Wavelength division multiplexer and silicon optical chip

Abstract

The invention provides a wavelength division multiplexer and a silicon optical chip, the wavelength division multiplexer comprises a silicon waveguide layer, the silicon waveguide layer is provided with an input port and at least two output ports, input light is input from the input port, and the position of the output port is a first self-imaging position of the input light; the central axis of the input port and the long side of the silicon waveguide layer form a first included angle, the central axis of the output port and the long side of the silicon waveguide layer form a second included angle, the first included angle is smaller than 90 degrees, and the second included angle is smaller than 90 degrees; a first distance is arranged between the input port and the bottom edge of the silicon waveguide layer, the first distance is larger than zero, and the first distance is smaller than the cosine value obtained by subtracting the width of the input port from the width of the silicon waveguide layer and dividing the width of the input port by the first included angle; and a thermo-optical phase shifter is arranged above the silicon waveguide layer. The wavelength division multiplexer is applied to the silicon optical chip. The wavelength division multiplexer can reduce phase errors.

Description

Technical Field

[0001] The present invention relates to the technical field of wavelength division multiplexers, and in particular to a wavelength division multiplexer capable of reducing phase error. Background Art

[0002] In integrated photonics, wavelength division multiplexers (WDMs) can directly separate (demultiplex) or combine (multiplex) optical signals of different wavelengths by leveraging the physical properties of oblique-incidence multimode interferometers. Oblique incidence refers to the angle between the input light and the end face of the multimode waveguide being less than 90 degrees. Since oblique-incidence multimode interferometers are wavelength-sensitive, they can separate or combine multi-wavelength signals by exploiting the differences in imaging positions of different wavelengths.

[0003] Using an oblique-incidence multimode interferometer as a wavelength division multiplexer (WDM) offers a simpler structure, requiring only a single etching step to manufacture the device. However, this design has limitations. During the manufacturing process, due to limited photolithography or etching precision, errors can occur in the waveguide dimensions, which can cause the output spectrum to redshift or blueshift, that is, a drift in the center wavelength. When this structure is used in data communication or telecommunications optical modules, because the laser wavelength is fixed and specified by the communication standard, this drift in the center wavelength increases the loss of each data channel and aggravates crosstalk between channels, leading to an increase in the channel bit error rate, adversely affecting communication quality. Summary of the Invention

[0004] A first object of the present invention is to provide a wavelength division multiplexer that reduces phase error.

[0005] A second object of the present invention is to provide a silicon photonic chip using the above-mentioned wavelength division multiplexer.

[0006] To achieve the first objective of the present invention, the present invention provides a wavelength division multiplexer, comprising a silicon waveguide layer, wherein the silicon waveguide layer is provided with an input port and at least two output ports, wherein input light is input through the input port, and the output ports are located at first self-imaging positions of the input light; wherein a central axis of the input port forms a first angle with a long side of the silicon waveguide layer, and a central axis of the output port forms a second angle with the long side of the silicon waveguide layer, wherein the first angle is less than 90 degrees, and the second angle is less than 90 degrees; wherein a first distance is provided between the input port and a bottom side of the silicon waveguide layer, wherein the first distance is greater than zero and is less than the cosine value of the width of the silicon waveguide layer minus the width of the input port divided by the first angle; and wherein a thermo-optical phase shifter is provided above the silicon waveguide layer.

[0007] As can be seen from the above scheme, the wavelength division multiplexer of the present invention operates based on the self-imaging effect of an oblique-incidence multimode interferometer, where the self-imaging positions differ for different wavelengths. When the wavelengths of the input ports differ, the distance between the first self-imaging position and the output port of the wavelength division multiplexer also varies. Because the first angle formed by the central axis of the input port and the long side of the silicon waveguide layer is less than 90 degrees, the input light generates a lateral component on the wavelength division multiplexer in the same direction as the bottom edge. Therefore, the magnitude of this first distance directly affects the propagation path of the input light, resulting in different phase errors. When the first distance is greater than zero and less than the width of the silicon waveguide layer minus the width of the input port divided by the cosine of the first angle, simulations show that the phase error is reduced, the output loss of the wavelength division multiplexer is reduced, and the crosstalk between ports is reduced. By controlling the heat generated by the thermo-optical phase shifter to increase the temperature of the silicon waveguide layer, and thereby changing the effective refractive index of all modes in the multimode waveguide through the thermo-optical effect, the distance between the first self-imaging position of the input light and the output port can be controlled to a certain extent, reducing the phase error.

