JPH09297228A - Array waveguide grating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an array waveguide grating having a flat light frequency characteristic. SOLUTION: In the array waveguide grating provided with a channel waveguide 12 for an input arranged on a substrate 11, the channel waveguide 13 for an output, a channel waveguide array 14, a first sector slab waveguide 15 and a second sector slab waveguide 16, cores of respective waveguides of the channel waveguide 12 for the input in the vicinity of the boundary with the first sector slab waveguide 15 are made a parabolic shape. Thus, a light distribution having a flat electric field distribution in the boundary between the second sector slab waveguide 16 and the channel waveguide 13 for the output is formed, and the flat light frequency characteristic nearly fixing a dividing output characteristic even when a wavelength (light frequency) of a light source is changed is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arrayed waveguide grating capable of realizing an optical multiplexer / demultiplexer having flat optical frequency characteristics.

[0002]

FIG. 1 shows an example of a conventional arrayed waveguide grating.
Here, an arrayed waveguide type optical multiplexer / demultiplexer is shown, in which an input channel waveguide 2, an output channel waveguide 3, a channel waveguide array 4, the input channel waveguide 2 and a channel A first fan-shaped slab waveguide for connecting to a waveguide array, and the channel waveguide array;
A second fan-shaped slab waveguide 6 for connecting the output channel waveguide 3 to the slab waveguide 6 is formed.

In this type of arrayed-waveguide type optical multiplexer / demultiplexer, the channel waveguide array 4 is constructed so that its length gradually increases with a predetermined waveguide length difference ΔL. Further, the cores of the respective waveguides of the input channel waveguide 2 and the channel waveguide array 4 in the vicinity of the boundary with the first fan-shaped slab waveguide 5 have a tapered shape which spreads linearly as shown in FIG. And the second fan-shaped slab waveguide 6
The cores of the respective waveguides of the output channel waveguide 3 and the channel waveguide array 4 in the vicinity of the boundary between and have a tapered shape that spreads linearly as shown in FIG.

2 and 3, R is the first and the first.
Radius of curvature of the second fan-shaped slab waveguides 5 and 6, U is the core opening width of the tapered waveguide of the input and output channel waveguides 2 and 3, S ₁ is the input and output channel waveguides 2, 3 is a distance, d ₁ is the length of the tapered waveguide of the input and output channel waveguides 2 and 3, D is the core opening width of the tapered waveguide of the channel waveguide array 4, and 2a is The core width of the channel waveguide portion, S ₂ is the interval between the channel waveguide arrays 4, and d ₂ is the length of the tapered waveguide of the channel waveguide array 4.

[0005]

FIG. 4 shows the optical frequency characteristics of the above-mentioned conventional arrayed waveguide grating. Parabolic loss characteristics in the vicinity of the center optical frequency of each waveguide (here, at 200 GHz intervals). Is doing. Therefore, if the wavelength (optical frequency) of the laser light source fluctuates from the central optical frequency of each signal channel (waveguide) due to temperature change or the like, there is a problem that the loss increases significantly.

An object of the present invention is to provide an arrayed waveguide grating having flat optical frequency characteristics.

[0007]

According to the present invention, in order to solve the above-mentioned problems, an input channel waveguide, an output channel waveguide, a channel waveguide array, and an input channel waveguide are arranged on a substrate. A first fan-shaped slab waveguide connecting the waveguide and the channel waveguide array, and a second fan-shaped slab waveguide connecting the channel waveguide array and the output channel waveguide.
And a fan-shaped slab waveguide, wherein the channel waveguide array length is sequentially increased by a predetermined waveguide length difference. We propose an arrayed waveguide grating in which the core of each waveguide of the input channel waveguide near the boundary has a parabolic shape.

