JPS585412B2 - Optical fiber with spherical lens body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an end face structure of an optical fiber that allows highly efficient coupling with a semiconductor light emitting device.

Low-loss optical fibers used in optical communications have a low transmission loss and can transmit up to high frequency bands, and have a small effective acceptance angle of about 10 degrees or less.

On the other hand, the directivity of the output light of a semiconductor light emitting device suitable as a light source for optical communication is that the half-value angle of the emission intensity is approximately 40 for a semiconductor laser.
100° for light emitting diodes (hereinafter referred to as LEDs)
It is about °.

For the above reasons, when a semiconductor light emitting element is directly coupled to a flat-end low-loss optical fiber, the coupling efficiency is low, and in the case of an LED, it is several percent or less of the total light emission output.

The following document shows that one way to increase the coupling efficiency between a semiconductor light emitting device and a low-loss optical fiber is to provide a lens effect to the end face of the optical fiber to increase the effective acceptance angle of the optical fiber. It is known from (i) and (ii).

(1) Kato Journal of Applied Physics (J, Appl Phys) Vol. 44. No
, 6゜2756 pages (1973) (ii) Kawasaki Johnson Optical and Qu Electronics
antum Electronics) 71281 page 1
1 shows a conventional structure in which the end face of this type of optical fiber has a lens effect.

In the structure shown in FIG. 1, the end face of the optical fiber is processed into a spherical shape, and a lens effect is obtained by the difference in refractive index on this spherical surface.

The conventional method described above has the following drawbacks.

The material forming the spherical surface that provides the lens effect is limited to the material of the optical fiber.

Since the refractive index of the material of the low-loss optical fiber is between 1.4 and 1.5, the difference in refractive index on the spherical surface cannot be greater than 0.5,
There is a limit to how much the lens effect can be enhanced by increasing the refractive index difference.

As the refractive index of the medium in contact with the end face of the optical fiber becomes larger than 1.0, the difference in refractive index becomes smaller and the lens effect becomes weaker, and when the refractive index of the medium reaches the refractive index of the material of the optical fiber, the lens effect disappears. It ends up.

Therefore, the refractive index of the medium in contact with the end face of the optical fiber is 1.0.
limited to air, etc.

The present invention aims to eliminate the above-mentioned drawbacks of the conventional lens by providing a structure in which a spherical lens body whose refractive index can be arbitrarily selected is fitted into the center of the optical fiber end face through a fitting hole.

A specific embodiment of the present invention is shown in FIG.

In the figure, 1 is an optical fiber, and 2 is a fitting hole formed so that its center coincides with the end surface of the optical fiber 1, and has a diameter of 80 μm and a depth of 15 μm, for example.

3 is a spherical lens body in which a part of the spherical surface is firmly fitted to the periphery of the fitting hole 2, and in this example, it has a diameter of 150 μm and a refractive index of 2.
．． 0 glass bulb was used.

4 is an adhesive for fixing the spherical lens body 3 to the optical fiber 1, and in this example, epoxy resin was used.

In this embodiment, the refractive index of the spherical lens body 3 is set to 2.0, and in the structure of the present invention, a material different from the material of the optical fiber can be arbitrarily used for the spherical lens body 3. By arbitrarily changing the refractive index of 3, the refractive index difference can be freely given.

Therefore, the lens effect at the end face of the optical fiber can be selected in accordance with the conditions for coupling with the semiconductor light emitting device.

In addition, since the spherical lens body 3 is fitted into the fitting hole 2 whose center coincides with the end surface of the optical fiber 1, it can be placed at the center of the optical fiber 1 with high precision, and the fine structure (the diameter of the low-loss optical fiber is 100~ It is about 200 μm.

), it is easy to assemble and has good reproducibility.

Furthermore, in the structure of the present invention shown in FIG. 2, if the spherical lens body 3 is made of a material with a sufficiently high refractive index, such as chalcogenide glass with a refractive index of 2.6, the medium surrounding the end face of the optical fiber has a refractive index higher than that of air. Since a sufficient lens effect can be obtained even with a material (the refractive index of epoxy resin is about 1.5), highly efficient coupling can be obtained even when molded with resin.

As described above, the end face configuration of the optical fiber according to the present invention can obtain optimal characteristics by arbitrarily controlling the reflection effect, is easy to assemble with high precision, has good reproducibility, and has a high refractive index. It is possible to achieve highly efficient coupling with a semiconductor light emitting device, including the possibility of highly efficient coupling with a sufficient lens effect even in a surrounding medium (for example, epoxy resin) whose temperature is higher than that of air, making it extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a conventional optical fiber, and FIG. 2 is a structural diagram of an end portion of an optical fiber with a spherical lens body according to the present invention. In the figure, 1 is an optical fiber, 2 is a fitting hole formed in the end face of the optical fiber 1, 3 is a spherical lens body inscribed in the periphery of the fitting hole 2, and 4 is an adhesive.

Claims (1)

[Claims] 1. A circular fitting hole is formed in the end face of the optical fiber with the axis of the fiber as the center, and the hole is made of a material that is transparent to the wavelength of the light propagating through the optical fiber, and has a diameter that is equal to or larger than the diameter of the fitting hole. A spherical lens body having a part of a spherical surface inscribed in the periphery of the fitting hole, and the spherical lens body is fixed to the end face of the optical fiber so as to be located over the center of the end face of the optical fiber. An optical fiber with a spherical lens body.