Terahertz generation and radiation device and terahertz phased array system based on double elliptical conical slot antenna

Abstract

The invention provides a terahertz generation and radiation device based on a double-ellipse conical groove antenna, which mainly comprises a terahertz generation part and a terahertz radiation part, and different device units in the terahertz generation part are used for generating terahertz based on two received light waves with different phase differences. Converting two beams of light waves with a specific phase difference into terahertz waves by using a light wave difference frequency effect, wherein the terahertz waves inherit the phase difference of the light waves; and the terahertz radiation part is used for radiating the terahertz waves to a free space so as to realize beam steering of the terahertz waves in a far field. Furthermore, the invention also discloses a terahertz phased array system. According to the invention, wide-angle and grating lobe-free scanning of terahertz wave beams can be realized, and a large-scale array can be realized.

Description

Technical Field

[0001] This invention relates to the field of terahertz phased arrays, and in particular to a terahertz generation and radiation device and a terahertz phased array system based on a double elliptical conical slot antenna. Background Technology

[0002] Terahertz (THz) waves typically refer to electromagnetic waves with frequencies between 0.1 and 10 THz. They possess advantages such as strong penetration, large bandwidth, narrow beamwidth, and low photon energy, demonstrating enormous application potential in fields such as non-destructive testing, high-resolution imaging, secure communication, and space exploration. However, compared to traditional microwave and millimeter-wave bands, the gain of a single antenna in the terahertz band is lower, and the transmission loss of terahertz waves in the atmosphere is more severe. This results in shorter operating ranges for terahertz wireless communication and radar detection systems, and makes it difficult to achieve functions such as rapid beam scanning and high-precision beam control.

[0003] Phased array devices can achieve functions such as directional beam radiation and rapid scanning by changing the phase of the electromagnetic waves emitted by each antenna element. They have advantages such as high gain, low sidelobes, and high spatial resolution. They are one of the key ways to break through the bottleneck of the operating range of terahertz systems and have become the core technology of next-generation terahertz radar, terahertz communication and imaging systems.

[0004] Terahertz phased arrays can be divided into two architectures: passive phased arrays and active phased arrays. Passive terahertz phased arrays distribute electromagnetic waves to amplitude- and phase-controllable radiating elements through passive networks or open-feed systems. They are typically implemented using materials such as liquid crystal materials, semiconductor materials, phase change materials, graphene, and microelectromechanical systems (MEMS). They offer high degrees of freedom and relatively low thermal management complexity, making large-scale arrays easily achievable. However, due to limitations in material properties or slow mechanical response, passive phased arrays have low modulation rates and low beam control efficiency. Active terahertz phased arrays are complex, integrated systems. Each antenna element is equipped with an active feed network (typically including amplifiers, phase shifters, frequency multipliers, etc.), which can independently generate, modulate, and receive terahertz waves. They are often implemented using semiconductor processes such as complementary metal-oxide-semiconductor (CMOS) and silicon germanium bicarbonate (BiCMOS). Compared to passive phased arrays, active phased arrays offer several advantages. First, their control devices are more efficient, but heat dissipation issues due to narrow antenna array spacing limit their large-scale deployment. Second, in the terahertz band, the parasitic capacitance of devices in the active feed network significantly affects phase-shifting accuracy, leading to increased sidelobes and pointing deviations after beamforming. Furthermore, research on terahertz active phased arrays is constrained by advancements in semiconductor technology.

[0005] Therefore, it is particularly important to study novel terahertz phased array technology that can easily realize large-scale arrays and also has a certain width of scanning angle. Summary of the Invention

[0006] To overcome the problem that existing terahertz phased arrays are difficult to implement on a large scale, this invention provides a terahertz generation and radiation device and a terahertz phased array system based on a double elliptical conical slot antenna.

[0007] The present invention achieves its objective through the following technical solution:

[0008] The first aspect of the present invention discloses a terahertz generating and radiating device based on a double elliptical conical slot antenna, which is equipped with a terahertz generating part and a terahertz radiating part. The terahertz generating unit is used to convert light waves into terahertz waves, and includes: The second-order nonlinear material waveguide layer has a continuous thin film and multiple equally spaced parallel ridge waveguides formed on the continuous thin film. Multiple electrode units are provided, each electrode unit comprising a metal electrode formed on a continuous thin film surface and symmetrically arranged on both sides of a ridge waveguide. The metal electrode consists of an electrode body and multiple T-shaped structures connected to the same side of the electrode body and arranged at equal intervals. The metal electrode is divided into an adjacent uniform electrode region and a gradient electrode region. In the uniform electrode region, the horizontal side lengths of the T-shaped structures are equal, while in the gradient electrode region, the horizontal side lengths of the T-shaped structures gradually increase from the uniform electrode region until the horizontal sides of adjacent T-shaped structures are connected. The terahertz radiating section is used to radiate the terahertz wave into free space, and includes: An antenna array has multiple antenna elements arranged at equal periods. Each antenna element includes an antenna radiating arm formed on a continuous thin film surface and symmetrically arranged on both sides of a ridge waveguide, and a double elliptical conical slot located between two antenna radiating arms. The inner and outer edges of the antenna radiating arms are both quarter-elliptical profiles. The width of the double elliptical conical slot gradually increases from the coupling end to the radiating end of the antenna radiating arm. The maximum aperture of the antenna element is not less than λ / 2, where λ is the wavelength of the terahertz wave. In the electrode unit, there is an inter-electrode physical gap G between adjacent metal electrodes; in the antenna unit, there is an antenna coupling end physical gap g between adjacent antenna radiating arms.

[0009] As an alternative, the terahertz radiating section further includes: a slot transition region having a connecting portion formed on a continuous thin film surface and symmetrically arranged on both sides of the ridge waveguide, and a slot line located between the two connecting portions; the two ends of the connecting portion are respectively connected to a metal electrode and an antenna radiating arm, and the shape of the slot line is defined by the inner edges of the two connecting portions.

