A light-controlled terahertz dual-microring echo-wall mode coupling system and a phase delay modulation method

Abstract

The application discloses a light-controlled terahertz double-microring echo-wall mode coupling system and a phase delay modulation method, and the system comprises a first echo-wall mode microring, a second echo-wall mode microring, a straight waveguide and two end taper type coupling waveguides integrated on the same high-resistance silicon substrate. The two microrings are located on the same side of the straight waveguide, the second echo-wall mode microring is directly evanescently coupled with the straight waveguide, and the first echo-wall mode microring is indirectly evanescently coupled with the second echo-wall mode microring, so that a double-resonance interference response is formed when the resonant frequencies are close. A solid-state laser source selectively irradiates a local annular waveguide region of the first echo-wall mode microring, changes the inherent loss through a photo-generated carrier effect, and reconfigures the system complex transmission response under the condition that the geometric coupling distance between the straight waveguide and the microring is unchanged. The application can realize the continuous adjustment of the transmission phase slope and the group delay while approximately maintaining the transmission amplitude at the interference center.

Description

Technical Field

[0001] This invention relates to the field of terahertz signal modulation and integrated photonic devices, specifically to a light-controlled terahertz dual-micro-loop whispering-gallery mode coupling system and a method for dynamically modulating transmission phase and group delay using the photogenerated carrier effect. Background Technology

[0002] Terahertz waves (0.1-10 THz) are an important frequency band bridging microwaves and infrared, and have wide applications in high-speed communication, non-destructive imaging, spectral analysis, and radar sensing. As terahertz systems evolve from simple transmission and detection to on-chip integration, reconfigurable transmission, and complex signal processing, active control of the phase, dispersion, and propagation time of terahertz signals, in addition to transmission amplitude, is gradually becoming a key requirement in system-level applications.

[0003] Whisper-gallery mode microring resonators possess high quality factors and strong electromagnetic field localization capabilities. Frequency selection, filtering, and phase response adjustment can be achieved through evanescent field coupling between a straight waveguide and the microring. Existing single-microring optical control schemes typically modify the microring loss by using photogenerated carriers, allowing the device to vary between overcoupled, critically coupled, and undercoupled states, thus achieving a large amplitude modulation depth. However, the amplitude and phase responses of such schemes usually change significantly simultaneously, which limits their application when independent phase or group delay adjustment is required under low-additional-loss conditions.

[0004] By employing two resonant units to form a coupled resonant system, the transmission spectrum and phase dispersion can be altered through energy exchange and coherent interference between different resonant channels. When the resonant frequencies of the two microrings are close to each other, the coupled system can form a double resonance and an intermediate interference region, making the transmission amplitude and phase differently sensitive to parameters such as coupling strength and inherent loss. Therefore, by selectively adjusting the loss of one of the microrings, it is possible to change the transmission phase slope and group delay without significantly altering the direct transmission amplitude, providing a new approach for low-loss terahertz phase modulation and tunable delay.

[0005] Photoconductivity modulation utilizes pump light to generate photogenerated carriers in semiconductor materials, enabling rapid changes in material conductivity and terahertz absorption loss without introducing on-chip electrodes and heaters. It features non-contact operation, simple structure, and ease of localized modulation. However, combining photoconductivity modulation with an on-chip dual-microring coupled resonant structure, and ensuring that the pump primarily acts on a single resonant unit to reconstruct the coupled interference phase and group delay using controllable losses while maintaining approximately stable transmission amplitude, still requires appropriate device structures, coupling relationships, and modulation methods. Summary of the Invention

[0006] The purpose of this invention is to provide an optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system and a phase delay modulation method. By selectively optically pumping one of the micro-rings in the dual micro-rings, its inherent loss is continuously changed while maintaining the geometric coupling relationship of the device. Active reconstruction of the terahertz signal transmission phase and group delay is achieved by using dual-micro-ring mode interference.

