WO2023248372A1 - Optical power feed converter - Google Patents

Optical power feed converter Download PDF

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Publication number
WO2023248372A1
WO2023248372A1 PCT/JP2022/024829 JP2022024829W WO2023248372A1 WO 2023248372 A1 WO2023248372 A1 WO 2023248372A1 JP 2022024829 W JP2022024829 W JP 2022024829W WO 2023248372 A1 WO2023248372 A1 WO 2023248372A1
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WIPO (PCT)
Prior art keywords
light
light receiving
circular
conical recess
circular light
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PCT/JP2022/024829
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French (fr)
Japanese (ja)
Inventor
尚友 磯村
悦司 大村
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株式会社京都セミコンダクター
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Application filed by 株式会社京都セミコンダクター filed Critical 株式会社京都セミコンダクター
Priority to JP2022560213A priority Critical patent/JP7178154B1/en
Priority to PCT/JP2022/024829 priority patent/WO2023248372A1/en
Publication of WO2023248372A1 publication Critical patent/WO2023248372A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0232—Optical elements or arrangements associated with the device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/30—Circuit arrangements or systems for wireless supply or distribution of electric power using light, e.g. lasers

Definitions

  • the present invention relates to an optical power supply converter that converts light input through an optical fiber cable into electric power and supplies the converted electric power.
  • optical power supply converters are used that receive light transmitted to electronic devices via optical fiber cables, generate photocurrent through photoelectric conversion, and supply power.
  • the optical power supply converter has a semiconductor light receiving element for photoelectric conversion.
  • the output voltage of this semiconductor photodetector is usually less than 1V.
  • an optical power supply converter with a high output voltage is used.
  • Patent Document 1 it is possible to increase the output voltage by dividing the circular light-receiving portion of a semiconductor light-receiving element into a plurality of fan-shaped photodiodes by an isolation groove and connecting these in series.
  • the output voltage of a semiconductor light-receiving element composed of a plurality of divided photodiodes connected in series increases as the number of photodiodes increases.
  • the output current is smaller than when it is not divided, and becomes smaller as the number of divisions increases.
  • this output current is limited by the photodiode with the least photocurrent generated by photoelectric conversion. Therefore, in order to make the photocurrents of the plurality of photodiodes equal to each other, the circular light receiving section is equally divided so that the plurality of photodiodes have the same shape and the same area.
  • Patent Document 1 in order to divide the circular light receiving part into the same shape and area, a plurality of linear isolation grooves with a constant width are formed radially in the radial direction from the center of the circular light receiving part. A plurality of isolation grooves are concentrated near the center of the circular light receiving section. The larger the number of divisions of the circular light-receiving section, that is, the more isolation grooves there are, the closer the adjacent isolation grooves are, and the more isolation grooves are formed in the width direction (circumferential direction) at positions farther from the center of the circular light-receiving section. It becomes connected.
  • the plurality of isolation grooves are continuous in the circumferential direction, and a regular polygonal region having one side equal to the width of the isolation groove is formed near the center of the circular light receiving section. Since photoelectric conversion cannot be performed in the isolation groove, this regular polygonal region is an ineffective region in which no photocurrent can be generated. This invalid area becomes larger as the number of divisions of the circular light receiving section increases.
  • the light intensity distribution of the incident light input through the optical fiber cable is generally a Gaussian distribution, and the light intensity decreases as the distance from the optical axis increases. This is the light intensity distribution.
  • the optical axis of the light is perpendicular to the circular light-receiving section and passes through the center of the circular light-receiving section. is incident.
  • the part of the incident light with high light intensity near the optical axis is irradiated onto the ineffective area formed near the center of the circular light-receiving section, and is not converted into photocurrent and is wasted, so the output of the optical power supply converter must be increased. Can not do it.
  • the present invention reduces wasted light among the light that is input via an optical fiber cable to a semiconductor light receiving element in which a circular light receiving part is divided radially into equal parts with respect to the center and connected in series.
  • the object of the present invention is to provide an optical power feeding converter that can make the light incident evenly.
  • the optical power feeding converter according to the invention according to claim 1 is an optical power feeding converter that converts light input via an optical fiber cable into a photocurrent by a semiconductor light receiving element and outputs the photocurrent, wherein the semiconductor light receiving element is a first one of a semiconductor substrate.
  • a back-illuminated light-receiving element that allows light to enter the circular light-receiving portion from a second surface side of the semiconductor substrate opposite to the first surface of the circular light-receiving portion formed on the surface side to generate a photocurrent.
  • the circular light-receiving section is divided into a plurality of linear isolation grooves extending from the center of the circular light-receiving section so that the light-receiving areas are equal to each other, and connected in series by a plurality of conductive members.
  • a conical recess formed by recessing the semiconductor substrate into a conical shape whose diameter decreases toward the first surface is provided on the second surface side of the semiconductor substrate, and the symmetry axis of the conical recess is is formed to pass through the center of the circular light-receiving section, and the light incident from the second surface side is converted into an annular shape by the conical recess, and the light is equal to each of the plurality of photodiodes of the circular light-receiving section. It is characterized by being configured such that the amount of light is incident.
  • the light input through the optical fiber cable is converted into an annular shape by the conical recess and is incident equally on the plurality of photodiodes, thereby reducing variations in the output of the plurality of photodiodes. be able to.
  • the photocurrent of the semiconductor light-receiving element having a circular light-receiving section formed by connecting a plurality of photodiodes in series can be increased, and the power supplied by the optical power supply converter can be increased.
  • the optical power feeding converter of the invention of claim 2 is the invention of claim 1, further comprising a collimator lens that converts the light input through the optical fiber cable into parallel light and makes it enter the conical recess. It is a feature. According to the above configuration, since the light traveling in a conical shape is converted into parallel light by the collimator lens, the angle of incidence on the conical recess can be made constant. Therefore, it is easy to set the distance between the optical fiber cable and the collimator lens so that the input light does not protrude from the circular light receiving part, so that the beam diameter of the parallel light matches the diameter of the circular light receiving part. can. Therefore, all of the input light can be made incident on the circular light receiving section, the photocurrent of the semiconductor light receiving element can be increased, and the power supplied by the optical power supply converter can be increased.
  • the conical recess allows the light incident on the conical recess to have an outer diameter equal to or less than a diameter of the circular light receiving part, and a plurality of The linear isolation groove is formed so as to be converted into an annular shape having an inner diameter larger than an outer diameter of an ineffective area formed continuously in the circumferential direction of the circular light receiving section.
  • the circular light receiving part is radially divided into equal parts with respect to the center thereof, and the semiconductor light receiving element connected in series is wasted among the light inputted through the optical fiber cable. It is possible to reduce the amount of light and make it evenly incident.
  • FIG. 1 is a perspective view of an optical power supply converter according to Example 1 of the present invention.
  • FIG. 2 is an explanatory diagram of light incident on a semiconductor light-receiving element included in the optical power feeding converter of FIG. 1.
  • FIG. 3 is a plan view showing a circular light-receiving portion of the semiconductor light-receiving element of FIG. 2;
  • FIG. 4 is a sectional view taken along the line IV-IV of the semiconductor light receiving element of FIG. 3 fixed to a base.
  • FIG. 2 is a light intensity distribution diagram of light input via an optical fiber cable.
  • FIG. 4 is an explanatory diagram of light incident on a semiconductor light receiving element and converted into an annular shape in a cross section taken along line VI-VI in FIG.
  • FIG. 7 is a graph showing the inner diameter of annular light in contour lines using the angle of incidence of parallel light on the conical surface of the conical recess and the distance from the apex of the conical recess to the center of the circular light receiving section as parameters.
  • FIG. 7 is an explanatory diagram of another example of light that enters a semiconductor light receiving element and is converted into an annular shape.
  • FIG. 3 is an explanatory diagram of an etching mask for forming a conical recess. It is an explanatory view of forming a conical recess by etching.
  • FIG. 7 is an explanatory diagram of light incident on the semiconductor light receiving element of the optical power supply converter according to Example 2 of the present invention and converted into an annular shape.
  • FIG. 7 is an explanatory diagram of another example of light that enters the semiconductor light receiving element of the optical power feeding converter according to the second embodiment and is converted into an annular shape.
  • the optical power supply converter 1 is a converter for converting light (incident light L1) input via a single mode optical fiber cable OC into a photocurrent and supplying power to the outside. It has a pair of output terminal parts 2a and 2b.
  • the base 3 equipped with a pair of output terminals 2a and 2b includes a semiconductor light receiving element 10 for generating a photocurrent by photoelectric conversion from received light, and a semiconductor light receiving element 10 for protecting and shielding the semiconductor light receiving element 10. covers 5 are fixed respectively.
  • the semiconductor light receiving element 10 is connected to corresponding output terminal parts 2a and 2b via wiring parts 3a and 3b in order to output the generated photocurrent.
  • the incident light L1 input via the optical fiber cable OC is infrared light with a wavelength of, for example, about 1.5 ⁇ m. After the incident light L1 is emitted from the output end E of the optical fiber cable OC, it is a conical beam whose irradiation range becomes wider as it advances.
  • the cover 5 has a collimator lens 6 made of optical glass with a refractive index of 1.45, for example, as an optical system through which the incident light L1 passes.
  • the collimator lens 6 converts the incident light L1 into parallel light L2, and makes the parallel light L2 enter the semiconductor light receiving element 10.
  • the semiconductor light-receiving element 10 is a back-illuminated light-receiving element that has a circular light-receiving section 12 that performs photoelectric conversion and receives light from the side opposite to the side on which the circular light-receiving section 12 is formed.
  • the cover 5 is fixed to the base 3 so that the optical axis 6a of the collimator lens 6 is perpendicular to the circular light receiving section 12 of the semiconductor light receiving element 10 and passes through the center C of the circular light receiving section 12.
  • the optical fiber cable OC is inserted into the insertion hole 5a of the cover 5 and fixed so that its output end E is spaced a predetermined distance from the collimator lens 6. At this time, the output end E is positioned so that the optical axis OA of the incident light L1 coincides with the optical axis 6a of the collimator lens 6.
  • the circular light-receiving section 12 is formed by a plurality of straight isolation grooves 13 extending radially from the center C of the circular PIN-type photodiode provided with a light absorption layer, for example. It is equally divided into a plurality of fan-shaped photodiodes 14 having the same area.
  • the circular light receiving section 12 is equally divided into 30 photodiodes 14 by 30 isolation grooves 13.
  • the plurality of linear isolation grooves 13 are formed radially with a constant width from the center C of the circular light receiving section 12 so as to form a plurality of fan-shaped photodiodes 14 having the same shape and light receiving area. Further, an annular isolation groove 15 is formed along the outer periphery of the circular light receiving portion 12, and a plurality of linear isolation grooves 13 are connected by the annular isolation groove 15. A plurality of photodiodes 14 electrically separated by a plurality of isolation grooves 13 are connected in series by a conductive member 4 formed on the base 3, thereby forming a circular light receiving section 12. The diameter of this circular light receiving portion 12 is assumed to be D1.
  • a plurality of sector-shaped photodiodes 14 having the same shape and light-receiving area are formed in the circular light-receiving section 12 so as to surround the center C. Since the isolation groove 13 cannot generate a photocurrent, it is preferable to form the isolation groove 13 with a small width and a straight line so that the area occupied by the isolation groove 13 in the area of the circular light receiving section 12 is reduced. In FIG. 3, some of the symbols of the isolation groove 13 and the photodiode 14 are omitted.
  • a plurality of linear isolation grooves 13 are concentrated near the center C of the circular light receiving section 12. Therefore, adjacent isolation grooves 13 are closer toward the center C, and a plurality of isolation grooves 13 are connected in the width direction at positions spaced apart from the center C. As a result, the plurality of isolation grooves 13 are continuous in the circumferential direction of the circular light receiving portion 12, and a regular polygonal region having one side equal to the width of the isolation groove 13 is formed near the center C. Since photoelectric conversion cannot be performed in the isolation groove 13, this regular polygonal region is an ineffective region I in which no photocurrent can be generated. The invalid area I becomes larger as the number of divisions of the circular light receiving section 12 increases. The outer diameter of this invalid area I is assumed to be D2.
