Optical receiver and method for manufacturing optical receiver

Abstract

The purpose of the present disclosure is to widen the bandwidth of an optical receiver through a simple configuration.　An optical receiver 100 according to the present disclosure comprises: a subcarrier 2; a PD 3 which is provided to the subcarrier 2 and which receives light and is driven by voltage supply from an external bias power supply E; and a dielectric layer 5 which is formed in the subcarrier 2.

Description

Optical Receiver and Method for Manufacturing the Same

[0001] The present disclosure relates to an optical receiver.

[0002] In a conventional optical receiver, a PD (Photodetector) is driven by a bias voltage supplied from a TIA (Transimpedance Amplifier) (see Non-Patent Document 1). On the other hand, when driving an APD (Avalanche Photodiode), the voltage from the TIA alone is not sufficient, so an external bias power supply is provided separately.

[0003] Conventionally, such an external bias power supply is provided outside the sub-carrier where the PD and TIA are provided, and is connected to the sub-carrier via a bypass capacitor for noise reduction via a metal wire, and supplies voltage to the PD.

[0004] Here, generally, the bandwidth of an optical receiver is determined by the impedance between the bypass capacitor and the PD. In a conventional optical receiver, since there is a lower limit to the length of the metal wire connecting the bypass capacitor and the sub-carrier, the distance between the bypass capacitor and the sub-carrier where the PD is provided cannot be sufficiently shortened, making it difficult to realize a broadband optical receiver.

[0005] Li et al., “100 Gbit / s co-designed optical receiver with hybrid integration”, Opt. Express. Vol. 29, no. 10, 14304, 2021.

[0006] In order to solve the above problems, an object of the present disclosure is to provide a technique capable of widening the bandwidth of an optical receiver with a simple configuration.

[0007] To achieve the above object, the optical receiver of the present disclosure employs a technique of forming a dielectric within a sub-carrier in which a light receiving element is provided.

[0008] Specifically, the optical receiver of the present disclosure comprises a subcarrier, a photodetector provided on the subcarrier that receives light and is driven by a voltage supplied from an external power source, and a dielectric formed within the subcarrier.

[0009] Furthermore, the dielectric may be formed within the GND via of the subcarrier.

[0010] Furthermore, a high-frequency line may be formed on the subcarrier, the photodetector may be in contact with one surface of the high-frequency line, and the dielectric may be in contact with the other surface of the high-frequency line.

[0011] Furthermore, a high-frequency line may be formed on the subcarrier, the photodetector may be in contact with one side of the high-frequency line, and the dielectric may be formed on the side of the subcarrier opposite to the side on which the high-frequency line is provided.

[0012] Furthermore, the dielectric material may be a chip capacitor.

[0013] Furthermore, the subcarrier may be provided with a Transsimpedance Amplifier (TIA) that supplies voltage to the photodetector.

[0014] More specifically, the present disclosure is a method for manufacturing an optical receiver comprising a subcarrier, a photodetector provided on the subcarrier that receives light and is driven by a voltage supplied from an external power source, and a dielectric formed within the subcarrier, wherein the dielectric is formed within the subcarrier by crystal growth.

[0015] Furthermore, the above disclosures can be combined as much as possible.

[0016] According to this disclosure, the bandwidth of an optical receiver can be widened with a simple configuration.

[0017] This is a diagram illustrating the configuration of an optical receiver according to the first embodiment of this disclosure. This is a graph illustrating the effects of the optical receiver according to the first embodiment in comparison with related optical receivers. This is a diagram illustrating the manufacturing process of the optical receiver according to the first embodiment. This is a diagram illustrating the manufacturing process of an optical receiver according to a modified example of the first embodiment. This is a diagram illustrating the configuration of an optical receiver according to a modified example of the first embodiment. This is a diagram illustrating the configuration of an optical receiver according to the second embodiment of this disclosure. This is a diagram illustrating the configuration of an optical receiver according to the third embodiment of this disclosure. This is a diagram illustrating the configuration of related optical receivers.

[0018] Embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments shown below. These examples are illustrative, and this disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. In this specification and in the drawings, components with the same reference numerals refer to the same components.

