CN116930629B - Electric field sensing device and method - Google Patents
Electric field sensing device and method Download PDFInfo
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- 230000005684 electric field Effects 0.000 title claims abstract description 112
- 238000000034 method Methods 0.000 title claims abstract description 40
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims abstract description 169
- 239000010409 thin film Substances 0.000 claims abstract description 149
- 239000000523 sample Substances 0.000 claims abstract description 69
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- 238000001312 dry etching Methods 0.000 claims description 8
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- UMIVXZPTRXBADB-UHFFFAOYSA-N benzocyclobutene Chemical compound C1=CC=C2CCC2=C1 UMIVXZPTRXBADB-UHFFFAOYSA-N 0.000 claims description 3
- 239000004038 photonic crystal Substances 0.000 claims description 3
- 230000035945 sensitivity Effects 0.000 abstract description 21
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- 230000001052 transient effect Effects 0.000 description 2
- 238000002834 transmittance Methods 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/12—Measuring electrostatic fields or voltage-potential
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
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- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The application provides an electric field sensing device and a method. The device comprises: the measuring system and the sensing probe made of the film lithium niobate are connected through optical fibers; the sensing probe comprises a thin-film lithium niobate annular waveguide, a thin-film lithium niobate straight waveguide, a thin-film lithium niobate flat plate, a buffer layer and a supporting material, wherein the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide form a resonant cavity; the measuring system is used for outputting a laser signal with the frequency locked to the resonant frequency of the resonant cavity to the sensing probe and receiving an optical signal output after passing through the resonant cavity; the measuring system is also used for converting the optical signal into an electric signal and acquiring the movement of the resonance peak of the resonant cavity in the frequency direction according to the electric signal; and calculating the change value of the external electric field according to the movement of the resonance peak of the resonant cavity in the frequency direction. The device can improve the sensitivity of the electric field sensor, reduce the volume of the device and increase the environmental stability of the electric field sensor.
Description
Technical Field
The present disclosure relates to the field of optical electric field sensing technologies, and in particular, to an electric field sensing device and method.
Background
Electric field sensing plays an irreplaceable role in both academic and industrial fields, and the increasingly complex space electromagnetic field environment makes it very difficult to accurately and rapidly measure electric fields. The optical electric field sensor has the advantages of wide frequency band, quick response, electro-optical isolation, non-invasiveness, anti-interference and other electric field sensing methods which are incomparable, and is one of the most important means in the field of electric field sensing.
In the prior art, an electric field sensing device is mainly made of a bulk lithium niobate material, and a lithium niobate optical electric field sensor is mainly based on a Mach-Zehnder interference structure, a Michelson interference structure or a common-path interference structure and the like.
However, in order to improve the sensitivity of the device, the existing lithium niobate optical electric field sensor can prolong the length of the waveguide, which brings about the increase of the size of the device, and can also cause the mismatch of the speed of light waves transmitted by the waveguide and microwaves transmitted by the electrode, thereby reducing the bandwidth of the device. In addition, the transfer functions of the sensor are cosine functions, and 90-degree static working points are needed to be realized through the design of the length or the width of the waveguide, so that the cosine functions are changed into sine functions, and a linear working area of the sensor is obtained, but the static working points are difficult to accurately reach 90 degrees due to the manufacturing process errors of the sensor; and after the sensor is manufactured, the working point of the sensor is easily deviated from a linear working area due to the influence of ambient temperature, vibration and the like, so that the measurement accuracy and the measurement range are influenced, and even the sensor cannot work.
Disclosure of Invention
The application provides an electric field sensing device and method, which are used for solving the problems that an optical sensor in the prior art is not high enough in sensitivity, is easily influenced by external environment factors (such as temperature and vibration), and is large in device size because of prolonging the waveguide length in order to improve the sensitivity.
In a first aspect, the present application provides an electric field sensing device, including a measurement system and a sensing probe made of thin film lithium niobate, where the measurement system is connected with the sensing probe through an optical fiber;
the sensing probe at least comprises a thin-film lithium niobate annular waveguide, a thin-film lithium niobate straight waveguide, a thin-film lithium niobate flat plate, a buffer layer and a supporting material, wherein the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide form a resonant cavity, the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide are arranged on the thin-film lithium niobate flat plate, and the buffer layer and the supporting material are sequentially arranged under the thin-film lithium niobate flat plate;
the measuring system is used for outputting a frequency-locked laser signal to the sensing probe and receiving an optical signal output after passing through the resonant cavity, and the frequency of the laser signal is locked to the resonant frequency of the resonant cavity;
the measuring system is also used for converting the optical signal into an electric signal and acquiring the electric field intensity of the position where the sensing probe is located according to the electric signal.
In one possible design of the first aspect, the measurement system comprises: an adjustable laser, a phase modulator, a microwave source, a mixer, a high-speed optical detector, a T-type bias device, a servo motor, a signal generator, a frequency spectrograph or an oscilloscope;
The adjustable laser outputs laser signals to the phase modulator through optical fibers;
the phase modulator outputs the laser signal to the sensing probe through an optical fiber;
the high-speed optical detector receives an optical signal output by the sensing probe through an optical fiber and converts the optical signal into an electric signal P;
the mixer is used for mixing an output signal M of the microwave source with the electric signal P to obtain an output signal L and outputting the output signal L to the T-type biaser;
the T-shaped biaser is used for splitting the output signal L into a direct current signal D and a radio frequency signal R, the direct current signal D is used for being input to the servo motor, and the radio frequency signal R is used for being input to the spectrometer or the oscilloscope;
the servo motor is used for performing proportional-integral-differential control according to the direct current signal D to obtain an output signal S and feeding the output signal S back to the adjustable laser, and the output signal S is used for locking the frequency of the adjustable laser;
the servo motor is also used for generating an output signal D 'and inputting the output signal D' into the oscilloscope;
the microwave source is used for inputting an output signal M to the phase modulator;
the signal generator is used for inputting an output signal F to the tunable laser, and the output signal F is used for frequency modulation of the tunable laser;
The frequency spectrograph is used for carrying out frequency domain measurement according to the radio frequency signal R;
the oscilloscope is used for carrying out time domain measurement according to the radio frequency signal R, and is also used for outputting the difference between the frequencies of the tunable laser and the resonant cavity according to the output signal D'.
In another possible design of the first aspect, the frequency of the output signal M of the microwave source is 1 ghz to 10 ghz or much larger than the linewidth of the resonant cavity.
