JPS62118303A - Distributed index lens - Google Patents

Abstract

PURPOSE:To facilitate the positioning of a distributed index lens relatively to a fine optical element such as a semiconductor laser and an optical fiber and to mount it by easily inserting into a narrow part by forming the end part of the distributed index lens on the side of a spot light source in a conic shape and pointing the tip. CONSTITUTION:Distributed index lenses 11 and 11 are arranged on both end surfaces of the semiconductor laser 6 opposite each other. The distributed index lenses 11 and 11 become <=200mum in the diameters of upper bases 14 and 14 and the size of the semiconductor laser 6, on the other hand, is about 100mum, so the upper bases of the distributed index lenses are much less in area than before. Consequently, the operating distance of the distributed index lenses is 10mum or short, necessary axial positioning for aligning the optical axes of the lenses with projection light and operation for obtaining the parallism between both opposite surfaces are easily carried out over an observation through a microscope. Further, the distributed index lenses 11 are formed in the shape of a frustum of right circular cone and then the lenses are mounted in the narrow space on the side of the slanting surface 15 of a heat sink 92.

Description

[Detailed Description of the Invention] [Summary] In a refractive index gradient lens, when collimating light emitted from a point light source into parallel light, the end on the point light source side is tilted only at the outer periphery that does not interfere with the luminous flux. By removing it and forming it in the shape of a truncated cone, etc., it becomes easier to connect it to other microscopic optical components.

[Industrial application field]

The present invention relates to a gradient index lens used to collimate light emitted from a semiconductor laser, an optical fiber, or the like, or to converge parallel light.

[Conventional technology]

With technological advances in semiconductor lasers and optical fibers, the proportion of optical components has increased, and miniaturization and higher efficiency are being considered for high-density packaging.

Further, with the progress of gradient index lenses, they are being put into practical use for collimating and condensing light emitted from semiconductor lasers and optical fibers. However, gradient index lenses have a short working distance and their diameter is large compared to the light emitting part of a semiconductor laser or the core diameter of an optical fiber, so placement is inevitably restricted, and positioning is difficult. is also difficult.

FIG. 5(a) is a cross section of the gradient index lens 1, and FIG. 5(b) is a diagram showing the characteristics of the gradient index lens. As shown in (b), the gradient index lens 1 exhibits a lens effect because the refractive index n is distributed parabolically from the central axis C toward the outer circumference.

This gradient index lens 1 has a cylindrical shape as shown in FIG. 6, and the light incident from the point light source 2 at the end is 3
It exhibits a meandering period as shown in .

Therefore, if a gradient index lens with a meandering period of 1/4 of the length is used, collimation as shown in FIG. 7(a) or light condensation as shown in FIG.

In (a) of FIG. 7, light incident from a point light source 2 is converted into parallel light 4 by the gradient index lens 1 and output. vice versa,
As shown in FIG. 7(B), when parallel light 5 enters from the opposite side, it is condensed by the gradient index lens 1 and focused at the position of the point light source 2 shown in FIG. 7(A).

Gradient index lenses have a narrow diameter of about 2mm, so
It was said to be suitable for handling light emitted from minute elements such as semiconductor lasers and optical fibers. However, when adjusting the working distance or aligning the optical axis, it is difficult to use a semiconductor laser with a size of 0.1 mm or a diameter of 0.2 mm.
Compared to an optical fiber, the diameter of a gradient index lens is 2
Because it is large (mm), the work is difficult.

FIG. 8 is a side view showing how a conventional semiconductor laser is used. 6 is a semiconductor laser, and laser light 7 is emitted from both end faces.
．． Emits 8. The semiconductor laser 6 is mounted on a heat sink 91 with excellent heat conduction for heat radiation, and the heat sink 91 is further mounted on a block 10 made of copper or the like. In order to sufficiently dissipate the heat generated by the semiconductor laser 6, the size of the heat sink 91 must have a satisfactory strength and heat capacity. As a result, the output light from one side is 8
hits the heat sink 91 and cannot be used, so only one output light 7 is used. Therefore, at present, the light 8 emitted from the back side is only used for roughly monitoring the light intensity.

[Problem that the invention seeks to solve]

By the way, in order to extract the emitted light 7 with the gradient index lens 1, it is necessary to align the optical axis and to align the end face of the semiconductor laser 6 and the incident surface of the gradient index lens. 1 has a short working distance of 10 μm at WD7, so even with a gradient index lens with a diameter of about 2 mm, it is difficult to align the optical axis and parallelism so that the gap with the semiconductor laser 6 is 10 μm. be. Also, the emitted light 7
On the side, since the heat sink 91 stands vertically,
Although it is time-consuming, it is not impossible to implement.

On the other hand, as shown in FIG. 9, if a heat sink 92 is used that has the side of the emitted light 8 cut out diagonally, the emitted light 8 will not hit, so it is possible to effectively utilize the emitted light from both sides. . However, the heat sink 92 makes coupling with the gradient index lens impossible.

The technical problem of the present invention is to eliminate such inconvenience when using a gradient index lens, and to solve the problem of using a gradient index lens, even if the optical element used in pair with the gradient index lens is a minute component.
The purpose is to ensure sufficient alignment and to enable mounting in narrow locations.

[Means for solving problems]

FIG. 1 is a front view and a right side view illustrating the basic principle of a gradient index lens according to the present invention. Reference numeral 11 denotes a gradient index lens, which has a lens effect by having a refractive index that gradually decreases from the central axis C toward the outer circumference.

