JP3720650B2 - Optical coupling device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical coupling device that is used, for example, as a light source for optical communication and optically couples a semiconductor element and an optical fiber via a lens.
[0002]
[Prior art]
Conventionally, an optical coupling device has a structure described in JP-A-5-37024.
[0003]
The optical coupling device described in JP-A-5-37024 performs optical coupling between a semiconductor light emitting element and an optical fiber via a spherical lens. That is, a trapezoidal groove with an alignment pattern for fixing the semiconductor light emitting element and a V groove for fixing the ball lens are formed on the optical coupling substrate composed of two semiconductor wafers. The trapezoidal grooves and the V-grooves are sized and shaped so that the laser emitting portion of the semiconductor light emitting element, the central portion of the spherical lens, and the central portion of the core of the optical fiber coincide with each other. It is set according to.
[0004]
[Problems to be solved by the invention]
However, the prior art has the following problems.
[0005]
That is, in the optical coupling device described in Japanese Patent Laid-Open No. 5-37024, the depths of the trapezoidal grooves and V-grooves of the optical coupling substrate are individually set, and the laser emitting portion of the semiconductor light emitting element and the central portion of the spherical lens In addition, since the core central part of the optical fiber is matched without adjustment, it is necessary to assemble and optically couple with extremely high accuracy. For this reason, it is difficult to reduce yield and assembly cost. Further, the position where the semiconductor light emitting element, the lens, and the optical fiber are in contact with the trapezoidal groove or the V groove differs depending on the height and diameter of each member.
[0006]
For this reason, when a temperature change occurs, the position of the central axis may slightly change depending on the coefficient of thermal expansion of each member. That is, positional deviation occurs in the height direction among the semiconductor light emitting element, the lens and the optical fiber, and the fiber light output fluctuates accordingly, and stable light transmission cannot be obtained. In particular, in the case of an optical coupling system using a lens, for example, when a positional shift occurs between the semiconductor light emitting element and the lens in the height direction, the laser focal position focused by the lens is increased due to the lens vertical magnification. Since the position changes, the condensing point is deviated from the center of the core of the optical fiber, and the fiber light output fluctuates greatly. As described above, in the optical coupling system using the lens, the condensing point is largely changed by the lens magnification even if the position is slightly changed. Therefore, a structure capable of maintaining a stable optical coupling state has been desired.
[0007]
An object of the present invention is to provide an optical coupling device capable of optically coupling a semiconductor element and an optical fiber by an easy operation and preventing light output fluctuation due to temperature change.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in a reference example of the present invention , a semiconductor element composed of at least one of a semiconductor light emitting element and a semiconductor light receiving element, a substrate member on which the semiconductor element is mounted, and the semiconductor element optically An optical fiber coupled to transmit laser light internally; and a lens mounted on the substrate member for optically coupling the semiconductor element and the optical fiber, wherein the semiconductor element is interposed between the substrate and the substrate. It is set as the structure attached to a member. The sheet film is a conductive film made of a metal film or an insulating film made of a resin material film. Further, the semiconductor element is connected to an external terminal of the optical coupling device through a metallized film applied to the surface of the substrate member.
[0009]
In this way, by applying a conductive sheet film or insulating sheet film to the part where the semiconductor element is mounted, when the temperature changes, the sheet film is mounted on the board member by expansion / contraction due to thermal expansion. The height position of the semiconductor element is changed. That is, the height position of the semiconductor element is corrected so that the laser emission position of the semiconductor element coincides with the center position of the lens whose height position has changed in the same manner due to temperature change, and between the semiconductor element and the lens. Eliminate relative height changes. Thereby, the amount of positional deviation of the laser condensing point that has passed through the lens can be minimized, and a stable optical coupling state between the semiconductor element and the optical fiber can be maintained. Further, the sheet film can be easily formed by adding a process of metallization wiring formed on the surface of the substrate member, and does not require special equipment or difficult process work. Furthermore, by changing the thickness and material of the sheet film arbitrarily, the amount of change in the height of the semiconductor element can be set as appropriate, so it can be easily and easily adapted to various situations such as the type and material of the lens or the fixed position. It can be set easily.
[0010]
In order to achieve the above object, according to the present invention, in the reference example, a substantially rectangular groove for positioning, holding, and fixing the lens is provided at the lens installation position of the substrate member, and the lens is substantially arranged with respect to the rectangular groove. It is configured to be fixed directly in contact with the diagonal line.
