JPS61267386A - Semiconductor light emission device with optical fiber - Google Patents

Abstract

PURPOSE:To eliminate a thermal distortion and obtain a stable hotocoupling efficiency at all times by a method wherein the combination of the material of an optical fiber, the material of the stem of a package and the material of a fiber guide is so selected as to keep the amount of displacement produced by heat equal at all times. CONSTITUTION:A submount 2 made of a ceramic material SiC is fixed to the bottom part 1b of the stem 1 of a package and tubular jacket guide 6 and fiber guide 8 are provided on the side part 1a of the stem 1 so as to make the tip of an optical fiber 10 face the laser beam emitting surface of a laser diode 4. As the material of the stem 1 and the fiber guide 8, a material with a low thermal expansion coefficient (invar) is employed. A quartz fiber is employed as the optical fiber 10 and the surface of the quartz fiber is metallized with a metal such as Ni or Al, whose thermal expansion coefficient is similar to that of the material of the stem 1 and the fiber guide 8, by ion plating or plating to make the equivalent thermal expansion coefficient of the optical fiber large.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a semiconductor light emitting device with an optical fiber, and particularly to a semiconductor light emitting device with an optical fiber suitable for application to optical communications.

[Background of the invention]

2. Description of the Related Art Semiconductor light emitting devices with optical fibers used for optical communications and the like are configured such that the output surface of a semiconductor light emitting element such as a laser diode and an optical coupling end, which is the tip of an optical fiber, face each other. The optical coupling end of the optical fiber is previously processed into a lens in order to efficiently introduce light from the semiconductor light emitting element. When optically coupled with this structure, the optical coupling efficiency changes depending on the amount of relative positional deviation of the optical axis between the semiconductor light emitting element and the optical coupling end of the optical fiber. Now, for example, a laser diode is used as the semiconductor light emitting device, a single mode fiber with a core diameter of 5 to 10 μφ is used as the optical fiber, and the optical axis direction is changed by changing the relative position between the laser diode and the optical coupling end of the optical fiber. In two directions, when the vertical direction to the optical axis direction is the X direction and the horizontal direction is the X direction, the change in optical coupling efficiency for misaligned acids in the become. As can be seen in Figures 5 and 6, the optical coupling efficiency has a small tolerance for positional deviation in the X direction (the same applies to the %descend. This result is based on the use of a single mode fiber (core diameter 5 to 10 μm) as the optical fiber, and the above tolerance range is somewhat larger for a multimode fiber (core diameter 45 to 62 μm). On the other hand, the tolerance range for positional deviation in two directions is larger than the tolerance range in the X direction.

Therefore, the conventional device is, for example, disclosed in Japanese Patent Application Laid-open No. 60-43889.
As described in the above publication, a structure in which the optical coupling end of an optical fiber is fixed in a hole or groove provided in a plastic support, and the X direction and the deviation in the X direction can be adjusted by deforming the support. is taking.

Further, as described in Japanese Patent Application Laid-Open No. 57-138191, the thickness of the semiconductor laser fixing part and the fiber fixing part and the combination of constituent materials are taken into consideration, and the structure is such that there is no relative displacement in the X direction.

However, all of these conventional structures consider the relative positional shift between the optical fiber and the semiconductor light emitting element, which also emits light in the X direction (X direction), in response to temperature changes that the package undergoes. No consideration was given to two directions. For example, in the structure described in Japanese Unexamined Patent Publication No. 60-43889, the relative positional deviation between the semiconductor light emitting element and the optical fiber in the two axial directions is calculated as follows. The coefficient of thermal expansion α□ of Kovar, which is the material of the package stem, is 5. OX 1. O-' (℃-
”), the coefficient of thermal expansion α2 of copper and nickel, which is the material of the fiber guide 2, is 14 × 10−’ (’C-1), and the coefficient of linear expansion α3 of the optical fiber is 0.5 × 10−’ (’
C-1), the distance A between the fiber support part and the tip of the fiber guide is IIIll, the protrusion length B of the fiber guide from the side surface of the stem is 211IIl, and the temperature is /I
If T ('C) changes, the amount of thermal deformation of the stem ■4. is ■, □=, (A0B)Xα1X71T =3X5. OXl 0-'X/IT = 15X10-'IT. On the other hand, the amount of thermal deformation L2 on the fiber side is T,2=
AXαa x A T + B Xα, xA”r'=(
I Xo, 5X10-'+2. X]4X Xl0-
') AT=28.5X 10-'A']'. (2) There is a large difference between the values of T, 1 and T, 2, and as the temperature changes, the difference becomes larger and larger. For example, when the temperature rises, the elongation on the fiber side becomes larger than the stem, which causes thermal strain to be applied to the fiber or the soldered joint between the fiber and the tip of the protruding part of the fiber support.
Since deformation may occur, this may cause a relative positional shift between the semiconductor light emitting element and the optical fiber, or may cause deterioration due to long-term use.