In a further possible design of the first aspect, the microwave source is further configured to output a frequency-tuned output signal M for compensating for a delay of phases of two signals input into the mixer;
or alternatively, the first and second heat exchangers may be,
the measurement system further includes: one end of the phase shifter is connected with the microwave source, and the other end of the phase shifter is connected with the mixer;
the phase shifter is used for compensating the delay of the phases of two signals input into the mixer.
In yet another possible design of the first aspect, the tunable laser is an external cavity diode laser or a distributed feedback laser or a fiber laser.
In yet another possible design of the first aspect, the sensing probe further comprises: the thickness of the electrode pair is 40-1000 nanometers, and the distance between the electrode pair and the thin film lithium niobate annular waveguide is 1.5-10 micrometers;
If the thin film lithium niobate is x-cut or y-cut, the electrode pairs are arranged on two sides of the thin film lithium niobate annular waveguide, and the electrode pairs are connected with the antenna in a wire bonding mode, wherein the number of the electrode pairs is one pair or more than two pairs, when the number of the electrode pairs is one pair, the electrode pairs are arranged on two sides of the half perimeter of the thin film lithium niobate annular waveguide, and when the number of the electrode pairs is two pairs, the electrode pairs are arranged on two sides of the full perimeter of the thin film lithium niobate annular waveguide;
and if the thin film lithium niobate is z-cut, the electrode pair is arranged above and below the whole circumference of the thin film lithium niobate annular waveguide, and the electrode pair is connected with the antenna by a wire bonding mode.
In a further possible design of the first aspect, the dry etching of the thin film lithium niobate is deepThe degree is 200-600 nanometers, the width of the thin film lithium niobate annular waveguide is 0.8-3.5 micrometers, the radius of the thin film lithium niobate annular waveguide is 80-200 micrometers, the coupling distance between the thin film lithium niobate annular waveguide and the thin film lithium niobate straight waveguide is 400-1000 nanometers, and the quality factor of the resonant cavity is 1 multiplied by 10 5 ~2×10 6 。
In yet another possible design of the first aspect, the buffer layer is silicon dioxide or benzocyclobutene.
In yet another possible design of the first aspect, the structure of the resonant cavity may be replaced by a photonic crystal type or a bragg grating type.
In a second aspect, the present application provides an electric field sensing method, applied to an electric field sensing device, where the electric field sensing device includes a measurement system and a sensing probe made of thin film lithium niobate, and the measurement system is connected with the sensing probe through an optical fiber; the sensing probe at least comprises a thin-film lithium niobate annular waveguide, a thin-film lithium niobate straight waveguide, a thin-film lithium niobate flat plate, a buffer layer and a supporting material, wherein the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide form a resonant cavity, the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide are arranged on the thin-film lithium niobate flat plate, and the buffer layer and the supporting material are sequentially arranged under the thin-film lithium niobate flat plate, and the method comprises the following steps:
locking the frequency of a laser signal output by an adjustable laser in the measuring system to the resonant frequency of the resonant cavity;
when the sensing probe is in an external electric field environment to be detected, outputting a frequency-locked laser signal to a resonant cavity of the sensing probe;
Acquiring an optical signal fed back by a resonant cavity of the sensing probe and converting the optical signal into an electric signal;
according to the electric signal, the movement of a resonance peak of the resonant cavity in the frequency direction is obtained;
and calculating the change value of the external electric field according to the movement of the resonance peak of the resonant cavity in the frequency direction.
According to the electric field sensing device and method, the resonant cavity is formed by the thin-film lithium niobate straight waveguide and the thin-film lithium niobate annular waveguide, so that the interaction time of an optical field and an external electric field is prolonged, the sensitivity of the electric field sensor is improved, and the volume is reduced. Meanwhile, the sensing probe is connected with the measuring system through the optical fiber, so that the measuring system can be far away from a measured electric field, only the sensing probe is arranged in the measured electric field, the interference on the original field is reduced, and the sensing system is not influenced by electromagnetic signals of the measured electric field. In addition, by locking the frequency of the adjustable laser in the measuring system, the environmental stability of the electric field sensing device is increased, so that the electric field sensing device can work in a non-laboratory environment and is not influenced by environmental temperature, vibration and the like.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.
Fig. 1 is a schematic diagram of a frame structure of an electric field sensing device according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of a sensing probe in the electric field sensing device according to the embodiment of the present application;
FIG. 3 is a normalized transmission spectrum waveform of a ring resonator provided in an embodiment of the present application;
FIG. 4 is a schematic structural diagram of an electric field sensing device according to another embodiment of the present disclosure;
FIG. 5 is a schematic diagram of a system frame of a measurement system according to an embodiment of the present application;
FIG. 6A is a schematic view of an electrode position according to an embodiment of the present disclosure;
FIG. 6B is a schematic view of an electrode position according to another embodiment of the present application;
FIG. 6C is a schematic view of an electrode position according to another embodiment of the present disclosure;
FIG. 6D is a schematic view of an electrode position according to another embodiment of the present disclosure;
fig. 7 is a schematic flow chart of an electric field sensing method according to an embodiment of the present application;
fig. 8 is a schematic diagram of a sensing system radio frequency signal R of a spectrometer according to an embodiment of the present application;
fig. 9 is a graph of normalization of the output signal R and the applied voltage signal of the sensing system obtained by the oscilloscope according to the embodiment of the present application.
Specific embodiments thereof have been shown by way of example in the drawings and will herein be described in more detail. These drawings and the written description are not intended to limit the scope of the inventive concepts in any way, but to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments.
Detailed Description
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples are not representative of all implementations consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with some aspects of the present application as detailed in the accompanying claims.
It should be noted that, in the description of the embodiments of the present application, terms such as "inner", "outer", and the like, refer to directions or positional relationships based on the directions or positional relationships shown in the drawings, which are merely for convenience of description, and do not indicate or imply that the apparatus or component must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application.
Furthermore, it should be noted that, in the description of the embodiments of the present application, unless explicitly specified and limited otherwise, the terms "connected," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be the communication between the two components. The specific meaning of the above terms in the embodiments of the present application will be understood by those skilled in the art according to the specific circumstances.
