A high-speed modulator packaging structure and a packaging method

Abstract

The present invention discloses a high-speed modulator packaging structure and a packaging method. The packaging structure includes a semi-airtight package housing. One end of the package housing extends upward to form a chamber, and an airtight space is formed above the chamber. The inner bottom surface of the airtight space is provided with a first ceramic substrate. The other end of the package housing is provided with a second ceramic substrate. A plurality of laser carriers are longitudinally arranged on the surface of the first ceramic substrate, and a modulator chip and a lens are mounted on the surface of the second ceramic substrate. A plurality of first collimating lenses are arranged on the first ceramic substrate, and the laser carriers correspond to the first collimating lenses one by one. A first through hole is formed on one side of the package wall of the chamber, and an optical window bracket is installed. An adapter is connected to the outside of the first optical window bracket. A light passing hole is provided on the other side of the package wall, and the lens on the second ceramic substrate corresponds to the light passing hole. The inner side of the first optical window bracket and the inner side of the light passing hole are encapsulated with a light transmissive device. This solution can reduce the transmission loss of radio frequency signals and improve the signal transmission quality and transmission rate of the optical module.

Description

Technical Field

[0001] The present invention relates to the field of optical communication, and particularly to a high-speed modulator packaging structure and a packaging method thereof. Background Art

[0002] In recent years, thanks to the key development of emerging industries such as artificial intelligence, telemedicine, and industrial Internet in China, the cloud computing and data center industries have been continuously developing. At the same time, the construction of 5G networks has been vigorously promoted, which has generated a great demand for high-speed transmission optical modules, including 200G, 400G, and the in-research 800G and 1.6T optical modules.

[0003] At present, there are three solutions for the transmitter of optical modules with a transmission rate below 400G: the EML (Electro-Absorption Laser) solution, the SOI modulator chip (Silicon on Insulator modulator chip) solution, and the LNOI (Lithium niobate on insulator) solution. For non-hermetic optical modules, the modulation signal can be transmitted from the PCBA (Printed Circuit Board Assembly) to the EML chip or the modulator chip through wire bonding. For hermetic modules, the modulator signal needs to be transmitted from the PCBA to the ceramic substrate and then to the EML chip or the modulator chip. The PCBA is connected to the ceramic substrate, and the ceramic substrate is connected to the EML chip (or the modulator chip) through wire bonding.

[0004] As Figures 15-17 shown, in the existing solution, the radio frequency interface on the modulator chip, that is, the metal pattern on the right side of the chip, is connected to one side of the ceramic 17 through wire bonding, and the other side of the ceramic 17 is connected to the PCBA16. The connection method can be wire bonding / flexible board soldering. It can be seen that two connections are required between the modulator chip and the PCBA16.

[0005] Compared with the transmission on the PCBA and the ceramic substrate, the radio frequency signal will have a large loss when transmitted through the wire, resulting in signal distortion. Therefore, in order to enable the optical module to support a higher transmission rate, it is necessary to minimize the number of times the radio frequency signal is transmitted through wire bonding. Summary of the Invention

[0006] Object of the Invention: The object of the present invention is to provide a high-speed modulator packaging structure and a packaging method thereof that can reduce the transmission loss of radio frequency signals and improve the signal transmission quality and transmission rate of optical modules.

[0007] Technical solution: The high-speed modulator packaging structure of the present invention includes a semi-airtight shell housing. One end of the shell housing extends upward to form a chamber. A shell cover plate is arranged above the chamber to form an airtight space. The inner bottom surface of the airtight space is provided with a first ceramic substrate. The other end surface of the shell housing is provided with a second ceramic substrate. A plurality of laser carriers are longitudinally arranged on the surface of the first ceramic substrate. A modulator chip is installed close to the end surface on the surface of the second ceramic substrate. One end of the second ceramic substrate close to the first ceramic substrate is a reserved space for installing a lens. A plurality of first collimating lenses are arranged on the first ceramic substrate on the side of the laser carrier close to the modulator chip, and the laser carriers correspond to the first collimating lenses one by one. A first through hole is opened on one side of the shell wall of the chamber for installing an optical window bracket, and an adapter is connected to the outside of the first optical window bracket. A light passing hole is arranged on the other side of the shell wall, and the lens on the second ceramic substrate corresponds to the light passing hole. The inner sides of the first optical window bracket and the light passing hole are both encapsulated with a light transmitting device.

[0008] The light transmitting device uses sapphire. Sapphire is built into the first optical window bracket, and a clamping groove is arranged inside the light passing hole. The sapphire is placed in the clamping groove, which can support the signal light to pass through while ensuring the airtightness of the shell.

