JPS6150293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides multiple inputs using thin film optical waveguides,
This invention relates to a thin film optical switch circuit with multiple outputs.

Conventionally, in multi-input, multi-output thin film optical switch circuits using optical waveguides, light deflection using the electro-optic effect or acousto-optic effect is used for the 1-input, 2-output or 2-input, 2-output optical switch elements that are the constituent elements. ing. However, in these optical switch elements, the deflection angle is as small as 2° or less. Therefore, if you try to combine these elements to construct an optical switch circuit with multiple inputs and multiple outputs, the deflection angle is small, so you will need an extremely long waveguide film, which will increase the size and cause propagation loss to become non-negligible. There was a drawback.

In order to solve these drawbacks, the present invention uses an optical switch element that can obtain a larger deflection angle than conventional ones by changing the equivalent refractive index of the optical waveguide, and uses this element as a component for multiple inputs and multiple outputs. A thin film optical switch circuit is provided. The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a perspective view of a two-input, two-output optical switch element that is a component of the thin film optical switch circuit of the present invention. FIG. 2 is a sectional view of the optical switch element.
This optical switch element is similar to that described in Japanese Patent Application No. 55-003474 "Thin Film Type Optical Deflection Element", and its structure and operation will be briefly explained.

An optical waveguide film 2 is laminated on a substrate 1 to a predetermined thickness. As shown in FIG. 1, for the following explanation, x and y orthogonal coordinate axes and a z axis perpendicular to these are taken within the plane of the optical waveguide film 2. A linear low refractive index region 2' is formed in the x-axis direction of the optical waveguide film 2, and an intermediate layer 3 is formed thereon.
A movable dielectric piece 4 having a bottom parallel to the xy plane is provided via an air layer (which is shown as an air layer in FIGS. 1 and 2). In order to move the movable dielectric piece up and down in the z-axis direction, a dielectric piece drive unit 5 (for example, a piezoelectric bimorph) is mechanically connected to the movable dielectric piece 4, and a dielectric piece drive unit 5 is electrically connected to the dielectric piece drive unit 5. A drive circuit 6 is provided. The refractive indices of the substrate 1, optical waveguide film 2, low refractive index region 2', intermediate layer 3, and movable dielectric piece 4 are respectively n ₁ , n ₂ , n ₂ ', n ₃ , and n ₄ , and n ₂ > n ₂ ′＞n ₄ ＞
The relationship (n ₁ , n ₃ ) should be satisfied. As shown in FIG. 1, when the guided waves 7 and 7' are incident on the low refractive index region 2' in the optical waveguide film 2, they are totally reflected or transmitted in the low refractive index region 2' depending on the incident angle θ. do. Here, the refractive index distribution of the low refractive index region 2' may be either a step type or a graded type.
The figure shows a case of a graded type (graded type in the y-axis direction), where light deflection occurs at the center of the low refractive index region 2'. In this case, the refractive index n ₂ ' is the value at the center of the low refractive index region 2' in the y-axis direction. Now, consider the relationship between the distance l ₃ between the movable dielectric piece 4 and the optical waveguide film 2 shown in FIG. 2, and the total reflection condition in the low refractive index region 2'. distance l ₃
is larger than the film thickness of the optical waveguide film 2.
and the equivalent refractive index at the center of the low refractive index region 2' is ν
₀ and ν ₀ '. Further, when l ₃ is sufficiently smaller than the film thickness of the optical waveguide film 2, the equivalent refractive indexes at the center of the optical waveguide film 2 and the low refractive index region 2' are assumed to be ν and ν'. The equivalent refractive indices ν ₀ , ν ₀ ', ν, ν' are determined by the characteristic equations described in the above-mentioned Japanese Patent Application No. 55-003474.
According to this characteristic equation, there is a relationship between ν ₀ , ν ₀ ', ν, and ν' such that ν'/ν>ν ₀ '/ν ₀ . Therefore, the incident angle θ of the guided light beams 7 and 7' into the low refractive index region 2' is set so as to satisfy ν'/ν>cosθ>ν ₀ '/ν ₀ (1). In this way, when l ₃ is large as described above, that is, when the movable dielectric piece 4 is moved away from the optical waveguide film 2, the total reflection condition is satisfied and the incident guided wave light 7 is totally reflected. The output guided wave 8 becomes the output guided wave 8, and the incident guided wave 7' is also totally reflected to become the output guided wave 8'.