  • the photodiode 14 includes an n-type semiconductor layer 21, a light absorption layer 22, and a p-type semiconductor layer 23, which are stacked on the first surface 20a of a semi-insulating semiconductor substrate 20.
  • the semiconductor substrate 20 is, for example, an InP substrate
  • the n-type semiconductor layer 21 is, for example, an n-InP layer
  • the light absorption layer 22 is, for example, an InGaAs layer
  • the p-type semiconductor layer 23 is, for example, a p-InP layer. It is not limited to this.
  • the photodiode 14 is not limited to the PIN type. Note that the thicknesses of the n-type semiconductor layer 21, the light absorption layer 22, and the p-type semiconductor layer 23 can be set as appropriate, and are often formed to a thickness of about 0.5 to 10 ⁇ m.
  • the isolation grooves 13 and 15 are created by etching the semiconductor substrate 20, in which the n-type semiconductor layer 21, the light absorption layer 22, and the p-type semiconductor layer 23 are stacked, from the p-type semiconductor layer 23 side so that the semiconductor substrate 20 is exposed. formed by Thereby, the circular light receiving section 12 is divided into a plurality of electrically isolated photodiodes 14.
  • the isolation grooves 13 and 15 may have sidewalls formed in an inclined shape, for example, so that the width becomes narrower toward the semiconductor substrate 20 side.
  • the plurality of photodiodes 14 each have a connection hole 17 that penetrates the p-type semiconductor layer 23 and the light absorption layer 22 and reaches the n-type semiconductor layer 21.
  • An insulating protective film 24 is formed to cover the surfaces of the plurality of photodiodes 14 and the side walls of the connection holes 17 of these photodiodes 14.
  • the protective film 24 covers the inner walls and bottoms of the plurality of linear isolation grooves 13 and the annular isolation groove 15.
  • Each photodiode 14 has an anode electrode 27 connected to the p-type semiconductor layer 23 exposed by partially removing the protective film 24 on the p-type semiconductor layer 23, and a protective film 24 at the bottom of the connection hole 17 removed.
  • a cathode electrode 28 is connected to the exposed n-type semiconductor layer 21.
  • the anode electrode 27 and the cathode electrode 28 are formed by selectively depositing a metal laminated film using, for example, a lift-off method.
  • the metal laminated film is composed of an adhesion layer such as titanium or chromium, and a low resistivity layer such as gold, silver, or aluminum.
  • One anode electrode 27 and the other cathode electrode 28 of the adjacent photodiodes 14 are connected by the conductive member 4 of the base 3 via the conductive paste 8, so that the plurality of circular light receiving parts 12 photodiodes 14 are connected in series.
  • a plurality of photodiodes 14 may be connected in series using, for example, a conductive wire mainly composed of gold, and the photodiodes 14 may be selectively formed on the protective film 24.
  • a plurality of photodiodes 14 may be connected in series by a plurality of wiring lines.
  • the optical power supply converter 1 which includes this semiconductor light receiving element 10 and supplies power by photoelectrically converting the incident light L1 inputted through the optical fiber cable OC, can supply power at a high voltage.
  • the incident light L1 emitted from the output end E of the optical fiber cable OC travels while expanding into a conical shape with an apex angle ⁇ (full angle) of 14°, for example.
  • the light intensity distribution of this incident light L1 becomes a Gaussian distribution on the plane P perpendicular to the optical axis OA, and the light intensity decreases as the distance from the optical axis OA increases, and the light intensity distribution is rotationally symmetrical with respect to the optical axis OA. become.
  • the outermost periphery of the incident light L1 is defined as the point where the light intensity becomes 1/e 2 of the light intensity on the optical axis OA.
  • the optical axis OA of the incident light L1 is made to coincide with the optical axis 6a of the collimator lens 6.
  • the collimator lens 6 converts the incident light L1 into parallel light L2, and makes the parallel light L2 enter the back-illuminated semiconductor light receiving element 10.
  • the light intensity distribution of the parallel light L2 is maintained as the light intensity distribution when the incident light L1 enters the collimator lens 6.
  • the semiconductor light-receiving element 10 has a diameter decreasing toward the second surface 20b (back surface side) of the semiconductor substrate 20 opposite to the first surface 20a of the semiconductor substrate 20 on which the circular light-receiving portion 12 is formed.
  • a conical recess 16 is formed by recessing the semiconductor substrate 20 into a conical shape.
  • the conical recess 16 is formed such that an extension line (axis of symmetry) of the axis of symmetry 16a of the conical recess 16 is perpendicular to the circular light receiving section 12 and passes through the center C of the circular light receiving section 12.
  • the optical axis 6a of the collimator lens 6 is aligned so as to pass through the center C of the circular light receiving section 12, and thus coincides with the axis of symmetry of the conical recess 16. Since the optical axis OA of the incident light L1 is made to coincide with the optical axis 6a of the collimator lens 6, the optical axis OA becomes the optical axis of the parallel light L2, and the optical axis OA coincides with the axis of symmetry of the conical recess 16. .
  • the parallel light L2 incident on the conical surface 16b of the conical recess 16 is refracted away from the optical axis OA and converted into annular light L3.
  • Db be the beam diameter of the parallel light L2 converted by the collimator lens 6.
  • the outer diameter of the annular light L3 incident on the circular light receiving portion 12 spaced apart by a distance T from the apex of the conical recess 16 is Do, and the inner diameter is Di.
  • the inner diameter Di and outer diameter Do of the annular light L3 are expressed by the following equations (3) and (4).
  • Di 2 ⁇ T ⁇ tan( ⁇ - ⁇ )...(3)
  • Do Di+2 ⁇ t...(4)
  • the inner diameter Di of the annular light L3 is shown in contour lines using the incident angle ⁇ and the distance T as parameters. If the incident angle ⁇ is constant, the larger the distance T, the larger the inner diameter Di. On the other hand, if the distance T is constant, the inner diameter Di increases as the incident angle ⁇ increases. Although it depends on the type of semiconductor substrate, the thickness of the semiconductor substrate 20 is usually about 700 ⁇ m, and the distance T cannot be made greater than the thickness of the semiconductor substrate 20.
  • the inner diameter Di of the annular light L3 is set larger than the outer diameter D2 of the ineffective area I in order to reduce wasted light input due to light entering the ineffective area I near the center C of the circular light receiving section 12.
  • the width of the isolation groove 13 is 10 ⁇ m and the number of photodiodes 14 is 30, the ineffective region I is a regular tridecagon with a side of 10 ⁇ m, so the length of the outer circumference is 300 ⁇ m, and the outer diameter D2 of the ineffective region I is It is less than 100 ⁇ m.
  • the incident angle ⁇ is 20° and the distance T is 470 ⁇ m from FIG. 7, the shape and size of the conical recess 16 are determined, and the output angle ⁇ is 6. It becomes 1°.
  • the diameter of the conical recess 16 on the second surface 20b of the semiconductor substrate 20 is 1264 ⁇ m, and the depth of the conical recess 16 is 230 ⁇ m.
  • the outer diameter Do of the annular light L3 is set to 1200 ⁇ m so that the entire parallel light L2 enters the circular light receiving portion 12 having a diameter D1 of, for example, 1200 ⁇ m through the conical recess 16, the beam diameter Db of the parallel light L2 is becomes 1108 ⁇ m. Then, the distance between the collimator lens 6 and the output end E of the optical fiber cable OC is determined to be 4513 ⁇ m as the predetermined distance.
  • the distance between the collimator lens 6 and the output end E of the optical fiber cable OC is adjusted so that the beam diameter Db of the parallel light L2 is small.
  • the optical power feeding converter 1 can be made smaller. Even if the distance between the collimator lens 6 and the output end E of the optical fiber cable OC is reduced, the inner diameter Di of the annular light L3 does not change.
  • the distance between the collimator lens 6 and the semiconductor light receiving element 10 can be set arbitrarily, the smaller the distance, the more advantageous it is to downsizing the optical power feeding converter 1.
  • a portion of the parallel light L2 near the optical axis is made incident on the circular light receiving portion 12 through the conical recess 16, and the remaining portion of the parallel light L2 is transmitted as parallel light without passing through the conical recess 16.
  • the light may be directly incident on the circular light receiving section 12.
  • the annular light L3, in which light that spreads in the radial direction and parallel light coexist enters the circular light receiving section 12.
  • At least a part of the parallel light L2 that would be incident on the invalid area I if it is parallel light is changed in its traveling direction by the conical recess 16, thereby avoiding the invalid area I and making it equally incident on the circular light receiving part 12. It would be good if you could.
  • the incident angle ⁇ and the distance T can be set by setting the inner diameter Di of the light that enters the conical recess 16 and becomes annular.
  • the distance T is 480 ⁇ m, which determines the shape and size of the conical recess 16, and the output angle ⁇ is 9°.
  • the diameter of the conical recess 16 on the second surface 20b is 762 ⁇ m, and the depth is 220 ⁇ m.
  • the outer diameter Do of the light that enters the conical recess 16 and becomes annular is 1081 ⁇ m.
  • the beam diameter Db of the parallel light L2 can be arbitrarily set within a range that is larger than the diameter of the conical recess 16 and less than or equal to the diameter D1 of the circular light receiving section 12.
  • the inner diameter of the annular light L3 in the circular light receiving part 12 is either the inner diameter Di of the light that enters the conical recess 16 and becomes annular or the diameter of the conical recess 16, depending on the shape and size of the conical recess 16. Decided on one side.
  • the outer diameter of the annular light L3 at the circular light receiving part 12 depends on the shape and size of the conical recess 16, and the beam diameter Db of the parallel light L2 or the outer diameter of the light that enters the conical recess 16 and becomes annular.
  • the diameter is determined by either one of the diameters Do.
  • an etching mask layer 30 having a conical recess 30a is formed on the second surface 20b of the semiconductor substrate 20.
  • the conical recess 30a has an axis of symmetry 30b.
  • the etching mask layer 30 is a photoresist whose thickness is continuously changed depending on, for example, a difference in exposure amount, thereby making a recess into a conical shape.
  • the thinner portions of the etching mask layer 30 are etched more deeply to form conical recesses 16 that reflect the shape of the etching mask layer 30.
  • a conical recess is formed in which the axis of symmetry 16a is aligned with the center C of the circular light receiving section 12. 16 is formed.
  • the conical recess 16 may be formed by grinding and polishing the semiconductor substrate 20 into a conical shape using a grindstone or the like. Further, the conical recess 16 is formed on the second surface side 20b after the circular light receiving section 12 is formed on the first surface side 20a of the semiconductor substrate 20.
  • a circular light receiving portion 12 may be formed in which C is aligned.
  • the semiconductor light-receiving element 10 receives incident light L1 emitted from the output end E of the optical fiber cable OC and spread into a conical shape with an apex angle ⁇ . In order to prevent light from entering the ineffective area I formed near the center C of the circular light receiving section 12, the incident light L1 is converted into an annular light L3' by the conical recess 16 in the same way as described above, and the circular light receiving section 12.
  • the shape and size of the conical recess 16 are determined by setting the inner diameter Di, incident angle ⁇ , and distance T of the annular light L3' with respect to the light on the optical axis OA in the same manner as described above. For example, if the inner diameter Di is 150 ⁇ m and the incident angle ⁇ is 24°, the output angle ⁇ is 7.3°, and from FIG. become.
  • the distance between the output end E and the semiconductor light receiving element 10 can be set so that all of the incident light L1 enters the circular light receiving section 12 through the conical recess 16.
  • the angle of incidence of the incident light L1 on the conical surface 16b becomes smaller as the distance from the optical axis OA increases, and the angle of incidence of the outermost portion of the incident light L1 on the conical surface 16b is ⁇ -( ⁇ /2). Further, the output angle ⁇ is smaller than the output angle ⁇ of the light on the optical axis OA. Then, the distance between the output end E and the semiconductor light receiving element 10 at which the outer diameter Do of the annular light L3' is equal to or less than the diameter D1 of the circular light receiving portion 12 is set as a predetermined distance.
