication method. Background Technology

[0002] With the rapid development of optical communication, optical interconnect, and photonic integrated circuit (PIC) technologies, more and more optical functional devices are being integrated onto single-chip platforms to achieve high-speed, low-power, and highly integrated information processing. Among them, on-chip optical amplifiers, as key components in photonic integrated systems, can be used to compensate for waveguide transmission loss, increase optical signal transmission distance, and enhance on-chip optical signal processing capabilities, and have significant application value in fields such as integrated optical communication, data center interconnect, and on-chip optical networks.

[0003] Currently, on-chip optical amplification is mainly achieved through two technical approaches: semiconductor optical amplifiers (SOAs) and rare-earth ion-doped waveguide amplifiers. Semiconductor optical amplifiers offer advantages such as high gain and small device size, but suffer from problems including high noise, polarization sensitivity, and poor compatibility with passive photonic platforms. In contrast, rare-earth ion-doped waveguide amplifiers utilize stimulated emission of rare-earth ions to achieve optical amplification, offering advantages such as low noise, stable operation, and easy compatibility with photonic integrated platforms, thus attracting widespread attention.

[0004] Among them, erbium ions (Er 3+ Due to its characteristic luminescent transition in the 1.53μm–1.56μm wavelength range, which is highly compatible with the C-band of optical fiber communication, erbium has become one of the most widely used rare-earth ions in the field of optical amplifiers. Under 980 nm or 1480 nm pump light excitation, erbium ions can achieve population inversion and amplify optical signals in the 1550 nm band through stimulated emission. Therefore, erbium-doped waveguide amplifiers (EDWAs) have become an important technical solution for realizing on-chip optical amplification.

[0005] Existing erbium-doped waveguide amplifiers are primarily built on silicon-based, silicon nitride, and lithium niobate material platforms. For rare-earth ion-doped waveguide amplifiers, the bandgap of the host material has a significant impact on the device's luminous efficiency and gain performance. Generally, a wider bandgap helps suppress nonradiative recombination of charge carriers and reduces the temperature quenching effect caused by thermal activation, thereby improving the radiative transition efficiency and luminous stability of rare-earth ions at room temperature. For erbium-doped material systems, Er... 3+The luminescence properties of ions are not only related to their doping concentration, but also closely related to the band structure, crystal quality, and local lattice environment of the host material. Therefore, selecting a host material with a wide bandgap is beneficial for fully utilizing Er. 3+ Luminescence and gain characteristics of ions in the 1.55 μm communication band.

[0006] Aluminum nitride (AlN) is a wide bandgap semiconductor material with a bandgap of approximately 6.2 eV and a refractive index of approximately 2.1 in the 1550 nm communication band. It also possesses advantages such as a wide transparency window, low nonlinear absorption, high thermal conductivity, excellent chemical stability, and good compatibility with silicon-based processes. Its wide bandgap characteristics effectively reduce temperature quenching effects and improve Er... 3+ The room-temperature luminescence efficiency and radiative transition probability of erbium ions make them suitable as host materials. By doping erbium ions into aluminum nitride to form erbium-doped aluminum nitride (Er:AlN) active waveguides, not only are the excellent light-guiding properties and material stability of aluminum nitride maintained, but the erbium ions can also be utilized... 3+ Stimulated emission of ions in the 1.55μm communication band enables optical signal amplification, providing a new technical approach for constructing high-gain, low-loss on-chip optical amplifiers.

[0007] In existing aluminum nitride photonic devices, waveguide structures are typically formed by etching the AlN waveguide layer. However, since the AlN etching process is not yet mature, direct etching can easily introduce sidewall roughness, surface defects, and lattice damage, thereby increasing light propagation loss and reducing the performance of optical amplifiers.

[0008] To reduce etching losses and simplify the fabrication process, we propose a strip-loaded waveguide structure. This structure, by introducing a loading structure above the dominant optical layer, modulates the local effective refractive index distribution, achieving propagation mode constraint without etching the dominant optical layer. Compared to traditional etched waveguide structures, this structure offers advantages such as lower propagation loss, simpler fabrication, and more flexible mode control.

[0009] Therefore, there is an urgent need to provide an on-chip optical amplifier based on an erbium-doped aluminum nitride active waveguide and a strip loading structure, so as to improve the interaction efficiency between the optical field and erbium ions while avoiding etching damage to the active waveguide, and achieve low-loss, high-gain on-chip optical amplification. Summary of the Invention

[0010] This invention provides an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure and its fabrication method, aiming to solve the problems of high etching loss, insufficient overlap between the optical field and the active gain region, and low gain efficiency in existing erbium-doped waveguide optical amplifiers, thereby achieving on-chip optical amplification functions with low-loss propagation, high optical field overlap factor, and high gain efficiency.