[0009] The light outlet of the laser carrier, the light inlet of the modulator chip, the optical axis of the collimating lens, and the optical axis of the lens on the second ceramic substrate are at the same height, which is beneficial to reducing the coupling process difficulty and improving the coupling efficiency.

[0010] A second through hole is opened on the front surface of the shell wall for installing a ceramic plate. Metal patterns are arranged on the surface and side surfaces of the ceramic plate. The metal patterns are connected to a plurality of laser carriers inside the airtight space of the shell housing, playing an electrical conduction role.

[0011] An isolator is arranged on the surface of the first ceramic substrate outside the collimating lens, and the isolator corresponds to the first collimating lens, which can prevent stray light from affecting the operation of the laser.

[0012] The present invention also includes a high-speed modulator packaging method, which includes the following steps:

[0013] S1: Fix a plurality of laser chips on a plurality of third ceramic substrates by eutectic to form a plurality of laser carriers; fix the plurality of laser carriers on the surface of the first ceramic substrate by silver glue patch and arrange them longitudinally; arrange a plurality of collimating lenses on the first ceramic substrate on the side of the laser carrier close to the modulator chip, and make the laser carriers correspond to the collimating lenses one by one;

[0014] S2: Fix the second ceramic substrate on the surface of the package housing by silver paste patching. Then, fix the modulator chip on the surface of the second ceramic substrate by silver paste patching. The modulator chip is mounted closely against the end face of the second ceramic substrate. A second collimating lens, or multiple focusing lenses and a second collimating lens, are mounted on the reserved end face.

[0015] S3: Power on the first-channel laser for coupling. Among them, the laser chip is coupled to the modulator chip by a single-lens or double-lens method.

[0016] S4: Power on any one channel or multiple channels of lasers, and adjust the lens position and adapter position on the second ceramic substrate to perform the coupling from the modulator chip to the fiber ferrule in the adapter.

[0017] S5: Seal the chamber of the package housing with the package cover plate.

[0018] In step S2, during the mounting process of the modulator chip, the following requirements need to be met: The light output port of the laser carrier in the Z direction is aligned with the light input port of the modulator chip. The distance from the laser carrier to the modulator chip in the Y direction is obtained by simulation software. The light output port of the laser carrier in the X direction is at the same height as the light input port of the modulator chip, so as to improve the coupling efficiency.

[0019] The working principle of the present invention is as follows: Multiple-channel lasers emit light simultaneously. The light is coupled into the modulator chip through a single / double-lens scheme. Through the MUX (multiplexing) function of the modulator chip, multiple-channel optical signals are combined into one channel, and then emitted by the modulator chip and coupled to the fiber ferrule of the adapter through the collimating lens on the second ceramic substrate.

[0020] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) A semi-hermetic package is adopted. The modulator chip is placed in the non-hermetic part of the package. The RF interface on the chip is directly connected to the external structure PCBA through gold wire bonding. Compared with the structure of the traditional hermetic package where the RF interface is first connected to the package ceramic part and then to the PCBA RF interface, it can greatly reduce the high-frequency signal loss and improve the transmission rate. (2) The laser carrier is placed inside the hermetic part of the package. This device combines the advantages of high transmission rate of traditional non-hermetic devices and high reliability of hermetic devices. In addition, through hybrid integration and the MUX function of the modulator chip, the device integration degree is improved. Description of the Drawings

[0021] Figure 1 It is a structural schematic diagram of the present invention;

[0022] Figure 2 It is a structural schematic diagram in the state without the package cover plate installed;

[0023] Figure 3Schematic diagram of the structure of the package housing

[0024] Figure 4 Front view of the package housing with the optical window bracket installed

[0025] Figure 5 Top view of the package housing with the optical window bracket installed

[0026] Figure 6 Left view of the package housing with the optical window bracket installed

[0027] Figure 7 Top view when the laser carriers are arranged in a 1-channel + 3-channel configuration and a double-lens coupling method is adopted

[0028] Figure 8 Top view when the laser carriers are arranged in a 1-channel + 3-channel configuration and a single-lens coupling method is adopted

[0029] Figure 9 Top view when the laser carriers are arranged in a 2-channel + 2-channel configuration and a double-lens coupling method is adopted

[0030] Figure 10 Top view when the laser carriers are arranged in a 2-channel + 2-channel configuration and a single-lens coupling method is adopted

[0031] Figure 11 Top view when the laser carriers are arranged in a 3-channel + 1-channel configuration and a double-lens coupling method is adopted