  • the distance between the output end E and the semiconductor light receiving element 10 is at most 2195 ⁇ m.
  • the incident light L1 whose beam diameter is equal to the diameter D1 of the conical recess 16 enters the conical recess 16, and the outer diameter Do of the annular light L3' becomes 701 ⁇ m.
  • the outer diameter Do is larger than the diameter D1 of the circular light receiving portion 12, the distance between the output end E and the semiconductor light receiving element 10 is reduced to reduce the beam diameter of the incident light L1 to the conical recess 16. Accordingly, all of the incident light L1 can be made to enter the circular light receiving section 12 while avoiding the ineffective area I.
  • the outer diameter Do of the annular light L3' may be less than or equal to the diameter D1 of the circular light receiving section 12. Even if the distance between the emission end E and the semiconductor light receiving element 10 is changed, the inner diameter Di of the annular light L3' does not change.
  • a portion of the incident light L1 near the optical axis OA enters the circular light receiving portion 12 via the conical recess 16, and the remaining outer peripheral portion of the incident light L1 enters the circular light receiving portion 12 via the conical recess 16.
  • the light may be incident on the circular light receiving section 12 without being exposed.
  • the annular light L ⁇ b>3 ′ in which light that spreads in different ways in the radial direction is mixed, enters the circular light receiving section 12 .
  • the incident light L1 that is incident on the ineffective area I can be made to avoid the ineffective area I and be made equally incident on the circular light receiving section 12 by changing the traveling direction by the conical recess 16.
  • Incident light L1 input to the optical power supply converter 1 via the optical fiber cable OC is converted into annular lights L3 and L3' by the conical recess 16 formed in the semiconductor light receiving element 10, and the circular light receiving part 12
  • An equal amount of light enters the plurality of equally divided photodiodes 14. Therefore, variations in the outputs of the plurality of photodiodes 14 can be reduced.
  • the annular lights L3 and L3' do not enter the vicinity of the center C of the circular light receiving section 12 where the plurality of isolation grooves 13 that do not generate photocurrent are concentrated, the photoelectric conversion of the incident light L1 It can reduce the amount of light that is wasted. Therefore, the photocurrent of the semiconductor light receiving element 10 having the circular light receiving section 12 formed by connecting a plurality of photodiodes 14 in series can be increased, and the power supplied by the optical power supply converter 1 can be increased. .
  • the angle of incidence ⁇ into the conical recess 16 can be made constant. Therefore, in order to prevent the input incident light L1 from protruding from the circular light receiving section 12, the output end E of the optical fiber cable OC and the collimator lens are arranged so that the beam diameter Db of the parallel light L2 matches the diameter D1 of the circular light receiving section 12. 6 can be easily set. Therefore, all of the input incident light L1 can be made incident on the circular light receiving section 12, the photocurrent of the semiconductor light receiving element 10 can be increased, and the power supplied by the optical power supply converter 1 can be increased.
  • the conical recess 16 allows the light incident on the conical surface 16b to pass through an outer diameter Do that is less than or equal to the diameter D1 of the circular light receiving section 12 and an inner diameter Di that is larger than the outer diameter D2 of the invalid area I of the circular light receiving section 12. It is converted into annular lights L3 and L3' having the following characteristics.
  • the annular lights L3 and L3' all enter the circular light receiving section 12, avoiding an ineffective region I formed near the center C of the circular light receiving section 12 where no photocurrent can be generated. Therefore, the incident light L1 inputted through the optical fiber cable OC can be utilized without wastage, and the power supplied by the optical power supply converter 1 can be increased.

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  • Light Receiving Elements (AREA)

Abstract

[Problem] To provide an optical power feed converter that can reduce wasted light in the light input through an optical fiber cable to semiconductor light-receiving elements, which are obtained by dividing a circular light-receiving portion into equal portions radially with respect to center thereof and which are connected in series, and that can ensure even incidence. [Solution] An optical power feed converter (1) converts light (L1) input through an optical fiber cable into a photocurrent using a semiconductor light-receiving element (10) and outputs the photocurrent, wherein light enters the semiconductor light-receiving element (10) from a second surface (20b) side of a semiconductor substrate (20), which is the back surface with respect to a circular light-receiving portion (12) on a first surface (20a) side, the circular light-receiving portion (12) includes a plurality of photodiodes (14) that are equally divided by a plurality of linear isolation grooves (13) extending from the center (C) of the circular light-receiving portion and that are connected in series, and a conical recess (16) that decreases in diameter toward the first surface (20a) side is formed correspondingly to the circular light-receiving portion (12) at the second surface (20b) side of the semiconductor substrate (20) and configured so that the incident light is converted into an annular shape at the conical recess (16) and falls with equal light quantity on each of the plurality of photodiodes (14).

Description

光給電コンバータoptical power converter
　本発明は、光ファイバケーブルを介して入力される光を電力に変換して給電する光給電コンバータに関する。 The present invention relates to an optical power supply converter that converts light input through an optical fiber cable into electric power and supplies the converted electric power.
　給電設備がない遠隔地、給電による微弱な電磁界がノイズとなる環境、防爆を必要とする環境、電気的相互影響がある超高電圧設備内等、特殊な環境では電源ケーブルを介して電子機器類を作動させる電力を供給できない場合がある。そのため、電子機器類の傍まで光ファイバケーブルを介して送られる光を受けて、光電変換によって光電流を生成して給電する光給電コンバータが利用されている。 In special environments, such as remote locations without power supply equipment, environments where weak electromagnetic fields from power supply cause noise, environments that require explosion protection, and inside ultra-high voltage equipment where electrical interactions occur, electronic devices may be connected via power cables. In some cases, it may not be possible to supply power to operate the equipment. For this reason, optical power supply converters are used that receive light transmitted to electronic devices via optical fiber cables, generate photocurrent through photoelectric conversion, and supply power.
　光給電コンバータは光電変換用の半導体受光素子を有する。この半導体受光素子の出力電圧は、通常１Ｖ未満である。光給電コンバータからの給電を受ける機器が高い入力電圧を必要とする場合には、出力電圧を高くした光給電コンバータが利用される。例えば特許文献１のように、半導体受光素子の円形受光部をアイソレーション溝によって複数の扇形のフォトダイオードに分割し、これらを直列に接続することによって出力電圧を高くすることが可能である。 The optical power supply converter has a semiconductor light receiving element for photoelectric conversion. The output voltage of this semiconductor photodetector 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 high output voltage is used. For example, as in Patent Document 1, it is possible to increase the output voltage by dividing the circular light-receiving portion of a semiconductor light-receiving element into a plurality of fan-shaped photodiodes by an isolation groove and connecting these in series.
　分割されて直列に接続された複数のフォトダイオードによって構成された半導体受光素子の出力電圧は、フォトダイオードが多いほど高くなる。一方、その出力電流は、分割されない場合よりも小さくなり、分割数が多いほど小さくなる。その上、この出力電流は、光電変換により生成される光電流が最小のフォトダイオードによって制限される。それ故、複数のフォトダイオードの光電流を互いに等しくするために、これら複数のフォトダイオードが同形状且つ同面積となるように円形受光部が等分される。 The output voltage of a semiconductor light-receiving element composed of a plurality of divided photodiodes connected in series increases as the number of photodiodes increases. On the other hand, the output current is smaller than when it is not divided, and becomes smaller as the number of divisions increases. Moreover, this output current is limited by the photodiode with the least photocurrent generated by photoelectric conversion. Therefore, in order to make the photocurrents of the plurality of photodiodes equal to each other, the circular light receiving section is equally divided so that the plurality of photodiodes have the same shape and the same area.
米国特許第５３４２４５１号明細書US Patent No. 5,342,451
　特許文献１では、円形受光部を同形状且つ同面積で分割するために、一定幅の直線状の複数のアイソレーション溝が、円形受光部の中心から径方向に放射状に形成されているので、複数のアイソレーション溝が円形受光部の中心近傍に集中する。そして、円形受光部の分割数が多いほど、即ちアイソレーション溝が多いほど隣り合うアイソレーション溝が近づき、円形受光部の中心から離隔した位置で複数のアイソレーション溝が幅方向（周方向）に連なるようになる。 In Patent Document 1, in order to divide the circular light receiving part into the same shape and area, a plurality of linear isolation grooves with a constant width are formed radially in the radial direction from the center of the circular light receiving part. A plurality of isolation grooves are concentrated near the center of the circular light receiving section. The larger the number of divisions of the circular light-receiving section, that is, the more isolation grooves there are, the closer the adjacent isolation grooves are, and the more isolation grooves are formed in the width direction (circumferential direction) at positions farther from the center of the circular light-receiving section. It becomes connected.
　こうして、複数のアイソレーション溝が周方向に連なって、円形受光部の中心近傍にアイソレーション溝の幅を一辺とする正多角形状の領域が形成される。アイソレーション溝では光電変換をすることができないので、この正多角形状の領域は光電流を生成できない無効領域である。この無効領域は、円形受光部の分割数が多いほど大きくなる。 In this way, the plurality of isolation grooves are continuous in the circumferential direction, and a regular polygonal region having one side equal to the width of the isolation groove is formed near the center of the circular light receiving section. Since photoelectric conversion cannot be performed in the isolation groove, this regular polygonal region is an ineffective region in which no photocurrent can be generated. This invalid area becomes larger as the number of divisions of the circular light receiving section increases.
　ここで、光ファイバケーブルを介して入力される入射光の光強度分布は、一般的にはガウス分布であり、光軸から離隔するほど光強度が低下すると共に、光軸に対して回転対称状の光強度分布である。この光を、同形状且つ同面積となるように等分された円形受光部に均等に入射させるために、光軸が円形受光部に対して垂直にこの円形受光部の中心を通るように光を入射させる。 Here, the light intensity distribution of the incident light input through the optical fiber cable is generally a Gaussian distribution, and the light intensity decreases as the distance from the optical axis increases. This is the light intensity distribution. In order to make this light evenly enter the circular light-receiving section that is divided into equal parts with the same shape and area, the optical axis of the light is perpendicular to the circular light-receiving section and passes through the center of the circular light-receiving section. is incident.
　しかし、入射光の光軸近傍の光強度が高い部分が、円形受光部の中心近傍に形成された無効領域に照射され、光電流に変換されず無駄になるので、光給電コンバータの出力を大きくすることができない。 However, the part of the incident light with high light intensity near the optical axis is irradiated onto the ineffective area formed near the center of the circular light-receiving section, and is not converted into photocurrent and is wasted, so the output of the optical power supply converter must be increased. Can not do it.
　そこで、本発明は、円形受光部がその中心に対して放射状に等分されて直列に接続された半導体受光素子に、光ファイバケーブルを介して入力される光のうち、無駄になる光を減少させて均等に入射させることができる光給電コンバータを提供することを目的としている。 Therefore, the present invention reduces wasted light among the light that is input via an optical fiber cable to a semiconductor light receiving element in which a circular light receiving part is divided radially into equal parts with respect to the center and connected in series. The object of the present invention is to provide an optical power feeding converter that can make the light incident evenly.
