High-brioullain gain inverted ridge type chalcogenide waveguide with air gap and preparation method thereof

Abstract

The application discloses a high-Briouin gain inverted ridge type chalcogenide waveguide with an air slit and a preparation method thereof. The chalcogenide waveguide comprises a substrate layer and a waveguide layer arranged on the substrate layer. The lower surface of the waveguide layer is outwardly convex to form a ridge type part. The ridge type part of the waveguide layer is embedded in the substrate layer to form an inverted ridge type waveguide structure. The inside of the ridge type part of the waveguide layer is provided with an air slit. The application limits the distribution areas of an optical field and an acoustic field through the inverted ridge type waveguide structure, enhances the acoustic-optical field overlap, simultaneously introduces an air slit structure, causes the appearance of optical radiation force, and makes the optical radiation force strongly coupled with the acoustic field near the air slit, enhances the coupling effect of the optical force and the acoustic field in the waveguide, and thus significantly improves the stimulated Briouin scattering gain. The waveguide structure can be applied to a laser, a microwave photon filter, slow light generation and other nonlinear optical devices.

Description

Technical Field

[0001] This invention relates to the field of chalcogenide waveguide technology, and in particular to a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps and its fabrication method. Background Technology

[0002] Stimulated Brillouin scattering is a nonlinear process of inelastic scattering, caused by phonon oscillations excited by pump light in the transmission chain through electrostriction or radiation pressure. Its principle is as follows: Figure 1 As shown, stimulated Brillouin scattering (SBS) results in the appearance of backscattered Stokes waves with a low frequency shift (several GHz below the pump light frequency) while carrying most of the pump light energy. Utilizing the advantages of SBS, such as narrow spectral linewidth, frequency stability, and gain-direction sensitivity, SBS can be applied to optical devices such as lasers, microwave photonic filters, and slow light generators. These photonic devices have increasingly broad and important application prospects in sensing, coherent optical communication systems, precision spectroscopy, and microwave photonics. Achieving low pump threshold power, realizing high-gain SBS, and meeting the requirements for on-chip miniaturization are important directions for the development of nonlinear photonics.

[0003] Ordinary silica optical fibers have low gain coefficients, requiring pump threshold power of several hundred milliwatts to achieve a certain stimulated Brillouin scattering (SBS) gain (i.e., Skochos amplification). To achieve low pump threshold power, high-gain SBS, and meet the miniaturization requirements of the device, novel chalcogenide waveguides with smaller submicron dimensions and higher SBS gain coefficients are needed. In existing technologies, some literature reports the use of inverted ridge-type chalcogenide waveguide structures, achieving a Brillouin gain coefficient of 3.77 × 10⁻⁶. 2 W -1 ·m -1 This gain coefficient is comparable to the Brillouin gain coefficient of conventional chalcogenide glass waveguides reported previously, and there is still no improvement. Based on this, research on achieving low-threshold, high-gain stimulated Brillouin scattering has attracted great attention. Chalcogenide photonics based on highly nonlinear chalcogenide glasses has developed rapidly in recent years and has become one of the most active frontier fields in the research and development of photonic functional devices internationally. Summary of the Invention

[0004] The purpose of this invention is to provide a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps and its fabrication method. The inverted ridge chalcogenide waveguide with air gaps significantly improves the stimulated Brillouin scattering gain, which is beneficial for chalcogenide photonic devices to achieve low-threshold, high-gain stimulated Brillouin scattering effects.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A high Brillouin gain inverted ridge chalcogenide waveguide with air gaps includes: a substrate layer and a waveguide layer disposed on the substrate layer, wherein the lower surface of the waveguide layer protrudes outward to form a ridge portion, the ridge portion of the waveguide layer is embedded in the substrate layer to form an inverted ridge waveguide structure, wherein an air gap is provided inside the ridge portion of the waveguide layer.

[0007] Furthermore, the substrate layer is made of silicon dioxide, and the waveguide layer is made of arsenic sulfide.

[0008] Furthermore, the waveguide layer has a thickness of 250-600nm, a ridge height of 900-950nm, a ridge width of 900-950nm, and an air gap width of 4-20nm.

[0009] Furthermore, a groove structure is provided at the center of the substrate layer, the size of which is adapted to the ridge portion, and the ridge portion of the waveguide layer is embedded in the groove structure.

