Microwave resonance suppression device of broadband electro-optical modulator packaging structure

Abstract

The invention relates to the technical field of microwave photonics and high-speed optical communication device packaging, in particular to a microwave resonance suppression device of a broadband electro-optical modulator packaging structure, which comprises at least one air cavity structure arranged in a metal tube shell of a target broadband electro-optical modulator packaging structure. And the filter is located below a modulator chip of the target broadband electro-optical modulator packaging structure so as to shift the cut-off frequency of mode coupling of the target broadband electro-optical modulator packaging structure out of the working frequency band of the corresponding device. Therefore, the problems that an existing cavity resonance suppression scheme mostly depends on wave absorbing materials, high-temperature failure exists, extra microwave transmission loss is introduced, and the packaging size is large are solved.

Description

Technical Field

[0001] The present invention relates to the technical fields of microwave photonics and high-speed optical communication device packaging, and particularly relates to a microwave resonance suppression device for a broadband electro-optic modulator packaging structure. Background Art

[0002] Coplanar Waveguide (CPW) devices and Coplanar Stripline (CSL) devices are widely used in the fields of microwave photonics and high-speed optical communication. They have excellent characteristics such as large bandwidth, high-frequency response, low microwave transmission loss, low dispersion, and easy integration, and have become common microwave transmission structures for electro-optic modulators.

[0003] In the actual packaging of electro-optic modulators, electro-optic modulators with coplanar waveguide (CPW) electrodes and capacitively loaded travelling-wave electrodes (CL-TWEs) are usually welded to metal packages. The metal package not only helps to provide physical support for the device, but also helps the device to dissipate heat. However, as an additional ground plane, the metal package will excite parasitic modes such as microstrip line (MSL) mode and parallel plate line (PPL) mode. When the CPW main mode is phase-matched with these parasitic modes, strong mode coupling will occur. At this time, the electromagnetic energy is no longer confined to the electrode gap of the coplanar waveguide, but leaks to the dielectric substrate, resulting in a sharp increase in transmission loss and deterioration of the reflection coefficient at specific frequencies, severely restricting the electro-optic bandwidth and high-frequency transmission performance of the modulator.

[0004] Currently, the mainstream cavity resonance suppression schemes mostly rely on absorbing materials, but there are significant limitations, as follows: (1) Commercial absorbing materials usually have an effective frequency band of no more than 40 GHz, and the upper temperature limit is only 165 °C, making it difficult to withstand the high temperature requirements (≥230 °C) of some solders in the packaging welding process, and there is a risk of high-temperature failure; (2) Although the absorbing materials can suppress the microwave stray radiation in the cavity, they will introduce additional microwave transmission loss, thereby reducing the device performance; (3) Absorbing materials are usually large in volume, occupying the internal space of the package, and it is difficult to meet the requirements of miniaturized packaging.

[0005] Based on the above technical defects, there is an urgent need for a cavity resonance suppression scheme with wideband resonance suppression ability, low-loss characteristics, and compact packaging adaptability to break through the limitations of the current packaging structure on the performance of electro-optic modulator modules. Summary of the Invention

[0006] The present invention provides a microwave resonance suppression device for a broadband electro-optic modulator packaging structure to solve the problems that existing cavity resonance suppression schemes mostly rely on absorbing materials, resulting in high-temperature failure, introducing additional microwave transmission loss, and large packaging volume.

[0007] In a first aspect embodiment of the present invention, a microwave resonance suppression device for a broadband electro-optic modulator packaging structure is provided, including: at least one air cavity structure, which is disposed within a metal can of the target broadband electro-optic modulator packaging structure and is located below a modulator chip of the target broadband electro-optic modulator packaging structure, so as to shift the cut-off frequency of mode coupling of the target broadband electro-optic modulator packaging structure out of the operating frequency band of the corresponding device.

[0008] Optionally, the at least one air cavity structure is located below any one of a microwave input port of the modulator chip, below the microwave input port and the microwave output port, or below the entire section.

[0009] Optionally, the depth of the at least one air cavity structure is determined according to the dielectric constant of the modulator chip substrate and the device operating frequency.

[0010] In a second aspect embodiment of the present invention, a microwave resonance suppression device for a broadband electro-optic modulator packaging structure is provided. Based on the microwave resonance suppression device provided in the first aspect embodiment, it includes:

[0011] At least one short-circuit bonding wire, which is arranged periodically along the microwave transmission direction of the modulator chip and is connected to two top ground electrodes of the modulator chip, or is connected to one top ground electrode of the modulator chip and the metal can, or is connected to two top ground electrodes of the modulator chip, one top ground electrode and the metal can simultaneously, so as to increase the grounding continuity between the modulator chip and the metal can.

[0012] In a third aspect embodiment of the present invention, a microwave resonance suppression device for a broadband electro-optic modulator packaging structure is provided. Based on the microwave resonance suppression device provided in the first aspect embodiment, it includes:

[0013] At least two thin-film resistor circuit substrates, which are arranged along the microwave transmission direction of the modulator chip, are placed on the same side or both sides of the modulator chip, and are welded to the surface of the metal can, so as to dissipate the stray electromagnetic energy in the high-order parasitic mode of the target broadband electro-optic modulator packaging structure.