[0010] As an alternative, the slot line is constructed as a tapered, gradually widening slot line; the width of the tapered, gradually widening slot line at one end of the metal electrode is equal to the size of the physical gap G between the electrodes, and the width at the other end is equal to the size of the physical gap g at the antenna coupling end, and its width gradually narrows or widens from the metal electrode to the antenna radiating arm. Further, the slot line is constructed to include a uniform slot line connected to the end of the tapered, gradually widening slot line away from the metal electrode; the width of the uniform slot line is equal to the size of the physical gap g at the antenna coupling end.

[0011] As an alternative, the slot line is constructed as a uniform slot line, the width of which is equal to the size of the physical gap G between the electrodes, and the physical gap g at the antenna coupling end is equal to the physical gap G between the electrodes.

[0012] As an alternative, the period d of the antenna array satisfies λ / 2 < d < λ, and the relationship between the antenna array spacing d and the terahertz beam steering angle θ satisfies .

[0013] As an alternative, in the antenna array, the physical gap D between adjacent antenna elements is 0, and the period d of the antenna array is equal to the maximum aperture of the antenna element.

[0014] As an alternative, the waveguide layer has an x-cut half-etched structure; the second-order nonlinear material is lithium niobate.

[0015] As an alternative, the metal electrode, antenna radiating arm, and connecting part are made of the same metal material, which can be any one of aluminum, copper, or gold.

[0016] The second aspect of this invention discloses a terahertz phased array system based on a double elliptical conical slot antenna, comprising an optical wave modulation unit and the terahertz generation and radiation device described in the first aspect of this invention; the optical wave modulation unit is configured with a power divider assembly and a phase shifter assembly; the power divider assembly has multiple cascaded one-to-two power dividers, and each one-to-two power divider is an on-chip power divider formed on a continuous thin film surface and based on the second-order nonlinear material; the phase shifter assembly has multiple phase shifters corresponding one-to-one with the ridge waveguide, and each phase shifter is an on-chip phase shifter formed on a continuous thin film surface and based on the second-order nonlinear material. The power divider assembly is used to divide the received near-infrared laser signal into multiple optical wave signals with the same amplitude and initial phase; each phase shifter in the phase shifter assembly is used to independently phase-modulate one of the received multiple optical wave signals.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Unlike traditional active CMOS arrays which are limited by power density and heat management and have difficulty expanding the number of channels, this invention is based on a photonic integration platform of second-order nonlinear materials such as lithium niobate. Through on-chip integration, optical waveguides, metal electrodes, antenna arrays, power dividers and phase shifters are integrated onto a continuous thin film of second-order nonlinear material to obtain a multifunctional terahertz chip that generates, radiates and directs terahertz beams. It is no longer limited by semiconductor processes, and the power consumption and heat dissipation problems are relatively controllable, making it easier to realize large-scale arrays.

[0018] (2) The antenna element in this invention adopts a double elliptical conical slot antenna, which has a simple structure, is easy to design and manufacture, and has the advantages of miniaturization and high integration. For example, the preferred antenna element size at a frequency of 360 GHz is only 1500 μm × 511.5 μm × 500 nm. Furthermore, the double elliptical conical slot antenna designed in this invention provides a smoother and more optimized impedance transformation path compared to the traditional linear or exponential gradient curve. By changing the elliptical shape of the outer edge of the antenna, the antenna impedance and radiation performance can be adjusted to achieve dynamic tuning of the antenna performance at different frequencies.

[0019] (3) By selecting appropriate antenna array spacing and physical gaps between adjacent antenna elements, this invention can effectively suppress the generation of grating lobes during beam scanning of a terahertz phased array system, ensuring that only a single main lobe exists in the far-field pattern, achieving wide-angle grating-lobe-free scanning, and solving the problems of signal spatial aliasing and interference enhancement. For example, the terahertz phased array system provided by this invention can achieve ±39° narrow beam, grating-lobe-free terahertz beam scanning at a frequency of 360 GHz. Furthermore, due to this wide-angle scanning capability, it has potential application value in fields such as terahertz radar and airborne communication.

[0020] (4) The present invention utilizes the electro-optic effect of lithium niobate material to achieve high-precision phase shifting, accurately control the phase difference of terahertz waves generated between adjacent channels, and realize the precise turning and scanning of terahertz beams; in addition, lithium niobate material also has a sub-picosecond electro-optic response speed, and its excellent electro-optic properties enable the on-chip phase shifter to exhibit extremely fast phase modulation speed, realizing fast and sensitive turning of terahertz beams. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the terahertz generation and radiation device in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a single device unit in an embodiment of the present invention; Figure 3 This is a schematic diagram of the terahertz generator in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a single double-elliptical conical slot antenna element in an embodiment of the present invention; Figure 5 This is a schematic diagram of the terahertz generation and radiation system of the present invention; Figure 6 The polar coordinate far-field radiation diagram of a terahertz phased array with a frequency of 360 GHz, an antenna array spacing of 511.5 μm, and a phase shift of 0. Figure 7 The polar coordinate far-field radiation diagram of a terahertz phased array with a frequency of 360 GHz, an antenna array spacing of 511.5 μm, and a phase shift of 139° is shown.

[0022] Explanation of reference numerals in the attached figures: 100. Power divider; 200. Phase shifter; 300, silicon dioxide substrate; 400. Lithium niobate waveguide layer; 410. Lithium niobate thin film; 420. Lithium niobate ridge waveguide; 500, Electrode unit; 501, Uniform electrode region; 502, Gradient electrode region; 510, Metal electrode; 511, Electrode body; 512, T-shaped structure; 5121, Horizontal side; 5122, Vertical side; 600, Antenna element; 610, Antenna radiating arm; 611, Antenna coupling end; 612, Antenna radiating end; 613, Inner edge of antenna; 614, Outer edge of antenna; 620, Double elliptical conical slot; 700, Slot transition area; 710, Antenna connection part; 720, Slot; 721, Tapered gradient slot; 722, Uniform slot. Detailed Implementation

[0023] This invention improves upon the principle of slot line scaling in traditional Vivaldi antennas by designing the slot lines between the antenna radiating arms as a double-elliptical gradient, thus achieving effective terahertz radiation. Furthermore, by combining a power divider and a phase shifter, the phase difference between adjacent channel terahertz waves is altered, enabling beam steering of the terahertz waves in the far field. Moreover, this invention can also combine the antenna array with an on-chip terahertz source on lithium niobate, realizing a terahertz phased array on a thin-film lithium niobate sheet.