On the other hand, when l ₃ is sufficiently small as described above, that is, when the movable dielectric piece 4 is brought close to the optical waveguide film 2, the total internal reflection condition is no longer satisfied, and the incident guided light 7 passes through the low refractive index region 2. The incident guided light 7' also passes through and becomes the output guided light 8.

In this case, the branching angle of the output guided beams 8 and 8' is given by 2θ, as is clear from FIG.
The branching angle 2θ is between the optical waveguide film 2 and the low refractive index region 2'.
If the relative refractive index difference n ₂ - n ₂ '/n ₂ is 2%, an angle of 20° or more can be obtained, and this degree of relative refractive index difference was
54-161350 "Method for manufacturing thin-film optical devices" and JP-A-53-71845 "Optical waveguide thin film and method for manufacturing the same". To actually drive such a switch element, a drive signal is sent from the drive circuit 6 to the dielectric drive section 5 to move the movable dielectric piece 4 up and down.

The optical switch element as described above performs a switch operation as shown in FIG. When the switch is turned on (the movable dielectric piece 4 is brought close to the optical waveguide film 2 and the low refractive index region 2'), as shown in FIG.
As shown in the figure, the input terminal and the output terminal 〓〓 are connected, and the input terminal and the output terminal 〓〓 are connected. On the other hand, when the movable dielectric piece 4 is placed in the off state (the movable dielectric piece 4 is moved away from the optical waveguide film 2 and the low refractive index region 2'), the input terminal and the output terminal 〓〓 are connected as shown in Fig. 3b. , the input terminal is connected to the output terminal 〓〓. Such a switch 9 is a 2×2 switch of the relocation block type. A relocation type refers to one in which input terminals and output terminals are always connected one to one, and a block type refers to one in which the connection of one input terminal and output terminal affects the connection of other input terminals. say something

If the relocation block type 2x2 switch 9 is the basic unit, the relocation block type NxN switch is N
It is known that it can be configured with (N-1)/2 2×2 switches 9. The structure may be a diamond structure as shown in FIG. 4 or a triangular structure as shown in FIG. Both examples are examples of 7x7 switches.

The N×N switch shown in FIGS. 4 and 5 is
If the 2×2 optical switch element shown in Fig. 1 is used,
Can be configured. FIG. 6 shows the structure of the diamond-structured N.times.N optical switch shown in FIG. 4. For convenience of explanation, xy orthogonal coordinate axes are used as shown in the figure.

There are (N+1) linear low refractive index regions 2' in the optical waveguide film 2, and the center line of each low refractive index region 2' is y=-nd (n=0, 1, ..., N). and the left end is within the third quadrant of the xy coordinate axes. Here, d is the distance between the centers of adjacent low refractive index regions 2' as shown in FIG.

In addition, a terminal located on an arbitrary low refractive index region 2',
The distance in the x-axis direction between this low refractive index region 2' and a terminal located on the adjacent low refractive index region 2' and at the shortest distance from the terminal is l, and the right end portion is
The x-coordinates of (N+1) low refractive index regions 2' are l=
As d/tanθ (θ satisfies equation (1)), (N-
1) It is sufficient if it is sufficiently larger than l.

On these low refractive index regions 2', coordinates [2(n ₁ -1)l, 2(n ₂ -1) with x and y as coordinate axes]
d], where N is an odd number, n ₁ = 1, 2, ...,
(N+1)/2, n ₂ = 1, 2, ..., (N-1)/
2. When N is an even number, n ₁ = 1, 2, ..., N/2,
n ₂ = 1, 2, ..., N/2, and coordinates with x and y as coordinate axes [2(n ₁ -1)l, 2n ₂ d], where when N is an odd number, n ₁ = 1, 2,..., (N-1)/
2, n ₂ = 1, 2, ..., (N-1)/2, when N is an even number, n ₁ = 1, 2, ..., N/2, n ₂ = 1,
2,..., the total N(N-
1) A movable dielectric piece 4 having a sufficiently large bottom surface to cover both the low refractive index region 2' and the optical waveguide film 2 is installed at the intermediate layer 3 at the /2 position. If such a configuration is adopted, in the case of Fig. 6, for the guided light incident on the input terminal ~, 〓〓
A 7×7 rearranged block type thin film optical switch circuit is formed with ~〓〓 as an output terminal. Here, the input/output terminal numbers are numbered in order from the one closest to the x-axis, as shown in FIG. 6. In Figure 6, −〓〓, −〓〓, −〓
Connection examples of 〓, −〓〓, −〓〓, −〓〓, and −〓〓 are shown. In the figure, a single circle represents an on state, and a double circle represents an off state. A connection is a given connection pair −〓〓 (here, ,...,,〓
〓 is 〓〓, 〓〓, ...'. ) in |a-
It is sufficient to perform the steps in order starting from the one with the largest a′|. This is because the selection of the optical path becomes more limited as |a−a′| becomes larger.

