Periodic dielectric waveguide-based crossed transmission system and design method thereof

Abstract

The invention discloses a crossed transmission system based on a periodic dielectric waveguide. The crossed transmission system comprises a transmission waveguide unit and a gradient resonant cavity unit, the transmission waveguide units are arranged in a cross mode, and the gradual change type resonant cavity units are distributed and arranged outwards with the cross center of the transmission waveguide as a starting point. According to the crossed transmission structure based on the periodic dielectric waveguide, aiming at the requirement of high integration level of the modern photon technology, a compact periodic cylindrical waveguide structure is adopted to construct a crossed unit, and additional cylinders with different radiuses are added to form a gradually-changed resonant cavity structure; the special structure of the resonant cavity enables the optical signal to present the characteristic of high localization in the cross area, the optical signal is well constrained and guided, the interaction between the optical signal and the surrounding environment is reduced, and the overall transmission loss and crosstalk effect are reduced. The invention provides a new direction for the development of optical integrated circuits, and has the potential to realize higher performance and wider application in the fields of optical communication, optical storage and the like.

Description

Technical Field

[0001] The present invention belongs to the field of optical communication, and particularly relates to a cross-type transmission system based on a periodic dielectric waveguide and a design method thereof. Background Art

[0002] With the rapid development of information technology, high-speed, large-capacity, and low-loss optical communication systems and optical integrated circuits have become indispensable infrastructure in modern society. As one of the important components of optical integrated circuits, the cross-waveguide structure undertakes the important task of realizing the cross-connection and routing functions of optical signals, is the basis for realizing complex optical paths and multi-channel transmission, and is also one of the problems that need to be solved in current optical wiring solutions. However, the traditional SOI cross-waveguide structure has serious loss and crosstalk problems. This is because when optical signals pass through the crossing, phenomena such as mode overlap, mode coupling, and scattering occur, resulting in energy loss and signal attenuation, thereby limiting the performance and reliability of the optical path.

[0003] For the cross-waveguide structure, the scattering loss at the crossing is related to the degree of refractive index change of the waveguide material. Currently proposed solutions include changing the waveguide size at the crossing, building a bridge structure, using a diffraction grating structure, and using a "metamaterial" structure for refractive index matching. However, these all have their applicable situations and are also limited by factors such as cost and process feasibility. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a cross-type transmission system based on a periodic dielectric waveguide and a design method thereof.

[0005] The specific technical solution for achieving the purpose of the present invention is as follows:

[0006] A cross-type transmission system based on a periodic dielectric waveguide includes a transmission waveguide unit and a tapered resonant cavity unit;

[0007] The transmission waveguide unit is arranged in a cross shape, and the tapered resonant cavity unit is distributed outward starting from the crossing center of the transmission waveguide;

[0008] The transmission waveguide is used to transmit optical signals on the cross path, and the tapered resonant cavity unit is used to reduce the abrupt change of the refractive index of the material at the crossing and reduce the scattering loss.

[0009] Further, the transmission waveguide unit includes a cylindrical transmission waveguide and a connecting waveguide;

[0010] The multiple cylindrical transmission waveguides are arranged in a cross shape, and the connecting waveguide is used to connect with an external waveguide and is respectively arranged at the outermost ends of the "plus" sign.

[0011] Furthermore, the connecting waveguide includes a front-end straight waveguide structure and a rear-end semi-cylindrical waveguide structure;

[0012] The front-end straight waveguide structure is connected to the rear-end semi-cylindrical waveguide structure. The rear-end semi-cylindrical waveguide structure is arranged towards the direction of the cylindrical transmission waveguide, and the front-end straight waveguide structure is arranged towards the direction of the external waveguide.

[0013] Furthermore, the tapered resonant cavity unit includes N×N cylindrically waveguides distributed in an array;

[0014] The cylindrically waveguides are arranged in an array centered on the cross-shaped intersection center of the transmission waveguide unit, and the radius of the cylindrically waveguides decreases from the center to the edge;

[0015] The array center of the tapered resonant cavity unit overlaps with the intersection center of the transmission waveguide unit.