　請求項１の発明の光給電コンバータは、光ファイバケーブルを介して入力される光を半導体受光素子によって光電流に変換して出力する光給電コンバータにおいて、前記半導体受光素子は、半導体基板の第１面側に光電流を生成するために形成された円形受光部に対して、この第１面に対向する前記半導体基板の第２面側から前記円形受光部に光を入射させる裏面入射型受光素子であり、前記円形受光部は、この円形受光部の中心から延びる複数の直線状のアイソレーション溝によって受光面積が互いに等しくなるように分割され、且つ複数の導電性部材によって直列に接続された複数のフォトダイオードを備え、前記半導体基板の前記第２面側には、前記第１面側ほど縮径する円錐状に前記半導体基板を凹入させた円錐状凹部が、この円錐状凹部の対称軸線が前記円形受光部の中心を通るように形成され、前記第２面側から入射させた光が前記円錐状凹部によって円環状に変換されて、前記円形受光部の前記複数のフォトダイオードに夫々等しい光量が入射するように構成されたことを特徴としている。 The optical power feeding converter according to the invention according to claim 1 is an optical power feeding converter that converts light input via an optical fiber cable into a photocurrent by a semiconductor light receiving element and outputs the photocurrent, wherein the semiconductor light receiving element is a first one of a semiconductor substrate. A back-illuminated light-receiving element that allows light to enter the circular light-receiving portion from a second surface side of the semiconductor substrate opposite to the first surface of the circular light-receiving portion formed on the surface side to generate a photocurrent. The circular light-receiving section is divided into a plurality of linear isolation grooves extending from the center of the circular light-receiving section so that the light-receiving areas are equal to each other, and connected in series by a plurality of conductive members. A conical recess formed by recessing the semiconductor substrate into a conical shape whose diameter decreases toward the first surface is provided on the second surface side of the semiconductor substrate, and the symmetry axis of the conical recess is is formed to pass through the center of the circular light-receiving section, and the light incident from the second surface side is converted into an annular shape by the conical recess, and the light is equal to each of the plurality of photodiodes of the circular light-receiving section. It is characterized by being configured such that the amount of light is incident.
　上記構成によれば、光ファイバケーブルを介して入力される光が、円錐状凹部によって円環状に変換されて複数のフォトダイオードに均等に入射するので、複数のフォトダイオードの出力のばらつきを小さくすることができる。また、光電流を生成しない複数のアイソレーション溝が集中している円形受光部の中心近傍には、円環状の光が入射しないようにすることができるので、光電変換されずに無駄になる光を減少させることができる。従って、複数のフォトダイオードを直列に接続して形成された円形受光部を有する半導体受光素子の光電流を大きくすることができ、光給電コンバータが給電する電力を大きくすることができる。 According to the above configuration, the light input through the optical fiber cable is converted into an annular shape by the conical recess and is incident equally on the plurality of photodiodes, thereby reducing variations in the output of the plurality of photodiodes. be able to. In addition, since it is possible to prevent the annular light from entering the vicinity of the center of the circular light-receiving area where multiple isolation grooves that do not generate photocurrent are concentrated, the light is wasted without being photoelectrically converted. can be reduced. Therefore, the photocurrent of the semiconductor light-receiving element having a circular light-receiving section formed by connecting a plurality of photodiodes in series can be increased, and the power supplied by the optical power supply converter can be increased.
　請求項２の発明の光給電コンバータは、請求項１の発明において、前記光ファイバケーブルを介して入力される光を平行光に変換して前記円錐状凹部に入射させるコリメータレンズを備えたことを特徴としている。
　上記構成によれば、円錐状に広がりながら進行する光をコリメータレンズによって平行光に変換するので、円錐状凹部への入射角を一定にすることができる。それ故、入力される光が円形受光部からはみ出ないように、円形受光部の直径に合わせた平行光のビーム径となる光ファイバケーブルとコリメータレンズの間の距離を、容易に設定することができる。従って、入力される光の全部を円形受光部に入射させて、半導体受光素子の光電流を大きくすることができ、光給電コンバータが給電する電力を大きくすることができる。 The optical power feeding converter of the invention of claim 2 is the invention of claim 1, further comprising a collimator lens that converts the light input through the optical fiber cable into parallel light and makes it enter the conical recess. It is a feature.
According to the above configuration, since the light traveling in a conical shape is converted into parallel light by the collimator lens, the angle of incidence on the conical recess can be made constant. Therefore, it is easy to set the distance between the optical fiber cable and the collimator lens so that the input light does not protrude from the circular light receiving part, so that the beam diameter of the parallel light matches the diameter of the circular light receiving part. can. Therefore, all of the input light can be made incident on the circular light receiving section, the photocurrent of the semiconductor light receiving element can be increased, and the power supplied by the optical power supply converter can be increased.
　請求項３の発明の光給電コンバータは、請求項１又は２の発明において、前記円錐状凹部は、この円錐状凹部に入射した光を、前記円形受光部の直径以下の外径、且つ前記複数の直線状のアイソレーション溝が前記円形受光部の周方向に連なって形成された無効領域の外径よりも大きい内径を有する円環状に変換するように形成されたことを特徴としている。
　上記構成によれば、円錐状凹部によって変換された円環状の光は、円形受光部の中心近傍に形成される光電流を生成できない無効領域を避けて、全て円形受光部に入射する。従って、光ファイバケーブルを介して入力される光の全部を円錐状凹部に入射させることによって、光を無駄なく利用して、光給電コンバータが給電する電力を大きくすることができる。 In the optical power feeding converter according to the invention of claim 3, in the invention of claim 1 or 2, the conical recess allows the light incident on the conical recess to have an outer diameter equal to or less than a diameter of the circular light receiving part, and a plurality of The linear isolation groove is formed so as to be converted into an annular shape having an inner diameter larger than an outer diameter of an ineffective area formed continuously in the circumferential direction of the circular light receiving section.
According to the above configuration, all of the annular light converted by the conical recess is incident on the circular light receiving section, avoiding the ineffective area where photocurrent cannot be generated, which is formed near the center of the circular light receiving section. Therefore, by allowing all of the light input via the optical fiber cable to enter the conical recess, the light can be utilized without wastage and the power supplied by the optical power supply converter can be increased.
　本発明の光給電コンバータによれば、円形受光部がその中心に対して放射状に等分されて直列に接続された半導体受光素子に、光ファイバケーブルを介して入力される光のうち、無駄になる光を減少させて均等に入射させることができる。 According to the optical power supply converter of the present invention, the circular light receiving part is radially divided into equal parts with respect to the center thereof, and the semiconductor light receiving element connected in series is wasted among the light inputted through the optical fiber cable. It is possible to reduce the amount of light and make it evenly incident.
本発明の実施例１に係る光給電コンバータの斜視図である。1 is a perspective view of an optical power supply converter according to Example 1 of the present invention. 図１の光給電コンバータが有する半導体受光素子への光の入射の説明図である。FIG. 2 is an explanatory diagram of light incident on a semiconductor light-receiving element included in the optical power feeding converter of FIG. 1. FIG. 図２の半導体受光素子の円形受光部を示す平面図である。FIG. 3 is a plan view showing a circular light-receiving portion of the semiconductor light-receiving element of FIG. 2; 基台に固定された図３の半導体受光素子のIV－IV線断面図である。FIG. 4 is a sectional view taken along the line IV-IV of the semiconductor light receiving element of FIG. 3 fixed to a base. 光ファイバケーブルを介して入力される光の光強度分布図である。FIG. 2 is a light intensity distribution diagram of light input via an optical fiber cable. 図３のVI－VI線断面における半導体受光素子に入射して円環状に変換される光の説明図である。FIG. 4 is an explanatory diagram of light incident on a semiconductor light receiving element and converted into an annular shape in a cross section taken along line VI-VI in FIG. 3; 円錐状凹部の円錐面への平行光の入射角と円錐状凹部の頂点から円形受光部の中心までの距離をパラメータとして円環状の光の内径を等高線状に示すグラフである。7 is a graph showing the inner diameter of annular light in contour lines using the angle of incidence of parallel light on the conical surface of the conical recess and the distance from the apex of the conical recess to the center of the circular light receiving section as parameters. 半導体受光素子に入射して円環状に変換される光の他の例の説明図である。FIG. 7 is an explanatory diagram of another example of light that enters a semiconductor light receiving element and is converted into an annular shape. 円錐状凹部の形成用のエッチングマスクの説明図である。FIG. 3 is an explanatory diagram of an etching mask for forming a conical recess. エッチングによって円錐状凹部を形成する説明図である。It is an explanatory view of forming a conical recess by etching. 本発明の実施例２に係る光給電コンバータの半導体受光素子に入射して円環状に変換される光の説明図である。FIG. 7 is an explanatory diagram of light incident on the semiconductor light receiving element of the optical power supply converter according to Example 2 of the present invention and converted into an annular shape. 実施例２に係る光給電コンバータの半導体受光素子に入射して円環状に変換される光の他の例の説明図である。FIG. 7 is an explanatory diagram of another example of light that enters the semiconductor light receiving element of the optical power feeding converter according to the second embodiment and is converted into an annular shape.
　以下、本発明を実施するための形態について実施例に基づいて説明する。 Hereinafter, modes for carrying out the present invention will be described based on examples.
　図１、図２に示すように、光給電コンバータ１は、例えばシングルモードの光ファイバケーブルＯＣを介して入力される光（入射光Ｌ１）を光電流に変換して外部に給電するための１対の出力端子部２ａ，２ｂを有する。１対の出力端子部２ａ，２ｂが装備された基台３には、受光した光から光電変換により光電流を生成するための半導体受光素子１０と、この半導体受光素子１０の保護及び遮光のためのカバー５が夫々固定されている。半導体受光素子１０は、生成した光電流を出力するために、配線部３ａ，３ｂを介して対応する出力端子部２ａ，２ｂに接続されている。 As shown in FIGS. 1 and 2, the optical power supply converter 1 is a converter for converting light (incident light L1) input via a single mode optical fiber cable OC into a photocurrent and supplying power to the outside. It has a pair of output terminal parts 2a and 2b. The base 3 equipped with a pair of output terminals 2a and 2b includes a semiconductor light receiving element 10 for generating a photocurrent by photoelectric conversion from received light, and a semiconductor light receiving element 10 for protecting and shielding the semiconductor light receiving element 10. covers 5 are fixed respectively. The semiconductor light receiving element 10 is connected to corresponding output terminal parts 2a and 2b via wiring parts 3a and 3b in order to output the generated photocurrent.
　光ファイバケーブルＯＣを介して入力される入射光Ｌ１は、波長が例えば１．５μｍ程度の赤外光である。この入射光Ｌ１は、光ファイバケーブルＯＣの出射端Ｅから出射された後は、進行するほど照射範囲が広がる円錐状のビームである。 The incident light L1 input via the optical fiber cable OC is infrared light with a wavelength of, for example, about 1.5 μm. After the incident light L1 is emitted from the output end E of the optical fiber cable OC, it is a conical beam whose irradiation range becomes wider as it advances.
　カバー５は、入射光Ｌ１が通る光学系として、例えば屈折率が１．４５の光学ガラス製のコリメータレンズ６を有する。コリメータレンズ６は、入射光Ｌ１を平行光Ｌ２に変換して半導体受光素子１０に入射させる。半導体受光素子１０は、光電変換を行う円形受光部１２を有し、この円形受光部１２が形成されている側と反対側から光が入射される裏面入射型受光素子である。 The cover 5 has a collimator lens 6 made of optical glass with a refractive index of 1.45, for example, as an optical system through which the incident light L1 passes. The collimator lens 6 converts the incident light L1 into parallel light L2, and makes the parallel light L2 enter the semiconductor light receiving element 10. The semiconductor light-receiving element 10 is a back-illuminated light-receiving element that has a circular light-receiving section 12 that performs photoelectric conversion and receives light from the side opposite to the side on which the circular light-receiving section 12 is formed.
　カバー５は、コリメータレンズ６の光軸６ａが半導体受光素子１０の円形受光部１２に対して垂直に且つ円形受光部１２の中心Ｃを通るように基台３に固定される。光ファイバケーブルＯＣは、カバー５の挿入孔５ａに差し込まれ、その出射端Ｅがコリメータレンズ６から所定の距離だけ離隔した位置となるように固定される。このとき、入射光Ｌ１の光軸ＯＡがコリメータレンズ６の光軸６ａに一致するように、出射端Ｅが位置決めされる。 The cover 5 is fixed to the base 3 so that the optical axis 6a of the collimator lens 6 is perpendicular to the circular light receiving section 12 of the semiconductor light receiving element 10 and passes through the center C of the circular light receiving section 12. The optical fiber cable OC is inserted into the insertion hole 5a of the cover 5 and fixed so that its output end E is spaced a predetermined distance from the collimator lens 6. At this time, the output end E is positioned so that the optical axis OA of the incident light L1 coincides with the optical axis 6a of the collimator lens 6.