[0011] To address the sidewall roughness and scattering loss issues inherent in traditional etched waveguides, this invention employs a strip-loaded waveguide structure. An erbium-doped aluminum nitride (Er:AlN) film serves as the active light guide layer, with a silicon dioxide strip-loaded structure positioned on top. This strip-loaded structure modulates the effective refractive index distribution in the waveguide's lateral direction, achieving propagation mode constraint without requiring etching of the active waveguide layer. This reduces waveguide scattering loss and improves device fabrication yield and long-term stability.

[0012] To address the problem of insufficient interaction efficiency between the optical field and the active gain medium in existing erbium-doped waveguides, this invention utilizes the localized effective refractive index modulation effect generated by the strip loading structure to preferentially concentrate the propagation mode below the strip loading region, thereby enhancing the distribution of the optical field in the erbium-doped aluminum nitride active waveguide, increasing the spatial overlap between the optical field and erbium ions, and enhancing the interaction efficiency between light and the active medium.

[0013] To address the issue of low gain utilization in existing waveguide optical amplifiers, this invention combines a strip-loaded waveguide mechanism with an erbium-doped aluminum nitride active gain mechanism. This achieves low-loss light guiding while improving the utilization efficiency of pump and signal light in the active waveguide. When the 980nm or 1480nm pump light excites erbium ions to form population inversion, the 1550nm signal light propagating in the waveguide can interact with more excited erbium ions through stimulated emission, thereby improving the gain per unit length and pump conversion efficiency, and achieving high-efficiency on-chip optical amplification.

[0014] Furthermore, this invention uses erbium-doped aluminum nitride as the active waveguide material, which combines the advantages of aluminum nitride, such as wide transparency window, low nonlinear absorption, high thermal stability, and good silicon-based process compatibility. At the same time, it combines the simple and easy-to-process characteristics of silicon dioxide strip loading structure, which can achieve high-efficiency optical gain while ensuring low propagation loss. This provides a simple, easy-to-integrate, and high-performance technical solution for applications such as on-chip optical communication, optical interconnection, integrated optical amplifiers, and on-chip lasers.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure, comprising: Silicon substrate; A silicon dioxide undercoating layer disposed on the silicon substrate; Erbium-doped aluminum nitride active waveguide layer disposed on the silicon dioxide under cladding; A silicon dioxide strip loading layer disposed on the erbium-doped aluminum nitride active waveguide layer; The silicon dioxide strip loading layer extends along the light propagation direction and together with the erbium-doped aluminum nitride active waveguide layer, forms a strip loading waveguide structure to achieve propagation mode constraint. The erbium-doped aluminum nitride active waveguide layer serves as both a light guide layer and an active gain dielectric layer, enabling optical signal amplification under pump light excitation.

[0016] Preferably, in the above-mentioned erbium-doped aluminum nitride optical amplifier based on the strip-loaded waveguide structure, the thickness of the silicon dioxide lower cladding layer is 2~3 μm; the thickness of the erbium-doped aluminum nitride active waveguide layer is 300~500 nm; and the width of the silicon dioxide strip-loaded layer is 1~2.8 μm and the thickness is 200~300 nm.

[0017] Preferably, in the above-mentioned erbium-doped aluminum nitride optical amplifier based on the strip-loaded waveguide structure, the erbium atom doping ratio in the erbium-doped aluminum nitride active waveguide layer is 2%~4%, and the refractive index of the erbium-doped aluminum nitride active waveguide layer in the 1550nm band is 1.9~2.2.

[0018] Preferably, in the above-mentioned erbium-doped aluminum nitride optical amplifier based on the strip-loaded waveguide structure, the erbium-doped aluminum nitride active waveguide layer is prepared by DC magnetron sputtering, and erbium-aluminum alloy target material is used to achieve in-situ uniform doping of Er element in AlN lattice.

[0019] Preferably, in the above-mentioned erbium-doped aluminum nitride optical amplifier based on the strip-loaded waveguide structure, the erbium-doped aluminum nitride active waveguide layer is subjected to thermal annealing after deposition, with an annealing temperature of 1000 ℃ and an annealing time of 30 s.

[0020] Preferably, in the above-mentioned erbium-doped aluminum nitride optical amplifier based on the strip-loaded waveguide structure, the silicon dioxide strip-loaded layer is patterned using ultraviolet lithography or electron beam exposure, and is prepared by patterning the pre-deposited silicon dioxide film using an etching process.

[0021] Preferably, in the above-mentioned erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure, the optical amplifier uses 980nm or 1480nm pump light to excite the Er in the erbium-doped aluminum nitride active waveguide layer. 3+ Ions are used to amplify optical signals in the 1530~1565nm wavelength range.