[0016] Furthermore, the transmission waveguide unit and the tapered resonant cavity unit are made of silicon.

[0017] Furthermore, the period length of the cylindrical transmission waveguide is set to be 0.13 to 0.16 times the wavelength, and the radius is set to be 0.46 to 0.56 times the period length;

[0018] The radius of the central cylindrically waveguide of the tapered resonant cavity unit is set to be 0.1 to 0.14 times the wavelength, the radius of the outer cylindrically waveguide of the central cylindrically waveguide is set to be 0.025 - 0.045 times the wavelength, and decreases outward in steps of 0.006 - 0.007 times the wavelength in turn.

[0019] The present invention also provides a design method for the system according to any one of the above, including the following steps:

[0020] Step 1: Design a cross-arranged transmission waveguide unit, including a connecting waveguide for connecting to an external waveguide and a cross-shaped cylindrical transmission waveguide for optical transmission; the front end of the connecting waveguide is a straight waveguide structure, and the rear end is a semi-cylindrical waveguide structure;

[0021] By changing the radius, spacing of the cylindrical transmission waveguide, and the width of the connecting waveguide, determine the parameter scheme with the highest transmission efficiency;

[0022] Step 2: Design a tapered resonant cavity unit based on cross-shaped periodic cylindrical waveguides. The tapered resonant cavity unit adds a resonant cavity composed of an array waveguide structure outward from the cross center of the cylindrical transmission waveguide. By changing the radius of each array waveguide structure constituting the tapered resonant cavity unit, determine the parameter scheme with the highest transmission efficiency and the lowest crosstalk.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The cross - type transmission structure based on the periodic dielectric waveguide provided by the solution of the present invention aims at the high integration requirements of modern photonics technology. It uses a compact periodic cylindrical waveguide structure to construct the cross - unit, and forms a tapered resonant cavity structure by adding additional cylinders with different radii;

[0025] The special structure of the resonant cavity enables the optical signal to exhibit highly localized characteristics in the cross - region, obtaining good confinement and guiding, reducing the interaction between the optical signal and the surrounding environment, thereby reducing the overall transmission loss and crosstalk effect. It provides a new direction for the development of optical integrated circuits and has the potential to achieve higher performance and wider applications in the fields of optical communication, optical storage, etc.

[0026] The following further illustrates the present invention in conjunction with specific embodiments. Brief Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the cross - type transmission system structure based on the periodic dielectric waveguide in the embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram of the cylindrical transmission waveguide in the embodiment of the present invention.

[0029] Figure 3 It is a schematic diagram of the connecting waveguide in the embodiment of the present invention.

[0030] Figure 4 It is a simulation result diagram in the embodiment of the present invention.

[0031] Figure 5 It is an imitated electric field distribution diagram in the embodiment of the present invention. Detailed Embodiments

[0032] The periodic dielectric waveguide (PDWG) is a special waveguide structure. Similar to photonic crystals, the periodic dielectric waveguide has a photonic bandgap, and electromagnetic waves of any frequency within the bandgap cannot be transmitted in the structure. Therefore, the propagation characteristics of PDWG are wavelength - dependent. The periodic dielectric waveguide is usually composed of a linear array of cylinders / holes for constructing the optical channel, and each cylinder / hole can be regarded as a high - quality coupled resonator. The optical power can be continuously coupled from one cylinder / hole to the next, thereby realizing the continuous transmission of light waves. Due to the discontinuity of its structure, when two PDWGs form a cross - structure, the jumping of light at the cross - point greatly reduces the coupling effect. Moreover, the cross - structure based on the periodic dielectric waveguide can provide a more flexible and adjustable optical path connection method to meet the requirements of complex optical path layouts in optical devices.

