JP7178154B1 - optical power converter - Google Patents

Abstract

Kind Code: A1 A circular light receiving part is equally divided radially about the center of a semiconductor light receiving element and is connected in series. To provide an optical feeding converter that can be incident. An optical power supply converter (1) for converting light (L1) input via an optical fiber cable into a photocurrent by a semiconductor light receiving element (10) and outputting the light, the semiconductor light receiving element (10) includes a semiconductor Light is incident on the circular light receiving portion 12 on the first surface 20a side of the substrate 20 from the second surface 20b side of the substrate 20, and the circular light receiving portion 12 is located at the center (C). a plurality of photodiodes (14) equally divided by a plurality of linear isolation grooves (13) extending from and connected in series; Corresponding to the portion (12), a conical recess (16) having a smaller diameter toward the first surface (20a) is formed. (14) was configured so that an equal amount of light was incident on each of them.

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 transmitted through an optical fiber cable to the vicinity of electronic equipment, generates a photocurrent through photoelectric conversion, and supplies power.

The optical feeding converter has a semiconductor photodetector for photoelectric conversion. The output voltage of this semiconductor photodetector is usually less than 1V. 2. Description of the Related Art When a device that receives 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 a circular light-receiving portion of a semiconductor light-receiving element into a plurality of fan-shaped photodiodes by isolation grooves and connecting these in series.

The output voltage of a semiconductor light-receiving element composed of a plurality of photodiodes divided and connected in series increases as the number of photodiodes increases. On the other hand, its output current becomes 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 that produces the minimum photocurrent from photoelectric conversion. Therefore, in order to make the photocurrents of the plurality of photodiodes equal to each other, the circular light receiving portion is equally divided so that the plurality of photodiodes have the same shape and the same area.

U.S. Pat. No. 5,342,451

In Patent Document 1, in order to divide the circular light-receiving portion into the same shape and the same area, a plurality of linear isolation grooves having a constant width are radially formed from the center of the circular light-receiving portion. A plurality of isolation grooves are concentrated near the center of the circular light receiving portion. As the number of divisions of the circular light receiving portion increases, that is, the number of isolation grooves increases, the adjacent isolation grooves become closer, and the plurality of isolation grooves extend in the width direction (circumferential direction) at positions separated from the center of the circular light receiving portion. become connected.

In this way, a plurality of isolation grooves are connected in the circumferential direction to form a regular polygonal region having a side equal to the width of the isolation groove near the center of the circular light receiving portion. Since photoelectric conversion cannot be performed in the isolation groove, this regular polygonal region is an ineffective region in which photocurrent cannot be generated. This invalid area increases as the number of divisions of the circular light receiving section increases.

Here, the light intensity distribution of incident light input via an optical fiber cable is generally a Gaussian distribution, and the light intensity decreases as the distance from the optical axis increases. is the light intensity distribution of In order to make this light equally incident on the circular light-receiving part which is equally divided so as to have the same shape and the same area, the light is directed so that the optical axis passes through the center of the circular light-receiving part perpendicularly to the circular light-receiving part. is incident.

However, the high-intensity portion of the incident light near the optical axis irradiates the ineffective region formed near the center of the circular light-receiving part, and is wasted without being converted into photocurrent. Can not do it.

Therefore, the present invention reduces wasted light among the light input through an optical fiber cable to a semiconductor light receiving element in which a circular light receiving portion is equally divided radially about the center and connected in series. It is an object of the present invention to provide an optical power feeding converter capable of allowing light to be incident evenly.

