A silicon photonics chip temperature sensor

Abstract

The present invention relates to a silicon photonics chip temperature sensor, which includes an input waveguide with a silica cladding, an input Y-shaped waveguide, a first sensing waveguide, a second sensing waveguide, an output Y-shaped waveguide, and an output waveguide. The input waveguide is connected to the input end of the input Y-shaped waveguide. The two output ends of the input Y-shaped waveguide are respectively connected to the two input ends of the output Y-shaped waveguide after being connected in series with the first sensing waveguide and the second sensing waveguide respectively. The output end of the output Y-shaped waveguide is connected to the output waveguide. The second sensing waveguide includes three silicon waveguides arranged closely side by side. The two ends of the silicon waveguide in the middle are respectively connected to the input Y-shaped waveguide and the output Y-shaped waveguide. In the first sensing waveguide, the optical signal is confined to propagate in the silicon waveguide. In the second sensing waveguide, the optical signal is confined to propagate in the silica cladding between adjacent silicon waveguides. This temperature sensor realizes built-in integrated silicon photonics chip temperature detection with high reliability.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technologies, particularly to the field of silicon photonics chip technologies, and specifically to a silicon photonics chip temperature sensor. Background Art

[0002] Silicon photonics chips have advantages such as small size, high bandwidth, and low power consumption, and have great application prospects in the field of optical communication, including various different environments such as data centers and the Internet of Things. However, silicon has a relatively high thermo-optic coefficient, which causes the optical characteristics of silicon photonics chips to vary significantly under different temperature environments. Therefore, in order to ensure the working stability of silicon photonics chips, it is necessary to monitor the temperature of silicon photonics chips. Currently, silicon photonics chip temperature sensors can be divided into two categories, including external temperature sensors and internal temperature sensors. The advantage of external temperature sensors is that they can combine existing temperature sensing technologies to detect the temperature of silicon photonics chips externally. However, their disadvantage is that they cannot quickly and accurately detect the temperature change of the core waveguide of silicon photonics chips because the core waveguide of silicon photonics chips is wrapped in a silica cladding. Internal temperature sensors can overcome this disadvantage by integrating temperature sensors inside the silicon photonics chip to achieve real-time and accurate temperature detection. There are two common structures for internal temperature sensors, but these temperature sensors have room for further improvement in terms of size, power consumption, cost, operating conditions, etc. One type of internal silicon photonics chip temperature sensor is based on the optical frequency domain reflectometry technique and realizes temperature sensing by measuring the drift of the Rayleigh scattering spectrum of the silicon photonics chip. Its device includes a swept laser, an optical fiber splitter, an optical fiber circulator, an optical fiber coupler, a photodetector, and a data acquisition card, etc. The entire system has a large size, complex data processing, and high cost. Another type of internal silicon photonics chip temperature sensor is composed of an input / output silicon waveguide and a microring waveguide. Optical signals are introduced by the silicon waveguide, and optical signals with certain specific wavelengths are coupled into the microring waveguide, and the remaining optical signals are output by the same silicon waveguide. Its disadvantage is that it has high requirements for the light source, which must be a light source operating in a specific wavelength range. Summary of the Invention

[0003] In view of the technical problems existing in the prior art, the present invention provides a silicon photonics chip temperature sensor to solve at least one of the technical problems proposed in the background art.

[0004] The technical solution of the present invention to solve the above technical problems is as follows:

[0005] A silicon photonic chip temperature sensor includes an input waveguide with a silica cladding, an input Y-branch waveguide, a first sensing waveguide, a second sensing waveguide, an output Y-branch waveguide, and an output waveguide. The input end of the input waveguide receives an optical signal input, the output end of the input waveguide is connected to the input end of the input Y-branch waveguide, one output end of the input Y-branch waveguide is connected to one input end of the output Y-branch waveguide through the first sensing waveguide, the other output end of the input Y-branch waveguide is connected to the other input end of the output Y-branch waveguide through the second sensing waveguide, and the output end of the output Y-branch waveguide is connected to the output waveguide;

[0006] The first sensing waveguide includes a silicon waveguide; the second sensing waveguide includes three silicon waveguides arranged closely side by side. The distance between adjacent silicon waveguides in the second sensing waveguide is at the nanometer level. The three silicon waveguides in the second sensing waveguide are filled with a silica cladding. The two ends of the middle silicon waveguide among the three side-by-side silicon waveguides are respectively connected to the output end of the input Y-branch waveguide and the input end of the output Y-branch waveguide;

[0007] In the first sensing waveguide, the optical signal is confined to propagate in the silicon waveguide; in the second sensing waveguide, the optical signal is confined to propagate in the silica cladding between adjacent silicon waveguides.