[0007] The technical solution to achieve the purpose of this invention is: a light-controlled terahertz dual-micro-ring whispering-gallery mode coupling system, comprising:

[0008] A dual-micro-ring whispering-gallery mode waveguide chip, integrated on the same substrate, includes a first whispering-gallery mode microring, a second whispering-gallery mode microring, a straight waveguide, and a first tapered coupling waveguide and a second tapered coupling waveguide located at opposite ends of the straight waveguide. The first whispering-gallery mode microring and the second whispering-gallery mode microring are both located on the same side of the straight waveguide. The second whispering-gallery mode microring is close to the straight waveguide and exchanges evanescent wave energy with it. The first whispering-gallery mode microring is located on the side of the second whispering-gallery mode microring away from the straight waveguide and is coupled to the second whispering-gallery mode microring through the evanescent field between the microrings.

[0009] A solid-state laser source has its fiber optic output end positioned above the first whispering-gallery mode microring, so that the pump light mainly irradiates a local region of the annular waveguide on the side of the first whispering-gallery mode microring that is far from the coupling region of the second whispering-gallery mode microring, thereby reducing direct irradiation of the second whispering-gallery mode microring and the straight waveguide. The pump light changes the equivalent conductivity and inherent loss of the first whispering-gallery mode microring through the photogenerated carrier effect, and dynamically adjusts the complex transmission response of the dual-microring coupling system while keeping the geometric coupling distance between the straight waveguide and the microring constant.

[0010] Furthermore, the substrate, the first whispering-gallery mode microring, the second whispering-gallery mode microring, the straight waveguide, the first tapered coupling waveguide, and the second tapered coupling waveguide are all made of high-resistivity silicon material and are integrally formed on the same silicon wafer through deep silicon etching process.

[0011] Furthermore, the first and second tapered coupled waveguides gradually transition from the width of the waveguide inside the chip to the outer tip, and are used to insert into a standard rectangular waveguide to complete mode conversion.

[0012] Furthermore, the radius of the first whispering-gallery mode microring is larger than that of the second whispering-gallery mode microring, and the waveguide widths and ridge heights of the straight waveguide, the first whispering-gallery mode microring, and the second whispering-gallery mode microring are equal, so that the three waveguide structures have matching mode effective refractive indices.

[0013] Furthermore, a first coupling gap g1 is provided between the second whispering-gallery mode microring and the straight waveguide, and a second coupling gap g2 is provided between the first whispering-gallery mode microring and the second whispering-gallery mode microring; by setting g1 and g2 respectively, the second whispering-gallery mode microring forms a resonant channel directly coupled to the straight waveguide, and the first whispering-gallery mode microring forms a resonant channel indirectly coupled through the second whispering-gallery mode microring.

[0014] Furthermore, by setting the radii of the first and second whispering-gallery mode microrings, as well as the first and second coupling distances, at least one set of whispering-gallery mode resonant frequencies of the first and second whispering-gallery mode microrings are brought close to each other, and a double-resonance transmission response formed by mode coupling and interference and an interference center located between the double resonators are generated within this frequency range.

[0015] Furthermore, the pump light generated by the solid-state laser source excites electron-hole pairs in the high-resistivity silicon, causing the equivalent conductivity of the first whispering-gallery mode microring to increase with the increase of the photogenerated carrier concentration. The relationship between the equivalent conductivity σ and the photogenerated carrier concentration Δn satisfies σ = qΔn(μ e +μ h ), where q is the charge, Δn is the concentration of photogenerated electrons and the concentration of photogenerated holes, and the concentration of photogenerated electrons is equal to the concentration of photogenerated holes, μ e and μ h These are electron mobility and hole mobility, respectively.

[0016] Furthermore, by continuously adjusting the output power of the solid-state laser source, the inherent loss of the first whispering-gallery mode microring is continuously varied, while the first coupling spacing g1, the second coupling spacing g2, and the coupling strength determined by the geometry remain constant or approximately constant. This continuously alters the interference relationship between the resonant channels of the first and second whispering-gallery mode microrings. Furthermore, near the interference center between the two resonators, with variations in pump power, the transmission amplitude of the terahertz signal output from the second tapered coupled waveguide remains within a preset range, while the transmission phase slope and group delay continuously change; the group delay τ... g Determined by the rate of change of the transmission phase φ relative to the angular frequency ω, satisfying τ g =-dφ / dω.