According to the first aspect of the present invention, there is provided an optical power supply converter in which light input via an optical fiber cable is converted into a photocurrent by a semiconductor light receiving element and output, wherein the semiconductor light receiving element is a first photocurrent on a semiconductor substrate. A back-illuminated light-receiving element that allows light to enter the circular light-receiving portion from the second surface side of the semiconductor substrate opposite to the first surface, with respect to the circular light-receiving portion formed on the surface side for generating a photocurrent. and the circular light receiving portion is divided by a plurality of linear isolation grooves extending from the center of the circular light receiving portion so that the light receiving areas are equal to each other, and is connected in series by a plurality of conductive members. and on the second surface side of the semiconductor substrate, a conical recess in which the semiconductor substrate is recessed in a conical shape whose diameter decreases toward the first surface side is formed along the axis of symmetry of the conical recess. is formed so as to pass through the center of the circular light receiving portion, and the light incident from the second surface side is converted into an annular shape by the conical concave portion, and is equal to each of the plurality of photodiodes of the circular light receiving portion. It is characterized in that it is configured so that the amount of light is incident.

According to the above configuration, the light that is input via the optical fiber cable is converted into an annular shape by the conical recess and enters the plurality of photodiodes evenly, thereby reducing variations in the output of the plurality of photodiodes. be able to. In addition, since it is possible to prevent annular light from entering the vicinity of the center of the circular light-receiving portion where a plurality of isolation grooves that do not generate photocurrent are concentrated, light that is wasted without being photoelectrically converted. can be reduced. Therefore, the photocurrent of the semiconductor light receiving element having a circular light receiving portion 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.

According to a second aspect of the invention, there is provided an optical power supply converter according to the first aspect of the invention, further comprising a collimator lens for converting the light input through the optical fiber cable into parallel light and making the light incident on the conical concave portion. Characterized by
According to the above configuration, the collimator lens converts the light traveling while expanding in a conical shape into parallel light, so that the incident angle to the conical concave portion can be made constant. Therefore, it is possible to easily set the distance between the optical fiber cable and the collimator lens so that the beam diameter of the parallel light matches the diameter of the circular light receiving portion so that the input light does not protrude from the circular light receiving portion. can. Therefore, all of the input light can be made incident on the circular light-receiving portion, so that the photocurrent of the semiconductor light-receiving element can be increased, and the power supplied by the optical power supply converter can be increased.

According to a third aspect of the present invention, there is provided an optical power supply converter according to the first or second aspect of the invention, wherein the conical concave portion emits light incident on the conical concave portion with an outer diameter equal to or less than the diameter of the circular light receiving portion and the plurality of is formed so as to be converted into an annular ring having an inner diameter larger than the outer diameter of the invalid region formed continuously in the circumferential direction of the circular light receiving portion.
According to the above configuration, all of the annular light converted by the conical concave portion enters the circular light receiving portion while avoiding the ineffective region formed near the center of the circular light receiving portion where photocurrent cannot be generated. Therefore, by causing all of the light input via the optical fiber cable to enter the conical concave portion, the light can be used without waste and the power supplied by the optical power supply converter can be increased.

According to the optical power supply converter of the present invention, of the light input through the optical fiber cable to the semiconductor light receiving element in which the circular light receiving part is equally divided radially about the center and connected in series, It is possible to reduce the amount of light that is different and make it enter evenly.

1 is a perspective view of an optical power supply converter according to Example 1 of the present invention; FIG. FIG. 2 is an explanatory diagram of light incident on a semiconductor light-receiving element included in the optical power supply converter of FIG. 1; 3 is a plan view showing a circular light receiving portion of the semiconductor light receiving element of FIG. 2; FIG. FIG. 4 is a cross-sectional view taken along line IV-IV of the semiconductor light receiving element of FIG. 3 fixed to a base; 4 is a light intensity distribution diagram of light input via an optical fiber cable; FIG. 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 the line VI-VI of FIG. 3; 4 is a graph showing contour lines of the inner diameter of an annular light with parameters being the angle of incidence of parallel light onto 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 portion. FIG. 10 is an explanatory diagram of another example of light that is incident on a semiconductor light receiving element and converted into an annular shape; FIG. 10 is an explanatory diagram of an etching mask for forming a conical concave portion; It is explanatory drawing which forms a conical recessed part by an etching. FIG. 10 is an explanatory diagram of light incident on the semiconductor light receiving element of the optical feeding converter according to the second embodiment of the present invention and converted into an annular shape; FIG. 12 is an explanatory diagram of another example of light that is incident on the semiconductor light receiving element of the optical power feeding converter according to the second embodiment and converted into an annular shape;