Optical electric field sensing is generally adoptedThe linear electro-optic effect of the bulk lithium niobate crystal is realized. The bulk lithium niobate wafer is used for manufacturing the optical waveguide by a titanium diffusion or proton exchange process, and the refractive index difference between the waveguide and the cladding thereof is small (10 -2 ~10 -3 ) The waveguide size is large (10 μm magnitude), which is unfavorable for miniaturization and integration of the device, and influences the sensitivity and other performances of the device. Based on the defects of the traditional optical electric field sensor, in recent years, a thin film lithium niobate wafer with the thickness of hundred nanometers appears and is rapidly commercialized, a micro-nano processing technology is mature gradually, a thin film lithium niobate waveguide obtained by dry etching has the characteristics of high refractive index difference (0.7-1) and low transmission loss, the waveguide limits an optical field to the width from micrometers to submicron, and the method provides possibility for manufacturing a thin film lithium niobate resonant cavity with high quality factor and compact size.
The existing lithium niobate optical electric field sensor is mainly based on Mach-Zehnder interference structures, michelson interference structures or common-path interference structures and the like, and still has the following problems: (1) The sensitivity of the device is positively correlated with the length of the electro-optic modulation region of the waveguide, which is typically in the order of centimeters in order to increase the sensitivity, which on the one hand results in an increase in the device size, and on the other hand results in a mismatch in the speed of the light wave transmitted by the waveguide and the microwaves transmitted by the electrode, reducing the bandwidth of the device. (2) The transfer functions of the sensor are cosine functions, and a 90-degree static working point is required to be realized through the design of the length or the width of the waveguide, so that the cosine functions are changed into sine functions, and a linear working area of the sensor is obtained, but the static working point is difficult to accurately reach 90 degrees due to the manufacturing process error of the sensor; and after the sensor is manufactured, the working point of the sensor is easily deviated from a linear working area due to the influence of ambient temperature, vibration and the like, so that the measurement accuracy and the measurement range are influenced, and even the sensor cannot work. (3) Current methods for improving sensor environmental stability include: the negative thermo-optic coefficient material is used for compensating the positive thermo-optic coefficient of lithium niobate, so that the steady-state temperature stability is improved; the end face of the chip is plated with a conductive film to improve transient temperature stability; the transient temperature stability is improved by the methods of thinning the chip, changing the beveling direction of the end face of the chip and the like; and monitoring the intensity change or the partial derivative change of the output light power to obtain the drift condition of the working point of the sensor, and controlling the working point of the sensor through an active method feedback. The passive method has limited improvement effect, the active method can introduce interference to the original field at the electric field measuring end, and the active compensation circuit is also extremely easy to be influenced by the original field, so that the possibility of instability of the measuring system is increased.
In view of the above, the present application provides an electric field sensing apparatus and method capable of achieving high sensitivity and environmental stability. Specifically, the resonant cavity is formed by the thin-film lithium niobate straight waveguide and the thin-film lithium niobate annular waveguide, so that the interaction time of an optical field and an external electric field is prolonged, the sensitivity of the electric field sensor is improved, and the volume is reduced. Meanwhile, the sensing probe is connected with the measuring system through the optical fiber, so that the measuring system can be far away from a measured electric field, only the sensing probe is arranged in the measured electric field, the interference on the original field is reduced, and the sensing system is not influenced by electromagnetic signals of the measured electric field. In addition, by locking the frequency of the adjustable laser in the measuring system, the environmental stability of the electric field sensing device is increased, so that the electric field sensing device can work in a non-laboratory environment and is not influenced by environmental temperature, vibration and the like.
The following describes the technical scheme of the present application in detail through specific embodiments. It should be noted that the following embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.
Fig. 1 is a schematic diagram of a frame structure of an electric field sensing device according to an embodiment of the present application, and as shown in fig. 1, an electric field sensing device 10 is divided into a sensing probe 101 and a measurement system 102. Wherein the sensing probe 101 is connected with the measuring system 102 through an optical fiber. When measuring the electric field intensity, the sensing probe 101 is in the measured electric field, and the measuring system can be far away from the measured electric field as far as possible through the optical fiber (the length of the optical fiber between the sensing probe 101 and the measuring system 102 can be set), generally, the farther the measuring system is away from the measured electric field, the smaller the interference on the original field is, and meanwhile, the influence of electromagnetic signals of the measured electric field can be avoided, so that the measuring accuracy is improved.
Specifically, fig. 2 is a schematic structural diagram of a sensing probe in an electric field sensing device provided in an embodiment of the present application, as shown in fig. 2, the sensing probe at least includes a thin film lithium niobate annular waveguide 21, a thin film lithium niobate straight waveguide 22, a thin film lithium niobate flat plate 23, a buffer layer 24 and a supporting material 25, the thin film lithium niobate annular waveguide 21 and the thin film lithium niobate straight waveguide 22 form a resonant cavity, the thin film lithium niobate annular waveguide 21 and the thin film lithium niobate straight waveguide 22 are disposed on the thin film lithium niobate flat plate 23, and the buffer layer 24 and the supporting material 25 are disposed under the thin film lithium niobate flat plate 23.
In this embodiment, the sensing probe is made of a thin film lithium niobate material on an insulator, and light in the thin film lithium niobate straight waveguide 22 is coupled into the thin film lithium niobate annular waveguide 21 through an evanescent field, and light in the thin film lithium niobate annular waveguide 21 is coupled out again. When the phase change generated by one light propagation cycle in the thin film lithium niobate ring waveguide 21 becomes an integer multiple of 2pi, the optical interference in the thin film lithium niobate ring waveguide 21 is constructive and the optical power is greatly enhanced. Can be described by the following formula:
（1）
in the above-mentioned method, the step of,the neff is the effective refractive index of the thin film lithium niobate annular waveguide, L is the annular circumference, and N is a positive integer. Wherein, the light wave is input from one end of the thin film lithium niobate straight waveguide 22, and the transmission spectrum received by the other end can be described by the following formula:
（2）
In the above formula, T is the transmittance, T is the self-coupling coefficient at the coupling region of the thin film lithium niobate annular waveguide 21 and the thin film lithium niobate straight waveguide 22, a and d are the transmission loss and the phase change of light transmitted in the thin film lithium niobate annular waveguide 21 for one week, respectively, and i is a constant.
Fig. 3 is a normalized transmission spectrum waveform of the ring resonator according to the embodiment of the present application, as shown in fig. 3, and two adjacent resonance peaks are shown in fig. 3. FSR is the free spectral range, and is the wavelength or frequency difference between two adjacent resonant peaks. FWHM is the full width at half maximum, characterizing the wavelength or frequency width at half the resonance peak, i.e. the linewidth of the cavity.
