Nonvolatile reconfigurable mode converter and preparation method thereof

Abstract

The invention relates to a nonvolatile reconfigurable mode converter and a preparation method thereof. The mode converter comprises a first waveguide and a second waveguide, a plurality of phase change materials are deposited on the first waveguide and the second waveguide respectively, and the states of the phase change materials are controlled respectively to achieve conversion from a fundamental mode to different high-order modes. According to the invention, the conversion among a plurality of different modes can be realized only by using a single device, the utilization rate of the device is improved, the design and manufacturing cost of the device is obviously reduced, and the expandability is realized; the phase-change material has non-volatility, so that the power consumption of the device can be remarkably reduced; reconfigurability of the device is achieved through reversible phase change of the phase change material, and due to the fact that the refractive index contrast ratio between the crystalline state and the amorphous state of the phase change material is large, the size of the device can be remarkably reduced, and the integration level of a photon chip is improved.

Description

Technical Field

[0001] This invention belongs to the field of mode converter technology, and specifically relates to a non-volatile reconfigurable mode converter and its preparation method. Background Technology

[0002] To improve the data carrying capacity of optical communication and optical information processing, advanced multiplexing technologies have been explored, including wavelength division multiplexing (WDM), polarization division multiplexing (PDM), and mode division multiplexing (MDM). MDM utilizes the different spatial characteristic modes of multimode waveguides to simultaneously transmit multiple optical signals at the same wavelength, thus expanding transmission capacity. Compared to WDM, MDM significantly reduces the cost of on-chip multiplexed transmission systems. Mode converters are commonly used MDM devices. Existing mode converters are large in size and have limited bandwidth. More importantly, these devices lack reconfigurability; a single device can only perform one mode conversion, requiring multiple devices to achieve different mode conversions. Reconfigurable mode conversion can be achieved using thermo-optic or electro-optic effects, but both effects are volatile, requiring continuous power to maintain the device's state, significantly increasing power consumption. Therefore, there is a need to develop a non-volatile reconfigurable mode converter that can achieve switching between multiple modes using only a single device and can significantly reduce the power consumption of the device. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a non-volatile reconfigurable mode converter and its fabrication method, which can realize the conversion between multiple different modes with only a single device, improve the utilization rate of the device, and significantly reduce the design and manufacturing cost of the device; it is non-volatile, which can greatly reduce the power consumption of the device; and it is scalable.

[0004] This invention provides a non-volatile reconfigurable mode converter, which includes a first waveguide and a second waveguide; the width of the first waveguide is not less than the minimum width corresponding to the highest-order mode that the waveguide needs to support in the dispersion curve; the width of the second waveguide is not less than the minimum width corresponding to the highest-order mode that the waveguide needs to support in the dispersion curve; both the first and second waveguides are deposited with multiple phase change materials, and the state of the phase change materials is controlled to realize the conversion from the fundamental mode to different higher-order modes.

[0005] Preferably, taking four phase change materials as an example, a first phase change material and a second phase change material are deposited on the first waveguide, and a third phase change material and a fourth phase change material are deposited on the second waveguide; the conversion method from the fundamental mode to different higher-order modes includes:

[0006] When the third phase change material is in an amorphous state, by setting the width of the first waveguide, the width of the second waveguide (the widths of the first and second waveguides are not less than the minimum width corresponding to the highest-order mode that each waveguide needs to support in the dispersion curve), the structural parameters of the third phase change material, the spacing between the first and second waveguides, and the coupling length, the fundamental mode in the first waveguide is coupled to the second waveguide. When the fourth phase change material is in an amorphous state, the fundamental mode in the second waveguide will not undergo mode conversion and will be output from the third port; when the fourth phase change material is in a crystalline state, the fundamental mode in the second waveguide will be converted to a first-order mode and will be output from the third port.

[0007] When the third phase change material is in a crystalline state, the fundamental mode in the first waveguide continues to propagate in the first waveguide after passing through the coupling region. When the first phase change material is in a crystalline state and the second phase change material is in an amorphous state, the fundamental mode is converted into a second-order mode and output from the second port. When both the first and second phase change materials are in a crystalline state, the fundamental mode is converted into a fourth-order mode and output from the second port.

[0008] Preferably, the materials of the first waveguide and the second waveguide include one or more of silicon, germanium, silicon nitride, silicon oxynitride, lithium niobate, and lithium tantalate.

[0009] Preferably, the phase change material includes one or more of Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3, Sb2S3, GeTe, and GeSe.

[0010] Preferably, the cross-sectional shape of the phase change material includes one or more of the following: rectangle, circle, ellipse, rhombus, and square, or a periodic or non-periodic micro-nano structure array composed of various shapes.

[0011] Preferably, the phase change material is deposited on the waveguide surface or deposited into waveguide grooves by etching grooves on the waveguide.

