JP2690354B2 - Optical coupling method between optical semiconductor chip and optical fiber - Google Patents

Description

The present invention relates to an optical coupling method for an optical semiconductor chip and an optical fiber, and an object thereof is to provide an optical coupling method which has good workability and is suitable for maintaining high optical coupling efficiency stably for a long period of time. After closely fixing the optical fiber to the object to be fixed, guide a powerful laser beam to this optical fiber and melt the irradiation part of the laser light emitted from the optical fiber to the object to be fixed to form a through hole. Then, the optical semiconductor chip is attached to the through hole forming portion of the fixed object.

TECHNICAL FIELD The present invention relates to an optical coupling method for an optical semiconductor chip and an optical fiber.

In a general optical communication system, a semiconductor laser (LD) and a light emitting diode (LE
D), etc. Light emitting system Modulates the intensity of the light emitted from the semiconductor, etc., and transmits the modulated light to the receiving side through an optical transmission line consisting of an optical fiber, and the receiving side receives light from the receiving system such as a photodiode (PD) Transmission information is reproduced by converting light to electricity by a semiconductor. In order to perform efficient transmission and reception of optical signals, it is necessary that these light emitting system and light receiving system optical semiconductors and the optical fiber are optically coupled with high optical coupling efficiency. There is a demand for an optical coupling method for an optical semiconductor chip and an optical fiber, which is capable of maintaining stable for a long time.

2. Description of the Related Art A conventional optical coupling method between an optical semiconductor chip and an optical fiber will be described with reference to FIG. First, the optical semiconductor chip 53 such as a PD chip is fixed to the carrier 52 fixed on the substrate 51, and the light emitted from the taper tip spherical portion 54a of the taper tip spherical optical fiber 54 is an optical semiconductor with high optical coupling efficiency. After the position of the tapered spherical optical fiber 54 is adjusted so as to be incident on the chip 53, the tapered spherical optical fiber 54 is fixed on the substrate 51 by the melted and solidified solder 55. Optical semiconductor chip
When 53 is a light receiving system, the position of the tapered spherical optical fiber 54 is adjusted while monitoring the optical-electrical conversion efficiency of the light emitted from the tapered spherical optical fiber 54 as described above. When the semiconductor chip 53 is of a light emitting system, the position of the tapered spherical optical fiber 54 is adjusted while monitoring the electric-optical conversion efficiency between the chip driving power and the light incident on the tapered spherical optical fiber 54. . In the prior art, the position of the tapered spherical optical fiber 54 is adjusted after fixing the optical semiconductor chip 53.
This is because it is easier than adjusting the position of the optical semiconductor chip 53 after fixing the tapered spherical optical fiber 54 to the substrate 51.

Problems to be Solved by the Invention The conventional method described above is not good in workability because it is necessary to adjust the position of the optical fiber while monitoring the optical coupling efficiency between the optical fiber and the optical semiconductor chip. Further, since the solder is interposed between the optical fiber and the substrate in a thickness corresponding to the position adjustment range of the optical fiber, even if the external force is constantly applied to the optical fiber, even if the force is small. The creep occurs in the solder, the relative positional relationship between the optical fiber and the optical semiconductor chip changes, and the optical coupling efficiency between the optical fiber and the optical semiconductor chip changes over time. Therefore,
The conventional method is not suitable for maintaining high optical coupling efficiency stably for a long period of time.

The present invention has been created in view of such circumstances,
An object of the present invention is to provide an optical coupling method of an optical semiconductor chip and an optical fiber, which has good workability and is suitable for maintaining high optical coupling efficiency stably for a long period of time.

Means for Solving the Problem FIG. 1 is an explanatory view of the principle of the present invention, and the method of the present invention will be described with reference to this drawing.

First, as shown in FIG. 1A, after the optical fiber 1 is closely fixed on the object 2 to be fixed, a powerful laser beam is guided to the optical fiber 1 to fix the laser beam emitted from the optical fiber 1. The through hole 3 is formed by melting the irradiated portion of the object 2.

Then, as shown in FIG. 3B, the optical semiconductor chip 4 is attached to the portion of the fixed object 2 where the through hole 3 is formed.

Effect According to the configuration of the present invention, a laser beam having sufficient power for melting an object to be fixed is guided to an optical fiber to be optically coupled with an optical semiconductor chip, and a through hole is formed on an optical path of this strong laser beam. Since the optical semiconductor chip can be fixed to the object by using the position of this through hole as a guide, it is not necessary to adjust the position of the optical fiber or optical semiconductor chip while monitoring the optical coupling efficiency. become. As a result, the workability in optically coupling the optical semiconductor chip and the optical fiber is improved.

