Extensible 1*3 nonvolatile optical switch unit and nonvolatile programmable 1*2 multimode optical switch

Abstract

The invention relates to an extensible 1 * 3 non-volatile optical switch unit and a non-volatile programmable 1 * 2 multimode optical switch. The 1 * 3 optical switch unit comprises a bare silicon multi-mode bus waveguide and two PCM-Si single-mode hybrid waveguides, Sb2Se3 phase change materials with equal length and equal thickness are arranged on the upper and lower arm hybrid waveguides, and the two functions of light splitting and optical switching can be realized by regulating and controlling the states of the phase change materials of the two waveguides, namely a crystalline state (c-Sb2Se3) and an amorphous state (a-Sb2Se3); 1 * 3 optical switch units with different multi-mode bus waveguide widths can be cascaded into a 1 * 2 multi-mode optical switch supporting six modes by utilizing the heat insulation conical waveguide, and when the multi-mode bus waveguide and the PCM-Si mixed waveguide reach a phase matching condition, a corresponding high-order mode signal is converted into a fundamental mode signal for data transmission. The optical switch structure provided by the invention supports multiplexing and exchange of multiple mode signals, and has the advantages of adjustable switch dynamic state, zero static power consumption, low insertion loss and low crosstalk.

Description

Technical Field

[0001] The present invention belongs to the technical field of photon signal processing, and in particular relates to an expandable 1×3 non-volatile optical switch unit and a non-volatile programmable 1×2 multi-mode optical switch supporting six-mode multiplexing. Background Art

[0002] The statements in this section only provide background information related to the present disclosure, and these statements may constitute prior art. In the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art.

[0003] With its significant advantages of large bandwidth, high-speed transmission, excellent CMOS compatibility and high-density integration, silicon-based optical interconnect technology provides a promising solution to meet the growing demand for data traffic. In order to expand the capacity of on-chip optical links, researchers have conducted in-depth research on technologies such as wavelength division multiplexing (WDM), mode multiplexing (MDM) and polarization multiplexing (PDM). Given the constraints of the Shannon limit and the bandwidth limitations of erbium-doped fiber amplifiers, WDM technology is encountering a severe capacity bottleneck. To overcome these challenges, MDM has attracted much attention as a viable alternative. MDM treats each spatial mode as an independent channel and significantly improves the link capacity by multiplexing orthogonal modes onto a single wavelength carrier. Integrating spatial mode parallelism into photonic integrated circuits (PICs) is expected to expand the capabilities of existing optical communication systems.

[0004] Recent advances in MDM systems have led to the development of some passive modal switches that utilize a range of structures, including multimode interferometers, waveguide crossings, curved waveguides, grating couplers, Y-junctions, adiabatic couplers, and nanophotonic structures optimized by computational methods. However, the basis for expanding MDM networks is the ability to dynamically switch channels between these structures and precisely control the propagation of specific modes. Currently, the reported dynamic mode switches, including those based on Mach-Zehnder interferometers (MZIs), microring resonators (MRRs), MMIs, and Y-junctions, mainly rely on thermo-optic, electro-optic, or all-optical effects due to their relative simplicity and low cost. However, the refractive index changes induced by these effects are quite small (Δn<0.01), resulting in device sizes that are typically hundreds of microns, limiting their scalability. In addition, the switches implemented are unstable and require continuous power supply to maintain the switching state, which inevitably leads to high power consumption.

[0005] For example, the patent application number 202311695651.2 is titled "A non-volatile optical switch unit and an optical switching network composed thereof", which is a non-volatile non-blocking optical switch based on Mach-Zehnder interferometer and phase change material. The structure involved in the invention is as follows: First, a non-volatile phase change material Sb2Se3 and MZI are used to form a non-volatile optical switch unit. The phase shift value is changed by switching the state of the phase change material, thereby controlling the state of the switch. In addition, based on the above optical switch unit, 2 n ×2 n Benes topology non-blocking optical switching network. However, this design does not consider improving the refractive index contrast between the two states of the phase change material, shortening the length of the coupling region, and mode (de)multiplexing, and has the following defects:

[0006] 1. The insertion loss is high, which affects the transmission quality of the signal.

[0007] This patent interconnects 2×2 optical switch units into 8×8 non-volatile non-blocking optical switches based on Benes topology. Although this structure can achieve non-blocking data transmission, the switch is composed of 20 2×2 optical switch units based on Mach-Zehnder interferometers and non-volatile phase change materials and 16 cross waveguides. The use of too many components will inevitably cause higher insertion loss and affect the transmission quality of the signal. In addition, the design of cross waveguides must be considered to reduce insertion loss.

[0008] 2. The effective refractive index contrast is low, and the upper and lower arm signals cannot be separated well.

[0009] Although the 8×8 non-volatile non-blocking optical switch uses Sb2Se3 phase change material to achieve non-volatile characteristics and reduce energy consumption, its thickness is 25nm. Figure 1 It can be deduced that its effective refractive index contrast is only between 0.045-0.161. It is usually necessary to set the width of the waveguide very finely so as to achieve phase matching with the hybrid waveguide embedded with the amorphous state, so that the signal can be completely output from the port on the amorphous side.

