JP3084482B2 - Magneto-optical element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magneto-optical element used for a Faraday rotator such as an optical isolator and a magnetic field sensor.

[Prior Art] Conventionally, when a semimagnetic semiconductor Cd _1-x Mn _x Te (0 <x ≦ 0.7) crystal is manufactured by the Bridgman method, twin defects are known to occur. When a crystal having twin defects is used as a Faraday rotator, there is a problem that practically sufficient light transmittance cannot be obtained. The generation of twin defects is attributed to the phase transformation of this material, and it is described that when the phase transitions from hexagonal, which is a high-temperature phase, to cubic, which is a low-temperature phase, twins are formed.

Therefore, in order to avoid twin defects, crystal growth has been conventionally performed below the phase transformation temperature using the melting zone transfer method (THM: Traveling Heater Method).

[Problems to be Solved by the Invention] However, although crystals produced by the THM method have practically sufficient optical characteristics, the growth rate is higher than that of the Bridgman method.
Since it is 1/10 or less, there is a disadvantage that productivity is poor and costs are high.

Therefore, the technical problem of the present invention is to provide a Faraday rotator element having a low insertion loss and a sufficiently high light transmittance even with a Cd _1-x Mn _x Te crystal manufactured by the Bridgman method having excellent productivity. The purpose is to provide.

[Means for Solving the Problems] According to the present invention, in a magneto-optical element that transmits laser light, a cadmium-manganese-tellurium Cd _1-x MnxTe (0 <x ≦ 0.7) single crystal produced by the Bridgman method And a means for making the laser light incident on a crystal plane of the single crystal having a mirror index of {111}.

[Operation] The present invention provides a Cd grown by the Bridgman method as a magneto-optical element used for an optical isolator magnetic field sensor or the like.
The Miller index of _1-x Mn _x Te (0 <x ≦ 0.7) single crystal is {111}
The laser beam is made incident on the crystal plane perpendicularly to the crystal plane by using the {111} plane. Even though there are twin defects, the light transmittance does not decrease.

That is, conventionally, since the Verdet constant of this crystal does not depend on the orientation of the crystal plane, the Faraday rotator has been constituted by an arbitrary plane. On the other hand, the twin defects generated in this crystal have a regular structure stacked vertically in the {111} direction.

When light is perpendicularly incident on the surface other than the {111} plane by the incident means, the light is diffracted at the twin boundary and the transmitted light becomes a spread beam, so only a part of the transmitted light reaches the light receiving surface Not doing so causes a decrease in light transmittance.

Therefore, when the light is perpendicularly incident on the {111} plane by the incidence means, since the light does not hit the twin boundary, no diffraction occurs and the beam diameter does not change. Will be the same as

EXAMPLES Hereinafter, the present invention will be specifically described using one example.
Composition Cd _1-x Mn _x Te (x = 0.2,0.45) by Bridgman method
Was grown. These crystals have about 1 in the {111} direction.
It had a structure in which twin planes overlapped at 0 μm intervals. Samples were prepared by cutting out the {111} plane parallel to the twin plane, the {110} plane perpendicular to the {111} plane, and a randomly determined plane, and performing optical polishing. The thickness of each sample was 1.00 mm. The light receiving area of the light receiving element is 5 mm × 5 mm, the wavelength is 633 nm,
The light transmittance was measured using a laser having a beam diameter of 1 mm at 850 nm.

For comparison, the light transmittance was similarly measured for a sample having the same composition and thickness without twin defects grown by the THM method. The measurement results are shown in FIGS. 3, 4 and 5.

As a result of the above measurement, at all wavelengths and compositions,
When the laser beam is incident on the 1｝ surface, the light transmittance does not change even if the distance between the sample and the light receiving element is changed, which is particularly advantageous when used in a device having a large optical path length. The magnitude of the transmittance was the same level as that grown by the THM method, and the level required for optical isolators, magnetic field sensors, etc. was obtained.

[Effects of the Invention] As described above, according to the present invention, a magneto-optical element having low insertion loss can be provided at low cost.

[Brief description of the drawings]

1 and 2 are conceptual diagrams for explaining the operation of the present invention. FIG. 2 shows a case where light is incident on a plane other than the {111} plane, and FIG. Show. FIGS. 3, 4 and 5 show the measured light transmittance of the sample as a value corrected in consideration of the reflectance. Units%
(percent). FIG. 3 shows a result of measuring a crystal having a composition of Cd _0.8 Mn _0.2 Te at a wavelength of 850 nm. Figure 4 shows the composition Cd _0.55 Mn
_0.45 Te crystal was measured at a wavelength of 633 nm. Fifth
The figure shows a crystal having a composition of Cd _0.55 Mn _0.45 Te measured at a wavelength of 850 nm.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/09 501 G02B 27/28 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A magneto-optical device for transmitting laser light, comprising cadmium, manganese, and cadmium produced by the Bridgman method.
A magneto-optical element comprising: a tellurium Cd _1-x MnxTe (0 <x ≦ 0.7) single crystal; and an incidence means for causing the laser light to enter a crystal plane having a mirror index of {111}. .