CN115508627B - Silicon-based waveguide electric field sensor chip based on slit racetrack microring and measurement method - Google Patents
Silicon-based waveguide electric field sensor chip based on slit racetrack microring and measurement method Download PDFInfo
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Abstract
本发明实施例公开了一种基于狭缝跑道型微环的硅基波导电场传感芯片及测量方法，芯片包括：自下而上设置的硅衬底层、埋氧层和硅刻蚀层，硅刻蚀层包括干涉结构和微环结构；干涉结构包括马赫曾德尔型调制波导和位于马赫曾德尔型调制波导输入和输出两侧的耦合光栅波导，光刻胶覆盖于马赫曾德尔型调制波导上；微环结构包括从外向内设置的跑道型微环外环波导和跑道型微环内环波导，两个波导之间具有狭缝，电光聚合物薄膜覆盖于微环结构上且将狭缝填充；马赫曾德尔型调制波导的一侧调制臂与跑道型微环外环波导的部分重叠。本发明通过优化微环结构和引入狭缝聚合物波导，解决了输出功率小，耦合不到位的问题，有效提升了传感芯片的线性度与灵敏度。
The embodiment of the present invention discloses a silicon-based waveguide electric field sensor chip based on a slit racetrack type microring and a measurement method. The chip includes: a silicon substrate layer, a buried oxide layer and a silicon etching layer arranged from bottom to top, the silicon etching layer includes an interference structure and a microring structure; the interference structure includes a Mach-Zehnder type modulation waveguide and a coupling grating waveguide located on both sides of the input and output of the Mach-Zehnder type modulation waveguide, and a photoresist covers the Mach-Zehnder type modulation waveguide; the microring structure includes a racetrack type microring outer ring waveguide and a racetrack type microring inner ring waveguide arranged from outside to inside, a slit is provided between the two waveguides, an electro-optic polymer film covers the microring structure and fills the slit; a modulation arm on one side of the Mach-Zehnder type modulation waveguide overlaps part of the racetrack type microring outer ring waveguide. The present invention solves the problems of low output power and inadequate coupling by optimizing the microring structure and introducing a slit polymer waveguide, and effectively improves the linearity and sensitivity of the sensor chip.
Description
Technical Field
The invention relates to the technical field of silicon-based optical waveguide electric field sensing, in particular to a silicon-based optical waveguide electric field sensing chip based on a slit runway type micro-ring and a measuring method.
Background
With the continuous expansion of the power grid scale and transmission capacity in China, the power grid is expected to perform comprehensive and accurate sensing and efficient transmission on big data through a ubiquitous small micro intelligent sensor which is highly fused with power equipment in the future so as to realize safe, reliable and efficient operation of the intelligent power grid under complex networks and conditions. However, although the traditional electromagnetic and capacitive electric field sensing equipment can realize real-time sensing and measurement of electric equipment and key nodes, most of the traditional electromagnetic and capacitive electric field sensing equipment has the defects of small amplitude measurement range, narrow frequency band measurement range, large volume, complex sensing structure, easiness in electromagnetic interference, high fault probability and the like due to the defects of the structure, and has limited application scenes.
An optical electric field sensor is a novel sensor for information transmission by using optical fibers, and monitors electric field signals existing in space through light intensity changes in optical waveguides on a substrate. Unlike electron transport, which may be disturbed by surrounding magnetic fields, photon transport has a higher transmission rate, a larger bandwidth, a faster response speed and a stronger anti-interference capability. The silicon-based optical waveguide electric field sensor adopting the advanced integrated optical technology and the electro-optic material can limit optical signals in a dielectric material with the size of the optical wavelength order, and realize low-loss connection of an integrated optical waveguide chip and an external device through efficient coupling with optical fibers, so that the sensor has the advantages of simple sensing structure, light weight, small volume after integration, wide output range, high measurement precision and wider application space and development prospect. However, at present, a good solution is not found in the problems of difficult integration of auxiliary devices, high requirements of manufacturing processes, nonlinear distortion of a modulation structure and the like, so that the application of the sensor is blocked, and large-area popularization cannot be realized.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a silicon-based waveguide electric field sensing chip based on a slit runway type micro-ring and a measuring method thereof, which solve the problems of small sensing output power and not in-place structure coupling of the same type in the past by optimizing a micro-ring auxiliary structure and introducing a slit polymer waveguide, and obtain the electric field sensing chip with high linearity, high precision, microminiaturization and wide frequency band.