[0010] 3. If you want to transmit more data, you need to expand to a larger optical switch and more components.

[0011] The waveguide of the 8×8 non-volatile non-blocking optical switch is only a single-mode waveguide, and each port can only transmit one data at a time. If more data is to be transmitted, it needs to be expanded to a larger optical switch, which requires more components. Summary of the invention

[0012] In view of the above problems, the object of the present invention is to solve part of the problems in the prior art, or at least alleviate these problems.

[0013] An expandable 1×3 non-volatile optical switch unit comprises a multimode bus waveguide located in the middle and an upper arm PCM-Si single-mode hybrid waveguide and a lower arm PCM-Si single-mode hybrid waveguide respectively arranged on both sides of the multimode bus waveguide; the upper arm PCM-Si single-mode hybrid waveguide and the lower arm PCM-Si single-mode hybrid waveguide are provided with phase change material Sb2Se3 films of equal length and thickness, and the Sb2Se3 films on the upper and lower arm PCM-Si single-mode hybrid waveguides can be switched between a crystalline state (c-Sb2Se3) and an amorphous state (a-Sb2Se3); the multimode bus waveguide and the PCM-Si single-mode hybrid waveguide containing a-Sb2Se3 can achieve a phase matching condition to convert a high-order mode signal input from an input end of the multimode bus waveguide into a fundamental mode signal for data transmission, while a mode signal that does not meet the phase matching condition continues to be transmitted forward, from O 12 Port output; the fundamental mode signal in the upper arm PCM-Si single-mode hybrid waveguide is output from O 11 The fundamental mode signal in the lower arm PCM-Si single-mode hybrid waveguide is output from O 13 Port output.

[0014] Optionally, the upper and lower arm PCM-Si single-mode hybrid waveguides can control the state of the Sb2Se3 film by laser pulse irradiation to achieve two different functions of light splitting and light switching.

[0015] Furthermore, the coupling region between the upper and lower arm PCM-Si single-mode hybrid waveguides and the multi-mode bus waveguide is composed of a PCM-Si hybrid waveguide of equal length to the coupling length; the PCM-Si hybrid waveguide in the coupling region is a 450nm wide and 220nm thick PCM-Si hybrid waveguide, including a Sb2Se3 thin film of the same width and 100nm thick and a silicon waveguide of the same width and 120nm thickness.

[0016] Furthermore, the width of the multimode bus waveguide is adjustable; the coupling gaps between the upper and lower arm PCM-Si hybrid waveguides and the middle multimode bus waveguide are both 0.1 um.

[0017] Furthermore, the phase change material Sb2Se3 is doped with GeTe.

[0018] A non-volatile programmable 1×2 multimode optical switch, using 6 of the expandable 1×3 non-volatile optical switch units, dividing the 1×2 multimode optical switch into six levels (including the first to sixth levels of multimode bus waveguides), from left to right, the number of modes supported by the multimode bus waveguide decreases by 1, and the two levels are connected by an adiabatic tapered waveguide to match two waveguides with different geometric cross-sectional parameters; the fundamental mode signals in the multiple upper arm PCM-Si single-mode hybrid waveguides are all output from the O1 port, and the fundamental mode signals in the multiple lower arm PCM-Si single-mode hybrid waveguides are all output from the O2 port.

[0019] Furthermore, the first-level multimode bus waveguide supports a total of 6 modes, namely: TE5, TE4, TE3, TE2, TE1, TE0; the second-level multimode bus waveguide supports a total of 5 modes, namely: TE4, TE3, TE2, TE1, TE0; the third-level multimode bus waveguide supports a total of 4 modes, namely: TE3, TE2, TE1, TE0; the fourth-level multimode bus waveguide supports a total of 3 modes, namely: TE2, TE1, TE0; the fifth-level multimode bus waveguide supports a total of 2 modes, namely: TE1, TE0; the sixth-level bus waveguide only supports 1 mode, namely: TE0.

[0020] Preferably, the widths of the first to sixth level multimode bus waveguides are 2.40μm, 1.99μm, 1.57μm, 1.17μm, 0.77μm, and 0.37μm, respectively, and the optimal coupling length and Sb2Se3 length are 13.7μm, 12.8μm, 11.4μm, 9.8μm, 8.0μm, and 5.3μm, respectively; the upper and lower floating ranges of the multimode bus waveguide width and coupling length are approximately 0.01μm and 0.02μm, respectively.

