CN118067243A - Terahertz electromagnetic wave electro-optical measurement device and method - Google Patents
Terahertz electromagnetic wave electro-optical measurement device and method Download PDFInfo
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Abstract
The invention discloses a terahertz electromagnetic wave electro-optical measurement device and a method, in a specific implementation mode, the device mainly comprises: the device comprises a thin film lithium niobate substrate, a dielectric rod waveguide and a standard interface conversion waveguide, wherein the standard interface conversion waveguide is used for receiving terahertz electromagnetic waves to be detected and feeding the terahertz electromagnetic waves to the dielectric rod waveguide; the dielectric rod waveguide is used for transmitting the fed terahertz electromagnetic wave to the thin film lithium niobate substrate at a first angle; the thin film lithium niobate substrate is used for outputting laser pulses carrying terahertz electromagnetic waves to the photoelectric detector after the incident sampling laser pulses interact with the incident terahertz electromagnetic waves. The device has the advantages of greatly simplified optical system, no limitation to crystal materials, realization of the effect of the device with electro-optic crystals, large measurement bandwidth, high sensitivity and strong signal to noise ratio.
Description
Technical Field
The invention relates to the technical field of precision measurement. And more particularly, to an electro-optical measurement device and method for terahertz electromagnetic waves.
Background
At present, terahertz detection is the basis of the related research field of terahertz, is a key technology widely applied to terahertz technology, and at present, an electro-optical sampling technology based on a linear electro-optical effect has been proved to be a method for forcefully detecting pulsed terahertz wave radiation, and is widely applied to various national metering institutions.
In general, the conventional electro-optical sampling technology converges ultrafast femtosecond sampling light and terahertz electromagnetic waves on an electro-optical crystal at the same time, and an instantaneous electric field of the terahertz electromagnetic waves induces the refractive index of the electro-optical crystal to change anisotropically, so that the polarization state of a sampling light beam is changed from linear polarization to elliptical polarization, and the ellipsometry of the sampling light is detected by a balanced photoelectric detector, so that the measurement of the electric field of the terahertz electromagnetic waves is realized. However, the electro-optic coefficient of the electro-optic crystal is limited to be small, and the phase velocity mismatch of the transmission lighting group velocity and the terahertz wave velocity in the crystal is limited, so that the traditional electro-optic sampling technology based on polarization modulation not only has a narrow test bandwidth, but also has lower measurement sensitivity and signal-to-noise ratio on small signals when detecting the pulse terahertz wave. Therefore, there is an urgent need for a terahertz electromagnetic wave electro-optical measurement device with large bandwidth, high sensitivity and strong signal-to-noise ratio
The heterodyne electro-optic sampling technology based on the Cherenkov radiation principle realizes the measurement of the electric field of the terahertz electromagnetic wave by making the terahertz electromagnetic wave incident to the electro-optic crystal at the Cherenkov angle, carrying out electro-optic action with the sampling light propagated on the surface of the crystal, and detecting the light intensity change before and after the modulation of the sampling light intensity in the electro-optic crystal. The technology does not need any polarization optical device, compared with the traditional electro-optic sampling technology based on polarization modulation, the optical system is greatly simplified, the technology is not limited by a crystal material, can be realized by acting with an electro-optic crystal, has large measurement bandwidth, high sensitivity and strong signal-to-noise ratio, and has great reference value for researching the terahertz precise detection technology and application.
Disclosure of Invention
The invention aims to provide a terahertz electromagnetic wave electro-optical measurement device and a terahertz electromagnetic wave electro-optical measurement method, which are used for solving at least one of the problems existing in the prior art.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the first aspect of the present invention provides a terahertz electromagnetic wave electro-optical measurement apparatus, comprising:
A thin film lithium niobate substrate, a dielectric rod waveguide and a standard interface conversion waveguide,
The standard interface conversion waveguide is used for receiving terahertz electromagnetic waves to be detected and feeding the terahertz electromagnetic waves to the dielectric rod waveguide;
the dielectric rod waveguide is used for transmitting the fed terahertz electromagnetic waves to the thin film lithium niobate substrate at a preset first included angle;
the thin film lithium niobate substrate is used for outputting laser pulses carrying terahertz electromagnetic waves to the photoelectric detector after the incident sampling laser pulses interact with the incident terahertz electromagnetic waves.
