JPH10142435A - Optical waveguide type optical element and production of optical waveguide type optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical waveguide type optical element which is capable of averting coupling loss and allows the miniaturization of optical integrated circuits, etc., by forming fringes of refractive index changes in a core in prescribed blocks nearly uniformly along the longitudinal direction of the core. SOLUTION: The optical element 1 is constituted by changing the refractive index in the core 3 of a plane waveguide 2 which is an optical waveguide like the fringes. The fringes of the refractive index changes are formed nearly uniformly along the longitudinal direction of the core 3. The optical element 1 has plural highrefractive index surfaces 11 according to the periods of these fringes. The plane waveguide 2 is provided with the core 3 which constitutes the waveguide route of light above, for example, a quartz substrate 4. A clad 5 is formed around the core 3. The core 3 is formed of a material which is increased in its refractive index by irradiation with UV light. When, for example, a clad 4 is formed of quartz, the core 3 is formed as a solid soln. formed by adding germanium oxide to the quartz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide type optical element, such as an optical modulator, an optical deflector, an optical frequency shifter, an optical filter, and a polarizer, for changing the state of propagating light, and an optical waveguide type optical element. And a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a polarizing beam splitter, a polarizing prism, and the like are known as polarizers for converting propagating light into polarized light. In recent years, a stacked polarizer in which a large number of metal layers and dielectric layers are alternately stacked has been developed. As shown in FIG. 8, the laminated polarizer A is formed by laminating a large number of metal layers B and dielectric layers C in parallel, and by making light D incident along those layers,
Light having an electric field component parallel to those layers B and C (FIG. 7)
In this case, only the TE wave is to be removed from the light D.

[0003]

However, the above-described polarizing beam splitter and the laminated polarizer have the following problems. First of all, since each of the above-mentioned polarizers is disposed as a component in a light propagation path, a certain degree of coupling loss always exists when light is incident on the polarizer. Since the coupling loss contributes to the transmission loss of the polarized light, the transmission efficiency decreases due to the polarization. Second, when the light guided by the optical integrated circuit is polarized, it is necessary to attach the polarizer to the optical integrated circuit. For this reason,
The circuit becomes a hybrid type, and the whole circuit becomes large.

The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide an optical waveguide type optical element and an optical waveguide type element capable of avoiding coupling loss and miniaturizing an optical integrated circuit or the like. An object of the present invention is to provide a method for manufacturing an optical element.

[0005]

That is, according to the present invention, a stripe of a change in refractive index is formed in a core, and the stripe of a change in refractive index is formed substantially uniformly in a predetermined section along the longitudinal direction of the core. This is an optical waveguide type optical element.

According to such an invention, since it can be provided directly in the core, there is no influence of coupling loss. Further, it can be used as one element of an optical integrated circuit.

Further, according to the present invention, the core is irradiated with ultraviolet light, the ultraviolet light is reflected toward the core by a reflector provided on the side opposite to the ultraviolet light irradiation side, and the ultraviolet light and the ultraviolet light are reflected. And forming a stripe of change in refractive index in the core by causing interference with the reflected light of the optical waveguide.

According to the invention, it is possible to provide the optical waveguide with a diffraction function and a polarization function only by irradiating the optical waveguide with ultraviolet light.

Further, according to the present invention, a core provided above a substrate is irradiated with ultraviolet light from above the core, and the substrate reflects the ultraviolet light toward the core, so that the ultraviolet light and the reflected light of the ultraviolet light are reflected. Forming a stripe of a change in refractive index in the core by causing interference with the optical waveguide type optical element.

[0010] According to such an invention, the substrate of the planar waveguide can be effectively used as a reflection surface for ultraviolet light, and no separate reflection means is required.

Further, the present invention is a method for manufacturing an optical waveguide type optical element, wherein the surface of a substrate is subjected to a high reflection treatment.

According to the invention, since the reflectance of light on the surface of the substrate is increased, a refractive index change region having a sharp refractive index change is formed. .

Further, according to the present invention, a plurality of ultraviolet rays are irradiated toward the core, and the ultraviolet rays interfere with each other in the core to form interference fringes parallel to the optical waveguide direction in the core. A method of manufacturing an optical waveguide type optical element, comprising forming a stripe of a change in refractive index in a core according to the stripe.