[0014] Optionally, each thin-film resistor circuit substrate includes a ground metal plate, a dielectric substrate, a surface metal layer, and a thin-film resistor. The thin-film resistor circuit substrate is connected to the metal package through the ground metal plate. The surface metal layer includes a metal pad and a ground metal layer. One end of the metal pad is connected to the ground metal layer through the thin-film resistor, and the other end of the metal pad is connected to a top ground electrode of the modulator chip.

[0015] Optionally, it further includes: at least one metal via hole that penetrates the dielectric substrate and forms a complete loop with the ground metal layer.

[0016] An embodiment of the fourth aspect of the present invention provides a microwave resonance suppression device for a broadband electro-optic modulator packaging structure. Based on the microwave resonance suppression device provided in the embodiment of the first aspect, it includes:

[0017] At least two thin-film resistor circuit substrates are arranged along the microwave transmission direction of the modulator chip, placed on the same side or both sides of the modulator chip, and welded to the surface of the metal package to dissipate the stray electromagnetic energy in the high-order parasitic modes of the target broadband electro-optic modulator packaging structure;

[0018] At least one shorting bond wire is periodically arranged along the microwave transmission direction of the modulator chip and is connected to two top ground electrodes of the modulator chip, or connected to one top ground electrode of the modulator chip and the metal package, or connected to two top ground electrodes of the modulator chip, or connected to one top ground electrode and the metal package, two top ground electrodes of the modulator chip, one top ground electrode and the metal package, and one top ground electrode and a thin-film resistor circuit substrate at the same time to increase the ground continuity between the modulator chip and the metal package.

[0019] Optionally, the thin-film resistor circuit substrate includes a ground metal plate, a dielectric substrate, a surface metal layer, and a thin-film resistor. The thin-film resistor circuit substrate is connected to the metal package through the ground metal plate. The surface metal layer includes a metal pad and a ground metal layer. One end of the metal pad is connected to the ground metal layer through the thin-film resistor, and the other end of the metal pad is connected to a top ground electrode of the modulator chip.

[0020] Optionally, it further includes: at least one metal via hole that penetrates the dielectric substrate and forms a complete loop with the ground metal layer.

[0021] The microwave resonance suppression device of the broadband electro-optic modulator packaging structure proposed in the embodiment of the present invention addresses the problems of high-order parasitic mode excitation and microwave resonance during the packaging process of electro-optic modulators and similar high-frequency devices. Based on the core design concept of a mode coupling suppressor with an air cavity structure, combined with various auxiliary means such as short-circuit wire bonding and thin-film resistor loading, it effectively suppresses parasitic modes such as microstrip line modes and planar transmission line modes excited during the packaging process, avoiding energy coupling between them and the CPW main mode, thereby achieving low-loss and broadband microwave transmission of the device; it does not rely on traditional absorbing materials, thus avoiding the risk of their failure in high-temperature environments and the requirement for packaging space, significantly reducing the packaging process complexity and packaging cost, and having the advantages of flexible structure design, unrestricted working frequency band, small implementation difficulty, high feasibility, etc.; by adjusting the shape, position, size, and number of the air cavity (mode coupling suppressor) structure, and synergistically optimizing the number and layout of short-circuit gold wires, the number, resistance value, and loading position of thin-film resistors, microwave resonance suppression in the frequency range from DC to hundreds of GHz can be effectively achieved without increasing additional volume.

[0022] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Brief Description of the Drawings

[0023] The above-mentioned or additional aspects and advantages of the present invention will become apparent and be easily understood from the following description of the embodiments in conjunction with the drawings, where:

[0024] Figure 1 is a schematic structural diagram of the first microwave resonance suppression device of the broadband electro-optic modulator packaging structure provided by the embodiment of the present invention;

[0025] Figure 2 is a schematic structural diagram of the second microwave resonance suppression device of the broadband electro-optic modulator packaging structure provided by the embodiment of the present invention, where (a) is connecting two top ground electrodes, (b) is connecting the top ground electrode and the metal package, and (c) is connecting two top ground electrodes simultaneously and connecting one top ground electrode and the metal package;

[0026] Figure 3 is a schematic structural diagram of the third microwave resonance suppression device of the broadband electro-optic modulator packaging structure provided by the embodiment of the present invention;

[0027] Figure 4 is a schematic structural diagram of a thin-film resistor circuit board provided by the embodiment of the present invention;

[0028] Figure 5 is a schematic structural diagram of the fourth microwave resonance suppression device of the broadband electro-optic modulator packaging structure provided by the embodiment of the present invention.

[0029] Description of reference numerals:

[0030] 10-microwave resonance suppression device of broadband electro-optic modulator packaging structure, 11-metal tube shell, 111-air cavity structure, 12-modulator chip, 121-top ground electrode, 122-signal electrode, 123-under the input port, 124-under the output port, 13-short-circuit bonding wire, 14-thin film resistor circuit substrate, 141-dielectric substrate, 1421-metal pad, 1422-ground metal layer, 143-thin film resistor and 144-metal through hole. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0032] The microwave resonance suppression device of the broadband electro-optic modulator packaging structure according to the embodiment of the present invention will be described below with reference to the accompanying drawings.

[0033] Figure 1 A schematic structural diagram of a microwave resonance suppression device of a first broadband electro-optic modulator packaging structure provided by an embodiment of the present invention.

[0034] like Figure 1 As shown, the microwave resonance suppression device 10 of the broadband electro-optic modulator packaging structure includes: at least one air cavity structure 111.