In addition, since the optical fiber is fixed in close contact with the object to be fixed without adjusting the position, the relative position of the optical fiber and the optical semiconductor chip due to creep of inclusions between the optical fiber and the object to be fixed. It is possible to prevent the relationship from changing with time, and to maintain the initially high optical coupling efficiency stably for a long period of time.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The procedure in the embodiment of the method of the present invention will be described with reference to FIG. First, a U-shaped groove 11a is formed in a substrate 11 made of a material such as metal or ceramics, as shown in a side view and a front view in FIGS. Next, as shown in FIG. 3C, the end face is obliquely polished to complete the total reflection surface 12
As a, the optical fiber 12 is fixed to the U-shaped groove 11a of the substrate. This fixing can be performed by using a solder 13 that has been melted and solidified after metalizing the side surface of the optical fiber 12 and the U-shaped groove 11a. In this case, the reflection optical axis of the total reflection surface 12a of the optical fiber is perpendicular to the substrate 11,
Also, to prevent creep in the solder 13, the optical fiber 12
Is sufficiently adhered to the U-shaped groove 11a of the substrate. Then, as shown in FIG. 3D, a YAG having sufficient power to melt the substrate 11 along the optical axis OA ₁ of the optical fiber 12.
Laser light such as a laser (wavelength is 1.06 μm or 1.15 μm) is introduced into the optical fiber 12. By doing so, the laser light is totally reflected by the total reflection surface 12a of the optical fiber and emitted from the side surface in a direction perpendicular to the central axis of the optical fiber, for example, so that the substrate 11 on the optical path is irradiated with the laser light. The heated portion is melted and evaporated to form the through hole 11b. In this case, if dust adheres to the side surface of the optical fiber 12, etc., the dust burns and sticks to the side surface of the fiber, the power of the emitted laser light decreases, or in the worst case, the optical fiber is heated and damaged. Therefore, when forming the through hole 11b in the substrate 11, it is desirable to work in a vacuum or in an inert gas such as N ₂ . Finally, as shown in FIG. 6E, in this example, a PD (photodiode) chip 14 as an optical semiconductor chip is formed in the portion where the through hole 11b is formed so that the center of the light receiving surface thereof coincides with the center of the through hole 11b. Install. Generally, the optical path of the laser light used to form the through hole 11b and the optical path of the light to be incident on the PD chip 14 match, so that the PD chip 14 should be positioned with the position of the through hole 11b as a guide as described above.
By installing the optical fiber, you can adjust the optical fiber without adjusting the position while monitoring the optical coupling efficiency.
Optical coupling between 12 and PD chip 14 can be made.

FIG. 3 is a perspective view of a PD chip that can be used in the embodiment of the present invention. The PD chip 14 includes a light receiving portion 21 having a photoelectric conversion function, a substantially annular electrode 22 provided along the outer periphery of the light receiving portion 21, and a ground electrode 23 provided on the opposite side of the electrode 22. It is configured to include. twenty four
Is a bonding wire for electrically connecting the electrode 22 and an electronic circuit (not shown). A feature of this embodiment is that an annular projection 22a is formed on the upper surface of the electrode 22 concentrically with the electrode 22. The annular protrusion 22a can be formed integrally with the electrode 22 by, for example, forming the electrode 22 thicker and partially removing the electrode 22 by etching. By providing the annular projection 22a, the following effects are produced.

FIG. 4 is a cross-sectional configuration diagram of the PD chip 14 mounting portion in the embodiment of the present invention. In this embodiment, the electrode 22 of the PD chip is
Since the annular projection 22a is formed on the substrate, the PD chip 14 can be easily fixed to the substrate 11. That is, by making the outer diameter of the annular protrusion 22a and the inner diameter of the PD chip mounting portion in the through hole 11b of the substrate substantially match, it is possible to easily insert the annular protrusion 22a into the through hole 11b. The position of the chip 14 with respect to the substrate 11 can be determined, and in this state, the PD chip 14 can be fixed to the substrate 11 by die bonding, for example.