Optionally, the first angle is a cerenkov angle.
Optionally, the dielectric rod waveguide comprises a coupling tip, a transmission section and a conversion tip which are sequentially connected;
the conversion tip is used for receiving the terahertz electromagnetic wave and transmitting the terahertz electromagnetic wave to the transmission section;
The transmission section is used for realizing the transformation of the transmission direction of the terahertz electromagnetic wave and transmitting the terahertz electromagnetic wave to the coupling tip;
and the coupling tip is used for coupling the received terahertz electromagnetic wave to be detected to the thin film lithium niobate substrate.
Optionally, the dielectric rod waveguide is made of silicon or GaAs semiconductor.
Optionally, the thin film lithium niobate substrate comprises a support layer, a lithium niobate slab layer and a lithium niobate ridge waveguide layer,
The optical axis direction of the lithium niobate crystal of the thin film lithium niobate substrate is the long side direction of the laser incident port surface; the material of the supporting layer is consistent with the material of the dielectric rod waveguide, and the lithium niobate slab layer and the lithium niobate ridge waveguide layer jointly form a thin film lithium niobate on-chip optical waveguide structure.
Optionally, the cross section of the optical waveguide on the thin film lithium niobate sheet is in a ridge structure.
Optionally, the coupling tip includes a first section and a second section, wherein a bottom surface of the first section is connected with the supporting layer of the thin film lithium niobate substrate, the second section is connected with the transmission section, and an included angle between the first section and the second section is a complementary angle of the cerenkov angle.
Optionally, the thick end of the conversion tip is connected with the bottom end of the transmission section, and the surface of the connection part is covered with a positioning strip; the width of the thin end of the conversion tip is linearly gradually changed; the thin end of the conversion tip is inserted into the through cavity in the standard interface waveguide, and the locking cavity of the standard interface waveguide is matched and locked with the locking block of the dielectric rod waveguide.
Optionally, the device is configured such that the polarization direction of the incident sampling light forms a preset first included angle with the optical axis of the lithium niobate crystal of the thin film lithium niobate substrate, and the polarization direction of the incident terahertz wave is parallel to the optical axis of the lithium niobate crystal of the thin film lithium niobate substrate.
The second aspect of the invention provides a terahertz electromagnetic wave electro-optical measurement method, which comprises the following steps:
The standard interface conversion waveguide receives terahertz electromagnetic waves to be detected and feeds the terahertz electromagnetic waves into the dielectric rod waveguide;
The dielectric rod waveguide transmits the fed terahertz electromagnetic wave to a thin film lithium niobate substrate at a preset first included angle;
The thin film lithium niobate substrate outputs laser pulses carrying terahertz electromagnetic waves to the photoelectric detector after the incident sampling laser pulses interact with the incident terahertz electromagnetic waves.
