JP7178153B1 - optical power converter - Google Patents

Abstract

An object of the present invention is to provide an optical power supply converter that allows input light input from a plurality of optical fiber cables to enter a semiconductor light receiving element so that the light intensity does not increase. An optical power supply converter (1) includes a plurality of lenses (6) corresponding to a plurality of input lights (L1) input through a plurality of optical fiber cables (30) and a light receiving area for generating a photocurrent. (12), each of the lenses (6) has a convex lens surface (6a) into which the input light (L1) is input and a conical lens surface (6b) facing the light receiving area (12), and a conical lens The symmetry axis (6c) of the surface (6b) is formed so as to pass through the center of the convex lens surface (6a) perpendicularly, and the plurality of lenses (6) are arranged such that the symmetry axis (6c) is aligned with the center axis ( 12a), and each of the plurality of input lights (L1) intersects the central axis (30a) of the optical fiber cable at a predetermined angle at the inclined end surface (31). Annular light (L2) reflected in the direction of (12a) is input to the corresponding lens (6), and emitted from the plurality of lenses (6) enters the light receiving area (12) without intersecting each other. configured to

Description

TECHNICAL FIELD The present invention relates to an optical power supply converter that converts light input via an optical fiber cable into electric power and supplies power.

In special environments, such as remote locations without power supply facilities, environments where weak electromagnetic fields from power supply become noise, environments requiring explosion protection, and ultra-high voltage facilities with electrical mutual influence, electronic devices can be connected via power cables. may not be able to supply power to operate Therefore, an optical power supply converter is used that receives light input through an optical fiber cable to the vicinity of electronic equipment, generates a photocurrent through photoelectric conversion, and supplies power.

If the optical power converter is required to supply a large amount of power, it is effective, for example, to increase the optical input. However, in a general single-mode optical fiber cable, the diameter of the core through which light propagates is as small as about 10 μm, so the core may be damaged by the fiber fuse phenomenon when a large optical input exceeds 1 W, for example. Therefore, as in Patent Documents 1 and 2, for example, the use of a plurality of optical fiber cables to input light is being studied.

In Patent Document 1, a concave reflecting mirror that utilizes the properties of a paraboloid collects light input through a plurality of optical fiber cables to the focal point of the paraboloid, and a light receiving element photoelectrically converts this light. are described. Further, in Patent Document 2, a concave reflector utilizing the properties of the ellipsoid of revolution collects light input through a plurality of optical fiber cables to the focal position of the ellipsoid of revolution, and this light is received by a light-receiving element. Techniques for converting and powering are described.

Japanese Patent No. 6928992 Japanese Patent No. 6937538

The light input through the optical fiber cable is a conical beam whose irradiation area widens as it travels after being emitted from the output end of the optical fiber cable. The light intensity distribution of this light is generally a Gaussian distribution, in which the light intensity decreases as the distance from the optical axis increases, and the light intensity distribution is rotationally symmetrical with respect to the optical axis.

When Gaussian-distributed light emitted from a plurality of optical fiber cables is collected at the focal position as in Patent Documents 1 and 2, the light on the optical axis with the highest light intensity overlaps at the focal position. Therefore, the light intensity becomes too high at and near this focal position, and the semiconductor light receiving element that receives this light suffers a drop in efficiency of photoelectric conversion due to, for example, space charge effect, temperature rise, etc. There is a risk that the ability will decrease.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical power supply converter capable of causing light input via a plurality of optical fiber cables to enter a semiconductor light receiving element without increasing the light intensity.

According to the first aspect of the present invention, there is provided an optical power supply converter that generates and supplies photocurrents from a plurality of input lights input via a plurality of optical fiber cables, wherein a plurality of photocurrents corresponding to the plurality of input lights are provided. a semiconductor light receiving element having a lens and a light receiving area for generating a photocurrent, each of the lenses having a convex lens surface to which the input light is input and a conical lens surface facing the light receiving area; The axis of symmetry of the surface is formed so as to pass through the center of the convex lens surface perpendicularly to the convex lens surface, and the plurality of lenses are formed so that the axis of symmetry passes through the center of the light receiving area perpendicular to the light receiving area. Each of the plurality of input lights is arranged at intervals so as to coincide with the central axis, and each of the plurality of input lights is directed in the central axis direction at the inclined end surface of the optical fiber cable that intersects the central axis of the optical fiber cable at a predetermined angle. a plurality of annular light beams, which are reflected by the lens, are input to the corresponding lenses, and are respectively emitted from the conical lens surfaces of the plurality of lenses, and are incident on the light receiving area without intersecting each other. It is characterized by

According to the above configuration, each of the plurality of lenses has a convex lens surface to which the input light is input via the optical fiber cable, and a conical lens surface facing the light receiving area. Input light enters the corresponding lens. When the plurality of input lights are emitted from the conical lens surface, they are converted into annular lights, and enter the light receiving area of the semiconductor light receiving element without intersecting each other. Therefore, the input light that is input via a plurality of optical fiber cables can be made incident on the semiconductor light-receiving element so that the light intensity does not increase.