As described above, according to the present embodiment, the guided light of the optical fiber 12 can be transmitted with high optical coupling efficiency without any position adjustment while monitoring the optical coupling efficiency between the optical fiber 12 and the PD chip 14. Since it can be made incident on the chip 14, workability is improved. Further, since it is not necessary to adjust the distance between the optical fiber 12 and the U-shaped groove 11a of the substrate, the optical fiber 12 is brought into close contact with the U-shaped groove 11a to prevent the fluctuation of the optical coupling efficiency due to creep or the like. Therefore, the initial optical coupling efficiency can be stably maintained for a long period of time.

The procedure in another embodiment of the method of the present invention will be described with reference to FIG. In this embodiment, an optical fiber and an LD (semiconductor laser) chip are optically coupled. First, as shown in the diagram (a), the tapered tip spherical portion 32a is formed on the substrate 31 in which the protrusion 31c is formed between the thick portion 31a and the thin portion 31b.
The optical fiber 32 in which is formed is fixed in the same manner as in the previous embodiment so that the tapered tip spherical portion 32a faces the protrusion 32c of the substrate. Next, as shown in FIG. 2B, a powerful laser beam is introduced along the optical axis OA ₂ of the optical fiber 32,
The through hole 31d is formed in the protrusion 31c of the substrate located on the outgoing optical path.
To form In this case, the laser light emitted from the optical fiber 32 is several μm to 10 μm due to the converging action of the tapered tip spherical portion 32 a.
Since it can be narrowed down to a beam system of several μm, the optical power density of the laser light irradiation portion can be increased, and the through hole 31d can be formed by the laser light having a relatively small power. Then, as shown in FIG. 3C, the LD chip assembly 33 is attached to the portion of the substrate where the through hole 31d is formed.

FIG. 6 is a perspective view of an LD chip assembly 33 that can be used in the embodiment shown in FIG. 5, and FIG. 7 is a sectional configuration diagram of an LD chip assembly 33 mounting portion. The LD chip assembly 33 is configured by including a heat sink 42 having a plate-like protrusion 41 at its end and an LD chip 43 fixed onto the heat sink 42 by die bonding, and the plate-like protrusion 41 of the heat sink. Is the active layer of the LD chip
A light passage hole 41a is formed at a position where the end faces of 43a face each other. Further, an annular protrusion 41b is formed around the light passage hole 41a with the emission optical axis of the LD chip 43 as the center.
The light passage hole 41a and the annular protrusion 41b can be formed by etching the plate-like protrusion 41 of the heat sink made of a metal material.

In this way, the LD chip assembly has an annular protrusion 41b.
By forming the above, it is possible to easily insert the annular protrusion 41b into the through hole 31d of the substrate 31 as in the previous embodiment.
The position of the LD chip 43 can be determined.

Effects of the Invention As described above, according to the present invention, it is possible to provide an optical coupling method for an optical semiconductor chip and an optical fiber, which has good workability and is suitable for maintaining high optical coupling efficiency stably for a long period of time. It has the effect of being possible.

As in the embodiment shown in FIG. 2, if the end face of the optical fiber is polished obliquely to fix the optical fiber in parallel with the substrate, the volume required for mounting the optical fiber is reduced. Another advantage is that the device can be downsized.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the present invention, FIG. 2 is a diagram showing a procedure in the embodiment of the present invention, and FIG. 3 can be used in the embodiment of the present invention.
FIG. 4 is a perspective view of a PD chip, FIG. 4 is a sectional configuration diagram of a PD chip attachment portion in an embodiment of the present invention, FIG. 5 is a diagram showing a procedure in another embodiment of the present invention, and FIG. FIG. 7 is a perspective view of an LD chip assembly that can be used in this embodiment, FIG. 7 is a sectional configuration diagram of an LD chip assembly mounting portion in another embodiment of the present invention, and FIG. 8 is an explanatory view of the prior art. 1,12,32 …… Optical fiber, 2 …… Fixed object, 3,11b, 31d …… Through hole, 4 …… Optical semiconductor chip, 11,31 …… Board, 14 …… PD (photodiode) chip , 33 …… LD (semiconductor laser) chip assembly, 43 …… LD chip.

Claims (1)

(57) [Claims] 1. An optical fiber (1) is adhered and fixed on an object (2) to be fixed, and then a powerful laser beam is guided to the optical fiber (1) to emit the laser beam emitted from the optical fiber (1). Fixed object (2)
The light is characterized in that a portion irradiated with the light is melted to form a through hole (3), and an optical semiconductor chip (4) is attached to the through hole (3) forming portion of the fixed object (2). Optical coupling method for semiconductor chip and optical fiber.