The beneficial effects of the invention are as follows:
Compared with the traditional electro-optic sampling technology based on polarization modulation, the electro-optic measuring device for the terahertz electromagnetic waves based on the Cerenkov radiation principle provided by the invention has the advantages that an optical system is greatly simplified, the technology is not limited by a crystal material, the electro-optic measuring device can be realized by acting with electro-optic crystals, the measuring bandwidth is large, the sensitivity is high, the signal to noise ratio is strong, and the electro-optic measuring device has a great reference value for researching the terahertz precise detection technology and application.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
FIG. 1 is a schematic diagram of the structure of a terahertz electromagnetic wave electro-optical measurement device in the invention;
FIG. 2 is a schematic diagram of a terahertz-light wave interaction structure in accordance with the present invention;
FIG. 3 is a schematic diagram of a silicon-based dielectric waveguide structure in accordance with the present invention;
FIG. 4 is a schematic diagram showing a cross-sectional structure of an optical waveguide on a thin film lithium niobate sheet according to the present invention;
FIG. 5 is a schematic diagram of the structure of the terahertz electromagnetic wave electro-optic sampling probe in the invention;
FIG. 6 is a schematic diagram of an optical waveguide structure on a thin film lithium niobate sheet according to the present invention;
FIG. 7 is a flow chart of a method for manufacturing the terahertz electromagnetic wave electro-optical measurement device in the invention;
FIG. 8 is a schematic diagram of a pulse terahertz signal measurement system based on heterodyne electro-optic sampling according to an embodiment of the present invention;
Fig. 9 is a schematic diagram of a pulse terahertz signal measurement system based on balanced heterodyne electro-optical sampling according to an embodiment of the present invention.
1. A support layer; 2. a lithium niobate planar layer; 3. a lithium niobate ridge waveguide layer; 4. a coupling tip; 5. a transmission section; 6. a positioning strip; 7. a locking block; 8. a switching tip; 9. a standard interface transition waveguide; 10. a through cavity; 11. a locking cavity; 12. a repetition frequency locked femtosecond laser; 13. a beam splitter; 14. a terahertz signal generator; 15. a standard interface transition waveguide; 16. an electro-optic sampling probe; 17. a photodetector; 18. a data acquisition and processing module; 19. an edge lens; 20. balancing the photodetector; 21. a reference clock; 100. a thin film lithium niobate substrate; 200. a dielectric rod waveguide; 300. the standard interface converts the waveguide.
Detailed Description
In order to more clearly illustrate the present invention, the present invention will be further described with reference to the following examples and FIGS. 1 to 9. Like parts in the drawings are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and that this invention is not limited to the details given herein.
As shown in fig. 1, the present invention discloses a terahertz electromagnetic wave electro-optical measurement device, comprising:
the standard interface conversion waveguide 300 is configured to receive the terahertz electromagnetic wave to be measured and feed the terahertz electromagnetic wave into the dielectric rod waveguide 200;
A dielectric rod waveguide 200 for transmitting the fed terahertz electromagnetic wave at a first angle onto the thin film lithium niobate substrate 100;
the thin film lithium niobate substrate 100 is used for outputting the laser pulse carrying the terahertz electromagnetic wave to the photoelectric detector after the incident sampling laser pulse interacts with the incident terahertz electromagnetic wave.
Specifically, terahertz electromagnetic waves are fed onto the dielectric rod waveguide 200 through the standard interface conversion waveguide 300 and are transmitted to the thin film lithium niobate substrate 100; the sampling laser pulse is efficiently incident to 100 optical waveguides on the thin film lithium niobate substrate through end surface coupling, interacts with terahertz electromagnetic waves incident at the Cerenkov angle, and outputs laser pulses carrying the terahertz electromagnetic waves to the photoelectric detector with low loss. As shown in fig. 2, a schematic of terahertz-light wave interactions.
In one specific embodiment, as shown in fig. 2, the dielectric rod waveguide 200 includes: a coupling tip 4, a transmission section 5, a positioning bar 6, a locking block 7 and a conversion tip 8,
A conversion tip 8 for receiving terahertz electromagnetic waves, transmitting to the transmission section 5;
a locking block 7 for fixing the standard interface conversion waveguide 300 to the conversion tip 8;
A positioning bar 6 for determining a fixed relative position between the dielectric rod waveguide 200 and the standard interface conversion waveguide 300;
a transmission section 5 for realizing the transformation of the terahertz electromagnetic wave transmission direction and transmitting the terahertz electromagnetic wave to a conversion tip 8;
A coupling tip 4 for coupling the received terahertz electromagnetic wave to be measured to the thin film lithium niobate substrate 100;
In a specific embodiment, the coupling tip 4 includes a first section and a second section, wherein a bottom surface of the first section is connected with the supporting layer 1, and the second section is connected with the transmission section 5, and an included angle between the first section and the second section is a complementary angle of the cerenkov angle. Wherein the coupling tip 4 comprises a first section parallel to the thin film lithium niobate substrate and a second section connected to the transmission section, so the cross section is an E-plane bending structure; the cross section of the transmission section 5 is of a rectangular structure, the cross section of the locking block 7 is of a T-shaped structure, and the cross section of the conversion tip 8, which is close to a standard interface conversion waveguide, is of a conical shape.