According to a second aspect of the invention, there is provided an optical feeding converter according to the first aspect of the invention, wherein the convex lens surfaces of the plurality of lenses have the same radius of curvature and the conical lens surfaces have the same apex angles. .
According to the above configuration, since only one type of lens is used, it is possible to easily form the optical feeding converter and reduce the manufacturing cost thereof.

According to a third aspect of the invention, there is provided an optical feeding converter according to the first aspect of the invention, wherein at least one of the plurality of lenses has a radius of curvature of the convex lens surface different from that of the other lenses.
According to the above configuration, it is possible to adjust the inner diameter of the annular light with a different radius of curvature so that the multiple annular lights do not cross each other and do not enter other lenses. Therefore, the input light that is input via a plurality of optical fiber cables can be made incident on the semiconductor light-receiving element so that the light intensity does not increase.

According to the invention of claim 4, in the invention of claim 1, at least one of the plurality of lenses is characterized in that the apex angle of the conical lens surface is different from that of the other lenses. .
According to the above configuration, it is possible to adjust the outer diameter and inner diameter of the annular light beams by different apex angles so that a plurality of annular light beams do not cross each other and do not enter other lenses. Therefore, the input light that is input via a plurality of optical fiber cables can be made incident on the semiconductor light-receiving element so that the light intensity does not increase.

A fifth aspect of the present invention provides an optical power feeding converter according to the first aspect of the invention, wherein the light receiving area comprises a plurality of photodiodes equally divided in the circumferential direction by a plurality of isolation grooves radially extending from the center of the light receiving area. It is characterized by being formed by being connected in series.
According to the above configuration, in order to increase the output voltage, a plurality of annular light beams can be made concentrically and evenly incident on the plurality of photodiodes whose light receiving areas are equally divided in the circumferential direction and connected in series. can. Therefore, it is possible to reduce variations in the photocurrents of the plurality of photodiodes and improve the output of the optical power supply converter.

In the optical feed converter of the invention of claim 6, in the invention of claim 1, the lens farthest from the light receiving area has an output end surface perpendicular to the central axis of the optical fiber cable arranged along the central axis. It is characterized in that it is configured such that the input light can be input from.
According to the above configuration, it is possible to easily adjust the distance between the lens furthest from the light receiving area and the output end face of the optical fiber cable that inputs light to this lens without changing the size of the optical power supply converter. Therefore, by adjusting this distance, it is possible to adjust the inner diameter of the annular light emitted from this lens, so that it is possible to facilitate the design of the optical feeding converter.

According to the optical power supply converter of the present invention, input light that is input via a plurality of optical fiber cables can be made incident on the semiconductor light receiving element so that the light intensity does not increase.

1 is a perspective view of an optical feeding converter according to an embodiment of the present invention; FIG. FIG. 2 is an explanatory diagram of the inside of the optical feeding converter of FIG. 1; 2 is a cross-sectional view including the central axis of the light receiving region of the optical power feeding converter of FIG. 1; FIG. FIG. 4 is an explanatory diagram of arrival positions of light rays included in input light input to a lens; 3 is an intensity distribution diagram of input light; FIG. It is an example of the graph which shows the relationship between the base angle of the conical lens surface of a lens, and the outer diameter of the annular light which injects into a light-receiving area. It is an example of the graph which shows the relationship between the curvature radius of the convex-lens surface of a lens, and the internal diameter of the annular light which injects into a light-receiving area|region. FIG. 10 is an example of a graph showing, in contour lines, the inner diameter of an annular light incident on a light receiving region using the radius of curvature of the convex lens surface of the lens and the base angle of the conical lens surface as parameters. It is an example of the graph which shows the relationship between the radius of curvature of the convex lens surface of a lens, and the inner diameter and outer diameter of the annular light which injects into a light-receiving area. It is a figure which shows an example in which three circular light beams inject into a light-receiving area by three lenses. FIG. 11 is a diagram showing an example in which three annular lights are incident on a light receiving area when the lens in FIG. 10 is an axicon lens; It is a figure which shows one example in which four circular light beams inject into a light-receiving area by four lenses. FIG. 10 is a diagram showing an example of a light receiving region formed by connecting a plurality of equally divided photodiodes in the circumferential direction in series; 14 is a cross-sectional view taken along line XIV-XIV of FIG. 13; FIG. FIG. 4 is a diagram showing a modification of the optical feeding converter of FIG. 3;

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on an Example.