The embodiment of the invention provides a silicon-based waveguide electric field sensing chip based on a slit runway type micro-ring, which comprises the following components:
The device comprises a silicon substrate layer, an oxygen burying layer and a silicon etching layer which are arranged from bottom to top, wherein the silicon etching layer comprises an interference structure and a micro-ring structure;
The interference structure comprises a Mach-Zehnder type modulation waveguide and coupling grating waveguides positioned on the input side and the output side of the Mach-Zehnder type modulation waveguide, wherein photoresist covers the Mach-Zehnder type modulation waveguide;
The micro-ring structure comprises a runway-type micro-ring outer ring waveguide and a runway-type micro-ring inner ring waveguide which are arranged from outside to inside, a slit is arranged between the runway-type micro-ring outer ring waveguide and the runway-type micro-ring inner ring waveguide, and an electro-optic polymer film covers the micro-ring structure and fills the slit;
one side modulation arm of the Mach-Zehnder type modulation waveguide is overlapped with part of the runway type micro-ring outer ring waveguide;
The effective refractive index of the electro-optic polymer film is changed under the action of an electric field to be measured, the effective refractive index of the micro-ring structure is changed, and the phase response output by the micro-ring structure enables the optical paths of the Mach-Zehnder type modulation waveguide double arms to generate a phase difference so as to realize measurement of the electric field to be measured.
As a further improvement of the present invention, a part of light enters the micro-ring structure through the coupling of the mach-zehnder type modulation waveguide, and the light intensity output by the sensing chip is as follows:
Wherein, I out is the light intensity output by the sensing chip, I in is the light intensity input by the sensing chip, T is the transfer function of the interference structure, phi R is the phase response of the micro-ring structure, theta is the phase change of the micro-ring structure, a is the transmission loss coefficient of the micro-ring structure, and k is the coupling coefficient of the micro-ring structure.
As a further improvement of the present invention, the phase response of the micro-ring structure is:
wherein a is a transmission loss coefficient of the micro-ring structure, k is a coupling coefficient of the micro-ring structure, and θ is a phase change of the micro-ring structure;
Wherein n eff is the effective refractive index in the micro-ring structure, delta n is the variation of the refractive index in the micro-ring structure, L is the perimeter of the slit, and lambda is the wavelength of light in vacuum.
As a further improvement of the present invention, in the micro-ring structure, the track-type micro-ring outer ring waveguide and the track-type micro-ring inner ring waveguide have the following field intensity relationship with the light in the slit:
Wherein E si is the electric field intensity at the interface of the runway-type micro-ring outer ring waveguide and the runway-type micro-ring inner ring waveguide, E p is the electric field intensity at the interface of the slit, n si is the refractive index of the runway-type micro-ring outer ring waveguide and the runway-type micro-ring inner ring waveguide, and n p is the refractive index of the electro-optic polymer film in the slit.
As a further improvement of the invention, the Mach-Zehnder type modulated waveguide has the width of 400nm, the radius of curvature of 499.6-500 mu m and the thickness of 220nm;
The thickness of the coupling grating waveguide is 110nm.
As a further improvement of the invention, the widths of the runway type micro-ring outer ring waveguide and the runway type micro-ring inner ring waveguide are 200nm, the thicknesses are 220nm, the radiuses of semicircles on two sides are 10um, and the lengths of the runways are 7um;
The width of the slit is 100nm, and the thickness is 220nm.
As a further improvement of the invention, the width of the overlapping area of the modulation arm and the runway type micro-ring outer ring waveguide is 150nm.
As a further improvement of the present invention, the electro-optic polymer film has a thickness of 2 μm to 4 μm.
As a further improvement of the invention, the electro-optic polymer film is prepared by taking an FTC chromophore and a PMMA polymer as solutes and tetrahydrofuran as solvents, and the electro-optic polymer film has an electro-optic effect by corona polarization.