The thick end of one side of the conversion tip 8 is connected with the bottom end of the transmission section 5, and the surface of the connection part is covered with a positioning strip 6; the width of the thin end of one side of the conversion tip 8 is linearly gradually changed, and the lower side of the thin end is connected with the locking block; when the terahertz electromagnetic wave electro-optical measuring device works, the thin end of one side of the conversion tip 8 of the terahertz electromagnetic wave electro-optical measuring device is inserted into the through cavity 10 in the standard interface waveguide 300, and the locking cavity 11 of the standard interface waveguide 300 is matched and locked with the locking block 7.
Specifically, the terahertz electromagnetic wave electro-optical measurement device realizes positioning and locking through the positioning strip 6 and the locking block 7 on the dielectric rod waveguide 200 and the standard interface conversion waveguide 300, and specifically, the positioning strip 6 made of copper foil material is pressed and connected on the dielectric rod waveguide 200, and the standard interface waveguide card 300 is fixed with the dielectric rod waveguide on the positioning strip 6; the transmission of terahertz signals is achieved by inserting the conversion tip 8 into the through cavity 11; the locking block 7 is in a position of constant width in the thick end of the conversion tip 8.
In one embodiment, as shown in FIG. 3, the thin film lithium niobate substrate comprises
The support layer 1, the lithium niobate slab layer 2 and the lithium niobate ridge waveguide layer 3 are the same as the dielectric rod waveguide 200 in material, and the lithium niobate slab layer 2 and the lithium niobate ridge waveguide layer 3 jointly form a thin film lithium niobate on-chip optical waveguide structure; the cross section of the optical waveguide on the thin film lithium niobate sheet is of a ridge structure; the optical axis c axis of the lithium niobate crystal is along the long side direction of the laser incident end surface; as shown in fig. 3, the surface of the lithium niobate ridge waveguide layer 3 close to the lithium niobate slab layer 2 is the top surface of the lithium niobate ridge waveguide layer 3, the surface of the lithium niobate slab layer 2 far away from the lithium niobate ridge waveguide layer 3 is the bottom surface of the lithium niobate ridge waveguide layer 3, and the side surface of the lithium niobate ridge waveguide layer 3 is the surface facing inwards perpendicular to the paper surface; the laser incident end port surface is a side surface of the lithium niobate ridge waveguide layer 3, and is a rectangular cross section. The polarization direction of the sampling laser pulse forms an included angle of 45 degrees with the optical axis direction of the lithium niobate crystal, and the polarization direction of the terahertz electromagnetic wave is along the optical axis direction of the lithium niobate crystal.
In a specific embodiment, as shown in fig. 5, the invention further provides a terahertz electromagnetic wave electro-optical sampling probe, which comprises
A dielectric rod waveguide 200 for transmitting the fed terahertz electromagnetic wave at a first angle onto the thin film lithium niobate substrate 100;
the thin film lithium niobate substrate 100 is used for outputting the incident sampling laser pulse after interaction with the incident terahertz electromagnetic wave.