[0019] (First Embodiment) [Configuration of the Optical Receiver According to the First Embodiment] The optical receiver 100 according to the first embodiment of this disclosure will be described with reference to Figures 1 to 5. Figure 1 is a diagram illustrating the configuration of the optical receiver 100 according to the first embodiment. The optical receiver 100 mainly comprises a carrier 1, a subcarrier 2, a PD (Photodetector) 3, a TIA (Transimpedance Amplifier) ​​4, and a dielectric layer 5. The dielectric layer 5 is an example of a "dielectric" in this disclosure.

[0020] Specifically, the optical receiver 100 includes a subcarrier 2, a PD 3 provided on the subcarrier 2 that receives light and is driven by a voltage supplied from an external bias power supply E, and a dielectric layer 5 formed within the subcarrier 2.

[0021] Carrier 1 is formed from a metal having sufficiently high conductivity to function as a GND plane. Carrier 1 is made of, for example, gold-plated Kovar. Carrier 1 is formed to be considerably larger than subcarrier 2. Subcarrier 2 is arranged on carrier 1.

[0022] In this embodiment, the subcarrier 2 has dimensions of 3.0 × 5.0 × 0.15 (length × width × thickness) mm. ３ It is formed to a certain size. The size of the subcarrier 2 (combination of length, width, and thickness) is not limited to the above and is arbitrary depending on the components arranged on the subcarrier 2. However, in order to perform high-frequency operation, it is preferable that the thickness of the subcarrier 2 is 0.15 mm or less. Furthermore, by making the thickness of the subcarrier 2 0.15 mm or less, the shift of electromagnetic field modes can be suppressed. This makes it possible to obtain the desired frequency characteristics.

[0023] A GND via 2a is formed on the left side of the subcarrier 2. The GND via 2a is formed by filling it with copper. A dielectric layer 5 is provided above the GND via 2a. The subcarrier 2 is made of a material on which a GND via 2a can be formed, such as AlN (when InP is used for PD3), Si, or quartz. The subcarrier 2 may be multilayer or monolayer.

[0024] High-frequency lines 21, 22, and 23 are formed on the subcarrier 2. High-frequency line 21 is in contact with the lower left side of PD3. The upper surface of high-frequency line 21 is an example of "one side of the high-frequency line" in this disclosure. High-frequency line 22 is in contact with the lower right side of PD3 and the lower left side of TIA4. High-frequency line 23 is in contact with the lower right side of TIA4. Each high-frequency line is a high-frequency line having a backside GND surface. Each high-frequency line is, for example, a GND-surfaced coplanar line or a microstrip line. The subcarrier 2 functions as a dielectric layer for each high-frequency line. In this embodiment, the length of the high-frequency line 22 between PD3 and TIA4 is 0.2 mm. However, the length of each high-frequency line is not limited to this and is arbitrary depending on the size and arrangement of each component.

[0025] In this embodiment, PD3 is 0.3 × 0.4 × 0.15 (length × width × thickness) mm ３ It is a light-receiving element of a certain size. PD3 is made of, for example, InP. However, the size and material of PD3 are not limited to this and can be arbitrary depending on the application and circumstances. The direction of light incidence on PD3 is arbitrary; light may be incident from above, below, or the side.

[0026] PD3 is driven by a bias voltage supplied from TIA4 via the high-frequency line 22. Additionally, PD3 is supplied with a bias voltage from an external bias power supply E via the high-frequency line 21 and wire L.

[0027] In this embodiment, TIA4 is 2.0 × 3.0 × 0.15 (length × width × thickness) mm ３ It has a certain size. TIA4 is made of, for example, SiGe. However, the size and material of TIA4 are not limited to this and can be arbitrary depending on the application and circumstances.

[0028] In this embodiment, the dielectric layer 5 is formed in a flat plate shape and measures 0.1 × 0.1 × 0.0003 (length × width × thickness) mm. ３ It has a size of approximately 0.1 × 0.1 mm. ２ The plane size is not limited to this, and any larger plane size is acceptable. Also, 0.0003 mm is the lower limit of the thickness of the dielectric layer 5, and the thickness of the dielectric layer 5 may be greater than this. However, it is preferable that the thickness of the dielectric layer 5 does not exceed 150 μm (0.15 mm).

[0029] The dielectric layer 5 is, for example, SiO ２ The dielectric layer consists of the above. However, the material of the dielectric layer 5 is not limited to these. Specifically, the volume and material (relative permittivity) of the dielectric layer 5 are determined according to the frequency (noise) to be cut off. In other words, the volume and material (relative permittivity) are determined so as to secure the required capacitance according to the frequency to be cut off. For example, if the required capacitance according to the frequency to be cut off is 10 pF, the volume and material are determined so as to secure 10 pF.