[0021] The present invention has the following beneficial effects:

[0022] 1. The scalable 1×3 non-volatile optical switch unit of the present invention selects Sb2Se3 with a width of 450nm and a thickness of 100nm and a silicon waveguide with the same width and thickness of 120nm to form a hybrid waveguide with a width of 450nm and a thickness of 220nm. Compared with the hybrid waveguide composed of Sb2Se3 with the same width of 20nm, 50nm, and 100nm thickness and a silicon waveguide with a thickness of 220nm, the effective refractive index contrast is increased by nearly 3-9 times, and has a larger refractive index contrast, which can better separate the upper and lower arm signals and achieve better optical switching. performance; and, the a-Sb2Se3 of the hybrid waveguide has the lowest refractive index value, and coupling with the amorphous Sb2Se3 can effectively reduce the width of the multimode bus waveguide, thereby reducing the area of ​​the multimode optical switch and improving the scalability of the optical switch; and, by using zero static power consumption, high refractive index contrast, non-volatile phase change material Sb2Se3, and doping it with GeTe and increasing the crystallization temperature, its thermal stability can be improved, so no additional power is needed to maintain the state of the switch, and the power consumption of the optical switch can be reduced;

[0023] 2. The present invention cascades the above-mentioned 6 expandable 1×3 non-volatile optical switch units to form a 1×2 multimode optical switch supporting six modes. By utilizing its non-volatility and the high contrast of complex refractive index between the crystalline and amorphous states and setting the optimal multimode waveguide width, coupling length and coupling gap, the TE0 fundamental mode signals in the 6 different modes and the upper and lower arm hybrid waveguides can achieve phase matching and efficient coupling, ensuring the optimal optical switching performance, and thus enabling the structure to achieve both splitting and optical switching functions; compared to the non-volatile non-blocking optical switch based on Mach-Zehnder interferometer and phase change material, the insertion loss of the six modes in the 1×2 multimode optical switch proposed by the present invention is less than or equal to 0.5dB within the C-band range. By reducing the insertion loss, the signal transmission quality is greatly improved. In addition, due to the combination of mode multiplexing technology, it is only necessary to design a suitable multimode bus waveguide width to support more high-order modes, so as to achieve parallel transmission of different modes, so as to facilitate parallel transmission of more data, thereby improving the capacity of the upper optical link;

[0024] 3. The present invention uses laser pulse irradiation to achieve rapid and reversible switching of Sb2Se3 between the crystalline state and the amorphous state, that is, the switching state can change rapidly;

[0025] 4. The optical switch structure proposed in the present invention supports the multiplexing and exchange of multiple mode signals, and has the advantages of adjustable switch dynamic state, zero static power consumption, low insertion loss and low crosstalk, and can realize flexible, dynamic and non-volatile switching of the optical switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A schematic diagram of the effective refractive index of a PCM-Si hybrid waveguide composed of phase change materials of different thicknesses and a silicon-based waveguide according to the present invention that varies with the waveguide width;

[0027] Figure 2 The present invention is a 1×3 optical switch unit based on phase change material; wherein Figure (a) is a schematic diagram of light splitting when the hybrid waveguides of the 1×3 optical switch unit are all a-Sb2Se3; Figure (b) is a schematic diagram of optical switching when the upper arm hybrid waveguide of the 1×3 optical switch unit is a-Sb2Se3 and the lower arm hybrid waveguide is c-Sb2Se3; Figure (c) is a schematic diagram of optical switching when the upper arm hybrid waveguide of the 1×3 optical switch unit is c-Sb2Se3 and the lower arm hybrid waveguide is a-Sb2Se3; Figure (d) is a schematic diagram of optical signal transmission when the hybrid waveguides of the 1×3 optical switch unit are all c-Sb2Se3;

[0028] Figure 3 It is a cross-sectional schematic diagram of a 1×3 optical switch unit of the present invention;

[0029] Figure 4 The 3dB optical power beam splitter based on mode multiplexing and phase change material of the present invention;

[0030] Figure 5 , Figure 6 , Figure 7 The present invention is a 1×2 multi-mode optical switch based on mode multiplexing and a combination of different phase change material states;

[0031] Figure 8 Schematic diagram of the effective refractive index of the eigenmode in a 220nm thick bare silicon waveguide calculated in the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings. The embodiments of the present invention are only used to illustrate the present invention rather than to limit the present invention. Without departing from the technical idea of ​​the present invention, various substitutions and changes can be made according to common technical knowledge and customary means in the field, which should all be included in the scope of the present invention.

[0033] The present invention is a patent application for an optical switch based on mode multiplexing and phase change materials, which aims to expand the capacity of on-chip optical links and enable flexible, dynamic and non-volatile switching of optical switches.

[0034] like Figure 2As shown in (a)-(d), an expandable 1×3 non-volatile optical switch unit includes a multimode bus waveguide located in the middle and an upper arm PCM-Si single-mode hybrid waveguide and a lower arm PCM-Si single-mode hybrid waveguide respectively arranged on both sides of the multimode bus waveguide; the upper arm PCM-Si single-mode hybrid waveguide and the lower arm PCM-Si single-mode hybrid waveguide are provided with phase change material Sb2Se3 films of equal length and thickness, and the Sb2Se3 films on the upper and lower arm PCM-Si single-mode hybrid waveguides can be switched between crystalline state (c-Sb2Se3) and amorphous state (a-Sb2Se3); the multimode bus waveguide and the PCM-Si single-mode hybrid waveguide containing a-Sb2Se3 achieve phase matching conditions to convert high-order mode signals input from the input end of the multimode bus waveguide into fundamental mode signals for data transmission, while the mode signals that do not meet the phase matching conditions continue to be transmitted forward, from O 12 Port output; the fundamental mode signal in the upper arm PCM-Si single-mode hybrid waveguide is output from O 11 The fundamental mode signal in the lower arm PCM-Si single-mode hybrid waveguide is output from O 13 Port output.