[0008] Furthermore, the input waveguide, the input Y-branch waveguide, the first sensing waveguide, the second sensing waveguide, the output Y-branch waveguide, and the output waveguide are all silicon waveguides with a height of 220 nm.

[0009] Furthermore, in the second sensing waveguide, the widths of the three side-by-side silicon waveguides are all 300 nm.

[0010] Furthermore, in the second sensing waveguide, the distance between adjacent silicon waveguides is 150 nm.

[0011] The beneficial effects of the present invention are as follows: The temperature sensor provided by the present invention is suitable for being disposed in a silicon photonics chip. An optical signal is provided by a light source in the silicon photonics chip, and the optical signal is input into the temperature sensor through an input waveguide. After being split by an input Y-shaped waveguide, the optical signal is respectively sent into a first sensing waveguide and a second sensing waveguide. In the first sensing waveguide, the optical signal is confined to propagate in the silicon waveguide, while in the second sensing waveguide, the optical signal is confined to propagate in the silica cladding between adjacent silicon waveguides. The two optical signals are converged and output through an output Y-shaped waveguide. After the two signals are converged, optical signal interference occurs, so that the output optical signal shows peaks and valleys. The corresponding temperature value can be obtained by detecting the value of the spectral valley. Since the thermo-optical coefficients of silicon and silica are different, the change in the refractive index of silicon and the change in the refractive index of silica caused by temperature changes in the silicon photonics chip are different. Therefore, when the temperature changes, the output signal generated by the interference of the first sensing waveguide and the second sensing waveguide will drift, and the internal core temperature of the silicon photonics chip can be sensed by detecting the wavelength change of the output optical signal. The temperature sensor has the following advantages:

[0012] 1. Realize the temperature detection of the built-in integrated silicon photonics chip;

[0013] 2. High overall integration, miniaturized size, low cost and high reliability;

[0014] 3. Can be matched with light sources having different working wavelengths, reducing the requirements for the working wavelength range of the light source.

[0015] 4. The symmetric structure enables the interchange of the input end and the output end. Brief Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the structural composition of the present invention;

[0017] Figure 2 It is a schematic diagram of the silicon waveguide structure in the second sensing waveguide of the present invention;

[0018] Figure 3 It is a schematic diagram of the optical energy distribution in the second sensing waveguide of the present invention;

[0019] Figure 4 It is a schematic diagram of the optical signal transmission of the present invention;

[0020] Figure 5 It is a schematic diagram of the spectral change at different temperatures in the embodiment of the present invention.

[0021] In the drawings, the list of components represented by each reference numeral is as follows:

[0022] 1. Input waveguide, 2. Input Y-shaped waveguide, 3. First sensing waveguide, 4. Second sensing waveguide, 5. Output Y-shaped waveguide, 6. Output waveguide, a. Silicon waveguide, b. Silica cladding. Detailed implementation manners

[0023] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0024] As Figure 1 shown, a silicon photonics chip temperature sensor is provided in a silicon photonics chip and is based on a Mach-Zehnder structure. It includes an input waveguide 1 provided with a silica cladding, an input Y-shaped waveguide 2, a first sensing waveguide 3, a second sensing waveguide 4, an output Y-shaped waveguide 5, and an output waveguide 6. The input end of the input waveguide 1 receives an optical signal input, the output end of the input waveguide 1 is connected to the input end of the input Y-shaped waveguide 2, one output end of the input Y-shaped waveguide 2 is connected to one input end of the output Y-shaped waveguide 5 through the first sensing waveguide 3, the other output end of the input Y-shaped waveguide 2 is connected to the other input end of the output Y-shaped waveguide 5 through the second sensing waveguide 3, and the output end of the output Y-shaped waveguide 5 is connected to the output waveguide 6. A spectral detector is provided at the output end of the output waveguide 6 for detecting the optical signal output by the temperature sensor. The first sensing waveguide 3 includes a silicon waveguide, and a silica cladding is provided outside the silicon waveguide. As Figures 2 - 3 shown, the second sensing waveguide 4 includes three silicon waveguides arranged closely side by side, and the cross-sections of the three silicon waveguides are rectangular. In this embodiment, in the second sensing waveguide 4, the spacing between adjacent silicon waveguides a is 150 nm, and a silica cladding b is filled between the three silicon waveguides a of the second sensing waveguide 4. The two ends of the middle silicon waveguide a among the three side-by-side silicon waveguides a are respectively connected to the output end of the input Y-shaped waveguide 2 and the input end of the output Y-shaped waveguide 5. Since silicon has a higher refractive index than silica, in the case of only a single silicon waveguide, the high-refractive-index silicon waveguide is covered by the low-refractive-index silica cladding, and the optical energy is confined in the high-refractive-index silicon waveguide. Therefore, in the first sensing waveguide 3, the optical signal is confined to propagate in the silicon waveguide. There is also a case where the optical energy may be confined in a uniform and narrow slit with a low refractive index. As Figure 3 shown is a cross-sectional schematic diagram of the second sensing waveguide 4 when the optical signal propagates. In the second sensing waveguide 4, the optical signal is input from the middle silicon waveguide a, and the two silicon waveguides a on both sides are equivalent to two high-refractive-index plates. Two uniform slits with a spacing not greater than 150 nm are formed between the three adjacent high-refractive-index silicon waveguides a, and the nano-scale slits are filled with a low-refractive-index silica cladding b. As Figure 3 shown, the higher the brightness in the area, the more concentrated the optical energy in that area. A considerable amount of optical energy is confined in these two slits, that is, the optical signal is confined to propagate in the silica cladding between adjacent silicon waveguides.