[Purpose of the invention]

An object of the present invention is to obtain a semiconductor light emitting device with an optical fiber that can always obtain stable optical coupling efficiency even if a temperature change occurs in the package.

[Summary of the invention]

A semiconductor light emitting device with an optical fiber is configured such that the output surface of the semiconductor light emitting element and the optical coupling end of the optical fiber face each other. The semiconductor light emitting device described above is bonded onto the stem of the package via a submount. The above-mentioned optical fiber passes through a fiber guide fixed to the side surface of the stem, its middle part is fixed at the fiber guide tip, and its distal end is fixed by a fiber support near the semiconductor light emitting element, and its optical coupling end is fixed. It faces the emission surface of the semiconductor light emitting device mentioned above.

A feature of the present invention is that in the semiconductor light emitting device with an optical fiber as described above, by always making the generated thermal displacement waves equal in combination with the material of the optical fiber, the material of the stem of the package, and the material of the fiber guide, It has a structure that eliminates the occurrence of thermal strain.

[Embodiments of the invention]

EMBODIMENT OF THE INVENTION Hereinafter, as an example of the present invention, a case where the semiconductor light emitting device is a laser diode will be described with reference to FIGS. 1 to 3.

The stem 1 of the package is made of, for example, a Kovar material, and a submount 2 made of a ceramic SiC material is fixed to the bottom part 1b of the stem 1 with a low melting point bonding material 3 such as solder.

The laser diode 4 is fixed to the submount 2-H with a low melting point bonding material 5 such as solder. A tubular jacket guide 6 is fixed to a side surface of the stem 1 facing one emission surface of the laser diode 4 with a bonding material 7 such as silver solder. A fiber guide 8 is bonded to this jacket guide 6 with a bonding material 9 such as silver solder. This fiber guide 8 is a tube having a protrusion 8a inside the package. The optical fiber 10 includes a core LOa made of a transparent material such as quartz and having a uniformly high refractive index, and a cladding 10b (not shown) covering the core 10a and having a uniform refractive index smaller than the core 10a. It consists of a jacket with 10 b 11 cladding. This optical fiber 10 passes through the aforementioned fiber guide 8 and is disposed such that its tip faces the emission surface number from which the laser diode 4 emits the laser beam. The optical fiber 10 is bonded and fixed at the end of the protrusion 8a of the fiber guide 8 with a bonding material 11 such as solder or adhesive. The bonding and fixing portion formed by the bonding material 11 is also a portion that maintains airtightness inside and outside the package. Furthermore, the optical fiber 10 and the jacket guide 6 are connected to a fixing material 16 such as resin.
In the inside and protruding portion of the fiber guide 8 of this optical fiber 10 which is bonded and fixed, the jagut is peeled off and the Clarad 10b is exposed, and the optical coupling end 10c, which has been processed with a lens at its tip, connects to one side of the laser diode 4. The optical fiber 10 faces the output surface of the optical fiber 10, and is adapted to take the laser light into the optical fiber 10. Further, the optical coupling end side of the optical fiber 10 is inserted into a hole 13 with a circular cross section bored in the fiber support 12 provided near the laser diode 4,
This hole 13 is fixed by a fixing material 14 such as a resin filled therein. This fiber support 12 is fitted into a hole in the bottom surface 1b of the stem 1, and a bonding material 15 such as silver solder is used.
Fixed by A light receiving element 17 such as a photodiode faces the other emission surface of the laser diode 4. This light receiving element 17 is attached to a support body 18 joined to the bottom surface portion 1b of the stem 1. Light receiving element 1
The signal extraction lead wires 19 and 20 of No. 7 extend outside through the side surface 1a of the stem 1, and the side surface 1a of the stem 1 and the lead wires 19.20 are sealed with glass. .