According to the present invention, the core of each waveguide of the input channel waveguide in the vicinity of the boundary with the first fan-shaped slab waveguide has a parabolic shape, so that the second fan-shaped slab waveguide is formed. It is possible to form a light distribution with a flat electric field distribution at the boundary between the output and the channel waveguide for output, which makes the demultiplexing output characteristic almost constant even if the wavelength (optical frequency) of the light source changes. An arrayed waveguide grating having optical frequency characteristics can be provided, and an optical multiplexer / demultiplexer suitable for large-capacity / long-distance optical communication and wavelength division routing can be realized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 5 shows an embodiment of an arrayed-waveguide grating of the present invention, which is an arrayed-waveguide type optical multiplexer / demultiplexer, in which an input channel waveguide 12 and an output channel are formed on a substrate 11. Waveguide 13, channel waveguide array 14,
A first fan-shaped slab waveguide 15 for connecting the input channel waveguide 12 and the channel waveguide array 14, and a second fan-shaped slab waveguide 15 for connecting the channel waveguide array 14 and the output channel waveguide 13 A slab waveguide 16 is formed.

The channel waveguide array 14 is constructed so that its length is gradually increased by a predetermined waveguide length difference ΔL. Further, the core of each waveguide of the input channel waveguide 12 in the vicinity of the boundary with the first fan-shaped slab waveguide 15 is
As shown in FIG. 6, it has a parabolic shape. The core of each waveguide of the channel waveguide array 14 in the vicinity of the boundary with the first fan-shaped slab waveguide 15 has a tapered shape that spreads linearly.

In FIG. 6, R is the radius of curvature of the first fan-shaped slab waveguide 15, and W is the input channel waveguide 1.
2, the core opening width of the parabolic waveguide, S ₁ is the interval between the input channel waveguides 12, l ₁ is the length of the parabolic waveguide of the input channel waveguide 12, and D is the channel waveguide array 14 The core opening width of the tapered waveguide of 2
a is the core width of the channel waveguide portion, S ₂ is the spacing between the channel waveguide arrays 14, and d ₂ is the channel waveguide array 14
Is the length of the tapered waveguide.

The parabolic shape of the core of each waveguide of the input channel waveguide 12 near the boundary with the first fan-shaped slab waveguide 15 is y = (1 / A) (a) as shown in FIG. ²⁻ x ² ) (where A is a parameter that specifies the parabolic shape, and a is ½ of the core width).

Here, in FIG. 5, an optical frequency f (wavelength λ = c / is assigned to one port of the input channel waveguide 12).
f: However, consider the case where signal light of (c is the speed of light) is incident.

The incident light forms a parallel-beam-shaped light distribution when passing through the parabola-shaped region shown in FIG. 6, and as shown in FIG. 8 at the boundary with the first fan-shaped slab waveguide 15. It produces a spatially flat electric field distribution. Core width 2
a = 7 μm, core thickness 2t = 7 μm, refractive index difference Δ = 0.7
In the case of a 5% optical waveguide, the structural parameters for obtaining the flat light distribution as shown in FIG. 8 are A = 1.0 and l ₁ =
250 μm.

The light having the flat distribution thus obtained further spreads laterally in the first fan-shaped slab waveguide 15 and excites each waveguide of the channel waveguide array 14, In the second fan-shaped slab waveguide 16, the light is focused at the position of the output channel waveguide 13 corresponding to the optical frequency f.

At this time, due to the reciprocity theorem, the light distribution at the boundary between the second fan-shaped slab waveguide 16 and the output channel waveguide 13 is also a flat light distribution as shown in FIG. Become.

FIG. 10 is an enlarged view of the vicinity of the second fan-shaped slab waveguide 16. Each of the output channel waveguide 13 and the channel waveguide array 14 near the boundary with the second fan-shaped slab waveguide 16. The core of the waveguide has a tapered shape that spreads linearly.

In FIG. 10, R is the radius of curvature of the second fan-shaped slab waveguide 16, U is the core opening width of the tapered waveguide of the output channel waveguide 13, and S ₁ is the output channel waveguide 13. , D ₁ is the output channel waveguide 13
Of the tapered waveguide, D is the core opening width of the tapered waveguide of the channel waveguide array 14, 2a is the core width of the channel waveguide portion, S ₂ is the spacing of the channel waveguide array 14, and d ₂ is the length of the tapered waveguide of the channel waveguide array 14.

Since the core opening width U of the output channel waveguide 13 is designed to be a fraction of the width of the flat light distribution shown in FIG. 9, the optical frequency f of the light source is Even if the value of A is slightly changed, the amount of light coupled to the output channel waveguide 13 is substantially constant. That is, a flat optical frequency characteristic is realized in which the demultiplexing output is substantially constant even if the optical frequency f of the light source changes to some extent.