As shown in FIGS. 1 and 2, a plurality of input lights L1 are input to the optical feeding converter 1 via a plurality of single-mode optical fiber cables 30, for example. This optical power supply converter 1 converts a plurality of input lights L1 into photocurrents and supplies power to the outside. For this purpose, the optical power supply converter 1 includes a semiconductor light receiving element 10 for generating a photocurrent, a base 2 in which the semiconductor light receiving element 10 is fixed to the accommodating portion 2a, and a power supply 1 mounted on the base 2. It has a pair of output terminal portions 3 a and 3 b and a cover 4 fixed to the base 2 so as to protect the semiconductor light receiving element 10 . An example in which light is input via two optical fiber cables 30 will be described below.

The semiconductor light receiving element 10 has a light receiving region 12 for generating a photocurrent by photoelectric conversion, and a pair of electrodes 10a and 10b for outputting the photocurrent generated in the light receiving region 12. FIG. A pair of electrodes 10a, 10b are connected to corresponding output terminals 3a, 3b by, for example, conductive wires 11a, 11b.

The cover 4 is formed by stacking a plurality of cover modules 5 corresponding to a plurality of optical fiber cables 30 . Each cover module 5 has, for example, a rectangular cylindrical peripheral wall portion 5a and a partition wall portion 5b that partitions the space inside the peripheral wall portion 5a into a knot-like shape perpendicular to the axial direction of the peripheral wall portion 5a. A notch portion 5c is formed in the peripheral wall portion 5a so that the outside of the peripheral wall portion 5a and one of the inner sides of the peripheral wall portion 5a partitioned by the partition wall portion 5b (the side opposite to the base 2) communicate with each other. . The optical fiber cable 30 is inserted into the cover module 5 through the notch 5c and fixed. An opening penetrating through the peripheral wall portion 5a may be formed instead of the notch portion 5c. Moreover, the peripheral wall portion 5a may be formed in a cylindrical shape other than a rectangular shape, for example, a circular or polygonal shape.

The partition wall portion 5b of the cover module 5 is made of a synthetic resin or glass transparent to the input light L1 and formed into a plate shape having a thickness of, for example, 100 μm, and is fitted and fixed inside the peripheral wall portion 5a. The partition portion 5b has a lens mounting hole formed so as to penetrate the partition portion 5b. A lens 6 is mounted and fixed in this lens mounting hole.

As shown in FIGS. 3 and 4, the lens 6 has a convex lens surface 6a and a conical lens surface 6b as lens surfaces having a diameter of 300 μm, for example. The lens 6 is made of optical glass having a refractive index of, for example, about 1.45 with respect to air. The axis of symmetry 6c of the conical lens surface 6b passes through the center of the convex lens surface 6a perpendicularly to this convex lens surface 6a. The lens 6 is mounted on the partition wall 5b so that the convex lens surface 6a faces the notch 5c of the cover module 5 to which the lens 6 is attached, with the axis of symmetry 6c perpendicular to the flat partition wall 5b. It is fixed to the lens mounting part.

The lens mounting hole is formed, for example, in the center of the partition wall 5b so that the plurality of lenses 6 are arranged in a row in the axial direction of the peripheral wall 5a when the cover 4 is formed by stacking the plurality of cover modules 5. . The cover 4 is fixed to the base 2 so that the symmetry axes 6c of the plurality of lenses 6 coincide with the center axis 12a passing through the center C of the light receiving area 12 perpendicularly to the light receiving area 12, respectively. The cover 4 may be formed by stacking and fixing a plurality of cover modules 5 to the base 2 .

A typical single-mode optical fiber cable has a strand composed of a core through which light propagates and a clad that wraps around the core and confines the light in the core. The strands are then covered with, for example, two layers of protective coating to form an optical fiber cable. An optical fiber cable 30 in a bare wire state from which the coating is removed is inserted into the optical feeding converter 1 . The input light L1 input through the optical fiber cable 30 is infrared light with a wavelength of about 1.5 μm, for example.

At the tip of the optical fiber cable 30 inserted parallel to the partition wall portion 5b from the notch portion 5c, an inclined end surface 31 is formed that intersects the central axis 30a of the optical fiber cable 30 at a predetermined angle of 45°. ing. A reflective film is formed on the inclined end face 31 by depositing a metal such as gold or aluminum.