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

As shown in FIGS. 1 and 2, the optical power supply converter 1 converts light (incident light L1) input via, for example, a single-mode optical fiber cable OC into a photocurrent and feeds it to the outside. It has a pair of output terminal portions 2a and 2b. A base 3 equipped with a pair of output terminals 2a and 2b is provided with 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. are fixed respectively. The semiconductor light receiving element 10 is connected to corresponding output terminal portions 2a and 2b via wiring portions 3a and 3b in order to output the generated photocurrent.

The incident light L1 input through the optical fiber cable OC is infrared light with a wavelength of about 1.5 μm, for example. The incident light L1 is a conical beam whose irradiation range widens as it travels after being emitted from the emission end E of the optical fiber cable OC.

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 causes the light to 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 portion 12 that performs photoelectric conversion and receives light from the side opposite to the side on which the circular light-receiving portion 12 is formed.

The cover 5 is fixed to the base 3 so that the optical axis 6 a of the collimator lens 6 is perpendicular to the circular light receiving portion 12 of the semiconductor light receiving element 10 and passes through the center C of the circular light receiving portion 12 . The optical fiber cable OC is inserted into the insertion hole 5a of the cover 5 and fixed so that the output end E thereof is separated from the collimator lens 6 by a predetermined distance. At this time, the output end E is positioned such that the optical axis OA of the incident light L1 coincides with the optical axis 6a of the collimator lens 6. FIG.

As shown in FIGS. 3 and 4, the circular light-receiving section 12 is formed by, for example, a circular PIN-type photodiode provided with a light absorption layer, and is shaped by a plurality of linear isolation grooves 13 radially extending from the center C thereof. and equally divided into a plurality of fan-shaped photodiodes 14 having the same area. Here, a circular light receiving portion 12 is equally divided into 30 photodiodes 14 by 30 isolation grooves 13 .

A plurality of linear isolation grooves 13 are radially formed with a constant width from the center C of the circular light receiving portion 12 so as to form a plurality of fan-shaped photodiodes 14 having the same shape and light receiving area. 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 isolated by a plurality of isolation grooves 13 are connected in series by a conductive member 4 formed on the base 3 to form a circular light receiving portion 12 . The diameter of this circular light receiving portion 12 is assumed to be D1.

In this way, a plurality of fan-shaped photodiodes 14 having the same shape and light-receiving area are formed so as to surround the center C in the circular light-receiving section 12 . Since a photocurrent cannot be generated in the isolation groove 13, it is preferable to reduce the width of the isolation groove 13 and form it linearly so that the area of the isolation groove 13 in the area of the circular light receiving portion 12 is reduced. 3, the reference numerals of the isolation groove 13 and the photodiode 14 are partially omitted.

A plurality of linear isolation grooves 13 are concentrated in the vicinity of the center C of the circular light receiving portion 12 . Therefore, the adjacent isolation grooves 13 are closer to the center C side, and the plurality of isolation grooves 13 are connected in the width direction at positions separated from the center C. As shown in FIG. As a result, a plurality of isolation grooves 13 are connected in the circumferential direction of the circular light-receiving portion 12, and a regular polygonal region having sides equal to the width of the isolation grooves 13 is formed in the vicinity of the center C. FIG. Since photoelectric conversion cannot be performed in the isolation groove 13, this regular polygonal region is an ineffective region I in which a photocurrent cannot be generated. The invalid area I increases 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 has an n-type semiconductor layer 21 , a light absorption layer 22 and a p-type semiconductor layer 23 laminated on a first surface 20 a 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. Also, the photodiode 14 is not limited to the PIN type. The thicknesses of the n-type semiconductor layer 21, the light absorption layer 22, and the p-type semiconductor layer 23 can be appropriately set, and are often formed to a thickness of about 0.5 to 10 μm.

