Transition transmission carrier structure for improving packaging bandwidth of directly modulated laser

Abstract

The invention relates to a transition carrier structure for improving the packaging bandwidth of a directly modulated laser chip. The transition carrier structure comprises a first transition carrier transmission structure, a second transition carrier transmission structure and a gold bonding wire. The first transition transmission carrier structure comprises a first ground electrode, a first signal transmission line and a first ground accompanying hole, and the second transition carrier structure comprises a second ground electrode, a second signal transmission line and a second ground accompanying hole. The first transition carrier structure and the second transition carrier structure are connected through gold bonding wires. The transition carrier packaging structure provided by the invention can be well applied to packaging of a laser chip, compensation transition area welding and electric parasitic parameters introduced by gold wire bonding, and reduction of loss generated in a signal transmission process, so that the packaging bandwidth of the laser chip is improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-frequency packaging of microwave photonic chips, and in particular to a transition transmission carrier structure for improving the packaging bandwidth of a direct-modulated laser. Background Art

[0002] There are two ways to modulate the laser light field: external modulation and direct modulation. Modulation using external modulation devices such as electro-absorption modulators or Mach-Zehnder modulators is external modulation. Compared with external modulation, direct modulation has the advantages of simple structure, low cost, high linearity, high reliability and high stability, and is therefore widely used in optical communication systems.

[0003] At present, for large-bandwidth laser chips, packaging has become the main factor limiting the overall bandwidth of the device. When designing the package, the main considerations are how to completely transmit microwave signals, how to control the temperature state of the chip when it is working, and how to efficiently perform photoelectric conversion, so as to determine its transmission carrier structure. The RF signal is fed from the tube shell to the RF input end of the chip. Since the chip requires a thermoelectric cooler TEC for temperature control, the transition matching carrier requires at least two independent transition transmission lines. One section is the tube shell RF feed to carrier one, and then transitions to carrier two, and is transmitted to the chip RF input end through carrier two. The chip and the carrier are grounded together, and a heat sink is placed under carrier two and the chip, and a temperature cooler TEC is placed under the heat sink. In order to consider the photoelectric conversion efficiency, the signal transmission side of carrier two cannot be too wide. General RF feed usually uses microstrip, coplanar waveguide and grounded coplanar waveguide. The intermediate transmission structure has characteristic impedance conversion and microwave mode matching problems, and the connection between electrodes usually uses gold wire bonding, but gold wire bonding will bring electrical parasitic effects, and there are shortcomings such as large transmission loss and narrow packaging bandwidth.

[0004] Therefore, it is necessary to realize a transition transmission carrier structure that improves the packaging bandwidth of a direct-modulated laser chip. Summary of the invention

[0005] The purpose of the present invention is to provide a transition transmission carrier structure for improving the packaging bandwidth of a direct-modulated laser chip. The transition transmission carrier structure for improving the packaging bandwidth of a direct-modulated laser chip can solve the deficiencies in the prior art, compensate for parasitic effects, reduce transmission losses, and improve the packaging bandwidth of the direct-modulated laser chip.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A transition transmission carrier structure for improving the packaging bandwidth of a direct-modulated laser comprises a first transition transmission carrier structure, a second transition transmission carrier structure and a bonding gold wire; the first transition transmission carrier structure and the second transition transmission carrier structure are connected in a gold wire cascade via the bonding gold wire.

[0008] The transition transmission carrier structure 1 includes a first substrate; a first ground electrode and a first signal transmission line are arranged on the first substrate; and a plurality of first ground companion holes distributed on both sides of the first signal transmission line are also arranged on the first substrate.

[0009] The second transition transmission carrier structure includes a second substrate; a second ground electrode and a second signal transmission line are arranged on the second substrate; and a plurality of second ground holes distributed on both sides of the second signal transmission line are also arranged on the second substrate.

[0010] Preferably, the transition transmission carrier structure 1 adopts a grounded coplanar waveguide GSG transmission structure. The GSG made of the transition transmission structure 1 has a GS spacing on the left side wider than that on the right side of the transition transmission structure 1. This design can not only compensate for the parameters introduced by the high-frequency gold wire and welding, but also effectively simulate the welding short circuit when the high-frequency insulator is welded to the transition transmission structure 1.

[0011] Preferably according to the present invention, one end of the transition transmission carrier structure 2 adopts a grounded coplanar waveguide GSG structure, and the other end adopts a single microstrip line structure; the end face of the single microstrip line structure is connected to the RF bias of the direct-modulated laser chip through a gold wire, and is connected to the high-frequency inductive welding.

[0012] Preferably according to the present invention, the substrate edge spacing between the transition transmission carrier structure 1 and the transition transmission carrier structure 2 is within 0.1 mm.

