CN-122018185-A - Micron-sized crystal thin film electro-optic modulator and preparation method thereof

Abstract

The invention discloses a micron-sized crystal film electro-optic modulator and a preparation method thereof, and relates to the technical field of optics. The micron-sized crystal film electro-optic modulator comprises a crystal film layer, a silicon dioxide buffer layer and a substrate layer which are sequentially stacked from top to bottom, wherein a ridge waveguide is arranged on the crystal film layer. The invention realizes the electro-optic coefficient inversion by utilizing the optical axis antiparallel x-cut lithium niobate splice, thereby realizing higher modulation speed than a single tangential lithium niobate modulator through quasi-speed matching, improving the modulation efficiency during high-speed modulation and the upper limit of the modulation speed on the basis of the original coplanar planar electrode.

Inventors

• ZHENG YUANLIN
• XU YINGDONG
• DING WENJUN
• LI HAO
• CHEN XIANFENG

Assignees

• 上海交通大学
• 上海量子科学研究中心

Dates

Publication Date

20260512

Application Date

20260402

Claims (10)

1. 1. The micron-sized crystal film electro-optic modulator comprises a crystal film layer, a silicon dioxide buffer layer and a substrate layer which are sequentially stacked from top to bottom, wherein a ridge waveguide is arranged on the crystal film layer.
2. 2. The micro-scale crystalline thin film electro-optic modulator of claim 1, wherein the thickness of the crystalline thin film layer is 2-3 μm and the thickness of the silica buffer layer is 2-5 μm.
3. 3. The electro-optic modulator of claim 1, wherein the ridge waveguide has a ridge width equal to the thickness of the crystal film layer and a ridge waveguide height 0.5-0.6 times the thickness of the crystal film layer.
4. 4. The micro-scale crystalline thin film electro-optic modulator of claim 1, wherein an included angle between the ridge waveguide sidewall and the crystalline thin film layer is 65 degrees.
5. 5. The micro-scale crystal thin film electro-optic modulator of claim 1, wherein the modulator ridge waveguide has a cross-sectional height and width that are equal and similar to the dimensions of a lensed fiber focus spot or a high numerical aperture fiber core of a measurement device.
6. 6. The electro-optic modulator of claim 1, wherein the material of the crystal film is lithium niobate or lithium tantalate.
7. 7. The micro-scale crystalline thin film electro-optic modulator of claim 1, wherein the substrate layer material is silicon, lithium niobate, or lithium tantalate.
8. 8. The micro-scale crystalline thin film electro-optic modulator of claim 7, wherein the crystalline thin film layer base layer material is the same as the crystalline thin film substrate material.
9. 9. A method for manufacturing a micro-scale crystal thin film electro-optic modulator as claimed in claim 1, comprising the steps of: Step 1, depositing a silicon dioxide buffer layer on the surface of the substrate layer; Step 2, optical-level polishing is carried out on the side face of the x-cut crystal-on-insulator film, and then two x-cut crystal-on-insulator films with antiparallel optical axes are spliced and then placed on the silicon dioxide buffer layer through a crystal bonding technology; And step 3, preparing the ridge waveguide on the spliced crystal film layer through ultraviolet exposure lithography and etching processes.
10. 10. The method of manufacturing a micro-scale crystal thin film electro-optic modulator of claim 9, wherein the etching process is dry etching.

Description

Micron-sized crystal thin film electro-optic modulator and preparation method thereof Technical Field The invention relates to the technical field of optics, in particular to a micron-sized crystal thin film electro-optical modulator and a preparation method thereof. Background An electro-optic modulator is a modulator made by using the electro-optic effect of electro-optic crystals, i.e. by applying a modulating voltage to such crystals, which causes a change in the refractive index of the crystals, resulting in a change in the phase of the transmitted light, which effects a modulation of the phase of the optical signal. Among these, lithium niobate crystals have the advantages of large transparent window (0.4-5.0 μm), high refractive index (n o=2.21, ne =2.14@1550 nm), large electro-optic coefficient (γ 33 =32 pm/V), stable physicochemical properties, and the like, and are widely applied to electro-optic modulation. The lithium niobate electro-optic modulator is a core device for realizing high-speed electro-optic modulation by utilizing the electro-optic effect of a lithium niobate material, and can realize a high-speed phase modulator and an intensity modulator by applying a microwave electric field to enable light to generate phase shift in a lithium niobate waveguide due to a linear electro-optic effect. The refractive index contrast ratio in the traditional proton exchange or titanium diffusion lithium niobate is small (delta n-0.01), only a weakly bound waveguide can be formed, the bending radius of the waveguide is in the order of a few millimeters or even centimeters, and the length of the device is generally 5-10 cm. The cross section of the weak constraint waveguide is larger, the diameter is 5-10 mu m, and the insertion loss of direct coupling with a standard optical fiber is small. But at the same time, the distance between microwave electrodes is larger, which results in higher half-wave voltage, and the device length is also required to be lengthened to reduce the driving voltage of the modulator. However, since the refractive index mismatch of the microwave and optical wave groups is more serious in long devices, the modulation bandwidth of the modulator is greatly limited. At present, the driving voltage of a bulk lithium niobate modulator is generally about 3.5V, the modulation efficiency is about 10-20V cm, the insertion loss is about 3 dB, and the electro-optic bandwidth is at most 40 GHz. The lithium niobate-based integrated optics of the lithium niobate-based technology developed in recent years is revolutionary. The refractive index contrast of the lithium niobate ridge waveguide on the insulator is very large (delta n-0.7), and the micro-nano strong constraint waveguide can be realized. At present, the performance of various devices of lithium niobate on an insulator far exceeds the limit of the traditional waveguide or bulk device. The mode of the nano waveguide is very small, so that very efficient electro-optic modulation can be realized, and the performance of the device is very good correspondingly. At present, the modulation bandwidth of the nano-film lithium niobate modulator exceeds 110 GHz, and the modulation efficiency is about 2V cm. The preparation process of the lithium niobate nano waveguide comprises electron beam exposure or deep ultraviolet lithography and dry etching. But the coupling efficiency of the nano-waveguide to the standard single-mode fiber is limited because the mode mismatch between the nano-waveguide and the standard single-mode fiber is serious, and the insertion loss of the nano-film lithium niobate waveguide device is 10-20 dB. Optical fiber input and output are required to realize low loss through a mode spot converter, although in principle and research reports, the insertion loss can be reduced to about 2 dB minimum by utilizing the mode spot converter. However, multiple electron beam exposure, etching, and deposition processes are required, and the cost of the conventional quantitative preparation process is high and has a certain challenge. In many application scenarios facing front-end users, such as optical fiber access networks, there is a certain requirement on the performance of lithium niobate electro-optical modulators, but not so high, more electro-optical devices are required to realize direct drive voltages below 2V, the modulator bandwidth is 1-10 GHz, the device insertion loss is 3 dB, the device cost is further reduced, and the large-scale deployment is facilitated. These requirements are higher than conventional proton exchange lithium niobate modulators, but do not reach the level of thin film lithium niobate modulators, and more times, the requirements are realized by considering the comprehensive performance cost performance of technology, etc., and considering lower cost and scalable preparation processes. There is no effective method in the prior art for preparing the electro-optical modulator with low cost due to the limitat