[0008] In a further solution, a linear tapered silicon layer is connected to the input port, and the width of the linear tapered silicon layer is uniformly widened along the transmission direction of the input light.

[0009] It can be seen that the width of the linear tapered structure silicon layer widens linearly, that is, widens uniformly, and the input light can be transmitted stably during transmission, avoiding the instability of the input light due to the sudden widening of the linear tapered structure silicon layer.

[0010] In a further solution, the cone tip of the linear cone-shaped silicon layer is arranged away from the input port.

[0011] In a further embodiment, the linear tapered silicon layer is a single-mode waveguide, and the silicon waveguide layer is a multi-mode waveguide.

[0012] It can be seen that the width of the single-mode waveguide is widened by the linear tapered silicon layer. When the input light enters the silicon waveguide layer, the optical signal can be stably input into the silicon waveguide layer, avoiding signal confusion caused by the sudden widening of the input light width.

[0013] In a further solution, the silicon waveguide layer is surrounded by a shallowly etched silicon layer, and the thickness of the shallowly etched silicon layer is less than the thickness of the silicon waveguide layer.

[0014] It can be seen that shallow etching of the silicon layer can reduce the effective refractive index difference of the silicon waveguide layer, thereby reducing the phase error.

[0015] In a further solution, the width of the thermo-optical phase shifter is greater than the width of the silicon waveguide layer, and the width of the shallowly etched silicon layer is greater than the width of the thermo-optical phase shifter.

[0016] It can be seen that the width of the shallowly etched silicon layer is larger than the width of the thermo-optical phase shifter, so that the phase error is further reduced.

[0017] In a further solution, electrodes are provided on two opposite sides of the thermo-optical phase shifter.

[0018] It can be seen that by setting electrodes, the thermo-optical phase shifter generates heat, thereby increasing the temperature of the silicon waveguide layer, and changing the effective refractive index of all modes in the silicon waveguide layer through the thermo-optic effect, thereby reducing the phase error.

[0019] In a further solution, the number of the thermo-optical phase shifter is one.

[0020] This shows that since the phase error of the silicon waveguide layer is minimal at this time, only one thermo-optical dependent device is required for thermo-optical compensation. This does not degrade the optical insertion loss and inter-channel crosstalk performance of the device, thereby improving the chip yield.

[0021] In order to achieve the second objective of the present invention, the silicon photonic chip provided by the present invention applies the above-mentioned wavelength division multiplexer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is a top view of an embodiment of a wavelength division multiplexer of the present invention.

[0023] Figure 2 It is a top view of a wavelength division multiplexer embodiment of the present invention including a shallowly etched silicon layer.

[0024] Figure 3 FIG. 1 is a side view of a wavelength division multiplexer including a shallowly etched silicon layer in an embodiment of the present invention.

[0025] Figure 4 It is a simulation diagram of an embodiment of the wavelength division multiplexer of the present invention.

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0027] The wavelength division multiplexer provided by the present invention has a first angle of less than ninety degrees formed between the central axis of the input port and the long side of the silicon waveguide layer, a first distance being greater than zero and less than the cosine value of the width of the silicon waveguide layer minus the width of the input port divided by the first angle, thereby reducing phase error, output loss of the wavelength division multiplexer, and crosstalk between ports.

[0028] Wavelength Division Multiplexer Example: See also Figure 1The wavelength division multiplexer of this embodiment is based on the physical characteristics of the oblique-incidence multimode interferometer, wherein the wavelength division multiplexer includes a silicon waveguide layer 13, which is a multimode waveguide. In this embodiment, the width of the silicon waveguide layer 13 is W m .W m The width of the silicon waveguide layer 13 is greater than 3 microns.

[0029] An input port 11 is provided on one side of the silicon waveguide layer 13. In this embodiment, the input port 11 is provided on one side of the short side of the silicon waveguide layer 13. Input light is input through the input port 11, and the input light comprises light of at least two wavelengths. In this embodiment, the input light comprises light of two wavelengths. The central axis of the input port 11 forms a first angle θ1 with the long side of the silicon waveguide layer 13, and the first angle θ1 is less than 90 degrees. When the input light is incident at an angle, it generates a lateral component on the wavelength division multiplexer in the same direction as the bottom side. Therefore, the magnitude of the first distance directly affects the propagation path of the input light. Therefore, different first distances result in different phase errors.

