JPS5974526A - Optical isolator and its production - Google Patents

Abstract

PURPOSE:To attain an optical isolator which can be coupled with a semiconductor optical waveguide monolithically and is small-sized and has less waveguide loss and has a high coefficient of coupling with a light source or the like, by forming insular magnetooptic materials on an amorphous material and crystallizing them by a laser annealing method to form an optical waveguide. CONSTITUTION:An amorphous material (having a thickness of 0.1-1mum) 9 consisting of an SiO2 is stuck to a substrate 10, and magnetooptic materials (having a thickness of 0.5-2mum) such as YIG, TAG, or the like are formed insularly with a width of 2-10mum, and magnetooptic crystals 6 and 7 are formed by the laser annealing method to form the optical waveguide. An optical waveguide consisting of a GaAs or the like is formed by the moleculer epitaxis method or the like, and a metallic thin film is vapor-deposited to the surface of this optical waveguide to form light absorbers 5 and 8. Thus, the optical isolator which is small-sized and has less optical waveguide loss and has a high coefficient of coupling with the light source or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical isolator used in optical communications and a method for manufacturing the same.

[Prior art]

In recent years, the practical application of optical communications has progressed rapidly, and research and development has been pushed forward to make optical components smaller and more reliable. Magneto-optical effects are now being used as optical isolators, which are components of optical integrated circuits. What has been done is known.

FIG. 1 is a diagram showing a conventional optical isolator.

In the figure, 1 is a polarizing plate, 2 is a magneto-optical material having a magneto-optic effect, 3 is an optically active substance that rotates the plane of polarization of light, and 4 is a polarizing plate.

In this optical isolator, the input light from the left becomes horizontally polarized light by the polarizing plate 1, the plane of polarization is rotated by 45° clockwise by the magneto-optic material 2, and rotated by 45° counterclockwise by the optically active material 3. The light returns to the original horizontally polarized light, passes through the polarizing plate 4, and is taken out as an output. On the other hand, the input light from the right becomes horizontally polarized light by the polarizing plate 4, and the plane of polarization is rotated by 45° clockwise by the optically active material 3, and further rotated by 45° in the same direction by the magneto-optic material 2. The light entering the polarizing plate 1 becomes vertically polarized light and cannot pass through the polarizing plate 1. That is, light from the left is output to the right, but light from the right is not output to the left.

But 1. Since this optical isolator is composed of a collection of single components made of oxide, when applied to optical integrated circuits, it can be monolithically combined with a ■-V compound semiconductor laser or ■-■ compound semiconductor optical waveguide that is generally used as a light source. It is impossible to couple them, and they are large in size, have high optical waveguide loss, and have a low coupling coefficient with light sources, optical switches, etc.

[Purpose of the invention]

This invention was made to solve the above problems.
(7) To provide an optical isolator that can be monolithically coupled with a semiconductor laser or a semiconductor optical waveguide, is small, has low optical waveguide loss, and has a high coupling coefficient with a light source, optical switch, etc. The present invention aims to provide a method for manufacturing an optical isolator.

[Summary of the invention]

In order to achieve this object, in the present invention, an island-shaped magneto-optic crystal is formed on an amorphous material, and the magneto-optic crystal is used as an optical waveguide. Furthermore, an island-like magneto-optic material is formed on an amorphous material, and the magneto-optic crystal is single-crystalized by a laser annealing method to form a magneto-optic crystal.

In other words, the present invention has developed a technique for crystal-growing a material different from a semiconductor substrate through an amorphous material in order to crystal-grow a magneto-optical material or an optically active material, which is a component of an optical isolator, on a semiconductor substrate. This was achieved by

As a technique for forming a single crystal thin film on an amorphous material, for example, there is a method published by J. F. Gibbons et al. in which polycrystalline Si formed in an island shape on amorphous 5iaN4 is made into a single crystal by laser annealing. (J
, p, Qibl) ons etaI, Appl
, PhYs, Lett.

34, (12), 831 (1979)). This invention was inspired by these methods, and as a result of studying a method for growing an oxide single crystal film of an optical material on a ■-■ compound semiconductor substrate via an amorphous material. This is based on the establishment of a technology that enables the production of single-crystal films.

Furthermore, this invention was made based on the discovery that the island-shaped single crystal film formed by this method functions as an optical waveguide.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail by way of examples.

Example 1 FIG. 2 is a sectional view showing an optical isolator according to the present invention,
FIG. 3 is a perspective view showing a part of the optical isolator. In the figure, 10 is a ■-■ compound semiconductor substrate, 5 is a light absorber provided on the substrate 1O, and the light absorber 5 is an optical waveguide and an optical thin film provided in close contact with its surface.
It has the same function as a polarizing plate. 9 is an amorphous material provided on the substrate 10, 6 is an island-shaped magneto-optic crystal formed on the amorphous material 9, and the magneto-optic crystal 6 is long so that the Faraday rotation angle is 45°. It consists of an oxide single crystal film with a determined grain size. Reference numeral 7 denotes a magneto-optic crystal having an island-like Kotton-Morton effect formed on an amorphous material *9. The magneto-optic crystal 7 rotates the plane of polarization rotated by Faraday rotation again by 45 degrees and outputs the same. 8 is board 1
0, the light absorber 8 is a light absorber provided on the light absorber 5.
It has the same configuration and functions as .