Furthermore, the stem 1 is provided with two lead wires 21 and 22. One lead wire 21 is.

Ground lead, welded to stem 1, stem 1
It is electrically connected to the lower electrode of the laser diode 4 via the submount 2 . In addition, the other lead wire 22
Although not shown in the stem 1, the stem 1 is sealed with glass and its inner end is electrically connected to the −L portion electrode of the laser diode 4.

The aforementioned light receiving element 17 measures the light intensity of the laser light emitted from the laser diode 4, adjusts the operating current of the laser diode 4 based on the measurement signal, and adjusts the operating current of the laser diode 4 to transmit the laser light within the optical fiber 10. Control the light intensity to a predetermined value.

In the structure as described above, the optical coupling efficiency between the output surface of the laser diode 4 and the optical coupling end of the optical fiber 10 is:
This is achieved by matching as much as possible the thermal deformation that occurs in the combination of the optical fiber, stem material, and fiber guide material.

As a first means in the present invention, the optical fiber 1
As fiber, stem material and fiber guide material,
By using materials whose thermal expansion coefficients are almost the same, the thermal deformation described above is made to match as much as possible. Specifically, the stem 1 and fiber guide 8 of the package
The material has a low coefficient of thermal expansion (a = 2 X i 0
-6 ('C-1) Fe-36Ni alloy material (Invar) is used. Further, a quartz fiber is used as the optical fiber 10, and the surface of the quartz fiber is coated with ion plate ink of metals such as N i and A Q having the same coefficient of thermal expansion as the materials of the stem 1 and fiber guide 8 described above. Alternatively, the quartz fiber is metallized by plating to increase the apparent coefficient of thermal expansion of the quartz fiber.

The materials for the above-mentioned stem] and fiber guide 8 and the surface treatment material for the quartz fiber are not limited to the above-mentioned materials. A material having a thermal expansion coefficient may be used.

- By using a combination of three types of materials, the thermal deformations occurring in the stem 1, fiber guide 8, and optical fiber 1° are matched as much as possible.

The length from the fiber support 12 to the bonding material 11 at the tip of the protrusion 8a of the fiber guide 8 is A, and the length from the bonding material 11 at the tip of the protrusion 8a of the fiber guide 8 to the end surface of the stem side surface 1a of the fiber guide 8. When the length is B, the combination of the materials of the optical fiber 0, the material of the stem 1, and the material of the fiber guide 8 is determined by the ratio A/H of the lengths A and B described above.

As a second means in the present invention, the combination of the above-mentioned optical fiber, stem material, and fiber guide material and the length A
The above-mentioned material and lengths A and B are determined based on the mutual relationship between the ratio A/B and B, and the above-mentioned thermal deformation is matched as much as possible.

As a specific first example of this second means, Fe-42N i is used as the material of the fiber guide 8.
6 (', r When used in combination with alloy materials or alumina ceramics, no relative displacement occurs due to temperature changes, and at this time, the ratio A of the lengths A and B described above is
/B is 1.1.

In addition, in the second embodiment, the material of the fiber guide 8 is Fe-50Ni alloy material (1:F
) is a combination. At this time, the ratio A/B of the aforementioned lengths A and B is 1.3.

Further, in the third embodiment, the fiber guide 8 is made of silk using a Cu34Nj alloy material. At this time, the ratio A/B of the aforementioned lengths A and B is 2.4. As shown in each of the above embodiments, when the materials of the stem and the fiber guide 8 are selected, the above-mentioned lengths A and B in a structure in which relative positional deviation does not occur due to temperature changes.
The ratio A/B is uniquely determined.

However, if the materials of the stem 1 and the fiber guide 8 are changed, the ratio A/B of the lengths A and B described above in a structure that does not cause relative positional deviation due to temperature changes changes.

That is, the desired relative positional deviation is achieved by the combination of the ratio α1/α of the thermal expansion coefficient α of the stem 1 and the thermal expansion coefficient α1 of the fiber guide 8, and the ratio A/H of the lengths A and B described above. Structures that do not occur are determined.

FIG. 4 shows the relationship between α1/α and A/B, with α and /α plotted on the horizontal axis and A/B plotted on the vertical axis.

Therefore, in each of the above embodiments, the material combination of the fiber guide 8 is selected for the stem 1 made of Kovar material based on the relationship shown in FIG.