[0024] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, the x-direction refers to the transverse direction, the y-direction to the longitudinal direction, and the z-direction to the film thickness direction. Terms indicating orientation or positional relationships, such as "upper," "lower," "inner," "outer," "front," and "rear," are based on the orientation or positional relationships shown in the accompanying drawings and are used solely for the convenience of describing the invention and for simplification. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, terms such as "first" and "second" are used to distinguish similar objects and are not necessarily used to describe a specific order or relative importance. In addition, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, but rather to include other units not explicitly listed or inherent to these products or devices.

[0026] This invention provides a terahertz generation and radiation device based on a double elliptical conical slot antenna (hereinafter referred to as "terahertz generation and radiation device"), which mainly consists of a terahertz generation section and a terahertz radiation section. In the terahertz generation section, different device units, based on two received light waves with different phase differences, utilize the light wave difference frequency effect to convert the two light waves with a specific phase difference into terahertz waves, and the terahertz waves inherit the phase difference of the light waves; the terahertz radiation section is used to radiate the terahertz waves into free space to achieve beam steering of the terahertz waves in the far field. The generation of terahertz waves using the light wave difference frequency effect can be understood as the phenomenon that two light waves with similar frequencies and a frequency difference within the terahertz range generate terahertz waves in an optical waveguide through a difference frequency process.

[0027] Combination Figures 1 to 4 As shown, the terahertz generating section mainly includes a silicon dioxide substrate 300, a lithium niobate waveguide layer 400 formed on the surface of the silicon dioxide substrate 300, and a plurality of electrode units 500 arranged on the surface of the lithium niobate waveguide layer 400.

[0028] The lithium niobate waveguide layer 400 serves as the site for generating terahertz waves using the difference-frequency effect of optical waves. Specifically, it includes a lithium niobate thin film 410 formed on the surface of a silicon dioxide substrate 300, and multiple lithium niobate ridges arranged in parallel on the film surface. It can be understood that the lithium niobate thin film 410 is a continuous thin film structure, and the lithium niobate ridges and the underlying lithium niobate thin film together constitute the lithium niobate ridge waveguide 420. In addition to silicon dioxide, the substrate can also be made of insulating materials such as quartz or silicon. These materials generally have low refractive index, low loss, high thermal stability, and lattice matching with the lithium niobate thin film to achieve effective confinement of the optical waveguide mode and high-quality on-chip integration.

[0029] The lithium niobate waveguide layer 400 can be designed with an x-cut half-etched structure. A ridge structure for optical wave transmission can be constructed based on the lithium niobate thin film through micro-nano processing (such as photolithography or etching) to form the lithium niobate ridge waveguide 420.

[0030] The thickness of lithium niobate thin films (410) is typically 200–400 nm, while the thickness of lithium niobate ridge waveguides (420), including the thickness of the lithium niobate thin film, is typically 400–800 nm. The specific thicknesses are determined comprehensively based on requirements such as optical wavelength, single-mode conditions, nonlinear coefficient optimization, and process feasibility. The width of lithium niobate ridge waveguides (420), designed for single-mode transmission, is typically 0.5–2 μm. The waveguide length can be designed to balance the generation efficiency of terahertz waves with the propagation losses of both optical and terahertz waves, and is typically 1–10 mm.

[0031] It is worth noting that in the terahertz generation section, the optical mode (i.e., the light field energy) is efficiently confined within the lithium niobate ridge waveguide 420 and propagates forward. Therefore, the key structure in the lithium niobate waveguide layer 400 that plays a guiding role is mainly the lithium niobate ridge waveguide 420 (referred to as "waveguide").

[0032] The placement of the lithium niobate thin film 410 is primarily based on a comprehensive consideration of factors such as optical field confinement, loss control, process tolerance, and on-chip integration. The use of a semi-etched ridge structure, retaining the bottom film (250 nm), maintains the vertical overlap between the optical mode field and the highly nonlinear region of lithium niobate, avoiding increased losses in the fully etched strip waveguide due to near-field leakage from the substrate. Simultaneously, the ridge structure provides lateral confinement to enhance power density, and the etching depth of the semi-etched layer (250 nm) is significantly lower than that of the fully etched layer (500 nm), significantly reducing the aspect ratio requirements, sidewall roughness, and lattice damage, thereby improving phase matching consistency and device yield.

[0033] It should also be noted that, besides lithium niobate, common second-order nonlinear materials such as gallium phosphide (GaP), gallium arsenide (GaAs), zinc telluride (ZnTe), gallium selenide (GaSe), and zinc germanium phosphide (ZGP) also exhibit significant second-order nonlinear optical effects and unique dispersion characteristics, and can all be used to generate terahertz waves based on the difference-frequency effect of optical waves. However, compared to the aforementioned materials, lithium niobate simultaneously possesses a large second-order nonlinear coefficient, low optical loss, and a relatively high optical damage threshold. Furthermore, the excellent electro-optic effect and fast response time of lithium niobate are also beneficial for phase modulation of optical waves, making lithium niobate the preferred material in this scheme. However, this invention does not limit the use of other second-order nonlinear materials to fabricate waveguide structures.

[0034] On the surface of the lithium niobate thin film 410, a metal electrode 510 is symmetrically disposed on both sides of each lithium niobate ridge waveguide 420, forming an electrode unit 500. These metal electrodes 510 disposed on both sides of the lithium niobate ridge waveguide 420 can be used to confine the terahertz field and guide the terahertz wave to propagate along the lithium niobate ridge waveguide 420, thus forming an effective working region for realizing optical-terahertz energy conversion together with the lithium niobate ridge waveguide 420.