[0030] The other side of the silicon waveguide layer 13 is provided with two output ports. In this embodiment, the output ports are located on one side of the long side of the silicon waveguide layer 13. In this embodiment, there are two output ports. The two output ports are located at points A and B. The output ports are located at the positions where the input light self-images after the self-imaging effect. The central axis of each output port forms a second angle θ2 with the long side of the silicon waveguide layer. The second angle θ2 is less than 90 degrees and has the same degree as the first angle θ1.

[0031] After the input light is input from the input port 11, it is demultiplexed through the silicon waveguide layer 13 and decomposed into light of different wavelengths, which are output at two output ports A and B. In this embodiment, output port A outputs light of the first wavelength ch1, and output port B outputs light of the second wavelength ch2. The input port is also connected to a linear tapered structure silicon layer 111. The linear tapered structure silicon layer 111 has a linear tapered structure, that is, the width of the linear tapered structure silicon layer 111 uniformly widens along the transmission direction of the input light. The tip of the linear tapered structure silicon layer 111 is arranged away from the input port. The linear tapered structure silicon layer is a single-mode waveguide. The linear tapered structure silicon layer is a single-mode waveguide, and the silicon waveguide layer is a multi-mode waveguide. The linear tapered structure silicon layer serves as a router.

[0032] In this embodiment, the width of the single-mode waveguide at the tip of the linear tapered silicon layer is W r .W r The length of the linear conical structure silicon layer is L t , the width of the single-mode waveguide of the linear tapered silicon layer is widened to W I .W IThe linear tapered silicon layer 111 widens the single-mode waveguide width. This allows for stable input of the optical signal into the silicon waveguide layer, avoiding signal confusion caused by the sudden widening of the single-mode waveguide.

[0033] A first distance L is set between the input port 11 and the bottom edge of the silicon waveguide layer 13 u , the first distance is greater than zero, and the first distance L u It is smaller than the width of the silicon waveguide layer minus the width of the input port 11 divided by the cosine value of the first angle θ1. .W I is the single-mode waveguide width of the input port. Because the central axis of input port 11 forms a first angle θ1 with the long side of silicon waveguide layer 13, the angle between the width of input port 11 and the width of silicon waveguide layer 13 is the first angle θ1. Therefore, in this embodiment, the input port is not located on the bottom or top edge of silicon waveguide layer 13, thereby reducing phase error.

[0034] See also Figure 4 In this embodiment, a simulation experiment is set up, in which the width W of the silicon waveguide layer is m = 12 microns, θ = 15°, and the first distance L u Selected as 0 micron, 3 micron, 6 micron and 9 micron. Figure 4 It can be seen that when the first distance L u When it is greater than 0 microns, the phase error decreases, and the first distance L u The larger the distance, the smaller the phase error. u The width of the silicon waveguide layer cannot be less than the quotient of the width of the input port 11 divided by the cosine value of the first angle θ, to ensure that the silicon waveguide layer 13 can receive all the input light and avoid data errors caused by input light loss.

[0035] See also Figure 1 、 Figure 2 and Figure 3 A thermo-optical phase shifter 12 is positioned above the silicon waveguide layer 13. Electrodes have positive and negative polarity, meaning that two electrodes are positioned on opposite sides of the thermo-optical phase shifter 12, each with different polarities. The width of the thermo-optical phase shifter 12 is greater than that of the silicon waveguide layer 13, ensuring that the temperature of the entire silicon waveguide layer 13 is controlled by the thermo-optical phase shifter 12.

[0036] By injecting current into the thermo-optic phase shifter 12 through the electrodes, the thermo-optic phase shifter 12 generates heat, increasing the temperature of the silicon waveguide layer 13. This, in turn, changes the effective refractive index of all modes in the silicon waveguide layer through the thermo-optic effect, allowing the self-imaging position of the input light to be regulated. When the self-imaging position of the input light is not at the position of output port A or B, that is, when there is a phase error at output port A or B, the self-imaging position of the input light is regulated by controlling the temperature generated by the thermo-optic phase shifter 12. Furthermore, there is only one thermo-optic phase shifter 12. Because the phase error of the silicon waveguide layer 13 is small at this time, the self-imaging quality is high. Setting up one thermo-optic phase shifter 12 will not degrade the optical insertion loss and inter-channel crosstalk performance of the device, thereby improving the chip yield. However, setting up multiple thermo-optic phase shifters 12 may degrade the optical insertion loss and inter-channel crosstalk performance of the device.