[0011]
Thus, by fixing the lens to the rectangular groove substantially diagonally, unlike the conventional case of fixing to the V groove, the lens can be fixed near the surface of the substrate member. As a result, the lens center position does not change significantly due to thermal expansion of the lens and adhesive even when temperature changes occur, and the relative height change with the laser emitting part of the semiconductor element mounted on the substrate member surface And the amount of positional deviation of the laser condensing point that has passed through the lens can be minimized.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In each drawing, in order to avoid complications, illustration of some metallized wirings, wire bonding, and bonding portions is omitted as appropriate.
[0013]
A reference example of the present invention will be described with reference to FIGS.
[0014]
FIG. 3 is a horizontal sectional view of the overall structure of the optical coupling device according to this reference example .
[0015]
In FIG. 3, the optical coupling device includes a laser diode 1 as a semiconductor light emitting element and a photodiode 10 as a semiconductor light receiving element. The laser diode 1 and the photodiode 10 are mounted on a silicon substrate 3 which is a substrate member. An optical fiber 14 that is optically coupled to the laser diode 1 and the photodiode 10 and internally transmits the laser light, and the laser diode 1, the photodiode 10, and the optical fiber 14 that are mounted on the silicon substrate 3 are optically coupled. A lens 4 to be coupled is provided. Further, a metallized wiring (not shown) and lead terminals (not shown) for electrically connecting the laser diode 1 and the photodiode 10 to the outside of the apparatus, and a case 11 for housing the silicon substrate 3. There is. A ferrule 19 comprising a cap 12 and an airtight glass window 13 for shutting off the inside of the case 11 from the outside and hermetically sealing, a zirconia sleeve 16 and a metal sleeve 18 in which an optical fiber 14 and an optical fiber coating 17 are provided. And a holder 15 attached to the side wall of one end of the case 11 and holding and fixing the ferrule 19. In this apparatus, the optical coupling between the laser diode 1 and the photodiode 10 and the optical fiber 14 is performed by a single lens 4.
[0016]
The case 11 is made of, for example, a ceramic material having a box shape, and includes eight lead terminals (not shown), for example, four on each side. A cap 12 for blocking the inside of the case 11 from the outside is attached to the upper surface of the case 11, and an airtight glass window 13 for blocking the inside of the case 11 from the outside is attached to the side wall of one end of the case 11. The dimensions of the box-shaped case 11 are, for example, a height (vertical direction on the paper surface in FIG. 3) of 4.6 mm, a horizontal width (perpendicular to the paper surface in FIG. 3), and a length (paper surface in FIG. 3). In the horizontal direction) is 10.0 mm.
[0017]
The holder 15 is a metal member and serves as a relay member that connects the ferrule 19 to the case 11.
[0018]
The ferrule 19 includes a zirconia sleeve 16 in which the optical fiber 14 is provided and fixed, and a metal sleeve 18 in which the optical fiber coating 17 is fixed. The attachment of the ferrule 19 causes the laser light passed from the lens 4 to enter the optical fiber 14 and the holder 15 and the ferrule 19 are moved in three axial directions so that the output light from the optical fiber 14 at that time becomes maximum. After the position adjustment, the metal sleeve 18 and the holder 15 are fixed by laser welding (not shown), and the holder 15 is similarly fixed to the side wall of the case 11 by laser welding (not shown).
[0019]
FIG. 1 is a horizontal sectional view showing a mounting structure of a laser diode 1 and a lens 4 which is one of the features of the optical coupling device of this reference example . FIG. 2 is a horizontal sectional view showing the positional deviation of the lens 4 due to a temperature change.
[0020]
In FIG. 1, a laser diode 1 is provided with a metallized wiring (not shown) formed on a surface 6 of a silicon substrate 3 and a conductive sheet film 2 made of a metal film, or an insulating sheet film 2 made of a resin-based material film. It is mounted on the part that was made. The mounting position of the laser diode 1 is positioned and mounted at a predetermined position with a marker (not shown) marked on the portion provided with the metallized wiring (not shown) and the sheet film 2 as a mark. The laser diode 1 is electrically connected to a metallized wiring (not shown) on the surface 6 of the silicon substrate 3 through wire bonding (not shown). The conductive or insulating sheet film 2 is formed in a series of operations of vapor deposition and sputtering processes for forming metallized wiring (not shown). The sheet film 2, for example, the reference example substantially 50μm thick in the case of the sheet film 2 in accordance with the resin-based material or a metal film substantially to the case of the sheet film 2 by (film such as aluminum or copper) thickness, 100 μm.
