Optical power converter

Abstract

[Problem] To provide an optical electric power supply converter that makes it possible to suppress any increase in the temperature of a semiconductor light-receiving element. [Solution] An optical electric power supply converter (1) has: a semiconductor light-receiving element (10) that converts, into electricity, an input light (L1) that has been inputted via an optical fiber cable; and a base (3) for securing the semiconductor light-receiving element (10). In the semiconductor light-receiving element (10), a photodiode (12) is provided on a first surface (11a) side of a semiconductor substrate (11) that is transparent with respect to the input light (L1), the first surface (11a) being secured to the base (3). A heat-conducting member (7) that is in close contact with a second surface (11b) side on the opposite side of the semiconductor substrate (11) from the first surface (11a) is secured to the base (3), the heat-conducting member (7) being transparent with respect to the input light (L1). The input light (L1) passes through the heat-conducting member (7) and enters the semiconductor light-receiving element (10), and part of the heat of the semiconductor light-receiving element (10) is transferred to the base (3) via the heat-conducting member (7).

Description

[Technical Field]

[0001] The present invention relates to an optical power supply converter that converts light input via an optical fiber cable into electric power and supplies the electric power. [Background technology]

[0002] In special environments, such as remote locations with no power supply facilities, environments where weak electromagnetic fields from power supply create noise, environments requiring explosion protection, and ultra-high voltage facilities where electrical interactions occur, it may not be possible to supply power to operate electronic devices via power cables. For this reason, optical power supply converters are used, which receive light sent via optical fiber cables to the vicinity of electronic devices, generate photoelectric current through photoelectric conversion, and supply power to them.

[0003] An optical power supply converter has a semiconductor light-receiving element for photoelectric conversion. The output voltage of this semiconductor light-receiving element is usually less than 1V. When a device receiving power from an optical power supply converter requires a high input voltage, an optical power supply converter with a higher output voltage is used. For example, as shown in Patent Document 1, by dividing the circular photodiode of the semiconductor light-receiving element into multiple equal sector-shaped segments by multiple grooves and connecting these in series, it is possible to increase the output voltage while reducing the output current.

[0004] The photoelectric conversion efficiency of a semiconductor photodetector is generally around 40% at most, so a portion of the input light is converted into electricity and output, while the remainder becomes heat, causing the temperature of the semiconductor photodetector to rise. As the temperature of the semiconductor photodetector increases, the photoelectric conversion efficiency decreases, and the output characteristics of the optical power-supply converter deteriorate. For example, as shown in the example of output characteristics in Figure 15, the output characteristics at room temperature, represented by curve A1, shift to curve A2 at temperatures higher than room temperature. As the temperature increases, the maximum operating point Pmax (maximum output power) shifts closer to the origin, resulting in a decrease in output power. Therefore, there is a need to promote heat dissipation in optical power-supply converters.

[0005] For example, Patent Document 2 describes a technology in which a semiconductor laser element is sandwiched between a block and a heat sink to promote heat dissipation from the semiconductor laser element, which generates heat when emitting light. One electrode of the semiconductor laser element is connected to the block, and the other electrode is connected to the heat sink. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2011 / 0108081 [Patent Document 2] Japanese Patent Application Publication No. 1-23592 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 2, light is emitted from the facet of the semiconductor laser element that is not in contact with the block or heat sink. Therefore, even if the block and heat sink do not transmit light, the block and heat sink can be in contact with the front and back sides of the semiconductor laser element, which have a large area, without interfering with the emission of light. This makes it easier for heat from the semiconductor laser element to be transferred to the block and heat sink, suppressing deterioration in light-emitting efficiency and durability due to heat from the semiconductor laser element.

[0008] On the other hand, a substrate on which the semiconductor light-receiving element of the optical power-feed converter is mounted is disposed on the front side or the opposite side (back side) of the surface on which the photodiode of the semiconductor light-receiving element is formed, and light is input to the semiconductor light-receiving element from the opposite side of the substrate. Therefore, it is difficult to provide a member equivalent to a heat sink on the opposite side of the substrate from the semiconductor light-receiving element, as this would block the input light.