[0010] Furthermore, the air gap is located at the center of the ridge section.

[0011] A method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps, as described above, includes the following steps:

[0012] S1, a substrate layer made of silicon dioxide;

[0013] S2, a groove structure of a set size is etched in the center of the substrate layer using ICP (inductively coupled plasma) etching method;

[0014] S3, Arsenic sulfide is deposited on the substrate layer etched in step S2 using a thermal evaporation method to form an arsenic sulfide thin film layer of a set thickness;

[0015] S4. Using a hot stamping method, the arsenic sulfide thin film obtained in step S3 is laminated flat to form a waveguide layer with an inverted ridge.

[0016] S5, ICP etching is used again to etch an air gap of a set width in the ridge of the flat waveguide layer.

[0017] S6. Then, arsenic sulfide is deposited on the surface of the waveguide layer etched in step S5 using a thermal evaporation method to seal the opening of the air gap and form a sealed air gap inside the ridge section.

[0018] Furthermore, in step S2, the reaction gas for the ICP etching method is a mixture of CHF3 and Ar, with a gas flow ratio of 30 sccm / 20 sccm and an etching power of 240 W.

[0019] In step S5, the reaction gas for the ICP etching method is a mixture of CF4 and CHF3, with a gas flow ratio of 30 sccm / 10 sccm and an etching power of 260 W.

[0020] Further, in step S3, before deposition using the thermal evaporation method, the substrate layer is treated sequentially with acetone, methanol, and isopropanol, then rinsed with distilled water, and then dried with a hot plate at 110°C; the vacuum chamber of the coating machine is evacuated to 6×10⁻⁶. -4 After Pa, the coating process begins, with the coating rate controlled at 20-25 nm / min. The coating is removed 60 minutes after the coating process begins.

[0021] Furthermore, in step S4, the hot embossing temperature is 250°C and the air pressure is 3 × 10⁻⁶. 5 Pa, imprinting time is 30s.

[0022] Furthermore, in step S6, before deposition using the thermal evaporation method, the waveguide layer is first rinsed with distilled water and then dried with a hot plate at 105°C; the vacuum chamber of the coating machine is evacuated to 5×10⁻⁶. -4 After Pa, the coating process begins, with the coating rate controlled at 10-15 nm / min. The coating is removed 20 minutes after the coating process begins.

[0023] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: The high Brillouin gain inverted ridge chalcogenide waveguide with air gap provided by the present invention is composed of a waveguide layer, a substrate layer and an air gap. The ridge of the waveguide layer of this novel chalcogenide waveguide is embedded in the substrate layer, and the air gap is located at the center of the ridge of the waveguide layer. By limiting the distribution area of ​​the optical field and the acoustic field through the inverted ridge structure, the overlap of the acousto-optic field is enhanced. At the same time, the introduction of the air gap structure makes the photoradiative force appear, which strongly couples with the acoustic field near the air gap, enhancing the coupling effect between the optical force and the acoustic field inside the waveguide, thereby significantly improving the stimulated Brillouin scattering gain. With the advantages of narrow spectral linewidth, frequency stability and gain direction sensitivity, it can be applied to nonlinear optical devices such as lasers, microwave photonic filters, and slow light generation. In addition, this invention also provides a method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps. By combining ICP etching, thermal evaporation and hot stamping techniques, the rapid and high-quality fabrication of chalcogenide waveguides can be achieved, which facilitates the mass production and application of chalcogenide waveguides. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the stimulated Brillouin scattering effect.

[0026] Figure 2 A schematic diagram of the structure of the high Brillouin gain inverted ridge chalcogenide waveguide with air gap provided by the present invention;

[0027] Figure 3 The optical field fundamental mode distribution diagram of the high Brillouin gain inverted ridge chalcogenide waveguide with air gap provided by the present invention;

[0028] Figure 4 The acoustic field mode distribution diagram of the high Brillouin gain inverted ridge chalcogenide waveguide with air gap provided by the present invention;

[0029] Figure 5 Stimulated Brillouin scattering gain spectrum of a high Brillouin gain inverted ridge chalcogenide waveguide with air gap provided by the present invention.

[0030] Figure 6 A flowchart illustrating the fabrication method of a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps provided by this invention;

[0031] Explanation of reference numerals in the attached figures: 1. Pump light; 2. Skethos light; 3. Acoustic wave; 4. Substrate layer; 5. Waveguide layer; 6. Air gap. Detailed Implementation

[0032] 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.

