On-chip optical amplifier and method of manufacturing the same

Abstract

The application discloses an on-chip optical amplifier and a preparation method thereof. The on-chip optical amplifier comprises an optical waveguide, an optical isolation layer, a substrate and an ion-doped layer, wherein the ion-doped layer comprises a doped layer medium and doped ions, the optical isolation layer is located between the substrate and the ion-doped layer; the ion-doped layer is tightly covered outside the optical waveguide, or is located between the optical waveguide and the optical isolation layer and is tightly attached to the optical waveguide. Compared with a conventional optical amplification mode using an erbium-doped optical fiber amplifier, an ion-doped waveguide and the like, the application can realize an integrated and chipped optical amplifier, has the characteristics of CMOS compatibility, and can realize optical-matter interaction without doping the optical waveguide device, eliminates the problem of introducing a crystal structure defect of the optical waveguide caused by direct ion doping, and guarantees optical index parameters such as dispersion and loss of the integrated photonic device.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and in particular to an on-chip optical amplifier and its fabrication method. Background Technology

[0002] The ever-increasing demands for optical communication capabilities have spurred the development of integrated photonics technology. Chip-level integrated photonic devices and the optical links and systems they form have significantly reduced the size and power consumption of optical communication devices. However, due to limitations in the scale of on-chip photonic devices, erbium-doped fiber application amplifiers (EDFAs) are typically used to amplify optical signals in applications requiring larger output signals. An EDFA is a special type of silica fiber doped with erbium (Er3+) ions. Under the action of pump light, ion beam reversal occurs in the erbium-doped fiber, generating stimulated emission, which amplifies the optical signal passing through the fiber core. However, traditional EDFA instruments are relatively large, hindering the integration and chip-level fabrication of related optical devices; furthermore, the optical signal transmission between EDFAs and chip-level integrated photonic devices often suffers from significant optical coupling loss and instability.

[0003] An optical waveguide is an on-chip photonic device that can confine light waves for propagation. Rare-earth-doped on-chip optical waveguides fabricated through methods such as ion implantation have been reported in this field (e.g., DOI: 10.1364 / OME.397011) and their optical signal amplification capabilities have been demonstrated. However, this direct ion-doping method often introduces defects into the crystal structure of the optical waveguide, increasing optical transmission loss and significantly reducing its optical performance.

[0004] Patent CN101933200A discloses a rare-earth ion-doped optical waveguide and an optical device including the waveguide, specifically an optical fiber including a core. The core is made of a rare-earth ion-doped silicon dioxide material and is covered with an optical cladding. The rare-earth ion-doped optical fiber is prepared by an impregnation method. This preparation method has low efficiency, the waveguide performance is unstable, and the optical transmission loss is high.

[0005] How to fabricate high-performance, low-loss integrated on-chip optical amplifier devices is a key issue that those skilled in the art need to focus on. Summary of the Invention

[0006] Based on the above ideas, this application provides an on-chip optical amplifier based on an ion-doped layer and its fabrication method. The ions in the doped layer interact with the evanescent field of the optical waveguide. When the signal light enters the optical waveguide, the pump light is simultaneously coupled in, resulting in optical amplification of the output optical signal. This eliminates the influence of direct ion doping on defects in the optical waveguide crystal structure and solves the problem of high optical transmission loss in traditional methods.

[0007] On one hand, the present invention provides an on-chip optical amplifier, the on-chip optical amplifier including an optical waveguide, an optical isolation layer, a substrate and an ion-doped layer, wherein the ion-doped layer includes a doped layer dielectric and doped ions, and the optical isolation layer is located between the substrate and the ion-doped layer; the ion-doped layer tightly covers the outside of the optical waveguide, or is located between the optical waveguide and the optical isolation layer and is tightly attached to the optical waveguide.

[0008] When an optical signal propagates inside an optical waveguide, the evanescent wave on its surface interacts with the dopant ions in the ion-doped layer, resulting in optical amplification of the output optical signal.