[0009] Therefore, the heat from the semiconductor light-receiving element is only transferred to the outside via the substrate, with a small amount dissipated into the air. Even if a back-illuminated semiconductor light-receiving element is used, in which the front side on which the photodiode is formed is fixed to the substrate to facilitate heat transfer to the substrate, the temperature rise cannot be sufficiently suppressed, and a decrease in output power due to the temperature rise has been an issue.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical power feeding converter that can suppress a temperature rise in a semiconductor light receiving element. [Means for solving the problem]

[0011] The optical power supply converter of the present invention has a semiconductor light receiving element that photoelectrically converts input light input via an optical fiber cable, and a base for fixing the semiconductor light receiving element, wherein the semiconductor light receiving element has a photodiode on a first surface side of a semiconductor substrate that is transparent to the input light, and the first surface side is fixed to the base, and a heat transfer member that is transparent to the input light and is in close contact with a second surface side of the semiconductor substrate that faces the first surface a support portion integrally formed on the base so as to extend toward the heat transfer member; The semiconductor light-receiving element is fixed to the base, and is configured so that the input light passes through the heat-transfer member and is incident on the semiconductor light-receiving element, and a portion of the heat of the semiconductor light-receiving element is transferred to the base via the heat-transfer member.

[0012] According to the above configuration, the input light input through the optical fiber cable passes through the heat transfer member attached to the semiconductor light receiving element and enters the semiconductor light receiving element, and a part of the heat of the semiconductor light receiving element is transferred to the base via the heat transfer member. Therefore, the heat of the semiconductor light receiving element is transferred to the base not only from the first surface side on which the photodiode is formed, but also from the second surface side via the heat transfer member, which promotes heat dissipation of the semiconductor light receiving element 10, reduces temperature rise, and suppresses a decrease in output of the optical power supply converter. In addition, Since the support portion to which the heat transfer member is fixed is formed integrally with the base, the only interface where heat transfer is generally difficult is the interface between the heat transfer member and the support portion, making it easier to transfer heat to the base.

[0013] The photovoltaic power supply converter of the invention of claim 2 comprises: An optical power supply converter having a semiconductor light receiving element that photoelectrically converts input light input via an optical fiber cable, and a base for fixing the semiconductor light receiving element, wherein the semiconductor light receiving element has a photodiode on a first surface side of a semiconductor substrate that is transparent to the input light, and the first surface side is fixed to the base, and a heat transfer member that is transparent to the input light and is in close contact with a second surface side of the semiconductor substrate that faces the first surface is fixed to the base via a spacer member, and the input light is configured to pass through the heat transfer member and enter the semiconductor light receiving element, and a portion of the heat of the semiconductor light receiving element is configured to be transferred to the base via the heat transfer member.

[0014] According to the above configuration, input light input via the optical fiber cable passes through the heat transfer member attached to the semiconductor light receiving element and enters the semiconductor light receiving element, and a portion of the heat from the semiconductor light receiving element is transferred to the base via the heat transfer member. Therefore, heat from the semiconductor light receiving element is transferred to the base not only from the first surface side on which the photodiode is formed but also from the second surface side via the heat transfer member. This promotes heat dissipation from the semiconductor light receiving element 10, reduces temperature rise, and suppresses a decrease in output from the optical power supply converter. Furthermore, by fixing the heat transfer member to the base via a spacer member, if the spacer member is made of a material with excellent thermal conductivity, heat can be easily transferred from the heat transfer member to the base, and the heat transfer member and base can be easily formed.

[0016] Claim 3 The photovoltaic power converter of the present invention is as follows: 1 or 2 In the invention, the photodiode is formed by connecting a plurality of equal segments in series, the segments being divided by grooves extending radially from a center through which the optical axis of the input light passes in a direction perpendicular to this optical axis, and the heat transfer member is characterized in that it has a conical concave surface formed so that its axis of symmetry coincides with the optical axis in an area where the input light is irradiated on the opposite side of a contact surface that is brought into close contact with the second surface side of the semiconductor substrate. According to the above configuration, in order to increase the output voltage, the photodiode is formed by connecting multiple segments, each divided equally by multiple grooves extending radially from the center, in series. The illumination area of ​​input light from the optical fiber cable is circular, and its light intensity distribution decreases with increasing distance from the optical axis and is rotationally symmetrical about the optical axis. Therefore, to ensure that the input light is evenly incident on the multiple segments, the input light is input so that the optical axis passes through the center of the photodiode. The heat transfer member has a conical concave surface in the area illuminated by the input light. The circular illumination area of ​​the input light incident on this concave surface is converted into an annular shape and then incident on the photodiode. Therefore, the input light is incident on the photodiode only in the area near the optical axis where the high light intensity is achieved, avoiding the area near the center of the photodiode where the grooves, which are unable to perform photoelectric conversion, are concentrated. This allows the input light to be effectively utilized and promotes heat dissipation from the semiconductor light receiving element. [Effects of the Invention]