In such a gradient index lens, the end portion is 12
As shown, it is cut diagonally and has a pointed tip. The pointed end 13 serves as the end on the point light source 2 side when collimating the light emitted from the point light source 2 into parallel light 4.
Only the outer peripheral portion that does not interfere with the light beam 3 is obliquely removed as shown by 12.

(Function) In the gradient index lens 11 of the present invention, when the meandering period of the light ray in the lens is 1/4, when the light ray enters the gradient index lens 11 from the point light source 2, the gradient index lens 11 When passing through, it is collimated and becomes parallel light 4.

At this time, since the light beam 3 passes inside the slope I2 of the truncated conical portion (3), the collimation effect is not inhibited by sharpening the end portion into a truncated conical shape or the like.

Conversely, when parallel light enters from the parallel light 4 side, it is focused at the point light source position 2 due to the condensing action. In this case as well, since the convergent light passes inside the slope 12, no problem arises due to the truncated cone shape.

When collimating the light incident from the point light source 2, an emitting part such as a semiconductor laser or an optical fiber is arranged on the end face (upper base) 14 on the truncated conical part 13 side. Gradient index lens 1
1 for condensing light, the end surface 14 of the truncated conical portion 13
Place the light receiving section on the side.

〔Example〕

Next, examples will be used to explain how the gradient index lens according to the present invention is actually implemented.

FIG. 2 is a side view showing an example in which the gradient index lens according to the present invention is used to collimate semiconductor laser light. The heat sink 92 on which the semiconductor laser 6 is mounted has a trapezoidal shape with both sides inclined, unlike the case shown in FIG. Then, gradient index lenses 1 are placed on both end surfaces of the semiconductor laser 6.
1.11 are arranged facing each other. That is, the upper base surface 14 of the truncated conical portion 13.13 of the gradient index lens 11.11.
．． 14 faces the re-emission end face of the semiconductor laser 6.

By forming the refractive index gradient lens 11.11 in the shape of a truncated cone, the diameter of the upper base 14.14 is approximately 200 μm or less. The top area of the distributed lens is extremely small compared to conventional lenses. As a result, even if the working distance of a gradient index lens is as short as 10 μm, it is easy to align the optical axis of the lens with that of the output light and to align the parallelism between opposing surfaces while looking through a microscope. can be done.

Furthermore, since the gradient index lens 11 has a truncated conical shape,
It becomes possible to mount the heat sink 92 even in a narrow space on the slope 15 side. Therefore, both sides have slopes 15
By doing so, the heat sink can be made larger to increase its heat capacity, and the area for mounting it on the block 10 can be expanded. By forming the gradient index lens in the shape of a truncated cone in this manner, it becomes possible to mount the semiconductor laser on the emission surface.

Note that the angle θ of the slope polishing can be determined by the numerical aperture of the gradient index lens. When the numerical aperture NA=0.6, it is about 45°. Furthermore, instead of having a truncated conical shape, it may be made into a curved surface along the light beam 3 as long as it does not interfere with the light beam 3 shown in FIG. 1, but processing is troublesome.

[Processing method of truncated conical part]

In order to form the truncated conical part 13 at the end of the gradient index lens, as shown in FIG. By polishing the end portion diagonally, a slope 12 can be formed as shown in (b). Alternatively, as shown in FIG. 4(a), the tip is conically shaped in advance, and then the apex of the lens is flat-polished as shown in FIG. 4(b) until the upper base 14 has a predetermined diameter.

〔Effect of the invention〕

As described above, according to the present invention, the end of the gradient index lens on the point light source side is formed into a truncated cone shape with a pointed tip, so that it can be used for micro-optics such as semiconductor lasers and optical fibers. It becomes easy to align with the element, and it also becomes possible to easily insert and mount it in a narrow part. As a result, we are able to meet the demands for high-density mounting of optical components.
The range of applications for gradient index lenses will also be expanded.

[Brief explanation of drawings]

Figure 1 is a front view and right side view illustrating the basic principle of the gradient index lens according to the present invention, and Figure 2 is a side view of an example in which the gradient index lens according to the present invention is used to collimate semiconductor laser light. Figures 3 and 4 are side views illustrating the method for manufacturing a gradient index lens of the present invention, and Figure 5 and the following are related to conventional gradient index lenses; Figure 6 is a longitudinal sectional view showing the meandering periodic characteristics of the luminous flux of the gradient index lens, Figure 7 is a sectional view showing the collimating action and focusing function of the gradient index lens. FIGS. 8 and 9 are side views showing an example of application of a gradient index lens in a semiconductor laser. In the figure, 1.11 is a gradient index lens, 2 is a point light source, 3 is a luminous flux, 4 is parallel light, 6 is a semiconductor laser, and 7.8
is the emitted light, 91.92 is the heat sink, 12 is the slope, 1
3 indicates a truncated conical portion, and 14 indicates an end surface (upper base). Patent Applicant: Fujitsu Ltd. Agent, Patent Attorney: Aoyagi Hoki “Basics of Flour”! Fig. 1 *;S example of the present invention Fig. 2 Fig. 5 Meandering flow of the bundle Fig. 6 Good Fig. 4 Collimating and gathering of the shiva wheel now cloth l/cis Fig. 7

Claims (1)

[Claims] In a gradient index lens that has a lens effect due to the refractive index gradually decreasing from the central axis (c) toward the outer periphery, the light emitted from a point light source (2) is collimated into parallel light. A gradient index lens characterized in that the end portion on the point light source (2) side is sharpened by obliquely removing only the outer peripheral portion that does not interfere with the light beam (3).