The optical fiber cable 30 is fixed to the optical power supply converter 1 in such an attitude that the central axis 30a of the inclined end surface 31 is orthogonal to the central axis 12a and the inclined end surface 31 faces the opposite side of the light receiving area 12. FIG. Light propagating through the core along the central axis 30 a of the optical fiber cable 30 is reflected by the inclined end surface 31 in the direction of the central axis 12 a toward the light receiving area 12 and emitted from the optical fiber cable 30 . This emitted light is input to the convex lens surface 6a of the corresponding lens 6 as the input light L1. In order to facilitate insertion of a plurality of bundled optical fiber cables 30, it is preferable to arrange the cutouts 5c in a row, but the arrangement is not limited to this.

The input light L1 is, as shown in FIG. 5, a beam that spreads conically with an apex angle θ. The light intensity distribution of this input light L1 is generally a Gaussian distribution, 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. The outermost periphery of the input light L1 is defined as the point where the light intensity is ¹ /e2 of the light intensity on the optical axis OA, and the apex angle θ of the outermost periphery is 14°.

The arrival position of the light ray R1 included in the input light L1 in the light receiving region 12 will be described with reference to FIG.
Let R be the radius of curvature of the convex lens surface 6a of the lens 6, and α be the apex angle of the conical lens surface 6b. The cross section of the conical lens surface 6b including the axis of symmetry 6c is an isosceles triangle, and the base angle of this isosceles triangle is defined as the base angle β of the conical lens surface 6b. β=(180°-α)/2, and the apex angle α and the base angle β are determined simultaneously. Also, on the central axis 12a of the light receiving area 12, the distance between the emitting point of the light ray R1 and the convex lens surface 6a is S1, and the distance between the convex lens surface 6a and the light receiving area 12 is S2. Incidentally, the length of the lens 6 on the axis of symmetry 6c is, for example, 200 μm.

A light ray R1 emitted in a direction inclined by an angle φ with respect to the central axis 12a is refracted when incident on the convex lens surface 6a, and is refracted again by the conical lens surface 6b to be emitted. A light beam R1 emitted from the lens 6 intersects the center axis 12a and enters the light-receiving region 12 at a distance d from the center C thereof.

All rays included in the input light L1 cross the central axis 12a by the lens 6 and enter the light receiving region 12. FIG. Accordingly, as shown in FIG. 3, the input light L1 is converted into an annular light L2 by the lens 6 and travels toward the light receiving area 12 while spreading. The annular light L2 is partially blocked by the optical fiber cable 30 arranged between the emitted lens 6 and the light receiving area 12, but most of it enters the light receiving area 12. FIG. Also, the ring-shaped light L2 is refracted when passing through the partition 5b, but since the effect is small, the refracting in the partition 5b is omitted from the illustration.

The light on the optical axis of the input light L1 corresponding to the angle φ=0° becomes the circular outer peripheral portion of the light L2, and the light on the outer peripheral portion of the input light L1 corresponding to the angle φ=θ/2 becomes circular. It becomes the inner periphery of the light L2. When the distances S1 and S2 are determined, the outer diameter Do of the annular light L2 is determined by the apex angle α (base angle β) of the conical lens surface 6b. When the distances S1 and S2 are determined, the inner diameter Di of the annular light L2 is determined by the radius of curvature R of the convex lens surface 6a and the vertical angle α (base angle β) of the conical lens surface 6b.

FIG. 6 shows the relationship between the base angle β of the conical lens surface 6b and the outer diameter Do of the annular light L2 in the light receiving area 12, with the distance S1=800 μm, the distance S2=2000 μm, and the radius of curvature R of the convex lens surface 6a= An example for 600 μm is shown. The larger the base angle β of the conical lens surface 6b, the larger the outer diameter Do of the annular light L2.

FIG. 7 shows the relationship between the radius of curvature R of the convex lens surface 6a and the inner diameter Di of the annular light L2 in the light receiving area 12. , the base angle β of the conical lens surface 6b is 35° (apex angle α=110°). The larger the radius of curvature R of the convex lens surface 6a, the smaller the inner diameter Di of the annular light L2.

FIG. 8 shows the light receiving area 12 when the apex angle θ of the input light L1 is 14°, the distance S1 is 800 μm, and the distance S2 is 2000 μm, using the curvature radius R of the convex lens surface 6a and the base angle β of the conical lens surface 6b as parameters. is an example in which the inner diameter Di of the annular light L2 in is shown in the form of contour lines. Using FIG. 8, it is possible to determine the combination of the radius of curvature R and the base angle β that provides the desired inner diameter Di. Then, using the same diagram with the distances S1 and S2 changed, it is possible to determine the combination of the radius of curvature R and the base angle β of the plurality of lenses 6.