[0021]
The lens used in this reference example has a thermal expansion coefficient α of 5 to 10 × 10 ⁻⁶ / ° C. and a refractive index of 1.5 to 1.9. Further, as the adhesive, an ultraviolet curable or thermosetting epoxy resin-based one having a thermal expansion coefficient of 30 to 100 × 10 ⁻⁶ / ° C. is used. Further, as the sheet film, when the metal film is a resin material film made of copper having a thermal expansion coefficient α of 17 × 10 ⁻⁶ / ° C. or aluminum having a thermal expansion coefficient α of 23 × 10 ⁻⁶ / ° C. A material having a thermal expansion coefficient α of 20 to 200 × 10 ⁻⁶ / ° C. was used using a material such as polyimide, polyetherimide, or polyamideimide.
[0022]
In the silicon substrate 3, a groove or a step that becomes the lens mounting surface 7 is formed by anisotropic etching, and the lens 4 is fixed to the mounting surface 7 with an adhesive 5. The silicon substrate 3 has, for example, a thickness of the mounting portion of the laser diode 1 (vertical direction in FIG. 3) of 1.0 mm and a thickness of the lens mounting surface 7 portion of 0.3 mm. The lens 4 having an outer diameter of 1.4 mm is mounted so that the laser emitting portion of the laser diode 1 and the center of the lens 4 coincide.
[0023]
The lens 4 is made of a glass material and processed by molding or the like. In the drawing, the spherical lens 4 is illustrated. However, the present invention is not limited to this, and even when a cylindrical rod lens or an aspherical lens is used, the lens mounting surface 7 has the same configuration. 4 can be configured.
[0024]
When the lens outer diameter is reduced to about 0.7 mm, which is half of the above, the thickness of the sheet film 2 can be reduced to about half. That is, it is about 25 μm in the case of a resin material, and about 50 μm in the case of a metal material.
[0025]
The operational effects of this reference example configured as described above will be described below.
[0026]
The effect of applying the conductive or insulating sheet film 2 is that when the temperature change occurs by applying the conductive or insulating sheet film 2 to the portion where the laser diode 1 is mounted, this sheet film is used. The height position of the laser diode 1 mounted on the substrate member is changed by expansion / contraction due to thermal expansion of 2. That is, as shown in FIG. 2, when the temperature changes, the center position 20 of the lens 4 may change due to thermal expansion of the lens 4 and the adhesive 5.
[0027]
In the reference example of the present invention , the height position of the laser diode 1 is adjusted by utilizing the expansion / contraction of the sheet film 2 so that the laser emission position of the laser diode 1 matches the height change of the lens 4. By correcting, the relative height change between the laser diode 1 and the lens 4 is eliminated. That is, height correction is facilitated by selecting and using a sheet film having a material and thickness that make the thermal expansion amount of the lens 4 and the adhesive 5 and the thermal expansion amount of the sheet film 2 substantially the same. is there. Thereby, the positional deviation amount of the laser condensing point which passed the lens 4 and the optical fiber 14 can be suppressed in an allowable range, and the stable optical coupling state of the laser diode 1 and the optical fiber 14 can be maintained.
[0028]
The allowable range of the positional deviation amount between the laser condensing point and the optical fiber 14 is, for example, within a positional deviation range of about ± 1 μm in order to ensure the fluctuation of the fiber output light within 10%, as described above. In addition, this can be realized by eliminating the relative height change between the laser diode 1 and the lens 4. Further, the sheet film 2 can be easily formed by adding a process of metallized wiring (not shown) formed on the surface 6 of the silicon substrate 3, and requires special equipment and difficult process work. Absent. Furthermore, the amount of change in the height of the laser diode 1 can be appropriately set by arbitrarily changing the thickness and material of the sheet film 2, so that it can be set according to various situations such as the type and material of the lens 4 or the fixed position. Can be set easily and easily.
[0029]
As a result, even if the temperature changes, the relative height change between the laser diode 1 and the lens 4 can be eliminated, and the stable optical coupling state between the laser diode 1 and the optical fiber 14 can be maintained. . Therefore, even when optical coupling is performed using members having different heights and diameters as in the conventional structure, it is sufficient to form the sheet film 2 on the silicon substrate 3 with a predetermined thickness. The optical fiber 14 can be optically coupled to prevent fluctuations in light output due to temperature changes.
[0030]
The actual施例of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a horizontal sectional view showing a lens mounting structure which is one of the features of the optical coupling device of this embodiment. In FIG. 5, the figure showing the comparison of the lens height change by various lens mounting structures is shown.