[0022] Secondly, the present invention also provides a method for fabricating an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure as described above, the method comprising: S1: An erbium-doped aluminum nitride thin film is deposited on a 2-3 μm thick SiO2 thermal oxidation sheet to form an erbium-doped aluminum nitride active waveguide layer; S2: Perform thermal annealing on the erbium-doped aluminum nitride active waveguide layer; S3: Deposit a silicon dioxide thin film on the surface of the erbium-doped aluminum nitride active waveguide layer; S4: The silicon dioxide thin film is patterned and etched to form a silicon dioxide strip loading layer. The silicon dioxide strip loading layer extends along the light propagation direction and together with the erbium-doped aluminum nitride active waveguide layer, it forms a strip loading waveguide structure.

[0023] Preferably, in the above preparation method, in step S1, a DC magnetron sputtering process is used, with an erbium-aluminum alloy target as the sputtering target, and deposition is carried out in an argon and nitrogen atmosphere. The sputtering power is 150W and the deposition time is 50~60 min, forming an erbium-doped aluminum nitride active waveguide layer with a thickness of 300-500 nm.

[0024] Preferably, in the above preparation method, in step S2, the annealing temperature is 1000 ℃, the annealing time is 30 s, and the annealing is carried out under a nitrogen atmosphere, an argon atmosphere, or an argon-nitrogen mixed protective atmosphere; in step S4, a pattern is formed by ultraviolet lithography or electron beam exposure, and then the silicon dioxide strip loading layer is prepared by dry etching or wet etching. The width of the silicon dioxide strip loading layer is 1~2.8 μm, and the thickness is 200-300 nm.

[0025] The erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure and its fabrication method provided by this invention have at least the following beneficial effects: (1) This invention employs a strip-loaded waveguide structure. Lateral mode constraint is achieved by constructing a silicon dioxide strip-loaded layer above the erbium-doped aluminum nitride active waveguide layer, eliminating the need for etching the erbium-doped aluminum nitride active waveguide layer. Compared to traditional etched waveguide structures, this invention effectively avoids sidewall roughness and etching damage during the etching process, reduces propagation loss caused by sidewall scattering, and improves device processing yield and long-term operational stability.

[0026] (2) This invention utilizes a silicon dioxide strip loading structure to regulate the effective refractive index distribution in the transverse direction of the waveguide, so that the propagation mode is preferentially concentrated in the erbium-doped aluminum nitride active waveguide layer region corresponding to the strip loading region. Since the erbium-doped aluminum nitride active waveguide layer is located in the main mode distribution region, it can improve the spatial overlap between the optical field and erbium ions, enhance the interaction efficiency between light and the active medium, and thus improve the stimulated emission gain capability.

[0027] (3) This invention combines the mode modulation mechanism of the strip-loaded waveguide structure with the active gain mechanism of the erbium-doped aluminum nitride active waveguide layer, so that the pump light and signal light maintain a high optical field intensity distribution within the erbium-doped aluminum nitride active waveguide layer. When the pump light excites erbium ions to form population inversion, the signal light can interact with the excited-state erbium ions through stimulated emission, thereby improving the gain per unit length and pump utilization efficiency, and realizing efficient on-chip optical amplification.

[0028] (4) The present invention introduces thermal annealing treatment after the deposition of erbium-doped aluminum nitride active waveguide layer, which can improve the crystal quality of erbium-doped aluminum nitride film, reduce the lattice defect density, promote erbium ions to enter stable lattice positions, improve the optical activity and radiative transition probability of erbium ions, thereby enhancing the luminous intensity of communication band, further improving waveguide gain performance and reducing propagation loss.

[0029] (5) The present invention uses erbium-doped aluminum nitride as an active waveguide material. While inheriting the wide transparent window, low nonlinear absorption, high thermal conductivity and chemical stability of aluminum nitride, it introduces the active gain mechanism of erbium ions to realize the integration of light guiding and amplification functions, which is beneficial to improving device stability and manufacturing consistency.

[0030] (6) The present invention uses a silicon substrate, a silicon dioxide lower cladding layer, an erbium-doped aluminum nitride active waveguide layer, and a silicon dioxide strip loading layer to construct the main structure of the device. The erbium-doped aluminum nitride active waveguide layer is prepared by DC magnetron sputtering, and the silicon dioxide strip loading layer is patterned by photolithography and etching. The entire process does not require etching of the active waveguide layer, the process is simple and has good repeatability, and is suitable for mass production and large-scale photonic integration.