FIG. 9 shows the relationship between the curvature radius R of the convex lens surface 6a and the outer diameter Do and inner diameter Di of the annular light L2 in the light receiving area 12, with respect to the apex angle θ of the input light L1=14°, the distance An example in which S2=2500 μm and the base angle β of the conical lens surface 6b=35° is shown. Since the base angle β is fixed, the outer diameter Do is constant regardless of the radius of curvature R. On the other hand, the larger the curvature radius R, the smaller the inner diameter Di. The difference between the outer diameter Do and the inner diameter Di is the beam width in the radial direction of the annular light L2 in the light receiving area 12, and the beam width increases as the radius of curvature R increases.

As shown in FIG. 3, in the optical power converter 1, a plurality of lenses 6 each having a determined combination of radius of curvature R and base angle β are arranged at intervals so as to be aligned on the central axis 12a. ing. The distance between the multiple lenses 6 is set based on the distances S1 and S2 of each lens 6 . Assuming that the lenses 6 are the first lens 6 and the second lens 6 in descending order from the light receiving area 12, the distances S1 and S2 of the first lens 6 are, for example, 300 μm and 700 μm, and the distances S1 and S2 of the second lens 6 S2 is, for example, 800 μm and 2500 μm. Each of the first and second lenses 6 has an apex angle α of, for example, 110° and a curvature radius R of, for example, 600 μm.

A plurality of input lights L<b>1 are input via a plurality of optical fiber cables 30 corresponding to a plurality of lenses 6 . The plurality of annular lights L2 emitted from the plurality of lenses 6 enter the light receiving area 12 concentrically with respect to the center C thereof without intersecting each other and without entering the adjacent lenses 6 . Therefore, the plurality of annular light beams L2 do not overlap in the light receiving region 12, and the input light beam L1 input via the plurality of optical fiber cables 30 is directed to the light receiving region 12 of the semiconductor light receiving element 10 so that the light intensity does not increase. can be made incident on

When the number of lenses 6 is one as shown in FIG. 3, the manufacturing cost of the optical power supply converter 1 can be reduced. Although not shown, if one type of lens 6 and one type of cover module 5 are used, the cover 4 can be easily formed, and the manufacturing cost of the optical power supply converter 1 can be further reduced. Also, it is possible to easily cope with an increase in the number of optical fiber cables 30 .

FIG. 10 shows how light is incident when the optical feeding converter 1 has three lenses 6 . The three lenses 6 are referred to as a first lens 6, a second lens 6, and a third lens 6 in order from the side closest to the light receiving area 12. FIG. The distance S1 between the first and second lenses 6 is set at 300 μm, and the distance S1 between the third lens 6 is set at 800 μm. Also, the distances S2 of the first to third lenses 6 are set to 500 μm, 1300 μm and 2000 μm, respectively. Optical fiber cables corresponding to the three lenses 6 are omitted.

The convex lens surface 6a of the first to third lenses 6 has a common radius of curvature R of 300 μm. smaller than the angle α (α′=105°, α=110°). Therefore, the third lens 6 farthest from the light receiving area 12 can spread the annular light L2 more than the other two lenses 6 can. Therefore, the third lens 6 receives light without allowing the plurality of annular light beams L2 to intersect with each other and without allowing the annular light beam L2 emitted from the third lens 6 to enter another lens 6. It is possible to reduce the size of the optical power supply converter 1 by bringing it closer to the area 12 .

FIG. 11 shows how light is incident when the radii of curvature R of the convex lens surfaces 6a of the three lenses 6 in FIG. 10 are infinite, that is, when the first to third lenses 6 are axicon lenses. ing. Although the apex angles of the multiple conical lens surfaces 6b are the same as in FIG. 10, the inner peripheral side portion of the light L2' converted into an annular shape by the axicon lens enters the adjacent axicon lens. Therefore, it can be seen from FIGS. 10 and 11 that the inner diameter Di of the annular light L2 is increased by decreasing the curvature radius R of the convex lens surface 6a. Since the plurality of lenses 6 can be brought closer to the light receiving area 12 by increasing the inner diameter Di, the optical feeding converter 1 can be miniaturized by the convex lens surfaces 6a of the lenses 6. FIG.