[0031]
Although not shown in FIG. 4, the laser diode 1 is mounted at a predetermined position on the silicon substrate 3 so that the center position of the laser emitting portion and the lens 4 coincide. In the silicon substrate 3, a rectangular groove 8 having a single step 9 on which the lens 4 is held and fixed is formed by anisotropic etching. For example, the silicon substrate 3 has a thickness (up and down direction in the drawing) of 1.0 mm. For example, when the lens outer diameter is 1.5 mm, the rectangular groove 8 has a depth (vertical direction of the paper surface in the drawing) of 0.8 mm and a width (lateral direction of the paper surface of the drawing) of 1.51 mm. The groove width is formed slightly larger than the outer diameter of the lens 4. The step portion 9 in the rectangular groove 8 has a depth of 0.27 mm and a width of 0.05 mm, for example, and the lens 4 is held in contact with the step portion 9 of the rectangular groove 8 and bonded to the step portion 9. Agent 5 is filled and fixed.
[0032]
Accordingly, the lens 4 is fixed in contact with the rectangular groove 8 and the stepped portion 9 in a manner close to the diagonal of the lens 4. The rectangular groove 8 and the stepped portion 9 are formed by anisotropic etching. First, the rectangular groove 8 and the stepped portion 9 are formed by etching to the depth of the stepped portion 9 and then masking and further etching to the depth of the rectangular groove 8. . Thereby, the position of the laser emitting portion of the laser diode 1 mounted on the surface 6 of the silicon substrate 3 and the center position of the lens 4 installed in the rectangular groove 8 are substantially matched.
[0033]
FIG. 5 is a diagram comparing the amount of change in lens height for each of various lens mounting structures, and is a result confirmed by the authors through actual measurement. When the lens 4 is mounted on the flat portion with the adhesive 5 (similar to FIG. 1), or when the lens is adhesively fixed to the V groove (similar to the prior art), the lens 4 is mounted on the rectangular groove 8. It is the result of measuring the positional deviation of the center of the lens 4 when heated from room temperature to 85 degrees for each of the three mounting structures when fixed with the adhesive 5 (structure shown in FIG. 4). The heating up to 85 degrees is a condition determined from the specification of the use environment temperature of the optical coupling device. According to FIG. 5, the positional deviation amount at the center of the lens 4 when the lens 4 is fixed to the flat portion is expressed as a relative value with 1.0, and 0.7 when the lens 4 is fixed to the V groove. In this case, it is confirmed that the positional deviation of the center of the lens 4 can be reduced by fixing the lens 4 to the rectangular groove 8.
[0034]
The operational effects of the present embodiment configured as described above will be described below.
[0035]
By fixing the lens 4 to the rectangular groove 8 and the stepped portion 9 on a substantially diagonal line, the center of the lens 4 can be fixed near the surface 6 of the silicon substrate 3, unlike the case of fixing to the V groove as in the prior art. . Thereby, even if the temperature changes, the center position of the lens 4 does not change significantly due to the thermal expansion of the lens 4 and the adhesive 5, and the laser emitting portion of the laser diode 1 mounted on the surface 6 of the silicon substrate 3 is not affected. The relative height change can be reduced, and the amount of positional deviation of the laser focusing point that has passed through the lens 4 can be minimized. Further, by forming the rectangular groove 8 and the step portion 9 by anisotropic etching, the groove width and the step can be formed with high accuracy, and by installing the lens 4 in the rectangular groove 8 and the step portion 9, the laser can be formed. The laser emission position of the diode 1 and the center position of the lens 4 can be matched without adjustment, and there can be no height shift due to a temperature change after the lens 4 is fixed.
[0036]
Further, the angle of the lens 4 in contact with the rectangular groove 8 and the stepped portion 9 with respect to the center of the lens 4 is made larger than the angle mounted on the V groove formed by the conventional anisotropic etching. Thus, the positional deviation of the center of the lens 4 that changes due to the thermal expansion of the lens 4 and the adhesive 5 can be minimized. In other words, by setting the angle formed with respect to the center of the lens 4 within a range of 140 degrees to 180 degrees, a relative positional shift between the laser condensing point position passing through the lens 4 and the core center position of the optical fiber 14 is allowed. Can be within the range. As a result, it is possible to maintain a stable optical coupling state between the laser diode 1 and the optical fiber 14 and to prevent light output fluctuations due to temperature changes.
