A rare earth ion doped lithium niobate micro-ring laser and a preparation method thereof
By fabricating lithium niobate microring lasers using femtosecond laser direct writing and chemical mechanical polishing techniques, the problem of integrating microring lasers with optoelectronic devices has been solved, enabling low-cost, high-efficiency production and multimode/single-mode laser output.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- EAST CHINA NORMAL UNIV
- Filing Date
- 2023-03-01
- Publication Date
- 2026-05-19
AI Technical Summary
Existing technologies make it difficult to integrate micro-ring lasers with other optoelectronic devices efficiently and at low cost, and the fabrication process is complex and has low processing efficiency.
A lithium niobate microring laser doped with rare earth ions was fabricated using femtosecond laser direct writing combined with chemical mechanical polishing. Multimode and single-mode lasers were achieved by changing the type and concentration of rare earth ions, and the microring structure was designed using Bezier curves.
It enables low-cost, large-scale production of lithium niobate microring lasers, reduces surface roughness, increases Q value, provides laser output in multiple wavelength bands, and facilitates integration with other optoelectronic devices.
Smart Images
Figure CN116417879B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of micro-nano integrated photonic devices and their fabrication technology, and in particular to a lithium niobate microring laser fabricated using femtosecond laser direct writing combined with chemical mechanical polishing technology, as well as the fabrication method thereon. Background Technology
[0002] Compared with thin film materials such as alumina and silica, lithium niobate has a higher refractive index and larger electro-optic, acousto-optic, and nonlinear optical coefficients. Therefore, thin-film lithium niobate has become a promising material platform for fabricating high-performance integrated optoelectronic devices. Furthermore, since lithium niobate crystals have proven to be a very suitable matrix material for rare-earth ions, on-chip microlasers can be fabricated on rare-earth ion-doped thin-film lithium niobate. [See references: P. Klopp, et al., PhD. Dissertation (University of Berlin, 2006); YQ Hu, et al., Opt. Express 29, 25663 (2021); D. Zhu, et al., Adv. Opt. Photon. 13, 242-352 (2021)].
[0003] Microdisk resonators must be coupled to a discrete tapered fiber for pump injection and signal laser extraction, which requires complex alignment techniques. Therefore, microdisk resonator-based lasers are difficult to integrate with other optoelectronic devices. Coupled microring lasers with other optoelectronic devices on the same chip can solve this problem. Currently, scientists have fabricated rare-earth-doped microring lasers using electron beam lithography and dry etching techniques; however, this method involves complex fabrication processes, requires extremely strict fabrication environments, and suffers from problems such as small write fields, low processing efficiency, and high costs. Summary of the Invention
[0004] To address the aforementioned problems, the present invention aims to design a rare-earth-doped thin-film lithium niobate microring coupled waveguide structure and utilize femtosecond laser direct writing combined with chemical mechanical polishing technology to achieve low-cost mass production of on-chip lithium niobate microring lasers.
[0005] To achieve the above objectives, the specific technical solution for realizing the objectives of this invention is as follows:
[0006] A rare-earth ion-doped lithium niobate microring laser comprises a rare-earth ion-doped lithium niobate thin film material and microrings and coupled waveguide structures etched on the thin film material. It achieves multimode lasers in different wavelength bands by changing the type and concentration of rare-earth ions, and achieves single-mode lasers through mode competition. The rare-earth ion-doped lithium niobate thin film material comprises: a first layer of rare-earth ion-doped lithium niobate thin film along the Z-direction with a thickness of 50 nm-10 μm; a second layer of silicon dioxide thin film with a thickness of 2 μm-5 μm; a third layer of thick silicon substrate with a thickness of 400 μm-600 μm; and a chromium film layer deposited on the first layer, i.e., the rare-earth ion-doped lithium niobate thin film, using magnetron sputtering technology.
[0007] The microring and coupled waveguide structure are formed by etching the lithium niobate film using femtosecond laser direct writing combined with chemical mechanical polishing technology. The microring is a ring formed by four quarter-Bezier curves.
[0008] The rare earth-doped ion is trivalent ytterbium ion, i.e., Yb. 3+ and trivalent erbium ions, i.e. Er 3+ Its concentration is 0.01 mol% - 2 mol%.
[0009] A method for fabricating the above-mentioned lithium niobate microring laser, the method comprising the following steps:
[0010] Step 1: Lithium niobate thin film material doped with rare earth ions and chromium-plated.
[0011] First, a lithium niobate thin film material doped with rare earth ions is prepared. The material includes: a first layer of lithium niobate thin film doped with rare earth ions along the Z direction with a thickness of 50 nm-10 μm; a second layer of silicon dioxide thin film with a thickness of 2 μm-5 μm; and a third layer of thick silicon substrate with a thickness of 400 μm-600 μm. A chromium film layer is then deposited on the first layer, i.e., the lithium niobate thin film doped with rare earth ions, using magnetron sputtering technology.
[0012] Step 2: Femtosecond laser direct writing
[0013] The rare earth ion-doped lithium niobate thin film material was fixed on an air bearing three-dimensional nano-displacement platform. A femtosecond laser was focused onto the chromium film using an objective lens, the displacement platform was driven to move and the femtosecond laser direct writing was started, and the chromium film was patterned into micro-rings and coupled waveguide shapes.
