JPH0560929A - Cross optical waveguide - Google Patents

Abstract

PURPOSE:To reduce the optical coupling loss by making the width or/and the thickness of optical waveguides in the vicinity of an intersection smaller than those in the other parts. CONSTITUTION:The width of an intersection 14 is made narrower than width W0 of waveguides in the other parts, and parts on the intersection 14 side of optical waveguides 11, 12, and 13 connected to the intersection 14 are formed into taper parts 11a, 12a, and 13a where the width of waveguides is gradually reduced toward the intersection 14. Therefore, the gap D1 of the intersection 14 becomes fairly small. When this cross optical waveguide is actually produced, the width of each of taper parts 11a, 12a, and 13a of optical waveguides 11, 12, and 13 is changed from W0, to W', and waveguide width W' and gap D' of an actual intersection 14A are shorter than the conventional waveguide width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact and low loss cross type optical waveguide.

[0002]

2. Description of the Related Art FIG. 5 shows a structural example of a conventional crossed optical waveguide. In the figure, 1 is an input optical waveguide, 2 is an output optical waveguide, 3 is an optical waveguide intersecting the input / output optical waveguides 1 and 2 (herein referred to as an external optical waveguide), 4 is an input / output optical waveguide 1, Intersections 5 between 2 and the external optical waveguide 3 are substrates. In such a crossed optical waveguide, light enters from the input optical waveguide 1 and exits from the output optical waveguide 2. At this time, the external optical waveguide 3 and the input / output optical waveguide 1,
At the intersection 4 where 2 and 2 intersect, the guided light is at the intersection 4
Is regarded as a gap and propagated. When the spot size of light propagating through the input optical waveguide 1 and the output optical waveguide 2 is w and the gap width at the intersection is D, the coupling efficiency η of coupling from the input optical waveguide 1 to the output optical waveguide 2 is η = 4 / (4+ (λD / πw ² ) ² ) (1) Λ is the wavelength of light in the optical waveguide. For example, if the equivalent refractive index n _eff of the optical waveguide is _3.3 and the wavelength λ ₀ used in vacuum is 1.5 5 μm, the wavelength λ in the optical waveguide is , Λ ₀ / n _eff , that is, 0.47 μm.

[0003]

In the above-mentioned conventional cross-type optical waveguide, since the input / output optical waveguides 1 and 2 and the external optical waveguide 3 both intersect at equal and right angles, the formula (1)
The gap width D at is about the waveguide width w ₀ . Since the waveguide width is about 2 μm, the coupling loss of the two optical waveguides at this gap (intersection 4) is 0.1.
There is a problem that it is relatively large at about dB. Further, in an actual cross-shaped optical waveguide, a rounding occurs at the crossing portion of the two optical waveguides due to resist pattern rounding at the time of manufacture, resulting in a crossing portion 4A as shown in FIG. In this case, the gap D ₀ of the intersection 4A when light propagates from the input optical waveguide 1 to the output optical waveguide becomes larger than that in the case of FIG. Assuming that the spot size w of the optical waveguide is 1 μm and the gap D ₀ at the intersection 4A caused by the rounding of the resist pattern is 3 μm, the coupling loss from the input optical waveguide 1 to the output optical waveguide 2 is 0.23 dB. And become even bigger. When the number of intersections 4A increases as in an optical switch, the optical coupling loss at the intersections 4A is also added and becomes too large to be ignored.

In view of such circumstances, it is an object of the present invention to provide a small-sized and low-loss cross type optical waveguide in which the optical coupling loss at the crossing portion is reduced.

[0005]

The cross-shaped optical waveguide according to the present invention which achieves the above-mentioned object, is a cross-shaped optical waveguide in which two or more optical waveguides intersect in the same plane. Alternatively, the thickness or both of them are made smaller than the value of the optical waveguide other than the intersection, and the spot size of the intersection is made larger than the spot size of the optical waveguide other than the intersection.