[0031] (7) This invention can be used not only as an on-chip optical amplifier in the communication band, but also as an active gain unit in on-chip lasers, amplified spontaneous emission sources, optical interconnect systems, wavelength division multiplexing communication systems and photonic integrated circuits, providing technical support for building high-performance, low-power, and highly integrated on-chip photonic systems. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0033] Figure 1 A three-dimensional structural diagram of an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure is provided for an embodiment of the present invention. Figure 2 This is a structural change diagram of an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure during the fabrication process, as provided in an embodiment of the present invention. Figure 3A flowchart illustrating a method for fabricating an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure, provided as an embodiment of the present invention; Figure 4 The mode field distribution diagram after adding a strip-loaded waveguide, obtained using simulation software, is provided for an embodiment of the present invention.

[0034] Figure label: 1. Silicon substrate; 2. Silicon dioxide undercoat; 3. Erbium-doped aluminum nitride active waveguide layer; 4. Silicon dioxide strip loading layer.

[0035] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0036] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0037] Example 1: This invention provides an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure, such as... Figure 1 As shown, the erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure includes a silicon substrate 1, a silicon dioxide lower cladding layer 2, an erbium-doped aluminum nitride active waveguide layer 3, and a silicon dioxide strip-loaded layer 4. The silicon dioxide lower cladding layer 2 is disposed on the silicon substrate 1; the erbium-doped aluminum nitride active waveguide layer 3 is disposed on the silicon dioxide lower cladding layer 2; and the silicon dioxide strip-loaded layer 4 is disposed on the erbium-doped aluminum nitride active waveguide layer 3. The silicon dioxide strip-loaded layer 4 extends along the light propagation direction and together with the erbium-doped aluminum nitride active waveguide layer 3, constitutes a strip-loaded waveguide structure to achieve propagation mode constraint. The erbium-doped aluminum nitride active waveguide layer 3 serves as a light guide layer and an active gain dielectric layer, used to amplify the optical signal under pump light excitation.

[0038] In this embodiment, a silicon dioxide strip-shaped loading layer 4 is disposed above the erbium-doped aluminum nitride active waveguide layer 3. Because the region below the silicon dioxide strip-shaped loading layer 4 has a higher local effective refractive index than the surrounding region, lateral mode confinement and optical field enhancement are achieved. Simultaneously, the erbium-doped aluminum nitride active waveguide layer 3 is located within the main mode distribution region, resulting in a high spatial overlap between the propagating modes and the erbium-doped aluminum nitride active waveguide layer 3, thus enhancing the interaction efficiency between the optical field and erbium ions.

[0039] During operation, when excited by pump light (such as 980nm pump light), the pump light and signal light are coupled and propagate into the erbium-doped aluminum nitride active waveguide layer 3. The pump light excites the erbium ions in the erbium-doped aluminum nitride active waveguide layer 3 from the ground state. 4 I 15 / 2 Leap to higher energy levels 4 I 11 / 2 It rapidly relaxes to a metastable state after nonradiative relaxation. 4 I 13 / 2 ,because 4 I 13 / 2 The energy level has a long lifetime, and erbium ions in 4 I 13 / 2 Energy levels and 4 I 15 / 2 Population inversion occurs between energy levels. When the signal light propagates through the active waveguide region where the erbium-doped aluminum nitride active waveguide layer 3 is located, the erbium ions in the excited state undergo stimulated emission under the induction of the signal light, emitting photons with the same frequency, phase, and polarization state as the signal light, thereby amplifying the signal light energy. Since the propagation mode maintains a high degree of overlap with the erbium-doped aluminum nitride active waveguide layer 3, the interaction efficiency between the optical field and erbium ions is enhanced, and high on-chip optical gain can be obtained under low propagation loss conditions.

[0040] In this embodiment, as Figure 2 As shown, the pump light (980nm or 1480nm) and the signal light (1550nm) are coupled and enter the erbium-doped aluminum nitride active waveguide layer 3 from the device input terminal, propagating forward together along the strip-loaded waveguide structure. During propagation, the pump light continuously excites erbium ions in the erbium-doped aluminum nitride active waveguide layer 3, enabling it to continuously provide stimulated emission gain along the signal light propagation path, and the signal light energy gradually increases with the propagation distance. After gain accumulation over the device length L, the signal light is output from the device output terminal, and the output signal light power Pout is greater than the input signal light power Pin, thus achieving optical signal amplification. It is understandable that the device length L can be designed according to actual gain requirements. Increasing the propagation distance can further improve the signal light output power, but the device integration density and propagation loss factors must be considered.

[0041] In some embodiments, the thickness of the silicon dioxide lower cladding layer 2 is 2~3 μm; the thickness of the erbium-doped aluminum nitride active waveguide layer 3 is 300~500 nm; and the width of the silicon dioxide strip loading layer 4 is 1~2.8 μm and the thickness is 200~300 nm.