The isolation grooves 13 and 15 are formed 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 laminated from the p-type semiconductor layer 23 side so that the semiconductor substrate 20 is exposed. formed by Thereby, the circular light receiving portion 12 is divided into a plurality of electrically separated photodiodes 14 . The sidewalls of the isolation grooves 13 and 15 may be inclined so that the width of the isolation grooves 13 and 15 becomes narrower toward the semiconductor substrate 20, for example.

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 so as to cover the surfaces of the plurality of photodiodes 14 and the sidewalls 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 trenches 13 and annular isolation trenches 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 the protective film 24 at the bottom of the connection hole 17 is removed. It has a cathode electrode 28 connected to the exposed n-type semiconductor layer 21 . The anode electrode 27 and 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, thereby forming a plurality of circular light receiving portions 12. of photodiodes 14 are connected in series. Although illustration is omitted, instead of the conductive member 4, a plurality of photodiodes 14 may be connected in series by a conductive wire containing gold as a main component, for example, and selectively formed on the protective film 24. A plurality of photodiodes 14 may be connected in series by a plurality of wirings.

Since the circular light receiving portion 12 is formed by a plurality of fan-shaped photodiodes 14 connected in series, the photocurrent output from the semiconductor light receiving element 10 is small, but the output voltage can be increased. Therefore, the optical power supply converter 1, which includes the semiconductor light receiving element 10 and photoelectrically converts the incident light L1 input via the optical fiber cable OC to supply power, can supply power at a high voltage.

As shown in FIGS. 2 and 5, the incident light L1 emitted from the emission end E of the optical fiber cable OC travels while expanding in 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 a 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 /e2 of the light intensity on the optical axis OA.

As shown in FIG. 6, when the incident light L1 is incident on the collimator lens 6, the optical axis OA of the incident light L1 is aligned with the optical axis 6a of the collimator lens 6. As shown in FIG. The collimator lens 6 converts the incident light L 1 into parallel light L 2 and causes the collimated light L 2 to enter the back-illuminated semiconductor light receiving element 10 . The light intensity distribution of the parallel light L2 maintains the light intensity distribution when the incident light L1 enters the collimator lens 6. FIG.

The semiconductor light-receiving element 10 is arranged on the second surface 20b side (rear surface side) of the semiconductor substrate 20 facing the first surface 20a of the semiconductor substrate 20 on which the circular light-receiving portion 12 is formed, so that the diameter of the semiconductor light-receiving element 10 decreases toward the first surface 20a side. has a conical recess 16 formed by recessing the semiconductor substrate 20 in a conical shape. The conical recess 16 is formed so that the extension line (symmetry axis) of the axis of symmetry 16 a 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 6 a of the collimator lens 6 is positioned so as to pass through the center C of the circular light receiving portion 12 , so it coincides with the axis of symmetry of the conical concave portion 16 . Since the optical axis OA of the incident light L1 is aligned 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 is aligned with the symmetry axis of the conical concave portion 16. .

The parallel light L2 incident on the conical surface 16b of the conical concave portion 16 is refracted away from the optical axis OA and converted into an annular light L3. Let Db be the beam diameter of the parallel light L2 converted by the collimator lens 6 . Let Do be the outer diameter and Di be the inner diameter of the annular light L3 incident on the circular light receiving portion 12 separated by the distance T from the apex of the conical recess 16 .

Assuming that the inclination angle of the conical surface 16b of the conical concave portion 16 (the angle formed by the conical bottom surface and the generatrix) is α, the incident angle of the parallel light L2 to the conical surface 16b is α. Assuming that the refractive index of the semiconductor substrate 20 with respect to air is n, and the output angle of the parallel light L2 incident on the conical surface 16b is β, the following equation (1) holds from Snell's law.
β=sin ⁻¹ ((sin(α))/n) (1)
In the following explanation, n=3.2, but the refractive index n is not limited to this.