[0013] Preferably, according to the present invention, the distance between two bonding points of the bonding gold wire is within 0.2 mm; and the bonding length of the gold wire is within 0.25 mm.

[0014] Preferably according to the present invention, the substrates of the transitional transmission carrier structure 1 and the transitional transmission carrier structure 2 are made of alumina, aluminum nitride or glass, and the thickness is not more than 0.254 mm.

[0015] Preferably according to the present invention, the transition transmission carrier structure is cascaded with the radio frequency lead of the tube shell.

[0016] Preferably, the transition transmission carrier structure 1 and the transition transmission carrier structure 2 are implemented by HFSS simulation design. Since the actual model of the direct-modulated laser chip is very complex, it is difficult to bring its most realistic model into the HFSS model, but the influence of the gold wire at high frequency cannot be ignored. Therefore, during the HFSS simulation design, the present invention uses a 50-ohm microstrip to simulate the direct-modulated laser chip method, which is brought into the full-link cascade simulation system for simulation optimization design.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] The present invention uses transition transmission carrier structure 1, transition transmission carrier structure 2 and bonding gold wire to transitionally transmit the RF broadband signal from the tube shell to the RF bias port of the direct-modulated laser chip, compensates for the impedance matching compensation at discontinuities such as transmission mode conversion and welding during signal transmission, reduces reflections during signal transmission, and thus reduces insertion loss during signal transmission. The present invention can achieve a bandwidth of more than 32 GHz for the direct-modulated laser chip after packaging, achieving a good effect of improving the packaging bandwidth of the direct-modulated laser chip. Transition transmission structure 1 and transition transmission structure 2 are the innovative points of the present invention, especially their surface graphic structures. These two transition transmission structures are not designed according to the traditional 50 ohm transmission line, and are used to compensate for the parasitic parameters introduced by the bonding gold wire. The technical means used are HFSS simulation design means. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is an overall diagram of the transition transmission carrier structure in the present invention;

[0020] Figure 2 It is a schematic diagram of the cascade connection of the transition transmission structure, the tube shell, and the direct-modulation laser chip in the present invention;

[0021] Figure 3 It is a cascade simulation result diagram of the transition transmission structure in the present invention; wherein the abscissa represents the frequency in GHz; the ordinate represents the S21 insertion loss and the S11 return loss in dB;

[0022] Figure 4 This is a bandwidth test result diagram of the directly modulated laser after packaging; the horizontal axis represents the frequency in GHz; the vertical axis represents the S21 insertion loss in dB.

[0023] in:

[0024] 1. Transition transmission carrier structure one; 2. Transition transmission carrier structure two; 3. Bonding gold wire; 11. First transmission signal line; 12. First ground electrode; 13. First companion ground hole; 21. Second transmission signal line; 22. Second ground electrode; 23. Second companion ground hole; 24. Area for gold wire bonding and high-frequency inductive welding with the direct-modulation laser chip; 4. RF lead; 5. Analog direct-modulation laser chip; 6. Bonding gold wire between the transition transmission carrier structure two and the direct-modulation laser chip. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings:

[0026] like Figure 1 A transition transmission carrier structure for improving the bandwidth of a direct-modulated laser package, comprising a transition transmission carrier structure 1, a transition transmission carrier structure 2, and a bonding gold wire 3, wherein the transition transmission carrier structure 1 and the transition transmission carrier structure 2 are cascaded through the bonding gold wire 3. The transition transmission carrier structure 1 and the transition transmission carrier structure 2 are located on the same plane. The cascade connection is performed by two different transition transmission carrier structures and bonding gold wires, aiming to optimize the signal transmission path, thereby improving the bandwidth of the overall package. The bonding gold wire is used to transmit the radio frequency signal transmitted to the transition transmission carrier structure 1 to the transition transmission carrier structure 2. Gold wire is widely used in the interconnection of semiconductor devices due to its excellent conductivity, corrosion resistance and mechanical strength. Through bonding technology, low-impedance and high-reliability electrical connections can be achieved.

[0027] For general photonic chips, such as detectors and modulator chips, the radio frequency is fed into the chip surface, and only one high-frequency matching transition transmission structure is needed to achieve it. However, for direct-modulated laser chips, since direct-modulated laser chips require temperature control, two high-frequency matching transition transmission structures are required to achieve this. Compared with general photonic chips, there is one more level of high-frequency transition transmission structure and one more level of bonding gold wire, that is, two high-frequency transition transmission structures and two-level bonding gold wires are required to feed the radio frequency signal from the high-frequency insulator of the shell to the radio frequency port of the direct-modulated laser chip, which greatly increases the manufacturing difficulty. Therefore, the present invention uses HFSS simulation design means to creatively invent a high-frequency transition transmission structure, which is mainly a high-frequency matching transition transmission structure surface pattern, which solves the technical problem of high-frequency packaging of large-bandwidth direct-modulated laser chips. Transition transmission structure one and transition transmission structure two are the innovative points of the present invention, especially the surface pattern structures invented by the two through HFSS simulation design means, which can make up for the parasitic parameters introduced by bonding gold wires and welding at high frequencies, reduce return loss, and thus improve the chip packaging bandwidth.