According to such an invention, it is possible to impart the diffraction function and the polarization function to the optical waveguide only by irradiating the optical waveguide with ultraviolet light.

Further, the present invention is a method for manufacturing an optical waveguide type optical element, characterized by irradiating ultraviolet light toward a core and moving an ultraviolet light irradiation position along a longitudinal direction of the core.

According to the invention, it is possible to form a stripe of a change in the refractive index having a desired length in the core.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments according to the present invention will be described below with reference to the accompanying drawings. In each of the drawings, the same elements are denoted by the same reference numerals, and description thereof is omitted.
Also, the dimensional ratios in the drawings do not always match those described.

(Embodiment 1) FIG. 1 is a schematic view of an optical waveguide type optical element. In FIG. 1, an optical element 1 is configured by changing the refractive index in a core 3 of a planar waveguide 2 which is an optical waveguide into a stripe shape, and the stripe of the change in the refractive index is substantially along the longitudinal direction of the core 3. It is formed uniformly. That is, the optical element 1 is a stripe of refractive index change formed parallel to and mutually parallel to the optical waveguide direction of the core 3 and a plurality of high refractive index surfaces 11 according to the period of the stripe. Have.

The planar waveguide 2 on which the optical element 1 is formed is
For example, a core 3 serving as a light guide path is provided above a substrate 4 made of quartz or silicon, and a clad 5 is formed around the core 3. Core 3 is
The region has a high refractive index with respect to the cladding 5 for guiding light, and is formed of a material whose refractive index increases by irradiation with ultraviolet light. For example, if the cladding 4 is made of quartz (Si
When the core 3 is formed of O2), the core 3 is a solid solution obtained by adding germanium oxide (GeO2) to quartz, and has a high refractive index region with respect to the clad. The added germanium oxide reacts with ultraviolet light. The refractive index increases. Note that the additive (dopant) in the core 3 is not limited to germanium oxide, but may be any material that has a higher refractive index than the clad 5 and raises the refractive index of the core 3 by irradiation with ultraviolet light. For example, other additives such as phosphorus (P), boron (B), and tin (Sn) may be used. Further, those additives may be mixed and added.

In FIG. 1, a high refractive index surface 1 of an optical element 1 is shown.
Reference numeral 1 denotes an equi-refractive index surface having a high refractive index in the core 3, and the light propagating through the core 3 is formed by forming a plurality of such high refractive index surfaces 11 along the optical waveguide direction of the core 3. Can be changed. For example, it is possible to diffract propagating light and divide it into a plurality of lights, or to remove only TM waves (light that does not include a magnetic field component in the light guiding direction) among propagating lights. The refractive index modulation degree and the formation interval of the high refractive index surface 11 may be appropriately set in consideration of the use of the optical element 1 and the wavelength of light propagating through the core 3.

Next, the diffraction function of the optical element 1 will be described.

When light 6 (propagating light) propagates along the core 3 and the light 6 enters the optical element 1, a part of the light 6 is diffracted into diffracted light, and a plurality of lights are emitted from the optical element 1. Will be done. That is, assuming that the formation length of the optical element 1 in the optical waveguide direction is L and the formation interval between the high refractive index surfaces 11 is D, as shown in FIG. Light 6 is converted into black diffraction light 6
Produces only a specific diffracted light. On the other hand, when the formation length L is sufficiently small relative to the interval D, Raman-Nass diffraction occurs as shown in FIG. Can be injected. By making the optical element 1 function as described above, the optical element 1 can be used as an optical deflector, an optical frequency shifter, an optical filter, an optical modulator, and the like.

When black diffraction is caused in the propagating light 6, the formation interval D in the optical element 1 needs to be a dimension suitable for the wavelength of the light 6. It is important to form the optical element 1 with D being an accurate dimension. According to the optical element 1, since the high refractive index surfaces 11 can be formed at precise intervals as described later, the diffraction function can be reliably exhibited.

The optical element 1 is a core 3 of the planar waveguide 2.
Is provided directly on the core 3, which is a normal core 3 which is a waveguide.
No boundary surface exists between the area of the optical element 1 and the optical element 1, and there is no coupling loss between the area of the waveguide and the optical element 1. Accordingly, light can be diffracted and deflected without loss. Furthermore, since it can be provided directly inside the core 3 of the planar waveguide 2, there is no need to separately package the chip of the optical integrated circuit, and it can be used as one component of the optical integrated circuit.

