JPH06222309A - Magneto-optical element - Google Patents

Abstract

PURPOSE:To provide the magneto-optical element adequate for use in a 0.8 to 1.1mum wavelength region. CONSTITUTION:This magneto-optical element has a Cd1-x-yMnxHgyTe single crystal having the compsn. included in a range enclosed by four points; Mn0.01 Hg0.04Cd0.95Te, Mn0.25Hg0.04Cd0.71Te in an MnTe-HgTe-CdTe pseudo ternary Mn0.25Hg0.04Cd0.71Te in an MnTe-HgTe-CdTe pseudo ternary phase diagram.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical element used as an optical isolator such as an optical amplifier, and more particularly to a magneto-optical element suitable for use in a wavelength range of 0.8 μm to 1.1 μm.

[0002]

2. Description of the Related Art Conventionally, 1.
The 5 μm traveling-wave optical amplifier is highly efficient, has no polarization dependence, and has excellent compatibility with the transmission system. From the practical viewpoint, laser diodes using 0.98 μm and 1.48 μm bands ( Hereinafter, LD) excitation has been actively studied. As a result of experimentally studying the signal light gain / noise characteristics, it has been found that the 0.98 μm band pump has higher efficiency and lower noise characteristics than the 1.48 μm band pump. However, at present, the development of an optical amplifier equipped with an optical device (optical isolator, etc.) suitable for the 1.48 μm band is progressing.

[0003]

At present, as the 0.98 μm optical isolator, an optical isolator employing a terbium gallium garnet (TGG) single crystal has been put into practical use. However, it is not considered from a future perspective because the size is too large as compared with the LD. In addition, bulk yttrium, iron, garnet (YIG) and Bi
The substituted garnet has a large absorption in the 0.98 μm band, and is thus impractical with a transmission loss of about 5 dB. C in which a part of Cd of CdTe having a ZnS type crystal structure is replaced with Mn
d _1-x Mn _x Te is a material with a large Verdet constant, and its practical performance was confirmed as an optical isolator material for visible light wavelengths of 0.85 to 0.63 μm (Onodera, Oikawa: The 15th Annual Meeting of the Japan Society for Applied Magnetics) Lecture summary 30aB-7,
p179 (1991)}.

However, at 0.98 μm, the Verdet constant was too small to be practically used.
That is, L used in the 0.98 μm pump optical amplifier
The fact that there is no optical isolator that can be used as a D module is essentially 1.48μ in terms of high efficiency and low noise characteristics.
This was one of the factors behind the delay in practical development, although it was superior to m-band excitation.

In view of the above drawbacks, the technical problem of the present invention is that the wavelength region is 0.8 μm to 1.1 μm (particularly 0.98 μm).
μm) for the purpose of providing a magneto-optical element suitable for use.

[0006]

According to the present invention, there is provided a magneto-optical element having a Cd _{1-x -y} Mn _x Hg _y Te single crystal mixed with Mn and Hg, wherein the single crystal has a wavelength of Mn so that it can be used in the region 0.8 μm to 1.1 μm.
In the Te-HgTe-CdTe pseudo-ternary phase diagram, Mn
_0.01 Hg _0.04 Cd _0.95 Te, Mn _0.01 Hg _0.1 Cd _0.89
Te, Mn _0.12 Hg _0.17 Cd _0.71 Te, Mn _0.25 Hg
A magneto-optical element having a composition contained in a range surrounded by four points of _0.04 Cd _0.71 Te is obtained.

Further, according to the present invention, there is provided an optical isolator comprising the magneto-optical element as a Faraday rotator.

[0008]

[Function] Cd _1-x Mn _x Te in which a part of Cd of CdTe having ZnS type crystal structure is replaced by Mn is a material having a large Verdet constant, and is an optical isolator material for visible light wavelength of 0.85 to 0.63 μm. Although the practical performance was confirmed as described above, the practical performance was not obtained in the 0.98 μm band due to the small Verdet constant. This is because the Verdet constant is large near the absorption edge of light. Therefore, in order to obtain practical performance using this material, consideration should be given to adjusting the bandgap energy of the material and selecting the Mn composition so that the absolute value of the Verdet constant becomes large. In order to shift the band gap energy to the 0.9 μm band, a part of Cd may be replaced with Hg. Eventually,
Bulk crystallinity has a large effect. Therefore, the optimum crystal composition is determined in consideration of the crystallinity.

According to the magneto-optical element of the present invention, an LD module having practical characteristics of isolation: 30 dB or more and insertion loss: 1 dB or less is possible.
It is possible to obtain an m-band optical isolator.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical element according to embodiments of the present invention will be described below with reference to the accompanying drawings.

First, selection of the optimum composition will be described.

