A subwavelength grating-assisted adiabatic power divider

Abstract

The present invention relates to a subwavelength grating-assisted adiabatic power divider, comprising an input conversion region, a tapered interleaved region, and an output conversion region, arranged in sequence. The input conversion region is used to transmit light entering an input waveguide into the tapered interleaved region; the output conversion region is used to transmit light passing through the tapered interleaved region into an output waveguide. The tapered interleaved region includes a first subwavelength grating waveguide, a second subwavelength grating waveguide, and a third subwavelength grating waveguide. The first, second, and third subwavelength grating waveguides have identical structures and are arranged perpendicularly along the direction of light transmission. The spacing between the first and second subwavelength grating waveguides, as well as the spacing between the second and third subwavelength grating waveguides, remains constant. Light in the second subwavelength grating waveguide is coupled into the first and third subwavelength grating waveguides, respectively, along the direction of light transmission. The present invention can improve the integration density of on-chip devices.

Description

Technical Field

[0001] The present invention relates to the field of silicon-based optoelectronic technology, in particular to a sub-wavelength grating-assisted adiabatic power divider. Background Art

[0002] Silicon-based optoelectronics technology utilizes mature microelectronics complementary metal oxide semiconductor (CMOS) process equipment to manufacture optoelectronic devices and chips for optical communications, optical interconnects, and optical signal processing on silicon-on-insulator (SOI), enabling low-cost, mass production. It is an emerging and hot technology in the international optical communications field. Silicon-based optical splitters are fundamental components for optical splitting and routing, and are widely used in optical switches, Mach-Zehnder interferometers (MZIs), and optical sensors.

[0003] Currently, the main methods for implementing on-chip power dividers include Y-splitters, directional couplers, and multimode interferometers. Due to manufacturing defects, traditional Y-splitters typically have a high insertion loss of 1dB and a splitting ratio of 3dB. For directional couplers, the power splitting can be designed by controlling the coupling length and distance between the two waveguides, but the coupling ratio is highly dependent on the input wavelength. Multimode interferometers have advantages such as relatively small size and high manufacturing tolerances, but also have disadvantages such as wavelength dependence and high insertion loss. To achieve arbitrary optical power splitting ratios while alleviating wavelength sensitivity, asymmetric multimode interferometer structures have been proposed. However, due to the small dimensions of the structure, the processing requirements are very high, meaning that the process tolerances are very narrow, and this can also result in high additional losses. Adiabatic designs are often used to address the device's wavelength sensitivity and processing sensitivity, but this significantly increases the device length, hindering device miniaturization and reducing the overall chip integration density. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a sub-wavelength grating (SWG)-assisted adiabatic power divider, which can improve the integration of on-chip devices.

[0005] The present invention solves the technical problem by adopting a technical solution: providing a subwavelength grating-assisted adiabatic power divider, comprising an input conversion region, a tapered interleaved region, and an output conversion region arranged in sequence; the input conversion region is used to transmit light entering an input waveguide into the tapered interleaved region; the output conversion region is used to transmit light passing through the tapered interleaved region into an output waveguide; the tapered interleaved region comprises a first subwavelength grating waveguide, a second subwavelength grating waveguide, and a third subwavelength grating waveguide; the first subwavelength grating waveguide, the second subwavelength grating waveguide, and the third subwavelength grating waveguide have the same structure and are arranged vertically along the direction of light transmission; the spacing between the first subwavelength grating waveguide and the second subwavelength grating waveguide, as well as the spacing between the second subwavelength grating waveguide and the third subwavelength grating waveguide, are both constant; and light in the second subwavelength grating waveguide is coupled into the first subwavelength grating waveguide and the third subwavelength grating waveguide respectively along the direction of light transmission.

[0006] The input conversion region includes a strip waveguide to sub-wavelength grating waveguide conversion structure, and the strip waveguide to sub-wavelength grating waveguide conversion structure includes a first tapered waveguide and a first grating structure. The first tapered waveguide is tapered along the direction of light transmission. The first grating structure is arranged around the first tapered waveguide, and its period and silicon block width are the same as those of the first sub-wavelength grating waveguide.