[0035] The multimode bus waveguide and the single-mode hybrid waveguide achieve the phase matching condition, that is, the effective refractive index value is equal, to realize the process of converting the high-order mode signal into the fundamental mode signal for data transmission. The mode signal that does not reach the phase matching condition will continue to transmit forward, where the upper arm hybrid waveguide and the lower arm hybrid waveguide are provided with Sb2Se3 films of equal length and thickness in the coupling region, such as Figure 3 As shown, the Sb2Se3 films on the two arm waveguides can switch between the crystalline state (c-Sb2Se3) and the amorphous state (a-Sb2Se3). The present application replaces the dynamic mode optical switch composed of the traditional MZI, MRR, MMI and Y-junction that rely on thermo-optical, electro-optical or all-optical effects with the non-volatile phase change material Sb2Se3 with zero static power consumption, high refractive index contrast. By forming a hybrid PCM-Si waveguide with Si waveguide and Sb2Se3, its effective refractive index contrast can be increased and the length of the coupling region can be reduced. Therefore, the present invention can reduce the area of ​​the multi-mode optical switch.

[0036] Correspondingly, by doping the phase change material Sb2Se3 with GeTe and increasing the crystallization temperature, its thermal stability can be improved, so no additional power is required to maintain the state of the switch, that is, the power consumption of the optical switch can be reduced.

[0037] like Figure 1 and Figure 3As shown, the coupling region between the upper and lower arm PCM-Si single-mode hybrid waveguides and the multi-mode bus waveguide is composed of a PCM-Si hybrid waveguide of equal length to the coupling length; the PCM-Si hybrid waveguide at the coupling region is a 450nm wide and 220nm thick PCM-Si hybrid waveguide, including a Sb2Se3 film of the same width and 100nm thick and a silicon waveguide of the same width and 120nm thickness. In the coupling region, the present invention selects Sb2Se3 with a width of 450nm and a thickness of 100nm and a silicon waveguide with the same width and thickness of 120nm to form a hybrid waveguide with a width of 450nm and a thickness of 220nm. Compared with the hybrid waveguide composed of Sb2Se3 with the same width and thickness of 20nm, 50nm, and 100nm and a silicon waveguide with a thickness of 220nm, the hybrid PCM-Si waveguide with the selected parameters has a larger refractive index contrast of about 0.42 at a waveguide width of 450nm, which can effectively shorten the length of the coupling region, while the refractive index contrasts of the other three are 0.045, 0.161, and 0.24, respectively. The effective refractive index contrast of the present invention is increased by nearly 3-9 times, which can better separate the upper and lower arm signals and achieve better optical switching performance. On the other hand, by Figure 1 It can be seen that the a-Sb2Se3 of the hybrid waveguide has the lowest refractive index value, so coupling with amorphous Sb2Se3 can effectively reduce the width of the multimode bus waveguide, thereby reducing the area of ​​the structure.

[0038] In the present invention, the upper and lower arm PCM-Si single-mode hybrid waveguides can control the state of the Sb2Se3 film by laser pulse irradiation to achieve two different functions of light splitting and optical switching. That is, when the Sb2Se3 films on the upper and lower arm hybrid waveguides are both a-Sb2Se3, the multimode bus waveguide simultaneously reaches phase matching conditions with the two PCM-Si single-mode hybrid waveguides, and the corresponding high-order mode signals are converted into two equal fundamental mode signals for data transmission. The upper and lower ports will each output half of the optical signal. At this time, the structure is a 3dB optical power splitter to achieve 3dB light splitting; when one of the Sb2Se3 films on the two arm waveguides is a-Sb2Se3 and the other is c-Sb2Se3, the multimode bus waveguide simultaneously reaches phase matching conditions with the two PCM-Si single-mode hybrid waveguides, and the corresponding high-order mode signals are converted into two equal fundamental mode signals for data transmission. The upper and lower ports will each output half of the optical signal. At this time, the structure is a 3dB optical power splitter to achieve 3dB light splitting; when one of the Sb2Se3 films on the two arm waveguides is a-Sb2Se3 and the other is c-Sb2Se3, Since the multimode bus waveguide and a-Sb2Se3 have similar effective refractive index values, the high-order mode optical signal carrying data will be completely converted into the fundamental mode signal in the single-mode hybrid waveguide on the amorphous side for output. At this time, the structure is a 1×2 optical switch to realize optical switching; when the Sb2Se3 films on the upper and lower arm hybrid waveguides are both c-Sb2Se3, the multimode bus waveguide and the two PCM-Si single-mode hybrid waveguides do not reach the phase matching condition. At this time, the optical signal carrying data will continue to move forward and be output from the through-port.

[0039] The specific working mode of the scalable 1×3 non-volatile optical switch unit is as follows Figure 2 As shown in (a)-(d).