[0035] Understandably, for difference frequency generation, the phase matching condition requires the phase mismatch Δk to satisfy the following condition: Δk=n1ω1 / c-n2ω2 / cn T ω T / c=0(1) In the formula, n1 represents the effective refractive index of the input high-frequency light wave, ω1 represents the angular frequency of the input high-frequency light wave; n2 represents the effective refractive index of the input low-frequency light wave, and ω2 represents the angular frequency of the input low-frequency light wave; n T ω represents the effective refractive index of the generated terahertz wave. T ω represents the angular frequency of the generated terahertz wave; c represents the speed of light in a vacuum.

[0036] Energy conservation in nonlinear processes also requires the angular frequency to satisfy the following condition: ω1-ω2-ω T =0 (2).

[0037] Since the frequencies of the two input light waves are similar, the phase matching approximation condition for the difference frequency effect can be obtained by combining formulas (1) and (2) as follows: n g,opt =n eff,TH (3), In the formula, n g,opt n represents the group refractive index of light waves in the preset near-infrared band. eff,THz This represents the effective refractive index of the generated terahertz waves.

[0038] It should be noted that both the input high-frequency and low-frequency light waves are near-infrared light waves within a preset wavelength band (such as a typical 1550±25nm), and the group refractive index of the light waves in this preset near-infrared wavelength band is the same. Therefore, the two light waves ω required for the difference frequency... 1, ω2 is also within this band, and the two have the same refractive index of light groups.

[0039] In this embodiment of the invention, the metal electrode 510 can be specifically designed as including an electrode body 511 and a plurality of T-shaped structures 512 arranged at equal intervals on the same side of the electrode body 511. The horizontal side 5121 of the T-shaped structure 512 is parallel to the electrode body 511, and the vertical side 5122 is perpendicularly connected to the electrode body 511. The spacing (i.e., the period) between adjacent T-shaped structures 512 is the distance between the center points of two adjacent T-shaped structures 512, and the center point of the T-shaped structure 512 is the intersection of the central axis of the horizontal side 5121 and the central axis of the vertical side 5122 of the T-shaped structure 512. The height of the metal electrode 510 (the dimensional parameter along the thickness direction of the lithium niobate waveguide layer 400) can be selected in the range of 100~500nm, determined by factors such as phase matching requirements, skin depth, and ohmic loss.

[0040] Understandably, in this invention, the lithium niobate ridge waveguides 420 are arranged periodically along the x-direction to form a waveguide array on the surface of the lithium niobate thin film 410. The period of the T-shaped structure 512 in the metal electrode 510 refers to the period in the y-direction. The electrode body 511 and multiple periodically arranged T-shaped structures 512 constitute the metal electrode 510 on one side of the waveguide.

[0041] In electrode unit 500, the transverse physical gap G between two metal electrodes 510 (hereinafter referred to as "inter-electrode physical gap G") specifically refers to the distance between the edges of the transverse sides 5121 of adjacent metal electrodes 510. Its selectable range is 3-6 μm, and it is usually determined by factors such as phase matching requirements, terahertz generation efficiency, and ohmic loss.

[0042] In the terahertz generation section, the terahertz energy field is confined between adjacent metal electrodes 510, specifically within the region corresponding to the lateral physical gap between the electrodes 510. The terahertz mode is determined by the T-shaped structure 512. At the coupling end of the antenna element 600, the terahertz field is confined within the slot line 720, and the terahertz mode is determined by the slot line structure.

[0043] Because the structural parameters of the metal electrode 510 and the slot line 720 are different, the terahertz modes also differ, and these different modes affect the propagation effect. Therefore, in order to reduce energy loss caused by mode mismatch, this invention considers designing a transition region to allow the terahertz mode to smoothly transition from the electrode mode to the slot line mode. Based on the difference in the structural shape of the metal electrode 510 and the antenna radiating arm 610, a T-shaped structure 512 with unequal side lengths p is introduced as a transition structure, that is, a gradient electrode region 502 is set in the metal electrode 510. By gradually increasing the side length p to be equal to the period of the T-shaped structure (for example, by using a linear increase), the T-shaped structure can smoothly transition to the slot line structure.

[0044] Based on the above considerations, and in combination Figure 2 and Figure 3 As shown in this embodiment of the invention, the metal electrode 510 includes a uniform electrode region 501 and a gradient electrode region 502. T-shaped structures 512 in both regions are distributed at equal periods, with the main difference being the length of the transverse side of the T-shaped structures 512. Specifically, the uniform electrode region 501 contains M1 T-shaped structures 512, all with equal transverse side length p (p0). The gradient electrode region 502 contains M2 T-shaped structures 512, each with a different transverse side length p, which gradually increases (e.g., linearly) from the uniform electrode region 501 towards the antenna array until adjacent T-shaped structures 512 are laterally connected. The number of T-shaped structures M2 in the gradient electrode region is generally a single digit, while the number of T-shaped structures M1 in the uniform electrode region is determined by M2 and the total length of the metal electrode 510.

[0045] For example, in a specific application case, M1 is 10 and M2 is 5. The gradient electrode region 502 is arranged on the side of the uniform electrode region 501 near the antenna array. The lateral lengths of the five T-shaped structures 512 in the gradient electrode region 502 are p1 to p5, respectively. The lateral length increases linearly until the duty cycle of p4 and p5 reaches 1 in one cycle. At this time, the lateral sides of the adjacent T-shaped structures 512 are connected, and the electrode unit 500 naturally transitions to the slot line transition region 700.

[0046] The initial width of the slot line in the transition region 700 is the physical gap G between electrodes. The formula for calculating the duty cycle is as follows: Duty cycle = (4), In the formula, p is the length of the transverse side of the metal electrode T-structure 512 within one cycle. One electrode cycle.

[0047] This invention designs the structural parameters of the lithium niobate ridge waveguide 420 and the metal electrode 510, including adjusting the width and thickness of the lithium niobate ridge waveguide 420, as well as the width H of the transverse side of the T-shaped structure 512 in the metal electrode 510 and the physical gap G between the electrodes. This allows the effective refractive index of the terahertz wave to be equal to the group refractive index of the light wave at the desired frequency, thereby achieving phase matching between the light wave and the terahertz wave and ensuring the generation efficiency of the terahertz wave.

