JPS6159406A - Optical coupling structure of planar type light guide and its manufacture - Google Patents

Abstract

PURPOSE:To eliminate the need to optical axis adjustment between a condenser lens and a light guide and to reduce Fresnel loss by forming the condenser lens on and end surface of the light guide in one body for the optical coupling structure between the planar type light guide and a light source. CONSTITUTION:The light guide 2 is formed on a substrate 3, and the condenser lens 4 for guiding projection light 5 from the light source 1 in the light guide 2 is formed integrally on the end surface of the light guide 2. This lens 4 can be formed by a dip method. Namely, the end-surface side edge of the light guide 2 on the substrate 3 is dipped in a liquid lens material which is transparent and has high viscosity normally, and the substrate 3 is lifted vertically; and the lens material is set at time in a drop shape at the edge, thus forming the lens 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to optical transmission technology, and particularly to an optical coupling structure between a planar light guide and a light source, and a method for manufacturing the same.

Optical fibers are mainly used as a means of optical transmission, but
In recent years, dielectric materials such as lithium niobate (LiNbo3) and quartz (S102) or gallium arsenide (Ga
Planar light guides formed on the surface of a substrate made of a semiconductor such as As) have been put into practical use. On the other hand, light sources for light transmitted using such a light guide P include light emitting diodes (LEDs) and semiconductor laser diodes (LDs).
are commonly used.

[Prior art and problems to be solved by the invention] Conventionally, optical coupling between the planar light guide and the light source as described above has been achieved by placing a ball lens or the like in the space between the two, and using this to remove light from the light source. It is configured to condense the emitted light and introduce it into the end face of the light guide. However, this structure requires highly accurate optical axis adjustment between the light source and the lens l'18, as well as between the lens and the light guide, and there is a problem that assembly work is complicated.

Additionally, the presence of the lens increases the number of interfaces between the media, resulting in a problem of large Fresnel loss.

[Means for solving problems]

In order to solve the above problems, the present invention provides an optical coupling structure between a planar light guide and a light source, in which a condensing lens for introducing light emitted from the light source into the light guide is integrally formed on the end face of the light guide. This is what I did.

The present invention also provides a method for integrally forming a condensing lens on the end face of such a planar light guide,
This method involves dipping the edge of the light guide side of the substrate into a transparent lens material, usually a relatively viscous liquid, and then lifting the substrate vertically, leaving behind droplets on the edge of the substrate. The condensing lens is formed by curing the lens material that hangs down in the shape.

[Function] In the optical coupling structure according to the present invention, the condenser lens integrally formed on the end face of the light guide eliminates the need for optical axis adjustment between the condenser lens and the light guide, and reduces the number of inter-medium interfaces that are broken. It acts to reduce.

Furthermore, according to the method for integrally forming a condenser lens according to the present invention, the surface tension of the lens material hanging down from the edge of the substrate makes it possible to easily form a condenser lens having an ideal shape.

〔Example〕

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

FIG. 1 is a schematic side view of an embodiment of an optical coupling structure between a planar light guide and a light source according to the present invention.

In the figure, reference numeral 1 indicates a light source, which is, for example, a semiconductor laser diode. Further, the reference numeral 2 indicates a planar type light guide (hereinafter simply abbreviated as "one light guide"). I like this light
-'2 is formed on the substrate 3 of Tsukishima 03, and metal titanium (Ti) is formed on the surface of the substrate 3 with a thickness of about 0.5 mm in a desired pattern with a width of several kilometers and a thickness of several hundred. This is heated at about 1000℃ for several hours and T! LiNbO5
The light guide 2 formed by this heat diffusion has a slightly larger refractive index than the rest of the light guide 2, so that the light guide 2 has a slightly larger refractive index than the other parts. When the light is introduced, the light is confined within the id 2 and transmitted. FIG. 2(A) is a partial perspective view of the light guide 2 and the substrate 30.

Next, reference numeral 4 indicates a condensing lens for introducing the emitted light 5 from the light source 1 into the light guide 2, and this lens 4 is integrally formed on the end surface of the light guide 2.