[0033] Stimulated Brillouin Scattering (SBS): Stimulated Brillouin scattering is a nonlinear process of inelastic scattering caused by phonon oscillations excited by the pump light in the transmission chain through electrostriction or radiation pressure. The SBS primarily produces backscattered Stokes waves, which exhibit a low frequency shift (several GHz below the pump light frequency) and carry most of the pump light energy. Figure 1As shown, based on the stimulated Brillouin scattering effect, it can be applied to distributed sensing, slow and fast light, microwave photonics, and narrow-linewidth Brillouin lasers, and has seen rapid development in these applications.

[0034] Brillouin gain refers to the increase or amplification of Stokes light wave power and is an important indicator for measuring the stimulated Brillouin scattering effect. Achieving high-gain stimulated Brillouin scattering with low pump threshold power while meeting the miniaturization requirements of devices is an important direction for the development of nonlinear photonics.

[0035] The purpose of this invention is to provide a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps and its fabrication method. The submicron-sized inverted ridge chalcogenide optical waveguide structure is used to better confine the optical and acoustic fields within the ridge region, resulting in a high overlap factor. At the same time, the introduction of air gaps in the ridge region causes photoradiative forces to appear, which strongly couple with the acoustic field near the air gaps, significantly improving the stimulated Brillouin scattering gain.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 2 As shown, the high Brillouin gain inverted ridge chalcogenide waveguide with air gap provided by the present invention includes: a substrate layer 4 and a waveguide layer 5 disposed on the substrate layer 4. The lower surface of the waveguide layer 5 protrudes outward to form a ridge portion, and the ridge portion of the waveguide layer 5 is embedded in the substrate layer 4 to form an inverted ridge waveguide structure. An air gap 6 is disposed inside the ridge portion of the waveguide layer 5. The air gap 6 is located at the center of the ridge portion.

[0038] The substrate layer 4 is made of SiO2 (silicon dioxide), and the waveguide layer 5 is made of As2S3 (arsenic sulfide).

[0039] Specifically, the waveguide layer 5 has a thickness c of 250-600 nm, a ridge height a of 900-950 nm, a ridge width b of 900-950 nm, and an air gap width d of 4-20 nm. For example, in a specific embodiment, the waveguide layer has a ridge height a of 910 nm, a ridge width b of 900 nm, a thickness c of 300 nm, and an air gap width d of 4 nm.

[0040] The substrate layer 4 has a groove structure at its center, the size of which is adapted to the ridge portion, and the ridge portion of the waveguide layer 5 is embedded in the groove structure.

[0041] Under the above structural parameters, Figure 3 and Figure 4The optical and acoustic field distributions of the novel chalcogenide ridge-type optical waveguide with an air gap inverted structure were obtained through experimental simulation. Figure 5 The stimulated Brillouin scattering gain spectrum of the novel chalcogenide optical waveguide structure of this invention shows that its stimulated Brillouin scattering gain coefficient is as high as 6.2 × 10⁻⁶. 4 W -1 ·m -1 Meanwhile, based on the effective mode area of ​​the optical field and the minimum effective waveguide length (for submicron-sized chalcogenide waveguides, the minimum effective length is taken as 3 cm), the pump light threshold power of the novel chalcogenide waveguide structure of this invention can be calculated to be 38 mW.

[0042] The working principle of the high Brillouin gain inverted ridge chalcogenide waveguide with air gap provided by the present invention is as follows: pump light with a power higher than the Brillouin threshold is input into the optical waveguide. Due to the electrostriction effect or photoradiation effect, optical pressure is generated, which excites sound waves in the waveguide. The sound waves are regarded as moving density gratings, which scatter the pump light and form backward Stokes light waves that migrate to lower frequencies. After this backward Stokes light wave, the spectral linewidth is narrow and the frequency is stable.

[0043] Stimulated Brillouin scattering gain coefficient G m It can be expressed by equation (1):

[0044]

[0045] In the formula, ω is the angular frequency of the light wave, and Q m This represents the mechanical quality factor, typically taken as 1000; Ω m V represents the Brillouin frequency shift of the m-th sound field mode. gp V gs Represent the group velocities of the pump beam and Skectos beam, respectively; f represents the optical force, u m E represents the displacement in the m-th sound field mode. p E s ε and ρ represent the light field intensities of the pump light and Skethos light, respectively; ε represents the relative permittivity of the waveguide, and ρ represents the waveguide density.