[0042] In this embodiment, the specific values ​​of the relevant parameters are selected within the range given above and can be determined based on the operating wavelength and mode constraint requirements of the optical amplifier. Specifically, the thickness of the silicon dioxide cladding layer 2 is set to 2~3 μm to maintain a sufficient distance between the propagation mode field and the silicon substrate 1, thereby reducing substrate leakage loss; the thickness of the erbium-doped aluminum nitride active waveguide layer 3 is set to 300~500 nm, which provides sufficient light guiding thickness for the propagation mode and avoids problems such as high-order mode excitation and increased material stress caused by excessive film thickness; the width of the silicon dioxide strip loading layer 4 is set to 1~2.8 μm to match the single-mode transmission conditions of the communication band, thereby forming a stable fundamental mode constraint in the erbium-doped aluminum nitride active waveguide layer 3; the thickness of the silicon dioxide strip loading layer 4 is set to 200~300 nm to provide sufficient effective refractive index modulation amplitude to ensure lateral mode constraint capability, while avoiding additional scattering loss caused by excessive loading layer thickness.

[0043] In some embodiments, the erbium atom doping ratio in the erbium-doped aluminum nitride active waveguide layer 3 is 2% to 4%, and the refractive index of the erbium-doped aluminum nitride active waveguide layer 3 in the 1550nm band is 1.9 to 2.2.

[0044] The specific values ​​of the doping ratios mentioned above are determined based on the balance between erbium ion luminescence efficiency and concentration quenching effect. Specifically, the erbium atom doping ratio is set to 2%~4%. On the one hand, this ensures that the number of erbium ions participating in stimulated emission in the active waveguide layer is sufficient to provide effective optical gain. On the other hand, it avoids concentration quenching effects such as erbium ion clusters and energy upconversion caused by excessive doping concentration, thereby maintaining a high radiative transition probability and luminescence efficiency. The refractive index of the erbium-doped aluminum nitride active waveguide layer 3 in the 1550nm band is 1.9~2.2. This refractive index range forms a sufficient refractive index difference with silicon dioxide material (refractive index of about 1.45), enabling the strip-loaded waveguide structure to effectively constrain the propagation mode and match the single-mode transmission conditions of the communication band.

[0045] In some embodiments, the erbium-doped aluminum nitride active waveguide layer 3 is prepared by DC magnetron sputtering and erbium-aluminum alloy target material is used to achieve in-situ uniform doping of Er elements in the AlN lattice.

[0046] The reason for adopting the above preparation method is that DC magnetron sputtering has advantages such as high film quality, good composition controllability, and compatibility with silicon-based processes, making it suitable for preparing large-area, highly uniform erbium-doped aluminum nitride thin films. Using an erbium-aluminum alloy target for single-target sputtering allows for in-situ uniform doping of Er elements in the AlN lattice, avoiding compositional segregation and doping inhomogeneity problems that may occur during multi-target co-sputtering, thereby ensuring the uniformity of erbium ion distribution and batch-to-batch repeatability in the active waveguide layer. It is understood that the specific selection of the DC magnetron sputtering process and erbium-aluminum alloy target is merely illustrative and does not constitute a limitation on the scope of protection of this invention. Those skilled in the art can use other deposition methods or target forms to prepare erbium-doped aluminum nitride thin films according to the film preparation conditions.

[0047] In some embodiments, after the erbium-doped aluminum nitride active waveguide layer 3 is deposited, it undergoes thermal annealing treatment at a temperature of 1000 °C for 30 s.

[0048] The above-mentioned annealing temperature and time range are adopted because: if the annealing temperature is too low or the time is too short, it is difficult to effectively repair the lattice defects introduced during the film deposition process, and erbium ions cannot fully enter stable lattice substitution sites, resulting in low optical activity; if the annealing temperature is too high or the time is too long, it may cause increased film surface roughness, excessive grain growth, or even film cracking, which will increase light propagation loss. Annealing for 30 s within the range of 1000 ℃ can effectively improve the crystallinity of erbium-doped aluminum nitride films, reduce the lattice defect density, promote the entry of erbium ions into stable lattice sites, improve their optical activity and radiative transition probability, thereby enhancing the luminescence intensity and gain performance in the communication band.

[0049] In some embodiments, the silicon dioxide strip loading layer 4 is patterned using ultraviolet lithography or electron beam exposure, and then patterned by etching the pre-deposited silicon dioxide film.

[0050] The reason for employing the above-mentioned patterning process is that ultraviolet lithography and electron beam lithography have advantages such as high patterning accuracy, good processing repeatability, and compatibility with semiconductor processes. They can achieve the definition of strip-shaped loading structure patterns at the micron or even submicron scale, thereby precisely controlling the width and shape of the strip-shaped loading layer and ensuring the accuracy of waveguide lateral refractive index modulation. Patterning the pre-deposited silicon dioxide film through etching eliminates the need to etch the erbium-doped aluminum nitride active waveguide layer 3, avoiding sidewall roughness and lattice damage to the active waveguide layer during etching, which is beneficial for maintaining low propagation loss characteristics. It is understood that the specific methods of the above-mentioned lithography and etching processes are merely illustrative and do not constitute a limitation on the scope of protection of this invention. Those skilled in the art can select other patterning methods to prepare silicon dioxide strip-shaped loading layers according to processing accuracy requirements and equipment conditions.