[0017] According to the optical power feeding converter of the present invention, it is possible to suppress the temperature rise of the semiconductor light receiving element, and to suppress the decrease in output power due to the temperature rise. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an external view of an optical power feeding converter according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of the optical power supply converter with the cover removed. [Figure 3] 3 is a cross-sectional view of a main part of the optical power feeding converter taken along line III-III in FIG. 2. [Figure 4] FIG. 10 is an exploded perspective view showing another example of the heat transfer member. [Figure 5] 10 is a graph showing the effect of a heat transfer member. [Figure 6] FIG. 3 is a cross-sectional view showing an example of a heat transfer member and a base. [Figure 7] 7 is a graph showing the effect of the heat transfer member of FIG. 6. [Figure 8] FIG. 10 is a cross-sectional view showing another example of the heat transfer member and the base. [Figure 9] 2 is a plan view showing a first surface side of a semiconductor substrate of the semiconductor light receiving element. FIG. [Figure 10] 10 is a plan view showing a wiring portion of a substrate on which the semiconductor light receiving element of FIG. 9 is mounted. [Figure 11] 11 is a cross-sectional view of a main part of the semiconductor light-receiving element of FIG. 9 mounted on the substrate of FIG. 10, taken along line XI-XI. [Figure 12] FIG. 2 is an explanatory diagram of the light intensity distribution of input light. [Figure 13] FIG. 10 is an explanatory diagram of a heat transfer member having a conical concave surface. [Figure 14] 10 is an explanatory diagram of input light entering a semiconductor light receiving element through a conical concave surface of a heat transfer member. FIG. [Figure 15] 10A and 10B are diagrams illustrating a decrease in output characteristics due to a rise in temperature of the optical power feeding converter. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, the mode for carrying out the present invention will be described based on examples. [Example]

[0020] 1 and 2, the optical power supply converter 1 has a pair of output terminals 2a and 2b for converting light (input light L1) input via, for example, a single-mode optical fiber cable OC into current and supplying it to the outside. A substrate 4 is fixed to a base 3 (stem) equipped with the pair of output terminals 2a and 2b, on which a semiconductor light receiving element 10 is mounted for generating current from the input light L1 by photoelectric conversion. A cover 5 is also fixed to the base 3 to protect and shield the semiconductor light receiving element 10 from light.

[0021] Infrared light having a wavelength in the range of, for example, 1 to 1.6 μm is often used as the input light L1 that is input to the semiconductor light receiving element 10 from the opening 5a provided in the cover 5 via the optical fiber cable OC. After being emitted from the output end E of the optical fiber cable OC, this input light L1 is a conical beam whose irradiation range widens as it travels.

[0022] The semiconductor light receiving element 10 is a back-illuminated light receiving element. As shown in FIGS. 2 and 3, a photodiode 12 is formed on a first surface 11a (front surface) of a semiconductor substrate 11 that is transparent to the input light L1, and this first surface 11a is fixed to a substrate 4. The substrate 4 has a wiring portion 4a for extracting a photocurrent generated by the semiconductor light receiving element 10, and the wiring portion 4a is connected to output terminals 2a and 2b by, for example, conductive wires 6a and 6b, respectively. The semiconductor light receiving element 10 has its first surface 11a facing the base 3 and is fixed to the base 3 via the substrate 4. The input light L1 is input to the semiconductor light receiving element 10 from a second surface 11b (back surface) facing the first surface 11a of the semiconductor substrate 11. The substrate 4 is preferably a ceramic substrate, which has better thermal conductivity than an epoxy substrate.