[0032] Figure 12 Top view when the laser carriers are arranged in a 3-channel + 1-channel configuration and a single-lens coupling method is adopted

[0033] Figure 13 Schematic diagram of the high-speed modulator packaging structure of the present invention in the operating state

[0034] Figure 14 For Figure 13 Enlarged schematic diagram at position A in

[0035] Figure 15 Schematic diagram of the existing modulator packaging structure in the operating state

[0036] Figure 16 For Figure 15 Enlarged schematic diagram at position B in

[0037] Figure 17 For Figure 15 Enlarged schematic diagram at position C in Detailed implementation manners

[0038] The technical solution of the present invention will be introduced in detail below in combination with specific embodiments and the accompanying drawings of the specification.

[0039] As Figure 1 shown, the high-speed modulator packaging structure of the present invention includes a package housing 5, and the package housing 5 is set to a semi-airtight structure. Specifically, the package housing 5 includes a package wall 51 and a kovar package substrate 52. One end of the package housing 5 extends upward to form a chamber. The periphery of the chamber is the package wall 51. A package cover plate 2 is arranged above the chamber to form an airtight space, and nitrogen is filled in the airtight space. The first ceramic substrate 8 is installed on the bottom surface in the airtight space. The first ceramic substrate 8 is a ceramic substrate without patterns; the other end of the package housing 5 is the kovar package substrate 52, and the second ceramic substrate 6 is installed on the surface of the kovar package substrate 52. The second ceramic substrate 6 is a ceramic substrate without patterns.

[0040] A plurality of laser carriers are longitudinally arranged on the surface of the first ceramic substrate 8. The laser carriers are formed by eutectically fixing laser chips 10 on a third ceramic substrate 9. A gold layer and gold-tin solder are provided on the surface of the third ceramic substrate 9. In this embodiment, the number of laser carriers is 4, so 4 optical channels can be generated. The modulator chip 15 is installed close to the end face on the surface of the second ceramic substrate 6. The modulator chip 15 is a thin-film lithium niobate modulator chip with a built-in single-mode fiber ferrule. One end of the surface of the second ceramic substrate 6 close to the first ceramic substrate 8 is a reserved space, and the type and number of lenses to be installed are determined according to the single-coupling method or the double-coupling method. The lenses here include a focusing lens 13 and a second collimating lens 14; a plurality of first collimating lenses 11 are arranged on the first ceramic substrate 8 on the side of the laser carrier close to the modulator chip 15, and the laser carriers correspond to the first collimating lenses 11 one by one to ensure that the light generated by the laser carriers can pass through the first collimating lenses 11. In order to prevent stray light from affecting the operation of the laser carriers, an isolator 12 is arranged on the surface of the first ceramic substrate 8 outside the first collimating lenses 11, and the isolator 12 corresponds to the first collimating lenses 11. In this embodiment, the light output ports of the laser carriers, the light input ports of the modulator chips 15, the optical axes of the first collimating lenses 11, and the optical axes of the lenses on the second ceramic substrate 6 are all at the same height, which is beneficial to reducing the coupling process difficulty and improving the coupling efficiency.

[0041] A first through-hole is opened on one side of the package wall 51 of the chamber, and an optical window bracket 1 is installed on the first through-hole. An adapter 7 is connected to the outside of the optical window bracket 1; a light-passing hole 3 is provided on the other side of the package wall 51, and the lens on the second ceramic substrate 6 corresponds to the light-passing hole 3 to ensure that the light can pass through the center of the lens on the second ceramic substrate 6 after passing through the light-passing hole 3; both the inside of the first optical window bracket 1 and the inside of the light-passing hole 3 are encapsulated with a light-transmitting device to support the passage of the signal light while ensuring the sealing performance of the airtight space. In this embodiment, the light-passing hole 3 is an elliptical structure arranged horizontally, the light-transmitting device uses sapphire, the first optical window bracket 1 is internally provided with sapphire, and a clamping groove is provided inside the light-passing hole 3, and the sapphire is placed in the clamping groove. The light-transmitting device is not limited to sapphire, as long as it can support the passage of the signal light and ensure airtightness at the same time. A second through-hole is opened on the front surface of the package wall 51 for installing the ceramic plate 4. Metal patterns are provided on the surface and side of the ceramic plate 4, and the metal patterns are connected to the internal parts in the airtight space of the package housing 5. The internal parts refer to the laser carrier. If a TEC is added to the lower end of the laser carrier, the metal pattern also needs to be connected to the TEC. In this case, the internal parts refer to the laser carrier and the TEC.