[0007] The output conversion region includes two identical sub-wavelength grating waveguide to strip waveguide conversion structures, and the sub-wavelength grating waveguide to strip waveguide conversion structure includes a second tapered waveguide and a second grating structure. The second tapered waveguide is tapered along the opposite direction of light transmission. The second grating structure is arranged around the second tapered waveguide, and its period and silicon block width are the same as those of the first sub-wavelength grating waveguide.

[0008] The first sub-wavelength grating waveguide and the third sub-wavelength grating waveguide are tapered along opposite directions of light transmission, and the second sub-wavelength grating waveguide is tapered along the direction of light transmission; the second sub-wavelength grating waveguide is located in the gap formed by the first sub-wavelength grating waveguide and the third sub-wavelength grating waveguide, and the splitting ratio is adjusted by adjusting the position of the second sub-wavelength grating waveguide.

[0009] The input waveguide and the output waveguide are strip waveguides, and the output waveguide is connected to the output conversion region through an S band.

[0010] Beneficial effects

[0011] Due to the adoption of the above-mentioned technical solution, the present invention has the following advantages and positive effects compared with the prior art: the present invention adopts a tapered staggered trident structure, in which a sub-wavelength grating (SWG) structure is used at the tapered staggering, which shortens the size of the device and thus improves the integration of on-chip devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 1 is a schematic structural diagram of an adiabatic power distributor according to an embodiment of the present invention;

[0013] Figure 2 Schematic diagram of connecting input and output waveguides of an adiabatic power divider according to an embodiment of the present invention;

[0014] Figure 3 1 is a transmission spectrum of the adiabatic power divider according to an embodiment of the present invention within the 1200-1700 nm band;

[0015] Figure 4 Schematic diagram of the corresponding splitting ratio of the adiabatic power divider under different N values according to an embodiment of the present invention;

[0016] Figure 5 1500-1600 nm transmission spectrum of the adiabatic power divider at different duty cycles according to the embodiment of the present invention;

[0017] Figure 6 1 is a transmission spectrum diagram of the adiabatic power divider in the 1500-1600 nm band at different N values according to an embodiment of the present invention;

[0018] Figure 7 Schematic diagram of insertion loss of the adiabatic power divider at different temperatures according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0020] The embodiments of the present invention relate to a sub-wavelength grating assisted adiabatic power divider, such as Figure 1 and Figure 2As shown, it includes an input conversion area 1, a tapered interleaved area 2, and an output conversion area 3 arranged in sequence; the input conversion area 1 is used to send light entering the input waveguide 4 into the tapered interleaved area 2; the output conversion area 3 is used to send light passing through the tapered interleaved area 2 into the output waveguide 5; the tapered interleaved area 2 includes a first subwavelength grating waveguide 21, a second subwavelength grating waveguide 22, and a third subwavelength grating waveguide 23; the first subwavelength grating waveguide 21, the second subwavelength grating waveguide 22, and the third subwavelength grating waveguide 23 have the same structure and are arranged vertically along the direction of light transmission; the interval G between the first subwavelength grating waveguide 21 and the second subwavelength grating waveguide 22 is 1 / 4. u and the interval G between the second sub-wavelength grating waveguide 22 and the third sub-wavelength grating waveguide 23 b the light in the second sub-wavelength grating waveguide 22 is coupled to the first sub-wavelength grating waveguide 21 and the third sub-wavelength grating waveguide 23 along the transmission direction of the light.

[0021] The adiabatic power divider of this embodiment is a trident-like structure, such as Figure 1 As shown, the entire structure is divided into three parts by black dotted lines: input transition region 1, tapered interleaved region 2 and output transition region 3.

[0022] The input conversion region 1 includes a strip waveguide to subwavelength grating waveguide conversion structure. Light is input from the single-mode strip waveguide in the middle and enters the tapered interleaved region through the conversion structure. The conversion structure consists of a tapered waveguide 11 with a width gradually changing from W1 to Wt and a grating structure 12 with the same period as the SWG waveguide in the tapered interleaved region and the same silicon block width. The length of the entire input conversion region 1 is L T .