[0023] The output terminals 2a and 2b are fixed to a base 3 made of, for example, Kovar, which is primarily composed of iron and has a low thermal expansion coefficient, via insulating members 3a and 3b. A heat transfer member 7 is also fixed to the base 3 so as to cover the semiconductor light receiving element 10 and the substrate 4, and is in close contact with the second surface 11b of the semiconductor light receiving element 10.

[0024] The heat transfer member 7 has a main body 7a formed in the shape of a rectangular plate and two leg portions 7b extending from both longitudinal ends of the main body 7a toward the base 3. The main body 7a is a plate made of, for example, silicon (Si), which is transparent to the input light L1 and has excellent thermal conductivity. The thermal conductivity of silicon is lower than that of, for example, gold, copper, or aluminum, which are used as wiring materials, but higher than that of, for example, glass, which is transparent to the input light L1. The two leg portions 7b are formed integrally with the main body 7a, facilitating heat transfer from the main body 7a to the leg portions 7b. The two leg portions 7b are fixed to the base 3 with, for example, a thermally conductive paste as an adhesive. The semiconductor light receiving element 10 and the substrate 4, which are sandwiched between the heat transfer member 7 and the base 3, are accommodated between the two leg portions 7b.

[0025] The main body 7a of the heat transfer member 7 has a portion (contact surface) that is brought into close contact with the second surface 11b of the semiconductor substrate 11 of the semiconductor light receiving element 10, which is polished to a flat surface, for example. Similarly, the second surface 11b of the semiconductor substrate 11 of the semiconductor light receiving element 10 that is brought into close contact with the heat transfer member 7 is polished to a flat surface, for example. When the semiconductor light receiving element 10 and the heat transfer member 7 are brought into close contact with each other, thermally conductive grease that is transparent to the input light L1 may be applied to fill any minute gaps in the contacting portions.

[0026] Input light L1 passes through the heat transfer member 7 and the semiconductor substrate 11 of the semiconductor light receiving element 10 and enters the photodiode 12. A portion of this input light L1 is converted into an electric current by photoelectric conversion and output, while the remainder is converted into heat, causing the temperature of the semiconductor light receiving element 10 to rise. Most of the heat from the semiconductor light receiving element 10 is transferred to the base 3. The heat transfer path is as shown by arrow H1, from the substrate 4 on the first surface 11a side to the base 3, and as shown by arrow H2, from the heat transfer member 7 on the second surface 11b side to the base 3. The only part of the path indicated by arrow H2 where heat transfer is difficult is the interface between the leg 7b of the heat transfer member 7 and the base 3, but heat transfer can be improved by using, for example, a thermally conductive paste. The heat transferred to the base 3 is dissipated from the base 3 to the outside (e.g., the air) and also from the cover 5 fixed to the base 3. Heat is transferred to the base 3 from the first surface 11a and second surface 11b of the semiconductor light receiving element 10, which have larger areas, and heat dissipation is promoted, thereby minimizing the temperature rise of the semiconductor light receiving element 10.

[0027] 4, the heat transfer member 7 may be formed integrally with a rectangular, flat-plate-shaped main body 7a that is in close contact with the semiconductor light-receiving element 10 and legs 7c that follow the outer periphery of the main body 7a. This increases the contact area between the heat transfer member 7 and the base 3, making it easier to transfer heat from the semiconductor light-receiving element 10 to the base 3 via the heat transfer member 7. The substrate 4 on which the semiconductor light-receiving element 10 is mounted is accommodated inside the legs 7c, including the portion that electrically connects the output terminals 2a, 2b to the substrate 4. Although not shown, the heat transfer member 7 may also have a plurality of legs that are formed integrally with the rectangular, flat-plate-shaped main body 7a and follow the outer periphery of the main body 7a.