FIG. 12 shows an example of how light is incident on the optical feeding converter 1 having four lenses 6 . The four lenses 6 are referred to as a first lens 6, a second lens 6, a third lens 6, and a fourth lens 6 in order from the side closer to the light receiving area 12. As shown in FIG. The diameter of the lens surface of the lens 6 closer to the light receiving area 12 is made smaller so that the annular light L2 does not enter from the adjacent lens 6 on the opposite side of the light receiving area 12 . Also, optical fiber cables corresponding to the four lenses 6 are omitted.

The first and second lenses 6 are axicon lenses in which the radius of curvature R of the convex lens surface 6a' is infinite. The curvature radius R of the convex lens surface 6a of the third lens 6 is 1000 μm, and the curvature radius R of the convex lens surface 6a of the fourth lens 6 is 800 μm. The apical angles α of the conical lens surfaces 6b of the first, second and fourth lenses 6 are 104°, respectively, and the apical angle α' of the conical lens surfaces 6b of the third lens 6 is 103°.

The distance S1 of the first to third lenses 6 is set to 300 μm, and the distance S1 of the fourth lens 6 is set to 800 μm. The distances S2 of the first to fourth lenses 6 are set to 300 μm, 800 μm, 1400 μm and 2100 μm.

By appropriately setting the radius of curvature and apex angle that determine the shape of the plurality of lenses 6, and the distances S1 and S2, the plurality of annular lights L2 in the light receiving area 12 do not cross each other as shown in FIG. Moreover, the gap between the annular lights L2 can be reduced. Therefore, the input light L1 input through the plurality of optical fiber cables 30 can be concentrically incident on the light receiving region 12 of the semiconductor light receiving element 10 so that the light intensity does not increase.

The light receiving region 12 is, for example, a single PIN photodiode with a light absorbing layer. Since the plurality of annular lights L2 are photoelectrically converted in the light receiving area 12, a large photocurrent is output at a low voltage. However, depending on the power supply destination, a small current may be sufficient, but a high voltage may be required. In such a case, as shown in, for example, FIGS. A region 12 is divided into a plurality of photodiodes 14 . Here, a circular light-receiving region 12 is equally divided in the circumferential direction by 30 isolation grooves 13 to form 30 photodiodes 14 .

The light-receiving region 12 is electrically separated from its outside by an isolation groove 15 formed on the outer periphery. A plurality of electrically separated photodiodes 14 are connected in series by a conductive member 25, except for some of the photodiodes 14 whose part of the annular light L2 is blocked by the optical fiber cable 30. there is 7, the reference numerals of the isolation groove 13, the photodiode 14, and the conductive member 25 are partially omitted.

In the vicinity of the center C of the light-receiving region 12, a plurality of isolation grooves 13 are densely arranged and adjacent isolation grooves 13 are connected in the width direction. As a result, a plurality of isolation grooves 13 are connected in the circumferential direction to form a regular polygonal region I in which the width of the isolation groove 13 is the width of one side and in which a photocurrent cannot be generated.

The photodiode 14 has, for example, a first conductivity type first semiconductor layer 21 laminated on a semi-insulating semiconductor substrate 20 , a light absorption layer 22 , and a second conductivity type second semiconductor layer 23 . The semiconductor substrate 20 is, for example, an InP substrate, the first semiconductor layer 21 is, for example, an n-InP layer, the light absorption layer 22 is, for example, an InGaAs layer, and the second semiconductor layer 23 is, for example, a p-InP layer. It is not limited to this. Also, the photodiode 14 is not limited to the PIN type. The thicknesses of the first semiconductor layer 21, the light absorption layer 22, and the second semiconductor layer 23 can be appropriately set, and are often formed to a thickness of about 0.5 to 10 μm.

The isolation groove 13 is formed by etching the semiconductor substrate 20 in which the first semiconductor layer 21, the light absorption layer 22, and the second semiconductor layer 23 are laminated from the second semiconductor layer 23 side so that the semiconductor substrate 20 is exposed. be done. As a result, the light receiving region 12 is divided into a plurality of electrically separated photodiodes 14 . The isolation groove 13 may be formed with an inclined side wall so that the width becomes narrower toward the semiconductor substrate 20 side, for example.

The plurality of photodiodes 14 each have a connection hole 17 that penetrates the second semiconductor layer 23 and the light absorption layer 22 and reaches the first semiconductor layer 21 . Then, an insulating protective film 24 is formed so as to cover the surfaces of the plurality of photodiodes 14 and the side walls of the connection holes 17 of the photodiodes 14 and to fill the plurality of linear isolation grooves 13 and 15 . It is The protective film 24 preferably has an antireflection function of light, but an antireflection film (not shown) may be further formed.