Next, the polarization function of the optical element 1 will be described.

In FIG. 3, the TE wave 61 along the core 3
When light including the TM wave 62 is propagating, when this light is incident on the optical element 1, TM having an electric field component in a direction intersecting with the high refractive index surface 11 in the light.
Waves 62 are emitted from core 3 and are removed from light propagating through core 3. That is, in the TM wave 62 of the propagating light, the formation region of the optical element 1 is effectively a region having a low refractive index, and as shown in FIG.
Is largely refracted with respect to the axis of. Therefore, the light is transmitted without being reflected at the boundary between the core 3 and the clad 5, and is emitted to the outside of the planar waveguide 2 through the clad 5.

On the other hand, in the TE wave 61 having only an electric field component parallel to the high refractive index surface 11 among the light propagating through the core 3, the formation of the optical element 1 is different from the TM wave 62 described above. Is hardly affected, so that the light passes through the optical element 1 and continues to propagate along the core 3.

As described above, according to the optical element 1, of the light propagating in the core 3, only the TM wave 62 is emitted to the outside of the core 3, and the light propagating in the core 3 is polarized only by the TE wave 61. be able to.

Further, the optical element 1 is a core 3 of the planar waveguide 2.
Is provided directly on the core 3, which is a normal core 3 which is a waveguide.
No boundary surface exists between the area of the optical element 1 and the optical element 1, and there is no coupling loss between the area of the waveguide and the optical element 1. Therefore, polarized light can be obtained without losing light.
Furthermore, since it can be provided directly inside the core 3 of the planar waveguide 2, there is no need to separately package the chip of the optical integrated circuit, and it can be used as one component of the optical integrated circuit.

Next, a method for manufacturing the optical element 1 will be described.

In FIG. 4, first, ultraviolet light 7 is irradiated to the core 3 provided inside the planar waveguide 2. As the ultraviolet light 7 to be irradiated, one having coherence is used, for example, an ultraviolet light having a wavelength of 244 nm emitted by an excimer laser is used.

The ultraviolet light 7 entering the planar waveguide 2 passes through the cladding 5 and enters the core 3, passes through the core 3,
It reaches the substrate 4 through the clad 5. Then, the ultraviolet light 7 is reflected on the surface of the substrate 4 and returns inside the core 3 again. At this time, the ultraviolet lights 7, 7 reciprocating in the core 3 interfere with each other to generate a number of interference fringes parallel to the surface of the substrate 4, that is, parallel to the light guide direction of the core 3. In a region of the interference fringe where the energy intensity of the ultraviolet light is large (a region of a bright portion of the brightness of the interference fringe), a light-induced refractive index change caused by a Ge-related oxygen-deficient defect occurs in a stripe shape. It will be. As a result, a number of high refractive index surfaces 11 are formed inside the core 3, and the manufacture of the optical element 1 is completed.

Assuming that the wavelength of the ultraviolet light 7 is λ, the interference fringe is λ
/ 2, so that the high refractive index surfaces 11 are formed at an interval of λ / 2. For example, when ultraviolet light 7 having a wavelength of 224 nm is used, 1
The high refractive index surfaces 11 are formed at a pitch of 12 nm. When it is desired to change the interval of forming the high refractive index surface 11, the irradiation may be performed using the ultraviolet light 7 having a wavelength corresponding to the interval.

In this manufacturing method, a reflecting surface of the ultraviolet light 7 is required. However, by effectively utilizing the surface of the substrate 4 of the planar waveguide 2 as a reflecting surface, a separate reflecting surface is provided in the planar waveguide 2. It is not necessary to provide the device, and the manufacturing operation can be performed efficiently. It is important that the irradiation direction of the ultraviolet light 7 is perpendicular to the surface of the substrate 4 serving as a reflection surface in order to surely cause interference inside the core 3.

As described above, the optical element 1 according to the present embodiment
According to the manufacturing method described above, the optical element 1 can be easily formed inside the core 3 simply by irradiating the planar waveguide 2 with the ultraviolet light 7.

(Embodiment 2) In the above-described method for manufacturing the optical element 1, the surface of the substrate 4 which is to be a reflection surface of the ultraviolet light 7 may be subjected to high reflection processing. That is, in the method for manufacturing the optical element 1 according to the present embodiment, before the irradiation with the ultraviolet light 7,
The surface of the substrate 4 is subjected to high reflection processing in advance. For example, before forming the core 3 on the substrate 4 at the time of manufacturing the planar waveguide 2, metal deposition is performed on the surface of the substrate 4 to make the surface of the substrate 4 a highly reflective surface. Then, the core 3 and the clad 5 are sequentially formed to form the planar waveguide 2. Note that gold or the like may be used as the metal for metal evaporation.

By irradiating such a planar waveguide 2 with ultraviolet light 7 as described above, and reflecting the ultraviolet light 7 on a metal-deposited surface provided on the substrate 4 and having a high reflectance,
The contrast of the interference fringes of the ultraviolet light 7 becomes clear. For this reason, the refractive index of the high refractive index surface 11 changes sharply, and the optical element 1 excellent in polarization performance and the like can be obtained.

The method of the high reflection treatment of the surface of the substrate 4 is not limited to the method of performing metal deposition, but any other method can be used as long as the surface of the substrate 4 can be made a surface having a high reflectance to the ultraviolet light 7. May be used.

(Embodiment 3) In the method of manufacturing the optical element 1 according to Embodiment 1 or 2 described above, the substrate 4 constituting the planar waveguide 2 is used as the means for reflecting the ultraviolet light 7. The reflecting means may be arranged outside the planar waveguide 2 to reflect the ultraviolet light 7.

For example, the substrate 4 of the planar waveguide 2 is
After the light reflector is provided below the planar waveguide 2, the ultraviolet light 7 is irradiated from above (as shown in FIG. 4). Then, ultraviolet light 7 is applied to clad 5,
The light passes through the core 3, the clad 5, and the substrate 4 sequentially, propagates, is reflected by the light reflector below the planar waveguide 2, and returns to the core 3 through the substrate 4 and the clad 5. At this time, since the ultraviolet light 7 interferes in the core 3, a stripe of a change in the refractive index, for example, a high refractive index surface 11 is formed in the interference fringe portion, and the optical element 1 similar to that described above can be formed.

(Embodiment 4) In Embodiments 1 to 3 described above, the ultraviolet light 7 emitted in the same direction is used, but the optical element 1 is formed by using a plurality of ultraviolet lights 7. Is also good. That is, in the method of manufacturing the optical element 1 according to the present embodiment, a plurality of ultraviolet lights 7 are irradiated toward the core 3 from different directions, and the ultraviolet lights 7 interfere within the core 3 so as to be parallel to the optical waveguide direction. Core 3
Within the pattern, stripes of a change in the refractive index are formed. For example, as shown in FIG. 5, two ultraviolet lights 7, 7 having different directions are projected toward the core 3, and the ultraviolet lights 7, 7 interfere with each other in the core 3, and the optical waveguide direction of the core 3 And an interference fringe parallel to. Then, the refractive index in the core 3 increases according to the fringe interval of the interference fringes of the ultraviolet light 7, 7, forming a stripe pattern of a change in the refractive index, and forming a large number of high refractive index surfaces 11. Similarly, the optical element 1 can be manufactured.

(Embodiment 5) In Embodiments 1 to 4 described above, the optical element 1 is formed by appropriately irradiating the ultraviolet light 7 to a predetermined position of the core 3. May be moved along the optical waveguide direction (longitudinal direction) of the core 3 to form the optical element 1. For example, as shown in FIG. 6, the core 3 is irradiated with a plurality of ultraviolet light beams 7a, and the irradiation position is moved in the optical waveguide direction of the core 3.
The irradiation position is moved with respect to the planar waveguide 2 with respect to the ultraviolet light beam 7.
The light source a may be moved, or the planar waveguide 2 may be moved with respect to the light source of the ultraviolet light beam 7a. UV light beam 7a
It is important to use a material whose light intensity is large enough to change the refractive index of the core 3 by irradiation. By the irradiation of the ultraviolet light 7a and the movement of the irradiation position, the optical element 1 continuous in the longitudinal direction of the core 3 can be formed according to the moving distance of the light source or the planar waveguide 2. According to such a manufacturing method, the optical element 1 having a desired formation length can be easily manufactured, and the optical element 1 having a long formation length can be manufactured.