[0028] FIG. 5 shows the results of a simulation showing the relationship between the thickness t of the main body 7a of the heat transfer member 7 and the temperature rise ΔT of the semiconductor light receiving element 10 when input light L1 is input to the optical power converter 1 having the heat transfer member 7 and heat is generated at 1 W (=1 J / s). The temperature of the base 3 is maintained constant. A thickness t = 0 mm indicates a case where the heat transfer member 7 is not present. ● indicates the type of heat transfer member 7 having two legs 7b as shown in FIG. 2, and ◇ indicates the type of heat transfer member 7 having leg 7c as shown in FIG. 4. The main body 7a of the heat transfer member 7 is the same size, and the thicknesses of the legs 7b and 7c are the same. The leg thickness refers to the length from the side of the leg facing the semiconductor light receiving element 10 (inner side) to the opposite side (outer side) in the direction away from the semiconductor light receiving element 10. The height of the legs 7b and 7c, which corresponds to the total thickness of the semiconductor light receiving element 10 and the substrate 4, is, for example, 0.8 mm. The contact area between the leg 7c in FIG. 4 and the base 3 is approximately twice the contact area between the two legs 7b in FIG.

[0029] 5, it can be seen that up to a thickness t of the main body 7a of about 0.8 mm, the thicker the main body 7a, the smaller the temperature rise ΔT of the semiconductor light receiving element 10, and the easier it is for heat from the semiconductor light receiving element 10 to be transferred to the base 3 via the heat transfer member 7. It can also be seen that the type having the leg 7c of FIG. 4, which has a larger contact area with the base 3, has a smaller temperature rise ΔT than the type having the two leg parts 7b of FIG. 2, and therefore has improved heat transfer performance. Note that the value of the temperature rise ΔT varies depending on the size of the main body 7a, the size of the semiconductor light receiving element 10, etc., but it can be easily inferred that the same tendency as above will be observed.

[0030] 6, the heat transfer member 7 may be formed in the shape of a rectangular plate, and two support portions 3c on which both end portions of the heat transfer member 7, which are in close contact with the semiconductor light receiving element 10, are placed and fixed may be integrally formed with the base 3 so as to protrude from the base 3 toward the heat transfer member 7. In this case as well, heat from the semiconductor light receiving element 10 is transferred to the base 3 via the substrate 4 on the first surface 11a side as shown by arrow H1, and is also transferred to the base 3 via the heat transfer member 7 on the second surface 11b side that is in close contact with the semiconductor light receiving element 10 and the two support portions 3c as shown by arrow H3. The only place where heat transfer is difficult along the path indicated by arrow H3 is the interface between the heat transfer member 7 and the support portions 3c, but heat transfer is improved by using, for example, a thermally conductive paste to fix the heat transfer member 7 to the support portions 3c. Since heat can be transferred to the base 3 from the first surface 11a and second surface 11b of the semiconductor light receiving element 10, which have larger areas, heat dissipation is promoted and temperature rise is suppressed to a small level.

[0031] FIG. 7 shows the results of a simulation showing the relationship between the thickness t of the heat transfer member 7 and the temperature rise ΔT of the semiconductor light receiving element 10 when 1 W of input light L1 is input to the optical power supply converter 1 having the heat transfer member 7 and base 3 of FIG. 6. The thickness t = 0 mm indicates the case where the heat transfer member 7 is not present. The size of the support portion 3c is equal to the leg portion 7b of FIG. 2. Again, up to the thickness t of the main body portion 7a of approximately 0.8 mm, the thicker the heat transfer member 7, the smaller the temperature rise ΔT of the semiconductor light receiving element 10, and the more easily heat from the semiconductor light receiving element 10 is transferred to the base 3 via the heat transfer member 7. Although not shown, a support portion protruding from the base 3 along the outer periphery of the heat transfer member 7, which is formed in a rectangular, flat plate shape, may be formed integrally with the base 3.