[0009] When an optical waveguide confines a light field for transmission, an optical isolation layer prevents the light mode field within the waveguide from leaking to the substrate. The doped layer provides a dielectric layer for the dopant ions to exist, while the dopant ions provide the ability to amplify light.

[0010] Furthermore, when the ion-doped layer is located between the optical waveguide and the optical isolation layer and is tightly bonded to the optical waveguide, a cladding layer is also provided outside the optical waveguide.

[0011] Furthermore, the material of the doped layer medium includes, but is not limited to, one of silicon, silicon nitride, silicon dioxide, lithium niobate, silicon carbide, tantalum oxide, tellurium oxide, aluminum oxide, zinc sulfide, tungstate, phosphate glass, bismuthate glass, fluoride glass, chalcogenide glass, III-V complex compounds, or polymers.

[0012] Furthermore, the doped ions include, but are not limited to, erbium ions (Er). 3+ ), ytterbium ions (Yb 3+ ), thulium ions (Tm 3 + ), rubidium ions (Nd) 3+ ), praseodymium ion (Pr 3+ ) or dysprosium ions (Dy 3 One of the +)

[0013] Furthermore, the material of the optical waveguide includes, but is not limited to, one of silicon, silicon nitride, silicon dioxide, lithium niobate, silicon carbide, aluminum oxide, zinc sulfide, germanium, yttrium aluminate, group III-V composite compounds, or polymers.

[0014] Furthermore, the structure of the optical waveguide includes, but is not limited to, any one of the following: strip waveguide, ridge waveguide, slit waveguide, planar waveguide, and cylindrical waveguide.

[0015] The working principle of the on-chip optical amplifier provided by this invention is as follows:

[0016] Under the influence of pump light, doped ions in the ground state transition to higher energy levels and rapidly transition to metastable states in a non-radiative manner. A large number of particles exist at these higher energy levels, achieving population inversion and enabling optical amplification. When the evanescent field of the optical signal within the waveguide comes into contact with the ion-doped layer, the metastable particles release identical photons through stimulated emission, significantly increasing the number of photons and amplifying the optical signal.

[0017] On the other hand, the present invention also provides a method for fabricating an on-chip optical amplifier, which is used to fabricate the above-mentioned on-chip optical amplifier, characterized by comprising the following steps:

[0018] Photoresist is spin-coated onto a chip with a thin-film chip, buried layer, and substrate structure. After photoresist exposure, development, fixing, and baking, a photoresist mask layer with an optical waveguide pattern is obtained.

[0019] Based on the thin film chip with the photoresist mask layer, the thin film chip is etched using an etching gas, and then ultrasonically cleaned sequentially with acetone, alcohol, and deionized water to obtain an optical waveguide;

[0020] A doped dielectric layer is fabricated on one side or the outside of an optical waveguide using thin film fabrication processes.

[0021] Ions are introduced into the doped dielectric layer through an ion doping process.

[0022] Furthermore, the methods for preparing the dielectric in the doped dielectric layer include, but are not limited to, one of plasma-enhanced chemical vapor deposition, low-pressure chemical vapor deposition, magnetron sputtering, electron beam evaporation, or atomic layer deposition.

[0023] Furthermore, methods for doping ions into a medium include, but are not limited to, one of ion implantation, liquid source ion diffusion, solid source ion diffusion, or direct deposition.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention provides an on-chip optical amplifier based on an ion-doped layer. By fabricating an ion-doped layer on an on-chip optical waveguide device, optical amplification is achieved through stimulated emission under the light-matter interaction between the evanescent field on the waveguide surface and the doped ions. This on-chip optical amplifier based on an ion-doped layer is an integrated, chip-based optical amplifier device. It achieves light-matter interaction without doping the optical waveguide device, eliminating the problem of defects in the optical waveguide crystal structure introduced by direct ion doping, and ensuring the optical parameters such as dispersion and loss of the integrated photonic device. Compared with the current method of amplifying optical signals by connecting an external active doped fiber, the on-chip optical amplifier solution based on an ion-doped layer provided by this invention uses micro-nano fabrication technology to fabricate the on-chip optical amplifier and achieves active ion doping through ion implantation and other means. Both of these process technologies are compatible with current integrated CMOS processes and are feasible. Attached Figure Description

