JP3077001B2 - Magneto-optical material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a wavelength of 0.6 to 0.8 .mu.m.
The present invention relates to a Faraday rotator such as an optical isolator used in the m region, a magneto-optical material used for the Faraday rotator and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, short wavelength (0.6 to 0.8 μm band)
The use of an optical isolator for removing return optical noise has been proposed in optical communication, optical measurement, magneto-optical recording and the like using a semiconductor laser and a gas laser as a light source. The use of semimagnetic semiconductor Cd _{1- x} MnxTe (0 <x ≦ 1) as a Faraday rotator material of the optical isolator is being studied.

[0003]

The Mn composition x is 0 ≦ x ≦
The 0.7 crystal is generally produced by solidification from the liquid phase by the Bridgman method. A phase transformation exists in the crystal, and the phase transformation from the high-temperature phase of hexagonal wurtzite to the low-temperature phase of cubic zinc-blende occurs during cooling of the crystal. Defects occur. Since twin defects cause birefringence to induce strain in the crystal and deteriorate the extinction characteristics, when this crystal is used as a Faraday element, its use is limited to the twin plane ({111} plane) and the process is complicated. And the yield has been reduced.

[0004] Therefore, technical problem of the present _{invention, Cd 1-x Mn x Te} (0 produced by the Bridgman method <x ≦ 0.
7) It is an object of the present invention to provide a Faraday rotator which has a practically sufficient extinction characteristic with a crystal, an inexpensive magneto-optical material used for the Faraday rotator and the like, and a method of manufacturing the same.

[0005]

Means for Solving the Problems The present inventors have the following:
The present inventors have experimentally found out the facts as described in the section, and have accomplished the present invention.

[0008] In a heat treatment at a temperature higher than the phase transformation point, twin defects disappear (however, light loss increases), and the quenching characteristics are improved.

[0007] Although the twin defects do not disappear by heat treatment at a temperature lower than the phase transformation temperature, the quenching characteristics improve as the temperature approaches the phase transformation point.

On the low side of the phase transformation temperature of 10 to 50 ° C., there is a temperature at which the decomposition and evaporation of the crystal components occur rapidly, and the light loss increases. Heat loss at a temperature lower than this temperature does not increase light loss.

That is, it has been found that the quenching characteristic can be improved without increasing the light loss by performing the heat treatment just below the temperature at which the decomposition and evaporation of the crystal components described in the section above occur.

According to the present invention, the formula _{Cd 1-x} Mn x
Te (where, 0 <x ≦ 0.7) is represented by, Bridgman
At most 100 from the phase transformation temperature
A magneto-optical material comprising a single crystal which has been heat-treated at a temperature lower by ° C. and characterized in that an arbitrary crystal plane can be used as an optical plane is obtained. According to the present invention, the chemical formula Cd _1-x M
n _x Te (where, 0 <x ≦ 0.7) is represented by, Bridgend
Made by the Ziman method and at most from the phase transformation temperature
A Faraday rotator characterized in that a crystal plane other than the {111} plane of the single crystal heat-treated at a temperature lower by 100 ° C. is used as an optical plane. According to the present invention, the chemical was produced by the Bridgman method Formula _Cd 1-x _Mn x Te (where, 0 <x
.Ltoreq.0.7), and a method for producing a magneto-optical material characterized by subjecting a single crystal to a heat treatment at a temperature at most 100.degree. C. lower than the phase transformation temperature.

[0011]

The present invention will be described below in detail with reference to examples.

According to the Bridgman method, the composition Cd _{1 -x} Mn _x
A single crystal of Te (x = 0.2, 0.5) was grown. The crystal had a structure in which twin defects overlapped in the {111} direction. Twin plane ({111} plane) and {11} perpendicular to it
A heat treatment was performed in a Cd or Te atmosphere by cutting out the {0} plane and the {112} plane.

The crystal having x = 0.5 has a wavelength λ = 0.6.
At 33 μm, a crystal with x = 0.2 has a wavelength λ = 0.78 μm.
After applying a magnetic field H = 0.5 T (tesla) at m, optical polishing is performed to a thickness that gives a Faraday rotation angle of 45 degrees, and an anti-reflection coating is applied to both surfaces.
Measured during application. Tables 1 and 2 show the measured values at various temperatures.
Shown in The phase transformation temperature is 870 ° C. for a crystal with x = 0.5,
The temperature is 1020 ° C. for a crystal with X = 0.2. As shown in Table 1, the heat loss of the crystal with x = 0.5 at 860 ° C. or more increases the light loss to exceed the practical level of 1 dB. 840 ° C
In the heat treatment, the extinction ratio is improved without changing the light loss as compared with that before the heat treatment. The value is practical level 3 in any aspect.
It has reached 0dB or more.

As shown in Table 2, the crystal with x = 0.2 is 98
Heat treatment at a temperature of 0 ° C. or higher increases the light loss and exceeds the practical level of 1 dB. In the heat treatment at 960 ° C., the extinction ratio is improved without changing the light loss as compared with that before the heat treatment. The value has reached a practical level of 30 dB or more in any aspect. That is, by using the heat treatment, the use was limited to the {111} plane when the conventional heat treatment was not performed.

On the other hand, the orientation of the ingot of the grown crystal is as shown in FIG. Also, {111}
Since the surface is perpendicular to the growth surface ({110} surface), it is necessary to expose the surface. In addition, as shown in FIG. 1B, the yield is about 70% because the ingot is cut longitudinally. Was.
According to the embodiment of the present invention, since it can be used on an arbitrary surface, a surfacing process is not required, and the cutting yield is improved to about 90% by slicing the ingot on the {110} surface.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

As described above, according to the present invention, a Faraday rotator having a practically sufficient extinction characteristic and used at a wavelength of 0.6 to 0.8 .mu.m and an inexpensive Faraday rotator used for this Faraday rotator and the like And a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1A is a perspective view showing the orientation of a crystal ingot grown by the Bridgman method. (B) is a side view of (a).

Claims (3)

(57) [Claims] 1. A chemical formula _Cd 1-x _Mn x Te (where 0
<X ≦ 0.7) and manufactured by the Bridgman method
Heat at a temperature at most 100 ° C lower than the phase transformation temperature
A magneto-optical material comprising a treated single crystal, wherein any crystal plane can be used as an optical surface. 2. The chemical formula Cd _1-x Mn _x Te (where 0
<X ≦ 0.7), the crystal plane other than the {111} plane of the single crystal produced by the Bridgman method and heat-treated at a temperature at most 100 ° C. lower than the phase transformation temperature was used as an optical surface. A Faraday rotator characterized by the following. 3. The chemical formula Cd1- produced by the Bridgman method.
A method for producing a magneto-optical material, wherein a single crystal represented by x Mnx Te (where 0 <x ≦ 0.7) is heat-treated at a temperature at most 100 ° C. lower than the phase transformation temperature.