Crystals of various compositions in the phase diagram of the MnTe-HgTe-CdTe pseudo-ternary system were prepared by the Bridgman method. Cd, Mn, Te, and Hg were mixed in a quartz ampoule in respective composition ratios and vacuum-encapsulated. If not completely melted at the time of heating, the quartz ampoule may crack due to the high vapor pressure, so the quartz ampoule should have a sufficient thickness and a Te excess composition of about 80%.
The melting point is set to about 0 ° C, and the internal pressure in the growing process is softened.

This quartz ampoule was placed in a vertical Bridgman furnace and held at a melting temperature of 800 ° C. for 10 hours. Then, the quartz crucible was gradually lowered to crystallize from one end of the low temperature portion of the quartz ampoule.

In FIG. 1, when an applied magnetic field of 3000 Oe that can realize an optical isolator (9.5φ × 10 Lmm) that can be formed into an LD module is added, isolation: 30
A composition that can realize an insertion loss of 1 dB or less and an insertion loss of 1 dB or more is shown. As shown in FIG. 1, the Cd _{1-x -y} Mn _x Hg _y Te single crystal that constitutes the magneto-optical element according to the present invention is MnTe.
In the -HgTe-CdTe quasi-ternary phase diagram, Mn _0.01
Hg _0.04 Cd _0.95 Te, Mn _0.01 Hg _0.1 Cd _0.89 T
e, Mn _0.12 Hg _0.17 Cd _0.71 Te, Mn _0.25 Hg _0.04
It has a composition contained in a range surrounded by four points of Cd _0.71 Te.

Examples of the present invention will be shown below.

Example 1 A single crystal having a composition of Mn _0.1 Hg _0.1 Cd _0.8 Te was made into T
e An excessive melt was used to grow at a low melting temperature (800 ° C.) by the Bridgman method. The breeding method is as described above. A square plate-like sample of 2 mm × 2 mm × 1.7 tmm was prepared from the grown single crystal so that the {111} plane was the end face. When a magnetic field of 3000 Oe was applied, a Faraday rotation of 45 ° was obtained for a laser beam with a wavelength of 0.98 μm, isolation: 30 dB, insertion loss: 0.7 dB, isolator size: φ8 × 5 Lm
It has become clear that m can be used sufficiently as an optical isolator.

Example 2 A single crystal having a composition of Mn _0.05 Hg _0.05 Cd _0.9 Te was T
e An excessive melt was used to grow at a low melting temperature (850 ° C.) by the Bridgman method. The breeding method is as described above. A square plate-like sample of 2 mm × 2 mm × 2.5 mm was prepared from the grown single crystal so that the {111} plane became the end face. When a magnetic field of 5000 Oe was applied, the wavelength was 0.
Faraday rotation of 45 ° was obtained for a laser beam of 98 μm, isolation: 30 dB, insertion loss:
0.7dB, isolator size: φ13 × 10Lm
It has become clear that m can be used sufficiently as an optical isolator. However, in view of the intended use, it is slightly larger than the semiconductor laser.

Comparative Example A single crystal having a composition of Mn _0.03 Hg _0.00 Cd _0.97 Te
e By using an excessive melt, it was grown by the Bridgeman method with low melting (1000 ° C.). The breeding method is as described above. A square plate-like sample of 2 mm × 2 mm × 7.0 mm was prepared from the grown single crystal so that the {111} plane was the end face. When a magnetic field of 5000 Oe was applied, the wavelength was 0.9.
Faraday rotation of 45 ° is obtained for 8 μm laser light, isolation: 25 dB, insertion loss:
1.0 dB, isolator size: φ13 × 15 Lm
It was m. The performance is insufficient for the intended use, and it is larger than the semiconductor laser from a practical point of view.

[0019]

As described above, according to the present invention,
It is possible to provide a magneto-optical element suitable for an optical isolator having a wavelength range of 0.8 to 1.1 μm.

[Brief description of drawings]

FIG. 1 shows a crystal composition of MnTe-HgTe that can realize an optical isolator that can be LD-modulated in the present invention.
-CdTe pseudo-ternary phase diagram.

Claims (2)

[Claims] _1. A Cd _{1-x -y} compounded with Mn and Hg.
A magneto-optical element having a Mn _x Hg _y Te single crystal, wherein the single crystal is MnTe-HgTe-CdTe pseudo-3 so that it can be used in a wavelength region of 0.8 μm to 1.1 μm.
In the original phase diagram, Mn _0.01 Hg _0.04 Cd _0.95 Te, Mn _0.01 Hg _0.1 Cd
_0.89 Te, Mn _0.12 Hg _0.17 Cd _0.71 Te, Mn _0.25 Hg _0.04 Cd
A magneto-optical element having a composition contained in a range surrounded by four points of _0.71 Te. 2. An optical isolator comprising the magneto-optical element according to claim 1 as a Faraday rotator.