[0023] The tapered interleaved region 2 is composed of three sections of sub-wavelength grating waveguides, namely the first sub-wavelength grating waveguide 21, the second sub-wavelength grating waveguide 22, and the third sub-wavelength grating waveguide 23. The first sub-wavelength grating waveguide 21 and the third sub-wavelength grating waveguide 23 are tapered in opposite directions of light transmission, and the second sub-wavelength grating waveguide 22 is tapered in the direction of light transmission. The second sub-wavelength grating waveguide 22 is located in the gap formed by the first sub-wavelength grating waveguide 21 and the third sub-wavelength grating waveguide 23. The second sub-wavelength grating waveguide 22 located in the middle is the input part of the tapered interleaved region 2. The first sub-wavelength grating waveguide 21 located above the second sub-wavelength grating waveguide 22 and the third sub-wavelength grating waveguide 23 located below the second sub-wavelength grating waveguide 22 are the two output parts of the tapered interleaved region 2. The three sections of sub-wavelength grating waveguides have the same composition, such as Figure 1As shown in the dotted box in the upper left corner, the entire grating period is a, the width of the silicon block is t, and the duty cycle (i.e., the ratio of the silicon block width to the period) is defined as the duty cycle ff. The interval G between the first sub-wavelength grating waveguide 21 and the second sub-wavelength grating waveguide 22 is u and the interval G between the second sub-wavelength grating waveguide 22 and the third sub-wavelength grating waveguide 23 b It remains unchanged in the entire tapered interleaved region 2. In the tapered interleaved region 2, the light of the second sub-wavelength grating waveguide 22 is gradually coupled into the first sub-wavelength grating waveguide 21 and the third sub-wavelength grating waveguide 23 along the transmission direction. The length of the entire tapered interleaved region 2 is L C .

[0024] In the output conversion region 3, the light coupled into the first sub-wavelength grating waveguide 21 and the third sub-wavelength grating waveguide 23 passes through a SWG waveguide to strip waveguide conversion structure and enters the output waveguide for output. The conversion structure includes a second tapered waveguide 31 and a second grating structure 32. The second tapered waveguide 31 is tapered in the opposite direction of light transmission. The second grating structure 32 is arranged around the second tapered waveguide 31, and its period and silicon block width are the same as those of the first sub-wavelength grating waveguide 21. In this embodiment, the output conversion region 3 is the inverse structure of the input conversion region 1, and all parameters of the two are the same. Since the two output ends of the output conversion region 3 are close to each other, in order to avoid mutual interference of the light at the two output ends, a method such as Figure 2 The S-shaped waveguide shown is used as an output waveguide to separate the two output ends and avoid unnecessary device performance degradation caused by mutual coupling between the two output ends.

[0025] By optimizing the above parameters, the coupling region length L is achieved. C Only 6um, the transition zone length L T The compact power divider is 5um in diameter and 16um in total length, with the smallest dimension of the entire device being 100nm of W2. Figure 3 The interval G between the first sub-wavelength grating waveguide 21 and the second sub-wavelength grating waveguide 22 is given as u and the interval G between the second sub-wavelength grating waveguide 22 and the third sub-wavelength grating waveguide 23 bThe transmission spectrum of the 50 / 50 power divider is 100nm. The two outputs of the entire power divider are consistent and above -3.1dB in the wavelength range of 1200-1700nm (500nm). The transmission rate basically does not change with wavelength, which shows that the designed device is adiabatic. According to the loss definition (the loss is calculated by adding the optical power tables of the two outputs and then calculating it with the input optical power), the calculated loss is less than 0.1dB, which successfully achieves low loss. In this embodiment, different splitting ratios can be achieved by adjusting the relative size between the interval Gu and the interval Gb while ensuring that the values of the interval Gu and the interval Gb are not too large. By changing the interval G b To interval G u N times, keeping the interval Gu unchanged at 100nm, Figure 4 The output optical power spectra of the upper and lower ports at different N values within the 100nm wavelength range are given. Theoretically, through careful optimization design, a power divider with any splitting ratio from 1% to 99% can be designed.