FIG. 2(B) is a partial perspective view of a state in which the lens 4 is integrally formed.

This lens 4 can be formed by a dipping method as shown in FIG. First, reference numeral 1o indicates a tank containing lens material 11. As the lens material 11, a transparent and usually relatively highly viscous liquid material that can be cured by means such as heat or light, such as r Optical Cement UV-71J manufactured by Summers Laboratories in the United States, is used. . This is cured by UV irradiation. Then, as shown in FIG. 3(A), the edge of the optical guide 2 of the substrate 3 as shown in FIG. 2(A) is dipped into this lens material 11. After a few seconds, the substrate 3 is gently pulled up vertically as shown in FIG. 3(b). At this time, the lens material attached to the substrate 3 hangs down to the edge of the substrate in the form of drops as shown by reference numeral 4a due to the effects of gravity and surface tension. If this is irradiated with ultraviolet rays and cured, it will be shown in Figure 2 (b).
As shown in FIG. 2, a condensing lens 4 having a substantially uniform cross-sectional shape is integrally formed along the edge of the substrate 3.

〔Effect of the invention〕

According to the optical coupling structure of the present invention, since the condenser lens 4 is integrally formed on the end face of the light guide 2, only the optical axis adjustment between the light source 1 and the light guide 2 (or the condenser lens 4) is required. Good and very easy to assemble. Furthermore, since the condensing lens is integrally formed, no other medium is interposed between the light guide 2 and the condensing lens 4, which reduces the number of interfaces between the media and reduces Fresnel loss.

Furthermore, according to the method of the present invention, the integral formation of the condensing lens 4 on the light guide 2 is very simple, and an ideal lens shape can be obtained. In particular, the lens formed by the method of the present invention does not have a lens effect in the in-plane direction of the substrate. However, in the case of a semiconductor laser diode, which is mainly used as a light source, the emitted light has a small spread in the direction parallel to the bonding surface of the active layer (that is, in the direction in the substrate plane), and has a small spread in the direction perpendicular to the bonding surface. Large axis asymmetry;
Therefore, a condensing lens as shown in the figure is extremely advantageous in terms of optical coupling. However, it is sufficient to say that it is practically effective even for devices whose emitted light is axially symmetrical, such as a light emitting diode. Furthermore, although the condensing lens 4 formed by the method of the present invention is symmetrical with respect to the center line of the substrate 3 as shown in FIG. It is an area. This is because one side of the light guide 2 is in contact with the substrate 3 and the other side is in contact with the air, so that an ideal lens effect can be obtained, considering that total reflection is different. still,
When it is desired to obtain a special lens shape, when the droplet-shaped lens material 4a is cured by ultraviolet irradiation as explained in FIG. be.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of an embodiment of the optical coupling structure between a planar light guide and a light source according to the present invention, and FIG. 2 is a partial perspective view of the light guide and the substrate, in which (a) shows the formation of a condenser lens. FIG. 3 is a diagram showing the previous state and the state after forming the condenser lens, and FIG. 3 is a diagram showing the method of integrally forming the condenser lens according to the present invention. DESCRIPTION OF SYMBOLS 1...Light source, 2...Light guide, 3...Substrate, 4...
... Condensing lens, 4a... Droplet lens material, 5...
Light, 10... Lens material tank, 11... Lens material.

Claims (1)

[Claims] 1. An optical coupling structure for coupling a light source to a planar light guide formed on the surface of a dielectric or semiconductor substrate, which structure is for introducing light emitted from the light source into the guide. A planar light guide characterized in that a condenser lens is integrally formed on an end face of the light guide. 2. A method of integrally forming a condensing lens on the end face of a planar light guide formed on the surface of a dielectric or semiconductor substrate for introducing light emitted from a light source into the planar light guide, which is transparent and Immersing the edge of the light guide end surface of the substrate in a lens material that is usually a liquid with relatively high viscosity;
A method characterized in that the substrate is then vertically pulled up, and the condensing lens is formed by curing the lens material that remains on the edge of the substrate and hangs down in the form of drops.