[0040] like Figure 2 (a) shows the multimode bus waveguide input port I of the scalable 1×3 non-volatile optical switch unit. 11 Take the support of TE1 and TE0 modes as an example. When the Sb2Se3 films on the upper and lower arm hybrid waveguides are both a-Sb2Se3, the TE1 high-order mode signal in the multimode bus waveguide simultaneously reaches the phase matching condition with the TE0 fundamental mode signal in the two PCM-Si single-mode hybrid waveguides. At this time, the TE1 mode signal is converted into two equal TE0 mode signals, that is, half of the TE1 mode signal is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide from O 11 The other half is converted into the TE0 fundamental mode signal in the lower arm hybrid waveguide from O 13 port output, achieving 3dB splitting in TE1 mode, while I 11 The TE0 mode signal input from the port will continue to move forward because it does not reach the phase matching condition with the TE0 fundamental mode signal in the PCM-Si single-mode hybrid waveguide. 12 Port output;

[0041] like Figure 2 As shown in (b), when the Sb2Se3 film of the upper arm waveguide is a-Sb2Se3 and the Sb2Se3 film of the lower arm waveguide is c-Sb2Se3, at this time, the high-order mode signal in the multimode bus waveguide reaches the phase matching condition with the fundamental mode signal in the upper arm PCM-Si single-mode hybrid waveguide, and the TE1 mode signal is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide. 11 Port output, realize TE1 mode signal from O 11 The output of the port, I 11 The TE0 mode signal of the port still changes from 0 to 12 Port output;

[0042] like Figure 2 As shown in (c), when the Sb2Se3 film of the upper arm waveguide is c-Sb2Se3 and the Sb2Se3 film of the lower arm waveguide is a-Sb2Se3, at this time, the high-order mode signal in the multimode bus waveguide and the fundamental mode signal in the lower arm PCM-Si single-mode hybrid waveguide reach the phase matching condition, and the TE1 mode signal is completely converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide from O 13 Port output, realize TE1 mode signal from O 13 The output of the port, I 11 The TE0 mode signal of the port still changes from 0 to 12 Port output;

[0043] like Figure 2As shown in (d), when the Sb2Se3 films on the upper and lower arm hybrid waveguides are both c-Sb2Se3, the TE1 and TE0 mode signals in the multimode bus waveguide and the TE0 fundamental mode signals in the two PCM-Si single-mode hybrid waveguides all reach the phase matching condition. At this time, the TE1 and TE0 mode signals will continue to move forward from O 12 Port output.

[0044] The width of the multimode bus waveguide is adjustable to support different high-order modes; Figure 3 As shown, if the state of the phase change material is not considered, the structure is symmetrical, and the coupling gaps between the upper and lower arm PCM-Si hybrid waveguides and the middle multi-mode bus waveguide are both 0.1 um.

[0045] The multimode bus waveguide is a bare silicon multimode bus waveguide, such as Figure 3 shown.

[0046] The present invention also proposes a non-volatile programmable 1×2 multi-mode optical switch supporting six-mode multiplexing, such as Figure 4-7 As shown, 6 expandable 1×3 non-volatile optical switch units are used to divide the 1×2 multimode optical switch into six levels (including the first to sixth multimode bus waveguides). From left to right, the number of modes supported by the multimode bus waveguide is reduced by 1, and the two levels are connected by an adiabatic tapered waveguide to match the two waveguides with different geometric cross-sectional parameters to reduce energy loss; the fundamental mode signals in the multiple upper arm PCM-Si single-mode hybrid waveguides are all output from the O1 port, and the fundamental mode signals in the multiple lower arm PCM-Si single-mode hybrid waveguides are all output from the O2 port. Compared with the non-volatile non-blocking optical switch based on Mach-Zehnder interferometer and phase change material, the insertion loss of the six modes in the 1×2 multimode optical switch proposed by the present invention is less than or equal to 0.5dB within the C band. By reducing the insertion loss, the signal transmission quality is greatly improved. Moreover, due to the combination of mode multiplexing technology, it is only necessary to design a suitable multimode bus waveguide width to support more high-order modes, so as to achieve parallel transmission of different modes, so as to facilitate parallel transmission of more data, thereby improving the capacity of the optical link.

[0047] The optical switch structure proposed by the present invention supports multiplexing and switching of multiple mode signals, and has the advantages of adjustable switch dynamic state, zero static power consumption, low insertion loss and low crosstalk.

[0048] like Figure 4-7As shown, the mode signal is input from the input end of the first-level multimode centerline waveguide. The first-level multimode bus waveguide supports 6 modes, namely: TE5, TE4, TE3, TE2, TE1, TE0; since the TE5 mode signal in the first-level multimode bus waveguide is converted into the TE0 fundamental mode signal of the hybrid waveguide, the second-level multimode bus waveguide supports 5 modes, namely: TE4, TE3, TE2, TE1, TE0; since the TE4 mode signal in the second-level multimode bus waveguide is also converted into the TE0 fundamental mode signal of the hybrid waveguide, the third-level multimode bus waveguide supports 4 modes, namely: TE3, TE2, TE1, TE0; Similarly, since the TE3 mode in the third-level multimode bus waveguide is also converted into the TE0 fundamental mode signal of the hybrid waveguide, the fourth-level multimode bus waveguide supports a total of 3 modes, namely: TE2, TE1, and TE0; since the TE2 mode signal in the fourth-level multimode bus waveguide is converted into the TE0 fundamental mode signal of the hybrid waveguide, the fifth-level multimode bus waveguide supports a total of 2 modes, namely: TE1 and TE0; since the TE1 mode signal in the fifth-level multimode bus waveguide is also converted into the TE0 fundamental mode signal of the hybrid waveguide, the sixth-level bus waveguide only supports 1 mode, namely: TE0.