[0032] 8, spacer members 8 made of a metal, such as aluminum or copper, having better thermal conductivity than the heat transfer member 7 may be disposed on both ends of the heat transfer member 7 formed in a rectangular plate shape or along the outer periphery of the heat transfer member 7, and the heat transfer member 7 may be in close contact with the semiconductor light receiving element 10 and fixed to the base 3 via the spacer members 8. In this case, too, heat from the semiconductor light receiving element 10 is conducted to the base 3 via the substrate 4 on the first surface 11a side as indicated by arrow H1, and is also conducted to the base 3 via the heat transfer member 7 on the second surface 11b side and the spacer member 8 as indicated by arrow H4. The path indicated by arrow H4 includes the interface between the spacer member 8 and the heat transfer member 7 and the interface between the spacer member 8 and the base 3, and heat is conducted from the heat transfer member 7 to the base 3 via the spacer member 8, which has high thermal conductivity, by improving heat conductivity using, for example, a thermally conductive paste. Therefore, heat can be transferred to the base 3 from the first surface 11a and the second surface 11b, which have larger areas, of the semiconductor light receiving element 10, thereby promoting heat dissipation, minimizing temperature rise, and facilitating the formation of the heat transfer member 7 and the base 3.

[0033] Next, the semiconductor light receiving element 10 will be described. In order to increase the output voltage of the semiconductor light receiving element 10, the photodiode 12 of the semiconductor light receiving element 10 has a plurality of segments equally divided in the circumferential direction by a plurality of grooves 13 extending radially from the center C of the photodiode 12, as shown in Figure 9. Here, the photodiode 12 is divided into eight equal parts, but the number of divisions can be appropriately set depending on the required voltage. Each of the plurality of segments has a pair of electrodes, and the electrode covering most of the surface of each segment is the second electrode 15, and the other electrode is the first electrode 14.

[0034] In order to connect all adjacent segments of the photodiode 12 in series by connecting the first electrode 14 of one segment with the second electrode 15 of the other segment, a wiring section 4a is formed on the substrate 4 on which the semiconductor light-receiving element 10 is mounted, as shown in Fig. 10. The wiring section 4a is provided with a wiring pattern formed to correspond to the second electrode 15 of each segment and extending to connect to the first electrode 14 of the adjacent segment, and with wiring patterns for connecting the conductive wires 6a and 6b at both ends of the series connection.

[0035] The first and second electrodes 14, 15 of the semiconductor light receiving element 10 are aligned with the corresponding wiring portion 4a of the substrate 4 and connected by, for example, lead-free solder paste. This fixes the semiconductor light receiving element 10 to the substrate 4 and forms a photodiode 12 in which a plurality of segments are connected in series. Figure 11 is a cross-sectional view of a main part of this series-connected photodiode 12, and is a cross-sectional view corresponding to line XI-XI in Figures 9 and 10.

[0036] The multiple segments constituting the photodiode 12 are formed on the first surface 11a side of the semiconductor substrate 11, with a circular PIN photodiode formed by laminating a first semiconductor layer 16, a light absorbing layer 17, and a second semiconductor layer 18, and the circular PIN photodiode is equally divided in the circumferential direction by multiple grooves 13. An insulating layer 19 is formed to cover the inside of the grooves 13 and the second semiconductor layer 18, and a second electrode 15 connected to the second semiconductor layer 18 through an opening formed in the insulating layer 19 is formed to cover most of the second semiconductor layer 18. The first electrode 14 is connected to the first semiconductor layer 16 through a connection hole that penetrates the second semiconductor layer 18 and the light absorbing layer 17. The insulating layer 19 is also formed on the inner wall of the connection hole.

[0037] The semiconductor substrate 11 is, for example, a semi-insulating InP substrate, and the first semiconductor layer 16 is, for example, an n-InP layer. The light absorption layer 17 is, for example, an InGaAs layer, the second semiconductor layer 18 is, for example, a p-InP layer, and the insulating layer 19 is, for example, a SiO2 layer. The first and second electrodes 14, 15 are formed of, for example, a metal containing gold as a main component. The wiring portion 4a of the substrate 4 is formed of, for example, a metal containing gold or copper as a main component. The first and second electrodes 14, 15 and the corresponding wiring portion 4a are connected by solder paste 20.

[0038] The optical fiber cable OC is fixed so that the optical axis OA of the input light L1 is perpendicular to the photodiode 12 and passes through the center C of the photodiode 12. The photodiode 12, which is made up of a plurality of circumferentially equally divided segments connected in series, generates heat due to the input light L1, causing the temperature of the semiconductor light receiving element 10 to rise. To keep this temperature rise to a minimum, a heat transfer member 7 is provided in close contact with the semiconductor light receiving element 10.