Illustratively, with continued reference to FIG. 2 above, a buffer layer 24 is disposed between the support material 25 and the thin film lithium niobate slab 23. The buffer layer 24 is a bonding buffer layer, and may be silicon dioxide, benzocyclobutene, and the support material 25 may be lithium niobate, silicon, quartz, or the like.
In this embodiment, when the external electric field is changed, the refractive index of the lithium niobate material is changed due to the linear electro-optic effect, and the resonance peak is shifted by the above formula (1).
Wherein the quality factor Q of the resonant cavity L Is defined as:
In the above, when the quality factor Q L The larger the FWHM is, the smaller the slope |dT/dλ| on the side of the resonance peak is, the higher the sensor sensitivity is, where T is the transmittance and λ represents the wavelength. The lithium niobate waveguide can be stably obtained by dry etching to obtain 1×10 6 Quality factor Q of the order of magnitude L 。
Further, in other embodiments, the structure of the resonant cavity may be replaced by a photonic crystal type or a bragg grating type. When the resonant cavity is in a Bragg grating structure, the resonant cavity is formed by a straight strip-shaped thin film lithium niobate waveguide. Further, when the resonator has a bragg grating structure, electrode pairs and antennas may be disposed on both sides of the straight strip-shaped thin film lithium niobate waveguide to enhance sensitivity.
In this embodiment, the resonant cavity is configured in a ring shape, so that the volume of the resonant cavity is as small as possible, the size of the sensing probe part is reduced, and the manufacturing process is simple, so that the manufacturing is more convenient. In addition, in other embodiments, the resist patterning step of the resonator structure may be achieved by a photolithography or electron beam exposure process.
FIG. 4 is a schematic structural diagram of an electric field sensing device according to another embodiment of the present application, where, as shown in FIG. 4, a measurement system is connected to a sensing probe through an optical fiber; the measuring system at least comprises a laser signal transmitting assembly, an optical signal processing assembly, a measuring result output assembly and a frequency adjusting assembly, wherein the measuring system adjusts the frequency of the laser signal through the frequency adjusting assembly to lock the frequency of the laser signal, outputs the laser signal to the sensing probe through the laser signal transmitting assembly, and receives the optical signal which is output after passing through the resonant cavity of the sensing probe through the optical signal processing assembly; the optical signal output after passing through the resonant cavity of the sensing probe is converted into an electric signal, and the electric field intensity of the sensing probe at the position is output according to the electric signal. Wherein the frequency of the laser signal may be locked to the resonant frequency of the resonant cavity. Specifically, fig. 5 is a schematic diagram of a system frame of a measurement system according to an embodiment of the present application, where, as shown in fig. 5, a dashed line represents an optical signal, and a solid line represents an electrical signal. The frequency locking process of the laser signal can be specifically as follows: (1) Coarsely adjusting the frequency of a laser signal output by an adjustable laser in a measuring system to be near the resonant frequency of a resonant cavity; (2) Adjusting the frequency of the output signal M of the microwave source to enable the output signal M to be matched with the electric signal P in phase; (3) The frequency of the laser signal output by the tunable laser in the fine tuning measurement system is locked to the resonant frequency of the resonant cavity.
In this embodiment, the sensing probe has a resonant cavity structure, the resonant cavity structure is implemented based on a lithium niobate material, and the lithium niobate material has an electro-optical effect, and when an external electric field exists, the refractive index of the lithium niobate material changes, so that a corresponding resonance peak of the resonant cavity moves in frequency, and the change amount of the external electric field can be reversely pushed by measuring the movement.
The sensing probe is mainly used for sensing external electric field signals, and the measuring system reversely pushes out the variation of the external electric field according to the optical signals fed back by the sensing probe to realize electric field sensing.
According to the embodiment of the application, the high-quality factor thin film lithium niobate resonant cavity is adopted, the size of the resonant cavity of the sensing probe part is only hundred micrometers, compared with the centimeter-level waveguide size of a Mach-Zehnder interference structure, a Michelson interference structure or a common-path interference structure and the like, the sensing probe is more compact in size, the resonant cavity structure is adopted, the interaction time of an optical field and an external measured electric field is increased, the sensitivity of an electric field sensing device is improved, and the external measured electric field is obtained by comparing the difference between the resonant frequency of the resonant cavity and the laser locking frequency, so that electric field sensing is realized. And static working points are not required to be set, so that the influence of process errors is avoided. Meanwhile, the optical signals input and output by the sensing probe are transmitted through the optical fiber, the whole measuring system is far away from the sensing probe and the measured electric field, photoelectric isolation is realized, no interference is caused to the original field, and the influence of the original field electromagnetic signals is avoided.
In some embodiments, a measurement system includes: an adjustable laser, a phase modulator, a microwave source, a mixer, a high-speed optical detector, a T-type bias device, a servo motor, a signal generator, a frequency spectrograph or an oscilloscope; the adjustable laser outputs a laser signal to the phase modulator through the optical isolator; the phase modulator outputs a laser signal to the sensing probe through the polarization maintaining fiber; the high-speed optical detector receives an optical signal output by the sensing probe through a single-mode optical fiber and converts the optical signal into an electric signal P; the mixer is used for mixing an output signal M of the microwave source with an electric signal P to obtain an output signal L and outputting the output signal L to the T-type biaser; the T-type bias device is used for splitting an output signal L into a direct current signal D and a radio frequency signal R, wherein the direct current signal D is used for being input to the servo motor, and the radio frequency signal R is used for being input to the spectrometer or the oscilloscope; the servo motor is used for performing proportional-integral-derivative control (PID) according to the direct current signal D to obtain an output signal S which is fed back to the tunable laser, wherein the output signal S is used for locking the frequency of the tunable laser; in addition, the servo motor can also perform proportional-integral control (PI) according to the direct current signal D to obtain an output signal S and feed back the output signal S to the tunable laser; the servo motor is also used for generating an output signal D 'and inputting the output signal D' into the oscilloscope; the microwave source is used for inputting an output signal M to the phase modulator; the signal generator is used for inputting an output signal F to the adjustable laser, and the output signal F is used for frequency modulation of the adjustable laser; the frequency spectrograph is used for carrying out frequency domain measurement according to the radio frequency signal R; the oscilloscope is used for carrying out time domain measurement according to the radio frequency signal R, and is also used for outputting the frequency difference between the tunable laser and the resonant cavity according to the output signal D'.