[0033] Based on this, the present invention provides a cross-type transmission system based on a periodic dielectric waveguide, including a transmission waveguide unit 1 and a tapered resonant cavity unit 2;

[0034] The transmission waveguide unit 1 is arranged in a cross-shaped intersection, and the tapered resonant cavity unit 2 is distributed outward starting from the intersection center of the transmission waveguide 1;

[0035] The transmission waveguide 1 is used to transmit optical signals on the cross path, and the tapered resonant cavity unit 2 is used to reduce the sudden change of the refractive index of the material at the intersection and reduce scattering loss.

[0036] Further, the transmission waveguide unit 1 includes a cylindrical transmission waveguide 3 and a connecting waveguide 4;

[0037] The plurality of cylindrical transmission waveguides 3 are arranged in a cross-shaped intersection, and the connecting waveguide 4 is used to connect with an external waveguide and is respectively arranged at the outermost ends of the "cross".

[0038] Further, the connecting waveguide 4 includes a front-end straight waveguide structure 5 and a rear-end semi-cylindrical waveguide structure 6;

[0039] The front-end straight waveguide structure 5 and the rear-end semi-cylindrical waveguide structure 6 are connected, and the rear-end semi-cylindrical waveguide structure 6 is arranged towards the direction of the cylindrical transmission waveguide 3, and the front-end straight waveguide structure 5 is arranged towards the direction of the external waveguide.

[0040] Further, the tapered resonant cavity unit 2 includes N×N cylindrically waveguides arranged in an array;

[0041] The cylindrically waveguides are arranged in an array centered on the cross-shaped intersection center of the transmission waveguide unit 1, and the radius of the cylindrically waveguides decreases from the center to the edge;

[0042] The array center of the tapered resonant cavity unit 2 overlaps with the intersection center of the transmission waveguide unit 1.

[0043] Further, the transmission waveguide unit 1 and the tapered resonant cavity unit 2 are made of silicon with a refractive index of 3.48.

[0044] Further, the period length of the cylindrical transmission waveguide 3 is set to be 0.13 to 0.16 times the wavelength, and the radius is set to be 0.46 to 0.56 period lengths;

[0045] The radius of the central cylindrically waveguide of the tapered resonant cavity unit 2 is set to be 0.1 to 0.14 times the wavelength, the radius of the outer cylindrically waveguide of the central cylindrically waveguide is set to be 0.025 - 0.045 times the wavelength, and decreases outward in steps of 0.006 - 0.007 times the wavelength in turn.

[0046] The present invention also provides a design method for the system according to any one of the above, including the following steps:

[0047] Step 1: Design the transmission waveguide unit 1 with a cross arrangement, including a connection waveguide 4 for connecting to an external waveguide and a cross-shaped cylindrical transmission waveguide 3 for optical transmission; the front end of the connection waveguide 4 is a straight waveguide structure, and the rear end is a semi-cylindrical waveguide structure;

[0048] By changing the radius, spacing of the cylindrical transmission waveguide 3, and the width of the connection waveguide 4, determine the parameter scheme with the highest transmission efficiency, specifically:

[0049] Determine the width of the connection waveguide 4, and use this width as the diameter of the semi-cylindrical waveguide at the rear end in the connection waveguide 4;

[0050] Refer to the bandgap law of one-dimensional periodic dielectric waveguides under specific parameters, and calculate the transmission efficiency and crosstalk magnitude of the crossed cylindrical transmission waveguide 3 under different parameters through electromagnetic simulation software to determine the radius of the cylindrical transmission waveguide 3 and the distance between two adjacent cylindrical transmission waveguides 3;

[0051] Design a cross-shaped transmission structure based on periodic dielectric waveguides according to the above parameters, cross-place two transmission waveguides with exactly the same parameters so that the central cylinders of the two waveguides coincide, and then remove the centrally coincident cylinder.