[0026] The following is a brief explanation of the content depicted in the accompanying drawings:

[0027] Figure 1 This is a cross-sectional schematic diagram of an on-chip optical amplifier provided in Embodiment 1 of this application;

[0028] Figure 2 This is a finite element method optical mode field simulation diagram of an on-chip optical amplifier provided in Embodiment 1 of this application;

[0029] Figure 3 This is a schematic diagram illustrating the working principle of an on-chip optical amplifier provided in Embodiment 1 of this application;

[0030] Figure 4 This is a cross-sectional schematic diagram of an on-chip optical amplifier provided in Embodiment 2 of this application;

[0031] Figure 5 This is a schematic diagram of the fabrication process of an on-chip optical amplifier provided in Embodiment 3 of this application;

[0032] Figure 6 This is a schematic diagram of an on-chip optical frequency comb light source generating device with an on-chip optical amplifier provided in Embodiment 4 of this application.

[0033] In the picture:

[0034] 101-Optical waveguide, 102-Optical isolation layer, 103-Substrate, 104-Doped dielectric layer, 105-Doped ions, 106-Signal optical mode field, 501-Clad layer. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] To achieve the fabrication of high-performance, low-loss integrated on-chip optical amplifier devices, this invention provides an on-chip optical amplifier based on an ion-doped layer and its fabrication method.

[0037] This on-chip optical amplifier includes an optical waveguide 101, an optical isolation layer 102, a substrate 103, and an ion-doped layer 104. The ion-doped layer includes a doped dielectric and doped ions 105. The optical isolation layer 102 is located between the substrate 103 and the ion-doped layer 104. The ion-doped layer 104 is tightly wrapped around the outside of the optical waveguide 101, or is located between the optical waveguide 101 and the optical isolation layer 102 and is tightly attached to the optical waveguide 101.

[0038] Furthermore, when the ion-doped layer is located between the optical waveguide 101 and the optical isolation layer 102 and is tightly bonded to the optical waveguide 101, a cladding layer 501 is also provided outside the optical waveguide.

[0039] When an optical signal propagates inside an optical waveguide, the evanescent wave on its surface interacts with the dopant ions in the ion-doped layer, resulting in optical amplification of the output optical signal.

[0040] When an optical waveguide confines a light field for transmission, an optical isolation layer prevents the light mode field within the waveguide from leaking to the substrate. The doped layer provides a dielectric layer for the dopant ions to exist, while the dopant ions provide the ability to amplify light.

[0041] The process of the above preparation method will be specifically described below with reference to specific embodiments.

[0042] Example 1

[0043] This embodiment provides a structure for an on-chip optical amplifier based on an ion-doped layer, such as... Figure 1 As shown, it includes an optical waveguide 101, an optical isolation layer 102, a substrate 103, a doped dielectric layer 104, and doped ions 105. The substrate 103 is located at the bottom, the optical isolation layer 102 is located between the substrate 103 and the ion-doped layer 104, and the ion-doped layer 104 is tightly wrapped around the outside of the optical waveguide 101.

[0044] The optical waveguide 101 is made of thin-film lithium niobate, the optical isolation layer 102 is made of silicon dioxide, the substrate 103 is made of silicon, the doped dielectric layer 104 is made of aluminum oxide, and the dopant ion 105 is erbium ion (Er3+ ).

[0045] Figure 2 This is a finite element method simulation diagram of an on-chip optical amplifier based on an ion-doped layer, provided in Embodiment 1 of this application. An evanescent field 201 exists on the surface of the optical waveguide. It should be noted that... Figure 2 This is merely intended to illustrate the basic principles of the light-matter interaction between the evanescent field on the surface of an optical waveguide and external matter, and is not intended to limit the content of this application in any way.