　図３、図４に示すように、円形受光部１２は、例えば光吸収層を備えた円形のＰＩＮ型フォトダイオードが、その中心Ｃから径方向に延びる複数の直線状のアイソレーション溝１３によって形状及び面積が同じ複数の扇形のフォトダイオード１４に等分されている。ここでは円形受光部１２が、３０本のアイソレーション溝１３によって３０個のフォトダイオード１４に等分されている。 As shown in FIGS. 3 and 4, the circular light-receiving section 12 is formed by a plurality of straight isolation grooves 13 extending radially from the center C of the circular PIN-type photodiode provided with a light absorption layer, for example. It is equally divided into a plurality of fan-shaped photodiodes 14 having the same area. Here, the circular light receiving section 12 is equally divided into 30 photodiodes 14 by 30 isolation grooves 13.
　複数の直線状のアイソレーション溝１３は、形状及び受光面積が等しい複数の扇形のフォトダイオード１４となるように、円形受光部１２の中心Ｃから一定幅で放射状に形成されている。また、円形受光部１２の外周に沿って円環状のアイソレーション溝１５が形成され、複数の直線状のアイソレーション溝１３が円環状のアイソレーション溝１５によって接続されている。そして、複数のアイソレーション溝１３によって電気的に分離された複数のフォトダイオード１４が、基台３に形成された導電性部材４によって直列に接続されて、円形受光部１２が形成されている。この円形受光部１２の直径をＤ１とする。 The plurality of linear isolation grooves 13 are formed radially with a constant width from the center C of the circular light receiving section 12 so as to form a plurality of fan-shaped photodiodes 14 having the same shape and light receiving area. Further, an annular isolation groove 15 is formed along the outer periphery of the circular light receiving portion 12, and a plurality of linear isolation grooves 13 are connected by the annular isolation groove 15. A plurality of photodiodes 14 electrically separated by a plurality of isolation grooves 13 are connected in series by a conductive member 4 formed on the base 3, thereby forming a circular light receiving section 12. The diameter of this circular light receiving portion 12 is assumed to be D1.
　こうして円形受光部１２には、中心Ｃを囲むように形状及び受光面積が等しい複数の扇形のフォトダイオード１４が形成されている。アイソレーション溝１３では光電流を生成できないので、アイソレーション溝１３の幅を小さく且つ直線状に形成して、円形受光部１２の面積に占めるアイソレーション溝１３の面積を小さくすることが好ましい。尚、図３ではアイソレーション溝１３とフォトダイオード１４の符号を一部省略している。 In this way, a plurality of sector-shaped photodiodes 14 having the same shape and light-receiving area are formed in the circular light-receiving section 12 so as to surround the center C. Since the isolation groove 13 cannot generate a photocurrent, it is preferable to form the isolation groove 13 with a small width and a straight line so that the area occupied by the isolation groove 13 in the area of the circular light receiving section 12 is reduced. In FIG. 3, some of the symbols of the isolation groove 13 and the photodiode 14 are omitted.
　円形受光部１２の中心Ｃ近傍において、複数の直線状のアイソレーション溝１３が集中している。そのため、中心Ｃ側ほど隣り合うアイソレーション溝１３が近づいて、中心Ｃから離隔した位置で複数のアイソレーション溝１３が幅方向に連なっている。これにより複数のアイソレーション溝１３が円形受光部１２の周方向に連なって、中心Ｃ近傍にアイソレーション溝１３の幅を一辺とする正多角形状の領域が形成されている。アイソレーション溝１３では光電変換をすることができないので、この正多角形状の領域は光電流を生成できない無効領域Ｉである。無効領域Ｉは、円形受光部１２の分割数が多いほど大きくなる。この無効領域Ｉの外径をＤ２とする。 A plurality of linear isolation grooves 13 are concentrated near the center C of the circular light receiving section 12. Therefore, adjacent isolation grooves 13 are closer toward the center C, and a plurality of isolation grooves 13 are connected in the width direction at positions spaced apart from the center C. As a result, the plurality of isolation grooves 13 are continuous in the circumferential direction of the circular light receiving portion 12, and a regular polygonal region having one side equal to the width of the isolation groove 13 is formed near the center C. Since photoelectric conversion cannot be performed in the isolation groove 13, this regular polygonal region is an ineffective region I in which no photocurrent can be generated. The invalid area I becomes larger as the number of divisions of the circular light receiving section 12 increases. The outer diameter of this invalid area I is assumed to be D2.
　フォトダイオード１４は、半絶縁性の半導体基板２０の第１面２０ａに積層されたｎ型半導体層２１と光吸収層２２とｐ型半導体層２３を有する。半導体基板２０は例えばＩｎＰ基板であり、ｎ型半導体層２１は例えばｎ－ＩｎＰ層であり、光吸収層２２は例えばＩｎＧａＡｓ層であり、ｐ型半導体層２３は例えばｐ－ＩｎＰ層であるが、これに限定されるものではない。また、フォトダイオード１４はＰＩＮ型に限定されるものではない。尚、ｎ型半導体層２１、光吸収層２２、ｐ型半導体層２３の厚さは適宜設定することができ、０．５～１０μｍ程度の厚さに形成される場合が多い。 The photodiode 14 includes an n-type semiconductor layer 21, a light absorption layer 22, and a p-type semiconductor layer 23, which are stacked on the first surface 20a of a semi-insulating semiconductor substrate 20. The semiconductor substrate 20 is, for example, an InP substrate, the n-type semiconductor layer 21 is, for example, an n-InP layer, the light absorption layer 22 is, for example, an InGaAs layer, and the p-type semiconductor layer 23 is, for example, a p-InP layer. It is not limited to this. Furthermore, the photodiode 14 is not limited to the PIN type. Note that the thicknesses of the n-type semiconductor layer 21, the light absorption layer 22, and the p-type semiconductor layer 23 can be set as appropriate, and are often formed to a thickness of about 0.5 to 10 μm.
　アイソレーション溝１３，１５は、ｎ型半導体層２１と光吸収層２２とｐ型半導体層２３が積層された半導体基板２０を、半導体基板２０が露出するようにｐ型半導体層２３側からエッチングすることによって形成される。これにより、円形受光部１２が電気的に分離された複数のフォトダイオード１４に分割される。尚、アイソレーション溝１３，１５は、例えば半導体基板２０側ほど幅が狭くなるように側壁が傾斜状に形成されてもよい。 The isolation grooves 13 and 15 are created by etching the semiconductor substrate 20, in which the n-type semiconductor layer 21, the light absorption layer 22, and the p-type semiconductor layer 23 are stacked, from the p-type semiconductor layer 23 side so that the semiconductor substrate 20 is exposed. formed by Thereby, the circular light receiving section 12 is divided into a plurality of electrically isolated photodiodes 14. Note that the isolation grooves 13 and 15 may have sidewalls formed in an inclined shape, for example, so that the width becomes narrower toward the semiconductor substrate 20 side.
　複数のフォトダイオード１４は、ｐ型半導体層２３と光吸収層２２を貫通してｎ型半導体層２１に到達する接続孔１７を夫々有する。そして、絶縁性の保護膜２４が、複数のフォトダイオード１４の表面と、これらフォトダイオード１４の接続孔１７の側壁を覆うように形成されている。この保護膜２４は、複数の直線状のアイソレーション溝１３及び円環状のアイソレーション溝１５の内壁部及び底部を覆っている。 The plurality of photodiodes 14 each have a connection hole 17 that penetrates the p-type semiconductor layer 23 and the light absorption layer 22 and reaches the n-type semiconductor layer 21. An insulating protective film 24 is formed to cover the surfaces of the plurality of photodiodes 14 and the side walls of the connection holes 17 of these photodiodes 14. The protective film 24 covers the inner walls and bottoms of the plurality of linear isolation grooves 13 and the annular isolation groove 15.
　各フォトダイオード１４は、ｐ型半導体層２３上の保護膜２４が部分的に除去されて露出したｐ型半導体層２３に接続されたアノード電極２７と、接続孔１７の底部の保護膜２４が除去されて露出したｎ型半導体層２１に接続されたカソード電極２８を備えている。アノード電極２７とカソード電極２８は、例えばリフトオフ法を用いて金属積層膜を選択的に堆積させることによって形成される。金属積層膜は、例えばチタン、クロムのような密着層と、例えば金、銀、アルミニウムのような低抵抗率層によって構成されている。 Each photodiode 14 has an anode electrode 27 connected to the p-type semiconductor layer 23 exposed by partially removing the protective film 24 on the p-type semiconductor layer 23, and a protective film 24 at the bottom of the connection hole 17 removed. A cathode electrode 28 is connected to the exposed n-type semiconductor layer 21. The anode electrode 27 and the cathode electrode 28 are formed by selectively depositing a metal laminated film using, for example, a lift-off method. The metal laminated film is composed of an adhesion layer such as titanium or chromium, and a low resistivity layer such as gold, silver, or aluminum.
　隣り合うフォトダイオード１４のうちの一方のアノード電極２７と他方のカソード電極２８とが、導電性ペースト８を介して基台３の導電性部材４によって接続されたことによって、円形受光部１２の複数のフォトダイオード１４が直列に接続されている。図示を省略するが、導電性部材４の代わりに、例えば金を主成分とする導電性ワイヤによって複数のフォトダイオード１４が直列に接続されていてもよく、保護膜２４上に選択的に形成された複数の配線によって複数のフォトダイオード１４が直列に接続されていてもよい。 One anode electrode 27 and the other cathode electrode 28 of the adjacent photodiodes 14 are connected by the conductive member 4 of the base 3 via the conductive paste 8, so that the plurality of circular light receiving parts 12 photodiodes 14 are connected in series. Although not shown, instead of the conductive member 4, a plurality of photodiodes 14 may be connected in series using, for example, a conductive wire mainly composed of gold, and the photodiodes 14 may be selectively formed on the protective film 24. A plurality of photodiodes 14 may be connected in series by a plurality of wiring lines.
　直列に接続された複数の扇形のフォトダイオード１４によって円形受光部１２が形成されているので、半導体受光素子１０が出力する光電流は小さくなるが、その出力電圧を高くすることができる。従って、この半導体受光素子１０を備え、光ファイバケーブルＯＣを介して入力される入射光Ｌ１を光電変換して給電する光給電コンバータ１は、高い電圧で給電することができる。 Since the circular light-receiving section 12 is formed by a plurality of fan-shaped photodiodes 14 connected in series, the photocurrent output by the semiconductor light-receiving element 10 becomes small, but its output voltage can be increased. Therefore, the optical power supply converter 1, which includes this semiconductor light receiving element 10 and supplies power by photoelectrically converting the incident light L1 inputted through the optical fiber cable OC, can supply power at a high voltage.
　図２、図５に示すように、光ファイバケーブルＯＣの出射端Ｅから出射された入射光Ｌ１は、例えば頂角θ（全角）が１４°の円錐状に広がりながら進行する。この入射光Ｌ１の光強度分布は、光軸ＯＡに垂直な平面Ｐ上においてガウス分布になり、光軸ＯＡから離隔するほど光強度が低下すると共に光軸ＯＡに対して回転対称の光強度分布になる。尚、光強度が光軸ＯＡ上の光強度の１／ｅ２になるところを入射光Ｌ１の最外周としている。 As shown in FIGS. 2 and 5, the incident light L1 emitted from the output end E of the optical fiber cable OC travels while expanding into a conical shape with an apex angle θ (full angle) of 14°, for example. The light intensity distribution of this incident light L1 becomes a Gaussian distribution on the plane P perpendicular to the optical axis OA, and the light intensity decreases as the distance from the optical axis OA increases, and the light intensity distribution is rotationally symmetrical with respect to the optical axis OA. become. Note that the outermost periphery of the incident light L1 is defined as the point where the light intensity becomes 1/e 2 of the light intensity on the optical axis OA.