[0049] When the structure acts as a 3dB optical beam splitter, the first-level multimode bus waveguide and the two single-mode hybrid waveguides in the upper and lower arms reach phase matching conditions at the same time. At this time, the high-order mode signal is converted into two equal fundamental mode signals, namely, the TE5 mode signal is converted into two equal TE0 mode signals, half of the TE5 mode signal is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide and output from the upper port, and the other half is converted into the TE0 signal in the lower arm hybrid waveguide and output from the lower port, thereby realizing 3dB splitting of the TE5 mode; the same is true for the TE4 mode in the second-level multimode bus waveguide, the TE3 mode in the third-level multimode bus waveguide, the TE2 mode in the fourth-level multimode bus waveguide, the TE1 mode in the fifth-level multimode bus waveguide, and the TE0 mode in the sixth-level single-mode bus waveguide to achieve 3dB splitting.

[0050] When the structure acts as a 1×2 multimode optical switch, the first-level multimode bus waveguide and the waveguide on the side embedded with a-Sb2Se3 in the two hybrid waveguides reach a phase matching condition. At this time, the high-order mode signal is converted into the fundamental mode signal and is completely output from the waveguide port on the amorphous side, that is: when the Sb2Se3 of the upper arm waveguide is a-Sb2Se3, the TE5 mode signal is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide and is completely output from the upper port; when the Sb2Se3 of the lower arm waveguide is a-Sb2Se3, the TE5 mode signal is converted into the TE0 fundamental mode signal in the lower arm hybrid waveguide and is completely output from the lower port; the process of achieving arbitrary port output of the TE4 mode signal in the second-level multimode bus waveguide, the TE3 mode signal in the third-level multimode bus waveguide, the TE2 mode signal in the fourth-level multimode bus waveguide, the TE1 mode signal in the fifth-level multimode bus waveguide, and the TE0 mode signal in the sixth-level bus waveguide is the same.

[0051] The specific working mode of the non-volatile programmable 1×2 multi-mode optical switch is as follows Figures 4 to 7 shown.

[0052] like Figure 4 As shown, when the structure acts as a 3dB optical beam splitter:

[0053] First stage: The TE5 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the upper and lower arm hybrid waveguides reach phase matching conditions at the same time. At this time, the TE5 mode signal is converted into two equal TE0 fundamental mode signals, that is, half is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide and output from the O1 port, and the other half is converted into the TE0 fundamental mode signal in the lower arm hybrid waveguide and output from the O2 port, realizing 3dB splitting of the TE5 mode;

[0054] Second stage: The TE4 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the upper and lower arm hybrid waveguides reach the phase matching condition at the same time. At this time, the TE4 mode signal is converted into two equal TE0 fundamental mode signals, that is, half is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide and output from the O1 port, and the other half is converted into the TE0 fundamental mode signal in the lower arm hybrid waveguide and output from the O2 port, thus realizing 3dB splitting of the TE4 mode.

[0055] Level 3: The TE3 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the upper and lower arm hybrid waveguides reach the phase matching condition at the same time. At this time, the TE3 mode signal is converted into two equal TE0 fundamental mode signals, that is, half is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide and output from the O1 port, and the other half is converted into the TE0 fundamental mode signal in the lower arm hybrid waveguide and output from the O2 port, thus realizing 3dB splitting of the TE3 mode.

[0056] Level 4: The TE2 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the upper and lower arm hybrid waveguides reach the phase matching condition at the same time. At this time, the TE2 mode signal is converted into two equal TE0 fundamental mode signals, that is, half is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide and output from the O1 port, and the other half is converted into the TE0 fundamental mode signal in the lower arm hybrid waveguide and output from the O2 port, realizing 3dB splitting of the TE2 mode.

[0057] Level 5: The TE1 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the upper and lower arm hybrid waveguides reach the phase matching condition at the same time. At this time, the TE1 mode signal is converted into two equal TE0 fundamental mode signals, that is, half is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide and output from the O1 port, and the other half is converted into the TE0 fundamental mode signal in the lower arm hybrid waveguide and output from the O2 port, thus realizing 3dB splitting of the TE1 mode.

[0058] Level 6: The TE0 mode signal in the bus waveguide and the TE0 fundamental mode signals in the upper and lower arm hybrid waveguides reach the phase matching condition at the same time. At this time, the TE0 mode signal is converted into two equal TE0 fundamental mode signals, that is, half is converted into the TE0 fundamental mode signal in the upper arm hybrid waveguide and output from the O1 port, and the other half is converted into the TE0 fundamental mode signal in the lower arm hybrid waveguide and output from the O2 port, realizing 3dB splitting of the TE0 mode.