The embodiment of the invention also provides a measuring method of the silicon-based waveguide electric field sensing chip based on the slit runway type micro-ring, which comprises the following steps:
the sensing chip is placed in the middle of a flat electrode, and the coupling grating waveguide is respectively coupled with the conical bare optical fibers at the output end of the polarization controller and the input end of the photoelectric detector at a certain vertical inclination angle;
transmitting light emitted by the laser source to the polarization controller through a single-mode fiber to form TE base mode polarized light, wherein the TE base mode polarized light is coupled into the sensing chip through a conical bare fiber;
applying voltage to the plate electrode through a high-voltage source, generating an electric field to be detected in the middle of the plate electrode, wherein the effective refractive index of the electro-optic polymer film is changed under the action of the electric field to be detected;
the optical field inside the micro-ring structure is fused with the electro-optic polymer film, and the effective refractive index of the micro-ring structure is changed, so that the optical paths of the double arms of the Mach-Zehnder type modulation waveguide generate phase differences;
and detecting the light intensity output by the sensing chip through the photoelectric detector, wherein the output light intensity represents the electric field to be detected.
The beneficial effects of the invention are as follows:
The runway type micro-ring waveguide is adopted, so that the coupling length between the interference structure and the micro-ring structure is increased, the binding capacity of the polymer waveguide to the light field is enhanced by utilizing the slit principle, and the light field and the electro-optic material are fused highly, thereby improving the linearity and the sensitivity of the sensing chip, and realizing accurate and sensitive measurement of the electric field to be measured.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is evident that the figures in the following description are only some embodiments of the invention, from which other figures can be obtained without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a silicon-based waveguide electric field sensor chip based on a slit racetrack micro-ring according to an exemplary embodiment of the invention;
FIG. 2 is a schematic plan view of a silicon-based waveguide electric field sensing chip based on a slit racetrack micro-ring shown in FIG. 1;
fig. 3 is a schematic diagram of a measurement device for measuring a silicon-based waveguide electric field sensor chip based on a slit racetrack micro-ring according to an exemplary embodiment of the invention.
In the drawing the view of the figure,
1. A silicon substrate layer; 2. an oxygen burying layer; 3. a silicon etching layer; 4. Mach-Zehnder modulated waveguides; 5. coupling a grating waveguide; 6. a racetrack-type micro-ring outer ring waveguide; 7. a racetrack-type micro-ring annular waveguide; 8. a photoresist; 9. an electro-optic polymer film; 10. a slit; 11. a modulating arm; 12. a laser source; 13. a polarization controller; 14. a plate electrode; 15. a photodetector; 16. an oscilloscope; 17. a high voltage amplifier 18, a function generator; 19. a tapered bare fiber; 20. a single mode optical fiber; 21. and a sensor chip.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and rear … …) are included in the embodiments of the present invention, the directional indications are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.
In addition, in the description of the present invention, the terminology used is for the purpose of illustration only and is not intended to limit the scope of the present invention. The terms "comprises" and/or "comprising" are used to specify the presence of stated elements, steps, operations, and/or components, but do not preclude the presence or addition of one or more other elements, steps, operations, and/or components. The terms "first," "second," and the like may be used for describing various elements, do not represent a sequence, and are not intended to limit the elements. Furthermore, in the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more. These terms are only used to distinguish one element from another element. These and/or other aspects will become apparent to those skilled in the art from the following description, when taken in conjunction with the accompanying drawings, wherein the present invention is described in connection with embodiments thereof. The drawings are intended to depict embodiments of the invention for purposes of illustration only. Those skilled in the art will readily recognize from the following description that alternative embodiments of the illustrated structures and methods of the present invention may be employed without departing from the principles of the present invention.
The embodiment of the invention provides a silicon-based waveguide electric field sensing chip based on a slit runway type micro-ring, as shown in fig. 1 and 2, the sensing chip comprises:
the silicon substrate layer 1, the oxygen-buried layer 2 and the silicon etching layer 3 are arranged from bottom to top, wherein the silicon etching layer 3 comprises an interference structure and a micro-ring structure, and the interference structure is a Mach-Zehnder interference structure;
the interference structure comprises a Mach-Zehnder type modulation waveguide 4 and coupling grating waveguides 5 positioned at the input side and the output side of the Mach-Zehnder type modulation waveguide 4, wherein photoresist 8 covers the Mach-Zehnder type modulation waveguide 4;
The micro-ring structure comprises a runway-type micro-ring outer ring waveguide 6 and a runway-type micro-ring inner ring waveguide 7 which are arranged from outside to inside, a slit 10 is arranged between the runway-type micro-ring outer ring waveguide 6 and the runway-type micro-ring inner ring waveguide 7, and an electro-optic polymer film 9 covers the micro-ring structure and fills the slit 10;
one side modulation arm 11 of the Mach-Zehnder type modulation waveguide 4 is overlapped with a part of the runway type micro-ring outer ring waveguide 6; it can be understood that the partial overlap can reduce the distance between the mach-zehnder type modulation waveguide 4 and the micro-ring structure, so as to improve the coupling coefficient of the micro-ring structure;
the effective refractive index of the electro-optic polymer film 9 is changed under the action of an electric field to be measured, the effective refractive index of the micro-ring structure is changed, and the phase response output by the micro-ring structure enables the optical paths of the two arms of the Mach-Zehnder type modulation waveguide 4 to generate a phase difference so as to realize the measurement of the electric field to be measured.