[0046] When the on-chip optical amplifier is working, as the optical signal propagates inside the optical waveguide, the evanescent wave on its surface interacts with the dopant ions in the ion-doped layer, resulting in optical amplification of the output optical signal. The wavelength of the signal optical mode field 106 within the optical waveguide is 1550 nm. The working principle of the on-chip optical amplifier provided in this application is as follows: Figure 3 As shown, signal light 301 and pump light 302 enter the on-chip optical amplification region through optical waveguide 101. The evanescent field of signal light 301 interacts with doped ions 105 via photo-matter interaction. Under the action of pump light 302, doped ions transition from ground state level 303 to the highest energy level 304, and then undergo a non-radiative transition to a higher metastable energy level 305. When a large number of particles transition to metastable energy level 305, population inversion occurs, enabling them to acquire optical amplification capabilities and emitting identical photons that satisfy the stimulated emission condition, thus obtaining the corresponding optical amplified signal 306.

[0047] In this embodiment, the wavelength of the pump light 302 is preferably 980nm.

[0048] Example 2

[0049] This embodiment provides another structure for an on-chip optical amplifier based on an ion-doped layer, such as... Figure 4 As shown, the device includes an optical waveguide 101, an optical isolation layer 102, a substrate 103, a doped dielectric layer 104, doped ions 105, and a cladding layer 501. The substrate 103 is located at the bottom, and from top to bottom are the optical isolation layer 102, the ion-doped layer 104, and the optical waveguide 101. The optical waveguide 101 is covered by the cladding layer 501, which provides protection for the on-chip optical waveguide device.

[0050] The optical waveguide 101 is made of thin-film lithium niobate, the optical isolation layer 102 is made of silicon dioxide, the substrate 103 is made of silicon, the doped dielectric layer 104 is made of aluminum oxide, and the dopant ion 105 is erbium ion (Er 3+ ).

[0051] Example 3

[0052] This embodiment provides a method for fabricating an on-chip optical amplifier based on an ion-doped layer, such as... Figure 5As shown, it includes the following steps:

[0053] Step S401: A high-precision positive photoresist 404-1 is spin-coated onto a chip having a thin film lithium niobate 401, a silicon dioxide buried layer 402, and a silicon substrate 403. The photoresist is exposed using electron beam exposure method 405, and after processing steps such as development, fixing, and baking, a photoresist mask layer 404-2 with an optical waveguide pattern is obtained.

[0054] Step S402: On the thin film lithium niobate chip with photoresist mask layer, the thin film lithium niobate is dry etched using argon ion gas 406, and then ultrasonically cleaned by cleaning solution 407 such as acetone, alcohol, and deionized water to form thin film lithium niobate optical waveguide 101.

[0055] Step S403: Based on the existing thin-film lithium niobate optical waveguide, an alumina-doped dielectric layer 104 is prepared using magnetron sputtering method 408; based on the existing doped dielectric layer, erbium ions 105 are doped by ion implantation method 409.

[0056] Example 4

[0057] This embodiment provides an on-chip optical frequency comb light source device with an on-chip optical amplifier based on an ion-doped layer, such as... Figure 6 As shown, the on-chip optical frequency comb light source device includes an on-chip optical frequency comb light source device 601, an optical frequency comb 602, and an on-chip optical amplifier 603.

[0058] When this on-chip optical frequency comb light source device with an on-chip optical amplifier based on an ion-doped layer is in operation, the signal light 301 and the pump light 302 are coupled into the on-chip optical frequency comb light source device via the optical waveguide 101. The signal light enters the micro-ring resonator 601 through inter-waveguide coupling, and forms an optical frequency comb 602-1 through optical nonlinear effects, which is then coupled back into the optical waveguide 101. The optical frequency comb 602-1 and the pump light 302 enter the region of the on-chip optical amplifier 603 with an ion-doped layer via the optical waveguide. Under the action of the pump light, an optically amplified optical frequency comb 602-2 is obtained, which is then coupled out of the chip via the optical waveguide 101.

[0059] Preferably, in this embodiment, the optical signal 301 is selected with a wavelength of 1550nm, the pump light 302 is selected with a wavelength of 980nm, the micro-ring resonator can generate an optical frequency comb for the 1550nm narrow linewidth light source and detune for the 980nm wavelength, and the lens fiber is used to realize the coupling of fiber-chip-fiber.