[0059] like Figure 5 As shown, when the structure acts as a 1×2 multimode optical switch:

[0060] First stage: The TE5 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the hybrid waveguide embedded with a-Sb2Se3 in the upper arm reach the phase matching condition. At this time, the TE5 mode signal is converted into the TE0 fundamental mode signal of the hybrid waveguide in the upper arm and is completely output from the O1 port;

[0061] Second stage: The TE4 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the hybrid waveguide embedded with a-Sb2Se3 in the lower arm reach the phase matching condition. At this time, the TE4 mode signal is converted into the TE0 fundamental mode signal of the hybrid waveguide in the lower arm and is completely output from the O2 port.

[0062] The third stage: the TE3 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the hybrid waveguide embedded with a-Sb2Se3 in the upper arm reach the phase matching condition. At this time, the TE3 mode signal is converted into the TE0 fundamental mode signal of the hybrid waveguide in the upper arm and is completely output from the O1 port.

[0063] Level 4: The TE2 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the hybrid waveguide embedded with a-Sb2Se3 in the upper arm reach the phase matching condition. At this time, the TE2 mode signal is converted into the TE0 fundamental mode signal of the hybrid waveguide in the upper arm and is completely output from the O1 port.

[0064] Level 5: The TE1 mode signal in the multimode bus waveguide and the TE0 fundamental mode signal in the hybrid waveguide embedded with a-Sb2Se3 in the lower arm reach the phase matching condition. At this time, the TE1 mode signal is converted into the TE0 fundamental mode signal of the hybrid waveguide in the lower arm and is completely output from the O2 port;

[0065] Level 6: The TE0 mode signal in the bus waveguide and the TE0 fundamental mode signal in the hybrid waveguide embedded with a-Sb2Se3 in the upper arm reach the phase matching condition. At this time, the TE0 mode signal is converted into the TE0 fundamental mode signal of the upper arm hybrid waveguide and is completely output from the O1 port.

[0066] Figure 6 , Figure 7 The working principle and Figure 2 (b) Figure 2 (c) and Figure 5 Consistent, due to Figure 6 The phase change material embedded in the upper hybrid waveguide of each 1×3 optical switch unit is a-Sb2Se3, and the lower hybrid waveguide is c-Sb2Se3, so the TE5, TE4, TE3, TE2, TE1, and TE0 mode signals are all output from the O1 port; Figure 7 The phase change material embedded in the upper arm hybrid waveguide of each level 1×3 optical switch unit is c-Sb2Se3, and the lower arm hybrid waveguide is a-Sb2Se3, so the TE5, TE4, TE3, TE2, TE1, and TE0 mode signals are all output from the O2 port.

[0067] The key to achieving optimal optical switching performance of the 1×2 multimode optical switch composed of 1×3 optical switch units of the present invention is that the multimode bus waveguide and the PCM-Si waveguides containing a-Sb2Se3 on both sides can achieve phase matching conditions, that is, the effective refractive index values ​​are equal to achieve the conversion of high-order mode signals to fundamental mode signals. Figure 5 As shown in the figure, the approximate waveguide width when the TE5-TE1 and the TE0 fundamental mode signal in the hybrid waveguide embedded with a-Sb2Se3 are coupled is marked. In this structure, the coupling gap between the fixed bus waveguide and the upper and lower arm hybrid waveguides is 0.1μm. Figure 5The results shown are scanned and optimized using the Ansys Lumerical simulation platform to obtain the specific parameter values ​​of the multimode bus waveguide width, coupling length and phase change material length to achieve the optimal optical switching performance. The multimode bus waveguide widths supporting TE5, TE4, TE3, TE2, TE1 and TE0 modes are 2.40μm, 1.99μm, 1.57μm, 1.17μm, 0.77μm and 0.37μm, respectively, and the optimal coupling lengths of these modes are the same as the Sb2Se3 lengths, which are 13.7μm, 12.8μm, 11.4μm, 9.8μm, 8.0μm and 5.3μm, respectively. Since the performance of optical switching can be changed by fine-tuning the bus waveguide width and coupling length, the upper and lower floating ranges of the bus waveguide width and coupling length to ensure the optimal optical switching performance are approximately 0.01μm and 0.02μm, respectively.

[0068] Table 1 summarizes the specific coupling length values, Sb2Se3 length values, coupling gap values, and bus waveguide width values ​​for the six different modes to achieve optimal optical switching conditions:

[0069] Table 1 1×2 multimode optical switch parameters

[0070]

[0071] The present invention uses Sb2Se3 with a width of 450nm and a thickness of 100nm and a silicon waveguide with the same width and thickness of 120nm to form a hybrid PCM-Si waveguide with a width of 450nm and a thickness of 220nm. Compared with the hybrid waveguide composed of Sb2Se3 with the same width and thickness of 20nm, 50nm, and 100nm and a silicon waveguide with a thickness of 220nm, the hybrid PCM-Si waveguide with the selected parameters has a larger refractive index contrast of about 0.42 at a waveguide width of 450nm, which can effectively shorten the length of the coupling region. In addition, combined with mode multiplexing, a 1×2 multimode optical switch supporting 6 modes is formed by cascading optical switch units embedded with phase change materials. The Ansys Lumerical simulation platform is used to scan and optimize the parameter values ​​such as TE width and coupling length. At a wavelength of 1550nm, the transmittance of each mode of the multimode optical switch at the corresponding output port is above 94%. By combining non-volatile phase change materials with mode multiplexing, dynamic non-volatile multimode optical switches can precisely control the transmission path of optical signals to ensure efficient and stable operation of the network. They can also be combined with other multiplexing methods to further expand on-chip link capacity to meet the growing bandwidth demand.