[0026] In order to verify that the device has a large process tolerance, the duty cycle ff and G of the SWG waveguide are b / G u Scan and get the corresponding transmission spectrum as Figure 5 and Figure 6 As shown. Figure 5 It can be seen that as long as the duty cycle ff>45%, the loss of the power divider (for a 50 / 50 power divider, the loss is calculated relative to -3dB) is less than 0.1dB in the wavelength range of 1500-1600nm. b / G u For example (see Figure 6 ), at a wavelength of 1550nm, or even at 200nm, the loss is less than 0.2dB, which ensures the device is insensitive to the processing technology.

[0027] In addition, considering that the operating temperature of the device may not be near room temperature and the large thermo-optical coefficient of Si material itself, the performance of the device at 0-75℃ was simulated. The results are as follows: Figure 7 shown. Figure 7 The total insertion loss of the device remains essentially unchanged at around 0.03dB, demonstrating excellent thermal stability. The subwavelength grating-assisted adiabatic power divider described above not only operates in the OC band (1500-1600nm), but is also suitable for optimizing the design of adiabatic power dividers in other bands.

Claims

1. A subwavelength grating-assisted adiabatic power divider, characterized in that: The optical fiber optical fiber transmission device comprises an input conversion region, a tapered interleaving region and an output conversion region arranged in sequence; the input conversion region is used to send light entering the input waveguide into the tapered interleaving region; the output conversion region is used to send light passing through the tapered interleaving region into the output waveguide; the tapered interleaving region comprises a first sub-wavelength grating waveguide, a second sub-wavelength grating waveguide and a third sub-wavelength grating waveguide; the first sub-wavelength grating waveguide, the second sub-wavelength grating waveguide and the third sub-wavelength grating waveguide have the same structure and are arranged vertically along the direction of light transmission; the interval between the first sub-wavelength grating waveguide and the second sub-wavelength grating waveguide and the interval between the first sub-wavelength grating waveguide and the second sub-wavelength grating waveguide are the same; the interval between the first sub-wavelength grating waveguide and the second sub-wavelength grating waveguide and the third ... The intervals between the second sub-wavelength grating waveguide and the third sub-wavelength grating waveguide remain unchanged; light in the second sub-wavelength grating waveguide is coupled to the first sub-wavelength grating waveguide and the third sub-wavelength grating waveguide respectively along the transmission direction of the light; the first sub-wavelength grating waveguide and the third sub-wavelength grating waveguide are tapered along the opposite directions of light transmission, and the second sub-wavelength grating waveguide is tapered along the direction of light transmission; the second sub-wavelength grating waveguide is located in the gap formed by the first sub-wavelength grating waveguide and the third sub-wavelength grating waveguide, and the splitting ratio is adjusted by adjusting the position of the second sub-wavelength grating waveguide.

2. The subwavelength grating-assisted adiabatic power divider according to claim 1, characterized in that: The input conversion region includes a strip waveguide to sub-wavelength grating waveguide conversion structure, and the strip waveguide to sub-wavelength grating waveguide conversion structure includes a first tapered waveguide and a first grating structure. The first tapered waveguide is tapered along the direction of light transmission. The first grating structure is arranged around the first tapered waveguide, and its period and silicon block width are the same as those of the first sub-wavelength grating waveguide.

3. The sub-wavelength grating-assisted adiabatic power divider according to claim 1, characterized in that: The output conversion region includes two identical sub-wavelength grating waveguide to strip waveguide conversion structures, and the sub-wavelength grating waveguide to strip waveguide conversion structure includes a second tapered waveguide and a second grating structure. The second tapered waveguide is tapered along the opposite direction of light transmission. The second grating structure is arranged around the second tapered waveguide, and its period and silicon block width are the same as those of the first sub-wavelength grating waveguide.

4. The sub-wavelength grating-assisted adiabatic power divider according to claim 1, wherein: The input waveguide and the output waveguide are strip waveguides, and the output waveguide is connected to the output conversion region through an S band.

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