[0012] Preferably, the state of the phase change material is changed by optical or electrical excitation.

[0013] This invention provides a first method for fabricating a non-volatile reconfigurable mode converter, comprising the following steps:

[0014] The first and second waveguides are fabricated by photolithography and etching. Then, the cladding is deposited and the waveguides are smoothed to the waveguide surface by chemical mechanical polishing. The phase change material is deposited and patterned by photolithography and etching. Finally, the cladding is deposited again to obtain a non-volatile reconfigurable mode converter.

[0015] This invention provides a second method for fabricating a non-volatile reconfigurable mode converter, comprising the following steps:

[0016] The first and second waveguides are fabricated by photolithography and etching. Then, the cladding is deposited and the cladding is smoothed to the surface of the waveguide by chemical mechanical polishing. Photoresist is deposited and photolithography is performed. Phase change material is deposited and the photoresist is stripped off. Finally, the cladding is deposited again to obtain a non-volatile reconfigurable mode converter.

[0017] Beneficial effects

[0018] The mode converter proposed in this invention is reconfigurable, enabling the conversion between the fundamental mode and multiple higher-order modes using only a single device, thus improving device utilization and significantly reducing design and manufacturing costs. This invention utilizes the reversible phase transition of phase change materials (PCMs) to achieve device reconfigurability; PCMs are non-volatile, which greatly reduces the device's static power consumption. The proposed non-volatile reconfigurable mode converter is scalable; by adding PCM structures or directional couplers to the first and second waveguides, the conversion from the fundamental mode to higher-order modes can be achieved. Furthermore, the large refractive index contrast between the crystalline and amorphous states of PCMs significantly reduces device size and improves the integration density of photonic chips. The reversible and highly repeatable phase transition of PCMs enhances device stability. Particularly in large-scale optical networks, this invention can significantly reduce network size, lower power consumption, and improve network stability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the non-volatile reconfigurable mode converter of the present invention.

[0020] Figure 2 This is a schematic diagram of the first fabrication process of the non-volatile reconfigurable mode converter of the present invention.

[0021] Figure 3 This is a schematic diagram of the second fabrication process of the non-volatile reconfigurable mode converter of the present invention. Detailed Implementation

[0022] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0023] Example 1

[0024] This embodiment provides a non-volatile reconfigurable mode converter, which includes a first waveguide and a second waveguide. The width of the first waveguide is not less than the minimum width corresponding to the highest-order mode that the waveguide needs to support in the dispersion curve. The width of the second waveguide is not less than the minimum width corresponding to the highest-order mode that the waveguide needs to support in the dispersion curve. Both the first and second waveguides are deposited with multiple phase change materials, and the state of the phase change materials is controlled to achieve the conversion from the fundamental mode to different higher-order modes. Figure 1 As shown, the first waveguide deposits a first phase change material (PCM1) and a second phase change material (PCM2), and the second waveguide deposits a third phase change material (PCM3) and a fourth phase change material (PCM4); the conversion methods from the fundamental mode to different higher-order modes include:

[0025] When the third phase change material is in an amorphous state, by setting the widths of the first and second waveguides and the structural parameters of the third phase change material, the fundamental mode in the first waveguide and the fundamental mode in the second waveguide satisfy the phase matching condition. The spacing between the first and second waveguides is determined according to the process conditions, and then the coupling length is calculated, so that the fundamental mode in the first waveguide is coupled into the second waveguide. When the fourth phase change material is in an amorphous state, the fundamental mode in the second waveguide does not undergo mode conversion and is output from the third port. When the fourth phase change material is in a crystalline state, the fundamental mode in the second waveguide is converted into a first-order mode and is output from the third port.

[0026] When the third phase change material is in a crystalline state, the fundamental mode in the first waveguide and the fundamental mode in the second waveguide no longer satisfy the phase matching condition. The fundamental mode in the first waveguide continues to propagate in the first waveguide after passing through the coupling region. When the first phase change material is in a crystalline state and the second phase change material is in an amorphous state, the fundamental mode is converted into a second-order mode and output from the second port. When both the first and second phase change materials are in a crystalline state, the fundamental mode is converted into a fourth-order mode and output from the second port.

[0027] Preferably, the materials of the first waveguide and the second waveguide include one or more of silicon, germanium, silicon nitride, silicon oxynitride, lithium niobate, and lithium tantalate.

[0028] Preferably, the phase change material includes one or more of Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3, Sb2S3, GeTe, and GeSe.

[0029] Preferably, the cross-sectional shape of the phase change material includes one or more of the following: rectangle, circle, ellipse, rhombus, and square, or a periodic or non-periodic micro-nano structure array composed of various shapes.

[0030] Preferably, the phase change material is deposited on the waveguide surface or deposited into waveguide grooves by etching grooves on the waveguide.