[0042] The present invention also includes a high-speed modulator packaging method, which specifically includes the following steps:

[0043] S1: Fix a plurality of laser chips 10 on a plurality of third ceramic substrates 9 by eutectic to form a plurality of laser carriers; fix the plurality of laser carriers on the surface of the first ceramic substrate 8 by silver paste patch and arrange them longitudinally; in this embodiment, four laser chips 10 are respectively fixed on four third ceramic substrates 9 to form four laser carriers. The first ceramic substrate 8 is fixed on the bottom surface of the airtight space of the package housing 5 by silver paste patch. A plurality of collimating lenses 11 are arranged on the first ceramic substrate 8 on the side of the laser carrier close to the modulator chip 15, and the laser carriers correspond to the collimating lenses 11 one by one; in this embodiment, the number of collimating lenses 11 is also four, corresponding to the four laser carriers one by one.

[0044] S2: Fix the second ceramic substrate 6 on the surface of the kovar package substrate 52 in the package housing 5 by silver paste patch, and then fix the modulator chip 15 on the surface of the second ceramic substrate 6 by silver paste patch. The modulator chip 15 is mounted closely against the end face of the second ceramic substrate 6, and a second collimating lens 14, or a plurality of focusing lenses 13 and a second collimating lens 14 are reserved for installation on the reserved end face;

[0045] During the mounting process of the modulator chip 15, the following requirements need to be met: such as Figure 7As shown, the light output port of the Z - direction laser carrier is aligned with the light input port of the modulator chip 15. The distance from the Y - direction laser carrier to the modulator chip 15 is obtained by simulation software. The light output port of the X - direction laser carrier is at the same height as the light input port of the modulator chip 15. The heights of the first ceramic substrate 8, the second ceramic substrate 6, and the third ceramic substrate 9 are adjusted according to actual requirements.

[0046] The isolator 12 is mounted on the first ceramic substrate 8 with ultraviolet - curable adhesive. When mounting, it is necessary to ensure that in the Z - direction, the light output of the laser carrier passes through the center of the isolator 12, which can be achieved by pre - adjusting the height of the isolator 12, and the mounting position in the Y - direction is obtained by simulation;

[0047] S3: Power on the lasers in the first channel for coupling. Among them, the laser chip 10 is coupled to the modulator chip 15 by a single - lens or double - lens method. The ultimate goal of both coupling methods is to improve the coupling efficiency of the optical system 1 as much as possible. Different laser chips and modulator chips will use different coupling methods, which are obtained through system simulation and modeling, and the method with the highest coupling efficiency is selected to manufacture the product. For the double - lens coupling scheme (as shown in Figure 7 , 9 , 11), the coupling efficiency is improved by adjusting the positions of the second collimating lens 14 and the focusing lens 13; for single - lens coupling (as shown in Figure 8 , 10 , 12), the coupling efficiency is improved by adjusting the position of the second collimating lens 14. The other three channels are coupled with reference to the method of the first channel. Among the above 6 possible coupling schemes, there are three laser distribution structures, that is, the positions of the three adapters. The final scheme selection depends on the optical module packaging form and the ROSA structure.

[0048] S4: Power on the lasers in any one or more channels, adjust the positions of the lenses on the second ceramic substrate 6 and the positions of the adapters 7, and perform the coupling from the modulator chip 15 to the fiber ferrule in the adapter 7 to improve the coupling efficiency;

[0049] S5: Use the housing cover plate 2 to cover the chamber of the housing body 5.

[0050] In addition, according to the actual product requirements, a TEC (Thermo Electric Cooler, semiconductor cooler) can be added at the lower end of the laser carrier, and a thermistor can be mounted on the first ceramic substrate 8 to monitor the working temperature of the laser chip 10.

[0051] In this solution, four-channel lasers emit light simultaneously. The light passes through a single / double lens and is coupled into the modulator chip 15. Through the MUX (multiplexing) function of the modulator chip, the 4-channel optical signals are combined into 1 channel, which is emitted by the modulator chip 15 and coupled into the fiber ferrule of the adapter 7 through the second collimating lens 14. Among them, to prevent stray light from affecting the operation of the laser carrier, an isolator 12 is provided between the laser carrier and the modulator chip 15.

[0052] As Figure 13 and Figure 14 shown, this solution uses a semi-hermetic TOSA. The RF interface on its modulator chip 15 can be directly connected to the PCBA RF interface through gold wire bonding. The RF interface on the chip, that is, the metal pattern located on the right side of the chip, is connected to the external PCBA16 through gold wire bonding. It can be seen that only one connection is required between the modulator chip 15 and the PCBA16.