[0037] See also Figure 2 and Figure 3 The silicon waveguide layer 13 is surrounded by a shallowly etched silicon layer 14, which is thinner than the silicon waveguide layer. The shallowly etched silicon layer 14 is fabricated using a shallow etching process. This layer adjusts the refractive index distribution around the waveguide, enabling precise control of the optical mode. The width of the shallowly etched silicon layer 14 is greater than that of the thermo-optical phase shifter 12. This expansion of the shallowly etched region dynamically adjusts the refractive index distribution around the waveguide, thereby suppressing mode crosstalk.

[0038] The present invention utilizes a first angle less than 90 degrees formed between the central axis of the input port and the long side of the silicon waveguide layer, causing the input light to generate a lateral component on the wavelength division multiplexer in the same direction as the bottom edge. This allows the wavelength division multiplexer to operate based on the self-imaging effect of an obliquely incident multimode interferometer. Input light of different wavelengths can generate self-images at different locations when the self-imaging effect is generated, resulting in output from different output ports. Because the input light generates a lateral component on the wavelength division multiplexer in the same direction as the bottom edge, a first distance is set between the input port and the bottom edge of the multicast waveguide. This distance directly affects the propagation path of the input light, resulting in different phase errors. Simulation results indicate that the phase error is reduced when the first distance is greater than zero and less than the value obtained by subtracting the width of the input port from the width of the silicon waveguide layer, divided by the cosine of the first angle.

[0039] Silicon photonic chip example: The silicon photonic chip applies the wavelength division multiplexer of the wavelength division multiplexer embodiment described above, thereby reducing phase error and improving communication quality.

[0040] The above are only preferred embodiments of the present invention, but the design concept of the invention is not limited to this. Without departing from the concept of the present invention, it can also include more other equivalent embodiments. It is obvious that various changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention.

Claims

1. A wavelength division multiplexer comprising a silicon waveguide layer, wherein the silicon waveguide layer is provided with an input port and at least two output ports, wherein input light is input through the input port, and the positions of the output ports are self-imaging positions of the input light; The central axis of the input port forms a first angle with the long side of the silicon waveguide layer, and the central axis of the output port forms a second angle with the long side of the silicon waveguide layer, the first angle is less than ninety degrees, and the second angle is less than ninety degrees; Its characteristics are: A first distance is set between the input port and the bottom edge of the silicon waveguide layer, the first distance is greater than zero, and the first distance is less than the width of the silicon waveguide layer minus the width of the input port divided by the cosine value of the first angle; A thermo-optical phase shifter is arranged above the silicon waveguide layer.

2. The wavelength division multiplexer according to claim 1, wherein: The input port is connected to a linear tapered silicon layer, and the width of the linear tapered silicon layer is uniformly widened along the transmission direction of the input light.

3. The wavelength division multiplexer according to claim 2, wherein: The cone tip of the linear cone-shaped silicon layer is arranged away from the input port.

4. The wavelength division multiplexer according to claim 3, wherein: The linear tapered structure silicon layer is a single-mode waveguide, and the silicon waveguide layer is a multi-mode waveguide.

5. The wavelength division multiplexer according to claim 1, wherein: The silicon waveguide layer is surrounded by a shallow etched silicon layer, and the thickness of the shallow etched silicon layer is less than the thickness of the silicon waveguide layer.

6. The wavelength division multiplexer according to claim 5, wherein: The width of the thermo-optical phase shifter is greater than the width of the silicon waveguide layer, and the width of the shallowly etched silicon layer is greater than the width of the thermo-optical phase shifter.

7. The wavelength division multiplexer according to any one of claims 1 to 6, characterized in that: Electrodes are provided on two opposite sides of the thermo-optical phase shifter.

8. The wavelength division multiplexer according to any one of claims 1 to 6, characterized in that: The number of the thermo-optical phase shifter is one.

9. Silicon photonic chip, characterized in that: A wavelength division multiplexer according to any one of claims 1 to 8 is used.

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