JPH10160964A - Optical device, optical guide-in device, and optical detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical guide-in device which can guide light in an optical waveguide efficiently. SOLUTION: The optical guide-in device S1 which guides the light in the optical waveguide 1 is provided with an echelette grating G formed on one main surface M2 of the optical waveguide 1l and a projecting element 2 on the main surface M1 on the opposite side from the main surface M2. Then light L11 is emitted by the projecting element 2 so that the echelette grating G is used as a reflection type diffraction grating. At this time, the light L11 is emitted to the echelette grating G so that blaze conditions are met, and diffracted light L13 is obtained with efficiency. Consequently, the light L13 which is propagated in the optical waveguide 1 while totally reflected inside can efficiency be obtained, Further, no prism is used, so compact design become possible and the influence of dirt sticking on the diffraction grating G is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device for converting between light propagating inside an optical waveguide and light propagating outside the optical waveguide.

[0002]

2. Description of the Related Art In the field of transmission of information using light, switching using light, and information processing, it is required as a basic technique to guide light to an optical waveguide or to detect light propagating through the optical waveguide. You.

As a method of introducing light into an optical waveguide, which is one of such basic techniques, a method using a prism or a diffraction grating has been conventionally known. FIG. 7 shows an example thereof. In FIG. 7A, a prism T1 having substantially the same refractive index as that of the optical waveguide 100 is coupled to the surface of the optical waveguide 100 (optical contact or the like). In this example, light emitted from the light projecting means 200 toward the prism T1 is incident on one surface of the prism T1 at an incident angle θp,
The light advances to the inside of the prism T1 at the refraction angle θq. Then, the light further proceeds into the optical waveguide 100, and enters the boundary with the outside at an incident angle θr equal to or larger than the critical angle inside the optical waveguide 100. Thus, the light L102 propagates inside the optical waveguide 100 while being totally reflected.

In FIG. 7B, a transmission type diffraction grating T2 is formed on the surface of the optical waveguide 100, and
0, the light L103 which is vertically incident on the transmission diffraction grating T2
Out of the optical waveguide 100 while totally diffracting the inside of the optical waveguide 100 as shown by light L104.
0 is propagated inside.

[0005]

As described above, as a method of introducing light into an optical waveguide, a method using a prism or a transmission type diffraction grating is known. In the method using a prism, the prism is moved from the optical waveguide. Since the projection largely protrudes to the outside, it is necessary to secure a space for disposing the prism. In addition, the transmission type diffraction grating is easily affected by dirt because it is a surface depending on the form used, and furthermore, since diffracted light is introduced into the optical waveguide,
There is a problem that the introduction efficiency is poor. Note that these are the same problems when light is guided from the inside of the optical waveguide to the outside with the same configuration.

Accordingly, the present invention has been made in view of the above problems, and is compact in size, hardly affected by dirt, and capable of efficiently introducing light into or extracting light from an optical waveguide. The purpose is to provide a device.

[0007]

According to a first aspect of the present invention, there is provided a light for converting between a first light propagating inside an optical waveguide and a second light propagating outside a surface on one side of the optical waveguide. A device, wherein a reflection type diffraction grating for directing a diffraction surface inside the optical waveguide is provided on the other surface of the optical waveguide, and the first diffraction grating is diffracted by the reflection type diffraction grating.
An optical path is changed from one of the light and the second light to the other.

According to a second aspect of the present invention, in the optical device according to the first aspect, the reflection type diffraction grating is an echelette grating.

A third aspect of the present invention is the optical device according to the first or second aspect, wherein the reflection type diffraction grating is a diffraction pattern formed on the other surface of the optical waveguide.

According to a fourth aspect of the present invention, in the optical device according to the third aspect, the other surface of the optical waveguide in the diffraction pattern is covered with a light reflecting layer.

According to a fifth aspect of the present invention, in the optical device according to the first or second aspect, the reflection type diffraction grating is formed on a member different from a member constituting the optical waveguide itself. Another member is coupled to the other surface of the optical waveguide.

A sixth aspect of the present invention is a light introducing device for introducing light from outside the surface on one side of the optical waveguide to the inside of the optical waveguide, wherein the reflection type device directs a diffraction surface to the inside of the optical waveguide. A diffraction grating is provided on the other surface of the optical waveguide, and light incident on the optical waveguide through the one surface is diffracted by the reflection type diffraction grating, so that the inside of the waveguide is Is obtained.