[0051] In some embodiments, the optical amplifier uses 980nm or 1480nm pump light to excite Er in the erbium-doped aluminum nitride active waveguide layer 3. 3+ Ions are used to amplify optical signals in the 1530~1565nm wavelength range.

[0052] The reason for using the above pump wavelength and gain band is that 980nm and 1480nm are both Er 3+ The characteristic absorption wavelength of ions, of which 980nm pumping can Er 3+ Ions from ground state 4 I 15 / 2 Stimulate 4 I 11 / 2 Energy level, after non-radiative relaxation to metastable energy level 4 I 13 / 2 This results in population inversion; a 1480nm pump can reduce Er 3+ Ions directly from the ground state 4 I 15 / 2 Stimulate 4 I 13 / 2 Both pumping methods can effectively establish population inversion conditions at energy levels, meeting the requirements for optical amplification. The 1530~1565nm band corresponds to Er 3+ Ions from metastable energy levels 4 I 13 / 2 Transition back to ground state 4 I 15 / 2 The pump light has a characteristic emission spectral range that perfectly matches the C-band of optical fiber communication, enabling efficient optical signal amplification within this band. It is understood that the above-described pump light wavelength and signal amplification band are merely illustrative examples and do not constitute a limitation on the scope of protection of this invention. Those skilled in the art can select other pump light wavelengths or cover other gain bands based on actual pump source conditions and gain bandwidth requirements.

[0053] Example 2: This invention provides a method for fabricating an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure, such as... Figure 2 As shown, (a) is the initial structure of the silicon substrate with a silicon dioxide cladding, (b) is the active layer structure after erbium-doped aluminum nitride thin film deposition by magnetron sputtering and annealing, (c) is the dielectric layer structure after depositing a silicon dioxide thin film on the surface of the erbium-doped aluminum nitride active waveguide layer, (d) is the coating structure after spin-coating photoresist on the surface of the silicon dioxide thin film, (e) is the patterned structure after forming a strip photoresist mask by exposure and development, (f) is the intermediate structure after etching to form a silicon dioxide strip structure while retaining the photoresist, and (g) is the structure of the erbium-doped aluminum nitride optical amplifier obtained after removing the residual photoresist. The fabrication method includes the following steps S1-S4.

[0054] S1: A thermo-oxidized sheet with a surface thickness of 2~3 μm of silicon dioxide is selected as the substrate, and an erbium-doped aluminum nitride thin film is deposited on the surface of the silicon dioxide underlayer 2 to form an erbium-doped aluminum nitride active waveguide layer 3.

[0055] Step S1 aims to prepare the erbium-doped aluminum nitride active waveguide layer 3. Specifically, an erbium-doped aluminum nitride (Er:AlN) thin film can be deposited on the surface of the silicon dioxide underlayer 2 using DC magnetron sputtering. In this embodiment, an erbium-aluminum alloy target is selected as the sputtering target, wherein the erbium atom doping ratio is preferably 2% or 4%, and the erbium atom doping ratio selected in this embodiment is 4%.

[0056] In-situ uniform doping of Er elements in the AlN lattice is achieved by single-target sputtering to avoid component segregation that may occur during multi-target co-sputtering, thereby improving the uniformity and repeatability of film composition.

[0057] During the deposition process, the sample is placed in the sputtering chamber; the chamber is evacuated to a background vacuum better than 4×10-4 Pa; then high-purity argon (Ar) and high-purity nitrogen (N2) are introduced as working gases, with an Ar:N2 flow ratio of 20:16; after adjusting the working gas pressure of the chamber to the set value, the DC power supply is turned on, and the sputtering power is 150W; after the plasma stabilizes, the substrate is heated to the target temperature and kept constant; sputtering deposition is continued for 50-60 minutes to form an erbium-doped aluminum nitride active waveguide layer 3.

[0058] Preferably, the SiO2 thickness on the thermally oxidized sheet is 2-3 μm, and the thickness of the erbium-doped aluminum nitride active waveguide layer 3 is 300-500 nm. In this embodiment, the SiO2 thickness on the thermally oxidized sheet is 2 μm, and the thickness of the erbium-doped aluminum nitride active waveguide layer 3 is selected to be 400 nm.

[0059] S2: The erbium-doped aluminum nitride active waveguide layer 3 is subjected to thermal annealing.