[0030] Furthermore, the dielectric layer 5 requires a withstand voltage three to four times the driving voltage of PD3. For example, if the driving voltage of PD3 is 25V, the dielectric layer 5 needs to be designed with a withstand voltage of approximately 100V.

[0031] [Distribution of the dielectric layer] In this embodiment, the dielectric layer 5 is provided above the GND via 2a of the subcarrier 2. In other words, the dielectric layer 5 is embedded in the subcarrier 2 directly beneath the PD3. The lower surface of the dielectric layer 5 is in contact with the upper surface of the GND via 2a of the subcarrier 2, and the upper surface of the dielectric layer 5 is in contact with the lower surface of the high-frequency transmission line 21. The lower surface of the high-frequency transmission line 21 is an example of the "other surface of the high-frequency transmission line" in this disclosure. In particular, in this embodiment, each surface is in contact over its entire surface. As a result, the dielectric layer 5 functions as a bypass capacitor. In other words, it provides a bypass capacitor function to the PD3 or the subcarrier 2. Furthermore, because the dielectric layer 5 and the high-frequency transmission line 21 are in direct contact, the inductance between the dielectric layer 5 and the PD3 and the high-frequency transmission line 21 can be made negligibly small. Therefore, the bandwidth can be controlled only by adjusting the impedance between the PD3 and the TIA4.

[0032] [Effects] Next, the effects of the optical receiver 100 will be explained, referring to the graph in Figure 2 and comparing it with the related optical receiver 100A shown in Figure 8. As shown in Figure 8, the optical receiver 100A includes a carrier 1A, a subcarrier 2A, a PD 3A, a TIA 4A, and a bypass capacitor 5A. High-frequency lines 21A, 22A, and 23A are formed on the subcarrier 2A. The bypass capacitor 5A is connected to an external bias power supply E via wire L1 and to the high-frequency line 21 via wire L2.

[0033] Figure 2 shows the calculated frequency response characteristics of optical receiver 100 and optical receiver 100A. In the graph, A represents the frequency response characteristics of optical receiver 100, and B represents the frequency response characteristics of optical receiver 100A. The horizontal axis of the graph represents the frequency of the modulated frequency signal.

[0034] Here, the frequency response characteristics depend on the impedance value of the transmission line between the dielectric layer (bypass capacitor) and PD. In the case of the related optical receiver 100A, since there is a wire L2 between the bypass capacitor 5A and PD3, excessive peaking appears in the frequency response characteristics, causing bandwidth degradation. For this reason, as shown in the graph, the optical receiver 100 has a higher bandwidth than the optical receiver 100A.

[0035] Thus, according to this embodiment, there is no need to provide a wire between the dielectric layer 5 (bypass capacitor) and the PD3, the distance between the dielectric layer 5 and the PD3 can be sufficiently shortened, and an optical receiver 100 with a wide bandwidth and versatile frequency range can be realized.

[0036] [Manufacturing Process] Next, the manufacturing process of the optical receiver 100 will be explained with reference to Figure 3. First, as shown in step (1) in the figure, GND vias 2a are formed on the subcarrier 2. Specifically, GND vias 2a are formed by filling with copper.

[0037] Next, in step (2), a dielectric layer 5 is formed on top of the GND via 2a so as to be embedded in the subcarrier 2. Specifically, the film is formed using crystal growth by the CVD (chemical vapor deposition) method. However, the method for forming the dielectric layer 5 is not limited to this, and any method can be used.

[0038] Next, in step (3), high-frequency lines 21, 22, and 23 are formed on the subcarrier 2. In particular, the high-frequency lines 21 are formed such that the lower surface of the high-frequency line 21 is in contact with the upper surface of the dielectric layer 5.

[0039] Finally, in step (4), the PD3 and TIA4 are placed on the subcarrier 2. In this case, the left lower surface of the PD3 is in contact with the high-frequency line 21, the right lower surface of the PD3 and the left lower surface of the TIA4 are in contact with the high-frequency line 22, and the right lower surface of the TIA4 is in contact with the high-frequency line 23.

[0040] Furthermore, if subcarrier 2 is multilayered, the above process may be carried out while the subcarriers are being formed.