[0037]
In the reference example of the present invention, the optical coupling device including both the laser diode 1 and the photodiode 10 as semiconductor elements has been described as an example. However, the present invention is not limited to this, and only one of them is provided. It can also be applied to an optical coupling device, and the same effect is obtained.
[0038]
In the embodiment of the present invention, the procedure for forming the rectangular groove 8 and the stepped portion 9 by anisotropic etching is shown. However, the present invention is not limited to this, and the procedure may be changed or formed by another method. There is no obstacle, and the same effect is obtained in these cases.
Furthermore, in the embodiment of the present invention , the shape of the stepped portion 9 is described, but the shape is not limited to this, and as described in the embodiment of the present invention , the angle in contact with the lens 4 is 140 to 180 degrees. What is necessary is just to set to the shape dimension of the level | step-difference part 9 which becomes in the range of a degree, and the same effect is acquired also in these cases.
[0039]
【The invention's effect】
According to the present invention, it is possible to optically couple the semiconductor element and the optical fiber with an easy operation, and to prevent the light output fluctuation due to the temperature change.
[Brief description of the drawings]
FIG. 1 is a horizontal sectional view showing a semiconductor element and a lens mounting structure which are the main parts of an optical coupling device of a reference example of the present invention.
FIG. 2 is a horizontal sectional view showing a change in the lens height due to a temperature change.
3 is a horizontal sectional view of the overall structure of the optical coupling device shown in FIG. 1;
It is a horizontal cross-sectional view showing a lens mounting structure is a main part of an optical coupling device according to the real施例of the present invention; FIG.
FIG. 5 is a diagram showing a comparison of changes in lens height by lens mounting structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Laser diode, 2 ... Sheet film, 3 ... Silicon substrate, 4 ... Lens, 5 ... Adhesive, 6 ... Substrate surface, 7 ... Lens mounting surface, 8 ... Rectangular groove, 9 ... Step part, 10 ... Photodiode, DESCRIPTION OF SYMBOLS 11 ... Case, 12 ... Cap, 13 ... Airtight glass window, 14 ... Optical fiber, 15 ... Holder, 16 ... Zirconia sleeve, 17 ... Optical fiber coating, 18 ... Metal sleeve, 19 ... Ferrule, 20 ... Lens center

Claims (6)

A semiconductor element comprising at least one of the semiconductor light emitting device and a semiconductor light receiving device, and the substrate member for mounting the semiconductor element, an optical fiber for internal transmitting the semiconductor element optically coupled to the laser beam, the substrate member In an optical coupling device that is mounted and has a lens that optically couples the semiconductor element and the optical fiber,
The substrate member has a substantially rectangular groove for positioning and holding and fixing the lens,
The optical coupling device , wherein the lens is supported from both sides by the rectangular groove, and the support portion is positioned on a substantially diagonal line with respect to the lens . A semiconductor element comprising at least one of a semiconductor light emitting element and a semiconductor light receiving element; a substrate member on which the semiconductor element is mounted; an optical fiber that is optically coupled to the semiconductor element and transmits laser light; and In an optical coupling device that is mounted and has a lens that optically couples the semiconductor element and the optical fiber,
The substrate member has a substantially rectangular groove for positioning and holding and fixing the lens,
The optical coupling device , wherein the lens is supported on the side wall of the rectangular groove from both sides, and is disposed so as to be positioned between the lower end of the lens and the bottom surface of the groove .   3. The optical coupling device according to claim 2, wherein the semiconductor element is mounted on the substrate member via a sheet film.   3. The optical coupling device according to claim 2, wherein the rectangular groove is formed by anisotropic etching and includes at least one step in the depth direction of the groove.   3. The optical coupling device according to claim 2, wherein the lens has a position in contact with the rectangular groove and an angle formed with respect to a center of the lens is within a range of 140 degrees to 180 degrees. A semiconductor element comprising at least one of a semiconductor light emitting element and a semiconductor light receiving element; a substrate member on which the semiconductor element is mounted; an optical fiber that is optically coupled to the semiconductor element and transmits laser light; and In an optical coupling device that is mounted and has a lens that optically couples the semiconductor element and the optical fiber,
The semiconductor element is attached to the substrate member via a sheet film, and is provided with a substantially rectangular groove for positioning, holding and fixing the lens on the substrate member, and the lens is fixed to the rectangular groove, The optical coupling device is characterized in that the fixing portion is positioned substantially diagonally with respect to the lens, and the lens and the bottom surface of the groove are arranged with a gap therebetween .

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