[0053] Compared with the traditional hermetic package structure where the RF interface first connects to the package ceramic part and then to the PCBA RF interface, the packaging structure proposed by the present invention can greatly reduce the high-frequency signal loss and improve the transmission rate. The modulation rate of the modulator packaged with the structure of this solution can reach up to 112 Gbaud at most, and it can be compatible with the QSFD-DD (Quad Small Form Factor Pluggable-Double Density) package of the optical module.

Claims

1. A high-speed modulator packaging structure, characterized in that: It includes a semi-hermetic package housing (5), one end of the package housing (5) extends upward to form a chamber, a package cover plate (2) is arranged above the chamber to form a hermetic space, and a first ceramic substrate (8) is installed on the inner bottom surface of the hermetic space; the other end surface of the package housing (5) is installed with a second ceramic substrate (6); A plurality of laser carriers are longitudinally arranged on the surface of the first ceramic substrate (8), a modulator chip (15) is installed close to the end face on the surface of the second ceramic substrate (6), and a reserved space is provided at one end of the second ceramic substrate (6) close to the first ceramic substrate (8) for installing a lens; a plurality of first collimating lenses (11) are arranged on the first ceramic substrate (8) on the side of the laser carrier close to the modulator chip (15), and the laser carriers correspond to the first collimating lenses (11) one by one; A first through hole is opened on one side of the package wall (51) of the chamber for installing a first optical window bracket (1), and an adapter (7) is connected to the outside of the first optical window bracket (1); a light passing hole (3) is arranged on the other side of the package wall (51), and the lens on the second ceramic substrate (6) corresponds to the light passing hole (3); the inner side of the first optical window bracket (1) and the inner side of the light passing hole (3) are both encapsulated with a light transmissive device; The light output port of the laser carrier, the light input port of the modulator chip (15), the optical axis of the first collimating lens (11), and the optical axis of the lens on the second ceramic substrate (6) are at the same height; A second through hole is opened on the front surface of the package wall (51) for installing a ceramic plate (4), and metal patterns are arranged on the surface and side of the ceramic plate (4), and the metal patterns are connected to a plurality of laser carriers inside the hermetic space of the package housing (5); 2. The high-speed modulator packaging structure according to claim 1, wherein: The light transmissive device uses sapphire, the first optical window bracket (1) is internally provided with sapphire, and a card slot is arranged on the inner side of the light passing hole (3), and the sapphire is placed in the card slot; 3. The high-speed modulator packaging structure according to claim 1, wherein: An isolator (12) is arranged on the surface of the first ceramic substrate (8) outside the first collimating lens (11), and the isolator (12) corresponds to the first collimating lens (11); 4. A high-speed modulator packaging method, characterized in that, The method is applied to the high-speed modulator packaging structure described in claim 1, and includes the following steps: S1: Fix a plurality of laser chips (10) on a plurality of third ceramic substrates (9) by eutectic to form a plurality of laser carriers; fix the plurality of laser carriers on the surface of the first ceramic substrate (8) by silver glue patch and arrange them longitudinally; arrange a plurality of first collimating lenses (11) on the first ceramic substrate (8) on the side of the laser carrier close to the modulator chip (15), and make the laser carriers correspond to the first collimating lenses (11) one by one; S2: Fix the second ceramic substrate (6) on the surface of the package housing (5) by silver glue patch, and then fix the modulator chip (15) on the surface of the second ceramic substrate (6) by silver glue patch. The modulator chip (15) is installed close to the end face of the second ceramic substrate (6), and a second collimating lens (14), or a plurality of focusing lenses (13) and a second collimating lens (14) are installed on the reserved end face; S3: Power on the first-channel laser for coupling. Among them, the laser chip (10) is coupled to the modulator chip (15) by a single-lens or double-lens method; S4: Optionally power on one or more channels of lasers, adjust the positions of the lenses and the adapter (7) on the second ceramic substrate (6), and perform the coupling from the modulator chip (15) to the fiber ferrule in the adapter (7); S5: Use the package cover plate (2) to cover the chamber of the package housing (5).

5. The high-speed modulator packaging method according to claim 4, wherein, In step S2, during the mounting process of the modulator chip (15), the following requirements need to be met: the light output port of the laser carrier in the Z direction is aligned with the light input port of the modulator chip (15), the distance from the laser carrier to the modulator chip (15) in the Y direction is obtained by simulation software, and the light output port of the laser carrier in the X direction is at the same height as the light input port of the modulator chip (15).

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