[0041] However, the configuration and manufacturing process of the sub-carrier are not limited to the above. A modified example of the manufacturing process will be described while referring to FIG. 4. FIG. 4 shows an example in which the sub-carrier is composed of a first portion 24 and a second portion 25.

[0042] First, as shown in process (1) in the figure, the GND via 2a is formed by filling the second portion 25 with copper.

[0043] Next, in process (2), the dielectric layer 5 and the high-frequency line 21 are formed on the second portion 25 in this order, and the high-frequency lines 22 and 23 are formed on the first portion 24.

[0044] Then, in process (3), the right surface of the second portion 25 and the left surface of the first portion 24 are adhered. The adhesion method is arbitrary, and it may be adhered by a chemical method or a mechanical method.

[0045] Finally, in process (4), the PD 3 and the TIA 4 are arranged on the sub-carrier 2.

[0046] [Modified Example] Also, the configuration in the vicinity of the dielectric layer 5 is not limited to the above. The optical receiver 101 according to the modified example of the first embodiment will be described while referring to FIG. 5.

[0047] In the optical receiver 101, a high-frequency line 26 is provided so as to contact the lower surface of the dielectric layer 5. The high-frequency line 26 has a line portion that extends downward from its left end and functions as GND.

[0048] The high-frequency lines 21, 26, and the dielectric layer 5 may be integrally configured to be adhesively attachable to the sub-carrier 2 as a postattachment.

[0049] (Second Embodiment) The optical receiver 200 according to the second embodiment of the present disclosure will be described while referring to FIG. 6.

[0050] In the optical receiver 200, a dielectric layer 5 is formed below the GND via 2a so as to be embedded in the subcarrier 2. In other words, the dielectric layer 5 is formed on the opposite side of the subcarrier 2 from the side on which the PD3 and TIA4 are provided. To put it another way, the dielectric layer 5 is formed on the opposite side of the subcarrier 2 from the side on which the high-frequency line 21 is provided. For this reason, in the manufacturing process, the direction in which crystal growth is performed using the CVD method is the opposite of step (2) in Figure 3.

[0051] In this embodiment as well, since the PD3 and the dielectric layer 5 can be connected without using wires, an optical receiver 200 with a wide bandwidth and versatile frequency range can be realized.

[0052] (Third Embodiment) The optical receiver 300 according to the third embodiment of this disclosure will be described with reference to Figure 7.

[0053] In the optical receiver 300, a barrel-shaped chip capacitor 6 is embedded in the subcarrier 2 instead of the dielectric layer 5. The chip capacitor 6 is embedded in the subcarrier 2 sandwiched between the high-frequency lines 27 and 28. The chip capacitor 6 is an example of a "dielectric" in this disclosure.

[0054] In this embodiment as well, since the PD3 and the chip capacitor 6 can be connected without using wires, an optical receiver 300 with a wide bandwidth and versatile frequency range can be realized.

[0055] 100, 101, 200, 300: Optical receiver 1: Carrier 2: Subcarrier 2a: GND via 21, 22, 23, 26, 27, 28: High-frequency transmission line 24: First part 25: Second part 3: PD 4: TIA 5: Dielectric layer 6: Chip capacitor

Claims

1. An optical receiver comprising: a subcarrier; a photodetector provided on the subcarrier that receives light and is driven by a voltage supplied from an external power source; and a dielectric formed within the subcarrier.

2. The optical receiver according to claim 1, wherein the dielectric is formed in the GND via of the subcarrier.

3. The optical receiver according to claim 2, wherein a high-frequency line is formed on the subcarrier, the photodetector is in contact with one surface of the high-frequency line, and the dielectric is in contact with the other surface of the high-frequency line.

4. The optical receiver according to claim 2, wherein a high-frequency line is formed on the subcarrier, the photodetector is in contact with one side of the high-frequency line, and the dielectric is formed on the side of the subcarrier opposite to the side on which the high-frequency line is provided.

5. The optical receiver according to claim 1, wherein the dielectric is a chip capacitor.

6. The optical receiver according to any one of claims 1 to 5, wherein the subcarrier is provided with a Transimpedance Amplifier (TIA) that supplies voltage to the photodetector.

7. A method for manufacturing an optical receiver having a subcarrier, a photodetector provided on the subcarrier that receives light and is driven by a voltage supplied from an external power source, and a dielectric formed within the subcarrier, wherein the dielectric is formed within the subcarrier by crystal growth.

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