[0052] Step 2: Design a tapered resonant cavity unit 2 based on the cross-shaped periodic cylindrical waveguide. The tapered resonant cavity unit 2 adds a resonant cavity composed of an array waveguide structure outward from the cross center of the cylindrical transmission waveguide 3. By changing the radius of each array waveguide structure that makes up the tapered resonant cavity unit 2, determine the parameter scheme with the highest transmission efficiency and the lowest crosstalk, specifically:

[0053] Determine the position of the tapered resonant cavity unit 2 according to the cross-shaped transmission waveguide unit 1;

[0054] Refer to the bandgap of the photonic crystal resonant cavity under specific parameters to determine the radius of the first-layer cylindrical waveguide of the tapered resonant cavity unit 2, that is, the cylindrical waveguide at the cross center, and make fine adjustments to the cylinder radius by observing its transmission efficiency curve;

[0055] Determine the radius parameter of the outer-layer resonant cavity cylinder by the above method of determining the radius of each layer of the resonant cavity cylinder, and make fine adjustments to the cylinder radius by observing its transmission efficiency curve, and so on until the cylinder radius with the highest optical transmission efficiency is determined.

[0056] Embodiment

[0057] Combine Figures 1 to 3, A cross-type transmission system based on a periodic dielectric waveguide, comprising a transmission waveguide unit 1 and a tapered resonant cavity unit 2;

[0058] The transmission waveguide unit 1 is arranged in a cross-shaped intersection, and the tapered resonant cavity unit 2 is distributed outward starting from the intersection center of the transmission waveguide 1;

[0059] The transmission waveguide 1 is used to transmit optical signals in the cross path, and the tapered resonant cavity unit 2 is used to reduce the abrupt change of the refractive index of the material at the intersection and reduce scattering loss.

[0060] The transmission waveguide unit 1 includes a cylindrical transmission waveguide 3 and a connecting waveguide 4;

[0061] The plurality of cylindrical transmission waveguides 3 are arranged in a cross-shaped intersection, and the connecting waveguide 4 is used to connect with an external waveguide and is respectively arranged at the outermost ends of the "cross".

[0062] The connecting waveguide 4 includes a front-end straight waveguide structure 5 and a rear-end semi-cylindrical waveguide structure 6;

[0063] The front-end straight waveguide structure 5 and the rear-end semi-cylindrical waveguide structure 6 are connected, and the rear-end semi-cylindrical waveguide structure 6 is arranged towards the direction of the cylindrical transmission waveguide 3, and the front-end straight waveguide structure 5 is arranged towards the direction of the external waveguide.

[0064] The tapered resonant cavity unit 2 includes N×N cylindrically waveguides arranged in an array. In this embodiment, the tapered resonant cavity unit 2 is composed of 7×7 cylindrically waveguide structures arranged in an array

[0065] The cylindrically waveguides are arranged in an array centered on the cross-shaped intersection center of the transmission waveguide unit 1, and the radius of the cylindrically waveguides decreases from the center to the edge;

[0066] The array center of the tapered resonant cavity unit 2 overlaps with the intersection center of the transmission waveguide unit 1.

[0067] In this embodiment, the cross-shaped periodic cylindrical transmission waveguide 3 for optical transmission is composed of 29 cylindrical waveguides, the working wavelength is 1.55 μm, the period length a of all cylindrical arrays of this structure is 0.23 μm, the cylindrical radius r of the cross-shaped transmission waveguide is 0.115 μm, and the width of the input and output straight waveguides is the diameter of the cross-shaped transmission waveguide, and the length is two period lengths.

[0068] The tapered resonant cavity unit 2 has a total of 4 layers, and the number of cylinders in each layer is 1×1, 3×3, 5×5, 7×7 respectively, and the cylinder center is consistent with the cross transmission waveguide center of the row and column where it is located;

[0069] Among them, the 1×1 layer is the center position of the crossed waveguide. If the cylinders in the remaining layers coincide with the crossed transmission waveguide, they will not be arranged additionally; the radius of the resonator cylinder decreases with the increase of the layer number, which are R0 = 0.18 μm, R1 = 0.06 μm, R2 = 0.05 μm, and R3 = 0.04 μm respectively. The main purpose of this resonator structure with gradually decreasing cylinder radius is to introduce a gradually enhanced optical field localization effect in the resonator, reduce the abrupt change of the refractive index of the structure at the crossing center, thereby effectively solving the problem that the energy stored in the cavity fails to be coupled into the waveguide in time and reducing the scattering loss.