　図６に示すように、入射光Ｌ１をコリメータレンズ６に入射させる場合に、入射光Ｌ１の光軸ＯＡをコリメータレンズ６の光軸６ａに一致させる。コリメータレンズ６は、入射光Ｌ１を平行光Ｌ２に変換して裏面入射型の半導体受光素子１０に入射させる。平行光Ｌ２の光強度分布は、入射光Ｌ１がコリメータレンズ６に入射したときの光強度分布が維持されている。 As shown in FIG. 6, when the incident light L1 is made to enter the collimator lens 6, the optical axis OA of the incident light L1 is made to coincide with the optical axis 6a of the collimator lens 6. The collimator lens 6 converts the incident light L1 into parallel light L2, and makes the parallel light L2 enter the back-illuminated semiconductor light receiving element 10. The light intensity distribution of the parallel light L2 is maintained as the light intensity distribution when the incident light L1 enters the collimator lens 6.
　半導体受光素子１０は、円形受光部１２が形成された半導体基板２０の第１面２０ａに対向する半導体基板２０の第２面２０ｂ側（裏面側）に、第１面２０ａ側ほど縮径するように半導体基板２０を円錐状に凹入させて形成された円錐状凹部１６を有する。この円錐状凹部１６の対称軸１６ａの延長線（対称軸線）が、円形受光部１２に対して垂直に且つ円形受光部１２の中心Ｃを通るように、円錐状凹部１６が形成されている。コリメータレンズ６の光軸６ａは、円形受光部１２の中心Ｃを通るように位置合わせされているので、円錐状凹部１６の対称軸線に一致する。そして、入射光Ｌ１の光軸ＯＡをコリメータレンズ６の光軸６ａに一致させたので、光軸ＯＡは平行光Ｌ２の光軸になり、光軸ＯＡが円錐状凹部１６の対称軸線に一致する。 The semiconductor light-receiving element 10 has a diameter decreasing toward the second surface 20b (back surface side) of the semiconductor substrate 20 opposite to the first surface 20a of the semiconductor substrate 20 on which the circular light-receiving portion 12 is formed. A conical recess 16 is formed by recessing the semiconductor substrate 20 into a conical shape. The conical recess 16 is formed such that an extension line (axis of symmetry) of the axis of symmetry 16a of the conical recess 16 is perpendicular to the circular light receiving section 12 and passes through the center C of the circular light receiving section 12. The optical axis 6a of the collimator lens 6 is aligned so as to pass through the center C of the circular light receiving section 12, and thus coincides with the axis of symmetry of the conical recess 16. Since the optical axis OA of the incident light L1 is made to coincide with the optical axis 6a of the collimator lens 6, the optical axis OA becomes the optical axis of the parallel light L2, and the optical axis OA coincides with the axis of symmetry of the conical recess 16. .
　円錐状凹部１６の円錐面１６ｂに入射した平行光Ｌ２は、光軸ＯＡから離隔するように屈折し、円環状の光Ｌ３に変換される。コリメータレンズ６で変換された平行光Ｌ２のビーム径をＤｂとする。また、円錐状凹部１６の頂点から距離Ｔだけ離隔した円形受光部１２に入射する円環状の光Ｌ３の外径をＤｏ、内径をＤｉとする。 The parallel light L2 incident on the conical surface 16b of the conical recess 16 is refracted away from the optical axis OA and converted into annular light L3. Let Db be the beam diameter of the parallel light L2 converted by the collimator lens 6. Further, the outer diameter of the annular light L3 incident on the circular light receiving portion 12 spaced apart by a distance T from the apex of the conical recess 16 is Do, and the inner diameter is Di.
　円錐状凹部１６の円錐面１６ｂの傾斜角度（円錐底面と母線のなす角度）をαとすると、平行光Ｌ２の円錐面１６ｂへの入射角がαである。半導体基板２０の空気に対する屈折率をｎとし、円錐面１６ｂに入射した平行光Ｌ２の出射角をβとすると、スネルの法則から下記（１）式が成り立つ。
　β＝ｓｉｎ－１（（ｓｉｎ（α））／ｎ）　・・・（１）
　以下ではｎ＝３．２として説明するが、屈折率ｎはこれに限定されるものではない。 If the inclination angle of the conical surface 16b of the conical recess 16 (the angle between the conical bottom surface and the generating line) is α, then the incident angle of the parallel light L2 on the conical surface 16b is α. If the refractive index of the semiconductor substrate 20 with respect to air is n and the exit angle of the parallel light L2 incident on the conical surface 16b is β, the following equation (1) holds true from Snell's law.
β=sin -1 ((sin(α))/n) ...(1)
Although the following description will be made assuming that n=3.2, the refractive index n is not limited to this.
　円錐状凹部１６によって変換された円環状の光Ｌ３が円形受光部１２に入射するときの径方向のビーム幅をｔとすると、このビーム幅は下記（２）式で表される。
　ｔ＝（Ｄｂ／２）×（ｃｏｓ（β）／（ｃｏｓ（α）×ｃｏｓ（α－β））　・・・（２） When the beam width in the radial direction when the annular light L3 converted by the conical recess 16 is incident on the circular light receiving section 12 is t, this beam width is expressed by the following equation (2).
t=(Db/2)×(cos(β)/(cos(α)×cos(α-β))...(2)
　そして、円環状の光Ｌ３の内径Ｄｉ、外径Ｄｏは下記（３），（４）式のようになる。
　Ｄｉ＝２×Ｔ×ｔａｎ（α－β）　・・・（３）
　Ｄｏ＝Ｄｉ＋２×ｔ　・・・（４） The inner diameter Di and outer diameter Do of the annular light L3 are expressed by the following equations (3) and (4).
Di=2×T×tan(α-β)...(3)
Do=Di+2×t...(4)
　図７には、入射角αと距離Ｔをパラメータとして円環状の光Ｌ３の内径Ｄｉが等高線状に示されている。入射角αが一定であれば、距離Ｔが大きくなるほど内径Ｄｉが大きくなる。一方、距離Ｔが一定であれば、入射角αが大きくなるほど内径Ｄｉが大きくなる。尚、半導体基板の種類によるが、通常は半導体基板２０の厚さが７００μｍ程度であり、距離Ｔを半導体基板２０の厚さ以上にすることはできない。 In FIG. 7, the inner diameter Di of the annular light L3 is shown in contour lines using the incident angle α and the distance T as parameters. If the incident angle α is constant, the larger the distance T, the larger the inner diameter Di. On the other hand, if the distance T is constant, the inner diameter Di increases as the incident angle α increases. Although it depends on the type of semiconductor substrate, the thickness of the semiconductor substrate 20 is usually about 700 μm, and the distance T cannot be made greater than the thickness of the semiconductor substrate 20.
　図７及び上記（１）～（４）式を用いることによって、例えば円環状の光Ｌ３の内径Ｄｉが所望の大きさに設定された場合に、円錐状凹部１６の形状とサイズ、及び平行光Ｌ２のビーム径Ｄｂを設定することができる。そして、カバー５における光ファイバケーブルＯＣとコリメータレンズ６の距離を設定することができる。 By using FIG. 7 and equations (1) to (4) above, for example, when the inner diameter Di of the annular light L3 is set to a desired size, the shape and size of the conical recess 16, and the parallel light The beam diameter Db of L2 can be set. Then, the distance between the optical fiber cable OC and the collimator lens 6 in the cover 5 can be set.
　円形受光部１２の中心Ｃ近傍の無効領域Ｉに入射する光による光入力の無駄を少なくするために、円環状の光Ｌ３の内径Ｄｉを無効領域Ｉの外径Ｄ２よりも大きく設定する場合について説明する。アイソレーション溝１３の幅を１０μｍ、フォトダイオード１４の数を３０個とすると、無効領域Ｉは一辺が１０μｍの正三十角形なので外周の長さが３００μｍであり、無効領域Ｉの外径Ｄ２は１００μｍ未満である。 Regarding the case where the inner diameter Di of the annular light L3 is set larger than the outer diameter D2 of the ineffective area I in order to reduce wasted light input due to light entering the ineffective area I near the center C of the circular light receiving section 12. explain. Assuming that the width of the isolation groove 13 is 10 μm and the number of photodiodes 14 is 30, the ineffective region I is a regular tridecagon with a side of 10 μm, so the length of the outer circumference is 300 μm, and the outer diameter D2 of the ineffective region I is It is less than 100 μm.
　円環状の光Ｌ３の内径Ｄｉを例えば１００μｍに設定すると、図７から例えば入射角αが２０°、距離Ｔが４７０μｍになり、円錐状凹部１６の形状とサイズが決まり、出射角βが６．１°になる。このとき半導体基板２０の第２面２０ｂにおける円錐状凹部１６の直径は１２６４μｍ、円錐状凹部１６の深さは２３０μｍになる。平行光Ｌ２の全部が円錐状凹部１６を介して直径Ｄ１が例えば１２００μｍの円形受光部１２に入射するように、円環状の光Ｌ３の外径Ｄｏを１２００μｍとすると、平行光Ｌ２のビーム径Ｄｂが１１０８μｍになる。そして、所定の距離としてコリメータレンズ６と光ファイバケーブルＯＣの出射端Ｅの間の距離が４５１３μｍに定まる。 When the inner diameter Di of the annular light L3 is set to, for example, 100 μm, the incident angle α is 20° and the distance T is 470 μm from FIG. 7, the shape and size of the conical recess 16 are determined, and the output angle β is 6. It becomes 1°. At this time, the diameter of the conical recess 16 on the second surface 20b of the semiconductor substrate 20 is 1264 μm, and the depth of the conical recess 16 is 230 μm. If the outer diameter Do of the annular light L3 is set to 1200 μm so that the entire parallel light L2 enters the circular light receiving portion 12 having a diameter D1 of, for example, 1200 μm through the conical recess 16, the beam diameter Db of the parallel light L2 is becomes 1108 μm. Then, the distance between the collimator lens 6 and the output end E of the optical fiber cable OC is determined to be 4513 μm as the predetermined distance.
　円環状の光Ｌ３の外径Ｄｏは円形受光部１２の直径Ｄ１より小さくてもよいので、平行光Ｌ２のビーム径Ｄｂが小さくなるようにコリメータレンズ６と光ファイバケーブルＯＣの出射端Ｅの間の距離を小さくして、光給電コンバータ１を小型化することができる。コリメータレンズ６と光ファイバケーブルＯＣの出射端Ｅの間の距離を小さくしても、円環状の光Ｌ３の内径Ｄｉは変わらない。コリメータレンズ６と半導体受光素子１０の間の距離は任意に設定できるが、小さいほど光給電コンバータ１の小型化に有利である。 Since the outer diameter Do of the annular light L3 may be smaller than the diameter D1 of the circular light receiving part 12, the distance between the collimator lens 6 and the output end E of the optical fiber cable OC is adjusted so that the beam diameter Db of the parallel light L2 is small. By reducing the distance, the optical power feeding converter 1 can be made smaller. Even if the distance between the collimator lens 6 and the output end E of the optical fiber cable OC is reduced, the inner diameter Di of the annular light L3 does not change. Although the distance between the collimator lens 6 and the semiconductor light receiving element 10 can be set arbitrarily, the smaller the distance, the more advantageous it is to downsizing the optical power feeding converter 1.