[0017] A terahertz signal phase delay modulation method, based on the aforementioned optically controlled terahertz dual-micro-loop whispering-gallery mode coupling system, the method comprising:

[0018] A terahertz signal is input into the first tapered coupled waveguide, and the terahertz signal is coupled into the second whispering-gallery mode microring through the straight waveguide, and further coupled into the first whispering-gallery mode microring. A coupled resonant interference response is formed in the frequency range where the resonant frequencies of the first whispering-gallery mode microring and the second whispering-gallery mode microring are close.

[0019] The pump light output from the solid-state laser source is controlled to selectively irradiate the first whispering-gallery mode microring, and the inherent loss of the first whispering-gallery mode microring is changed by using photogenerated carriers.

[0020] Adjusting the pump light power to change the interference relationship between the two micro-ring resonant channels, and reconstructing the transmission phase frequency response while keeping the transmission amplitude at the interference center approximately stable;

[0021] The second tapered coupled waveguide outputs a modulated terahertz signal to achieve at least one of the following functions: phase modulation, group delay adjustment, dispersion control, and tunable filtering.

[0022] Compared with the prior art, the significant advantages of this invention are:

[0023] 1) Phase modulation under low additional amplitude loss conditions is achieved: by using the interference center generated by the dual micro-ring coupling, the output amplitude and phase have different sensitivities to the pumped micro-ring loss; when the pump power changes, the transmission amplitude of the interference center can only change slightly, while the phase frequency response and phase slope are significantly reconstructed, overcoming the problem of synchronous enhancement of amplitude loss and phase change in single absorption modulation.

[0024] 2) Achieves continuous reconfigurable adjustment of group delay: Group delay is determined by the derivative of the transmission phase with respect to the angular frequency. This invention continuously changes the interference of the dual micro-ring mode by adjusting the inherent loss of a micro-ring, thereby achieving continuous adjustment from a larger positive group delay to a smaller group delay on the same chip without changing the device geometry. It can be used for on-chip terahertz delay and dispersion control.

[0025] 3) It realizes the combination of selective optical pumping and coupled resonant modulation: the pump fiber is positioned on the side away from the coupling region between micro-rings, and only illuminates the local ring waveguide of the first whispering-gallery mode micro-ring, which can reduce the direct impact of pumping on the second whispering-gallery mode micro-ring and the straight waveguide; at the same time, the loss of the pumped micro-ring is changed by utilizing the photogenerated carrier effect of high-resistivity silicon, without the need to add electrodes, heaters or mechanical actuators on the chip.

[0026] 4) Ensures on-chip integration and system compatibility: Two whispering-gallery mode microrings, straight waveguides and tapered coupling waveguides can be integrally fabricated on the same high-resistivity silicon substrate; the first tapered coupling waveguide and the second tapered coupling waveguide can be docked with WR series rectangular waveguides; the optical fiber can be fixed above the microring through the positioning holes of the packaging shell, thus forming a compact, easy-to-package functional device that can be connected to existing terahertz vector network analysis and system platforms. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of a light-controlled terahertz dual-micro-ring whispering-gallery mode coupling system.

[0028] Figure 2 This is a schematic diagram of the dimensions of a light-controlled terahertz dual-micro-ring whispering-gallery mode coupling system.

[0029] Figure 3 The transmission spectrum test results of the optically controlled terahertz dual micro-loop whispering-gallery mode coupled system under different pump powers.

[0030] Figure 4 The transmission phase test results are for an optically controlled terahertz dual-micro-loop whispering-gallery mode coupled system under different pump powers.