[0048] Terahertz radiators typically refer to antenna arrays. In this embodiment of the invention, the antenna array includes multiple double-elliptical conical slot antenna elements 600 (hereinafter referred to as "antenna elements 600") and a slot line transition region 700 located at the coupling end of the antenna elements 600, with each antenna element 600 arranged at equal lateral intervals. Figure 1As shown, there is usually a certain lateral physical gap (referred to as "inter-antenna element physical gap D") between adjacent antenna elements 600, specifically the distance between the edges of adjacent antenna elements 600. The period d of the antenna array is defined as the physical distance between the center points of two adjacent antenna elements, and is therefore also called "antenna array spacing d".

[0049] like Figure 1 As shown, the terahertz generating and radiating device as a whole consists of multiple periodically arranged device units. Each device unit includes a lithium niobate ridge waveguide 420, an electrode unit 500 used in conjunction with it (mainly including a pair of metal electrodes 510 located on both sides of the lithium niobate ridge waveguide 420), a double elliptical conical slot antenna unit 600 used in conjunction with it, and a slot line transition region 700 connecting the electrode unit 500 and the antenna unit 600. The multiple device units are arranged in parallel with equal periods in the x-direction, and each device unit is an independent functional unit that radiates terahertz waves with a specific frequency.

[0050] like Figure 2 As shown, each antenna element 600 consists of two antenna radiating arms 610 and a double elliptical conical slot 620 between the two antenna radiating arms 610. One end of the antenna radiating arm 610 is the antenna coupling end 611, and the other end is the antenna radiating end 612. The antenna radiating arm 610 mainly serves to define the boundary of the double elliptical conical slot and constrain the propagation direction of the terahertz beam. Its key design is to make the width of the double elliptical conical slot 620 gradually increase along the light propagation direction (y direction).

[0051] The two antenna radiating arms 610 are also symmetrically arranged about the lithium niobate ridge waveguide 420 and are connected to the metal electrode 510 in the terahertz generator through the connecting part 710, so that the electromagnetic field energy of the terahertz generator can be smoothly coupled into the double elliptical conical slot 620.

[0052] In this embodiment of the invention, the groove transition region 700 includes two connecting portions 710 symmetrically arranged on both sides of the lithium niobate ridge waveguide 420 and a groove line 720 between the two connecting portions 710. It can be understood that the connecting portion 710 is a metal block whose two ends are respectively connected to the metal electrode 510 and the metal antenna, and the groove line 720 specifically refers to the region between adjacent metal blocks, the shape of which is defined by the inner edges of two adjacent metal blocks.

[0053] like Figure 3As shown, the slot line 720 includes a tapered, gradually widening slot line 721. The length (y-direction) of the tapered, gradually widening slot line 721 is lw, and its width (x-direction) gradually narrows or widens from the electrode to the antenna direction. Specifically, one end of the connecting portion 710 is connected to the metal electrode 510, and the other end is connected to the antenna radiating arm 610. The width of the tapered, gradually widening slot line 721 is the distance between the two connecting portions 710. Correspondingly, the width of the tapered, gradually widening slot line 721 narrows or widens from G to g in the direction from the metal electrode 510 to the antenna radiating arm 610, where g is the lateral physical gap between adjacent antenna radiating arms 610 at the antenna coupling end 611 (referred to as "antenna coupling end physical gap g").

[0054] Furthermore, to smooth the impedance transition, reduce reflection loss, and improve coupling efficiency, the slot line 720 also includes a uniform slot line 722. The uniform slot line 722 is located at the end of the tapered slot line 721 away from the metal electrode 510, and its length (y direction) is la, and its width (x direction) is the physical gap g at the antenna coupling end.

[0055] Understandably, when the physical gap g at the antenna coupling end is equal to the physical gap G between the electrodes, the electromagnetic field energy in the terahertz generating section can be directly coupled into the antenna element. In this case, only the uniform slot line region 722 can be set, or even the slot line transition region 700 can be omitted, and the metal electrode 510 is directly connected to the antenna element 600.

[0056] Understandably, slot antennas are an increasingly widely used type of ultra-wideband antenna, radiating in the end-fire direction. They possess advantages such as wide bandwidth, high gain, low manufacturing cost, and ease of integration, making them promising for applications in ultra-wideband radar and communications. Single-polarized and dual-polarized arrays composed of slot antennas can be used in broadband antenna arrays or phased arrays with wideband scanning angles.

[0057] The traditional Vivaldi antenna is a slotted wire antenna with radiating arms that gradually change according to an exponential law. This invention improves upon it by replacing the traditional Vivaldi antenna with a double-elliptical conical slot antenna. The inner and outer edges of the radiating arms of the double-elliptical conical slot antenna are quarter-elliptical profiles. For example... Figure 4 As shown in the embodiment of the invention, the minor axis and major axis of the ellipse corresponding to the inner edge 613 of the antenna radiating arm 610 are Rx2 and Ry2, respectively, and the minor axis and major axis of the ellipse corresponding to the outer edge 614 of the antenna are Rx1 and Ry1, respectively. By adjusting these four parameters Rx1, Ry1, Rx2, and Ry2, the radiation performance of the antenna element, such as impedance, gain, and far-field pattern, can be adjusted, providing more freedom for antenna design.

[0058] In addition, it should be noted that, besides the design freedom, the double elliptical conical slot antenna designed in this invention still possesses the broadband characteristics of traditional conical slot antennas, meeting the requirement of frequency tunability. Furthermore, the double elliptical conical slot antenna is also easily connected to the metal electrode 510 in the terahertz generation section, meeting the requirements of on-chip integration.

[0059] Continue to refer to Figure 3 As shown, the dimensions of an antenna element can be simply represented by the following structural parameters: the length (y-direction) of the antenna element is py = Ry1, and the width (x-direction) is px = g + Rx1. 2. The height (z direction) is 500nm.