In addition, in the embodiment shown above, the case where Kovar was used as the material of the stem 1 was explained, but the material of the stem 1 is not limited to Kovar, and for example, ceramic SiC or Pyrex glass can also be used.

In this case, suitable materials for the fiber guide 8 include Kovar material and Fe-42Ni alloy material. At this time, the ratio A/B of the aforementioned lengths A and B is 1.1.

By adopting the structure as explained above, even if a light emitting device equipped with a semiconductor light emitting element such as a laser diode, an optical fiber, etc. is subjected to repeated temperature changes of low and high temperatures, the optical fiber side and the stem supporting the optical fiber can be easily maintained. The thermal expansion coefficients of the two sides are almost the same.

i Therefore, the less rigid optical fiber side is not restrained by thermal deformation of the highly rigid stem, and it is possible to obtain a light emitting device that is always free from relative positional deviation and stress.

That is, a semiconductor light emitting device with an optical fiber is initially assembled in such a state that the light emitted from one light emitting element is taken into the optical fiber with maximum optical coupling efficiency. This state is always maintained even when the temperature changes after assembly, and the optical coupling efficiency between the light emitting element and the optical fiber does not decrease.

〔Effect of the invention〕

As described above, according to the present invention, even if a temperature change occurs in the package, it is possible to always obtain stable optical coupling efficiency between the light emitting element and the optical fiber.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the light emitting device of the present invention, FIG. 2 is a sectional view taken along line nn' in FIG. 1, and FIG. Figure 4 shows the relationship between the thermal expansion coefficient ratio of the main part and the length ratio of the main part in the light emitting device of the present invention, and Figures 5 and 6 show the light emitting element and optical fiber in the conventional light emitting device. It is a figure explaining the positional shift amount with respect to FIG. ■... Stem, 2... Submount, 3, 5, 7,
9゜11.15... Bonding material, 4... Laser diode, 6... Jacket guide, 8... Fiber guide, 10... Optical fiber, ]2... Fiber support, 17. ··Light receiving element.

Claims (1)

[Scope of Claims] 1. A semiconductor light emitting device and an optical fiber having an optical coupling end facing the output surface of the light emitting device, the light emitting device being provided on the bottom of the stem via a submount, In the semiconductor light emitting device with an optical fiber, the optical fiber passes through a fiber guide provided on a side surface of the stem, and an optical coupling end side of the optical fiber is supported by a fiber support provided in the vicinity of the light emitting element. 1. A semiconductor light-emitting device with an optical fiber, wherein the optical fiber, the fiber guide, and the stem are made of a material having a coefficient of thermal expansion such that the amount of thermal displacement of each is always equal. 2. A quartz fiber is used as the optical fiber, an Fe-36Ni alloy material is used as the stem and fiber guide material, and the surface of the fiber is made of a material having a coefficient of thermal expansion comparable to that of the stem and fiber guide material. A semiconductor light emitting device with an optical fiber according to claim 1, which is processed. 3. It has a semiconductor light emitting element and an optical fiber whose optical coupling end faces the output surface of the light emitting element, the light emitting element is provided on the bottom of the stem via a submount, and the optical fiber is attached to the stem. In a semiconductor light emitting device with an optical fiber, the optical coupling end side of which passes through a fiber guide provided on a side surface of the light emitting element and is supported by a fiber support provided near the light emitting element, wherein the fiber support and the fiber guide are connected to each other. When the length to the tip of the protrusion is A, and the length from the tip of the protrusion of the fiber guide to the end surface of the side surface of the fiber guide is B, the combination of the optical fiber, the material of the stem, and the material of the fiber guide is as described above. length A and B
A semiconductor light emitting device with an optical fiber, which is selected based on the correlation between the ratio A/B. 4. A quartz fiber is used as the optical fiber, Kovar material is used as the stem material, and Fe-
Using 42Ni-6Cr alloy material, the ratio of length A and B is A/B.
3. A semiconductor light emitting device with an optical fiber according to claim 3, wherein: 1.1. 5. Using a quartz fiber as the optical fiber, using Kovar material as the stem material, and using Fe-50Ni alloy material as the fiber guide material, the ratio A/B of length A and B.
3. A semiconductor light emitting device with an optical fiber according to claim 3, characterized in that 1.3.