[0035] Among them, at least one air cavity structure 111 is placed in the metal tube shell 11 of the target broadband electro-optic modulator packaging structure and is located below the modulator chip 12 of the target broadband electro-optic modulator packaging structure to move the cutoff frequency of the mode coupling of the target broadband electro-optic modulator packaging structure out of the operating frequency band of the corresponding device.

[0036] In the actual implementation process, under the modulator chip 12 of the target broadband electro-optic modulator package structure, the metal tube shell 11 of the target broadband electro-optic modulator package structure can be locally micro-machined by high-precision metal milling process to obtain the air cavity structure 111. The air cavity structure 111 is used to adjust the effective refractive index of the MSL mode, optimize the electromagnetic field distribution, break the phase matching condition between the MSL mode and the CPW mode, thereby suppressing mode coupling and moving the cutoff frequency of mode coupling out of the working frequency band of the device. After the air cavity is introduced, the energy is effectively limited between the top signal electrode 122 and the top ground electrode 121 of the modulator chip 12, significantly suppressing the problem of high-frequency loss caused by energy leakage to the substrate when there is no air cavity.

[0037] Furthermore, the interior of the air cavity structure 111 can maintain an air environment or be filled with low-dielectric-constant materials, including but not limited to low-dielectric-constant materials such as benzocyclobutene (BCB), polytetrafluoroethylene (PTFE), and polyethylene (PE), to change the effective refractive index of the MSL mode, thereby optimizing the device performance.

[0038] In some embodiments, at least one air cavity structure 111 is located below the microwave input port 123 of the modulator chip 12, below the microwave input port 123 and the microwave output port 124, or below the entire section.

[0039] During actual implementation, the air cavity structure 111 can be below the microwave input port 123 of the modulator chip 12, below the microwave input port 123 and the microwave output port of the modulator chip 12, or below the entire section of the modulator chip 12 to suppress parasitic modes excited by structural discontinuity and material discontinuity at the microwave packaging transition.

[0040] In some embodiments, the depth of at least one air cavity structure 111 is determined according to the dielectric constant of the modulator chip substrate and the operating frequency of the device.

[0041] During actual implementation, the depth of the air cavity structure 111 is designed based on the dielectric constant of the substrate of the modulator chip 12 and the operating frequency of the device. Typically, the depth of the air cavity structure 111 can be selected as 500 μm to cover a frequency band above 120 GHz, or any depth greater than 50 μm to comprehensively meet the feasibility of the cutting process and the requirements of the device operating frequency, ensure the electrical characteristics (effective refractive index, characteristic impedance) of the MSL mode, better suppress mode coupling, and shift the cut-off frequency of mode coupling out of the operating frequency band of the device. Those skilled in the art can select according to the actual situation and no specific limitation is made here.

[0042] Furthermore, the width of the air cavity structure 111 can be slightly smaller than the width of the modulator chip 12 to provide mechanical support for the device, or can be larger than the width of the modulator chip 12 to reduce the requirements for the cutting process. Those skilled in the art can select according to the actual situation and no specific limitation is made here.

[0043] Figure 2 FIG. 20 is a schematic structural diagram of a microwave resonance suppression device of a second broadband electro-optic modulator packaging structure provided by an embodiment of the present invention.

[0044] As Figure 2 shown, the microwave resonance suppression device 10 of the broadband electro-optic modulator packaging structure includes: at least one air cavity structure 111 and at least one shorting bond wire 13.

[0045] Among them, at least one air cavity structure 111 is placed inside the metal package 11 of the target broadband electro-optic modulator package structure and below the modulator chip 12 of the target broadband electro-optic modulator package structure, so as to shift the cut-off frequency of the mode coupling of the target broadband electro-optic modulator package structure out of the working frequency band of the corresponding device. At least one shorting bond wire 13 is arranged periodically along the microwave transmission direction of the modulator chip 12 and is connected to two top ground electrodes 121 of the modulator chip 12, or connected to one top ground electrode 121 of the modulator chip 12 and the metal package 11, or connected to two top ground electrodes 121 of the modulator chip 12 and one top ground electrode 121 and the metal package 11 simultaneously, so as to increase the grounding continuity between the modulator chip 12 and the metal package 11.

[0046] During the actual implementation process, below the modulator chip 12 of the target broadband electro-optic modulator package structure, local microfabrication can be carried out inside the metal package 11 of the target broadband electro-optic modulator package structure through a high-precision metal milling process to obtain the air cavity structure 111, and the shorting bond wire 13 is used to connect the two top ground electrodes 121 of the modulator chip 12 ( Figure 2 a), or connect the top ground electrode 121 of the modulator chip 12 to the metal package 11 ( Figure 2 b), or connect all three simultaneously ( Figure 2 c), so that the shorting bond wire 13 works in cooperation with the air cavity structure 111. The effective refractive index of the MSL mode is regulated by the air cavity structure 111, the electromagnetic field distribution is optimized, the phase matching condition between the MSL mode and the CPW mode is broken, thereby suppressing mode coupling, and the cut-off frequency of mode coupling is shifted out of the working frequency band of the device. And after the air cavity is introduced, the energy is effectively confined between the top signal electrode 122 and the top ground electrode 121 of the modulator chip 12, significantly suppressing the problem of high-frequency loss caused by energy leakage to the substrate when there is no air cavity. In addition, the shorting bond wire 13 is strategically introduced along the edge of the top ground electrode 121 of the modulator chip 12 to enhance the grounding continuity between the modulator chip 12 and the metal package 11, avoiding the excitation of the PPL mode between the modulator chip 12 and the metal package 11, thereby enhancing the resonance suppression effect in the ultra-wide frequency band.