[0014] Step 3: Chemical Mechanical Polishing
[0015] The lithium niobate thin film material doped with rare earth ions after femtosecond laser direct writing was fixed on a chemical mechanical polishing machine, and its surface was chemically mechanically polished using a chemical polishing slurry. The lithium niobate thin film with the chromium film removed by femtosecond laser direct writing was etched, leaving a silicon dioxide support layer. The remaining part was protected by the chromium film from being etched, thus obtaining a microring and coupled waveguide structure.
[0016] Step 4: Wet chemical etching
[0017] The thin film material, after being directly written with a femtosecond laser and chemically mechanically polished, is immersed in a chemical etching solution to remove the chromium film on the surface, resulting in a rare earth-doped lithium niobate thin film material with on-chip micro-rings and a coupling waveguide, which is the lithium niobate micro-ring laser.
[0018] The chemical polishing solution contains silica microspheres with a diameter of 10-60 nm and is slightly alkaline.
[0019] The chemical corrosion solution is a 5%-10% hydrofluoric acid buffer corrosion solution.
[0020] Compared with the prior art, the advantages of the present invention are as follows:
[0021] 1. The surface average roughness of the rare-earth-doped lithium niobate thin-film microring laser prepared by chemical mechanical polishing can reach 0.1 nm. Simultaneously, the use of a quarter-Bezier curve design improves the quality factor, enabling the Q value of the microcavity to reach 10. 6 .
[0022] 2. The fabrication process of lithium niobate microring lasers by chemical mechanical polishing has higher yield and lower cost compared with the traditional semiconductor process of electron beam lithography combined with ion beam etching.
[0023] 3. The laser based on thin-film lithium niobate microrings in this invention generates multimode lasers in multiple wavelength bands, and can also generate single-mode lasers. Attached Figure Description
[0024] Figure 1 A schematic diagram of the process for manufacturing the laser of the present invention;
[0025] Figure 2 This is a top view of the lithium niobate microring laser of the present invention;
[0026] Figure 3 The present invention uses trivalent ytterbium ions (Yb). 3+ The multimode spectrum of a lithium niobate microring laser was experimentally measured.
[0027] Figure 4 The present invention uses trivalent ytterbium ions (Yb). 3+Experimentally measured single-mode spectrum of a lithium niobate microring laser;
[0028] Figure 5 The present invention is doped with trivalent erbium ions (Er). 3+ The multimode spectrum of a lithium niobate microring laser was experimentally measured.
[0029] Figure 6 The present invention is doped with trivalent erbium ions (Er). 3+ Experimentally measured single-mode spectrum of a lithium niobate microring laser. Detailed Implementation
[0030] The present invention will be further described below with reference to specific implementation methods and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.
[0031] Example 1
[0032] See Figure 1 Adding Yb 3+ The fabrication method of the lithium niobate microring laser includes the following steps:
[0033] Step 1: Prepare to add Yb 3+ Lithium niobate thin film material and chromium-plated film
[0034] First, prepare Yb-doped materials. 3+ A lithium niobate thin film material, comprising: a first layer having a thickness of 500 nm and being Yb-doped along the Z-direction. 3+ Lithium niobate film 1, wherein Yb 3+ The ion concentration is 0.5 mol%; the second layer is a 4.7 μm thick silicon dioxide thin film 2; the third layer is a 500 μm thick silicon substrate 3; and the prepared Yb-doped substrate... 3+ A chromium film layer 4 with a thickness of 200 nm was deposited on a lithium niobate thin film 1 using magnetron sputtering technology;
[0035] Step 2: Femtosecond laser direct writing
[0036] The Yb doping of the chromium-plated film on the surface 3+ The lithium niobate thin film material was fixed on an air bearing three-dimensional nano-displacement platform. A femtosecond laser was focused onto the chromium film using an objective lens, driving the displacement platform to move and initiating femtosecond laser direct writing. The chromium film was patterned into the shape of micro-ring 5 and coupled waveguide 6, where the radius of micro-ring 5 is 200μm.
[0037] Step 3: Chemical Mechanical Polishing
[0038] Yb-doped after femtosecond laser direct writing 3+The lithium niobate thin film material was fixed on a chemical mechanical polishing machine, and its surface was chemically mechanically polished using a chemical polishing slurry. The lithium niobate thin film surface was etched by femtosecond laser direct writing to remove the chromium film, leaving the silicon dioxide support layer 7. The remaining part was protected by the chromium film from being etched, thus obtaining the micro-ring 8 and the coupled waveguide 9 structure. The micro-ring 8 structure uses a quarter Bezier curve design.
[0039] Step 4: Wet chemical etching
[0040] See Figure 2 The polished structure after femtosecond laser direct writing was immersed in a chemical etching solution to remove the chromium film pattern 10 on the surface, finally obtaining Yb-doped material. 3+ A lithium niobate thin film material on-sheet microring and coupling waveguide are used to obtain the lithium niobate microring laser. The coupling gap between waveguide 9 and microring 8 is 2 μm, the coupling length is 80 μm, the top width is 2 μm, and the bottom width is 7 μm.