The invention realizes electric field sensing under micro-nano scale by utilizing SOI (silicon on insulator) integration technology and photon transmission method, and optical transmission structures (namely Mach-Zehnder type modulation waveguide 4, coupling grating waveguide 5, runway type micro-ring outer ring waveguide 6 and runway type micro-ring inner ring waveguide 7) are all completed by adopting silicon-based etching technology, and electro-optic material is prepared by adopting liquid spin coating with film forming property (namely electro-optic polymer film 9). The whole sensing chip does not need an external optimizing device, the manufacturing cost of the sensing chip is greatly reduced, the volume of the sensing chip is effectively reduced, and the sensing chip can realize passive non-contact information sensing in a narrow space area while considering high sensitivity and wide dynamic measurement range.
The sensing chip adopts the runway type micro-ring waveguide (the runway type micro-ring outer ring waveguide 6 and the runway type micro-ring inner ring waveguide 7), increases the coupling length between the interference structure and the micro-ring structure, enhances the binding capacity of the polymer waveguide (the electro-optic polymer film 9) to the light field by utilizing the slit principle, ensures that the light field is highly fused with the electro-optic material, and improves the output power of the sensing chip, thereby improving the linearity and the sensitivity of the sensing chip and realizing the accurate and sensitive measurement of the electric field to be measured.
The thickness of the silicon substrate layer 1 is 200-300 mu m, the buried oxide layer 2 is made of silicon dioxide, and the waveguides (namely the Mach-Zehnder modulation waveguide 4, the coupling grating waveguide 5, the runway type micro-ring outer ring waveguide 6 and the runway type micro-ring inner ring waveguide 7) of the silicon etching layer 3 are manufactured by adopting an EBL electron beam exposure technology.
Wherein the Mach-Zehnder modulated waveguide 4 has a width of 400nm, a radius of curvature of 499.6 μm to 500 μm, and a thickness of 220nm.
The coupling grating waveguides 5 are located at two sides of the mach-zehnder modulated waveguide 4, and are used for coupling the single-mode optical fiber with low loss when the measurement is performed by the measuring device shown in fig. 3, and the depth of the coupling grating waveguide 5 is 110nm.
Wherein the racetrack-type micro-ring outer ring waveguide 6 and the racetrack-type micro-ring inner ring waveguide 7 operate in an over-coupling state (coupling coefficient of 0.96), the width of the two semi-circles is 200nm, the thickness of the two semi-circles is 220nm, the radius of the semi-circles on both sides is 10um, and the length of the runway is 7um. The slit 10 between the inner ring and the outer ring has a width of 100nm and a depth of 220nm.
Wherein, the width of the overlapping area of the modulation arm 11 at one side of the Mach-Zehnder type modulation waveguide 4 and the runway type micro-ring outer ring waveguide 6 is 150nm.
The thickness of the photoresist is 2 mu m and covers the whole Mach-Zehnder modulation waveguide, but does not cover the slit between the coupling grating waveguide and the runway type micro-ring waveguide. The photoresist is used for isolating the Mach-Zehnder modulation waveguide and the electro-optic polymer film, so that the electro-optic polymer film only acts on the micro-ring structure. Alternatively, SU8 is used as the photoresist, and is not limited to SU8, but other near ultraviolet-like and nonconductive photoresists are also possible.