[0047] Furthermore, the inside of the air cavity structure 111 can maintain an air environment or can be filled with low-dielectric-constant materials, including but not limited to low-dielectric-constant materials such as benzocyclobutene (BCB), polytetrafluoroethylene (PTFE), polyethylene (PE), etc., so as to change the effective refractive index of the MSL mode, thereby optimizing the device performance.

[0048] Further, the number of short - circuit bonding wires 13 is related to the size of the modulator chip 12 in the microwave transmission direction (i.e., the modulator length). On the premise of ensuring the integrity of the modulator chip 12, the more the number of short - circuit bonding wires 13, the better the resonance suppression effect.

[0049] Further, the short - circuit bonding wires 13 can be made of gold wires, silver wires or copper wires with a diameter of 25μm, or gold strips, silver strips or copper strips with a size of 150μm×15μm. Among them, the larger the cross - sectional area, the better the resonance suppression effect.

[0050] It should be noted that when the short - circuit bonding wire 13 connects the top ground electrode 121 of the modulator chip 12 to the metal package 11, the top ground electrode 121 can be on the same height plane as the metal package 11 or on different height planes. Those skilled in the art can choose according to the actual situation and no specific limitation is made here.

[0051] In some embodiments, at least one air - cavity structure 111 is located below the microwave input port 123 of the modulator chip 12, below the microwave input port 123 and the microwave output port 124, or below the entire section of the modulator chip 12.

[0052] During the actual implementation process, the air - cavity structure 111 can be located below the microwave input port 123 of the modulator chip 12, below the microwave input port 123 and the microwave output port 124 of the modulator chip 12, or below the entire section of the modulator chip 12 to suppress the parasitic modes excited by the structural discontinuity and material discontinuity at the microwave packaging transition.

[0053] In some embodiments, the depth of at least one air - cavity structure 111 is determined according to the dielectric constant of the modulator chip substrate and the device operating frequency.

[0054] During the actual implementation process, the depth of the air - cavity structure 111 is designed according to the dielectric constant of the modulator chip 12 substrate and the device operating frequency. Typically, the depth of the air - cavity structure 111 can be selected as 500μm to cover the frequency band above 120GHz, or any depth greater than 50μm to comprehensively meet the feasibility of the cutting process and the requirements of the device operating frequency, ensure the electrical characteristics (effective refractive index, characteristic impedance) of the MSL mode, better suppress the mode coupling, and move the cut - off frequency of the mode coupling out of the operating frequency band of the device. Those skilled in the art can choose according to the actual situation and no specific limitation is made here.

[0055] Further, the width of the air - cavity structure 111 can be slightly smaller than the width of the modulator chip 12 to provide mechanical support for the device, or can be larger than the width of the modulator chip 12 to reduce the requirements for the cutting process. Those skilled in the art can choose according to the actual situation and no specific limitation is made here.

[0056] Figure 3 Schematic diagram of the microwave resonance suppression device of the third broadband electro-optic modulator packaging structure provided by the embodiments of the present invention.

[0057] As Figure 3 shown, the microwave resonance suppression device 10 of the broadband electro-optic modulator packaging structure includes: at least one air cavity structure 111 and at least two thin film resistor circuit substrates 14.

[0058] Among them, at least one air cavity structure 111 is placed inside the metal package 11 of the target broadband electro-optic modulator packaging structure and is located below the modulator chip 12 of the target broadband electro-optic modulator packaging structure to shift the cut-off frequency of the mode coupling of the target broadband electro-optic modulator packaging structure out of the working frequency band of the corresponding device. At least two thin film resistor circuit substrates 14 are arranged along the microwave transmission direction of the modulator chip 12, placed on the same side or both sides of the modulator chip 12, and welded to the surface of the metal package 11 to dissipate the stray electromagnetic energy in the higher-order parasitic modes of the target broadband electro-optic modulator packaging structure.

[0059] During the actual implementation process, below the modulator chip 12 of the target broadband electro-optic modulator packaging structure, local microfabrication can be performed inside the metal package 11 of the target broadband electro-optic modulator packaging structure through a high-precision metal milling process to obtain the air cavity structure 111. And at least two thin film resistor circuit substrates 14 are welded above the metal package 11 through conductive silver glue or solder, and the top ground electrode 121 of the modulator chip 12 is connected to the metal pad 1421 of the thin film resistor circuit substrate 14 through gold wire, gold strip or conductive silver glue, so that the thin film resistor circuit substrate 14 and the air cavity structure 111 work together. The effective refractive index of the MSL mode is regulated by the air cavity structure 111, the electromagnetic field distribution is optimized, the phase matching condition between the MSL mode and the CPW mode is broken, thereby suppressing mode coupling, and shifting the cut-off frequency of mode coupling out of the working frequency band of the device. And after introducing the air cavity, the energy is effectively limited between the top signal electrode 122 and the top ground electrode 121 of the modulator chip 12, significantly suppressing the problem of high-frequency loss caused by energy leakage to the substrate when there is no air cavity. In addition, at least two thin film resistor circuit substrates 14 are strategically loaded along the edge of the ground electrode 121 of the modulator chip 12, and the stray electromagnetic energy of the higher-order parasitic mode is suppressed by the energy dissipation mechanism of the thin film resistor 143, avoiding the coupling between the higher-order mode and the CPW mode, and improving the microwave resonance suppression ability and packaging electromagnetic stability.