According to a seventh aspect of the present invention, there is provided a photodetecting device for detecting and detecting light propagating in an optical waveguide from one surface of the optical waveguide, wherein a diffractive surface is provided in the optical waveguide. Is provided on the other surface of the optical waveguide, and a light receiving means is optically coupled to the one surface of the optical waveguide, and propagates inside the waveguide. After being diffracted by the reflection type diffraction grating, the reflected light is led out of the optical waveguide through the one surface, and then is received and detected by the light receiving means.

When the waveguide direction in the optical waveguide (transparent plate 1) is a horizontal direction as shown in the drawings relating to the following embodiments, the "upper side" and "lower side" of the optical waveguide correspond to the above-mentioned invention. The "one side" and "the other side" of the optical waveguide in the definition can correspond to each other, but it is obvious from the essence of the present invention that these may be inverted upside down.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

<1. First Embodiment> FIG. 1 is a view showing a light introducing device S1 according to a first embodiment of the present invention. The light introducing device S1 is a device for introducing light into a transparent plate 1, which is an optical waveguide capable of transmitting light while totally reflecting the light therein. It has a light projecting element 2 that emits light toward the surface M1, and a diffraction grating G that is an optical device formed on a part of the main surface M2 which is one surface opposite to the main surface M1. It is assumed that both principal surfaces are substantially parallel.

The refractive index of the space outside the transparent plate 1 is n
0, assuming that the refractive index inside the transparent plate 1 is n1

[0017]

(Equation 1)

The following relationship is satisfied. That is,
The transparent plate 1 is located at the boundary surface with the outside.

[0019]

(Equation 2)

Is a critical angle, and light incident on the boundary surface at an incident angle equal to or greater than the critical angle propagates inside the transparent plate 1 while being totally reflected.

When the light L11 is emitted from the light projecting element 2 and enters the transparent plate 1 through the main surface M1, it becomes light L12 and enters the diffraction grating G at an incident angle α. Diffraction grating G
Is a saw-toothed echelette grating as shown in FIG. 2 so that the diffraction efficiency of diffracted light is maximized for a specific wavelength of incident light and a specific incident angle.
That is, assuming that the angle between the incident light L12 and the diffracted light L13 is K and the wavelength of the light L12 incident on the diffraction grating G is λb (blaze wavelength), the lattice constant is d, and the surface of the grating groove is the main surface direction. Angle θb (blaze angle) is the blaze condition,

[0022]

(Equation 3)

A diffraction grating G is formed so as to satisfy the above.

The light L13 thus obtained is the light L13
12 is incident on the surface of the diffraction grating G at an incident angle α,

[0025]

(Equation 4)

After that, the light enters the boundary surface between the transparent plate 1 and the outside at the angle β, so that in relation to the critical angle θc,

[0027]

(Equation 5)

Is satisfied, the light L13 propagates while totally reflecting inside the transparent plate 1.

As described above, in the first embodiment, an echelette grating is formed as an optical device on the principal surface M2, which is one surface of the transparent plate 1, and the diffraction surface is directed to the inside of the transparent plate 1. Since it is used as a reflection type diffraction grating, the diffracted light L13 can be obtained very efficiently. Thereby, efficient introduction of light into the transparent plate 1 is realized.

The diffraction grating is not limited to an echelette, but may be another diffraction grating. Also in this case, since the diffraction surface of the diffraction grating faces the inside of the transparent plate 1, efficient introduction of light which is hardly affected by dirt attached to the diffraction grating is realized.

Further, since the light introducing device S1 does not use a prism, it is compact, and there is no space problem. Further, since the main surface M2 of the transparent plate 1 itself forms a diffraction pattern by forming a diffraction pattern, an optical device can be directly formed on the transparent plate 1.

<2. 2. Second Preferred Embodiment FIG. 3 is a view showing a photodetector S2 according to a second preferred embodiment of the present invention. In the photodetector S2, as in the first embodiment, the transparent plate 1 having the main surfaces M1 and M2, which are the front and back surfaces, is an optical waveguide. As in the first embodiment, a diffraction grating (echelette grating) G is formed on the main surface M2, and the light receiving element 3 is provided on the main surface M1 side.

The light detecting device S2 detects the light L21 propagating while totally reflecting inside the transparent plate 1, and the diffraction grating G causes a phenomenon completely opposite to that of the first embodiment.

That is, the wavelength λ propagating while being totally reflected at a predetermined incident angle β at the boundary between the transparent plate 1 and the outside.
A diffraction grating G that satisfies the relationship shown in Equation 3 is formed so that the diffraction efficiency of the diffraction grating G with respect to the light b is improved.

Therefore, the light receiving element 3 is arranged on the optical path where the diffracted light L22 is led out of the transparent plate 1 through the main surface M2 and travels as light L23. The light L21 propagating inside the transparent plate 1 can be efficiently detected.