[0025] The temperature sensor of this embodiment is suitable for being set in a silicon photonic chip. The light source in the silicon photonic chip provides an optical signal. The optical signal is input into the temperature sensor through the input waveguide 1. After being introduced into the Y-type waveguide 2 for splitting, the optical signal is sent to the first sensing waveguide 3 and the second sensing waveguide 4 respectively. The first sensing waveguide 3 and the second sensing waveguide 4 are the temperature sensing parts of this temperature sensor. In the first sensing waveguide 3, the optical signal is bound to propagate in the silicon waveguide, while in the second sensing waveguide 4, the optical signal is bound to propagate in the silicon dioxide cladding b between adjacent silicon waveguides a. The two optical signals are output after being converged through the Y-type waveguide 5. A spectrum detector is set at the output end of the output waveguide 6 to detect the converged optical signal.

[0026] After the two signals in the first sensing waveguide 3 and the second sensing waveguide 4 converge in the derived Y-type waveguide 5, optical signal interference occurs, so that the output optical signal has peaks and troughs. The corresponding temperature value can be obtained by detecting the value of the spectrum trough. Since the thermal-optical coefficients of silicon and silicon dioxide are different, the change in the silicon refractive index caused by the temperature change in the silicon photonic chip is different from the change in the silicon refractive index of silicon dioxide. Therefore, when the temperature changes, the output signal generated by the interference of the first sensing waveguide 3 and the second sensing waveguide 4 will drift. By detecting the change in the wavelength of the output optical signal, the internal core temperature of the silicon photonic chip can be sensed.

[0027] In this embodiment, the input waveguide 1, the import Y-type waveguide 2, the first sensing waveguide 3, the second sensing waveguide 4, the export Y-type waveguide 5 and the output waveguide 6 are all silicon waveguides with a height of 220 nm.

[0028] In this embodiment, the width of the three silicon waveguides arranged side by side in the second sensing waveguide 4 is 300nm and the length is 60μm. When the wavelength of the light source is greater than 1300nm, most of the light energy will be bound in the silicon dioxide cladding b between the three silicon waveguides a. The temperature sensor can be matched with light sources with different working wavelengths by adjusting the length of the first sensing waveguide 3 and / or the second sensing waveguide 4, which reduces the requirements for the light source.

[0029] like Figure 4 The propagation path of the optical signal in the temperature sensor is shown. The dark area in the figure is the area where the optical signal propagates. The darker the color, the stronger the optical signal here. The output signal is obtained by the interference of the two sensing signals. Since the temperature sensor has a symmetrical structure, its input end and output end can be interchanged, that is, the functions of the input waveguide 1 and the output waveguide 6 can be interchanged, which increases the applicability of the temperature sensor.

[0030] Working principle:

[0031] The temperature sensor provided in this embodiment is applicable to be arranged in a silicon photonics chip. An optical signal is provided by a light source in the silicon photonics chip. The optical signal is input into the temperature sensor through an input waveguide 1. After being split by an input Y-shaped waveguide 2, the optical signal is respectively sent into a first sensing waveguide 3 and a second sensing waveguide 4. In the first sensing waveguide 3, the optical signal is confined to propagate in the silicon waveguide; while in the second sensing waveguide 4, the optical signal is confined to propagate in a silica cladding b between adjacent silicon waveguides a. The two optical signals are converged and output after passing through an output Y-shaped waveguide 5. After the two signals are converged, optical signal interference occurs, so that the output optical signal shows peaks and valleys. Specifically, silicon has a relatively high thermo-optic coefficient (1.8×10 -4 K -1 ), but silica has a relatively low thermo-optic coefficient (1.1×10 -5 K -1 ). Due to the different thermo-optic coefficients of silicon and silica, the change in the refractive index of silicon and the change in the refractive index of silica caused by temperature changes in the silicon photonics chip are different. Therefore, when the temperature changes, the output signal generated by the interference of the first sensing waveguide 3 and the second sensing waveguide 4 will drift. By detecting the wavelength change of the optical signal output from the output waveguide 6, the internal core temperature of the silicon photonics chip can be sensed.