[0060] When a terahertz wave, acting as an electromagnetic energy carrier, couples into antenna element 600 through the slot transition region 700, the energy cannot radiate into free space due to the small physical gap g at the antenna coupling end. Instead, it propagates as a guided electromagnetic wave along the double elliptical conical slot 620 between the two antenna radiating arms 610. The initial width of the double elliptical conical slot 620 is the physical gap g at the antenna coupling end. With a small initial width, the electric field is constrained by the antenna radiating arms 610, which are made of metal, limiting the radiation capability. As the width of the double elliptical conical slot 620 increases, the constraint of the antenna radiating arms 610 on the electric field weakens. When the width of the double elliptical conical slot 620 reaches half the wavelength of the electromagnetic wave, the electromagnetic wave will radiate into free space. The distance between adjacent antenna radiating arms 610 at the antenna radiating end 612 is also the width of the radiating end slot, which simultaneously represents the width px of the antenna element, i.e., the maximum aperture of the antenna, px = g + Rx1. 2.

[0061] The initial width of the double elliptical conical slot 620 at the antenna coupling end 611 (i.e., the physical gap g at the antenna coupling end) is typically determined by the frequency of the terahertz wave. Considering the radiation effect, different initial widths may be selected for different terahertz wave frequencies. At the antenna radiating end 612, to effectively radiate the terahertz wave, the maximum aperture of the antenna element 600 should be greater than or equal to half the wavelength of the terahertz wave. The length py of the antenna element 600 should generally be greater than or equal to a wavelength corresponding to its operating frequency.

[0062] According to the phased array principle, the terahertz waves radiated by different antenna elements 600 coherently superimpose in the far field, and the final radiation direction of the terahertz beam is determined by the phase difference Φ between adjacent antenna elements 600. The relationship between the phase difference Φ between adjacent antenna elements 600 and the terahertz beam steering angle θ satisfies the following equation: (5), in, d is the terahertz beam steering angle, defined as the deflection angle of the antenna main lobe radiation direction relative to the antenna array normal direction (0°); d is the antenna array spacing; λ is the wavelength of the terahertz wave converted by the terahertz generator, abbreviated as "terahertz wave wavelength".

[0063] Understandably, the beam scanning range of terahertz phased arrays has always been one of the important indicators for evaluating phased array performance. According to the principle of phased arrays, the beam steering angle is related to the antenna array spacing and the wavelength of the electromagnetic wave, and the maximum beam steering angle determines the beam scanning range. However, for terahertz signals of a specific wavelength, if the antenna array spacing d is not properly selected, grating lobes may appear in the radiation pattern of the phased array, leading to spatial aliasing of the signal, interfering with the transmission of the main signal, and affecting the directivity and gain of the antenna.

[0064] The phase difference Φ ranges from -180° to +180°. Since Φ has a periodicity of 2π, the solution for the turning angle θ may not be unique, meaning that grating lobes may appear in the far-field radiation pattern of the phased array. The scanning angle and grating lobe position of a terahertz phased array are both related to the array spacing d and the terahertz wave wavelength λ. When d > λ, grating lobes are unavoidable; when d < λ / 2, changing the phase difference Φ across the entire range can achieve a ±90° grating-lobe-free beam scanning angle, but to effectively radiate terahertz waves, the maximum aperture of the antenna element 600 needs to be greater than or equal to λ / 2; when λ / 2 < d < λ, the grating-lobe-free beam scanning angle is limited by the value of d / λ, and when the phase difference reaches... The corresponding beam steering angle reaches At this point, grating lobes begin to appear. Therefore, by adjusting the antenna array spacing d, it can be made to satisfy λ / 2 < d < λ. At that time, it can ensure that no grating lobes are generated in the terahertz phased array within the beam scanning range.

[0065] Furthermore, to ensure effective suppression of grating lobes while achieving wide-angle beam scanning, the antenna array spacing d should be as small as possible. By definition, d = D + px, as... Figure 5 As shown, both D and px should be as small as possible. The minimum physical gap D between antenna elements can be 0, meaning adjacent antenna elements are arranged closely without any gap. In this case, the antenna array spacing d is equal to the width px of the antenna element, i.e.: d = px = g + Rx1 2. Therefore, by adjusting the short axis Rx1 of the outer edge 614 of the antenna, the antenna can maintain high gain while increasing the scanning range.

[0066] Regarding material selection, the metal electrode 510, antenna radiating arm 610, and connecting part 710 can be made of the same metal material, such as aluminum, copper, or gold. Of course, different materials can also be used, and this invention does not impose any limitations on this. It is understandable that using the same metal material is more convenient in terms of process implementation, and the process conditions and processing precision are also the same. Furthermore, the same material has the same resistivity, ohmic loss, and other properties, which also facilitates device characterization.

[0067] like Figure 5 As shown, another embodiment of the present invention provides a terahertz phased array system based on a double elliptical conical slot antenna. This system includes an on-chip integrated optical wave modulation unit, a terahertz generation unit, and a terahertz radiation unit. The structural design of the terahertz generation unit and the terahertz radiation unit can adopt the structural design of the terahertz generation and radiation device based on a double elliptical conical slot antenna in the above embodiments of the present invention, and will not be elaborated further.

[0068] The optical wave modulation unit is located before the terahertz generation unit. It is used to divide the received original optical signal into multiple optical waves with the same initial phase, and to perform phase modulation on the multiple optical waves with the same initial phase, thereby controlling the phase of the terahertz wave emitted by each antenna element, so as to finally achieve scanning of the terahertz beam direction.

[0069] Specifically, the optical wave control unit mainly consists of a power divider assembly and a phase shifter assembly. The power divider assembly is composed of multiple cascaded 1-to-2 power dividers 100, used to split the received near-infrared laser signal into multiple optical wave signals with the same amplitude and initial phase. The power divider 100 can be an on-chip power divider based on lithium niobate material; for example, a multimode interference (MMI) coupler can be selected, which mainly consists of an input waveguide, an output waveguide, and a multimode interference region located between them.