In a specific embodiment, the dielectric rod waveguide 200 and the supporting layer 1 on the thin film lithium niobate substrate 100 preferably have a material with a flat refractive index and low absorption in the terahertz frequency range, such as high-resistivity silicon or low-temperature semi-insulating GaAs; as shown in fig. 5, a schematic diagram of terahertz electromagnetic wave-optical wave interaction based on the cerenkov radiation principle is given when the material is a high-resistivity silicon substrate, it can be seen that when the terahertz wave is refracted at the Si-LN interface, its propagation angle θ LN in the LN layer is determined by fresnel law, which satisfies the following requirements:
sinθLN＝sinθSi·nSi/nLN
Where θ Si is the angle of incidence in silicon based, n Si and n LN are the terahertz refractive indices in silicon and lithium niobate materials, respectively.
As can be seen from fig. 2, the terahertz wave front is transmitted in the lithium niobate layer at the speed of c/n LN, the intersection point of the wave front and the optical axis is along the surface direction of the lithium niobate layer, and moves at the speed vp=c/(n LNsinθLN)＝c/(nSisinθSi) independent of the terahertz frequency, so that by selecting a suitable θ Si, that is, when the terahertz wave is incident at the cerenkov angle, the group velocity (c/n g) of the pulse light in the lithium niobate layer is equal, the speed matching of the terahertz wave and the optical wave is realized, c is the light speed, and n g is the group refractive index of the light.
By parsing the formula:
sinθSi＝ng/nSi
it is known that when θ Si ≡41°, the optical pulse is almost perfectly synchronized with the terahertz wave.
In addition, in the terahertz electromagnetic wave electro-optical measurement device disclosed by the invention, the detection bandwidth range is related to the width of the sampling pulse laser. Since the terahertz electromagnetic wave front is tilted with respect to the beam, different lateral portions of the optical pulse interact with different phases of the terahertz field, which will to some extent be less of a total electro-optic effect. Even a zero response condition may occur when opposite sides of the light pulse interact with terahertz wave fronts separated by one wavelength. Thus, in order to increase the electro-optic response effect as much as possible, a waveguide layout structure as shown in the top view of fig. 6 may be employed.
In addition, the terahertz electromagnetic wave electro-optical measurement device based on the Cerenkov radiation principle is limited by the high absorption characteristic of a lithium niobate material to terahertz waves, and the upper limit of the test bandwidth depends on the thickness d LN of the lithium niobate layer, so that the formula is satisfied:
fmax＝c/dLNnLN cosθLN
In a specific embodiment, as shown in fig. 7, the invention also discloses a preparation method of the terahertz electromagnetic wave electro-optical measurement device, which comprises the following steps:
Cutting a dielectric rod waveguide 200 containing a terahertz wave incident from a Cerenkov angle by a laser processing technology, and processing a lithium niobate layer of a thin film lithium niobate substrate 100 by a dry etching technology to obtain a thin film lithium niobate on-chip optical waveguide, in particular to a ridge waveguide single-mode optical waveguide; the coupling tip bottom surface 4 of the dielectric rod waveguide 200 is bonded to the surface of the support layer 1 of the thin film lithium niobate substrate 100 by a bonding process.
According to theoretical calculation and simulation design, a silicon-based dielectric rod waveguide structure meeting the Cerenkov angle is obtained, and the silicon-based dielectric rod waveguide structure is prepared through a laser processing technology; then combining the upper limit of the bandwidth of the test system, obtaining a broadband film lithium niobate on-chip optical waveguide structure through theoretical calculation and simulation, and sampling a dry etching semiconductor processing technology to obtain the broadband film lithium niobate on-chip optical waveguide structure; and finally, connecting the bottom surface of the coupling tip of the silicon-based dielectric rod waveguide with the thin film lithium niobate high-resistivity support silicon layer by adopting a bonding process.