　例えば図８に示すように、平行光Ｌ２の光軸近傍部分を円錐状凹部１６を介して円形受光部１２に入射させ、平行光Ｌ２の残り部分は円錐状凹部１６を介さずに平行光のまま円形受光部１２に入射させてもよい。この場合、径方向に広がって進行する光と平行光とが混在する円環状の光Ｌ３が、円形受光部１２に入射する。少なくとも平行光のままでは無効領域Ｉに入射する平行光Ｌ２の一部の光について、円錐状凹部１６によって進行方向を変えることにより、無効領域Ｉを避けて円形受光部１２に均等に入射させることができればよい。特に、無効領域Ｉに近いほど、円形受光部１２の周方向におけるアイソレーション溝１３が占める割合が大きいため、光電変換されない高強度の光が多くなるので、円環状の光Ｌ３の内径Ｄｉを大きくする場合に有用である。 For example, as shown in FIG. 8, a portion of the parallel light L2 near the optical axis is made incident on the circular light receiving portion 12 through the conical recess 16, and the remaining portion of the parallel light L2 is transmitted as parallel light without passing through the conical recess 16. The light may be directly incident on the circular light receiving section 12. In this case, the annular light L3, in which light that spreads in the radial direction and parallel light coexist, enters the circular light receiving section 12. At least a part of the parallel light L2 that would be incident on the invalid area I if it is parallel light is changed in its traveling direction by the conical recess 16, thereby avoiding the invalid area I and making it equally incident on the circular light receiving part 12. It would be good if you could. In particular, the closer to the ineffective area I, the larger the proportion of the isolation groove 13 in the circumferential direction of the circular light receiving part 12 is, and the more high-intensity light is not photoelectrically converted, so the inner diameter Di of the annular light L3 is increased. This is useful when
　図８の場合も上記と同様に、円錐状凹部１６に入射して円環状になる光の内径Ｄｉを設定して、入射角αと距離Ｔを設定することができる。例えば内径Ｄｉを１５０μｍとして、入射角αを３０°とすると距離Ｔは４８０μｍになり、円錐状凹部１６の形状とサイズが決まり、出射角βが９°になる。このとき第２面２０ｂにおける円錐状凹部１６の直径は７６２μｍ、深さは２２０μｍになる。そして、円錐状凹部１６に入射して円環状になる光の外径Ｄｏは１０８１μｍになる。 In the case of FIG. 8 as well, the incident angle α and the distance T can be set by setting the inner diameter Di of the light that enters the conical recess 16 and becomes annular. For example, when the inner diameter Di is 150 μm and the incident angle α is 30°, the distance T is 480 μm, which determines the shape and size of the conical recess 16, and the output angle β is 9°. At this time, the diameter of the conical recess 16 on the second surface 20b is 762 μm, and the depth is 220 μm. The outer diameter Do of the light that enters the conical recess 16 and becomes annular is 1081 μm.
　一方、平行光Ｌ２のビーム径Ｄｂは、円錐状凹部１６の直径より大きく、且つ円形受光部１２の直径Ｄ１以下の範囲内で任意に設定することができる。円環状の光Ｌ３の円形受光部１２における内径は、円錐状凹部１６の形状及びサイズによって、円錐状凹部１６に入射して円環状になる光の内径Ｄｉ又は円錐状凹部１６の直径の何れか一方に決まる。また、円環状の光Ｌ３の円形受光部１２における外径は、円錐状凹部１６の形状及びサイズによって、平行光Ｌ２のビーム径Ｄｂ又は円錐状凹部１６に入射して円環状になる光の外径Ｄｏの何れか一方に決まる。 On the other hand, the beam diameter Db of the parallel light L2 can be arbitrarily set within a range that is larger than the diameter of the conical recess 16 and less than or equal to the diameter D1 of the circular light receiving section 12. The inner diameter of the annular light L3 in the circular light receiving part 12 is either the inner diameter Di of the light that enters the conical recess 16 and becomes annular or the diameter of the conical recess 16, depending on the shape and size of the conical recess 16. Decided on one side. Also, the outer diameter of the annular light L3 at the circular light receiving part 12 depends on the shape and size of the conical recess 16, and the beam diameter Db of the parallel light L2 or the outer diameter of the light that enters the conical recess 16 and becomes annular. The diameter is determined by either one of the diameters Do.
　次に、円錐状凹部１６の形成方法について説明する。
　例えば図９に示すように、半導体基板２０の第２面２０ｂに、円錐状の凹部３０ａを有するエッチングマスク層３０を形成する。円錐状の凹部３０ａは対称軸３０ｂを有する。エッチングマスク層３０は、例えば露光量の違いによって厚さを連続的に変化させることによって円錐状に凹入させたフォトレジストである。 Next, a method for forming the conical recess 16 will be explained.
For example, as shown in FIG. 9, an etching mask layer 30 having a conical recess 30a is formed on the second surface 20b of the semiconductor substrate 20. The conical recess 30a has an axis of symmetry 30b. The etching mask layer 30 is a photoresist whose thickness is continuously changed depending on, for example, a difference in exposure amount, thereby making a recess into a conical shape.
　そして、図１０に示すように例えば反応性イオンエッチングによって、エッチングマスク層３０が薄い部分ほど深くエッチングして、エッチングマスク層３０の形状が反映された円錐状凹部１６が形成される。半導体基板２０の第１面２０ａ側に形成された円形受光部１２の中心Ｃに対称軸３０ｂを位置合わせすることによって、対称軸１６ａが円形受光部１２の中心Ｃに位置合わせされた円錐状凹部１６が形成される。円錐状凹部１６は、砥石等によって半導体基板２０を円錐状に研削、研磨することによって形成されてもよい。また、円錐状凹部１６は、半導体基板２０の第１面側２０ａに円形受光部１２を形成した後で第２面側２０ｂに形成されるが、円錐状凹部１６の形成後に対称軸１６ａに中心Ｃが位置合わせされた円形受光部１２が形成されてもよい。 Then, as shown in FIG. 10, by reactive ion etching, for example, the thinner portions of the etching mask layer 30 are etched more deeply to form conical recesses 16 that reflect the shape of the etching mask layer 30. By aligning the axis of symmetry 30b with the center C of the circular light receiving section 12 formed on the first surface 20a side of the semiconductor substrate 20, a conical recess is formed in which the axis of symmetry 16a is aligned with the center C of the circular light receiving section 12. 16 is formed. The conical recess 16 may be formed by grinding and polishing the semiconductor substrate 20 into a conical shape using a grindstone or the like. Further, the conical recess 16 is formed on the second surface side 20b after the circular light receiving section 12 is formed on the first surface side 20a of the semiconductor substrate 20. A circular light receiving portion 12 may be formed in which C is aligned.
　上記実施例１の光給電コンバータ１のコリメータレンズ６を省略した場合について、図１１に基づいて説明する。上記実施例１と共通する部分には同じ符号を付して説明を省略する。
　半導体受光素子１０には、光ファイバケーブルＯＣの出射端Ｅから出射された頂角θの円錐状に広がる入射光Ｌ１が入射する。円形受光部１２の中心Ｃ近傍に形成される無効領域Ｉへの光の入射を防ぐため、上記と同様に円錐状凹部１６によって入射光Ｌ１を円環状の光Ｌ３’に変換して、円形受光部１２に入射させる。 A case where the collimator lens 6 of the optical power feeding converter 1 of the first embodiment is omitted will be described based on FIG. 11. The same parts as in the first embodiment are given the same reference numerals and the description thereof will be omitted.
The semiconductor light-receiving element 10 receives incident light L1 emitted from the output end E of the optical fiber cable OC and spread into a conical shape with an apex angle θ. In order to prevent light from entering the ineffective area I formed near the center C of the circular light receiving section 12, the incident light L1 is converted into an annular light L3' by the conical recess 16 in the same way as described above, and the circular light receiving section 12.
　円錐状凹部１６の形状、サイズは、光軸ＯＡ上の光に対して、上記と同様に円環状の光Ｌ３’の内径Ｄｉ、入射角α、距離Ｔを設定することによって決まる。例えば内径Ｄｉを１５０μｍ、入射角αを２４°とすると出射角βは７．３°になり、図７から距離Ｔが５８０μｍになり、円錐状凹部１６の底面の直径が５３９μｍ、深さが１２０μｍになる。 The shape and size of the conical recess 16 are determined by setting the inner diameter Di, incident angle α, and distance T of the annular light L3' with respect to the light on the optical axis OA in the same manner as described above. For example, if the inner diameter Di is 150 μm and the incident angle α is 24°, the output angle β is 7.3°, and from FIG. become.
　入射光Ｌ１の全部が円錐状凹部１６を介して円形受光部１２に入射するように、出射端Ｅと半導体受光素子１０の間の距離を設定することができる。入射光Ｌ１の円錐面１６ｂへの入射角は光軸ＯＡから離隔するほど小さくなり、入射光Ｌ１の最外周部分の円錐面１６ｂへの入射角はα－（θ／２）である。また、その出射角γは光軸ＯＡ上の光の出射角βよりも小さくなる。そして、円環状の光Ｌ３’の外径Ｄｏが円形受光部１２の直径Ｄ１以下になる出射端Ｅと半導体受光素子１０の間の距離を所定の距離として設定する。 The distance between the output end E and the semiconductor light receiving element 10 can be set so that all of the incident light L1 enters the circular light receiving section 12 through the conical recess 16. The angle of incidence of the incident light L1 on the conical surface 16b becomes smaller as the distance from the optical axis OA increases, and the angle of incidence of the outermost portion of the incident light L1 on the conical surface 16b is α-(θ/2). Further, the output angle γ is smaller than the output angle β of the light on the optical axis OA. Then, the distance between the output end E and the semiconductor light receiving element 10 at which the outer diameter Do of the annular light L3' is equal to or less than the diameter D1 of the circular light receiving portion 12 is set as a predetermined distance.
　例えばθ＝１４°の場合に、入射光Ｌ１の全部を直径が５３９μｍの円錐状凹部１６に入射させるためには、出射端Ｅと半導体受光素子１０の間の距離が最大で２１９５μｍになる。このとき、ビーム径が円錐状凹部１６の直径Ｄ１に等しい入射光Ｌ１が円錐状凹部１６に入射して、円環状の光Ｌ３’の外径Ｄｏが７０１μｍになる。 For example, when θ=14°, in order to make all of the incident light L1 enter the conical recess 16 with a diameter of 539 μm, the distance between the output end E and the semiconductor light receiving element 10 is at most 2195 μm. At this time, the incident light L1 whose beam diameter is equal to the diameter D1 of the conical recess 16 enters the conical recess 16, and the outer diameter Do of the annular light L3' becomes 701 μm.
　この外径Ｄｏが円形受光部１２の直径Ｄ１より大きい場合には、出射端Ｅと半導体受光素子１０の間の距離を小さくして円錐状凹部１６への入射光Ｌ１のビーム径を小さくすることにより、入射光Ｌ１の全部が無効領域Ｉを避けながら円形受光部１２に入射させることができる。円環状の光Ｌ３’の外径Ｄｏは円形受光部１２の直径Ｄ１以下であればよい。出射端Ｅと半導体受光素子１０の間の距離を変えても、円環状の光Ｌ３’の内径Ｄｉは変わらない。 When this outer diameter Do is larger than the diameter D1 of the circular light receiving portion 12, the distance between the output end E and the semiconductor light receiving element 10 is reduced to reduce the beam diameter of the incident light L1 to the conical recess 16. Accordingly, all of the incident light L1 can be made to enter the circular light receiving section 12 while avoiding the ineffective area I. The outer diameter Do of the annular light L3' may be less than or equal to the diameter D1 of the circular light receiving section 12. Even if the distance between the emission end E and the semiconductor light receiving element 10 is changed, the inner diameter Di of the annular light L3' does not change.
　一方、図１２に示すように、入射光Ｌ１の光軸ＯＡ近傍部分が円錐状凹部１６を介して円形受光部１２に入射し、入射光Ｌ１の残りの外周側部分が円錐状凹部１６を介さずに円形受光部１２に入射するようにしてもよい。この場合、径方向への広がり方が異なる光が混在する円環状の光Ｌ３’が、円形受光部１２に入射する。 On the other hand, as shown in FIG. 12, a portion of the incident light L1 near the optical axis OA enters the circular light receiving portion 12 via the conical recess 16, and the remaining outer peripheral portion of the incident light L1 enters the circular light receiving portion 12 via the conical recess 16. Alternatively, the light may be incident on the circular light receiving section 12 without being exposed. In this case, the annular light L<b>3 ′, in which light that spreads in different ways in the radial direction is mixed, enters the circular light receiving section 12 .
　少なくとも入射光Ｌ１のうちの無効領域Ｉに入射する部分について、円錐状凹部１６によって進行方向を変えることにより、無効領域Ｉを避けて円形受光部１２に均等に入射させることができればよい。特に、無効領域Ｉに近いほど、円形受光部１２の周方向におけるアイソレーション溝１３が占める割合が大きいため、光電変換されない高強度の光が多くなるので、円環状の光Ｌ３’の内径Ｄｉを大きくする場合に有用である。 It is only necessary that at least a portion of the incident light L1 that is incident on the ineffective area I can be made to avoid the ineffective area I and be made equally incident on the circular light receiving section 12 by changing the traveling direction by the conical recess 16. In particular, the closer to the ineffective area I, the larger the ratio of the isolation groove 13 in the circumferential direction of the circular light receiving part 12 is, and the more high-intensity light that is not photoelectrically converted, the inner diameter Di of the annular light L3' is This is useful when increasing the size.