[0060] Furthermore, the interior of the air cavity structure 111 can maintain an air environment or be filled with low dielectric constant materials, including but not limited to low dielectric constant materials such as benzocyclobutene (BCB), polytetrafluoroethylene (PTFE), and polyethylene (PE), to change the effective refractive index of the MSL mode, thereby optimizing device performance.

[0061] In some embodiments, at least one air cavity structure 111 is located below the microwave input port 123 of the modulator chip 12, below the microwave input port 123 and the microwave output port 124, or below the entire section.

[0062] During actual implementation, the air cavity structure 111 can be below the microwave input port 123 of the modulator chip 12, below the microwave input port 123 and the microwave output port 124 of the modulator chip 12, or below the entire section of the modulator chip 12 to suppress parasitic modes excited by structural discontinuity and material discontinuity at the microwave package transition.

[0063] In some embodiments, the depth of at least one air cavity structure 111 is determined according to the substrate dielectric constant of the modulator chip 12 and the device operating frequency.

[0064] During actual implementation, the depth of the air cavity structure 111 is designed based on the substrate dielectric constant of the modulator chip 12 and the device operating frequency. Typically, the depth of the air cavity structure 111 can be selected as 500 μm to cover a frequency band above 120 GHz, or any depth greater than 50 μm, to comprehensively meet the feasibility of the cutting process and the requirements of the device operating frequency, ensure the electrical characteristics (effective refractive index, characteristic impedance) of the MSL mode, better suppress mode coupling, and move the cut-off frequency of mode coupling out of the operating frequency band of the device. Those skilled in the art can make their own choices according to the actual situation and are not specifically limited herein.

[0065] Furthermore, the width of the air cavity structure 111 can be slightly smaller than the width of the modulator chip 12 to provide mechanical support for the device, or can be larger than the width of the modulator chip 12 to reduce the requirements for the cutting process. Those skilled in the art can make their own choices according to the actual situation and are not specifically limited herein.

[0066] In some embodiments, the number of thin film resistor circuit substrates 14 is designed symmetrically or asymmetrically according to the size of the modulator chip 12 and the surface current difference of the top ground electrode 121 of the modulator chip 12.

[0067] During actual implementation, the thin-film resistor circuit substrates 14 can be symmetrically placed on both sides of the modulator chip 12. The number of thin-film resistor circuit substrates 14 on both sides can be the same or different. The thin-film resistor circuit substrates 14 can also be asymmetrically placed on the same side or both sides of the modulator chip 12. The number of thin-film resistor circuit substrates 14 on both sides can be the same or different. Those skilled in the art can select according to the size of the modulator chip 12 and the surface current difference of the top ground electrode 121 of the modulator chip 12 under actual circumstances, and no specific limitation is made here.

[0068] In some embodiments, each thin-film resistor circuit substrate 14 includes a ground metal plate, a dielectric substrate 141, a surface metal layer, and a thin-film resistor 143. Among them, the thin-film resistor circuit substrate 14 is connected to the metal package 11 through the ground metal plate. The surface metal layer includes a metal pad 1421 and a ground metal layer 1422. One end of the metal pad 1421 is connected to the ground metal layer 1422 through the thin-film resistor 143, and the other end of the metal pad 1421 is connected to a top ground electrode 121 of the modulator chip 12.

[0069] During actual implementation, as Figure 4 shown, the thin-film resistor circuit substrate 14 sequentially includes from bottom to top: a ground metal plate, a dielectric substrate 141, a surface metal layer, and a thin-film resistor 143. Among them, the thin-film resistor circuit substrate 14 is connected to the metal package 11 through the ground metal plate. The surface metal layer includes a metal pad 1421 and a ground metal layer 1422. The thin-film resistor 143 connects the metal pad 1421 and the ground metal layer 1422, and the other end of the metal pad 1421 is connected to a top ground electrode 121 of the modulator chip 12. Among them, the material of the dielectric substrate 141 includes but is not limited to alumina ceramic substrate, aluminum nitride substrate, diamond substrate, quartz substrate, etc. The typical thickness is 127μm or 254μm, but is not limited to these two thicknesses. Those skilled in the art can select according to the actual situation. The material of the thin-film resistor 143 includes but is not limited to materials such as nickel-chromium alloy (NiCr), titanium nitride (TiN), tantalum nitride (TaN), etc. The resistance value of the thin-film resistor 143 is symmetrically or asymmetrically designed according to the size of the modulator chip 12 and the surface current distribution of the top ground electrode 121 of the modulator chip 12.

[0070] Furthermore, the thin-film resistor circuit substrate 14 may further include: at least one metal via 144. At least one metal via 144 penetrates through the dielectric substrate 141 and forms a complete loop with the ground metal layer 1422. Among them, the diameter of the metal via 144 is related to the thickness of the dielectric substrate 141. The typical diameter is not less than four-fifths of the thickness of the dielectric substrate 141. With the improvement of process technology, the diameter can be further reduced.

[0071] Figure 5Schematic diagram of the microwave resonance suppression device of the fourth broadband electro-optic modulator packaging structure provided by the embodiments of the present invention.

[0072] As Figure 5 shown, the microwave resonance suppression device 10 of the broadband electro-optic modulator packaging structure includes: at least one air cavity structure 111, at least one shorting bond wire 13, and at least two thin film resistor circuit substrates 14.