Figure 7 shows the N of the triangle structure shown in Figure 5.
The configuration of a ×N rearrangement block type thin film optical switch is shown. N linear low refractive index regions 2' are formed in the optical waveguide film 2 so that the center line of each low refractive index region 2' is y=
nd (n=0, . . . , N-1). In addition, the x-coordinate of the right-hand end is larger than (n-1)l, and the x-coordinate of the left-hand end is smaller than -(n-1)l. On these low refractive index regions 2', coordinates with x and y as coordinate axes [(n ₁ -1) l-2 l (n ₂ -1) (n ₁ -1)
d], where n ₁ = 1, 2, ..., N-1, n ₂ =
1, 2, ..., N(N-1)/2 represented by n ₁
The low refractive index region 2' and the optical waveguide film 2 are located at
A movable dielectric piece having a sufficiently large bottom surface to cover both is installed via the intermediate layer 3. Even with this configuration, a 7.times.7 rearranged block type thin film optical switch circuit is formed in which the input terminals shown in FIG. 7 are connected to the output terminals . Here, the input/output terminal numbers are as shown in Figure 7, in order from the one farthest from the x-axis.
Add 〓〓,... In Figure 7, as in Figure 6, −〓〓, −〓〓, −〓〓, −〓〓, −
A connection example of 〓〓, −〓〓, and −〓〓 is shown. The connections may be made in order from the input terminal with the largest terminal number, or in order from the largest output terminal number. This is because the selection of optical paths is more limited as the combination of connections with larger input terminal numbers or the combination of connections with larger output terminal numbers.

Although a 7.times.7 example is shown in FIGS. 6 and 7, an N.times.N relocation block type switch can generally be formed by the construction method described above. These thin-film optical switch circuits can be easily manufactured according to JP-A-53-71845 ``Optical waveguide film and its manufacturing method'' and JP-A-54-161350 ``Method for manufacturing thin-film optical devices''. .

As explained above, the thin film optical switch circuit of the present invention has a structure in which a movable dielectric piece is installed above N parallel low refractive index regions that can be easily fabricated in an optical waveguide film. It is simple and easy to manufacture, and N×N switch circuits can be manufactured on the same substrate. Also, since the deflection angle of the basic switch elements of the circuit is large, the density of the switch arrangement can be increased. Therefore, if the thin film optical switch circuit of the present invention is applied to the fields of optical communications and optical information processing, it will be extremely effective in reducing manufacturing costs and downsizing devices.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a 2x2 optical switch element, Figure 2
The figure is a cross-sectional view of a 2x2 optical switch element, and Figure 3 is a cross-sectional view of a 2x2 optical switch element.
4 and 5 are diagrams showing the configuration of an N×N switch, and FIGS. 6 and 7 are diagrams showing the configuration of an N×N thin-film optical switch. . DESCRIPTION OF SYMBOLS 1... Substrate, 2... Optical waveguide film, 2'... Low refractive index region, 3... Intermediate layer, 4... Movable dielectric piece, 5
...Movable dielectric piece drive unit, 6...Drive circuit, 7...
...Incoming waveguide light, 8...Output waveguide light, 8'...Output waveguide light, 9...2x2 switch.