Assuming that the beam width in the radial direction when the annular light L3 converted by the conical concave portion 16 is incident on the circular light receiving portion 12 is t, this beam width is expressed by the following equation (2).
t=(Db/2)×(cos(β)/(cos(α)×cos(α−β)) (2)

The inner diameter Di and the outer diameter Do of the annular light L3 are given by the following equations (3) and (4).
Di=2×T×tan(α−β) (3)
Do=Di+2×t (4)

FIG. 7 shows contour lines of the inner diameter Di of the annular light L3 with the incident angle α and the distance T as parameters. If the incident angle α is constant, the inner diameter Di increases as the distance T increases. 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 .

By using FIG. 7 and the above formulas (1) to (4), 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 A 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.

Regarding the case where the inner diameter Di of the annular light L3 is set larger than the outer diameter D2 of the ineffective region I in order to reduce the waste of light input due to the light incident on the ineffective region 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 the photodiodes 14 is 30, the ineffective area I is a regular tridecagon with a side of 10 μm, so the length of the outer circumference is 300 μm. less than 100 μm.

If the inner diameter Di of the annular light L3 is set to 100 μm, for example, the incident angle α is 20° and the distance T is 470 μm from FIG. 1 degree. 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. Assuming that the outer diameter Do of the annular light L3 is 1200 μm so that all of the parallel light L2 enters the circular light receiving portion 12 having a diameter D1 of 1200 μm, for example, through the conical concave portion 16, the beam diameter Db of the parallel light L2 is becomes 1108 μm. As the predetermined distance, the distance between the collimator lens 6 and the output end E of the optical fiber cable OC is determined to be 4513 μm.

Since the outer diameter Do of the annular light L3 may be smaller than the diameter D1 of the circular light receiving portion 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 becomes small. , the optical power supply converter 1 can be miniaturized. 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 arbitrarily set, the smaller the distance, the more advantageous it is for miniaturization of the optical power supply converter 1 .

For example, as shown in FIG. 8, the portion of the parallel light L2 near the optical axis is made incident on the circular light receiving portion 12 via the conical recess 16, and the remaining portion of the parallel light L2 is converted into parallel light without passing through the conical recess 16. The light may be incident on the circular light receiving portion 12 as it is. In this case, annular light L<b>3 , which is a mixture of parallel light and light that spreads in the radial direction, is incident on the circular light receiving section 12 . At least part of the parallel light L2 that would be incident on the ineffective area I if the light remains parallel is changed in its traveling direction by the conical concave portion 16 so as to avoid the ineffective area I and be evenly incident on the circular light receiving portion 12. I wish I could. In particular, the closer to the ineffective area I, the greater the ratio of the isolation grooves 13 in the circumferential direction of the circular light-receiving section 12, and the more high-intensity light that is not photoelectrically converted. Useful when

In the case of FIG. 8, similarly to the above, the incident angle α and the distance T can be set by setting the inner diameter Di of the light that enters the conical concave portion 16 and forms an annular ring. For example, if the inner diameter Di is 150 μm and the incident angle α is 30°, the distance T is 480 μm, the shape and size of the conical recess 16 are determined, and the output angle β is 9°. At this time, the conical recess 16 on the second surface 20b has a diameter of 762 μm and a depth of 220 μm. Then, the outer diameter Do of the light that enters the conical concave portion 16 and becomes an annular ring is 1081 μm.

On the other hand, the beam diameter Db of the parallel light L2 can be arbitrarily set within a range larger than the diameter of the conical concave portion 16 and equal to or smaller than the diameter D1 of the circular light receiving portion 12 . The inner diameter of the annular light L3 in the circular light receiving portion 12 is either the inner diameter Di of the light that enters the conical recess 16 and becomes an annular ring or the diameter of the conical recess 16, depending on the shape and size of the conical recess 16. decided on one side. In addition, the outer diameter of the annular light L3 in the circular light receiving portion 12 depends on the shape and size of the conical concave portion 16, and the beam diameter Db of the parallel light L2 or the diameter of the light incident on the conical concave portion 16 and becoming circular. One of the diameters Do is determined.