[0070] In this embodiment, FDTD Solutions is applied for simulation to obtain the transmission results of this structure; the periodic dielectric waveguide has polarization dependence. The TE-mode photonic bandgap of the hole array structure is more likely to appear, while the columnar periodic dielectric waveguide is more likely to form the TM-mode photonic bandgap. The results in the TM fundamental mode are adopted in this example, and the electric field direction is perpendicular to the propagation direction.

[0071] In this embodiment, several monitors are placed in the light propagation direction, the vertical direction, and the central plane. Among them, the monitoring situation P o / P i at the end of the straight waveguide in the output waveguide is used as the result of the transmission efficiency, and the monitoring situation P c / P i at the end of the straight waveguide in the vertical direction is used as the crosstalk result;

[0072] Figure 4 In, a is the transmission efficiency and crosstalk curves of the entire crossed structure unit under different radius conditions when there is only a cylinder at the crossing center, b is the transmission efficiency and crosstalk curves of the entire crossed structure unit under different radius conditions of the cylinders in this layer when a 3×3 array is expanded outward after the radius of the central cylinder is determined, c is the transmission efficiency and crosstalk curves of the entire crossed structure unit under different radius conditions of the cylinders in this layer when a 5×5 array is expanded outward after the radius of the 3×3 array is determined, and d is the transmission efficiency and crosstalk curves of the entire crossed structure unit under different radius conditions of the cylinders in this layer when a 7×7 array is expanded outward after the radius of the 5×5 array is determined. It can be seen from Figure 5 that after adding the 7×7 gradient resonator structure, the transmission efficiency of the entire crossed structure reaches 92.5%, and the crosstalk is as low as -18 dB. Through the analysis of the optimization results of the radii of the cylinders in different layers of the resonator, increasing the number of layers of the resonator and changing the radius of the cylinders will affect the transmission efficiency and crosstalk of this waveguide structure.

[0073] Figure 5 shows the transmission electric field distribution of the TM fundamental mode of this structure under the above parameters. It can be seen that the transmitted light generates a localization effect in the resonator at the crossing part, and the transmission efficiency of this structure is relatively high and the crosstalk is relatively low.

[0074] The above-described embodiments merely represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A cross-type transmission system based on a periodic dielectric waveguide, characterized in that, It includes a transmission waveguide unit (1) and a tapered resonant cavity unit (2); The transmission waveguide unit (1) is arranged in a cross-shaped intersection, and the tapered resonant cavity unit (2) is distributed outward starting from the intersection center of the transmission waveguide (1); The transmission waveguide (1) is used to transmit optical signals on the cross path, and the tapered resonant cavity unit (2) is used to reduce the abrupt change of the refractive index of the material at the intersection and reduce scattering loss.

2. The cross-type transmission system based on a periodic dielectric waveguide according to claim 1, characterized in that, The transmission waveguide unit (1) includes a cylindrical transmission waveguide (3) and a connecting waveguide (4); The multiple cylindrical transmission waveguides (3) are arranged in a cross-shaped intersection, and the connecting waveguide (4) is used to connect with an external waveguide and is respectively arranged at the outermost ends of the "plus" sign.

3. The cross-type transmission system based on a periodic dielectric waveguide according to claim 2, wherein The connecting waveguide (4) includes a front-end straight waveguide structure (5) and a rear-end semi-cylindrical waveguide structure (6); The front-end straight waveguide structure (5) and the rear-end semi-cylindrical waveguide structure (6) are connected, and the rear-end semi-cylindrical waveguide structure (6) is arranged towards the direction of the cylindrical transmission waveguide (3), and the front-end straight waveguide structure (5) is arranged towards the direction of the external waveguide.