[0031] Figure 5 The results show the group delay of the optically controlled terahertz dual-micro-loop whispering-gallery mode coupled system under different pump powers. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0033] like Figure 1-2 As shown, a light-controlled terahertz dual-micro-ring whispering-gallery mode coupling system is integrated with a solid-state laser source at the fiber optic output end 1 and a dual-micro-ring whispering-gallery mode waveguide chip, wherein:

[0034] The dual-microring whispering-gallery mode waveguide chip includes a first whispering-gallery mode microring 2, a second whispering-gallery mode microring 3, a first tapered coupling waveguide 4, a substrate 5, a second tapered coupling waveguide 6, and a straight waveguide 7. Both the first whispering-gallery mode microring 2 and the second whispering-gallery mode microring 3 adopt a ring-shaped waveguide structure and are located on the same side of the straight waveguide 7; the first whispering-gallery mode microring 2 is located on top and has a larger radius, while the second whispering-gallery mode microring 3 is located between the first whispering-gallery mode microring 2 and the straight waveguide 7 and has a smaller radius. A first coupling distance g1 is maintained between the straight waveguide 7 and the second whispering-gallery mode microring 3, and a second coupling distance g2 is maintained between the two microrings, thus forming a successive evanescent field coupling relationship of "straight waveguide - second whispering-gallery mode microring - first whispering-gallery mode microring".

[0035] A straight waveguide 7 is used to transmit terahertz signals. Its two ends are connected to a first tapered coupled waveguide 4 and a second tapered coupled waveguide 6, respectively, serving as the input and output ports for the terahertz signals. Two whispering-gallery mode microrings 2 and 3 with different radii, the straight waveguide 7, and the first tapered coupled waveguide 4 and the second tapered coupled waveguide 6 located at both ends of the straight waveguide are integrated on the same high-resistivity silicon substrate. The two microrings are both located on the same side of the straight waveguide 7. The second whispering-gallery mode microring 3, which is closer to the straight waveguide 7, is evanescently coupled to the straight waveguide 7 through a first coupling gap g1. The first whispering-gallery mode microring 2, which is farther from the straight waveguide 7, is evanescently coupled to the second whispering-gallery mode microring 3 through a second coupling gap g2. After the terahertz signal enters the straight waveguide 7 through the first tapered coupling waveguide 4, the frequency component that satisfies the resonance condition of the second whispering-gallery mode microring 3 is coupled into the second whispering-gallery mode microring 3 through the evanescent field, and further coupled into the first whispering-gallery mode microring 2 through g2; by designing the radii of the two microrings and g1 and g2, at least one set of whispering-gallery modes is coupled near the target terahertz frequency and forms a double resonant interference response.

[0036] For a circular whispering-gallery mode microring with radius r, its resonance condition can be expressed as mλ = 2πrn. eff Where m is the whispering gallery mode order, λ is the vacuum wavelength, and n eff The effective refractive index corresponds to the waveguide mode. By setting the radii of the two micro-rings respectively, at least one of the two sets of discrete whispering-gallery modes is made close to each other in the target operating frequency band, providing the frequency conditions for forming coupled resonant interference.

[0037] The fiber emitting end 1 of the solid-state laser source is positioned above the first whispering-gallery mode microring 2 via a fixed structure, so that the pump spot falls on a local region of the annular waveguide on the side of the first whispering-gallery mode microring away from the coupling region of the second whispering-gallery mode microring. The fiber emitting from the solid-state laser source is positioned above the first whispering-gallery mode microring and illuminates its annular waveguide region. The pump power is adjusted to change the photogenerated carrier concentration and inherent loss in the first whispering-gallery mode microring 2. Since the geometry and coupling distance between the straight waveguide and the microring do not change with pumping, pumping mainly alters the energy exchange and interference conditions between the two microrings through the loss dimension, thereby reconstructing the transmission phase and group delay of the output terahertz signal. This arrangement allows pumping to primarily change the material conductivity and inherent loss of the first whispering-gallery mode microring 2, while having a relatively small impact on the direct illumination of the second whispering-gallery mode microring 3 and the straight waveguide 7.

[0038] The optimization design and control mechanism of each part will be explained in detail below.