[0039] 12, input light L1 input through optical fiber cable OC spreads in a conical shape. The light intensity distribution of this input light L1 decreases with increasing distance from the optical axis OA of the input light L1, and exhibits a Gaussian distribution that is rotationally symmetrical about the optical axis OA. However, photodiode 12 has multiple grooves 13 extending radially from its center C in a direction perpendicular to the optical axis OA. Since photoelectric conversion is not possible in these grooves 13, the areas of high light intensity near the optical axis OA cannot be utilized near center C where the multiple grooves 13 are concentrated.

[0040] 13 and 14, a conical concave surface 7d is formed in the region of the heat transfer member 7 that is irradiated with the input light L1. This concave surface 7d is formed by recessing the surface of the rectangular, flat-plate-shaped main body 7a of the heat transfer member 7 opposite to the surface that is brought into close contact with the semiconductor light receiving element 10. For example, the conical concave surface 7d may be formed by a known etching technique, or may be formed by polishing.

[0041] The heat transfer member 7, which has a conical concave surface 7d, is positioned with respect to the semiconductor light receiving element 10 and fixed to the base 3 so that the optical axis OA of the input light L1 coincides with the axis of symmetry passing through the apex of the conical concave surface 7d and passes through the center C of the photodiode 12. As a result, the input light L1 is spread by the conical concave surface 7d so as to move away from the optical axis OA, and the circular irradiation area becomes annular. Then, the light whose irradiation area is annular is incident on the photodiode 12.

[0042] The heat transfer member 7 having the conical concave surface 7d prevents the input light L1 from being incident on the vicinity of the center C of the photodiode 12 where the plurality of radial grooves 13 gather, allowing the input light L1 to be used effectively. Furthermore, since the heat of the semiconductor light receiving element 10 is transferred to the base 3 not only through the substrate 4 but also through the heat transfer member 7, heat dissipation from the semiconductor light receiving element 10 is promoted and a rise in temperature of the semiconductor light receiving element 10 is suppressed. The conical concave surface 7d can also be formed on the heat transfer member 7 of the type shown in FIG. 4, FIG. 6 or FIG. 8.

[0043] In Figure 15, curve A1 shows the output characteristics of the optical power feeding converter at a certain temperature (e.g., room temperature), and curve A2 shows the output characteristics as the temperature rises. As the temperature rises, the maximum output power Pmax shifts toward the origin, i.e., the maximum output power Pmax decreases. The optical power feeding converter 1 equipped with the heat transfer member 7 can reduce the temperature rise by transferring some of the heat from the semiconductor light receiving element 10 to the base 3 via the heat transfer member 7, thereby promoting heat dissipation and reducing the temperature rise, thereby reducing this output decrease.

[0044] The operation and effects of the optical power feeding converter 1 will be described. Input light L1 input to the optical power feeding converter 1 via the optical fiber cable OC passes through the heat transfer member 7 attached to the semiconductor light receiving element 10 and enters the semiconductor light receiving element 10, and some of the heat from the semiconductor light receiving element 10 is transferred to the base 3 via the heat transfer member 7. Therefore, the heat from the semiconductor light receiving element 10 is transferred to the base 3 not only from the first surface 11a on which the photodiode 12 is formed, but also from the second surface 11b via the heat transfer member 7. This promotes heat dissipation from the semiconductor light receiving element 10, reducing temperature rise and suppressing a decrease in the output of the optical power feeding converter 1.

[0045] When the leg portions 7b fixed to the base 3 are formed integrally with the heat transfer member 7, the only interface at which heat transfer is generally difficult is the interface between the leg portions 7b and the base 3, making it possible to easily transfer heat to the base 3. On the other hand, when the support portions 3c to which the heat transfer member 7 is fixed are formed integrally with the base 3, the only interface at which heat transfer is difficult is the interface between the heat transfer member 7 and the support portions 3c, making it possible to easily transfer heat to the base 3. Furthermore, when the heat transfer member 7 is fixed to the base 3 via spacer members 8 made of a material with excellent thermal conductivity, it is possible to easily transfer heat to the base 3 and also to easily form the heat transfer member 7 and the base 3.