In other embodiments, an optical isolator may be disposed between the tunable laser and the phase modulator, and the laser signal output from the tunable laser enters the phase modulator through the optical isolator. With continued reference to fig. 5 above, the laser light is output from the tunable laser through an optical fiber to a phase modulator, and an optical isolator is used to prevent light reflected back from the phase modulator from entering the tunable laser.
The light passing through the phase modulator can be input into a resonant cavity in the sensing probe through the polarization maintaining optical fiber, and then output from the resonant cavity in the sensing probe through the single mode optical fiber, and the light is converted into an electric signal by the high-speed optical detector. In addition, the light passing through the phase modulator can also be input to the resonant cavity in the sensing probe through a single mode fiber and a polarization controller.
One path of output signal M of the microwave source drives a phase modulator to perform phase modulation on laser output; the other path is input to the LO port of the mixer. The high-speed photodetector outputs an electrical signal P that is input to the RF port of the mixer. After the electric signal P is mixed with the output signal M, an output signal L of the mixer IF port is obtained. The output signal L is divided into a direct current signal D and a radio frequency signal R by a T-type bias device, wherein the direct current signal D is input into a servo motor to obtain an output signal S through PID adjustment, and finally fed back and input into an adjustable laser for locking the frequency of the adjustable laser; the radio frequency signal R is input into a frequency spectrograph for frequency domain measurement or an oscilloscope for time domain measurement, and an external measured electric field signal is obtained. The output signal F of the signal generator is used to control the fine frequency modulation of the tunable laser. The direct current signal D input to the servo motor can be monitored by the output signal D ' of an ' input error ' port of the servo motor and is input into an oscilloscope for observing the difference between the resonant frequencies of the tunable laser and the resonant cavity in the sensing probe.
In the present embodimentDue to the modulation frequency of the microwave source outputFar larger than the line width of the resonant cavity, so that only the carrier frequency of the tunable laser output is +.>Enters a resonant cavity to modulate sideband->Without entering the cavity. When the external measured electric field exists, the resonant cavity is formed by the frequency of +>Is phase modulated by an external measured electric field to generate sidebands->. Four sidebandsAnd->The frequency of the light generated in the high-speed light detector is +.>Is a heterodyne signal of (a). These heterodyne signals are +.>After mixing of the microwave source at a frequency +.>The measured electric field signal is obtained.
Therefore, in order to derive the transfer function of the system, the sidebands need to be analyzedAnd->。
Light field of incident light after passing through phase modulatorIs that
（4-1）
In the above-mentioned method, the step of,is the (angular) frequency of the laser source (i.e. tunable laser), t is time,/is>Modulation frequency output to the phase modulator for the microwave source,/->Is the modulation depth.
The equation (4-1) is developed by the Bessel function, and when the modulation depth is small, the term is retained only once:
（4-2）
wherein,，/>the incident light frequency carrier is modulated to generate two frequency sidebands for the Bessel function of the first kind. Due to the side band->The light field in the output waveguide after the cavity is discharged is as follows:
（4-3）
Due to the side bandWithin the cavity, its amplitude and phase are affected by the cavity mode response. By frequency of +.>The evolution equation of the optical field in the resonator of the continuous laser pump is:
（4-4）
in the above formula, A is the envelope of the light field in the cavity, t is time,for the difference between the resonance frequencies of the pump laser and the resonator, < >>For the total loss rate of the resonator, including intrinsic loss rate +.>And external coupling ratio，/>For the time of one week light propagates in the resonator, < > for>Is the frequency shift of the resonance peak due to the phase modulation of the measured electric field.
Fourier transforming the formula (4-4) to obtain:
（4-5）
in the above-mentioned method, the step of,is->Fourier transform of->Is->Related frequency, +.>Is a dirac function. After solving, obtaining the laser frequency locked at the resonant frequency of the resonant cavity, and outputting the corresponding optical field as follows:
（4-7）
side bandAfter the cavity is discharged, the corresponding light fields are respectively as follows:
（4-8）
（4-10）
the total optical field in the output waveguide after cavity exit is:
（4-11）
the electrical signal P output by the high-speed photodetector is:
（4-12）
in the above-mentioned method, the step of,the conversion coefficient of the high-speed photodetector is expressed as V/W. Side band->Frequency +.>Mixing and filtering by a T-type bias device to obtain the frequency +.>The radio frequency signal R at the position is:
（4-13）
in the above, the total conversion coefficient Sequentially comprises extra-cavity phase modulation +.>Detector conversion factor->Mixer conversion factor->And electro-optical modulation efficiency +.>Influence of (1)>For the outside measured electric field, +.>Is a phase change.
The equation (4-13) is a transfer function between the system output voltage and the external measured electric field, and the measured electric field is obtained through the change of the system output voltage.
According to the embodiment of the application, the electric field sensing and the frequency locking of the laser are realized by adopting the thin film lithium niobate resonant cavity structure, the resonant cavity increases the interaction time of an optical field and an external electric field, the sensitivity of the electric field sensor is improved, and the volume is reduced. Meanwhile, the frequency of the adjustable laser is locked in the sensing system, so that the environmental stability of the electric field sensing device is improved, the electric field sensing device can work in a non-laboratory environment and is not influenced by environmental temperature, vibration and the like, the intensity noise of the adjustable laser is restrained, and the signal to noise ratio of the electric field sensing device is improved.
In some embodiments, the frequency of the output signal M of the microwave source is 1 ghz to 10 ghz or much greater than the linewidth of the resonant cavity.
In this embodiment, the more the frequency of the output signal M of the microwave source exceeds the linewidth of the resonant cavity, the higher the sensitivity of the electric field sensing device.
In some embodiments, the measurement system further comprises: one end of the phase shifter is connected with the microwave source, and the other end of the phase shifter is connected with the mixer; the phase shifter is used to compensate for the delay of the phases of the two signals input into the mixer.
In other embodiments, the frequency of the microwave source may be directly changed to equalize the phases of the two input signals of the mixer without adding a phase shifter.
In some embodiments, the tunable laser is an external cavity diode laser or a distributed feedback laser or a fiber laser.