Claims (1)

[Claims] 1. An optical waveguide film having a refractive index n ₂ is laminated to a predetermined thickness on a smooth substrate that is transparent to guided light and has a refractive index n ₁ , and xy When the orthogonal coordinate axes are taken, (N+1) linear low refractive index regions 2' having a refractive index n ₂ ' are provided in the optical waveguide film, where N is a positive integer, and d is the adjacent low refractive index region 2'. Let the distance between the centers of the refractive index regions 2' be y=-nd(n=
0, 1, . Assuming that the total reflection angle for x between certain terminals
The distance in the axial direction is l, l = d/tanθ, and the x-coordinate of the right end of the (N+1) low refractive index regions 2' is set to be larger than (N-1)l.
Coordinates [ ₂ ( _{n 1} -1)l,
(2n ₂ -1)d], where N is an odd number, n ₁ = 1,
2,..., (N+1)/2, n ₂ = 1, 2,...,
(N-1)/2, when N is an even number, n ₁ = 1, 2,...
..., N/2, n ₂ = 1, 2, ..., N/2 and coordinates with x, y as the coordinate axes [(2n ₁ -1)l,
2n ₂ d], where N is an odd number, n ₁ = 1, 2,...
..., (N-1)/2, n ₂ = 1, 2, ..., (N-
1)/2, when N is an even number, n ₁ = 1, 2,...
At each of a total of N(N-1)/2 positions represented by N/2, n ₂ = 1, 2, ..., N/2-1, a refractive index is applied via an intermediate layer with a refractive index of n ₃ . n ₄ and parallel to the waveguide film, the low refractive index region 2'
and a movable dielectric piece having a sufficiently wide bottom surface to cover the surrounding optical waveguide film is installed, and the distance _l3 between this movable dielectric piece and the optical waveguide film is greater than the film thickness of the optical waveguide film. Let ν ₀ and ν ₀ ' be the equivalent refractive index at the center of the optical waveguide film and the low refractive index region 2', and the optical waveguide film and the low refractive index when the distance l ₃ is sufficiently smaller than the film thickness of the optical waveguide film and the low refractive index region 2'. Let the equivalent refractive index at the center of the refractive index region 2' be ν and ν',
Satisfying the relationship ν′／ν＞cosθ＞ν ₀ ′／ν ₀ ,
Between the refractive index n ₁ , n ₂ , n ₂ ′, n ₃ , n ₄ , n ₂ >n ₂ ′>
A thin film optical switch circuit characterized in that the following relationship is satisfied: n ₄ >(n ₁ , n ₃ ). 2. When an optical waveguide film having a refractive index n ₂ is laminated to a predetermined thickness on a smooth substrate that is transparent to guided light and has a refractive index n ₁ , and xy orthogonal coordinate axes are set in the optical waveguide film. , N linear low refractive index regions 2' having a refractive index n ₂ ' are provided in the optical waveguide film, where N is a positive integer, and d is the number of adjacent low refractive index regions 2'. The distance between the centers is y=nd (n=0,
1, . The distance in the x-axis direction between the terminal and a terminal located on the low refractive index region 2' adjacent to this low refractive index region 2' and located at the shortest distance from the terminal is l.
and l=d/tanθ, the x-coordinate of the right end of the N low refractive index regions 2' is larger than (n-1)l, and the x-coordinate of the left end is -(n-1)l The coordinates [(n ₁ −
1) l-2 l(n ₂ -1), (n-1) d], where n ₁ = 1, 2, ..., N-1, n ₂ = 1, 2, ...
..., at N(N-1)/2 positions represented by n ₁ , have a refractive index n ₄ through an intermediate layer with a refractive index n ₃ , and are parallel to the optical waveguide film and have the low refractive index. A movable dielectric piece having a sufficiently wide bottom surface to cover the index area 2' and the optical waveguide film around it is installed, and the distance l ₃ between this movable dielectric piece and the optical waveguide film is equal to the distance of the optical waveguide film. The equivalent refractive index at the center of the optical waveguide film and the low refractive index region 2' when it is larger than the film thickness is ν ₀
and ν ₀ ′, and when the distance l ₃ is sufficiently smaller than the film thickness of the optical waveguide film, the equivalent refractive index at the center of the optical waveguide film and the low refractive index region 2′ is ν and ν′, and ν′/ The relationship ν＞cosθ＞ν ₀ ′/ν ₀ is satisfied, and furthermore, between the refractive indices n ₁₁ , n ₂ , n ₂ ′, n ₃ , n ₄
A thin film optical switch circuit characterized in that the following relationship is satisfied: n ₂ > n ₂ ′ > n ₄ > (n ₁ , n ₃ ).