[0046] To increase the output voltage, the photodiode 12 is formed by serially connecting multiple segments equally divided by multiple grooves 13 extending radially from its center C. The illumination area of ​​the input light L1 from the optical fiber cable OC is circular, and its light intensity distribution is rotationally symmetric about the optical axis OA, with the light intensity decreasing with increasing distance from the optical axis OA. Therefore, to ensure uniform illumination of the multiple segments, the input light L1 is input so that its optical axis OA passes through the center C of the photodiode 12. Because grooves 13 that cannot be photoelectrically converted are concentrated near the center C of the photodiode 12, the high-intensity portion of the input light L1 near the optical axis OA is not photoelectrically converted, resulting in significant waste. However, if a conical concave surface 7d is formed in the area illuminated by the input light L1 on the heat transfer member 7, the circular illumination area of ​​the input light L1 incident on this concave surface 7d is converted into an annular shape before entering the photodiode 12. Therefore, the portion of the input light L1 with high light intensity is made incident on the photodiode 12, avoiding the vicinity of the center C of the photodiode 12 where the grooves 13 are concentrated, and the input light L1 can be used effectively.

[0047] The substrate 4 may be a silicon substrate having an insulating layer and a wiring portion 4a on the insulating layer. Alternatively, the wiring portion 4a of the substrate 4 may be formed on the insulating layer of the base 3, and the substrate 4 may be omitted and the semiconductor light receiving element 10 may be fixed to the base 3 to promote heat dissipation. In addition, those skilled in the art may implement the present invention in various forms by adding various modifications to the above embodiment without departing from the spirit of the present invention, and the present invention also includes such modifications. [Explanation of symbols]

[0048] 1: Optical power converter 2a, 2b: Output terminal section 3: Base 3c: Support part 4: Substrate 4a: Wiring section 5: Cover 5a: opening 6a, 6b: Conductive wire 7: Heat transfer material 7a: Main body 7b,7c: Legs 7d: concave 8: Spacer member 10: Semiconductor photodetector 11: Semiconductor substrate 11a: Front page 11b:Second side 12: Photodiode 13: Groove 14: 1st electrode 15: 2nd electrode 16: First semiconductor layer 17: Light absorbing layer 18: Second semiconductor layer 19: Insulating layer 20: Solder paste L1: Input light OA: optical axis OC: Optical fiber cable

Claims

1. An optical power supply converter having a semiconductor light receiving element that photoelectrically converts input light input through an optical fiber cable, and a base for fixing the semiconductor light receiving element, the semiconductor light receiving element includes a photodiode on a first surface side of a semiconductor substrate transparent to the input light, and the first surface side is fixed to the base; a heat transfer member that is transparent to the input light and is in close contact with a second surface side of the semiconductor substrate that faces the first surface, the heat transfer member being fixed to a support portion that is integrally formed with the base so as to extend toward the heat transfer member; An optical power supply converter characterized in that the input light is configured to pass through the heat transfer member and be incident on the semiconductor light receiving element, and a portion of the heat of the semiconductor light receiving element is configured to be transferred to the base via the heat transfer member.

2. An optical power supply converter having a semiconductor light receiving element that photoelectrically converts input light input via an optical fiber cable, and a base for fixing the semiconductor light receiving element, the semiconductor light receiving element includes a photodiode on a first surface side of a semiconductor substrate transparent to the input light, and the first surface side is fixed to the base; a heat transfer member that is transparent to the input light and is in close contact with a second surface side of the semiconductor substrate that faces the first surface, and is fixed to the base via a spacer member; An optical power supply converter characterized in that the input light is configured to pass through the heat transfer member and be incident on the semiconductor light receiving element, and a portion of the heat of the semiconductor light receiving element is configured to be transferred to the base via the heat transfer member.

3. The photodiode is formed by connecting a plurality of segments in series, the segments being equally divided by grooves extending radially from a center through which an optical axis of the input light passes in a direction perpendicular to the optical axis, The optical power supply converter according to claim 1 or 2, characterized in that the heat transfer member has a conical concave surface formed in an area where the input light is irradiated on the opposite side of the contact surface that is in close contact with the second surface side of the semiconductor substrate, with its axis of symmetry coinciding with the optical axis.

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