[0073] Among them, at least one air cavity structure 111 is placed inside the metal package 11 of the target broadband electro-optic modulator packaging structure and below the modulator chip 12 of the target broadband electro-optic modulator packaging structure, so as to shift the cut-off frequency of the mode coupling of the target broadband electro-optic modulator packaging structure out of the working frequency band of the corresponding device. At least two thin film resistor circuit substrates 14 are arranged along the microwave transmission direction of the modulator chip 12, placed on the same side or both sides of the modulator chip 12, and welded to the surface of the metal package 11 to dissipate the stray electromagnetic energy in the higher-order parasitic modes of the target broadband electro-optic modulator packaging structure. At least one shorting bond wire 13 is periodically arranged along the microwave transmission direction of the modulator chip 12, and is connected to the two top ground electrodes 121 of the modulator chip 12, or connected to one top ground electrode 121 of the modulator chip and the metal package 11, or connected to the two top ground electrodes 121 of the modulator chip, one top ground electrode 121 and the metal package 11 simultaneously, so as to increase the grounding continuity between the modulator chip 12 and the metal package 11.

[0074] During the actual implementation process, below the modulator chip 12 of the target broadband electro-optic modulator packaging structure, local microfabrication can be performed inside the metal package 11 of the target broadband electro-optic modulator packaging structure through a high-precision metal milling process to obtain the air cavity structure 111. And use the shorting bond wire 13 to connect the two top ground electrodes 121 of the modulator chip 12 ( Figure 2 a), or connect the top ground electrode 121 of the modulator chip 12 to the metal package 11 ( Figure 2 b), or connect all three simultaneously ( Figure 2 c), so that the shorting bond wire 13 and the air cavity structure 111 work together. Also, at least two thin film resistor circuit substrates 14 are welded above the metal package 11 through conductive silver paste or solder, and the top ground electrode 121 of the modulator chip 12 is connected to the metal pad 1421 of the thin film resistor circuit substrate 14 through a gold wire, a gold strip or conductive silver paste, so that the thin film resistor circuit substrate 14 and the air cavity structure 111 work together.

[0075] In the embodiments of the present invention, an air cavity structure 111 is used to regulate the effective refractive index of the MSL mode, optimize the electromagnetic field distribution, break the phase matching condition between the MSL mode and the CPW mode, and suppress the excitation of high-frequency parasitic modes and their coupling with the main mode at the source. After introducing the air cavity, the energy is effectively confined between the top signal electrode 122 and the top ground electrode 121 of the modulator chip 12, significantly suppressing the problem of high-frequency loss caused by energy leakage to the substrate when there is no air cavity. In addition, shorting bond wires 13 are strategically introduced along the edge of the top ground electrode 121 of the modulator chip 12 to enhance the grounding continuity between the modulator chip 12 and the metal package 11, effectively suppressing the excitation of the PPL mode, thereby achieving stronger resonance suppression ability in a wider frequency band range; at least two thin film resistor circuit boards 14 are strategically loaded along the edge of the ground electrode 121 of the modulator chip 12, and the energy dissipation mechanism of the thin film resistor 143 is used to absorb the stray electromagnetic energy carried by the residual parasitic modes, taking into account the microwave performance and the flexibility and stability of the package structure. The synergistic effect of the three mechanisms helps to achieve a coverage suppression of different frequency bands and different forms of parasitic modes.

[0076] Further, the interior of the air cavity structure 111 can maintain an air environment or be filled with a low dielectric constant material, including but not limited to low dielectric constant materials such as benzocyclobutene (BCB), polytetrafluoroethylene (PTFE), polyethylene (PE), etc., to change the effective refractive index of the MSL mode, thereby optimizing the device performance.

[0077] Further, the number of shorting bond wires 13 is related to the size of the modulator chip 12 in the microwave transmission direction (i.e., the modulator length). On the premise of ensuring the integrity of the modulator chip 12, the more the number of shorting bond wires 13, the better the resonance suppression effect.

[0078] Further, the shorting bond wires 13 can be selected from gold wires, silver wires or copper wires with a diameter of 25 μm, or gold strips, silver strips or copper strips with a size of 150 μm × 15 μm. Among them, the larger the cross-sectional area, the better the resonance suppression effect.

[0079] It should be noted that when the shorting bond wires 13 connect the top ground electrode 121 of the modulator chip 12 and the metal package 11, the top ground electrode 121 can be on the same height plane as the metal package 11 or on different height planes. Those skilled in the art can choose according to the actual situation and are not specifically limited here.

[0080] In some embodiments, at least one air cavity structure 111 is located below the microwave input port 123 of the modulator chip 12, below the microwave input port 123 and the microwave output port 124, or below the entire section.

[0081] During actual implementation, the air cavity structure 111 can be located below the microwave input port 123 of the modulator chip 12, below the microwave input port 123 and the microwave output port 124 of the modulator chip 12, or below the entire section of the modulator chip 12 to suppress parasitic modes excited due to structural discontinuity and material discontinuity at the microwave packaging transition.

[0082] In some embodiments, the depth of at least one air cavity structure 111 is determined according to the substrate dielectric constant of the modulator chip 12 and the device operating frequency.