In a specific embodiment, the terahertz electromagnetic wave electro-optical measurement device provided by the invention can be applied to measurement of terahertz electromagnetic wave waveform parameters, and the application implementation process is briefly described below:
As shown in fig. 8, a pulse terahertz signal measurement system based on heterodyne electro-optic sampling includes a femtosecond laser 12 with locked repetition frequency, a beam splitter 13, a terahertz signal generator 14, a terahertz electromagnetic wave electro-optic measurement device, a photoelectric detector 17, a data acquisition and processing module 18 and a reference clock 21; the terahertz electromagnetic wave electro-optical measurement device comprises a standard interface conversion waveguide 15 and an electro-optical sampling probe 16.
A reference clock 21 for providing a reference clock signal to the terahertz signal generator 14, the repetition frequency locked femtosecond laser 12, and the data acquisition and processing module 18.
In the terahertz wave link, a terahertz signal generator 14 for providing terahertz electromagnetic waves;
A standard interface conversion waveguide 15 for feeding terahertz electromagnetic waves into an electro-optical sampling probe 16, the electro-optical sampling probe 16 for inputting terahertz electromagnetic waves into a lithium niobate layer thereof at a cerenkov angle;
A sampling pulse laser link, a repetition frequency locked femtosecond laser 12, for dividing the laser beam into two parts, namely pump light and sampling light;
the pump light is used for exciting the terahertz signal generator 14 to generate terahertz electromagnetic waves to be detected,
The sampling light is efficiently incident into the optical waveguide structure on the thin film lithium niobate substrate sheet in a lens or optical fiber coupling mode, interacts with terahertz electromagnetic waves incident from the cerenkov angle in the lithium niobate layer, and is output to the photodetector 17,
The data acquisition and processing module 18 is used for acquiring the electric signals output by the detector 17 and analyzing and obtaining the information of the related terahertz electromagnetic waves to be detected.
As shown in fig. 9, a pulse terahertz signal measurement system based on balanced heterodyne electro-optic sampling includes a femtosecond laser 12 with locked repetition frequency, a beam splitter 13, a terahertz signal generator 14, a terahertz electromagnetic wave electro-optic measurement device, an edge lens 19, a balanced photoelectric detector 20, a data acquisition and processing module 18 and a reference clock 21; the terahertz electromagnetic wave electro-optical measurement device comprises a standard interface conversion waveguide 15 and an electro-optical sampling probe 16.
A reference clock 21 for providing a reference clock signal to the terahertz signal generator 14, the repetition frequency locked femtosecond laser 12, and the data acquisition and processing module 18.
In the terahertz wave link, a terahertz signal generator 14 for providing terahertz electromagnetic waves
A standard interface conversion waveguide 15 for feeding terahertz electromagnetic waves into an electro-optical sampling probe 16,
An electro-optic sampling probe 16 for impinging terahertz electromagnetic waves at a cerenkov angle to a lithium niobate layer thereof;
A sampling pulse laser link, a repetition frequency locked femtosecond laser 12, for dividing the laser beam into two parts, namely pump light and sampling light;
the pump light is used for exciting the terahertz signal generator 14 to generate terahertz electromagnetic waves to be detected,
The sampling light is efficiently incident into the optical waveguide structure on the thin film lithium niobate substrate sheet through a lens or optical fiber coupling mode, and after the interaction with terahertz electromagnetic waves incident from the Cerenkov angle in the lithium niobate layer, the coupling with low loss is connected into the edge lens 19,
An edge lens 19, configured to ionize the sampled light into two light beams of a sum frequency component and a difference frequency component, and make the two light beams incident on a balanced photodetector 20 after being ionized;
the data acquisition and processing module 18 is configured to acquire the electrical signal output by the balance detector 20, and analyze the electrical signal to obtain information about the terahertz electromagnetic wave to be detected.
In the description of the present invention, it should be noted that the azimuth or positional relationship indicated by the terms "upper", "lower", etc. are based on the azimuth or positional relationship shown in the drawings, and are merely for convenience of describing the present invention and simplifying the description, and are not indicative or implying that the apparatus or element in question must have a specific azimuth, be constructed and operated in a specific azimuth, and thus should not be construed as limiting the present invention. Unless specifically stated or limited otherwise, the terms "mounted," "connected," and "coupled" 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 communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
It is further noted that in the description of the present invention, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
It should be understood that the foregoing examples of the present invention are provided merely for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.