　上記光給電コンバータ１の作用、効果について説明する。
　光ファイバケーブルＯＣを介して光給電コンバータ１に入力される入射光Ｌ１は、半導体受光素子１０に形成された円錐状凹部１６によって円環状の光Ｌ３，Ｌ３’に変換され、円形受光部１２が等分された複数のフォトダイオード１４に均等に、等しい光量が入射する。従って、複数のフォトダイオード１４の出力のばらつきを小さくすることができる。また、光電流を生成しない複数のアイソレーション溝１３が集中している円形受光部１２の中心Ｃ近傍には、円環状の光Ｌ３，Ｌ３’が入射しないので、入射光Ｌ１のうちの光電変換されずに無駄になる光を減少させることができる。従って、複数のフォトダイオード１４を直列に接続して形成された円形受光部１２を有する半導体受光素子１０の光電流を大きくすることができ、光給電コンバータ１が給電する電力を大きくすることができる。 The operation and effects of the optical power feeding converter 1 will be explained.
Incident light L1 input to the optical power supply converter 1 via the optical fiber cable OC is converted into annular lights L3 and L3' by the conical recess 16 formed in the semiconductor light receiving element 10, and the circular light receiving part 12 An equal amount of light enters the plurality of equally divided photodiodes 14. Therefore, variations in the outputs of the plurality of photodiodes 14 can be reduced. Further, since the annular lights L3 and L3' do not enter the vicinity of the center C of the circular light receiving section 12 where the plurality of isolation grooves 13 that do not generate photocurrent are concentrated, the photoelectric conversion of the incident light L1 It can reduce the amount of light that is wasted. Therefore, the photocurrent of the semiconductor light receiving element 10 having the circular light receiving section 12 formed by connecting a plurality of photodiodes 14 in series can be increased, and the power supplied by the optical power supply converter 1 can be increased. .
　また、円錐状に広がりながら進行する入射光Ｌ１をコリメータレンズ６によって平行光Ｌ２に変換する場合には、円錐状凹部１６への入射角αを一定にすることができる。それ故、入力される入射光Ｌ１が円形受光部１２からはみ出ないように、円形受光部１２の直径Ｄ１に合わせた平行光Ｌ２のビーム径Ｄｂとなる光ファイバケーブルＯＣの出射端Ｅとコリメータレンズ６の間の距離を容易に設定することができる。従って、入力される入射光Ｌ１の全部を円形受光部１２に入射させて、半導体受光素子１０の光電流を大きくすることができ、光給電コンバータ１が給電する電力を大きくすることができる。 Furthermore, when the incident light L1 traveling while expanding in a conical shape is converted into parallel light L2 by the collimator lens 6, the angle of incidence α into the conical recess 16 can be made constant. Therefore, in order to prevent the input incident light L1 from protruding from the circular light receiving section 12, the output end E of the optical fiber cable OC and the collimator lens are arranged so that the beam diameter Db of the parallel light L2 matches the diameter D1 of the circular light receiving section 12. 6 can be easily set. Therefore, all of the input incident light L1 can be made incident on the circular light receiving section 12, the photocurrent of the semiconductor light receiving element 10 can be increased, and the power supplied by the optical power supply converter 1 can be increased.
　その上、円錐状凹部１６は、円錐面１６ｂに入射した光を、円形受光部１２の直径Ｄ１以下の外径Ｄｏ、且つ円形受光部１２の無効領域Ｉの外径Ｄ２よりも大きい内径Ｄｉを有する円環状の光Ｌ３，Ｌ３’に変換する。円環状の光Ｌ３，Ｌ３’は円形受光部１２の中心Ｃ近傍に形成される光電流を生成できない無効領域Ｉを避けて、全て円形受光部１２に入射する。従って、光ファイバケーブルＯＣを介して入力される入射光Ｌ１を無駄なく利用して、光給電コンバータ１が給電する電力を大きくすることができる。 Moreover, the conical recess 16 allows the light incident on the conical surface 16b to pass through an outer diameter Do that is less than or equal to the diameter D1 of the circular light receiving section 12 and an inner diameter Di that is larger than the outer diameter D2 of the invalid area I of the circular light receiving section 12. It is converted into annular lights L3 and L3' having the following characteristics. The annular lights L3 and L3' all enter the circular light receiving section 12, avoiding an ineffective region I formed near the center C of the circular light receiving section 12 where no photocurrent can be generated. Therefore, the incident light L1 inputted through the optical fiber cable OC can be utilized without wastage, and the power supplied by the optical power supply converter 1 can be increased.
　その他、当業者であれば、本発明の趣旨を逸脱することなく、上記実施形態に種々の変更を付加した形態で実施可能であり、本発明はその種の変更形態も包含するものである。 In addition, those skilled in the art can implement various modifications to the above embodiments without departing from the spirit of the present invention, and the present invention includes such modifications.
１　　：光給電コンバータ
２ａ，２ｂ：出力端子部
３　　：基台
４　　：導電性部材
５　　：カバー
５ａ　：挿入孔
６　　：コリメータレンズ
６ａ　：対称軸
８　　：導電性ペースト
１０　：半導体受光素子
１２　：円形受光部
１３　：アイソレーション溝
１４　：フォトダイオード
１５　：アイソレーション溝
１６　：円錐状凹部
１６ａ：対称軸
１６ｂ：円錐面
１７　：接続孔
２０　：半導体基板
２１　：ｎ型半導体層
２２　：光吸収層
２３　：ｐ型半導体層
２４　：保護膜
２７　：アノード電極
２８　：カソード電極
Ｌ１　：入射光
Ｌ２　：平行光
Ｌ３，Ｌ３’　：円環状の光
ＯＡ　：光軸
ＯＣ　：光ファイバケーブル
Ｅ　　：出射端
Ｉ　　：無効領域 1: Optical power supply converter 2a, 2b: Output terminal section 3: Base 4: Conductive member 5: Cover 5a: Insertion hole 6: Collimator lens 6a: Axis of symmetry 8: Conductive paste 10: Semiconductor photodetector 12: Circular light receiving Part 13: Isolation groove 14: Photodiode 15: Isolation groove 16: Conical recess 16a: Axis of symmetry 16b: Conical surface 17: Connection hole 20: Semiconductor substrate 21: N-type semiconductor layer 22: Light absorption layer 23: p Type semiconductor layer 24: Protective film 27: Anode electrode 28: Cathode electrode L1: Incident light L2: Parallel light L3, L3': Annular light OA: Optical axis OC: Optical fiber cable E: Output end I: Ineffective area

Claims (3)

  1. 　光ファイバケーブルを介して入力される光を半導体受光素子によって光電流に変換して出力する光給電コンバータにおいて、
    　前記半導体受光素子は、半導体基板の第１面側に光電流を生成するために形成された円形受光部に対して、この第１面に対向する前記半導体基板の第２面側から前記円形受光部に光を入射させる裏面入射型受光素子であり、
    　前記円形受光部は、この円形受光部の中心から延びる複数の直線状のアイソレーション溝によって受光面積が互いに等しくなるように分割され、且つ複数の導電性部材によって直列に接続された複数のフォトダイオードを備え、
    　前記半導体基板の前記第２面側には、前記第１面側ほど縮径する円錐状に前記半導体基板を凹入させた円錐状凹部が、この円錐状凹部の対称軸線が前記円形受光部の中心を通るように形成され、
    　前記第２面側から入射させた光が前記円錐状凹部によって円環状に変換されて、前記円形受光部の前記複数のフォトダイオードに夫々等しい光量が入射するように構成されたことを特徴とする光給電コンバータ。     In an optical power supply converter that converts light input via an optical fiber cable into photocurrent using a semiconductor photodetector and outputs the photocurrent,
    The semiconductor light-receiving element receives the circular light-receiving portion from the second surface of the semiconductor substrate opposite to the first surface, with respect to the circular light-receiving portion formed on the first surface of the semiconductor substrate to generate a photocurrent. It is a back-illuminated light receiving element that allows light to enter the
    The circular light receiving section is divided by a plurality of linear isolation grooves extending from the center of the circular light receiving section so that the light receiving area is equal to each other, and includes a plurality of photodiodes connected in series by a plurality of conductive members. Equipped with
    On the second surface side of the semiconductor substrate, there is a conical recess formed by recessing the semiconductor substrate into a conical shape whose diameter decreases toward the first surface, and the axis of symmetry of the conical recess is aligned with the circular light receiving section. formed to pass through the center,
    The light incident from the second surface side is converted into an annular shape by the conical recess, and an equal amount of light is incident on each of the plurality of photodiodes of the circular light receiving section. Optical power converter.
  2. 　前記光ファイバケーブルを介して入力される光を平行光に変換して前記円錐状凹部に入射させるコリメータレンズを備えたことを特徴とする請求項１に記載の光給電コンバータ。 The optical power supply converter according to claim 1, further comprising a collimator lens that converts the light input through the optical fiber cable into parallel light and makes it enter the conical recess.
  3. 　前記円錐状凹部は、この円錐状凹部に入射した光を、前記円形受光部の直径以下の外径、且つ前記複数の直線状のアイソレーション溝が前記円形受光部の周方向に連なって形成された無効領域の外径よりも大きい内径を有する円環状に変換するように形成されたことを特徴とする請求項１又は２に記載の光給電コンバータ。
          The conical recess is formed such that the outer diameter of the conical recess is less than or equal to the diameter of the circular light receiving part, and the plurality of linear isolation grooves are continuous in the circumferential direction of the circular light receiving part, so that the light incident on the conical recess is 3. The optical power feeding converter according to claim 1, wherein the optical power feeding converter is formed to have an annular shape having an inner diameter larger than an outer diameter of the ineffective region.
PCT/JP2022/024829 2022-06-22 2022-06-22 Optical power feed converter WO2023248372A1 (en)

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JPH02224375A (en) * 1989-02-27 1990-09-06 Toshiba Corp Solar cell module
JPH10117012A (en) * 1996-10-11 1998-05-06 Sumitomo Electric Ind Ltd Semiconductor light-receiving element
US20110108082A1 (en) * 2006-12-20 2011-05-12 Jds Uniphase Corporation Multi-Segment Photovoltaic Power Converter With A Center Portion
CN102184999A (en) * 2011-04-02 2011-09-14 中国科学院苏州纳米技术与纳米仿生研究所 NPN-structure-based laser photovoltaic cell and preparation process thereof
CN104037178A (en) * 2013-03-07 2014-09-10 中国科学院苏州纳米技术与纳米仿生研究所 GaAs laser photovoltaic cell with output voltage being 5V and making method thereof
US20140318620A1 (en) * 2013-04-28 2014-10-30 Jordin T. Kare Device for Converting Electromagnetic Radiation into Electricity, and Related Systems and Methods

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02224375A (en) * 1989-02-27 1990-09-06 Toshiba Corp Solar cell module
JPH10117012A (en) * 1996-10-11 1998-05-06 Sumitomo Electric Ind Ltd Semiconductor light-receiving element
US20110108082A1 (en) * 2006-12-20 2011-05-12 Jds Uniphase Corporation Multi-Segment Photovoltaic Power Converter With A Center Portion
CN102184999A (en) * 2011-04-02 2011-09-14 中国科学院苏州纳米技术与纳米仿生研究所 NPN-structure-based laser photovoltaic cell and preparation process thereof
CN104037178A (en) * 2013-03-07 2014-09-10 中国科学院苏州纳米技术与纳米仿生研究所 GaAs laser photovoltaic cell with output voltage being 5V and making method thereof
US20140318620A1 (en) * 2013-04-28 2014-10-30 Jordin T. Kare Device for Converting Electromagnetic Radiation into Electricity, and Related Systems and Methods

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