[0083] During actual implementation, the depth of the air cavity structure 111 is designed based on the substrate dielectric constant of the modulator chip 12 and the device operating frequency. Typically, the depth of the air cavity structure 111 can be selected as 500 μm to cover a frequency band above 120 GHz, or any depth greater than 50 μm can also be selected to comprehensively meet the feasibility of the cutting process and the requirements of the device operating frequency, ensure the electrical characteristics (effective refractive index, characteristic impedance) of the MSL mode, better suppress mode coupling, and shift the cut-off frequency of mode coupling out of the operating frequency band of the device. Those skilled in the art can make their own selection according to the actual situation and no specific limitation is made here.

[0084] Furthermore, the width of the air cavity structure 111 can be slightly smaller than the width of the modulator chip 12 to provide mechanical support for the device, or it can be larger than the width of the modulator chip 12 to reduce the requirements for the cutting process. Those skilled in the art can make their own selection according to the actual situation and no specific limitation is made here.

[0085] In some embodiments, the number of thin-film resistor circuit substrates 14 is designed symmetrically or asymmetrically according to the size of the modulator chip 12 and the surface current difference of the top ground electrode 121 of the modulator chip 12.

[0086] During actual implementation, the thin-film resistor circuit substrates 14 can be symmetrically placed on both sides of the modulator chip 12, and the number of thin-film resistor circuit substrates 14 on both sides can be the same or different; the thin-film resistor circuit substrates 14 can also be asymmetrically placed on the same side or both sides of the modulator chip 12, and the number of thin-film resistor circuit substrates 14 on both sides can be the same or different. Those skilled in the art can make their own selection according to the size of the modulator chip 12 and the surface current difference of the top ground electrode 121 of the modulator chip 12 under the actual situation and no specific limitation is made here.

[0087] In some embodiments, each thin-film resistor circuit substrate 14 includes a ground metal plate, a dielectric substrate 141, a surface metal layer, and a thin-film resistor 143. The thin-film resistor circuit substrate 14 is connected to the metal package 11 through the ground metal plate. The surface metal layer includes a metal pad 1421 and a ground metal layer 1422. One end of the metal pad 1421 is connected to the ground metal layer 1422 through the thin-film resistor 143, and the other end of the metal pad 1421 is connected to a top ground electrode 121 of the modulator chip 12.

[0088] During the actual implementation process, as Figure 4 shown, the thin-film resistor circuit substrate 14 sequentially includes from bottom to top: a ground metal plate, a dielectric substrate 141, a surface metal layer, and a thin-film resistor 143. The thin-film resistor circuit substrate 14 is connected to the metal package 11 through the ground metal plate. The surface metal layer includes a metal pad 1421 and a ground metal layer 1422. The thin-film resistor 143 connects the metal pad 1421 and the ground metal layer 1422, and the other end of the metal pad 1421 is connected to a top ground electrode 121 of the modulator chip 12. Among them, the material of the dielectric substrate 141 includes but is not limited to alumina ceramic substrates, aluminum nitride substrates, diamond substrates, quartz substrates, etc. The typical thickness is 127μm or 254μm, but is not limited to these two thicknesses. Those skilled in the art can select according to the actual situation; the material of the thin-film resistor 143 includes but is not limited to materials such as nickel-chromium alloy (NiCr), titanium nitride (TiN), tantalum nitride (TaN), etc. The resistance value of the thin-film resistor 143 is symmetrically or asymmetrically designed according to the size of the modulator chip 12 and the surface current distribution of the top ground electrode 121 of the modulator chip 12.

[0089] Furthermore, the thin-film resistor circuit substrate 14 may further include: at least one metal via 144. At least one metal via 144 penetrates through the dielectric substrate 141 and forms a complete loop with the ground metal layer 1422. Among them, the diameter of the metal via 144 is related to the thickness of the dielectric substrate 141. The typical diameter is not less than four-fifths of the thickness of the dielectric substrate 141. With the improvement of process technology, the diameter can be further reduced.

[0090] In summary, the microwave resonance suppression device of the broadband electro-optic modulator packaging structure proposed according to the embodiments of the present invention has the following beneficial effects:

[0091] (1) Wide bandwidth coverage: It can support efficient resonance suppression in the frequency range from DC to hundreds of GHz, significantly improving the high-frequency stability and frequency response consistency of the device;

[0092] (2) Compact structure and process-friendly: Only local microstructure modification of the metal shell is required, avoiding the limitations of existing microwave absorbing materials in terms of temperature, frequency, and space, reducing the complexity of the packaging process, and meeting the requirements of miniaturization and high-density modular packaging;

[0093] (3) Flexible design and high degree of freedom: The three mechanisms of mode coupling suppressor, short-circuit line bonding, and thin-film resistor loading can be used independently or combined as needed, with high configurability, and are suitable for various electrode structures (such as CPW, CSL, and their microstructure variants) and different chip packaging layouts;

[0094] (4) Cost controllable: The materials and processing methods used are all based on mature process paths, without the need for high-cost new materials or complex manufacturing steps, which helps to control the overall module manufacturing cost and is suitable for large-scale industrial applications;