In order to manufacture this optical isolator, first, the substrate 10 is coated with a 0.000.degree.
An amorphous material 9 made of silicon oxide with a thickness of 1 to 1 μm is provided. Next, YIG (yttrium iron garnet), TAG (terbium aluminum garnet), TIG (terbium iron garnet) are placed on the amorphous material 9.
A magneto-optical material with a relatively large Faraday rotation angle, such as GPIG (gadolium grasseodium iron garnet), is formed into a material with a thickness of 0.5 to 2 μm and a width of 2 to 10 μm using methods such as high frequency sputtering or plasma CVD. Form into islands. Next, a magneto-optical material having the Kotton-Morton effect is formed in the form of an island on the amorphous material 9 in the same manner. Next, since these magneto-optic materials are amorphous, the magneto-optic materials are crystallized by heating with a laser such as CO2 or Ar, that is, by laser annealing, to form magneto-optic crystals 6 and 7. form. At this time,
Although it is almost impossible to form a single crystal film over a wide area, it is extremely easy to form a single crystal of an island-shaped magneto-optic material. That is, monocrystallization of an elongated island-shaped thin film such as an optical waveguide can be carried out by moving a continuous wave laser beam of 5 to 20 W along the optical waveguide. Next, GaA is deposited on the substrate 10.
S.

By forming a III-V compound semiconductor guided waveguide such as Ga1xkLxAs or InP by, for example, molecular beam epitaxy, metal organic CVD, etc., and further depositing a metal thin film on its surface, the light absorber 5,
8 will be provided.

Embodiment 2 FIG. 4 is a sectional view showing another optical isolator according to the present invention. In Example 1, a magneto-optic crystal 7 having a Kotton-Morton effect was formed in order to efficiently couple with a planar optical waveguide or an optical modulator. optical crystal 7
did not form. Therefore, the polarization plane is output with its plane rotated by 45 degrees. Note that the material and manufacturing method of this optical isolator are the same as in Example 1.

Embodiment 3 FIG. 5 is a diagram showing an optical integrated circuit in which an optical isolator according to the present invention is monolithically coupled with a compound semiconductor laser and an optical circuit. In the figure, reference numeral 11 indicates a ■-■ compound semiconductor laser provided on the substrate 10, such as InG.
aAsP/I nP heterolaser, semiconductor laser 11
is molecular beam epitaxy or metal organic CV
Formed by method D. At this time, as the substrate 10,
If IV compound semiconductors are used, extremely high quality ■-v
Because compound semiconductor single crystal films can be grown,
An efficient semiconductor laser 11 can be obtained.

12 is a compound semiconductor optical circuit provided on the substrate 10 and has an optical modification function. Note that the semiconductor laser 1
1 can be formed simultaneously with the light absorbers 5 and 8.

Embodiment 4 FIG. 6 is a diagram showing a part of another optical isolator according to the present invention. This optical isolator has a structure in which a magneto-optic crystal 6 is covered with an amorphous material 9. Therefore, if a material having a smaller refractive index than the magneto-optic crystal 6, such as silicon oxide, is used as the amorphous material 9, the confinement efficiency in the magneto-optic crystal 6 can be improved.

In addition, the amorphous material 9 can prevent the magneto-optic material from evaporating and changing its shape during laser annealing, and the amorphous material 9 can also keep the magneto-optic material warm. It can be easily made into a single crystal.

In Examples 1 and 3, the magneto-optic crystal 7 having the Kotton-Morton effect was formed on the substrate 10, but NaClOs was used instead of the magneto-optic material.

HIO3, 28i06. An optically active material such as NaBrO3 can be used, and similarly to the magneto-optical material, this optically active material can also be made into a υ single crystal by laser annealing. Furthermore, in the above embodiment, silicon oxide was used as the amorphous material 9, but any material can be used as the amorphous material 9 as long as it maintains an amorphous state during laser annealing. can.

〔Effect of the invention〕

As explained above, the optical isolator according to the present invention can be monolithically coupled to a semiconductor laser or a semiconductor optical waveguide, is small in size, has low optical waveguide loss, and has a low coupling coefficient with a light source, optical switch, etc. expensive. Further, in the method for manufacturing an optical isolator according to the present invention, since the magneto-optic material is single-crystallized by laser annealing to form a magneto-optic crystal, the optical isolator can be manufactured extremely easily. As described above, the effects of this invention are remarkable.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional original isolake, FIG. 2 is a sectional view showing an optical isolator according to the present invention, and FIG.
FIG. 4 is a perspective view showing a part of the optical isolator shown in the figure, FIG. 4 is a diagram showing another optical isolator according to the present invention, and FIG. 5 is a monolithic combination of a semiconductor laser and an optical circuit to the optical isolator according to the present invention. A diagram showing a photonic integrated circuit,
FIG. 6 is a perspective view showing a part of another optical isolator according to the present invention. Death...Light absorber, 6,7...Magneto-optical crystal, 8...
Light absorber, 9... Amorphous material, 10... Substrate, 11
... Semiconductor laser, 12... Semiconductor optical circuit. Agent Patent Attorney Toshiken Usuda Figure 1 Figure 3 Atsushi Atsushi Figure 5

Claims (1)

[Claims] 1. An optical isolator characterized in that an island-shaped magneto-optic crystal is formed on an amorphous material, and the magneto-optic crystal is used as an optical waveguide. 2. A method for producing an optical isolator, which comprises forming an island-shaped magneto-optic material on an amorphous substance, and single-crystallizing the magneto-optic material by laser annealing to form a magneto-optic crystal.