[0070] After the optical field is injected into the multimode interference region through the input waveguide, the constructive interference between multiple modes produces a self-mirror effect, periodically generating one or more images of the input optical field along the direction of light propagation. Based on this principle, the MMI coupler, as an optical power divider, can uniformly distribute the input optical power to multiple output waveguides and ensure that each output light wave has the same initial phase and amplitude, thereby achieving highly consistent optical power distribution.

[0071] The phase shifter assembly is responsible for independently controlling the phase of the multiple optical signals output by the power divider assembly. It includes multiple phase shifters 200, each corresponding to one optical signal. Specifically, the phase shifter 200 can be an on-chip phase shifter based on lithium niobate material.

[0072] Each phase shifter 200 utilizes the electro-optic effect of lithium niobate material. By applying a voltage to the electrodes on both sides of its internally integrated waveguide, it causes a change in the refractive index of the waveguide, thereby generating an additional phase change in the transmitted light within the waveguide, i.e., achieving additional phase modulation. By precisely adjusting the magnitude of the applied voltage for each path, the phase change amplitude of each light wave can be independently controlled, thus indirectly regulating the phase of the terahertz waves generated by the conversion of each light wave, ultimately ensuring that the phase difference of the terahertz waves radiated between adjacent antenna elements in the double elliptical conical slot antenna array is equal. Optionally, other functional materials with electro-optic effects can also be used for the phase shifter 200.

[0073] It is important to note that because on-chip phase shifters utilize the electro-optic properties of the material itself to achieve phase modulation, and its physical process is based on dielectric polarization rather than charge transport, it does not suffer from the inherent parasitic capacitance problem caused by CMOS transistors. Furthermore, the extremely fast electro-optic effect speed of lithium niobate material provides higher phase shift accuracy than CMOS transistors.

[0074] Specifically, the phase shifter 200 can be a Mach-Zehnder interferometer (MZI) phase shifter, whose core structure consists of two 3dB couplers and two optical waveguide arms (referred to as "optical arms"). The two optical arms are arranged in parallel between the two couplers arranged sequentially along the optical path. By applying different modulation voltages to the two optical arms, a controllable phase difference is generated between the two optical arms. After the two light waves interfere through the second 3dB coupler, a continuously adjustable synthesized phase can be achieved at the output end, thereby realizing the phase shifting function.

[0075] The working principle of the terahertz phased array system described in this embodiment of the invention is as follows: Taking near-infrared continuous lasers with a frequency difference of terahertz around 1550nm as an example, two near-infrared continuous lasers are coupled to the system with TE polarization.

[0076] First, in the optical wave control unit, the two beams are split into multiple paths (e.g., 16 paths) by cascaded power dividers 100. Each optical wave is phase-controlled by an independent phase shifter 200 and then coupled into the terahertz generation unit.

[0077] In each device unit of the terahertz generation section, for each lithium niobate ridge waveguide 420, since the frequency interval between the two input light waves is the terahertz frequency, a terahertz wave corresponding to the frequency interval can be effectively generated in the lithium niobate ridge waveguide 420 through the optical difference frequency effect. The generated terahertz wave is guided to propagate forward along the path defined between adjacent metal electrodes 510 in the electrode unit and reaches the slot line transition region 700. In this region, the terahertz wave is confined within the slot line 720 and continues to propagate forward, subsequently entering the terahertz radiation section.

[0078] In the terahertz radiating section, the terahertz wave continues to propagate forward within the double elliptical conical slot 620 defined by the antenna radiating arm 610. Initially, due to the small width of the double elliptical conical slot 620, the terahertz wave is tightly confined by the antenna. As the width of the double elliptical conical slot 620 increases to approximately half the terahertz wavelength, the confinement is released, and the terahertz wave radiates into free space.

[0079] In free space, the terahertz waves radiated by all antenna elements 600 in the system coherently superimpose in the far field. By precisely controlling the phase of each optical wave through the phase shifter 200, the phase difference of the radiated wavefronts of adjacent antenna elements 600 can be flexibly set, thereby achieving electronic scanning of the radiation direction of the synthesized terahertz beam.

[0080] As can be seen from this process, this invention innovatively integrates a thin-film lithium niobate-based photogenerated terahertz source and a terahertz phased array antenna on a single chip. This architecture fully realizes the generation, transmission, radiation, and beam steering of terahertz waves on a single multifunctional integrated terahertz chip, providing a novel technical path for constructing a compact, efficient, and multifunctional active terahertz phased array system.

[0081] The on-chip integrated terahertz phased array system described in this invention embodiment can be fabricated using x-cut commercial thin-film lithium niobate wafers. The main fabrication process is as follows: First, photoresist is spin-coated onto a thin-film lithium niobate wafer sample, and then exposed using electron beam lithography (EBL) to define the power divider, phase shifter, and ridge waveguide patterns.

[0082] The exposed sample is then developed. During development, the photoresist in the exposed areas is selectively dissolved, while the unexposed areas are retained, forming a mask pattern complementary to the waveguide structure.

[0083] Next, the lithium niobate thin film is dry-etched at 250 nm using inductively coupled plasma (ICP) etching or reactive ion etching (RIE) processes based on argon plasma (Ar+), transferring the pattern to the lithium niobate thin film and completing the fabrication of the power divider, phase shifter and lithium niobate optical waveguide.

[0084] Finally, the metal electrode 510 and the antenna were fabricated using an electron beam lift-off process, and the desired terahertz phased array system was obtained.

[0085] In a specific application case, taking a terahertz wave with a generation and radiation frequency of 360 GHz and a corresponding wavelength of λ = 833 μm as an example, the relevant structural parameters of the terahertz phased array system are selected as follows based on the requirements for efficient terahertz generation and radiation: The lithium niobate thin film 410 has a thickness of 250 nm; the lithium niobate ridge waveguide 420 has a thickness (including the thickness of the lithium niobate thin film 410) of 500 nm, and a width of 700 nm depending on the wavelength of the light wave and the etching depth.