Further, similarly to the first embodiment, a compact photodetector which does not cause a problem in space is realized, and is less affected by dirt attached to the diffraction grating G.

<3. Other Embodiments> FIGS. 4 and 5 show that the light L11 emitted from the light projecting element 2 is
FIG. 6 is a view showing another embodiment of the light introducing device for introducing light into the transparent plate 1 as shown in FIG. In the following description, similar modifications can be made for the photodetector.

FIG. 4 is a diagram showing an example in which the diffraction grating G is provided indirectly on the main surface M2. That is, the member 4 on which the diffraction grating G is formed is connected to the main surface M2. Of course, in this case, it is preferable that the refractive index of the member 4 and the transparent plate 1 be substantially the same and that light transmitted at the boundary with the main surface M2 be not disturbed, but these are appropriately selected according to the application. .

As described above, by forming the diffraction grating G on another member 4 and bonding it to the main surface M2, even if the transparent plate 1 is a thin sheet or a thin coating, for example, It can be used as an optical waveguide.

FIG. 5 shows a diffraction grating G covered with a reflection member (a light reflection layer generally including a reflection film) 5. The reflection member 5 and the diffraction grating G are in an optical contact state up to the inside of the grating groove, so that light incident on the diffraction grating G is reflected at the boundary with the reflection member. Thus, the light incident on the diffraction grating G is efficiently reflected at the grating grooves, and the diffraction efficiency can be further increased. In addition, dirt does not adhere to the diffraction grating G.

The present invention is not limited to the above embodiment, but can be used for various modifications and various applications.

For example, in the above embodiment, the transparent plate 1 is used as the optical waveguide. However, as described above, a thin sheet or a coated thin film may be used. A type of diffraction grating may be formed.

Also, the diffraction grating is not limited to the surface of the optical waveguide as long as it is used as a reflection type, and may be present in a portion near the surface inside the optical waveguide.

In the above embodiment, light having a specific wavelength is described as light, but light having a plurality of wavelengths may be used. In this case, if the diffraction grating is used as an echelette grating, according to the wavelength of the incident light,
The diffraction efficiency can be increased for each light by selecting the incident angle. Also, if the diffraction efficiency is not pursued to the extent that diffraction using an echelette grating is performed, light must be introduced into the optical waveguide even if white light is incident on a normal diffraction grating. Can be.

<4. Application Example to Switch> FIG. 6 is a cross-sectional view showing a switch PS which is an application example of the light introducing device and the light detecting device according to the present invention. The switch PS is shown in FIG.
As shown in (b), the switch is a switch for detecting an input of pressing P, and is arranged so that a first transparent plate 11 serving as a base, a spacer 6, and a second transparent plate 12 having flexibility are overlapped. ing. Further, a diffraction grating G1 is formed on the lower surface of the side end of the first transparent plate 11, and the light projecting element 2 is disposed above the diffraction grating G1, thereby forming a light introducing device S1. Further, a diffraction grating G2 is formed on the lower surface of the side end of the second transparent plate 12, and the light receiving element 3 is disposed above the diffraction grating G2.
The light detection device S2 is configured.

The area between the two spacers 6 is the switch P
The first transparent plate 11 and the second transparent plate 1 are in an area where the pressing P of S is input, and when no pressing P is input.
2 is in a state of being separated as shown in FIG. Therefore, the light L31 emitted from the light projecting element 2 is diffracted by the diffraction grating G1, and the light L31 passes through the inside of the first transparent plate 11 as described in the first embodiment.
It only reaches 32 and propagates.

Here, as shown in FIG. 6B, the first transparent plate 1 is placed in the region between the two spacers 6 from the second transparent plate 12 side.
When the pressure P is input toward 1, the first transparent plate 11 bends and the first and second transparent plates 11 and 12 come into contact with each other at the contact position E. Thereby, a part of the light L32 that has propagated inside the first transparent plate 11 is guided from the contact position E to the inside of the second transparent plate 12, and propagates inside the second transparent plate 12 as shown by light L33. It will go.

When the light L33 propagates through the inside of the second transparent plate 12, the light L33 reaches the diffraction grating G2, and is diffracted there, and enters the light receiving element 3 as shown by the light L34.

When the pressure P is removed, the second transparent plate 12
Due to its own restoring force, it returns to the original state as shown in FIG.