[0039] (1) Dual-micro-ring whispering-gallery mode waveguide chip

[0040] High-resistivity silicon exhibits low dielectric loss in the terahertz band and can be etched into ridge waveguide structures on the scale of hundreds of micrometers through deep silicon etching. Therefore, this embodiment uses high-resistivity silicon as the chip material. The first whispering-gallery mode microring 2, the second whispering-gallery mode microring 3, the straight waveguide 7, and the first tapered coupling waveguide 4 and the second tapered coupling waveguide 6 are fabricated on the same high-resistivity silicon wafer. The relative positions of the two microrings and the straight waveguide are defined by the same set of photolithography and etching processes to improve the consistency of coupling spacings g1 and g2 and the repeatability of the device.

[0041] The effective refractive index of a dielectric waveguide is related to the material, waveguide width, and cross-sectional height. To ensure mode matching between the straight waveguide and the two microrings, this invention sets the straight waveguide 7, the first whispering-gallery mode microring 2, and the second whispering-gallery mode microring 3 to have the same ridge waveguide cross-section. Figure 2 In one embodiment shown, the waveguide width w is 200 μm, the total thickness t of the silicon substrate is 200 μm, the ridge height h2 is 140 μm, and the thickness h1 of the lower silicon layer is 60 μm. The radius R2 of the upper first whispering-gallery mode microring 2 is larger than the radius R1 of the lower second whispering-gallery mode microring 3. In a specific embodiment, R2 is 2.5 mm and R1 is 1.9 mm. The first coupling spacing g1 and the second coupling spacing g2 are set according to the target coupling coefficient. In this embodiment, g1 is 30 μm and g2 is 25 μm.

[0042] The first coupling spacing g1 is used to determine the external coupling strength between the straight waveguide 7 and the second whispering-gallery mode microring 3, and the second coupling spacing g2 is used to determine the coherent coupling strength between the two microrings. In the design, g1 is first used to obtain a stable coupling between the straight waveguide and the second whispering-gallery mode microring 3, and then g2 is used to adjust the mode exchange between the two microrings so that a resolvable double resonance and intermediate interference response are formed near the target resonance.

[0043] When describing the complex transmission coefficient near the target resonance using time-domain coupled-mode theory, it can be written as t(ω) = 1 - 2γ e / [j(ω-ω1)+(γ1+γ e )+μ² / (j(ω-ω2)+γ2)], where ω1 and ω2 represent the resonant angular frequencies of the second whispering-gallery mode microring 3 and the first whispering-gallery mode microring 2, respectively, and γ1 and γ2 represent the inherent loss rates of the second whispering-gallery mode microring 3 and the first whispering-gallery mode microring 2, respectively. e γ represents the external coupling ratio between the second whispering-gallery mode microring 3 and the straight waveguide 7, and μ represents the coupling ratio between the two microrings. This relationship shows that, with ω1, ω2, and the geometric coupling parameters approximately constant, changing γ2 can redistribute the amplitude and phase contributions of the resonant channel, thereby reconstructing the output complex transmission response.

[0044] (2) Photogenerated carrier loss regulation

[0045] The band gap of silicon at room temperature is approximately 1.12 eV. When the pump photon energy is higher than this band gap, electron-hole pairs are generated in the first whispering-gallery mode microring 2. If the concentration of photogenerated electrons and the concentration of photogenerated holes are equal, both denoted as Δn, then the equivalent conductivity can be expressed as σ = qΔn(μ e +μ h ), where q is the charge, μ e μ h These represent electron and hole mobility, respectively. As pump power increases, the concentration of photogenerated carriers and the absorption of free carriers in the terahertz band increase, leading to an increase in the equivalent intrinsic loss γ2 of the first whispering-gallery mode microring 2.