[0046] Equation (1) shows that the stimulated Brillouin gain coefficient is related to the energy flux of the acousto-optic field. <E p ,εE p > <E s ,εE s > m ,ρu m > The coupling effect between optical forces and sound fields | <f,u m >| 2 and the quality factor Q of the sound field loss m Therefore, to improve the Brillouin scattering gain coefficient, we need to start from these three points. ​

[0047] This invention mainly improves the Brillouin scattering gain coefficient by enhancing the coupling effect between optical force and sound field, that is, by utilizing the strong coupling effect between strong optical force and sound field.

[0048] This invention employs an inverted ridge waveguide structure, distinct from traditional ridge waveguides. Specifically, an inverted As2S3 ridge structure is embedded within SiO2. The significant difference in sound velocity between As2S3 and SiO2 effectively confines sound waves within the ridge region, resulting in strong coupling between the sound and optical fields and achieving high Brillouin gain. Simultaneously, the introduction of air gaps allows for greater photoradiative forces at the boundary between air and the chalcogenide glass material, further enhancing the coupling strength between the optical force and the sound field.

[0049] Figure 5 The stimulated Brillouin scattering gain coefficient spectrum of the novel chalcogenide ridge waveguide with air gap inverted structure of the present invention was calculated using equation (1), showing that the stimulated Brillouin scattering gain coefficient is as high as 6.2 × 10⁻⁶. 4 W -1 ·m -1 Its spectral linewidth is narrow, approximately 30 MHz.

[0050] The power gain threshold of the pump light is calculated using equation (2):

[0051]

[0052] In the formula, L eff It is the effective length, A eff It is the effective modulus area, G m It is the stimulated Brillouin scattering gain coefficient.

[0053] In summary, the structural features of the high Brillouin gain inverted ridge chalcogenide waveguide with air gap described in this invention are as follows:

[0054] (1) The chalcogenide waveguide structure of the present invention adopts an inverted ridge structure with air gaps. The inverted ridge structure restricts the distribution area of ​​the optical field and the acoustic field, and enhances the overlap of the acousto-optic field. At the same time, the introduction of the air gap structure enhances the coupling effect between the optical force and the acoustic field inside the waveguide. This greatly improves the stimulated Brillouin scattering gain coefficient, which is as high as 6.2 × 10⁻⁶. 4 W -1 ·m -1 It is much higher than existing ridge-type chalcogenide waveguides, and its Brillouin gain threshold power (pump light threshold power) is even lower, reduced to 38mW.

[0055] (2) The chalcogenide waveguide structure of the present invention has a submicron size that meets the requirements of miniaturization, integration and high efficiency of integrated photonic devices, and has the advantages of on-chip.

[0056] On the other hand, the present invention also provides a method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps as described above, such as... Figure 6 As shown, the specific steps include:

[0057] S1, a substrate layer made of silicon dioxide;

[0058] S2 uses ICP (inductively coupled plasma) etching to etch a groove structure with a width of 900nm and a depth of 910nm in the center of a SiO2 substrate layer with a thickness of about 1mm. The reaction gas is a mixture of CHF3 (trifluoromethane) and Ar (argon) with a gas flow ratio of 30sccm / 20sccm and an etching power of 240W.

[0059] S3. As2S3 is deposited on the SiO2 substrate obtained in step S2 using a thermal evaporation method, forming an As2S3 waveguide layer film with a thickness of approximately 1.2 μm on its surface. Before deposition, the SiO2 substrate is treated sequentially with acetone, methanol, and isopropanol, then rinsed with distilled water, and dried on a hot plate at 110°C; the vacuum chamber of the coating machine is evacuated to 6 × 10⁻⁶. -4 After Pa, the coating process begins, and the coating rate is controlled at 20-25 nm / min. The coating is removed approximately 60 minutes after the coating process begins.

[0060] S4. The As2S3 thin film obtained in the previous step is flattened using a hot embossing method to form an inverted chalcogenide ridge-type optical waveguide. The embossing temperature is controlled at 250℃ and the gas pressure at 3×10⁻⁶. 5 Pa, imprinting time approximately 30 seconds;

[0061] S5. ICP etching was used again to etch a slit about 15 nm wide on the flat As2S3 film. The etching gas was a mixture of CF4 (carbon tetrafluoride) and CHF3 with a gas flow ratio of 30 sccm / 10 sccm and an etching power of 260 W.