[0031] Preferably, the state of the phase change material is changed by optical or electrical excitation. The type of heater used for electrical excitation includes PIN heaters, silicon resistors, indium tin oxide (ITO), graphene, etc.

[0032] Depend on Figure 2 As shown, this embodiment provides a first method for fabricating a non-volatile reconfigurable mode converter, including the following steps:

[0033] The first and second waveguides are fabricated by photolithography and etching. Then, the cladding is deposited and the waveguides are smoothed to the waveguide surface by chemical mechanical polishing. The phase change material is deposited and patterned by photolithography and etching. Finally, the cladding is deposited again to obtain a non-volatile reconfigurable mode converter.

[0034] Depend on Figure 3 As shown, this embodiment provides a second method for fabricating a non-volatile reconfigurable mode converter, including the following steps:

[0035] The first and second waveguides are fabricated by photolithography and etching. Then, the cladding is deposited and the cladding is smoothed to the surface of the waveguide by chemical mechanical polishing. Photoresist is deposited and photolithography is performed. Phase change material is deposited and the photoresist is stripped off. Finally, the cladding is deposited again to obtain a non-volatile reconfigurable mode converter.

Claims

1. A non-volatile reconfigurable mode converter, characterized in that, The mode converter includes a first waveguide and a second waveguide; the width of the first waveguide is not less than the minimum width corresponding to the highest-order mode that the waveguide needs to support in the dispersion curve; the width of the second waveguide is not less than the minimum width corresponding to the highest-order mode that the waveguide needs to support in the dispersion curve; both the first waveguide and the second waveguide are deposited with multiple phase change materials, and the state of the phase change materials is controlled to realize the conversion from the fundamental mode to different higher-order modes.

2. The non-volatile reconfigurable mode converter according to claim 1, characterized in that, Taking four phase change materials as an example, the first and second phase change materials are deposited on the first waveguide, and the third and fourth phase change materials are deposited on the second waveguide; the conversion methods from the fundamental mode to different higher-order modes include: When the third phase change material is in an amorphous state, by setting the width of the first waveguide, the width of the second waveguide, the structural parameters of the third phase change material, the spacing between the first and second waveguides, and the coupling length, the fundamental mode in the first waveguide is coupled to the second waveguide. When the fourth phase change material is in an amorphous state, the fundamental mode in the second waveguide will not undergo mode conversion and will be output from the third port. When the fourth phase change material is in a crystalline state, the fundamental mode in the second waveguide will be converted to a first-order mode and output from the third port. When the third phase change material is in a crystalline state, the fundamental mode in the first waveguide continues to propagate in the first waveguide after passing through the coupling region. When the first phase change material is in a crystalline state and the second phase change material is in an amorphous state, the fundamental mode is converted into a second-order mode and output from the second port. When both the first and second phase change materials are in a crystalline state, the fundamental mode is converted into a fourth-order mode and output from the second port.

3. The non-volatile reconfigurable mode converter according to claim 1, characterized in that, The materials of the first waveguide and the second waveguide include one or more of silicon, germanium, silicon nitride, silicon oxynitride, lithium niobate, and lithium tantalate.

4. The non-volatile reconfigurable mode converter according to claim 1, characterized in that, The phase change material includes one or more of Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3, Sb2S3, GeTe, and GeSe.

5. The non-volatile reconfigurable mode converter according to claim 1, characterized in that, The cross-sectional shape of the phase change material includes one or more of the following: rectangle, circle, ellipse, rhombus, and square, or a periodic or non-periodic micro-nano structure array composed of various shapes.

6. The non-volatile reconfigurable mode converter according to claim 1, characterized in that, The phase change material is deposited on the waveguide surface or deposited into waveguide grooves by etching grooves on the waveguide.

7. The non-volatile reconfigurable mode converter according to claim 1, characterized in that, The state of the phase change material is changed by optical or electrical excitation.

8. A method for fabricating a non-volatile reconfigurable mode converter, characterized in that, Includes the following steps: The first and second waveguides are fabricated by photolithography and etching. Then, the cladding is deposited and the waveguides are smoothed to the waveguide surface by chemical mechanical polishing. The phase change material is deposited and patterned by photolithography and etching. Finally, the cladding is deposited again to obtain a non-volatile reconfigurable mode converter.

9. A method for fabricating a non-volatile reconfigurable mode converter, characterized in that, Includes the following steps: The first and second waveguides are fabricated by photolithography and etching. Then, the cladding is deposited and the cladding is smoothed to the surface of the waveguide by chemical mechanical polishing. Photoresist is deposited and photolithography is performed. Phase change material is deposited and the photoresist is stripped off. Finally, the cladding is deposited again to obtain a non-volatile reconfigurable mode converter.

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