[0086] Among the other parameters, G=3.5um, H=2um, p0=61.1um, p1=64.1um, p2=67.1um, p3=70.1um, p4=p5=73.1um, lw=la=100um, g=3um, Rx1=254.25um, Rx2=140um, Ry1=1500um, Ry2=600um, D=0.

[0087] Correspondingly, the antenna array spacing d = px = g + Rx1 2 = 511.5um, and the size of the antenna element is: 1500um (length, py) × 511.5um (width, px) × 500nm (height).

[0088] Based on the relationship between the phase difference Φ between adjacent antenna array elements and the terahertz beam steering angle θ: The theoretical maximum turning angle of terahertz waves can be calculated. = 38.96°, and the phase difference Φ = ±139° required to reach the maximum steering angle.

[0089] Figure 6 and Figure 7 This is a simulation of the 360GHz terahertz far-field radiation pattern obtained from a terahertz phased array system using the above structural parameters. (Example:) Figure 6 As shown, when the phase difference Φ is 0, the terahertz beam points to the normal direction of the array, the steering angle is 0, and no grating lobes appear. Figure 7 As shown, when the phase difference Φ is 139°, the terahertz beam deflects to one side of the array, with a turning angle of 39°, which is consistent with the theoretical result. Furthermore, the beam intensity is significantly enhanced at an angle of -90°, where grating lobes just begin to appear, but there are no grating lobes at other positions. Considering that the phase difference Φ ranges from -180° to +180°, the maximum scanning range achievable by the terahertz phased array at this point is ±39°, thus achieving a wide scanning angle without grating lobes.

[0090] Finally, it should be noted that although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art, guided by this specification, can make many other forms without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A terahertz generation and radiation device based on a double elliptical conical slot antenna, characterized in that, It is equipped with a terahertz generator and a terahertz radiator; The terahertz generating unit is used to convert light waves into terahertz waves, and includes: The second-order nonlinear material waveguide layer has a continuous thin film and multiple equally spaced parallel ridge waveguides formed on the continuous thin film. Multiple electrode units are provided, each electrode unit comprising a metal electrode formed on a continuous thin film surface and symmetrically arranged on both sides of a ridge waveguide. The metal electrode consists of an electrode body and multiple T-shaped structures connected to the same side of the electrode body and arranged at equal intervals. The metal electrode is divided into an adjacent uniform electrode region and a gradient electrode region. In the uniform electrode region, the horizontal side lengths of the T-shaped structures are equal, while in the gradient electrode region, the horizontal side lengths of the T-shaped structures gradually increase from the uniform electrode region until the horizontal sides of adjacent T-shaped structures are connected. The terahertz radiating section is used to radiate the terahertz wave into free space, and includes: An antenna array has multiple antenna elements arranged at equal periods. Each antenna element includes an antenna radiating arm formed on a continuous thin film surface and symmetrically arranged on both sides of a ridge waveguide, and a double elliptical conical slot located between two antenna radiating arms. The inner and outer edges of the antenna radiating arms are both quarter-elliptical profiles. The width of the double elliptical conical slot gradually increases from the coupling end to the radiating end of the antenna radiating arm. The maximum aperture of the antenna element is not less than λ / 2, where λ is the wavelength of the terahertz wave. In the electrode unit, there is an inter-electrode physical gap G between adjacent metal electrodes; in the antenna unit, there is an antenna coupling end physical gap g between adjacent antenna radiating arms.

2. The terahertz generating and radiating device as described in claim 1, characterized in that, The terahertz radiating section also includes: The groove transition region has a connecting portion formed on the surface of a continuous thin film and symmetrically arranged on both sides of the ridge waveguide, and a groove line located between the two connecting portions; the two ends of the connecting portion are respectively connected to a metal electrode and an antenna radiating arm, and the shape of the groove line is defined by the inner edges of the two connecting portions.

3. The terahertz generating and radiating device as described in claim 2, characterized in that, The groove is constructed as a tapered gradient groove; the width of the tapered gradient groove at one end of the metal electrode is equal to the size of the physical gap G between the electrodes, and the width at the other end is equal to the size of the physical gap g at the antenna coupling end, and its width gradually narrows or widens from the metal electrode to the antenna radiating arm.

4. The terahertz generating and radiating device as described in claim 3, characterized in that, The groove line is constructed to include a uniform groove line connected to the end of the tapered groove line away from the metal electrode; the width of the uniform groove line is equal to the size of the physical gap g at the antenna coupling end.

5. The terahertz generating and radiating device as described in claim 2, characterized in that, The slot line is constructed as a uniform slot line, the width of which is equal to the size of the physical gap G between the electrodes, and the physical gap g at the antenna coupling end is equal to the physical gap G between the electrodes.

6. The terahertz generating and radiating device according to any one of claims 1 to 5, characterized in that, The period d of the antenna array satisfies λ / 2 < d < λ, and the relationship between the period d and the terahertz beam steering angle θ satisfies .

7. The terahertz generating and radiating device according to any one of claims 1 to 5, characterized in that, In the antenna array, the physical gap D between adjacent antenna elements is 0, and the period d is equal to the maximum aperture of the antenna element.

8. The terahertz generating and radiating device according to any one of claims 1 to 5, characterized in that, The waveguide layer has an x-cut half-etched structure; the second-order nonlinear material is lithium niobate.

9. The terahertz generating and radiating device according to any one of claims 1 to 5, characterized in that, The metal electrode, antenna radiating arm, and connecting part are made of the same metal material, which can be any one of aluminum, copper, or gold.

10. A terahertz phased array system based on a double elliptical conical slot antenna, characterized in that, It includes an optical wave control unit and a terahertz generating and radiating device as described in any one of claims 1 to 9; the optical wave control unit is equipped with a power divider assembly and a phase shifter assembly; The power divider assembly has multiple cascaded one-to-two power dividers, and the one-to-two power dividers are on-chip power dividers formed on a continuous thin film surface and based on the second-order nonlinear material. The phase shifter assembly has multiple phase shifters corresponding one-to-one with the ridge waveguide. The phase shifters are on-chip phase shifters formed on the surface of a continuous thin film and based on the second-order nonlinear material.

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