[0046] The control process of this invention does not require changing the geometry of g1, g2, or the micro-rings; therefore, the external coupling rate γ, determined by the geometric relationship, is... e The coupling ratio μ between the microrings remains relatively stable during the pumping process, with the main variation being the inherent loss γ2 of the pumped first whispering-gallery mode microring 2. By applying loss modulation to the indirectly coupled microrings, the phase slope of the complex transmission function can be changed near the intermediate interference frequency, thus avoiding the direct superposition of all optical losses onto the through transmission channel.

[0047] The group delay of a terahertz signal is determined by the transmission phase φ, and can be expressed as τ. g=-dφ / dω. Therefore, when the pump changes the dual-micro-ring interference conditions and the phase-frequency curve gradually flattens from steep, the corresponding positive group delay decreases synchronously. Under appropriate g1, g2, and loss matching conditions, the transmission amplitude at the interference center changes only slightly, while the phase slope and group delay have a large adjustable range, thereby achieving phase and time delay control with approximate amplitude preservation.

[0048] (3) Conical coupling and fiber positioning structure

[0049] The first tapered coupling waveguide 4 and the second tapered coupling waveguide 6 serve as the terahertz signal input and output ports, and are symmetrically arranged left and right along the extension direction of the straight waveguide 7. The tapered coupling waveguides gradually transition from the width of the waveguide inside the chip to the outer tip, and can be inserted into the WR series rectangular waveguides to complete the conversion between the metal waveguide mode and the high-resistivity silicon dielectric waveguide mode. The length L of the tapered waveguide can be determined according to the operating frequency band and the size of the rectangular waveguide; in one embodiment, L is approximately 1.2 mm.

[0050] The optical fiber output end 1 is fixed above the first whispering-gallery mode microring 2 through a positioning through-hole in the encapsulation shell. The end face of the optical fiber maintains a preset distance from the chip, so that the light spot covers a local waveguide of the first whispering-gallery mode microring 2. The pump wavelength is selected to be able to generate photogenerated carriers in high-resistivity silicon. In this embodiment, a 655 nm solid-state laser source is used. The light spot size matches the local waveguide region of the first whispering-gallery mode microring 2. In this embodiment, the light spot diameter is approximately 0.2 mm, and the pump power is continuously adjustable in the mW range.

[0051] To verify the effectiveness of the present invention, a dual-micro-ring whispering-gallery mode coupling system was fabricated and packaged according to the following process:

[0052] 1. The high-resistivity silicon wafer is thinned to achieve the target total thickness; in one embodiment, the total thickness t is 200 μm;

[0053] 2. A straight waveguide 7, a first whispering-gallery mode microring 2, a second whispering-gallery mode microring 3 and their ridge-shaped cross-sections are formed using photolithography and deep silicon etching processes, and a first coupling spacing g1 and a second coupling spacing g2 are defined by the same layout.

[0054] 3. Form the first tapered coupled waveguide 4 and the second tapered coupled waveguide 6 and complete the chip cutting. Design a rectangular waveguide package and pump light positioning structure according to the chip size and fiber position for scattering parameter and group delay testing.

[0055] The packaged optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system was connected to a vector network analyzer and a corresponding terahertz spread spectrum module. The first tapered coupling waveguide 4 served as the signal input, and the second tapered coupling waveguide 6 served as the signal output. The fiber optic output end 1 of the solid-state laser source was fixed above the first whispering-gallery mode micro-ring 2. Complex S-wavelengths were tested at different pump powers within the 400-408 GHz range. 21 The transmission amplitude, transmission phase, and group delay are obtained respectively.

[0056] Figure 3 The transmission spectra at pump powers of 0 mW, 9.8 mW, and 24.2 mW are presented. The dual-micro-ring coupled system forms two adjacent resonances near approximately 403 GHz and 404.4 GHz, with an interference center between them. With increasing pump power, the two resonances and the intermediate transmission level change only to a limited extent; taking the area near approximately 403.8 GHz as an example, the S-values ​​at 0 mW, 9.8 mW, and 24.2 mW are shown. 21 The losses are approximately -4.80 dB, -5.07 dB, and -5.38 dB, respectively, with an additional loss of approximately 0.6 dB for 24.2 mW relative to the unpumped state.