[0072] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An expandable 1×3 non-volatile optical switch unit, characterized in that: The invention comprises a multimode bus waveguide located in the middle and an upper arm PCM-Si single-mode hybrid waveguide and a lower arm PCM-Si single-mode hybrid waveguide respectively arranged on both sides of the multimode bus waveguide; the upper arm PCM-Si single-mode hybrid waveguide and the lower arm PCM-Si single-mode hybrid waveguide are provided with phase change material Sb2Se3 films of equal length and thickness, and the Sb2Se3 films on the upper and lower arm PCM-Si single-mode hybrid waveguides can be switched between crystalline state (c-Sb2Se3) and amorphous state (a-Sb2Se3); the multimode bus waveguide and the PCM-Si single-mode hybrid waveguide containing a-Sb2Se3 can achieve the conversion of the high-order mode signal inputted from the input end of the multimode bus waveguide into the fundamental mode signal for data transmission by reaching the phase matching condition, while the mode signal which does not reach the phase matching condition continues to be transmitted forward, from O 12 Port output; the fundamental mode signal in the upper arm PCM-Si single-mode hybrid waveguide is output from O 11 The fundamental mode signal in the lower arm PCM-Si single-mode hybrid waveguide is output from O 13 Port output.

2. The expandable 1×3 non-volatile optical switch unit according to claim 1, characterized in that: The upper and lower arm PCM-Si single-mode hybrid waveguide can control the state of the Sb2Se3 film by laser pulse irradiation to achieve two different functions of light splitting and light switching.

3. The expandable 1×3 non-volatile optical switch unit according to claim 1, characterized in that: The coupling region between the upper and lower arm PCM-Si single-mode hybrid waveguides and the multi-mode bus waveguide is composed of a PCM-Si hybrid waveguide of equal length to the coupling length; the PCM-Si hybrid waveguide in the coupling region is a 450nm wide and 220nm thick PCM-Si hybrid waveguide, including a Sb2Se3 thin film of the same width and 100nm thick and a silicon waveguide of the same width and 120nm thickness.

4. The expandable 1×3 non-volatile optical switch unit according to claim 1, characterized in that: The width of the multimode bus waveguide is adjustable; the coupling gaps between the upper and lower arm PCM-Si hybrid waveguides and the middle multimode bus waveguide are both 0.1 um.

5. The expandable 1×3 non-volatile optical switch unit according to claim 1, characterized in that: The phase change material Sb2Se3 is doped with GeTe.

6. A non-volatile programmable 1×2 multimode optical switch, characterized in that: Six expandable 1×3 non-volatile optical switch units as described in any one of claims 1 to 4 are used to divide the 1×2 multimode optical switch into six levels (including the first to sixth levels of multimode bus waveguides), from left to right, the number of modes supported by the multimode bus waveguide is reduced by 1, and the two levels are connected by an adiabatic conical waveguide to match two waveguides with different geometric cross-sectional parameters; the fundamental mode signals in the multiple upper arm PCM-Si single-mode hybrid waveguides are all output from the O1 port, and the fundamental mode signals in the multiple lower arm PCM-Si single-mode hybrid waveguides are all output from the O2 port.

7. The non-volatile programmable 1×2 multi-mode optical switch according to claim 6, characterized in that: The first-level multimode bus waveguide supports a total of 6 modes, namely: TE5, TE4, TE3, TE2, TE1, TE0; the second-level multimode bus waveguide supports a total of 5 modes, namely: TE4, TE3, TE2, TE1, TE0; the third-level multimode bus waveguide supports a total of 4 modes, namely: TE3, TE2, TE1, TE0; the fourth-level multimode bus waveguide supports a total of 3 modes, namely: TE2, TE1, TE0; the fifth-level multimode bus waveguide supports a total of 2 modes, namely: TE1, TE0; the sixth-level bus waveguide only supports 1 mode, namely: TE0.

8. The non-volatile programmable 1×2 multi-mode optical switch according to claim 7, characterized in that: The widths of the first to sixth level multimode bus waveguides are 2.40μm, 1.99μm, 1.57μm, 1.17μm, 0.77μm, and 0.37μm, respectively; the optimal coupling length and Sb2Se3 length are 13.7μm, 12.8μm, 11.4μm, 9.8μm, 8.0μm, and 5.3μm, respectively; the upper and lower floating ranges of the multimode bus waveguide width and coupling length are approximately 0.01μm and 0.02μm, respectively.

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