The electro-optic polymer film 9 uses FTC chromophore (namely second order nonlinear optical chromophore, alkylaniline donor thieno polyene conjugated electron bridge tricyanofuran acceptor chromophore) and PMMA polymer as solute, the doping concentration of the FTC chromophore in the PMMA polymer in the solute is 30%, tetrahydrofuran is used as solvent, the solution of the solute and the solvent after stirring and filtering is obtained after spin-coating on a sensing chip by a spin coater with the rotating speed of 4300r/min, the solution is placed in a drying box for drying for 24h, corona polarization is carried out, the electro-optic effect is achieved, a heater is used for heating to the temperature near 160 ℃ of the vitrification temperature of the polymer film, and after 9KV direct current voltage is applied for 1min, the temperature is gradually reduced, and the polarization state is kept until the normal temperature. The refractive index of the spin-coating electro-optic polymer film 9 is lower than 3.42, and the thickness is 2-4 μm. After the electro-optic polymer film 9 is spin-coated, the slit between the inner ring and the outer ring is filled with electro-optic polymer material, and the change of the effective refractive index and the linear change of the externally applied electric field cause the output light intensity change after Mach-Zehnder structure interference to be still linearly related to the electric field to be measured, so as to realize the measurement of the electric field to be measured.
In one embodiment, part of the light enters the micro-ring structure through the coupling of the mach-zehnder type modulation waveguide 4, and the light intensity output by the sensing chip is as follows:
Wherein, I out is the light intensity output by the sensing chip, I in is the light intensity input by the sensing chip, T is the transfer function of the interference structure, phi R is the phase response of the micro-ring structure, theta is the phase change of the micro-ring structure, a is the transmission loss coefficient of the micro-ring structure, and k is the coupling coefficient of the micro-ring structure.
In one embodiment, the phase response of the micro-ring structure is:
wherein a is a transmission loss coefficient of the micro-ring structure, k is a coupling coefficient of the micro-ring structure, and θ is a phase change of the micro-ring structure;
Wherein n eff is the effective refractive index in the micro-ring structure, delta n is the variation of the refractive index in the micro-ring structure, L is the perimeter of the slit, and lambda is the wavelength of light in vacuum.
From the above, the phase response output by the micro-ring structure can offset the inherent sine function third-order nonlinearity of the interference structure while the two arms of the interference structure generate a phase difference, so that increasing the coupling length of the Mach-Zehnder interference structure and the micro-ring structure can effectively improve the coupling coefficient of the micro-ring structure, enable the micro-ring structure to be in an over-coupling state, and realize the high-linearity output of the sensing chip.
In one embodiment, in the micro-ring structure, the track-type micro-ring outer ring waveguide and the track-type micro-ring inner ring waveguide have the following field intensity relationship with the light in the slit 10:
Wherein E si is the electric field intensity at the interface of the racetrack-type micro-ring outer ring waveguide and the racetrack-type micro-ring inner ring waveguide, E p is the electric field intensity at the interface of the slit 10, n si is the refractive index of the racetrack-type micro-ring outer ring waveguide and the racetrack-type micro-ring inner ring waveguide, and n p is the refractive index of the electro-optic polymer film 9 in the slit 10.
The racetrack type micro-ring outer ring waveguide and the racetrack type micro-ring inner ring waveguide are both silicon waveguides, and it is understood that in the field intensity relation, the electric field intensity at the interface of the racetrack type micro-ring outer ring waveguide and the electric field intensity at the interface of the racetrack type micro-ring inner ring waveguide are both E si, and the refractive index of the racetrack type micro-ring outer ring waveguide and the refractive index of the racetrack type micro-ring inner ring waveguide are both n si. The racetrack type micro-ring outer ring waveguide and the racetrack type micro-ring inner ring waveguide are hereinafter referred to as two side waveguides of the slit.
From the above field strength relation, it is known from the slit principle that the electro-optic polymer material with low refractive index and high electro-optic coefficient can cause the abrupt change of the photoelectric field at the waveguide interface within a certain width limit, and the slit is filled with the high electro-optic material with low refractive index (for example, 1.6), so that the optical fields in the waveguides at both sides of the slit are overlapped towards the middle (i.e., towards the slit). At this time, most of energy is limited in the polymer of the slit, so that the electro-optic material and the optical field are fully coupled, the overall effective refractive index variation of the micro-ring structure is increased (i.e. the effective refractive index difference of the micro-ring structure is increased), and the accuracy of the sensing chip is improved.
The embodiment of the invention provides a measuring method of a silicon-based waveguide electric field sensing chip based on a slit runway type micro-ring, which is a passive non-contact measuring method. The measuring device used is shown in fig. 3, and includes: the laser source 12, the polarization controller 13, the flat electrode 14, the photodetector 15, the oscilloscope 16, the high-voltage amplifier 17, the function generator 18, the tapered bare fiber 19, the single-mode fiber 20 and the sensing chip 21, and the sensing chip 21 is shown in fig. 1 and 2.
