JPS61292613A - Faraday rotor and its production - Google Patents

Abstract

PURPOSE:To compensate the change of the coefft. of Faraday rotation with a temp. change by providing the coefft. of Faraday rotation having the temp. characteristic to change in the directions opposite from each other to a Faraday rotor so that the change by temp. of the Faraday rotation received by the light perpendicularly transmitted through the 1st and 2nd films if offset by the 1st and 2nd films and is minimized. CONSTITUTION:The Faraday rotor is formed by using a crystal growth method in which a non-magnetic substrate 20 is brought into contact with the melt in a crucible placed in a vertical furnace and a single crystal film is obtd. on said substrate by a liquid phase epitaxial method. The material of which the coefft. of Faraday rotation approaches 0 from the minus side with a temp. increase is grown at the 1st film 21 on the substrate 20 and the material of which the coefft. of Faraday rotation approaches 0 from the plus side is grown as the 2nd film 22 on the 1st film 21. The temp. change of the coefft. of Faraday rotation received by the light perpendicularly transmitted through the 1st film and the 2nd film is thus minimized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a Faraday rotator and a method for manufacturing the same.
In particular, the present invention relates to a method for manufacturing a Faraday rotator using a liquid phase epitaxial method.

[Conventional technology]

Liquid phase epitaxial (
Magnetic garnet liquid phase epitaxial crystal films grown by the LPE method are important for use in magneto-optical devices.

As disclosed in Japanese Unexamined Patent Publication No. 57-17919, even if this magnetic LPE film is made thicker, performance equivalent to that of bulk garnet crystal can be obtained, thereby attempting to reduce the cost of bulk, which was previously expensive. It is being The crystal growth method for thickening the magnetic garnet film is as shown in FIG. 5 and a nonmagnetic garnet substrate 4 held by an alumina rod 6 are inserted from above into the crucible and immersed in the melt, thereby causing crystal growth. 7 is a heater.

8 is a crucible support stand.

[Problem that the invention seeks to solve]

Magneto-optical materials grown by this method are used as Faraday rotators in optical isolators used to stabilize the oscillation of semiconductor lasers in optical fiber communication technology. A schematic diagram of the optical isolator is shown in FIG. Emitted light 10 from the semiconductor laser 9 passes through a polarizer 11 and is separated into light having a vertical phase. From there, the phase of the light that passes through the Faraday rotator 12 is 4 in the traveling direction.
It rotates 5 times and enters the optical fiber through the analyzer 13, which has been tilted 45 degrees in advance. During optical fiber transmission, reflected light from connectors, optical switches, etc. returns to the analyzer 13 and enters the Faraday rotator 12. This return light 14 is
The Faraday rotator 12 further rotates the light by 45 times and shifts the phase of the emitted light by 90''. Since the polarizer 11 transmits only the vertical phase, the returned light 14 is blocked here. The light 14 returns to the laser 9 and stable oscillation is possible without being incident.Currently, (GdY)5Fe5012.Y,F is used as a Faraday rotator.
e501□.

Gd2Bi1Fe501□ and the like are used.

[Problem that the invention seeks to solve]

These materials are suitable for wavelengths 1 and 3 of semiconductor lasers for optical communications.
Small absorption coefficient (below 1.5 m-1) in the μm band
and a large Faraday rotation coefficient (200 to 1
500deg/Crn, that is, 200 to 1 per meter of thickness
Rotates 500 times. ), the sample shape is 2.2 to 0.
, 3 tan thick and serves as a Faraday rotator. Therefore, it is considered to be an extremely suitable material for incorporating into small semiconductor radar diode modules. However, the Faraday rotation coefficient of these materials changes with respect to temperature changes. FIG. 5 shows the temperature change in the Faraday rotation coefficient of the Gd2Bi1Fe501□ film. Therefore,
When a temperature change occurs in the above-mentioned optical isolator, there is a problem in that the isolation function deteriorates and the oscillation of the semiconductor laser becomes unstable.

An object of the present invention is to provide a Faraday rotator that can compensate for changes in Faraday rotation coefficient due to temperature changes.

Another object of the present invention is to provide a method for manufacturing a Faraday rotator that can compensate for changes in the Faraday rotation coefficient due to temperature changes.

[Failure to solve the problem]

According to the present invention, the present invention has first and second films, and the first and second films are configured to prevent a change in Faraday rotation due to temperature of light that perpendicularly passes through the first and second films. A Faraday rotator is obtained, characterized in that the first and second films have Faraday rotation coefficients of temperature characteristics that change in opposite directions so as to be canceled out and minimized.