[0028] Specifically, the transition transmission carrier structure 1 includes a first substrate; a first ground electrode 12 and a first signal transmission line 11 are arranged on the first substrate; and a plurality of first ground holes 13 distributed on both sides of the first signal transmission line are also arranged on the first substrate. The transition transmission carrier structure 2 includes a second substrate; a second ground electrode 22 and a second signal transmission line 21 are arranged on the second substrate; and a plurality of second ground holes 23 distributed on both sides of the second signal transmission line are also arranged on the second substrate. Both the transition transmission carrier structure 1 and the transition transmission carrier structure 2 contain ground holes, which are respectively distributed on both sides of the transmission signal line. The position, number and aperture size of the ground holes are specifically set according to the simulation results. The purpose of adopting the above structural design of the transition transmission carrier structure 1 and the transition transmission carrier structure 2 is to optimize the signal transmission path, reduce parasitic effects, and improve signal integrity and bandwidth. Among them, the substrate is used to provide mechanical support and electrical isolation. The signal electrode is used to receive or send electrical signals. The ground electrode is used to provide a ground reference point, which helps to stabilize the signal and reduce noise. The signal transmission line is used to transmit the signal from one position to another. Ground vias are distributed on both sides of the signal transmission line to improve the impedance matching of the signal transmission line and reduce parasitic effects. Ground vias can adjust the electromagnetic field distribution around the signal transmission line, thereby helping to achieve more precise characteristic impedance control, which is especially important for high-frequency signals because mismatched impedance can cause signal reflection and distortion. In addition, ground vias help reduce parasitic capacitance and inductance between the signal transmission line and the surrounding environment, reduce parasitic effects, and improve signal integrity.

[0029] In some embodiments, the transition transmission structure 1 adopts a grounded coplanar waveguide GSG transmission structure, and the RF port of the direct-modulated laser chip is a single microstrip line transmission structure. Therefore, one end of the transmission structure of the transition transmission structure 2 is a grounded coplanar waveguide GSG, and the other end is a single microstrip line form. In addition to being able to compensate for the parasitic parameters introduced by the bonding wire, this design can also perform transition conversion of high-frequency transmission forms. One end of the transition transmission carrier structure 2 is a grounded coplanar waveguide GSG structure, and the other end is a microstrip structure. The combination of the grounded coplanar waveguide GSG structure and the microstrip provides good impedance matching and signal integrity, reducing signal reflection and insertion loss. The grounded coplanar waveguide GSG structure is used to perform gold wire cascading with the transition transmission structure 1 to ensure good electrical connection. The microstrip structure is used to transmit broadband RF electrical signals to the RF input port of the direct-modulated laser chip. The transition transmission carrier structure 2 is provided with a microstrip structure at one end, and an area 24 for gold wire bonding and high-frequency inductive welding with the direct-modulated laser chip is provided. The end face of the microstrip structure can be welded with the RF bias of the direct-modulated laser chip and the high-frequency inductor. Among them, the conical inductor needs to select a high-frequency broadband inductor. Compared with the welding method, the amount of solder cannot be controlled, but the influence of the amount of solder on the high-frequency signal cannot be underestimated. Therefore, the surface material of the conical inductor port is selected as gold, and the conical inductor can be welded to the surface of the substrate by pressure welding.

[0030] In some embodiments, the substrate of the transition transmission carrier structure 1 and the transition transmission carrier structure 2 may be made of alumina, aluminum nitride or sapphire. The thickness of the plate is preferably no more than 0.254 mm. A thinner substrate can easily achieve a higher transmission rate. By properly selecting the substrate material and thickness, the bandwidth, signal integrity and thermal management performance of the package can be significantly improved, thereby meeting the requirements of high-speed optical communications and other high-frequency applications.

[0031] In some embodiments, in order to reduce signal transmission loss and reflection, the substrate edge spacing between the transition transmission carrier structure 1 and the transition transmission carrier structure 2 is controlled within 0.1 mm.