4. The cross-type transmission system based on a periodic dielectric waveguide according to claim 2, characterized in that The tapered resonant cavity unit (2) includes N×N cylindrically waveguides arranged in an array; The cylindrically waveguides are arranged in an array centered on the cross-shaped intersection center of the transmission waveguide unit (1), and the radius of the cylindrically waveguides decreases from the center to the edge; The array center of the tapered resonant cavity unit (2) overlaps with the intersection center of the transmission waveguide unit (1).

5. The cross-type transmission system based on a periodic dielectric waveguide according to claim 1, characterized in that, The transmission waveguide unit (1) and the tapered resonant cavity unit (2) are made of silicon.

6. The cross-type transmission system based on a periodic dielectric waveguide according to claim 4, characterized in that The period length of the cylindrical transmission waveguide (3) is set to be 0.13 to 0.16 times the wavelength, and the radius is set to be 0.46 to 0.56 period lengths; The radius of the central cylindrical waveguide of the tapered resonant cavity unit (2) is set to be 0.1 to 0.14 times the wavelength, the radius of the outer cylindrical waveguide of the central cylindrical waveguide is set to be 0.025 - 0.045 times the wavelength, and decreases outward in steps of 0.006 - 0.007 times the wavelength in turn.

7. The design method of the system according to any one of claims 1-6, characterized in that It includes the following steps: Step 1: Design a transmission waveguide unit (1) arranged in a cross shape, including a connecting waveguide (4) for connecting with an external waveguide and a cross-shaped cylindrical transmission waveguide (3) for optical transmission; the front end of the connecting waveguide (4) is a straight waveguide structure, and the rear end is a semi-cylindrical waveguide structure; By changing the radius, spacing of the cylindrical transmission waveguide (3) and the width of the connecting waveguide (4), determine a parameter scheme with the highest transmission efficiency; Step 2: Design a tapered resonant cavity unit (2) based on cross-shaped periodic cylindrical waveguides. The tapered resonant cavity unit (2) adds a resonant cavity composed of an array waveguide structure outward from the intersection center of the cylindrical transmission waveguide (3). By changing the radius of each array waveguide structure constituting the tapered resonant cavity unit (2), determine a parameter scheme with the highest transmission efficiency and the lowest crosstalk.

8. The design method according to claim 7, characterized in that The specific content of Step 1 is: Determine the width of the connecting waveguide (4), and use this width as the diameter of the rear-end semi-cylindrical waveguide in the connecting waveguide (4); Refer to the bandgap law of a one-dimensional periodic dielectric waveguide, and calculate the transmission efficiency and crosstalk magnitude of the crossed cylindrical transmission waveguide (3) under different parameters through an electromagnetic simulation software to determine the radius of the cylindrical transmission waveguide (3) and the distance between two adjacent cylindrical transmission waveguides (3). Design a crossed transmission structure based on a periodic dielectric waveguide according to the above parameters. Place two transmission waveguides with exactly the same parameters in a crossed manner so that the central cylinders of the two waveguides coincide, and then remove the centrally coincident cylinder.

9. The design method according to claim 7, characterized in that, The specific content of step 2 is as follows: Determine the position of the tapered resonant cavity unit (2) according to the crossed transmission waveguide unit (1). Refer to the bandgap of a photonic crystal resonant cavity under specific parameters to determine the radius of the first-layer cylindrical waveguide of the tapered resonant cavity unit (2), that is, the radius of the cylindrical waveguide at the crossing center, and make fine adjustments to the cylinder radius by observing its transmission efficiency curve. Use the method of determining the radius of each layer of cylinders in the resonant cavity described above to determine the radius parameters of the cylinders in the outer layer of the resonant cavity, and make fine adjustments to the cylinder radius by observing its transmission efficiency curve, and so on until the cylinder radius with the highest light transmission efficiency is determined.

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