[0057] Figure 4 The transmission phase under the corresponding pump power is given. Although the transmission amplitude changes little near the interference center, the phase-frequency curve is significantly reconstructed with the pump power: the unpumped state has a steep phase slope between the two resonances, and as the pump power increases, the phase curve gradually widens and flattens, indicating that the increased loss of the pumped microring changes the interference relationship between the two resonant channels.

[0058] Figure 5 The complex number S is given 21 The group delay test results obtained from the phase analysis show that near the interference center, the peak group delay in the unpumped state is approximately 0.94 ns; the group delay decreases to approximately 0.49 ns with a pump power of 9.8 mW; and further decreases to approximately 0.03 ns with a pump power of 24.2 mW. This demonstrates that the present invention achieves continuous adjustment of the group delay over a wide range under conditions of relatively small additional changes in transmission amplitude, verifying the effectiveness of phase and time response reconstruction through selective loss modulation. The main degree of freedom of adjustment comes from the optically induced loss of the pumped microring, without relying on mechanical changes to the coupling spacing or overall thermally induced frequency shift.

[0059] The embodiments of the present invention are not limited to the described examples. Without departing from the essence and principle of the present invention, the radius, coupling spacing, waveguide cross-section, pump wavelength, and pump position of the two whispering-gallery mode microrings can all be adjusted according to the target operating frequency band; the first whispering-gallery mode microring can also adopt a local racetrack type or other closed dielectric waveguide structure capable of forming a whispering-gallery mode.

[0060] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described one by one. However, as long as there is no contradiction in the combination of these technical features, they should all be considered to be within the scope of this specification.

[0061] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection of this invention patent. For those skilled in the art, various modifications and improvements can be made without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the appended claims.

Claims

1. A light-controlled terahertz dual-micro-ring whispering-gallery mode coupling system, characterized in that, include: The dual-micro-ring whispering-gallery mode waveguide chip is integrated on the same substrate and includes a first whispering-gallery mode micro-ring (2), a second whispering-gallery mode micro-ring (3), a straight waveguide (7), and a first tapered coupling waveguide (4) and a second tapered coupling waveguide (6) located at both ends of the straight waveguide (7); the first whispering-gallery mode micro-ring and the second whispering-gallery mode micro-ring are both located on the same side of the straight waveguide (7), the second whispering-gallery mode micro-ring (3) is close to the straight waveguide (7) and exchanges evanescent wave energy with the straight waveguide, the first whispering-gallery mode micro-ring (2) is located on the side of the second whispering-gallery mode micro-ring (3) away from the straight waveguide, and is coupled to the second whispering-gallery mode micro-ring (3) through the evanescent field between the micro-rings; The solid-state laser source has its fiber output end (1) positioned above the first whispering-gallery mode microring (2), so that the pump light mainly irradiates the local area of ​​the annular waveguide on the side of the first whispering-gallery mode microring (2) that is far from the coupling area of ​​the second whispering-gallery mode microring (3), so as to reduce the direct irradiation of the second whispering-gallery mode microring (3) and the straight waveguide (7). The pump light changes the equivalent conductivity and inherent loss of the first whispering-gallery mode microring (2) through the photogenerated carrier effect, and dynamically adjusts the complex transmission response of the dual microring coupling system under the condition that the geometric coupling distance between the straight waveguide and the microring remains unchanged.

2. The optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system according to claim 1, characterized in that, The substrate (5), the first whispering-gallery mode microring (2), the second whispering-gallery mode microring (3), the straight waveguide (7), the first tapered coupling waveguide (4), and the second tapered coupling waveguide (6) are all made of high-resistivity silicon material and are integrally formed on the same silicon wafer by deep silicon etching process.

3. The optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system according to claim 1, characterized in that, The first tapered coupling waveguide (4) and the second tapered coupling waveguide (6) gradually transition from the width of the waveguide inside the chip to the outer tip, and are used to insert into the standard rectangular waveguide to complete the mode conversion.