With respect to the above-mentioned arrayed waveguide grating, a mask was produced using the following parameters. That is, R
= 11.3 mm, W = 35 μm, S ₁ = 25 μm, l ₁
= 250 μm, D = 20 μm, 2a = 7 μm, S ₂ = 2
5 μm, d ₂ = 2 mm, A = 1.0, U = 10 μm, Δ
L = 63 μm.

The arrayed waveguide grating of the present embodiment was produced by using a silica type optical waveguide with the mask thus produced.

First, S is deposited on the Si substrate by the flame deposition method.
An iO ₂ lower clad layer was deposited, and then a core layer of SiO ₂ glass doped with GeO ₂ as a dopant was deposited, followed by transparent vitrification in an electric furnace. Next, the core layer was etched by using the patterns shown in FIGS. 5, 6 and 10 based on the above design to fabricate an optical waveguide portion. Finally, the SiO ₂ upper cladding layer was deposited again.

FIG. 11 shows the measurement result of the optical frequency characteristics of the arrayed waveguide grating thus manufactured. From FIG. 11, it can be seen that the optical frequency characteristic is flattened.

As a result, the 1 dB bandwidth (B _{1.0 dB} ), which was 35 GHz in the conventional arrayed waveguide grating, is expanded to 120 GHz without deteriorating the crosstalk to the adjacent signal channels.

[0026]

As described above, according to the present invention,
Since the core of each waveguide of the input channel waveguide in the vicinity of the boundary with the first fan-shaped slab waveguide has a parabolic shape, a 1 dB bandwidth without deteriorating crosstalk to an adjacent signal channel. The 3 dB bandwidth can be significantly increased, and a flat optical frequency characteristic can be realized. Therefore, even if the wavelength of the light source changes from the central wavelength of each signal channel due to temperature change or the like, the passage loss does not increase, and there is an advantage that the design tolerance of the wavelength division routing system and the like increases.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a conventional arrayed waveguide grating

FIG. 2 is an enlarged view of the vicinity of the first fan-shaped slab waveguide in FIG.

FIG. 3 is an enlarged view of the vicinity of a second fan-shaped slab waveguide in FIG.

FIG. 4 is a diagram showing measurement results of optical frequency characteristics of a conventional arrayed waveguide grating.

FIG. 5 is a configuration diagram showing an example of an embodiment of an arrayed waveguide grating of the present invention.

FIG. 6 is an enlarged view of the vicinity of the first fan-shaped slab waveguide in FIG.

FIG. 7 is an enlarged view of the core of the input channel waveguide in the vicinity of the boundary with the first fan-shaped slab waveguide.

FIG. 8 is a diagram showing an electric field distribution at a boundary between a first fan-shaped slab waveguide and an input channel waveguide.

FIG. 9 is a diagram showing an electric field distribution at a boundary between a second fan-shaped slab waveguide and an output channel waveguide.

10 is an enlarged view of the vicinity of the second fan-shaped slab waveguide in FIG.

FIG. 11 is a diagram showing measurement results of optical frequency characteristics of the arrayed waveguide grating of the present invention.

[Explanation of symbols]

11 ... substrate, 12 ... input channel waveguide, 13 ... output channel waveguide, 14 ... channel waveguide array, 15
... 1st fan-shaped slab waveguide, 16 ... 2nd fan-shaped slab waveguide.

Claims (2)

[Claims] An input channel waveguide disposed on a substrate, an output channel waveguide, a channel waveguide array, and a first sector connecting the input channel waveguide and the channel waveguide array. A second connecting the slab waveguide to the channel waveguide array and the output channel waveguide;
And a fan-shaped slab waveguide, wherein the length of the channel waveguide array sequentially increases with a predetermined waveguide length difference. An arrayed waveguide grating, characterized in that the core of each waveguide of the input channel waveguide near the boundary has a parabolic shape. 2. The parabolic shape is determined by an equation: y = (1 / A) (a ² −x ² ) (where A is a parameter that specifies the parabolic shape, and a is 1/2 of the core width). The arrayed waveguide grating according to claim 1, wherein: