A heat sink for high-speed externally modulated laser packages and methods of using the same

Abstract

The application relates to the field of optoelectronic devices, in particular to a heat sink for high-speed external modulation laser package and a use method thereof. The heat sink for high-speed external modulation laser package comprises a heat sink, an electrode assembly and a through hole, wherein: the heat sink is divided into at least three layers, the surface layer and the bottom layer of the heat sink are coated with an alloy film, and the middle layer of the heat sink is coated with a tungsten film; the ground electrode of the electrode assembly covers at least one through hole; the through hole penetrates the heat sink, and the electrode assembly covers the surface layer of the heat sink. When the integrated high-speed external modulation laser works, the heat sink can simultaneously load electrical signals to the distributed feedback laser and the electro-absorption modulator. The middle layer of the heat sink is coated with a tungsten film, the polarization ability of tungsten is strong, a flat plate capacitor is easily formed, the flat plate capacitor spacing is reduced, the capacitance value is reduced, the response bandwidth is improved, and the high-frequency characteristics of the device are improved.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic devices, and in particular to a heat sink for packaging a high-speed externally modulated laser and its application method. Background Technology

[0002] The rapid development of 5G technology has greatly promoted the development of high-speed externally modulated lasers. High-speed externally modulated lasers, which monolithically integrate a distributed feedback laser (DFB) and an electro-absorption modulator (EAM), play a crucial role as a stable and reliable light source in long-distance high-speed fiber optic transmission systems. However, the heat sink for integrated devices cannot be the same as that used in discrete devices. This is because the electrical signals required for the operation of the DFB and EAM in integrated devices must be applied simultaneously, necessitating a redesign of the electrode positions on the heat sink. Furthermore, the optocoupler effect of the large capacitor on a typical heat sink reduces the response bandwidth of the integrated light source and deteriorates the high-frequency characteristics of the high-speed externally modulated laser; therefore, it is necessary to reduce the capacitance value of the heat sink used in the packaging.

[0003] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the technical problem to be solved by the present invention is to provide a heat sink for packaging high-speed externally modulated lasers and its usage method, with the aim of solving the technical problem of large capacitance value of the heat sink for packaging high-speed externally modulated lasers.

[0005] To achieve the above objectives, according to one aspect of the present invention, a heat sink for packaging a high-speed externally modulated laser is provided, comprising: a heat sink 1, an electrode assembly 2, and a through-hole 3, wherein:

[0006] The heat sink 1 is divided into at least three layers: the surface layer and the bottom layer of the heat sink 1 are deposited with an alloy thin film, and the middle layer of the heat sink 1 is deposited with a tungsten thin film.

[0007] The ground electrode 21 of the electrode assembly 2 covers at least one of the through holes 3;

[0008] The through hole 3 penetrates the heat sink 1, and the electrode assembly 2 covers the surface of the heat sink 1.

[0009] Preferably, solder 4 is attached to the surface of the heat sink 1, and the solder 4 is used to weld and fix the laser 5 to the heat sink 1.

[0010] Preferably, the electrode assembly 2 includes a first electrode 22 and a second electrode 23, wherein:

[0011] The first electrode 22 and the second electrode 23 are respectively disposed on the edge of the heat sink 1, and the first electrode 22 and the second electrode 23 are respectively connected to the top of the laser pad 51 and the modulator pad 52 by gold wires.

[0012] Preferably, the through hole 3 includes at least a first through hole 31 and a second through hole 32, wherein:

[0013] The first through hole 31 and the second through hole 32 are located at the bottom of the laser 5. The first through hole 31 and the second through hole 32 are located on the same line. The first through hole 31 and the second through hole 32 correspond to the bottom of the laser and the modulator in the high-speed externally modulated laser, respectively.

[0014] Preferably, the laser pad 51 and the modulator pad 52 are located on opposite sides of the laser 5, wherein:

[0015] The laser pad 51 is connected to the surface of the heat sink 1 by gold wire, and the laser pad 51 is connected to the first electrode 22 through the alloy thin film circuit on the surface of the heat sink 1.

[0016] The modulator pad 52 is connected to the second electrode 23 through the alloy thin film circuit on the surface of the heat sink 1, and the modulator pad 52 is connected to the ground electrode 21 through the alloy thin film circuit on the surface of the heat sink 1.

[0017] Preferably, a capacitor 6 and a resistor 7 are provided between the modulator pad 52 and the ground electrode 21, the capacitor 6 and the resistor 7 are connected in series, and the resistor 7 is connected to the ground electrode 21.

[0018] Preferably, the through hole 3 is filled with tungsten material from top to bottom.

[0019] Preferably, the heat sink 1 is made of aluminum nitride, and the surface and bottom layers of the heat sink 1 are coated with Ti / Pt / Au alloy thin films. The surface layer of the heat sink 1 has a thickness of 0.9 μm; the intermediate layer of the heat sink 1 has a thickness of 5 to 20 μm; and the bottom layer of the heat sink 1 has a thickness of 0.9 μm.

[0020] Preferably, the surface of the heat sink 1 is provided with an isolation metal 8, which is located on both sides of the solder 4. When the solder 4 melts, the isolation metal 8 prevents the solder 4 from overflowing and prevents a short circuit from occurring on the surface of the heat sink 1.

[0021] Secondly, the present invention provides a method for using a heat sink for packaging a high-speed externally modulated laser. The heat sink described in the first aspect is placed on a temperature control platform, which is grounded. A DC probe is pressed onto the first electrode of the heat sink, and a high-frequency probe is pressed onto the second electrode of the heat sink. The DC probe is loaded with a positive current, and the high-frequency probe is loaded with a negative voltage, causing the high-speed externally modulated laser to emit laser light or adjust its intensity. When the positive current on the DC probe is greater than the lasing current of the laser, the laser emits laser light. The negative voltage on the high-frequency probe is adjusted; the greater the negative voltage, the lower the laser intensity.

[0022] The present invention has the following beneficial effects:

[0023] The heat sink used in the packaging of high-speed externally modulated lasers can simultaneously load electrical signals to both the distributed feedback laser and the electro-absorption modulator when the integrated high-speed externally modulated laser is working. A tungsten thin film is deposited in the middle layer of the heat sink. Tungsten has strong polarization ability and easily forms parallel plate capacitors, thus reducing the spacing between the parallel plate capacitors, reducing the capacitance value, increasing the response bandwidth, and improving the high-frequency characteristics of the device. The capacitor on the heat sink is connected to the electro-absorption modulator through a gold wire, guiding the high-frequency signal coupled from the electro-absorption modulator to the distributed feedback laser to the ground electrode, avoiding additional modulation to the distributed feedback laser and eliminating the influence of optocoupler. The thin-film resistor on the heat sink is connected in parallel with the electro-absorption modulator through a capacitor, reducing the high resistance of the electro-absorption modulator during operation. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0025] Figure 1 This is a schematic diagram of the surface layer of a heat sink for packaging a high-speed externally modulated laser, provided in an embodiment of the present invention.

[0026] Figure 2 This is a side view of a heat sink for packaging a high-speed externally modulated laser provided in an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the surface layer of a heat sink for packaging a high-speed externally modulated laser, provided in an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of an overall heat sink for packaging a high-speed externally modulated laser, provided in an embodiment of the present invention.

[0029] Figure 5This is a schematic diagram of an intermediate layer for a heat sink used in packaging a high-speed externally modulated laser, provided in an embodiment of the present invention.

[0030] Figure 6 This is a schematic diagram of the second electrode of a heat sink for packaging a high-speed externally modulated laser, provided in an embodiment of the present invention.

[0031] Figure 7 This is a circuit diagram of a heat sink for packaging a high-speed externally modulated laser provided in this embodiment of the invention.

[0032] 1-Heat sink; 2-Electrode assembly; 21-Ground electrode; 22-First electrode; 23-Second electrode; 3-Through hole; 31-First through hole; 32-Second through hole; 4-Solder; 5-Laser; 51-Laser pad; 52-Modulator pad; 6-Capacitor; 7-Resistor; 8-Isolation metal. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] In the description of this invention, the terms "inner", "outer", "longitudinal", "lateral", "upper", "lower", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and do not require that this invention must be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0035] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] Example 1:

[0037] To address the technical challenge of large capacitance values ​​in heat sinks for packaging high-speed externally modulated lasers, this embodiment provides a heat sink for packaging high-speed externally modulated lasers, such as... Figure 1As shown, it includes: a heat sink 1, an electrode assembly 2, and a through hole 3, wherein:

[0038] The heat sink 1 is divided into at least three layers: the surface layer and the bottom layer of the heat sink 1 are coated with an alloy thin film, and the middle layer of the heat sink 1 is coated with a tungsten thin film.

[0039] In this first embodiment, as Figure 2 As shown, heat sink 1 has a 3-layer AlN ceramic structure. The surface layer of heat sink 1 is coated with a Ti / Pt / Au alloy film, the second layer is coated with a tungsten film, and the third layer is coated with a Ti / Pt / Au alloy film.

[0040] like Figure 3 and Figure 4 As shown, the ground electrode 21 of the electrode assembly 2 covers at least one of the through holes 3.

[0041] In this first embodiment, the electrode assembly 2 includes a ground electrode 21, a first electrode 22, and a second electrode 23. The electrode assembly 2 is deposited on a Ti / Pt / Au thin film on the first layer surface of the heat sink 1, and Au is deposited on the surfaces of the first electrode 22, the second electrode 23, and the ground electrode 21.

[0042] In this first embodiment, the first electrode 22 is deposited on the long side of the heat sink 1 to provide the bias current required for the operation of the high-speed externally modulated laser (DFB). In three-port testing, it can also be used to directly provide the high-frequency modulation signal required by the laser. The first electrode 22 is deposited on a Ti / Pt / Au alloy thin film on the surface of the heat sink 1 and is connected to the laser pad 51 on the top of the laser via a gold wire.

[0043] In this embodiment, the second electrode 23 is deposited on the short side of the heat sink 1 and is used to apply the bias voltage and high-speed modulation signal required for modulation to the modulator (EAM) of the high-speed externally modulated laser. The second electrode 23 is deposited on the Ti / Pt / Au alloy film on the surface of the heat sink 1 and is connected to the modulator pad 52 on the top of the modulator via a gold wire. Since the Ti / Pt / Au film covers the surface of the heat sink, the gold wire can be connected to the Ti / Pt / Au alloy film nearby, avoiding the adverse effects caused by excessively long gold wires. The adverse effects include that the resistance of the gold wire is proportional to its length, and the resistance is large when the gold wire is too long. Secondly, the current flowing through the gold wire will cause the gold wire to heat up, and the longer the gold wire, the more obvious the heating phenomenon.

[0044] In order to connect the ground electrode 21 to the "ground" signal, the through hole 3 penetrates the heat sink 1, and the electrode assembly 2 covers the surface of the heat sink 1.

[0045] Through hole 3 is drilled on ground electrode 21 and penetrates 3 layers of heat sink 1 made of AlN ceramic. Through hole 3 is filled with tungsten material from top to bottom, and through hole 3 connects ground electrode 21 with the "ground" signal.

[0046] like Figure 5 The diagram shown is a top view of the second layer surface of a heat sink for packaging a high-speed externally modulated laser according to Embodiment 1. A tungsten thin film with a thickness of 5–20 μm is deposited on the second layer surface of the heat sink 1. Tungsten has strong polarization ability and easily forms electrode plate surfaces, which, together with the surface layer of the heat sink 1, constitute an equivalent parallel-plate capacitor. Furthermore, because the distance between the surface layer and the second layer surface of the heat sink 1 is very close (approximately 1 cm), the capacitance value of the parallel-plate capacitor is inversely proportional to the distance between the capacitor plates, thus greatly reducing the capacitance, increasing the response bandwidth, and thereby improving the high-frequency response characteristics of the device.

[0047] The formula for calculating the capacitance of a parallel-plate capacitor is: C = εS / 4πkd

[0048] Where ε is the relative permittivity, S is the plate area, k is the electrostatic constant, and d is the plate spacing.

[0049] This formula shows that the capacitance is inversely proportional to the distance between the plates. That is, the greater the distance between the plates, the smaller the capacitance. Since the capacitance formed by the heat sink and the capacitance formed by the laser 5 are connected in series (because the laser is directly soldered to the heat sink), the size of the series capacitance is equal to the sum of the reciprocals of the values ​​of each discrete capacitor (equivalent to resistors in parallel), thus reducing the overall capacitance.

[0050] Solder 4 is attached to the surface of the heat sink 1, and the solder 4 is used to weld and fix the laser 5 to the heat sink 1. In this embodiment, the solder 4 is Au. 0.7 Sn 0.3 The material has a thickness of 5μm.

[0051] To separately adjust the laser emission and intensity, the electrode assembly 2 includes a first electrode 22 and a second electrode 23, wherein:

[0052] The first electrode 22 and the second electrode 23 are respectively disposed on the edge of the heat sink 1, and the first electrode 22 and the second electrode 23 are respectively connected to the top of the laser pad 51 and the modulator pad 52 by gold wires.

[0053] In this first embodiment, as Figure 1 , Figure 3 and Figure 4 As shown, the first electrode 22 is deposited on the long side of the heat sink 1 to provide the bias current required for the operation of the high-speed externally modulated laser (DFB). In three-port testing, it can also be used to directly provide the high-frequency modulation signal required for the laser. The second electrode 23 is deposited on the short side of the heat sink 1 to apply the bias voltage and high-speed modulation signal required for modulation to the modulator (EAM) of the high-speed externally modulated laser.

[0054] The modulator pad 52 of the high-speed externally modulated laser is connected to the left Ti / Pt / Au thin film via a gold wire. The Ti / Pt / Au thin film is connected to the ground electrode 21 via a series thin-film resistor 7, forming a circuit loop. Simultaneously, the modulator pad 52 is connected to the right Ti / Pt / Au thin film via a gold wire, and the right Ti / Pt / Au thin film is connected to the second electrode 23, achieving signal loading. The laser pad 51 of the high-speed externally modulated laser is connected to the left Ti / Pt / Au thin film via a gold wire, and the left Ti / Pt / Au thin film is connected to the first electrode 22, achieving signal loading. This design aims to minimize the length of the gold wire and avoid its impact on device performance. The second electrode 23 is positioned below to provide a sufficiently large area for loading the high-frequency probe during testing. When loading the high-frequency probe, the middle electrode of the second electrode 23 is reverse biased, while the two side electrodes are grounded. Therefore, the via 3 is placed on both sides, and in actual testing, they share a common ground. A schematic diagram of the second electrode 23 is shown below. Figure 6 As shown, in this first embodiment, the second electrode 23 is composed of three alloy films separated by a middle section. The square in the middle represents the middle electrode of the second electrode 23, which is loaded with a reverse bias voltage. The squares on both sides represent the two side electrodes of the second electrode 23, which are loaded with a "ground" signal. The through hole 3 is drilled on the alloy film connected to the two side squares, and the through hole 3 avoids touching the alloy film connected to the middle square.

[0055] To avoid short circuits, the through hole 3 includes at least a first through hole 31 and a second through hole 32, wherein:

[0056] The first through hole 31 and the second through hole 32 are located at the bottom of the laser 5. The first through hole 31 and the second through hole 32 are located on the same line. The first through hole 31 and the second through hole 32 correspond to the bottom of the laser and the modulator in the high-speed externally modulated laser, respectively.

[0057] In this first embodiment, as Figure 3 As shown, the first through-hole 31 and the second through-hole 32 are in direct contact with the bottom surface of the laser 5, but not with the laser pad 51 and the modulator pad 52. The laser pad 51 and the modulator pad 52 are used to load the positive signal, and the first through-hole 31 and the second through-hole 32 are connected to the "ground" signal. The first through-hole 31 and the second through-hole 32 are located directly below the laser 5, while the laser pad 51 and the modulator pad 52 are located on both sides of the laser 5. Figure 3 In the high-speed externally modulated laser 5, it is divided into two parts: a laser DFB and a modulator EAM. The laser DFB and the modulator EAM together form the high-speed externally modulated laser.

[0058] To avoid short circuits, the laser pad 51 and the modulator pad 52 are located on opposite sides of the laser 5, wherein:

[0059] The laser pad 51 is connected to the surface of the heat sink 1 by gold wire, and the laser pad 51 is connected to the first electrode 22 through the alloy thin film circuit on the surface of the heat sink 1.

[0060] The modulator pad 52 is connected to the second electrode 23 through the alloy thin film circuit on the surface of the heat sink 1, and the modulator pad 52 is connected to the ground electrode 21 through the alloy thin film circuit on the surface of the heat sink 1.

[0061] In this first embodiment, as Figure 4 As shown, the top of the modulator pad 52 is connected to the second electrode 23 and the ground electrode 21 by two gold wires, which are indicated by dashed lines. The laser pad 51 is connected to the circuit of the first electrode 22. Since the electrical signal can only be applied through the electrodes during testing, the probe cannot be inserted into the pad. To minimize the length of the gold wires, the gold wires are directly connected to the pad and the nearest alloy film. To facilitate probe loading during testing, the second electrode is located at the edge of the heat sink, but this would place the second electrode far from the laser pad, requiring a very long gold wire for connection. Therefore, an alloy film circuit is covered on the surface of the heat sink to reduce the length of the gold wires.

[0062] In order to improve the response bandwidth of the high-speed externally modulated laser and enhance the high-frequency characteristics of the device, a capacitor 6 and a resistor 7 are provided between the modulator pad 52 and the ground electrode 21. The capacitor 6 and the resistor 7 are connected in series, and the resistor 7 is connected to the ground electrode 21.

[0063] like Figure 4 As shown, capacitor 6 and resistor 7 are selected as surface mount capacitor 6 and thin film resistor 7. Capacitor 6 is located on ground electrode 4 and has a capacitance of 1pF. Capacitor 6 is connected to modulator pad 52 via gold wire. Capacitor 6 is connected in parallel with the modulator. Its function is to guide the coupled electrical signal between the laser and modulator of the high-speed externally modulated laser to ground, avoid additional modulation of the laser by the coupled signal, eliminate the influence of optocoupler, improve the response bandwidth of the high-speed externally modulated laser, and enhance the high-frequency characteristics of the device.

[0064] Resistor 7 is located on one side of capacitor 6 and connected to ground electrode 4. A matching thin-film resistor with a resistance of 25Ω is selected. In actual fabrication, thin-film resistor 7 is connected in series with surface-mount capacitor 6, and thin-film resistor 7 is connected in parallel with the modulator. Its function is to reduce the high resistance at the modulator end when the high-speed externally modulated laser is working, facilitating the testing of the high-frequency characteristics of the high-speed externally modulated laser.

[0065] If the resistance value increases or decreases relative to 25Ω, and the capacitance value increases or decreases relative to 1pF, and the resistance value increases relative to 25Ω, the overall parallel resistance increases, making it impossible to effectively reduce the high resistance at the modulator end when the high-speed externally modulated laser is operating. The resistance can be reduced, but this may result in a mismatch with the laser; as mentioned earlier, the thin-film resistor is a matching thin-film resistor. The smaller the capacitance value, the better, but currently, it is not possible to achieve a surface-mount capacitor with a smaller capacitance value.

[0066] The through-hole 3 is filled with tungsten material from top to bottom.

[0067] Through-hole 3 is filled with tungsten material from top to bottom, allowing the heat sink to be connected to the ground electrode 21 "ground" signal from the surface to the bottom. In order to better connect with the intermediate layer of heat sink 1 by utilizing the strong polarization characteristics of tungsten, since the intermediate layer itself is made of tungsten material, tungsten material is also directly used in through-hole 3.

[0068] The heat sink 1 is made of aluminum nitride. The surface and bottom layers of the heat sink 1 are coated with Ti / Pt / Au alloy thin films. The surface layer of the heat sink 1 has a thickness of 0.9 μm; the middle layer of the heat sink 1 has a thickness of 5 to 20 μm; and the bottom layer of the heat sink 1 has a thickness of 0.9 μm.

[0069] The heat sink 1 is provided with an isolation metal 8 on its surface. The isolation metal 8 is located on both sides of the solder 4. When the solder 4 melts, the isolation metal 8 prevents the solder 4 from overflowing and prevents short circuits from occurring on the surface of the heat sink 1.

[0070] In this first embodiment, the isolation metal 8 is made of Pt material with a thickness of 0.7 μm. The isolation metal 8 is vapor-deposited on both sides of the solder 4, the capacitor 6, and the resistor 7. Pt has a high melting point, and when the solder 4 melts, the isolation metal 8 can effectively prevent the solder from overflowing and prevent short circuits from occurring on the surface of the heat sink 1.

[0071] Example 2:

[0072] This embodiment provides a method for using a heat sink in the packaging of a high-speed externally modulated laser, such as... Figure 7 As shown, the process includes: placing the heat sink for packaging the high-speed externally modulated laser from Embodiment 1 on a temperature control platform, which is grounded; pressing a DC probe onto the first electrode of the heat sink and a high-frequency probe onto the second electrode of the heat sink; applying a positive current to the DC probe and a negative voltage to the high-frequency probe, thereby causing the high-speed externally modulated laser to emit laser light or adjust its intensity. When the positive current on the DC probe is greater than the lasing current of the laser, the laser emits laser light; adjusting the negative voltage on the high-frequency probe results in a lower laser intensity as the negative voltage increases. Using the heat sink for packaging the high-speed externally modulated laser in Embodiment 2 increases the modulation bandwidth of the laser, improves the response bandwidth, and enhances the high-frequency characteristics of the device.

[0073] When using the high-speed externally modulated laser packaging heat sink in this embodiment 2, the heat sink 1 is divided into at least three layers: the surface and bottom layers of the heat sink 1 are deposited with an alloy thin film, and the middle layer of the heat sink 1 is deposited with a tungsten thin film. For example... Figure 2 As shown, heat sink 1 has a 3-layer AlN ceramic structure. The surface layer of heat sink 1 is deposited with a Ti / Pt / Au alloy film, the second layer with a tungsten film, and the third layer with a Ti / Pt / Au alloy film. The ground electrode 21 of electrode assembly 2 covers at least one through-hole 3, as shown... Figure 3 and Figure 4 As shown. Electrode assembly 2 includes a ground electrode 21, a first electrode 22, and a second electrode 23. Electrode assembly 2 is deposited on a Ti / Pt / Au thin film on the first layer surface of heat sink 1, and Au is deposited on the surfaces of the first electrode 22, the second electrode 23, and the ground electrode 21. The first electrode 22 is deposited on the long side of heat sink 1 and is used to provide the bias current required for the operation of the high-speed externally modulated laser (DFB). In three-port testing, it can also be used to directly provide the high-frequency modulation signal required by the laser.

[0074] The first electrode 22 is deposited on the Ti / Pt / Au alloy film on the surface of the heat sink 1 and connected to the laser pad 51 on top of the laser via a gold wire. The second electrode 23 is deposited on the short side of the heat sink 1 and is used to apply the bias voltage and high-speed modulation signal required for modulation to the modulator (EAM) of the high-speed externally modulated laser. The second electrode 23 is deposited on the Ti / Pt / Au alloy film on the surface of the heat sink 1 and connected to the modulator pad 52 on top of the modulator via a gold wire. Since the Ti / Pt / Au film covers the surface of the heat sink, the gold wire can be connected to the Ti / Pt / Au alloy film nearby, avoiding the adverse effects caused by excessively long gold wires.

[0075] Through-hole 3 penetrates heat sink 1, and electrode assembly 2 covers the surface of heat sink 1. Through-hole 3 is drilled on ground electrode 21 and penetrates the three layers of heat sink 1 made of AlN ceramic. Through-hole 3 is filled with tungsten material from top to bottom, and through-hole 3 connects ground electrode 21 to the "ground" signal.

[0076] like Figure 5 The diagram shown is a top view of the second layer surface of a heat sink for packaging a high-speed externally modulated laser according to Embodiment 2. A tungsten thin film with a thickness of 5–20 μm is deposited on the second layer surface of the heat sink 1. Tungsten has strong polarization ability and easily forms electrode plate surfaces, which, together with the surface layer of the heat sink 1, constitute an equivalent parallel-plate capacitor. Furthermore, because the distance between the surface layer and the second layer surface of the heat sink 1 is very close (approximately 1 cm), the capacitance value of the parallel-plate capacitor is inversely proportional to the distance between the capacitor plates, thus greatly reducing the capacitance, increasing the response bandwidth, and thereby improving the high-frequency response characteristics of the device.

[0077] The formula for calculating the capacitance of a parallel-plate capacitor is: C = εS / 4πkd

[0078] Where ε is the relative permittivity, S is the plate area, k is the electrostatic constant, and d is the plate spacing.

[0079] This formula shows that the capacitance is inversely proportional to the distance between the plates. That is, the greater the distance between the plates, the smaller the capacitance. Since the capacitance formed by the heat sink and the capacitance formed by the laser 5 are connected in series (because the laser is directly soldered to the heat sink), the size of the series capacitance is equal to the sum of the reciprocals of the values ​​of each discrete capacitor (equivalent to resistors in parallel), thus reducing the overall capacitance.

[0080] Electrode assembly 2 includes a first electrode 22 and a second electrode 23, wherein:

[0081] The first electrode 22 and the second electrode 23 are respectively disposed on the edge of the heat sink 1. The first electrode 22 and the second electrode 23 are respectively connected to the top of the laser pad 51 and the modulator pad 52 by gold wires.

[0082] In this second embodiment, as Figure 1 , Figure 3 and Figure 4 As shown, the first electrode 22 is deposited on the long side of the heat sink 1 to provide the bias current required for the operation of the high-speed externally modulated laser (DFB). In three-port testing, it can also be used to directly provide the high-frequency modulation signal required for the laser. The second electrode 23 is deposited on the short side of the heat sink 1 to apply the bias voltage and high-speed modulation signal required for modulation to the modulator (EAM) of the high-speed externally modulated laser.

[0083] The modulator pad 52 of the high-speed externally modulated laser is connected to the left Ti / Pt / Au thin film via a gold wire. The Ti / Pt / Au thin film is connected to the ground electrode 21 via a series thin-film resistor 7, forming a circuit loop. Simultaneously, the modulator pad 52 is connected to the right Ti / Pt / Au thin film via a gold wire, and the right Ti / Pt / Au thin film is connected to the second electrode 23, achieving signal loading. The laser pad 51 of the high-speed externally modulated laser is connected to the left Ti / Pt / Au thin film via a gold wire, and the left Ti / Pt / Au thin film is connected to the first electrode 22, achieving signal loading. This design aims to minimize the length of the gold wire and avoid its impact on device performance. The second electrode 23 is positioned below to provide a sufficiently large area for loading the high-frequency probe during testing. When loading the high-frequency probe, the middle electrode of the second electrode 23 is reverse biased, while the two side electrodes are grounded. Therefore, the via 3 is placed on both sides, and in actual testing, they share a common ground. A schematic diagram of the second electrode 23 is shown below. Figure 6As shown in the second embodiment, the second electrode 23 is composed of three alloy films separated by a middle section. The square in the middle represents the middle electrode of the second electrode 23, which is loaded with a reverse bias voltage. The squares on both sides represent the two side electrodes of the second electrode 23, which are loaded with a "ground" signal. The through hole 3 is drilled on the alloy film connected to the two side squares, and the through hole 3 avoids touching the alloy film connected to the middle square.

[0084] Through hole 3 includes at least a first through hole 31 and a second through hole 32, wherein:

[0085] The first through hole 31 and the second through hole 32 are located at the bottom of the laser 5. The first through hole 31 and the second through hole 32 are located on the same line. The first through hole 31 and the second through hole 32 correspond to the bottom of the laser and the modulator in the high-speed externally modulated laser, respectively.

[0086] In this second embodiment, as Figure 3 As shown, the first through-hole 31 and the second through-hole 32 are in direct contact with the bottom surface of the laser 5, but not with the laser pad 51 and the modulator pad 52. The laser pad 51 and the modulator pad 52 are used to load the positive signal, and the first through-hole 31 and the second through-hole 32 are connected to the "ground" signal. The first through-hole 31 and the second through-hole 32 are located directly below the laser 5, while the laser pad 51 and the modulator pad 52 are located on both sides of the laser 5. Figure 3 In the high-speed externally modulated laser 5, it is divided into two parts: a laser DFB and a modulator EAM. The laser DFB and the modulator EAM together form the high-speed externally modulated laser.

[0087] Laser pad 51 and modulator pad 52 are located on both sides of laser 5, respectively, wherein:

[0088] The laser pad 51 is connected to the surface of the heat sink 1 by gold wire, and the laser pad 51 is connected to the first electrode 22 through the alloy thin film circuit on the surface of the heat sink 1.

[0089] The modulator pad 52 is connected to the second electrode 23 through the alloy thin film circuit on the surface of the heat sink 1, and the modulator pad 52 is connected to the ground electrode 21 through the alloy thin film circuit on the surface of the heat sink 1.

[0090] In this second embodiment, as Figure 4As shown, the top of the modulator pad 52 is connected to the second electrode 23 and the ground electrode 21 by two gold wires. The laser pad 51 is connected to the circuit of the first electrode 22. Since the electrical signal can only be applied through the electrodes during testing, the probe cannot be inserted into the pad. To minimize the length of the gold wire, the gold wire directly connects the pad to the nearest alloy film. To facilitate probe loading during testing, the second electrode is located at the edge of the heat sink, but this would place the second electrode far from the laser pad, requiring a very long gold wire for connection. Therefore, an alloy film circuit is covered on the surface of the heat sink to reduce the length of the gold wire.

[0091] A capacitor 6 and a resistor 7 are provided between the modulator pad 52 and the ground electrode 21. The capacitor 6 and the resistor 7 are connected in series, and the resistor 7 is connected to the ground electrode 21.

[0092] like Figure 4 As shown, capacitor 6 and resistor 7 are selected as surface mount capacitor 6 and thin film resistor 7. Capacitor 6 is located on ground electrode 4 and has a capacitance of 1pF. Capacitor 6 is connected to modulator pad 52 via gold wire. Capacitor 6 is connected in parallel with the modulator. Its function is to guide the coupled electrical signal between the laser and modulator of the high-speed externally modulated laser to ground, avoid additional modulation of the laser by the coupled signal, eliminate the influence of optocoupler, improve the response bandwidth of the high-speed externally modulated laser, and enhance the high-frequency characteristics of the device.

[0093] Resistor 7 is located on one side of capacitor 6 and connected to ground electrode 4. A matching thin-film resistor with a resistance of 25Ω is selected. In actual fabrication, thin-film resistor 7 is connected in series with surface-mount capacitor 6, and thin-film resistor 7 is connected in parallel with the modulator. Its function is to reduce the high resistance at the modulator end when the high-speed externally modulated laser is working, facilitating the testing of the high-frequency characteristics of the high-speed externally modulated laser.

[0094] If the resistance value increases or decreases relative to 25Ω, and the capacitance value increases or decreases relative to 1pF, and the resistance value increases relative to 25Ω, the overall parallel resistance increases, making it impossible to effectively reduce the high resistance at the modulator end when the high-speed externally modulated laser is operating. It can be reduced, but this may result in a mismatch with the laser. A smaller capacitance value is better, but currently, it is not possible to achieve a surface-mount capacitor with a smaller capacitance value.

[0095] Tungsten material is filled into the through hole 3 from top to bottom.

[0096] Through-hole 3 is filled with tungsten material from top to bottom, allowing the heat sink to be connected to the ground electrode 21 "ground" signal from the surface to the bottom. In order to better connect with the intermediate layer of heat sink 1 by utilizing the strong polarization characteristics of tungsten, since the intermediate layer itself is made of tungsten material, tungsten material is also directly used in through-hole 3.

[0097] The material of heat sink 1 is aluminum nitride. The surface and bottom layers of heat sink 1 are coated with Ti / Pt / Au alloy thin films. The surface layer of heat sink 1 has a thickness of 0.9μm; the middle layer of heat sink 1 has a thickness of 5 to 20μm; and the bottom layer of heat sink 1 has a thickness of 0.9μm.

[0098] The surface of the heat sink 1 is provided with isolation metal 8, which is located on both sides of the solder 4. When the solder 4 melts, the isolation metal 8 prevents the solder 4 from overflowing and prevents short circuits from occurring on the surface of the heat sink 1.

[0099] In this second embodiment, the isolation metal 8 is made of Pt material with a thickness of 0.7 μm. The isolation metal 8 is vapor-deposited on both sides of the solder 4, capacitor 6, and resistor 7. Pt has a high melting point, and when the solder 4 melts, the isolation metal 8 can effectively prevent the solder from overflowing and prevent short circuits from occurring on the surface of the heat sink 1.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat sink for a high-speed externally modulated laser package, characterized by, The application relates to a heat sink (1), an electrode assembly (2) and a through hole (3), wherein: The heat sink (1) is divided into at least three layers, the surface layer and the bottom layer of the heat sink (1) are evaporated with alloy thin films, and the middle layer of the heat sink (1) is evaporated with tungsten thin films; The ground electrode (21) of the electrode assembly (2) covers at least one of the through holes (3); The through hole (3) penetrates the heat sink (1), the electrode assembly (2) covers the surface layer of the heat sink (1), the laser pad (51) and the modulator pad (52) are respectively located on the two sides of a laser (5), the laser pad (51) is connected with the surface layer of the heat sink (1) through gold wires, the laser pad (51) is communicated with the first electrode (22) of the electrode assembly (2) through the alloy thin film circuit of the surface layer of the heat sink (1), the modulator pad (52) is communicated with the second electrode (23) of the electrode assembly (2) through the alloy thin film circuit of the surface layer of the heat sink (1), and the modulator pad (52) is communicated with the ground electrode (21) through the alloy thin film circuit of the surface layer of the heat sink (1). The surface layer of the heat sink (1) is attached with solder (4), and the solder (4) is used for welding and fixing the laser (5) and the heat sink (1).

2. The heat sink for high speed externally modulated laser packages of claim 1, wherein, The first electrode (22) and the second electrode (23) are respectively arranged at the edges of the heat sink (1).

3. The heat sink for high speed TO laser packages of claim 1 wherein, The through hole (3) comprises at least a first through hole (31) and a second through hole (32), wherein:

4. The heat sink for high speed externally modulated laser packages of claim 1 wherein, The first through hole (31) and the second through hole (32) are located at the bottom of the laser (5), the first through hole (31) and the second through hole (32) are located on the same line, and the first through hole (31) and the second through hole (32) respectively correspond to the bottom of the laser and the modulator in the high-speed external modulation laser. A capacitor (6) and a resistor (7) are arranged between the modulator pad (52) and the ground electrode (21), the capacitor (6) and the resistor (7) are connected in series, and the resistor (7) is connected with the ground electrode (21).

5. The heat sink for high speed lateral lasing laser packages of claim 1 wherein, The through hole (3) is filled with tungsten material from top to bottom.

6. The heat sink for high speed lateral lasing laser packages of claim 4, wherein, The material of the heat sink (1) is selected from aluminum nitride, the surface layer and the bottom layer of the heat sink (1) are evaporated with Ti / Pt / Au alloy thin films, the thickness of the surface layer of the heat sink (1) is 0.9 microns, the thickness of the middle layer of the heat sink (1) is 5-20 microns, and the thickness of the bottom layer of the heat sink (1) is 0.9 microns.

7. The heat sink for high speed TO laser packages of claim 1 wherein, The surface layer of the heat sink (1) is provided with isolation metals (8), the isolation metals (8) are located on the two sides of the solder (4), when the solder (4) is melted, the isolation metals (8) prevent the solder (4) from overflowing and prevent the surface layer of the heat sink (1) from being short-circuited.

8. The heat sink for high speed TO laser packages of claim 2 wherein, ​ 9. A method of using a heat sink for a high-speed externally modulated laser package, the method comprising: The heat sink of the high-speed external modulation laser package of any one of claims 1 to 8 is placed on a temperature control platform, the temperature control platform is grounded, a direct current probe is pressed on the first electrode of the heat sink, a high-frequency probe is pressed on the second electrode of the heat sink, the direct current probe is loaded with a positive current, the high-frequency probe is loaded with a negative voltage, so that the high-speed external modulation laser emits laser or adjusts the laser intensity, when the positive current on the direct current probe is greater than the lasing current of the laser, the laser emits laser; the negative voltage on the high-frequency probe is adjusted, the greater the negative voltage, the smaller the laser intensity.

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