As described above, the light introducing device S1
The switch PS can be formed by introducing light into the first transparent plate 11 using the light detecting device S2 and detecting light guided to the second transparent plate 12 by the pressing P using the photodetector S2. Further, in the switch PS, as described in the first and second embodiments, it is not necessary to consider the arrangement space of the prism and the like. Further, since the light is efficiently introduced and derived, 1 and 2nd transparent plate 1
Even if the sheets 1 and 12 are thin sheets, they can function as switches having excellent operation performance.

[0051]

According to the optical device of the first aspect, the reflection type diffraction grating which directs the diffraction surface to the optical waveguide is formed by the first light propagating inside the optical waveguide and the second light propagating outside the optical waveguide. Since the conversion is performed, light conversion is realized, and the optical device itself is more compact than when a prism is used. In addition, since the reflection type diffraction grating directs the diffraction surface toward the inside of the optical waveguide, it is hardly affected by dirt and efficient light conversion is realized.

In the optical device according to the second aspect, since the reflection type diffraction grating is an echelette grating, more efficient conversion between the first light and the second light can be realized.

In the optical device according to the third aspect, since the diffraction pattern is formed on the surface of the optical waveguide itself, the optical device can be directly formed on the optical waveguide.

In the optical device according to the fourth aspect, since the surface on which the diffraction pattern is formed is covered with the light reflecting layer, more efficient conversion between the first light and the second light becomes possible. At the same time, no dirt adheres to the reflection type diffraction grating.

In the optical device according to the fifth aspect, since the reflection type diffraction grating is coupled as a separate member, the conversion between the first light and the second light is performed even if the optical waveguide has a thin layer shape. be able to.

In the light introducing device according to the sixth aspect, the light from the light projecting means is converted into light propagating inside the optical waveguide by using the above-described optical device, so that efficient light introduction is realized.

In the photodetector according to the seventh aspect, the light propagating inside the optical waveguide is guided to the outside of the optical waveguide by using the above-mentioned optical device, and is detected by the light receiving means. A detection device is realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a light introducing device according to the present invention.

FIG. 2 is a diagram showing an echelette grating.

FIG. 3 is a sectional view showing a photodetector according to the present invention.

FIG. 4 is a sectional view showing another embodiment of the light introducing device.

FIG. 5 is a sectional view showing another embodiment of the light introducing device.

FIG. 6 is a sectional view showing a switch using the light introducing device and the light detecting device according to the present invention.

FIG. 7 is a diagram showing a conventional method for introducing light into an optical waveguide.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transparent plate 2 light emitting element 3 light receiving element 4 member 5 reflecting member L11 to L13, L21 to L23 light G diffraction grating (echelette grating) M1, M2 main surface S1 light introducing device S2 light detecting device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shuko Yokoyama 13-17 Shimizuguchi, Nakano, Honme-cho, Kameoka-shi, Kyoto

Claims (7)

[Claims] 1. An optical device for converting between first light propagating inside an optical waveguide and second light propagating outside a surface on one side of the optical waveguide, wherein a diffractive surface is provided inside the optical waveguide. Is provided on the other surface of the optical waveguide, and by diffraction by the reflection type diffraction grating, one of the first light and the second light is transmitted to the other. An optical device, wherein an optical path is changed. 2. The optical device according to claim 1, wherein said reflection type diffraction grating is an echelette grating. 3. The optical device according to claim 1, wherein the reflection-type diffraction grating is a diffraction pattern formed on the other surface of the optical waveguide. 4. The optical device according to claim 3, wherein the other surface of the optical waveguide in the diffraction pattern is covered with a light reflecting layer. 5. The optical device according to claim 1, wherein the reflection type diffraction grating is formed on a member different from a member forming the optical waveguide itself, and the another member is formed on the optical waveguide. An optical device, wherein the optical device is coupled to the other surface of the optical device. 6. A light introducing device for introducing light from outside a surface on one side of an optical waveguide to the inside of the optical waveguide, wherein a reflection type diffraction grating for directing a diffraction surface to the inside of the optical waveguide is provided. The light incident on the optical waveguide through the one surface is diffracted by the reflection type diffraction grating, so that light propagating inside the waveguide is obtained. A light introducing device characterized by the above-mentioned. 7. A light detection device for detecting light propagating inside an optical waveguide from one surface of the optical waveguide and detecting the light, wherein a reflection type diffraction grating for directing a diffraction surface to the inside of the optical waveguide is provided. The light guide is provided on the other surface of the optical waveguide, and light receiving means is optically coupled to the one surface of the optical waveguide, and the light propagating inside the waveguide is reflected by the reflection type diffraction grating. A light detecting device that is guided out of the optical waveguide through the one surface after being diffracted by the optical waveguide, and then received and detected by the light receiving unit.