In each photodiode 14, the protective film 24 on the second semiconductor layer 23 and inside the connection hole 17 is partially removed, exposing the first semiconductor layer 21 at the second semiconductor layer 23 and the bottom of the connection hole 17, respectively. . Then, in order to connect the plurality of photodiodes 14 in series, excluding some of the photodiodes 14 where part of the annular light L2 is blocked, between the photodiodes 14 adjacent to each other via the isolation groove 13, The second semiconductor layer 23 exposed on one side and the first semiconductor layer 21 exposed on the other side are connected by a conductive member 25 . Conductive members 25 at both ends of the plurality of photodiodes 14 connected in series are connected to corresponding electrodes 10a and 10b.

The conductive member 25 is formed by selectively depositing a metal laminate 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. Since the isolation trenches 13 and 15 are filled with the protective film 24 to reduce the difference in level, the formation of the conductive member 25 is facilitated.

The isolation trench 13 does not need to be completely filled with the protective film 24, and it is sufficient if the step is small enough to form the conductive member 25. FIG. Although not shown, in each photodiode 14, a first electrode connected to the first semiconductor layer 21 and a second electrode connected to the second semiconductor layer 23 are formed. , one first electrode and the other second electrode may be connected by a conductive member 25 . Also, although not shown, a conductive wire mainly composed of gold, for example, is used as the conductive member 25 to connect the first electrode on one side and the second electrode on the other side between the adjacent photodiodes 14 in the same manner as described above. may be connected.

A plurality of annular lights L2 enter the light receiving region 12 concentrically with respect to the center C of the light receiving region 12 . Therefore, since the light is evenly incident on the plurality of photodiodes 14 connected in series, the photocurrent output from the semiconductor light receiving element 10 is small, but the output voltage can be increased. can be fed with a high voltage. Further, since the light L2 is annular, it is possible to prevent the input light L1 from being wasted by preventing it from entering the region I in which the photocurrent cannot be generated. In addition, since the annular light L2 is uniformly incident, variations in the photocurrent generated by the plurality of photodiodes 14 connected in series are reduced, and the photocurrent is limited by the photodiode 14 with the smallest photocurrent. Therefore, it is possible to suppress a decrease in photocurrent due to an increase in the photocurrent and improve the output.

As shown in FIG. 15, since the cover module 5 has a cylindrical shape, an optical fiber cable 32 having an output end surface 33 orthogonal to the central axis 32a is attached to the lens 6 farthest from the light receiving area 12 so that the central axis 32a is aligned with the central axis. 12a. In this case, the distance S1 between the lens 6 farthest from the light receiving area 12 and the emission point of the input light L1 input to this lens 6 can be easily adjusted without changing the size of the optical power feeding converter 1. FIG. Since the inner diameter Di of the annular light L2 can be adjusted by adjusting the distance S1 in addition to the radius of curvature R and the apex angle α of the lens 6, the degree of freedom of optical design in the optical feeding converter 1 increases. It is possible to make the design easier when miniaturizing the optical power feeding converter 1 .

The operation and effects of the optical power supply converter 1 will be described.
Each of the plurality of lenses 6 of the optical feeding converter 1 has a convex lens surface 6a into which the input light L1 is input, and a conical lens surface 6b facing the light receiving area 12, along the axis of symmetry 6c of the conical lens surface 6b. Input light L1 is input to the corresponding lens 6 . A plurality of input lights L1 incident on the corresponding lenses 6 are converted into annular lights L2 when emitted from the conical lens surface 6b, respectively, and enter the light receiving area 12 of the semiconductor light receiving element 10 without intersecting each other. do. Therefore, the input light L1 input through the plurality of optical fiber cables 30 can be made incident on the semiconductor light receiving element 10 so that the light intensity does not increase.

When the radii of curvature R of the convex lens surfaces 6a of the plurality of lenses 6 are equal to each other and the apex angles α of the conical lens surfaces 6b are equal to each other, the number of lenses 6 becomes one type, which facilitates the formation of the optical feeding converter 1. Along with this, the manufacturing cost can be reduced. On the other hand, when at least one lens 6 out of the plurality of lenses 6 has a convex lens surface 6a with a radius of curvature R different from that of the other lenses 6, the plurality of annular lights L2 are prevented from intersecting each other and other lenses 6 The inner diameter Di of the annular light L2 can be adjusted by a different radius of curvature R so that it does not enter the lens 6 . Therefore, the input light L1 input via a plurality of optical fiber cables 30 can be made incident on the semiconductor light receiving element 10 so that the light intensity does not increase. 1 can be miniaturized.