[0060] After the deposition of the erbium-doped aluminum nitride active waveguide layer 3 is completed in step S1, the sample is subjected to thermal annealing in step S2.

[0061] In this embodiment, annealing is performed under a nitrogen atmosphere, an argon atmosphere, or a nitrogen-argon mixed protective atmosphere.

[0062] Preferably, the annealing temperature is 1000 ℃.

[0063] Preferably, the annealing time is 30 s.

[0064] Annealing treatment improves the crystallinity of erbium-doped aluminum nitride films, reduces lattice defect density, and increases Er. 3+ The optical activity and luminescence efficiency of ions are improved, thereby enhancing the waveguide's optical gain performance and reducing propagation loss.

[0065] After step S2 is completed, the corresponding Figure 2 The structure shown in (b) is shown in the diagram.

[0066] S3: A silicon dioxide thin film is deposited on the surface of the erbium-doped aluminum nitride active waveguide layer 3.

[0067] A silicon dioxide thin film is deposited on the surface of the erbium-doped aluminum nitride active waveguide layer 3 after the annealing treatment is completed in step S2.

[0068] Silica thin films can be prepared by magnetron sputtering, plasma-enhanced chemical vapor deposition (PECVD) or other thin film deposition processes. In this embodiment, magnetron sputtering is used.

[0069] Preferably, the thickness of the silicon dioxide film is 200~300 nm; in this embodiment, the thickness of the silicon dioxide film is selected as 200 nm.

[0070] The deposited silica film serves as the material layer for the subsequent strip loading structure, which is used to change the waveguide cross-sectional structure and form local effective refractive index modulation.

[0071] After step S3 is completed, the corresponding Figure 2 The structure shown in (c) is shown in the diagram.

[0072] S4: Pattern the silicon dioxide thin film to form a silicon dioxide strip loading layer 4. The silicon dioxide strip loading layer 4 extends along the light propagation direction and together with the erbium-doped aluminum nitride active waveguide layer 3, it forms a strip loading waveguide structure.

[0073] In this embodiment, step S4 is used to pattern the strip loading structure and etch the silicon dioxide strip loading layer.

[0074] Specifically, in this embodiment, photoresist is spin-coated onto the surface of the silicon dioxide thin film deposited in step S3, and after spin-coating, the corresponding... Figure 2 The structure shown in (d) is formed into a strip-loaded structure pattern using ultraviolet lithography or electron beam lithography, and then developed to obtain a strip-loaded structure mask. After development, the corresponding... Figure 2 The structure shown in (e) is shown in the diagram.

[0075] Preferably, the width of the strip loading structure is 1~2.8 μm; in this embodiment, the width of the strip loading structure is 2 μm.

[0076] Furthermore, using the photoresist pattern as an etching mask, the silicon dioxide film is patterned and etched to remove the silicon dioxide material in the unloaded areas while retaining the silicon dioxide structure in the strip-loaded areas.

[0077] The etching process in this embodiment can be reactive ion etching (RIE) or inductively coupled plasma etching (ICP). After etching, residual photoresist is removed to obtain a silicon dioxide strip-shaped loading layer 4. This silicon dioxide strip-shaped loading layer 4 is located above the erbium-doped aluminum nitride active waveguide layer 3 and extends along the light propagation direction.

[0078] Finally, through the above steps S1-S4, an erbium-doped aluminum nitride optical amplifier is formed, consisting of a silicon substrate 1, a silicon dioxide lower cladding layer 2, an erbium-doped aluminum nitride active waveguide layer 3, and a silicon dioxide strip loading layer 4. Figure 2 The structure shown in (g) is as follows.

[0079] To verify the mode confinement and optical field distribution characteristics of the erbium-doped aluminum nitride optical amplifier based on the strip-loaded waveguide structure prepared above, numerical simulation software was used to simulate and analyze the 1550nm signal optical mode field of the device cross-section. The simulation results are as follows: Figure 4 As shown. By Figure 4 As can be seen, under the action of the strip-loaded waveguide structure composed of silicon dioxide strip loading layer 4 and erbium-doped aluminum nitride active waveguide layer 3, the signal optical mode field is effectively confined within the erbium-doped aluminum nitride active waveguide layer 3 directly below the silicon dioxide strip loading layer 4. The optical energy is concentrated in the erbium-doped aluminum nitride active waveguide layer 3, and the mode field profile is elliptical. The lateral coverage range matches the width of the silicon dioxide strip loading layer 4, and the longitudinal direction is mainly confined within the erbium-doped aluminum nitride active waveguide layer 3. No obvious energy leakage to the silicon substrate 1 or the air side occurs.

