JPS5922204B2 - How to couple optical semiconductor elements and optical fibers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coupling an optical semiconductor element such as an LD or an LED to an optical fiber in order to match the optical output of the optical semiconductor element to the optical fiber.

Spherical lens optical systems for optical matching include a combination lens made up of multiple convex lenses and concave lenses glued together, or a lens with a large refractive index at the center and a nearly parabolic index toward the periphery. Conventionally, rod lenses and the like have been used to reduce the optical axis of each lens, but combination lenses require a great deal of time and effort to align the optical axes of each lens during bonding, and small combination lenses used for optical fibers The radius of curvature of the lens is extremely small, making polishing difficult. In addition, the head nodule lens not only has the disadvantage that it is difficult to control the manufacturing precision of the refractive index distribution, but also that the lens must actually be cut into a highly precise length through the light beam, which also requires a great deal of time and effort. The present invention is intended to solve these problems, and an object of the present invention is to provide a method for coupling an optical semiconductor element and an optical fiber, which can efficiently match the optical output from an optical semiconductor element to an optical fiber. This is what I did.

Embodiments of the invention will be described below with reference to the drawings.

In FIG. 1, 1 is a sphere made of an optical material such as glass aquarium, ruby, etc., and 2 and 3 are wrapped around the sphere 1.
The sphere 1 is inserted into a two-split mold (not shown) that forms a cylindrical groove with a diameter equal to that of the sphere 1 with a cylindrical outer envelope made of an optical material such as glass or acrylic, and the cylindrical groove is An optical material such as glass or acrylic is press-fitted from both sides of the column to form a cylindrical outer enclosure 2.

In FIG. 2, 4 is a sphere similar to the above, and 5 is a cylindrical outer enclosure formed in the same manner as above.

The ball lens optical system shown in Fig. 1 is polished using a centerless grinder to have the same diameter as the outer part of the ball lens optical system shown in Fig. 2 (Fig. 3), and then mechanically inserted into a V-groove. By aligning the optical axis and bonding, the ball lens optical system 6 shown in FIG. 4 can be obtained. As shown in FIG. 5, the optical fiber 1 is connected to this ball lens optical system 6 by fusion splicing or by adhesion using a lens bond or the like to integrate the two.
2 is connected to an optical semiconductor element 8 such as an LED.

In this case as well, the optical axes of the ball lens system 6 and the optical fiber T can be easily and precisely aligned using the V-groove.
Here, the design conditions of the ball lenses 1, 4, etc. will be explained.
In Fig. 6, 8 is a single mode LD, and 9 is an LD.
In the far-field image on the x-y plane according to 8, is the optical power spread angle of the x-direction light, and θ is the optical power spread angle of the y-direction.

Generally, due to the interference effect, it spreads greatly in the y direction, and θ is about 50 to 60 degrees, and θ is about 15 degrees.

In addition, as shown in FIG. 7, the active layer 1 of the LD8
Let the length of 0 in the x direction be X, and the length in the y direction be y1.
Normally, X1 is l~20μM, y is 0.1~2μm, so the core diameter of the optical fiber 7 is 2a, the radius of the lens sphere 4 is R, the focal length is F, and the radius of the lens sphere 1 is R2
, the focal length is F2, and the relative refractive index of each lens sphere is Nr, and the lens conditions for optimal coupling of the above LD 8 and optical fiber 7 are found.However, in the case of lens spheres, F,=''? The relative refractive index Nr of the lens sphere is determined from equation (1) based on the angle of spread of the effective power based on actual measurements.

Also, 2r,=2a・・・・・・・・・(2)(
The radius R of the lens sphere 4 is determined from equation 2).

On the other hand, if the numerical aperture of the optical fiber 1 is NA, then the optimum radius R2 of the lens sphere 1 can be determined from equation (3) or equation (4). As explained above, according to the present invention, it is possible to easily obtain a spherical lens optical system with an accurate predetermined diameter by using a centerless grinder and a groove, and by appropriately selecting lens conditions, Optical output can be efficiently matched to the optical fiber.

[Brief explanation of drawings]

Figures 1 and 2 are front views of a spherical lens optical system consisting of a sphere and a cylindrical envelope, Figure 3 is a front view of the lens shown in Figure 1 polished to a predetermined diameter, and Figure 4. is a front view of a ball lens optical system that integrates what is shown in FIG. 2 and what is shown in FIG. 3, FIG. 5 is a front view of an embodiment of the optical semiconductor device matching circuit according to the present invention, and FIG. FIG. 7 is a perspective view showing a far-field image of the optical semiconductor element, and FIG. 7 is a side view of the optical semiconductor element.

Claims (1)

[Claims] 1. An optical semiconductor element characterized in that light from the optical semiconductor element is made to enter an optical fiber through a spherical lens optical system formed by surrounding a sphere made of an optical material with a cylindrical envelope made of an optical material. and optical fiber coupling methods.