[0041] See Figure 3 It is the prepared Yb-doped material. 3+ The multimode laser power of the lithium niobate microring laser was measured in experiments between 1022 nm and 1028 nm.
[0042] Example 2
[0043] As described in Example 1, mode competition is used to generate single-mode laser. (See also...) Figure 4 It is the prepared Yb-doped material. 3+ The laser power of the lithium niobate microring laser in the experiment was between 1023nm and 1027nm.
[0044] Example 3
[0045] Following the preparation method described in Example 1, Er was doped along the Z-direction in the lithium niobate film. 3+ Er 3+ The ion concentration is 1 mol%, the coupling gap between waveguide 9 and microring 8 is 4.8 μm, and the width is 1 μm.
[0046] See Figure 5 It is the Er-doped material that has been prepared. 3+ The multimode laser power of the lithium niobate microring laser was measured in experiments between 1548 nm and 1554 nm.
[0047] Example 4
[0048] As described in Example 3, mode competition is used to generate single-mode laser. (See also...) Figure 6 It is the Er-doped material that has been prepared. 3+The lithium niobate microring laser achieved laser power in the experimental wavelength range of 1500nm-1570nm.
[0049] The above embodiments demonstrate that the rare-earth-doped lithium niobate microring laser of the present invention, based on femtosecond laser direct writing combined with chemical mechanical polishing (CMP), improves the average surface roughness of the laser through CMP, while the use of a quarter-Bezier curve design improves the quality factor, and it also features low cost and high production efficiency. Furthermore, by incorporating different types of rare-earth ions and mode counteraction, single-mode and multi-mode lasers in multiple bands are obtained. Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which are within the scope of protection of the invention.
Claims
1. A rare-earth ion-doped lithium niobate microring laser, characterized in that, The invention includes a rare-earth-doped lithium niobate thin film material and microrings and coupled waveguide structures etched on the thin film material. It enables multimode lasers in different wavelength bands by changing the type and concentration of rare-earth-doped ions, and single-mode lasers through mode competition. The rare-earth-doped lithium niobate thin film material comprises: a first layer of rare-earth-doped lithium niobate thin film along the Z-direction with a thickness of 50 nm-10 μm; a second layer of silicon dioxide thin film with a thickness of 2 μm-5 μm; a third layer of thick silicon substrate with a thickness of 400 μm-600 μm; and a chromium film layer deposited on the first layer, i.e., the rare-earth-doped lithium niobate thin film, using magnetron sputtering technology. The microring and coupled waveguide structure are formed by etching the lithium niobate film using femtosecond laser direct writing combined with chemical mechanical polishing technology. The microring is a ring formed by four quarter-Bezier curves. The rare earth-doped ion is trivalent ytterbium ion, i.e., Yb. 3+ and trivalent erbium ions, i.e. Er 3+ Its concentration is 0.01 mol% - 2 mol%.
2. A method for fabricating the lithium niobate microring laser according to claim 1, characterized in that, The method includes the following steps: Step 1: Lithium niobate thin film material doped with rare earth ions and chromium-plated. First, a lithium niobate thin film material doped with rare earth ions is prepared. The material includes: a first layer of lithium niobate thin film doped with rare earth ions along the Z direction with a thickness of 50 nm-10 μm; a second layer of silicon dioxide thin film with a thickness of 2 μm-5 μm; and a third layer of thick silicon substrate with a thickness of 400 μm-600 μm. A chromium film layer is then deposited on the first layer, i.e., the lithium niobate thin film doped with rare earth ions, using magnetron sputtering technology. Step 2: Femtosecond laser direct writing The rare earth ion-doped lithium niobate thin film material was fixed on an air bearing three-dimensional nano-displacement platform. A femtosecond laser was focused onto the chromium film using an objective lens, the displacement platform was driven to move and the femtosecond laser direct writing was started, and the chromium film was patterned into micro-rings and coupled waveguide shapes. Step 3: Chemical Mechanical Polishing The lithium niobate thin film material doped with rare earth ions after femtosecond laser direct writing was fixed on a chemical mechanical polishing machine, and its surface was chemically mechanically polished using a chemical polishing slurry. The lithium niobate thin film with the chromium film removed by femtosecond laser direct writing was etched, leaving a silicon dioxide support layer. The remaining part was protected by the chromium film from being etched, thus obtaining a microring and coupled waveguide structure. Step 4: Wet chemical etching The thin film material, after being directly written with a femtosecond laser and chemically mechanically polished, is immersed in a chemical etching solution to remove the chromium film on the surface, resulting in a rare earth-doped lithium niobate thin film material with on-chip micro-rings and a coupling waveguide, which is the lithium niobate micro-ring laser.
3. The preparation method according to claim 2, characterized in that, The chemical polishing solution contains silica microspheres with a diameter of 10-60 nm and is slightly alkaline.
4. The preparation method according to claim 2, characterized in that, The chemical corrosion solution is a 5%-10% hydrofluoric acid buffer corrosion solution.