In addition, when at least one lens 6 among the plurality of lenses 6 has a different apex angle α of the conical lens surface 6b from that of the other lenses 6, the plurality of annular light beams L2 are prevented from intersecting each other and other lenses 6 are arranged. The outer diameter Do and the inner diameter Di of the annular light L2 can be adjusted by a different apex angle α so as not to enter the lens 6 of the ring. Therefore, the input light L1 input via a plurality of optical fiber cables 30 can be made incident on the semiconductor light receiving element 10 so that the light intensity does not increase. 1 can be miniaturized.

When the light receiving region 12 is formed by connecting in series a plurality of photodiodes 14 equally divided in the circumferential direction by a plurality of isolation grooves 13 radially extending from the center C of the light receiving region 12, the photodiodes 14 are connected in series. A plurality of annular lights L2 can be concentrically and evenly incident on the plurality of photodiodes 14 connected to . Therefore, the output of the optical power supply converter 1 can be improved by reducing variations in photocurrents generated by the plurality of photodiodes 14 .

The lens 6 farthest from the light receiving area 12 can receive the input light L1 from the output end surface 33 orthogonal to the central axis 32a of the optical fiber cable 32 arranged along the central axis 12a. Therefore, the distance S1 between the lens 6 farthest from the light receiving area 12 and the output end surface 33 of the optical fiber cable 32 for inputting the input light L1 to the lens 6 can be easily adjusted without changing the size of the optical power supply converter 1. be able to. By adjusting the distance S1, the inner diameter Di of the annular light L2 emitted from the lens 6 can be adjusted.

The semiconductor light receiving element 10 may be of a back-illuminated type, and the base 2 may be flat. Since the annular light L2 spreads in the circumferential direction and the light intensity becomes low, even if it overlaps with other annular light L2 in the radial direction, the light intensity does not become too high. may be partially overlapped. An adapter member having a plurality of optical fiber cables 30 to be inserted into the optical power supply converter 1 may be attached to the optical power supply converter 1, and the laid optical fiber cables may be connected to this adapter member. In addition, those skilled in the art can implement various modifications to the above embodiment without departing from the scope of the present invention, and the present invention includes such modifications.

Reference Signs List 1: optical feed converter 2: bases 3a, 3b: output terminal portion 4: cover 5: cover module 5a: peripheral wall portion 5b: partition wall portion 5c: notch portion 6: lens 6a: convex lens surface 6b: conical lens surface 6c: Axis of symmetry 10: semiconductor light receiving elements 10a, 10b: electrodes 11a, 11b: conductive wire 12: light receiving region 12a: central axis 13: isolation groove 14: photodiode 20: semiconductor substrate 21: first semiconductor layer 22: light absorption Layer 23: Second semiconductor layer 24: Protective film 25: Conductive members 30, 32: Optical fiber cables 30a, 32a: Central axis 31: Inclined end surface 32: Output end surface L1: Input light L2: Annular light

Claims (6)

In an optical power supply converter that generates and supplies photocurrent from a plurality of input lights input via a plurality of optical fiber cables,
a plurality of lenses corresponding to the plurality of input lights, and a semiconductor light receiving element having a light receiving region for generating a photocurrent,
Each of the lenses has a convex lens surface into which the input light is input and a conical lens surface facing the light receiving area, and the axis of symmetry of the conical lens surface makes the center of the convex lens surface perpendicular to the convex lens surface. formed to pass through
the plurality of lenses are spaced apart so that the axes of symmetry are aligned with a central axis that passes through the center of the light receiving region perpendicularly to the light receiving region;
each of the plurality of input lights is reflected in the direction of the central axis by an inclined end surface of the optical fiber cable that intersects the central axis of the optical fiber cable at a predetermined angle, and is input to the corresponding lens;
An optical feeding converter, wherein a plurality of annular lights emitted from said conical lens surfaces of said lenses are incident on said light receiving area without intersecting each other. 2. The optical feed converter according to claim 1, wherein the convex lens surfaces of the plurality of lenses have the same radius of curvature and the conical lens surfaces have the same apex angle. 2. The optical feed converter according to claim 1, wherein at least one of the plurality of lenses has a radius of curvature of the convex lens surface different from that of the other lenses. 2. The optical feeding converter according to claim 1, wherein at least one of the plurality of lenses has a different apex angle of the conical lens surface from that of the other lenses. 2. The light-receiving region according to claim 1, wherein the light-receiving region is formed by connecting in series a plurality of photodiodes equally divided in the circumferential direction by a plurality of isolation grooves radially extending from the center of the light-receiving region. optical power converter. 3. The input light can be input to the lens farthest from the light receiving area from an output end face perpendicular to the central axis of the optical fiber cable arranged along the central axis. 2. The optical power converter according to 1.

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