[0006]

In the crossed optical waveguide having the above structure, since the width and thickness of the crossing portion are smaller than the others, the spot size of the guided light becomes larger than the spot size of the guided light other than the crossing portion, and the coupling loss at the crossing portion becomes small. ..

[0007]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 is a block diagram of an intersecting optical waveguide according to an embodiment. In the figure, 11 is an input optical waveguide, 12 is an output optical waveguide, and 13 is an input / output optical waveguide 11, 12. External optical waveguides, and 14 are input / output optical waveguides 11 and 12
And an external optical waveguide 13 intersects with each other, and 15 shows a substrate. In this embodiment, the width of the crossing portion 14 is smaller than the width W _{0 of the} waveguide other than the crossing portion 14. Therefore, the crossing portion 14 side of each of the optical waveguides 11, 12, 13 connected to the crossing portion 14 is ,
Tapered portion 11 in which the width of the waveguide gradually decreases toward the crossing portion 14
a, 12a, 13a. Therefore, the gap D ₁ of the intersection 14 is considerably small. FIG. 2 shows a state in which the roundness of the resist pattern is taken into consideration when actually manufacturing the crossed optical waveguide of FIG. In this case, the waveguide widths of the tapered portions 11a, 12a, 13a of the optical waveguides 11, 12, 13 are set to change from W ₀ to W ′, and the actual waveguide width of the intersection 14A is W. , And the gap becomes D ′, the waveguide width W ′ and the gap D ′ are smaller than the conventional waveguide width W ₀ and gap D ₀ .

FIG. 3 shows the relationship between the waveguide width W and the spot size w. From the figure, it can be seen that the spot size can be increased from w ₀ to w ′ by making the waveguide width W ′ of the intersection 14A smaller than the waveguide width W ₀ of portions other than the intersection. FIG. 4 shows the relationship between the intersection gap D and the coupling loss at various spot sizes. From the figure, it is understood that the smaller the gap D at the intersection and the larger the spot size w, the smaller the coupling loss between the input optical waveguide and the output optical waveguide.

Therefore, in the crossed optical waveguide of the above-mentioned embodiment in which the waveguide width of the crossing portion 14A is reduced to W'and the gap is reduced to D ', the coupling loss between the two optical waveguides 11 and 12 is reduced. can do.

In the above embodiment, the optical waveguide width W at the intersection
However, the spot size of the guided light at the intersection can be increased even if the thickness or width of the optical waveguide at the intersection is reduced, and the coupling loss between the input optical waveguide and the output optical waveguide can be increased. Can be reduced.

[0012]

As described above, according to the present invention, the spot size is increased by making the width and / or thickness of the optical waveguide near the intersection smaller than that of the optical waveguide other than near the intersection. Since the gap D at the intersecting portion is made small, it is possible to form an intersecting optical waveguide with low loss.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a crossed optical waveguide according to an embodiment.

FIG. 2 is an explanatory diagram showing an actual cross-shaped optical waveguide of one embodiment.

FIG. 3 is a diagram showing a relationship between a waveguide width W and a spot size w.

FIG. 4 is a diagram showing a relationship between a gap width D at an intersection and a coupling efficiency η at various spot sizes.

FIG. 5 is a configuration diagram of a cross-shaped optical waveguide according to a conventional technique.

FIG. 6 is an explanatory diagram showing an actual cross-shaped optical waveguide in a conventional type.

[Explanation of symbols]

 11 Input Optical Waveguide 12 Output Optical Waveguide 13 External Optical Waveguide 14, 14A Intersection 15 Substrate

Claims (1)

[Claims] 1. In an intersecting optical waveguide in which two or more optical waveguides intersect in the same plane, the width and / or thickness of the optical waveguides at the intersections are made smaller than the values of the optical waveguides other than the intersections. A cross-shaped optical waveguide, wherein the spot size of the intersection is larger than the spot size of the optical waveguide other than the intersection.