Claims (10)
1. A terahertz electromagnetic wave electro-optical measurement device, characterized by comprising:
A thin film lithium niobate substrate, a dielectric rod waveguide and a standard interface conversion waveguide,
The standard interface conversion waveguide is used for receiving terahertz electromagnetic waves to be detected and feeding the terahertz electromagnetic waves to the dielectric rod waveguide;
the dielectric rod waveguide is used for transmitting the fed terahertz electromagnetic waves to the thin film lithium niobate substrate at a preset first included angle;
the thin film lithium niobate substrate is used for outputting laser pulses carrying terahertz electromagnetic waves to the photoelectric detector after the incident sampling laser pulses interact with the incident terahertz electromagnetic waves.
2. The device of claim 1, wherein the first angle is a cerenkov angle.
3. The apparatus of claim 1, wherein the dielectric rod waveguide comprises a coupling tip, a transmission segment, and a transition tip connected in sequence;
the conversion tip is used for receiving the terahertz electromagnetic wave and transmitting the terahertz electromagnetic wave to the transmission section;
The transmission section is used for realizing the transformation of the transmission direction of the terahertz electromagnetic wave and transmitting the terahertz electromagnetic wave to the coupling tip;
and the coupling tip is used for coupling the received terahertz electromagnetic wave to be detected to the thin film lithium niobate substrate.
4. A device according to claim 3, wherein the dielectric rod waveguide comprises a silicon or GaAs semiconductor.
5. The apparatus of claim 1, wherein the thin film lithium niobate substrate comprises a support layer, a lithium niobate slab layer, and a lithium niobate ridge waveguide layer,
The optical axis direction of the lithium niobate crystal of the thin film lithium niobate substrate is the long side direction of the laser incident port surface; the material of the supporting layer is consistent with the material of the dielectric rod waveguide, and the lithium niobate slab layer and the lithium niobate ridge waveguide layer jointly form a thin film lithium niobate on-chip optical waveguide structure.
6. The device of claim 5, wherein the cross-section of the optical waveguide on the thin film lithium niobate sheet is a ridge structure.
7. The device of claim 3, wherein the coupling tip comprises a first section and a second section, wherein a bottom surface of the first section is connected to the support layer of the thin film lithium niobate substrate, the second section is connected to the transmission section, and an included angle between the first section and the second section is a complementary angle to the cerenkov angle.
8. A device according to claim 3, wherein the thick end of the conversion tip is connected with the bottom end of the transmission section, and the surface of the connection part is covered with a positioning strip; the width of the thin end of the conversion tip is linearly gradually changed; the thin end of the conversion tip is inserted into the through cavity in the standard interface waveguide, and the locking cavity of the standard interface waveguide is matched and locked with the locking block of the dielectric rod waveguide.
9. The apparatus of claim 8, wherein the apparatus is configured such that the polarization direction of the incident sampled light is at a predetermined first angle to the optical axis of the lithium niobate crystal of the thin film lithium niobate substrate, and the polarization direction of the incident terahertz wave is parallel to the optical axis of the lithium niobate crystal of the thin film lithium niobate substrate.
10. The electro-optical measurement method of the terahertz electromagnetic wave is characterized by comprising the following steps of:
The standard interface conversion waveguide receives terahertz electromagnetic waves to be detected and feeds the terahertz electromagnetic waves into the dielectric rod waveguide;
The dielectric rod waveguide transmits the fed terahertz electromagnetic wave to a thin film lithium niobate substrate at a preset first included angle;
The thin film lithium niobate substrate outputs laser pulses carrying terahertz electromagnetic waves to the photoelectric detector after the incident sampling laser pulses interact with the incident terahertz electromagnetic waves.
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