In some embodiments, the sensing probe further comprises: the thickness of the electrode pair and the antenna is 40-1000 nanometers, and the distance between the electrode pair and the thin film lithium niobate annular waveguide is 1.5-10 micrometers;
if the thin film lithium niobate is x-cut or y-cut, the electrode pairs are arranged at two sides of the thin film lithium niobate annular waveguide, the electrode pairs are connected with the antenna in a wire bonding mode, wherein the number of the electrode pairs is one or more than two pairs, when the number of the electrode pairs is one pair, the electrode pairs are arranged at two sides of the half perimeter of the thin film lithium niobate annular waveguide, and when the number of the electrode pairs is two pairs, the electrode pairs are arranged at two sides of the full perimeter of the thin film lithium niobate annular waveguide;
If the thin film lithium niobate is z-cut, the electrode pair is disposed above and below the entire circumference of the annular waveguide, and the electrode pair is connected to the antenna by wire bonding.
In this embodiment, in the field of optical electric field sensing technology, x-cut, y-cut and z-cut are three different wafer cutting methods.
For example, for x-cut thin film lithium niobate, fig. 6A is a schematic diagram of the electrode positions provided in the embodiment of the present application, as shown in fig. 6A, on a thin film lithium niobate flat plate, a pair of electrodes 61 and 62 are fabricated on two sides of a half perimeter of a thin film lithium niobate annular waveguide 60, a resonant cavity is formed by a thin film lithium niobate straight waveguide 63 and the thin film lithium niobate annular waveguide 60, and the electrodes can be connected with on-chip antennas at other positions by a wire bonding manner, so as to further improve the sensitivity and directionality of the electric field sensor. Further, for the x-cut thin film lithium niobate, fig. 6B is a schematic diagram of the electrode positions provided in another embodiment of the present application, as shown in fig. 6B, a pair of electrodes 611 and 621 are fabricated on two sides of the full perimeter of the thin film lithium niobate annular waveguide 60 on the thin film lithium niobate flat plate, the thin film lithium niobate straight waveguide 63 and the thin film lithium niobate annular waveguide 60 form a resonant cavity, and the electrodes can be connected with on-chip antennas at other positions by a wire bonding manner, so as to further improve the sensitivity and directionality of the electric field sensor.
For example, for y-cut thin film lithium niobate, fig. 6C is a schematic diagram of electrode positions provided in another embodiment of the present application, as shown in fig. 6C, a pair of electrodes 612 and 622 are fabricated on two sides of a half perimeter of the thin film lithium niobate annular waveguide 60 on a thin film lithium niobate flat plate, the thin film lithium niobate straight waveguide 63 and the thin film lithium niobate annular waveguide 60 form a resonant cavity, and the electrodes can be connected with on-chip antennas at other positions by a wire bonding manner, so as to further improve sensitivity and directionality of the electric field sensor. Further, for y-cut thin film lithium niobate, fig. 6D is a schematic diagram of electrode positions provided in another embodiment of the present application, as shown in fig. 6D, a pair of electrodes 613 and 623 are fabricated on two sides of the full perimeter of the thin film lithium niobate annular waveguide 60 on a thin film lithium niobate flat plate, the thin film lithium niobate straight waveguide 63 and the thin film lithium niobate annular waveguide 60 form a resonant cavity, and the electrodes can be connected with on-chip antennas at other positions by wire bonding, so as to further improve the sensitivity and directionality of the electric field sensor.
The difference between the x-cut and the y-cut of the thin film lithium niobate is that coordinate axes are marked differently, the coordinate axes represent the crystal orientation of the lithium niobate crystal, and the different coordinate axes are marked differently. In addition, when two electrode pairs are provided, the polarities of the inner and outer electrodes of the two electrode pairs are opposite.
In this embodiment, the different cutting methods are mainly to use the largest linear electro-optic coefficient component γ33 of lithium niobate, and the x-cut electrodes of the thin film lithium niobate are disposed on two sides of the thin film lithium niobate annular waveguide, and the z-cut electrodes of the thin film lithium niobate are disposed above and below the thin film lithium niobate annular waveguide.
In this embodiment, the antenna may be an antenna structure such as a dipole antenna or a junction antenna; the number of the electrode pairs can be one or two, and the two pairs of electrodes can realize sensing by utilizing the circumference of the whole thin film lithium niobate annular waveguide, so that the maximum linear electro-optic coefficient component gamma 33 of lithium niobate is utilized to the maximum extent.
In other embodiments, the sensor probe may be used as an all-dielectric electric field sensor without providing a metal electrode, thereby reducing distortion of the measured electric field.
According to the embodiment of the application, the sensitivity and the directivity of the electric field sensor are further improved by arranging the electrodes and the antennas.
In some embodiments, the dry etching depth of the thin film lithium niobate is 200-600 nanometers, the width of the thin film lithium niobate annular waveguide is 0.8-3.5 micrometers, the radius of the thin film lithium niobate annular waveguide is 80-200 micrometers, the coupling distance between the thin film lithium niobate annular waveguide and the thin film lithium niobate straight waveguide is 400-1000 nanometers, and the quality factor of the resonant cavity is 1×10 5 ~2×10 6 。
In the embodiment, the thin film lithium niobate waveguide obtained by dry etching has the characteristics of high refractive index difference (0.7-1) and low transmission loss. The dry etching of the lithium niobate waveguide can stably obtain 1×10 6 Quality factor Q of the order of magnitude L While the quality factor Q L The larger the FWHThe smaller M, the greater the slope |dT/dλ| on the side of the resonance peak, the higher the sensor sensitivity.
Fig. 7 is a schematic flow chart of an electric field sensing method according to an embodiment of the present application, where the electric field sensing method may be applied to the electric field sensing device mentioned in the foregoing embodiment, and as shown in fig. 7, the electric field sensing method may specifically include the following steps:
step S701, coarsely adjusting the frequency of the laser signal output by the tunable laser in the measurement system to be near the resonant frequency of the resonant cavity.
In step S702, the frequency of the signal M output by the microwave source is adjusted to match the phases of the signal M and the signal P.
In step S703, the frequency of the laser signal output by the tunable laser in the measurement system is finely tuned, and locked to the resonant frequency of the resonant cavity.
Step S704, when the sensing probe is in the external electric field environment, acquiring an optical signal fed back by the resonant cavity of the sensing probe and converting the optical signal into an electric signal.
Step S705, according to the electric signal, the movement of the resonance peak of the resonant cavity in the frequency direction is obtained.
Step S706, calculating the external electric field variation value according to the movement of the resonance peak of the resonant cavity in the frequency direction.