Wherein the laser source 12 is 1550nm laser source. The output of the laser source 12 is connected to the input of the polarization controller 13 via a single-mode fiber 20.
The sensor chip 21 needs to be placed in the middle of the plate electrode 14. The upper surface of the plate electrode 14 is connected to the output terminal of the high voltage amplifier 17, and the lower surface of the plate electrode 14 is grounded.
The output end of the polarization controller 13 is connected to the input end of the coupling grating waveguide 5 of the sensor chip 21 through a tapered bare fiber 19, and the tapered bare fiber 19 is inclined so that the input end of the coupling grating waveguide 5 is coupled to the tapered bare fiber 19 at a vertical inclination angle (the vertical inclination angle is preferably within 15 ° to 30 °, for example, 20 ° -vertical inclination angle). The vertical tilt angle ensures that the single mode optical fiber is transported in TE mode. The output end of the coupling grating waveguide 5 of the sensing chip 21 is connected with the input end of the photodetector 15 through the tapered bare fiber 19, and the tapered bare fiber 19 is obliquely arranged so that the output end of the coupling grating waveguide 5 and the tapered bare fiber 19 are coupled at a certain vertical oblique angle (for example, 20 ° vertical oblique angle).
The function generator 18 and the high voltage amplifier 17 serve as a high voltage source to apply a voltage to the flat electrode 14. The function generator 18 generates a voltage as required and applies it to the plate electrode 14 after amplification by the high voltage amplifier 17.
The photodetector 15 is used to detect the light intensity output by the coupling grating waveguide 5 (i.e., the light intensity output by the sensor chip), and display the output light intensity through the oscilloscope 16.
With the measuring device, in the measuring process, the method comprises the following steps:
S1, placing the sensing chip 21 in the middle of a flat electrode, and respectively coupling the coupling grating waveguide 5 with the conical bare optical fiber 19 at the output end of the polarization controller and the input end of the photoelectric detector at a certain vertical inclination angle;
S2, transmitting light emitted by the laser source 12 to the polarization controller 13 through the single-mode optical fiber 20, and converting the light into TE base mode polarized light, wherein the TE base mode polarized light is coupled into the sensing chip 21 through the conical bare optical fiber 19 at the output end of the polarization controller 13;
S3, the function generator 18 generates voltage according to the requirement, the voltage amplified by the high-voltage amplifier 17 is applied to the flat plate electrode 14, after the voltage is applied, an electric field to be detected is generated in the inner space of the flat plate electrode 14, and the refractive index of the electro-optic polymer film 8 is changed;
S4, the optical field inside the micro-ring structure is fused with the electro-optic polymer film 9, and at the moment, the effective refractive index of the micro-ring structure is changed, so that the optical paths of the two arms of the Mach-Zehnder type modulation waveguide 4 generate phase differences;
S5, after interference, the photoelectric detector 15 is used for detecting the light intensity output by the sensing chip 21, the output light intensity represents the electric field to be measured, and the oscillograph 16 is used for reading the waveform representing the electric field to be measured, so that the measurement of the electric field to be measured is realized.
The light intensity output by the sensor chip 21 is denoted by I out in the foregoing embodiment, and will not be described herein. It can be seen that, based on the photoelectric conversion principle, the sensor chip 21 can realize passive non-contact measurement of the electric field to be measured, and the runway micro-ring waveguide and the slit structure effectively enhance the coupling effect between the light field and each waveguide, so that the linearity and the sensitivity of the sensor chip are improved, and accurate and sensitive measurement of the electric field to be measured is realized.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Furthermore, one of ordinary skill in the art will appreciate that while some embodiments described herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.
It will be understood by those skilled in the art that while the invention has been described with reference to exemplary embodiments, various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. A silicon-based waveguide electric field sensing chip based on a slit runway type micro-ring is characterized in that the sensing chip comprises:
The device comprises a silicon substrate layer, an oxygen burying layer and a silicon etching layer which are arranged from bottom to top, wherein the silicon etching layer comprises an interference structure and a micro-ring structure;
The interference structure comprises a Mach-Zehnder type modulation waveguide and coupling grating waveguides positioned on the input side and the output side of the Mach-Zehnder type modulation waveguide, wherein photoresist covers the Mach-Zehnder type modulation waveguide;
The micro-ring structure comprises a runway-type micro-ring outer ring waveguide and a runway-type micro-ring inner ring waveguide which are arranged from outside to inside, a slit is arranged between the runway-type micro-ring outer ring waveguide and the runway-type micro-ring inner ring waveguide, and an electro-optic polymer film covers the micro-ring structure and fills the slit;
one side modulation arm of the Mach-Zehnder type modulation waveguide is overlapped with part of the runway type micro-ring outer ring waveguide;
The effective refractive index of the electro-optic polymer film is changed under the action of an electric field to be measured, the effective refractive index of the micro-ring structure is changed, and the phase response output by the micro-ring structure enables the optical paths of the Mach-Zehnder type modulation waveguide double arms to generate a phase difference so as to realize measurement of the electric field to be measured.