Next, a method for forming the conical concave portion 16 will be described.
For example, as shown in FIG. 9, on the second surface 20b of the semiconductor substrate 20, an etching mask layer 30 having conical recesses 30a is formed. The conical recess 30a has an axis of symmetry 30b. The etching mask layer 30 is, for example, a photoresist that is recessed in a conical shape by continuously changing the thickness according to the difference in exposure dose.

Then, as shown in FIG. 10, for example, by reactive ion etching, the thinner the etching mask layer 30 is, the deeper the etching is performed to form the conical concave portion 16 reflecting the shape of the etching mask layer 30 . By aligning the axis of symmetry 30b with the center C of the circular light receiving portion 12 formed on the first surface 20a side of the semiconductor substrate 20, the axis of symmetry 16a is aligned with the center C of the circular light receiving portion 12 to form a conical concave portion. 16 are formed. The conical concave portion 16 may be formed by grinding and polishing the semiconductor substrate 20 into a conical shape with a whetstone or the like. Also, the conical recess 16 is formed on the second surface side 20b after forming the circular light receiving portion 12 on the first surface side 20a of the semiconductor substrate 20. A circular receiver 12 with C aligned may be formed.

A case where the collimator lens 6 of the optical feeding converter 1 of the first embodiment is omitted will be described with reference to FIG. The same reference numerals are given to the parts that are common to the first embodiment, and the description thereof will be omitted.
The semiconductor light receiving element 10 receives incident light L1 that is emitted from the output end E of the optical fiber cable OC and spreads in 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 portion 12, the incident light L1 is converted into an annular light L3′ by the conical concave portion 16 in the same manner as described above, and circular light is received. The light is made incident on the portion 12 .

The shape and size of the conical concave portion 16 are determined by setting the inner diameter Di, the incident angle α, and the distance T of the annular light L3' in the same manner as described above with respect to the light on the optical axis OA. For example, if the inner diameter Di is 150 μm and the incident angle α is 24°, the output angle β is 7.3°, the distance T is 580 μm 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 portion 12 via the conical recess 16 . The angle of incidence of the incident light L1 on the conical surface 16b decreases with distance from the optical axis OA, and the angle of incidence of the incident light L1 on the conical surface 16b at the outermost periphery is α-(θ/2). Moreover, the output angle γ thereof is smaller than the output angle β of the light on the optical axis OA. Then, the distance between the semiconductor light receiving element 10 and the emission end E 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.

For example, when .theta.=14.degree., the maximum distance between the output end E and the semiconductor light receiving element 10 is 2195 .mu.m in order to cause all of the incident light L1 to enter the conical concave portion 16 having a diameter of 539 .mu.m. At this time, the incident light L1 whose beam diameter is equal to the diameter D1 of the conical concave portion 16 enters the conical concave portion 16, and the outer diameter Do of the annular light L3' becomes 701 μm.

If the outer diameter Do is larger than the diameter D1 of the circular light receiving portion 12, the beam diameter of the incident light L1 to the conical recess 16 can be reduced by reducing the distance between the emitting end E and the semiconductor light receiving element 10. Thus, all of the incident light L1 can be made incident on the circular light receiving section 12 while avoiding the invalid area I. FIG. It is sufficient that the outer diameter Do of the annular light L3' is equal to or smaller than the diameter D1 of the circular light receiving portion 12. FIG. Even if the distance between the emitting end E and the semiconductor light receiving element 10 is changed, the inner diameter Di of the annular light L3' does not change.

On the other hand, as shown in FIG. 12, the 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 passes through the conical recess 16. Alternatively, the light may be incident on the circular light receiving portion 12 without the light. In this case, 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 .

At least a portion of the incident light L1 incident on the ineffective area I should be able to uniformly enter the circular light receiving section 12 while avoiding the ineffective area I by changing the direction of travel by the conical recess 16 . In particular, the closer to the ineffective area I, the greater the ratio of the isolation grooves 13 in the circumferential direction of the circular light-receiving section 12, and the more high-intensity light that is not photoelectrically converted. Useful for enlarging.