[0062] S6. Then, using thermal evaporation, As2S3 is deposited onto the etched As2S3 film to form an As2S3 film of a certain thickness, sealing the openings of the air gaps etched in the previous step, creating a sealed air gap inside the ridge. Before deposition, the As2S3 film is rinsed with distilled water and then dried on a hot plate at 105°C; the vacuum chamber of the coating machine is evacuated to 5 × 10⁻⁶. -4 After Pa, the coating process begins, with the coating rate controlled at 10-15 nm / min. The coating is removed approximately 20 minutes after the coating process begins.

[0063] After completing all the above preparation steps, a novel high Brillouin gain chalcogenide ridge waveguide with an air gap inverted structure as described in this invention can be obtained.

[0064] The present invention provides a method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps, which combines ICP etching, thermal evaporation and hot stamping techniques. The fabrication process is simple and enables rapid and high-quality fabrication of chalcogenide waveguides, facilitating the mass production and application of chalcogenide waveguides.

[0065] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A high Brillouin gain inverted ridge chalcogenide waveguide with air gaps, comprising a substrate layer and a waveguide layer disposed on the substrate layer, characterized in that, The lower surface of the waveguide layer protrudes outward to form a ridge, and the ridge of the waveguide layer is embedded in the substrate layer to form an inverted ridge waveguide structure, wherein an air gap is provided inside the ridge of the waveguide layer. The substrate layer is made of silicon dioxide, and the waveguide layer is made of arsenic sulfide; The substrate layer has a groove structure at its center, the size of which is adapted to the ridge portion, and the ridge portion of the waveguide layer is embedded in the groove structure; The waveguide layer has a thickness of 250-600 nm, a ridge height of 900-950 nm, a ridge width of 900-950 nm, and an air gap width of 4-20 nm. The air gap is located at the center of the ridge section.

2. A method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps as described in claim 1, characterized in that, Includes the following steps: S1, a substrate layer made of silicon dioxide; S2, a groove structure of a set size is etched in the center of the substrate layer using ICP etching method; S3, Arsenic sulfide is deposited on the substrate layer etched in step S2 using a thermal evaporation method to form an arsenic sulfide thin film layer of a set thickness; S4. Using a hot stamping method, the arsenic sulfide thin film obtained in step S3 is laminated flat to form a waveguide layer with an inverted ridge. S5, ICP etching is used again to etch air gaps of a set width in the ridge of the flat waveguide layer. S6. Then, arsenic sulfide is deposited on the surface of the waveguide layer etched in step S5 using a thermal evaporation method to seal the opening of the air gap and form a sealed air gap inside the ridge section.

3. The method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps according to claim 2, characterized in that, In step S2, the reaction gas for the ICP etching method is a mixture of CHF3 and Ar, with a gas flow ratio of 30 sccm / 20 sccm and an etching power of 240 W. In step S5, the reaction gas for the ICP etching method is a mixture of CF4 and CHF3, with a gas flow ratio of 30 sccm / 10 sccm and an etching power of 260 W.

4. The method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps according to claim 2, characterized in that, In step S3, before deposition using the thermal evaporation method, the substrate layer is treated sequentially with acetone, methanol, and isopropanol, then rinsed with distilled water, and finally dried with a hot plate at 110 °C; the vacuum chamber of the coating machine is evacuated to 6 × 10⁻⁶. -4 After Pa, the coating process begins, with the coating rate controlled at 20-25 nm / min. The coating is removed 60 min after the coating process begins.

5. The method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps according to claim 2, characterized in that, In step S4, the hot embossing temperature is 250°C and the air pressure is 3×10⁻⁶. 5 Pa, imprinting time is 30s.

6. The method for fabricating a high Brillouin gain inverted ridge chalcogenide waveguide with air gaps according to claim 2, characterized in that, In step S6, before deposition using the thermal evaporation method, the waveguide layer is first rinsed with distilled water and then dried with a hot plate at 105°C; the vacuum chamber of the coating machine is evacuated to 5×10⁻⁶. -4 After Pa, the coating process begins, with the coating rate controlled at 10-15 nm / min. The coating is removed 20 minutes after the coating process begins.

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