Further, according to the present invention, a first film is grown on the substrate using a crystal growth method in which a nonmagnetic substrate is brought into contact with the melt and a single crystal film is obtained on the substrate by liquid phase epitaxial method,
Subsequently, a second film is grown on the first film, and the first and second films are arranged such that the Faraday rotation of the light transmitted perpendicularly through the first and second films changes with temperature. , a method for manufacturing a Faraday rotator is obtained, characterized in that the first and second films have Faraday rotation coefficients of temperature characteristics that change in opposite directions so as to be canceled out and minimized. It will be done.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a Faraday rotator according to one embodiment of the present invention is shown. This Faraday rotator is formed using a crystal growth method in which a nonmagnetic substrate 20 is brought into contact with a melt in a crucible placed in a vertical furnace, and a single crystal film is obtained on the substrate by liquid phase epitaxial method. be done. At this time,
As shown in FIG. 2, a material whose Faraday rotation coefficient approaches 0 from the - side with respect to temperature rise is grown on the substrate 20 as the -th film 21, and the Faraday rotation coefficient is grown on the -th film 21. However, by growing a material that approaches O from the + side as the second film 22 as the temperature rises, the temperature change in the Faraday rotation coefficient of the light transmitted perpendicularly through the - film and the second film can be minimized. I will make it happen.

Specifically, PbO-Bi203-B203 based flux (111)Nd3Ga5012 substrate (non-magnetic substrate) 2
0 as the second film 21 by liquid phase epitaxial method. . Bill,.

Fe4.65AtO,05Ga0.30012 was grown. As shown in Figure 2, the Faraday rotation coefficient of this material changes from one value to 0 when the temperature rises from 0 to 50°C.
approach. The thickness of the first film 21 was approximately 150 μm.

-th film 21 (0 surface is polished without distortion by mechanochemical polishing + Gd from P b O-B 20 s flux
2. QB' 1.0Fe4.65 0-5 as shown
For a temperature increase of 0°C.

The Faraday rotation coefficient approaches O from the + side value.

The thickness of the second film 22 was approximately 700 μm. After strain-free polishing on the second film again by mechanochemical polishing,
As a result of examining the temperature dependence of the Faraday rotation coefficient by transmitting light perpendicularly to the first film 21 and the second film 22, the results are as shown at 30 in FIG.

It was found that the material has a nearly constant Faraday rotation coefficient that shows very little variation with respect to temperature changes.

Note that since the substrate 20 is a non-magnetic material, the magnetic field does not cause Faraday rotation, and the temperature characteristics of the Faraday rotation coefficients of the first film 21 and the second film 22 are not affected. Therefore, the first film 21 and the second film 22 may be used as a Faraday rotator with the substrate 20 attached. Of course, it may be used as a Faraday rotator with the substrate 20 removed.

Further, in the above embodiment, the Faraday rotation coefficient of the -th film approaches 0 from a - value with respect to temperature rise.

On the contrary, in the case of the second film, the value approached 0 from the value of 10, but it goes without saying that the same effect can be obtained even if the order of the first and second films is switched.

Furthermore, the same effect can be obtained by dividing the thickness of the first film into first and third films and forming the first, second, and third films in this order. The same effect was obtained even when the thickness of the film was divided into second and fourth films, and the entire film was composed of the first to fourth films.

In addition, although the cost of the first film 21 and the second film 22 is high, C
■It may be formed by a method.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a Faraday rotator that can compensate for changes in the Faraday rotation coefficient due to temperature changes.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a Faraday rotator according to an embodiment of the present invention, and FIG. 2 shows the temperature dependence of the Faraday rotation coefficient of the first film and second film in FIG. 1, and the second film and the second film. Figure 3 shows the temperature dependence of the Faraday rotation coefficient when light is transmitted perpendicular to Gd2. [
1B 11. FIG. 3 is a diagram showing the temperature dependence of the Faraday rotation coefficient of the o Fe so 12 film. 1 is the LPE furnace body (vertical furnace), 2 is the melt, 3 is the crucible, 4 is the garnet substrate, 5 is the platinum jig, 6 is the alumina rod, 7 is the heater, 8 is the crucible support stand, 9 is a semiconductor laser, 11 is a polarizer, 12 is a Faraday rotator, 13
is the analyzer, and 20 is the board. 21 is a first film, and 22 is a second film. Figure 1 r> to ID1b-Issai Haru Hajime

Claims (1)

[Claims] 1. has a first and a second film, the first and second film are:
Temperatures that change in mutually opposite directions so that changes due to temperature in Faraday rotation experienced by light that perpendicularly transmits through the first and second films are canceled out by the first and second films and minimized. A Faraday rotator characterized by having a characteristic Faraday rotation coefficient. 2. A nonmagnetic substrate is brought into contact with the melt, and a first film is grown on the substrate using a crystal growth method in which a single crystal film is obtained on the substrate by liquid phase epitaxial method, and then the first film is grown on the substrate. a second film is grown on the first and second films, and the first and second films are arranged such that the temperature-dependent change in Faraday rotation of light transmitted perpendicularly through the first and second films A method for manufacturing a Faraday rotator, characterized in that it has Faraday rotation coefficients of temperature characteristics that change in opposite directions so as to be canceled out and minimized by a second film.