The operation and effects of the optical power supply converter 1 will be described.
The incident light L1 input to the optical power supply converter 1 via the optical fiber cable OC is converted into annular light L3, L3' by the conical concave portion 16 formed in the semiconductor light receiving element 10, and the circular light receiving portion 12 An equal amount of light is incident on the plurality of equally divided photodiodes 14 . Therefore, variations in the outputs of the photodiodes 14 can be reduced. In addition, since the annular lights L3 and L3′ do not enter the vicinity of the center C of the circular light receiving portion 12 where the plurality of isolation grooves 13 that do not generate photocurrent are concentrated, photoelectric conversion of the incident light L1 is performed. It is possible to reduce the amount of light that would otherwise be wasted. Therefore, the photocurrent of the semiconductor light receiving element 10 having the circular light receiving portion 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. .

Further, when the incident light L1, which travels while spreading out in a conical shape, is converted into parallel light L2 by the collimator lens 6, the incident angle α to the conical concave portion 16 can be made constant. Therefore, in order that the incident light L1 to be input does not protrude from the circular light receiving portion 12, the output end E of the optical fiber cable OC and the collimator lens have a beam diameter Db of the parallel light L2 that matches the diameter D1 of the circular light receiving portion 12. 6 can be easily set. Therefore, all of the incident light L1 that is input can be made incident on the circular light receiving portion 12, so that 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.

In addition, the conical recess 16 has an outer diameter Do smaller than the diameter D1 of the circular light receiving section 12 and an inner diameter Di larger than the outer diameter D2 of the ineffective area I of the circular light receiving section 12. light L3, L3'. All of the circular light beams L3 and L3' enter the circular light receiving portion 12 while avoiding the ineffective region I formed near the center C of the circular light receiving portion 12 where no photocurrent can be generated. Therefore, the incident light L1 input via the optical fiber cable OC can be used without waste, and the power supplied by the optical power supply converter 1 can be increased.

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 power supply converters 2a, 2b: output terminal portion 3: base 4: conductive member 5: cover 5a: insertion hole 6: collimator lens 6a: axis of symmetry 8: conductive paste 10: semiconductor light receiving element 12: circular light receiving Part 13: Isolation groove 14: Photodiode 15: Isolation groove 16: Conical recess 16a: Symmetry axis 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)

In an optical power supply converter that converts light input via an optical fiber cable into a photocurrent by a semiconductor light receiving element and outputs it,
The semiconductor light receiving element receives the circular light from the second surface side of the semiconductor substrate facing the first surface of the semiconductor substrate with respect to the circular light receiving portion formed for generating the photocurrent on the first surface side of the semiconductor substrate. It is a back-illuminated light receiving element that allows light to enter the part,
The circular light-receiving portion is divided into a plurality of linear isolation grooves extending from the center of the circular light-receiving portion so that the light-receiving areas are equal to each other, and a plurality of photodiodes connected in series by a plurality of conductive members. with
On the side of the second surface of the semiconductor substrate, a conical recess is formed by recessing the semiconductor substrate into a conical shape whose diameter decreases toward the first surface. formed through the center,
It is characterized in that the light incident from the second surface side is converted into an annular shape by the conical concave portion, and an equal amount of light is incident on each of the plurality of photodiodes of the circular light receiving portion. Optical power converter. 2. An optical power supply converter according to claim 1, further comprising a collimator lens for converting light input through said optical fiber cable into parallel light and for causing said parallel light to enter said conical concave portion. The conical recess has an outer diameter equal to or smaller than the diameter of the circular light receiving part, and the plurality of linear isolation grooves are formed so as to extend in the circumferential direction of the circular light receiving part. 3. The optical power feeding converter according to claim 1, wherein the converter is formed to have an annular shape with an inner diameter larger than the outer diameter of the ineffective region.

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