2. The sensor chip of claim 1, wherein a portion of the light is coupled into the micro-ring structure via the mach-zehnder modulated waveguide, and the light output by the sensor chip is:
Wherein, I out is the light intensity output by the sensing chip, I in is the light intensity input by the sensing chip, T is the transfer function of the interference structure, phi R is the phase response of the micro-ring structure, theta is the phase change of the micro-ring structure, a is the transmission loss coefficient of the micro-ring structure, and k is the coupling coefficient of the micro-ring structure.
3. The sense die of claim 2, wherein the phase response of the micro-ring structure is:
wherein a is a transmission loss coefficient of the micro-ring structure, k is a coupling coefficient of the micro-ring structure, and θ is a phase change of the micro-ring structure;
Wherein n eff is the effective refractive index in the micro-ring structure, delta n is the variation of the refractive index in the micro-ring structure, L is the perimeter of the slit, and lambda is the wavelength of light in vacuum.
4. The sensor chip of claim 1, wherein in the micro-ring structure, the racetrack type micro-ring outer ring waveguide and the racetrack type micro-ring inner ring waveguide have the following field strength relationship with the light in the slit:
Wherein E si is the electric field intensity at the interface of the runway-type micro-ring outer ring waveguide and the runway-type micro-ring inner ring waveguide, E p is the electric field intensity at the interface of the slit, n si is the refractive index of the runway-type micro-ring outer ring waveguide and the runway-type micro-ring inner ring waveguide, and n p is the refractive index of the electro-optic polymer film in the slit.
5. The sensor chip of claim 1, wherein the mach-zehnder modulated waveguide has a width of 400nm, a radius of curvature of 499.6 μm to 500 μm, and a thickness of 220nm;
The thickness of the coupling grating waveguide is 110nm.
6. The sensor chip of claim 1, wherein the racetrack micro-ring outer ring waveguide and the racetrack micro-ring inner ring waveguide each have a width of 200nm, a thickness of 220nm, a radius of 10um on each side of the semicircle, and a racetrack length of 7um;
The width of the slit is 100nm, and the thickness is 220nm.
7. The sensor chip of claim 1, wherein the width of the overlap region of the modulation arm and the racetrack micro-ring outer ring waveguide is 150nm.
8. The sensor chip of claim 1, wherein the electro-optic polymer film has a thickness of 2 μm to 4 μm.
9. The sensing chip of claim 1 or 8, wherein the electro-optic polymer film is prepared by taking an FTC chromophore and a PMMA polymer as solutes and tetrahydrofuran as a solvent, and the electro-optic polymer film is subjected to corona polarization to have an electro-optic effect.
10. A method for measuring a slit racetrack micro-ring based silicon-based waveguide electric field sensor chip as defined in any one of claims 1-9, comprising:
the sensing chip is placed in the middle of the flat electrode, and the coupling grating waveguide is respectively coupled with the conical bare optical fibers at the output end of the polarization controller and the input end of the photoelectric detector at a certain vertical inclination angle;
transmitting light emitted by the laser source to the polarization controller through a single-mode fiber to form TE base mode polarized light, wherein the TE base mode polarized light is coupled into the sensing chip through a conical bare fiber;
applying voltage to the plate electrode through a high-voltage source, generating an electric field to be detected in the middle of the plate electrode, wherein the effective refractive index of the electro-optic polymer film is changed under the action of the electric field to be detected;
The optical field inside the micro-ring structure is fused with the electro-optic polymer film, and the effective refractive index of the micro-ring structure is changed, so that the optical paths of the double arms of the Mach-Zehnder modulation waveguide generate phase differences;
and detecting the light intensity output by the sensing chip through the photoelectric detector, wherein the output light intensity represents the electric field to be detected.
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