[0095] (5) Good versatility and scalability, and strong packaging compatibility: Suitable for the packaging of various types of electro-optic modulators and related devices, specifically including: not only suitable for modulators using CPW electrodes or CSL electrode structures, but also suitable for CPW / CSL structures of modulators with periodically microstructured metal electrodes, such as periodic capacitive load traveling wave electrodes (CL-TWEs). Among them, the microstructured metal electrodes include, but are not limited to, T-shaped microstructured metal electrodes, L-shaped microstructured metal electrodes, zigzag microstructured metal electrodes, grid-shaped microstructured metal electrodes, and fan-shaped microstructured metal electrodes, etc.; it is also compatible with various new coplanar structure devices developed based on CPW electrodes and CSL electrodes; suitable for the packaging of electro-optic modulators based on various material platforms, including but not limited to silicon-based modulators, (thin-film) lithium niobate modulators, InP-based modulators, and polymer modulators, and can also be extended to the packaging structure design of coplanar waveguide or coplanar slotline devices in other high-frequency microwave photonic devices or radio frequency circuits, with good platform migration ability;

[0096] (6) Breaking through the bottlenecks of parasitic mode coupling and microwave resonance caused by the metal cavity in the existing electro-optic modulator packaging structure, significantly improving the high-frequency microwave transmission performance and electro-optic frequency response of the modulator packaging module, with good engineering practical value and promotion prospects.

[0097] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0098] In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "N" is at least two, such as two, three, etc., unless otherwise specifically defined.

Claims

1. A microwave resonance suppression device for a broadband electro-optic modulator packaging structure, characterized in that, Including: At least one air cavity structure, which is placed inside the metal package of the target broadband electro-optic modulator package structure and is located below the modulator chip of the target broadband electro-optic modulator package structure, so as to move the cut-off frequency of the mode coupling of the target broadband electro-optic modulator package structure out of the working frequency band of the corresponding device.

2. The microwave resonance suppression device of the broadband electro-optic modulator packaging structure according to claim 1, characterized in that, The at least one air cavity structure is located below the microwave input port of the modulator chip, below the microwave input port and the microwave output port, or below the entire section.

3. The microwave resonance suppression device of the broadband electro-optic modulator packaging structure according to claim 1, characterized in that, The depth of the at least one air cavity structure is determined according to the dielectric constant of the modulator chip substrate and the device operating frequency.

4. A microwave resonance suppression device for a broadband electro-optic modulator packaging structure, characterized in that, The microwave resonance suppression device according to any one of claims 1-3, including: At least one short-circuit bonding wire, which is periodically arranged along the microwave transmission direction of the modulator chip and is connected to two top ground electrodes of the modulator chip, or is connected to one top ground electrode of the modulator chip and the metal package, or is connected to two top ground electrodes of the modulator chip, one top ground electrode and the metal package simultaneously, so as to increase the grounding continuity between the modulator chip and the metal package.

5. A microwave resonance suppression device for a broadband electro-optic modulator packaging structure, characterized in that The microwave resonance suppression device according to any one of claims 1-3, including: At least two thin-film resistor circuit substrates, which are arranged along the microwave transmission direction of the modulator chip, are placed on the same side or both sides of the modulator chip, and are welded to the surface of the metal package, so as to dissipate the stray electromagnetic energy in the high-order parasitic mode of the target broadband electro-optic modulator package structure.

6. The microwave resonance suppression device of the broadband electro-optic modulator packaging structure according to claim 5, characterized in that, Each thin-film resistor circuit substrate includes a grounding metal plate, a dielectric substrate, a surface metal layer and a thin-film resistor. Among them, the thin-film resistor circuit substrate is connected to the metal package through the grounding metal plate. The surface metal layer includes a metal pad and a grounding metal layer. One end of the metal pad is connected to the grounding metal layer through the thin-film resistor, and the other end of the metal pad is connected to one top ground electrode of the modulator chip.

7. The microwave resonance suppression device of the broadband electro-optic modulator packaging structure according to claim 6, characterized in that, Further including: At least one metal through-hole, which penetrates through the dielectric substrate and forms a complete loop with the grounding metal layer.

8. A microwave resonance suppression device for a broadband electro-optic modulator packaging structure, characterized in that, The microwave resonance suppression device according to any one of claims 1-3, including: At least two thin-film resistor circuit substrates, which are arranged along the microwave transmission direction of the modulator chip, are placed on the same side or both sides of the modulator chip, and are welded to the surface of the metal package, so as to dissipate the stray electromagnetic energy in the high-order parasitic mode of the target broadband electro-optic modulator package structure; At least one short-circuit bonding wire, wherein the at least one short-circuit bonding wire is arranged periodically along the microwave transmission direction of the modulator chip, and is connected to two top ground electrodes of the modulator chip, or is connected to one top ground electrode of the modulator chip and the metal package, or is connected to two top ground electrodes of the modulator chip, or is connected to one top ground electrode and the metal package simultaneously, or is connected to two top ground electrodes of the modulator chip, or is connected to one top ground electrode, the metal package and a thin-film resistor circuit substrate simultaneously, so as to increase the grounding continuity between the modulator chip and the metal package.

9. The microwave resonance suppression device of the broadband electro-optic modulator packaging structure according to claim 8, characterized in that, The thin-film resistor circuit substrate includes a ground metal plate, a dielectric substrate, a surface metal layer and a thin-film resistor, wherein the thin-film resistor circuit substrate is connected to the metal package through the ground metal plate, the surface metal layer includes a metal pad and a ground metal layer, one end of the metal pad is connected to the ground metal layer through the thin-film resistor, and the other end of the metal pad is connected to one top ground electrode of the modulator chip.

10. The microwave resonance suppression device of the broadband electro-optic modulator packaging structure according to claim 9, characterized in that, Further comprising: At least one metal via hole, wherein the at least one metal via hole penetrates through the dielectric substrate and forms a complete loop with the ground metal layer.

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