[0032] In some embodiments, in order to reduce the loss, the height of the bonding wire 3 is as short as possible, the spacing between the bonding points is as close as possible, and the length of the bonding wire 3 is as short as possible. Specifically, the height of the bonding wire connected between the transition transmission carrier structure 1 and the transition transmission carrier structure 2 is less than 0.15 mm, the spacing between the bonding points of the bonding wire 3 is less than 0.2 mm, and the length of the bonding wire 3 is less than 0.25 mm. Figure 3 As shown in the figure, when the gold wire bonding parameters are within this range, the S parameter simulation results show that the loss is small, and within the 32GHz bandwidth range, the return loss is ≤-17.42dB.

[0033] like Figure 2As shown, the transition transmission carrier structure 1 is cascaded with the RF lead of the tube shell. The RF signal is fed into the transition transmission carrier structure 1 through the tube shell, and then transmitted to the transition transmission carrier structure 2 2 through the bonding gold wire 3, and then transmitted to the RF bias port of the direct-modulated laser chip through the bonding gold wire 6 between the transition transmission carrier structure 2 and the direct-modulated laser chip. The signal enters the transition transmission carrier structure 1 from the external circuit, and then is transmitted to the transition transmission carrier structure 2 2 through the bonding gold wire 3. At the single microstrip end of the transition transmission carrier structure 2 2, the signal is connected to the RF bias pad and high-frequency inductor on the laser chip by welding to ensure high-quality transmission of the signal. At the microstrip end of the transition transmission carrier structure 2, the high-frequency broadband electrical signal is transmitted to the RF input port of the direct-modulated laser and is converted into an optical signal. The microstrip structure can provide low loss and high isolation, which is suitable for high-speed optical communication applications.

[0034] Figure 4 This is the bandwidth test result of the packaged direct modulated laser chip. According to GB / T 21548-2008 semiconductor laser measurement method, Figure 4 It can be seen that the 3dB bandwidth of the packaged direct-modulated laser can reach 40HGz, which meets expectations and greatly improves the packaging bandwidth of the direct-modulated laser chip.

[0035] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the scope of protection determined by the claims of the present invention.

Claims

1. A transition transmission carrier structure for improving the bandwidth of a direct-modulated laser package, characterized in that: It comprises a transition transmission carrier structure 1 (1), a transition transmission carrier structure 2 (2) and a bonding gold wire (3); the transition transmission carrier structure 1 (1) and the transition transmission carrier structure 2 (2) are connected by a bonding gold wire (3) to achieve gold wire cascading; The transition transmission carrier structure (1) comprises a first substrate; a first ground electrode (12) and a first signal transmission line (11) are arranged on the first substrate; and a plurality of first ground companion holes (13) distributed on both sides of the first signal transmission line are also arranged on the first substrate; The second transition transmission carrier structure (1) comprises a second substrate; a second ground electrode (22) and a second signal transmission line (21) are arranged on the second substrate; and a plurality of second ground holes (23) distributed on both sides of the second signal transmission line are also arranged on the second substrate.

2. The transition transmission carrier structure for improving the packaging bandwidth of a direct modulated laser according to claim 1, characterized in that: The first transition transmission carrier structure (1) adopts a grounded coplanar waveguide (GSG) transmission structure, one end of the second transition transmission carrier structure (2) adopts a grounded coplanar waveguide (GSG) structure, and the other end adopts a single microstrip line structure; the end face (24) of the single microstrip line structure is cascaded with the radio frequency bias port of the direct-modulated laser chip through a gold wire, and is connected to a high-frequency inductive welding.

3. The transition transmission carrier structure for improving the packaging bandwidth of a direct modulated laser according to claim 1, characterized in that: The substrate edge spacing between the transition transmission carrier structure 1 (1) and the transition transmission carrier structure 2 (2) is within 0.1 mm.

4. The transition transmission carrier structure for improving the packaging bandwidth of a direct modulated laser according to claim 1, characterized in that: The distance between two bonding points of the bonding gold wire (3) is within 0.2 mm; The length of the gold wire bonding (3) is within 0.25 mm.

5. The transition transmission carrier structure for improving the packaging bandwidth of a direct modulated laser according to claim 1, characterized in that: The substrates of the transition transmission carrier structure 1 (1) and the transition transmission carrier structure 2 (2) are made of aluminum oxide, aluminum nitride or glass, with a thickness of no more than 0.254 mm.

6. The transition transmission carrier structure for improving the packaging bandwidth of a direct modulated laser according to claim 1, characterized in that: The transition transmission carrier structure 1 (1) is cascaded with the radio frequency lead of the tube shell.

7. The transition transmission carrier structure for improving the packaging bandwidth of a direct modulated laser according to claim 1, characterized in that: The transition transmission carrier structure 1 (1) and the transition transmission carrier structure 2 (2) are implemented by HFSS simulation design.

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