In this embodiment, based on the above-mentioned fig. 2, the structure of the whole electric field sensing device is as follows: the sensing probe is made of a thin film lithium niobate wafer, and comprises a thin film lithium niobate flat plate 23, a buffer layer 24 (for example, silicon dioxide material) and a supporting material 25 (for example, high-resistance silicon). Illustratively, the tangential direction of lithium niobate is x-cut, and the direction of light propagation in the thin film lithium niobate straight waveguide 22 is along the y-direction. The crystal coordinate system is shown as the coordinate axes in fig. 2. The resonant cavity structure (comprising the thin-film lithium niobate annular waveguide 21 and the thin-film lithium niobate straight waveguide 22) is manufactured through a resist patterning and dry etching process, the etching depth is 300 nanometers, the width of the thin-film lithium niobate annular waveguide 21 is 2.5 micrometers, the radius of the thin-film lithium niobate annular waveguide 21 is 100 micrometers, and the coupling distance between the thin-film lithium niobate annular waveguide 21 and the thin-film lithium niobate straight waveguide 22 is 600 nanometers. By testing the transmission spectrum of the resonant cavityCan obtain Q thereof L =1×10 6 At 1550 nm wavelength, the linewidth of the cavity is 193.5 mhz.
Based on fig. 6A, electrode pairs 61 and 62 were fabricated by photolithography, metal evaporation and lift-off processes, the thickness of the electrode was 500 nm, and the distance between the electrode and the thin film lithium niobate ring waveguide was 3 μm. The electrode shape is shown in FIG. 6A, and the largest linear electro-optic coefficient component gamma of lithium niobate is utilized through a single electrode pair to the maximum extent 33 。
Wherein the measurement system is shown in fig. 5. The tunable laser frequency is coarsely tuned to around the resonant frequency of the resonant cavity. The signal generator outputs a triangular wave signal F with the frequency of 50 Hz and the peak-to-peak value of 3V, and the tunable laser is subjected to fine frequency sweep. The frequency of the output signal M of the microwave source is 3 GHz, which is far greater than the line width 193.5 MHz of the resonant cavity. The 3 dB bandwidth of the phase modulator is 40 gigahertz, and the 3 dB bandwidth of the high frequency detector is 10 gigahertz. The frequency of the output signal M of the microwave source is finely adjusted so that the output signal M is matched with the electric signal P in phase.
At this point, the servo motor is operated in an unlocked state and an output signal D' is observed on the oscilloscope, representing the difference between the tunable laser frequency and the resonant frequency of the resonant cavity. And (3) turning off the output signal F of the signal generator, finely adjusting the frequency of the adjustable laser, and locking the servo motor when the output signal D' is zero-crossing observed on the oscilloscope, wherein the frequency of the adjustable laser is locked on the resonant frequency of the resonant cavity.
Fig. 8 is a schematic diagram of a sensing system radio frequency signal R of a spectrometer according to an embodiment of the present application. As shown in fig. 8, when the frequency of the external measured electric field signal is 100 mhz, the spectrometer obtains the sensing system rf signal R.
Fig. 9 is a graph of normalization of a sensing system radio frequency signal R and an applied voltage signal obtained by the oscilloscope according to the embodiment of the present application. As shown in fig. 9, when the applied voltage signal is a waveform of a modulated wave with a frequency of 500 khz and a carrier wave with a frequency of 15 mhz, and a measured electric field signal is generated, the curve of the normalization of the radio frequency signal R and the applied voltage signal is obtained by the oscilloscope. Because the frequency of the tunable laser is locked, the electric field sensing device is not affected by the changes of low-frequency physical quantities such as ambient temperature, vibration and the like.
In this embodiment, with continued reference to fig. 5, the dc signal D is input to the servo motor, and the output signal S is obtained by PID adjustment, and finally fed back to the tunable laser for frequency locking of the tunable laser.
According to the embodiment of the application, the frequency of the adjustable laser is locked in the test system, so that the environmental stability of the whole electric field sensing device is improved, the electric field sensing device can work in a non-experimental environment, and the influence of environmental temperature, vibration and the like is avoided.
The electric field sensing method provided in this embodiment may be applied to the foregoing device embodiment, and its implementation principle and technical effects are similar, and will not be described in detail.
In the present application, "at least one" means one or more, and "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a alone, a and B together, and B alone, wherein a, B may be singular or plural. The character "/" generally indicates that the front and rear associated objects are an "or" relationship; in the formula, the character "/" indicates that the front and rear associated objects are a "division" relationship. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (one) of a, b, or c may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, c may be single or plural.
It will be appreciated that the various numerical numbers referred to in the embodiments of the present application are merely for ease of description and are not intended to limit the scope of the embodiments of the present application. In the embodiments of the present application, the sequence number of each process does not mean the sequence of execution sequence, and the execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.
Claims (9)
1. The electric field sensing device is characterized by comprising a measuring system and a sensing probe made of thin film lithium niobate, wherein the measuring system is connected with the sensing probe through an optical fiber;
the sensing probe comprises a thin-film lithium niobate annular waveguide, a thin-film lithium niobate straight waveguide, a thin-film lithium niobate flat plate, a buffer layer and a supporting material, wherein the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide form a resonant cavity, the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide are arranged on the thin-film lithium niobate flat plate, and the buffer layer and the supporting material are sequentially arranged under the thin-film lithium niobate flat plate;
The measuring system is used for outputting a frequency-locked laser signal to the sensing probe and receiving an optical signal output after passing through the resonant cavity, and the frequency of the laser signal is locked to the resonant frequency of the resonant cavity;
the measuring system is also used for converting the optical signal into an electric signal and acquiring the electric field intensity of the position where the sensing probe is located according to the electric signal;
the measurement system includes: an adjustable laser, a phase modulator, a microwave source, a mixer, a high-speed optical detector, a T-type bias device, a servo motor, a signal generator, a frequency spectrograph or an oscilloscope;
the adjustable laser outputs laser signals to the phase modulator through optical fibers;
the phase modulator outputs the laser signal to the sensing probe through an optical fiber;
the high-speed optical detector receives an optical signal output by the sensing probe through an optical fiber and converts the optical signal into an electric signal P;
the mixer is used for mixing an output signal M of the microwave source with the electric signal P to obtain an output signal L and outputting the output signal L to the T-type biaser;
the T-shaped biaser is used for splitting the output signal L into a direct current signal D and a radio frequency signal R, the direct current signal D is used for being input to the servo motor, and the radio frequency signal R is used for being input to the spectrometer or the oscilloscope;
The servo motor is used for performing proportional-integral-differential control according to the direct current signal D to obtain an output signal S and feeding the output signal S back to the adjustable laser, and the output signal S is used for locking the frequency of the adjustable laser;
the servo motor is also used for generating an output signal D 'and inputting the output signal D' into the oscilloscope;
the microwave source is used for inputting an output signal M to the phase modulator;
the signal generator is used for inputting an output signal F to the tunable laser, and the output signal F is used for frequency modulation of the tunable laser;
the frequency spectrograph is used for carrying out frequency domain measurement according to the radio frequency signal R;
the oscilloscope is used for carrying out time domain measurement according to the radio frequency signal R, and is also used for outputting the difference between the frequencies of the tunable laser and the resonant cavity according to the output signal D'.