[0032] The light emitted by the light source propagates in the silicon waveguide and in the silica respectively, as Figure 5 shown. The optical signal after the superposition of the two beams of light output from the first sensing waveguide 3 and the second sensing waveguide 4 is related to the refractive indices of the two beams of light. Temperature changes will cause changes in the refractive indices of silicon and silica, but the rates of change of the two refractive indices with temperature are different. Therefore, at different temperatures, the spectra after the superposition of the two beams of light are different, and there is a one-to-one correspondence between the spectrum and the temperature. The temperature value of the chip can be determined through the spectrum. Figure 5 shows the output spectrum drift of the temperature sensor of this embodiment at 25°C, 50°C, 80°C, and 120°C. The following formulae are applicable to the change in refractive index, thermo-optic coefficient, and temperature change:

[0033] △n = (dn / dT) * △T,

[0034] where △n is the change in refractive index, dn / dT is the thermo-optic coefficient, and △T is the temperature change.

[0035] The final temperature value is determined by the curve valley value in Figure 5 . After initial calibration, one valley value corresponds to one temperature. By detecting the spectrum valley value, the chip temperature can be obtained.

[0036] The overall size of the temperature sensor can be miniaturized to 100μm×30μm, greatly optimizing the space utilization efficiency and reducing the manufacturing cost. In addition, the temperature sensor can be matched with light sources having different operating wavelengths by adjusting the length of the first sensing waveguide 3 or the second sensing waveguide 4, reducing the requirements for the light source. Meanwhile, the symmetric structure of the temperature sensor enables the interchange of the input end and the output end, further expanding the applicability of the temperature sensor.

[0037] In summary, the temperature sensor has the following advantages:

[0038] 1. It realizes the temperature detection of the built-in integrated silicon optical chip;

[0039] 2. It has a high overall integration degree, miniaturized size, low cost and high reliability;

[0040] 3. It can be matched with light sources having different operating wavelengths, reducing the requirements for the operating wavelength range of the light source.

[0041] 4. The symmetric structure enables the interchange of the input end and the output end.

[0042] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A silicon photonics chip temperature sensor, characterized in that, it includes an input waveguide (1) with a silica cladding, an input Y-shaped waveguide (2), a first sensing waveguide (3), a second sensing waveguide (4), an output Y-shaped waveguide (5) and an output waveguide (6). The input end of the input waveguide (1) receives an optical signal input, the output end of the input waveguide (1) is connected to the input end of the input Y-shaped waveguide (2), one output end of the input Y-shaped waveguide (2) is connected to one input end of the output Y-shaped waveguide (5) through the first sensing waveguide (3), the other output end of the input Y-shaped waveguide (2) is connected to the other input end of the output Y-shaped waveguide (5) through the second sensing waveguide (4), and the output end of the output Y-shaped waveguide (5) is connected to the output waveguide (6); the first sensing waveguide (3) includes a silicon waveguide; the second sensing waveguide (4) includes three silicon waveguides arranged closely side by side, the spacing between adjacent silicon waveguides in the second sensing waveguide (4) is at the nanometer level, and the three silicon waveguides in the second sensing waveguide (4) are filled with silica cladding. The two ends of the middle silicon waveguide among the three side-by-side silicon waveguides are respectively connected to the output end of the input Y-shaped waveguide (2) and the input end of the output Y-shaped waveguide (5); in the first sensing waveguide (3), the optical signal is confined to propagate in the silicon waveguide; in the second sensing waveguide (4), the optical signal is confined to propagate in the silica cladding between adjacent silicon waveguides.

2. The silicon photonics chip temperature sensor according to claim 1, characterized in that, the input waveguide (1), the input Y-shaped waveguide (2), the first sensing waveguide (3), the second sensing waveguide (4), the output Y-shaped waveguide (5) and the output waveguide (6) are all silicon waveguides with a height of 220 nm.

3. The silicon photonics chip temperature sensor according to claim 1, characterized in that, in the second sensing waveguide (4), the widths of the three side-by-side silicon waveguides are all 300 nm.

4. The silicon photonics chip temperature sensor according to any one of claims 1 to 3, characterized in that, in the second sensing waveguide (4), the spacing between adjacent silicon waveguides is 150 nm.

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