Further, such a manufacturing method is described in the first embodiment.
4 can also be directly applied. For example, in the case where the optical element 1 is formed by irradiating the ultraviolet light 7 toward the core 3 of the planar waveguide 2 and causing interference in the core 3,
The irradiation position of the ultraviolet light 7 is set in the optical waveguide direction of the core 3 (longitudinal direction).
By irradiating the ultraviolet light 7 while moving the optical element 1, the optical element 1 having a desired formation length can be easily manufactured,
It is also possible to manufacture the optical element 1 having a large formation length.

(Embodiment 6) In the manufacturing method of the optical element 1 of the above-described Embodiments 1 to 5, the core 3 of the planar waveguide 2
Although the optical element 1 is formed, the object to be manufactured is not limited to the planar waveguide 2 but may be an optical fiber. For example, as shown in FIG. 7, by projecting two ultraviolet lights 7 and 7 toward the core 3 of the optical fiber 2 a and causing interference inside the core 3, the same optical element 1 as described above is manufactured on the core 3. be able to.

[0045]

As described above, according to the present invention,
The following effects can be obtained. That is, since it can be provided directly in the core, there is no influence of the coupling loss. In addition, by directly providing the optical integrated circuit chip, it can be used as a component of the optical integrated circuit,
The size of the optical integrated circuit can be reduced.

Further, an optical element having a diffraction function and a polarization function inside the optical waveguide can be easily manufactured only by irradiating the optical waveguide with ultraviolet light.

Further, if the substrate of the planar waveguide is used as a reflecting surface for ultraviolet light, it is not necessary to provide a separate reflecting means, and the optical element can be manufactured efficiently.

Further, if the surface of the substrate is subjected to high reflection treatment before irradiation with ultraviolet light, the reflectance of light on the surface of the substrate can be increased, and an optical element having high polarization performance or high deflection function can be manufactured. it can.

Further, by moving the irradiation position of the ultraviolet light beam along the optical waveguide direction of the core, an optical element having a desired formation length can be easily manufactured. Manufacturing is also possible.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an optical element.

FIG. 2 is an explanatory diagram of a diffraction function of an optical element.

FIG. 3 is an explanatory diagram of a polarization function of an optical element.

FIG. 4 is an explanatory diagram of a manufacturing process of the optical element.

FIG. 5 is an explanatory diagram of a method for manufacturing an optical element according to a fourth embodiment.

FIG. 6 is an explanatory diagram of a method for manufacturing an optical element according to a fifth embodiment.

FIG. 7 is an explanatory diagram of a method for manufacturing an optical element according to a sixth embodiment.

FIG. 8 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical element, 11 ... High refractive index surface, 2 ... Planar waveguide, 3
... Core, 4 ... Substrate, 5 ... Clad, 6 ... Light (propagating light),
7 ... Ultraviolet light

Claims (6)

[Claims] 1. An optical waveguide type optical element wherein a stripe of a change in refractive index is formed in a core, and the stripes of a change in refractive index are formed substantially uniformly in a predetermined section along a longitudinal direction of the core. 2. A core is irradiated with ultraviolet light, and the ultraviolet light is reflected toward the core by a reflector provided on a side opposite to the ultraviolet light irradiation side with respect to the core, and the ultraviolet light and the ultraviolet light are reflected. Performing by forming stripes of refractive index change in the core by interfering with reflected light of light,
The manufacturing method of the optical waveguide type optical element characterized by the above-mentioned. 3. A core provided above a substrate is irradiated with ultraviolet light from above the core, the substrate reflects the ultraviolet light toward the core, and the ultraviolet light and the reflected light of the ultraviolet light. To form a stripe of refractive index change in the core by causing interference with
The method for manufacturing an optical waveguide type optical element according to claim 2, wherein: 4. The method according to claim 3, wherein the surface of the substrate is subjected to high reflection processing. 5. A method of irradiating a plurality of ultraviolet lights toward a core, causing the ultraviolet lights to interfere in the core to form interference fringes parallel to the optical waveguide direction in the core, and forming an interference fringe of the ultraviolet light. Forming a stripe of a change in the refractive index in the core according to the above method. 6. A core is irradiated with a plurality of ultraviolet light beams toward the core, and the irradiation positions of the ultraviolet light beams are moved along the optical waveguide direction of the core so as to be parallel to the optical waveguide direction in the core. A method of manufacturing an optical waveguide type optical element, wherein the method is performed by forming stripes of a change in refractive index.