[0060] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this application. For those skilled in the art, several improvements and modifications can be made to this application without departing from the principle of this application, for example:

[0061] Those skilled in the art will recognize that the interaction between the evanescent field and the ion-doped layer can be enhanced by means including but not limited to changing the geometry of the optical waveguide, such as its thickness, width, length, and bending radius, or by changing the refractive index of the optical waveguide.

[0062] Those skilled in the art will recognize that by designing structures of ion-doped layers of different types, numbers, lengths, and concentrations of doped ions, their ability to amplify light at different wavelengths can be enhanced.

[0063] Those skilled in the art can conceive of achieving light amplification under different conditions by changing the position of the ion-doped layer, the effective area, and the effects of different light-matter interactions such as ion co-doping.

[0064] Those skilled in the art can conceive of designing on-chip photonic devices such as miniature resonant cavities, Bragg gratings, and Mach-Zehnder interferometers using the aforementioned on-chip optical amplification waveguide structure to amplify the output optical signal.

[0065] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. 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 list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An on-chip optical amplifier, characterized in that, The on-chip optical amplifier includes an optical waveguide, an optical isolation layer, a substrate, and an ion-doped layer. The ion-doped layer includes a doped dielectric and doped ions. The optical isolation layer is located between the substrate and the ion-doped layer. The ion-doped layer is located between the optical waveguide and the optical isolation layer and is tightly bonded to the optical waveguide. This allows for the realization of the evanescent field on the surface of the optical waveguide and the light-matter interaction between the doped ions without doping the optical waveguide device. The optical waveguide is covered with a cladding layer, which provides protection for the optical waveguide.

2. The on-chip optical amplifier according to claim 1, characterized in that, The material of the doped layer medium is one of silicon, silicon nitride, silicon dioxide, lithium niobate, silicon carbide, tantalum oxide, tellurium oxide, aluminum oxide, zinc sulfide, tungstate, phosphate glass, bismuthate glass, fluoride glass, chalcogenide glass, III-V group composite compounds or polymers.

3. An on-chip optical amplifier according to claim 1, characterized in that, The doped ion is one of erbium ion, ytterbium ion, thulium ion, rubidium ion, praseodymium ion or dysprosium ion.

4. An on-chip optical amplifier according to claim 1, characterized in that, The optical waveguide is made of one of the following materials: silicon, silicon nitride, silicon dioxide, lithium niobate, silicon carbide, aluminum oxide, zinc sulfide, germanium, yttrium aluminate, group III-V composite compounds, or polymers.

5. An on-chip optical amplifier according to claim 1, characterized in that, The structure of the optical waveguide can be any one of the following: strip waveguide, ridge waveguide, slit waveguide, planar waveguide, and cylindrical waveguide.

6. A method for fabricating an on-chip optical amplifier, used to fabricate the on-chip optical amplifier according to any one of claims 1 to 5, characterized in that, Includes the following steps: Photoresist is spin-coated onto a chip with a thin-film chip, buried layer, and substrate structure. After photoresist exposure, development, fixing, and baking, a photoresist mask layer with an optical waveguide pattern is obtained. Based on the thin film chip with the photoresist mask layer, the thin film chip is etched using an etching gas, and then ultrasonically cleaned sequentially with acetone, alcohol, and deionized water to obtain an optical waveguide; A doped dielectric layer is fabricated on one side or the outside of an optical waveguide using thin film fabrication processes. Ions are introduced into the doped dielectric layer through an ion doping process.

7. The method for fabricating an on-chip optical amplifier according to claim 6, characterized in that, The thin film preparation process is one of plasma-enhanced chemical vapor deposition, low-pressure chemical vapor deposition, magnetron sputtering, electron beam evaporation, or atomic layer deposition.

8. The method for fabricating an on-chip optical amplifier according to claim 6, characterized in that, The ion doping process is one of ion implantation, liquid source ion diffusion, solid source ion diffusion, or direct deposition.

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