4. The optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system according to claim 1, characterized in that, The radius of the first whispering-gallery mode microring (2) is greater than that of the second whispering-gallery mode microring (3), and the waveguide widths and ridge heights of the straight waveguide (7), the first whispering-gallery mode microring (2), and the second whispering-gallery mode microring (3) are equal, so that the three waveguide structures have matching effective refractive indices of the modes.

5. The optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system according to claim 1, characterized in that, A first coupling gap g1 is provided between the second whispering-gallery mode microring (3) and the straight waveguide (7), and a second coupling gap g2 is provided between the first whispering-gallery mode microring (2) and the second whispering-gallery mode microring (3). By setting g1 and g2 respectively, the second whispering-gallery mode microring (3) forms a resonant channel directly coupled to the straight waveguide, and the first whispering-gallery mode microring (2) forms a resonant channel indirectly coupled through the second whispering-gallery mode microring (3).

6. The optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system according to claim 5, characterized in that, By setting the radii of the first whispering-gallery mode microring (2) and the second whispering-gallery mode microring (3), as well as the first coupling distance and the second coupling distance, at least one set of whispering-gallery mode resonant frequencies of the first whispering-gallery mode microring (2) and the second whispering-gallery mode microring (3) are made close to each other, and a double resonant transmission response formed by mode coupling and interference and an interference center located between the double resonators are generated within the frequency range.

7. The optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system according to claim 1, characterized in that, The pump light generated by the solid-state laser source excites electron-hole pairs in high-resistivity silicon, causing the equivalent conductivity of the first whispering-gallery mode microring (2) to increase with the increase of the photogenerated carrier concentration. The relationship between the equivalent conductivity σ and the photogenerated carrier concentration Δn satisfies σ=qΔn(μ e +μ h ), where q is the charge, Δn is the concentration of photogenerated electrons and the concentration of photogenerated holes, and the concentration of photogenerated electrons is equal to the concentration of photogenerated holes, μ e and μ h These are electron mobility and hole mobility, respectively.

8. The optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system according to claim 7, characterized in that, By continuously adjusting the output power of the solid-state laser source, the inherent loss of the first whispering-gallery mode microring (2) is continuously changed, while the first coupling distance g1, the second coupling distance g2, and the coupling strength determined by the geometry remain unchanged or approximately unchanged. This continuously changes the interference relationship between the resonant channels of the first whispering-gallery mode microring (2) and the second whispering-gallery mode microring (3).

9. The optically controlled terahertz dual-micro-ring whispering-gallery mode coupling system according to claim 8, characterized in that, Near the interference center between the two resonances, as the pump power changes, the transmission amplitude of the terahertz signal output by the second tapered coupled waveguide (6) remains within a preset range, while the transmission phase slope and group delay change continuously; the group delay τ g Determined by the rate of change of the transmission phase φ relative to the angular frequency ω, satisfying τ g =-dφ / dω.

10. A terahertz signal phase delay modulation method, based on the optically controlled terahertz dual-micro-loop whispering-gallery mode coupling system according to any one of claims 1 to 9, characterized in that, The method includes: A terahertz signal is input into the first tapered coupled waveguide (4), and the terahertz signal is coupled into the second whispering-gallery mode microring (3) through the straight waveguide (7), and further coupled into the first whispering-gallery mode microring (2). A coupled resonance interference response is formed in the frequency range where the resonant frequencies of the first whispering-gallery mode microring (2) and the second whispering-gallery mode microring (3) are close. Control the output pump light of the solid-state laser source to selectively irradiate the first whispering-gallery mode microring (2), and use photogenerated carriers to change the inherent loss of the first whispering-gallery mode microring (2); Adjusting the pump light power to change the interference relationship between the two micro-ring resonant channels, and reconstructing the transmission phase frequency response while keeping the transmission amplitude at the interference center approximately stable; The second tapered coupled waveguide (6) outputs a modulated terahertz signal to achieve at least one of the following functions: phase modulation, group delay adjustment, dispersion control, and tunable filtering.

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