[0080] The above mode field distribution results fully demonstrate that the strip-loaded waveguide structure adopted in this invention (i.e., the waveguide structure formed by the combination of silicon dioxide strip-loaded layer 4 and erbium-doped aluminum nitride active waveguide layer 3) can achieve good lateral mode confinement without etching the erbium-doped aluminum nitride active waveguide layer 3. It effectively improves the spatial overlap between the optical field and the erbium-doped aluminum nitride active waveguide layer 3, and can enhance the interaction efficiency between light and erbium ions. This provides a structural basis for improving waveguide gain per unit length and reducing transmission loss, and also verifies the rationality and effectiveness of the above strip-loaded structure in the erbium-doped aluminum nitride optical amplifier.

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure, characterized in that, include: Silicon substrate (1); A silicon dioxide undercoat (2) is disposed on the silicon substrate (1); Erbium-doped aluminum nitride active waveguide layer (3) disposed on the silicon dioxide lower cladding (2); A silicon dioxide strip loading layer (4) is disposed on the erbium-doped aluminum nitride active waveguide layer (3). The silicon dioxide strip loading layer (4) extends along the light propagation direction and together with the erbium-doped aluminum nitride active waveguide layer (3) constitutes a strip loading waveguide structure to achieve propagation mode constraint. The erbium-doped aluminum nitride active waveguide layer (3) serves as both a light guide layer and an active gain medium layer, and is used to amplify optical signals under pump light excitation.

2. The erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure according to claim 1, characterized in that, The thickness of the silicon dioxide lower cladding layer (2) is 2~3 μm; the thickness of the erbium-doped aluminum nitride active waveguide layer (3) is 300~500 nm; the width of the silicon dioxide strip loading layer (4) is 1~2.8 μm and the thickness is 200~300 nm.

3. The erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure according to claim 1, characterized in that, The erbium atom doping ratio in the erbium-doped aluminum nitride active waveguide layer (3) is 2%~4%, and the refractive index of the erbium-doped aluminum nitride active waveguide layer (3) in the 1550nm band is 1.9~2.

2.

4. The erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure according to claim 1, characterized in that, The erbium-doped aluminum nitride active waveguide layer (3) is prepared by DC magnetron sputtering and erbium-aluminum alloy target material is used to achieve in-situ uniform doping of Er element in AlN lattice.

5. The erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure according to claim 4, characterized in that, After the erbium-doped aluminum nitride active waveguide layer (3) is deposited, it is subjected to thermal annealing treatment at a temperature of 1000 ℃ and a time of 30 s.

6. The erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure according to claim 1, characterized in that, The silicon dioxide strip loading layer (4) is patterned by ultraviolet lithography or electron beam exposure process, and is prepared by etching process to pattern the pre-deposited silicon dioxide film.

7. The erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure according to claim 1, characterized in that, The optical amplifier uses 980nm or 1480nm pump light to excite the Er in the erbium-doped aluminum nitride active waveguide layer (3). 3+ Ions are used to amplify optical signals in the 1530~1565nm band.

8. A method for fabricating an erbium-doped aluminum nitride optical amplifier based on a strip-loaded waveguide structure as described in any one of claims 1 to 7, characterized in that, The preparation method includes: S1: Deposit an erbium-doped aluminum nitride thin film on a SiO2 thermo-oxidative sheet with a thickness of 2~3 μm to form an erbium-doped aluminum nitride active waveguide layer (3). S2: The erbium-doped aluminum nitride active waveguide layer (3) is subjected to thermal annealing. S3: Deposit a silicon dioxide thin film on the surface of the erbium-doped aluminum nitride active waveguide layer (3); S4: The silicon dioxide thin film is patterned and etched to form a silicon dioxide strip loading layer (4). The silicon dioxide strip loading layer (4) extends along the light propagation direction and together with the erbium-doped aluminum nitride active waveguide layer (3) constitutes a strip loading waveguide structure.

9. The preparation method according to claim 8, characterized in that, In step S2, a DC magnetron sputtering process is used, with erbium-aluminum alloy target as sputtering target, and deposition is carried out in an argon and nitrogen atmosphere. The sputtering power is 150W and the deposition time is 50~60min, forming an erbium-doped aluminum nitride active waveguide layer (3) with a thickness of 300~500 nm.

10. The preparation method according to claim 8, characterized in that, In step S3, the annealing temperature is 1000 ℃ and the annealing time is 30 s. The annealing is carried out in a nitrogen atmosphere, an argon atmosphere or an argon-nitrogen mixed protective atmosphere. In step S4, a pattern is formed by ultraviolet lithography or electron beam exposure process, and then the silicon dioxide strip loading layer (4) is prepared by dry etching or wet etching process. The width of the silicon dioxide strip loading layer (4) is 1~2.8 μm and the thickness is 200~300 nm.

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