2. The apparatus of claim 1, wherein the frequency of the output signal M of the microwave source is 1 gigahertz to 10 gigahertz or much greater than the linewidth of the resonant cavity.
3. The apparatus of claim 1, wherein the microwave source is further configured to output a frequency-tuned output signal M for compensating for a delay in phases of two signals input to the mixer;
Or alternatively, the first and second heat exchangers may be,
the measurement system further includes: one end of the phase shifter is connected with the microwave source, and the other end of the phase shifter is connected with the mixer;
the phase shifter is used for compensating the delay of the phases of two signals input into the mixer.
4. The apparatus of claim 1, wherein the tunable laser is an external cavity diode laser or a distributed feedback laser or a fiber laser.
5. The apparatus of claim 1, wherein the sensing probe further comprises: the thickness of the electrode pair is 40-1000 nanometers, the distance between the electrode pair and the thin film lithium niobate annular waveguide is 1.5-10 micrometers, and the antenna has the structure of dipole antenna or junction antenna and other antenna structures;
if the thin film lithium niobate is x-cut or y-cut, the electrode pairs are arranged on two sides of the thin film lithium niobate annular waveguide, and the electrode pairs are connected with the antenna in a wire bonding mode, wherein the number of the electrode pairs is one pair or more than two pairs, when the number of the electrode pairs is one pair, the electrode pairs are arranged on two sides of the half perimeter of the thin film lithium niobate annular waveguide, and when the number of the electrode pairs is two pairs, the electrode pairs are arranged on two sides of the full perimeter of the thin film lithium niobate annular waveguide;
And if the thin film lithium niobate is z-cut, the electrode pair is arranged above and below the whole circumference of the thin film lithium niobate annular waveguide, and the electrode pair is connected with the antenna by a wire bonding mode.
6. The device of claim 1, wherein the dry etching depth of the thin film lithium niobate is 200 to 600 nanometers, the width of the thin film lithium niobate annular waveguide is 0.8 to 3.5 micrometers, and the radius of the thin film lithium niobate annular waveguide is 80 to 200 micrometersThe coupling distance between the thin film lithium niobate annular waveguide and the thin film lithium niobate straight waveguide is 400-1000 nanometers, and the quality factor of the resonant cavity is 1 multiplied by 10 5 ～2×10 6 。
7. The device of claim 1, wherein the buffer layer is silica or benzocyclobutene.
8. The device of claim 1, wherein the resonator structure is replaced by a photonic crystal type or a bragg grating type.
9. The electric field sensing method is characterized by being applied to an electric field sensing device, wherein the electric field sensing device comprises a measuring system and a sensing probe made of thin film lithium niobate, and the measuring system is connected with the sensing probe through an optical fiber; the sensing probe comprises a thin-film lithium niobate annular waveguide, a thin-film lithium niobate straight waveguide, a thin-film lithium niobate flat plate, a buffer layer and a supporting material, wherein the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide form a resonant cavity, the thin-film lithium niobate annular waveguide and the thin-film lithium niobate straight waveguide are arranged on the thin-film lithium niobate flat plate, and the buffer layer and the supporting material are sequentially arranged under the thin-film lithium niobate flat plate, and the method comprises the following steps:
Adjusting and locking the frequency of a laser signal output by an adjustable laser in the measuring system to the resonant frequency of the resonant cavity;
when the sensing probe is in an external electric field environment to be detected, outputting a frequency-locked laser signal to a resonant cavity of the sensing probe;
acquiring an optical signal fed back by a resonant cavity of the sensing probe and converting the optical signal into an electric signal;
according to the electric signal, the movement of a resonance peak of the resonant cavity in the frequency direction is obtained;
calculating an external electric field change value according to the movement of the resonance peak of the resonant cavity in the frequency direction;
the measurement system includes: an adjustable laser, a phase modulator, a microwave source, a mixer, a high-speed optical detector, a T-type bias device, a servo motor, a signal generator, a frequency spectrograph or an oscilloscope;
the adjustable laser outputs laser signals to the phase modulator through optical fibers;
the phase modulator outputs the laser signal to the sensing probe through an optical fiber;
the high-speed optical detector receives an optical signal output by the sensing probe through an optical fiber and converts the optical signal into an electric signal P;
the mixer is used for mixing an output signal M of the microwave source with the electric signal P to obtain an output signal L and outputting the output signal L to the T-type biaser;
The T-shaped biaser is used for splitting the output signal L into a direct current signal D and a radio frequency signal R, the direct current signal D is used for being input to the servo motor, and the radio frequency signal R is used for being input to the spectrometer or the oscilloscope;
the servo motor is used for performing proportional-integral-differential control according to the direct current signal D to obtain an output signal S and feeding the output signal S back to the adjustable laser, and the output signal S is used for locking the frequency of the adjustable laser;
the servo motor is also used for generating an output signal D 'and inputting the output signal D' into the oscilloscope;
the microwave source is used for inputting an output signal M to the phase modulator;
the signal generator is used for inputting an output signal F to the tunable laser, and the output signal F is used for frequency modulation of the tunable laser;
the frequency spectrograph is used for carrying out frequency domain measurement according to the radio frequency signal R;
the oscilloscope is used for carrying out time domain measurement according to the radio frequency signal R, and is also used for outputting the difference between the frequencies of the tunable laser and the resonant cavity according to the output signal D'.
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| CN116482802A (en) * | 2023-04-04 | 2023-07-25 | 北京航空航天大学 | Reflective optical electric field sensor based on lithium niobate thin film material |
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| JPH09171201A (en) * | 1995-12-20 | 1997-06-30 | Toyota Central Res & Dev Lab Inc | Opto-electronic integrated circuit and multipoint optical heterodyne measuring device |
| CN110161295A (en) * | 2019-04-30 | 2019-08-23 | 浙江大学 | A kind of probe and its Method of Adjustment of reflection type optical fiber electric-field sensor |
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