Translucent sintered body, a Faraday rotator made of this sintered body, and an optical isolator

Abstract

A translucent sintered body having the following basic composition:
Ca.sub.(1−x)Yb.sub.xF.sub.(2+x), where 0.4≦x≦1.0,
or preferably
Ca.sub.(1−x−y)Yb.sub.xR.sub.yF.sub.(2+x+y), 0.4≦x≦1.0, 0≦y≦0.5 wherein R is at least one element selected from Ce, Pr, Sm, Eu and Y.

Claims

1. A translucent sintered body comprising a composition represented by the following formula:
Ca.sub.(1−x−y)Yb.sub.xR.sub.yF.sub.(2+x+y), 0.4<x≦1.0, 0<y≦0.5, 0.1≦1−x−y, wherein R is at least one element selected from Ce, Pr, Sm, Eu and Y.

2. A translucent sintered body as claimed in claim 1, having a transmittance of 60% or higher with respect to the lights of wavelength range of 140 nm through 450 nm.

3. A Faraday rotator comprising a translucent sintered body according to claim 1.

4. A Faraday rotator comprising a translucent sintered body according to claim 2.

5. An optical isolator comprising a Faraday rotator of claim 3.

6. An optical isolator comprising a Faraday rotator of claim 4.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a graph to show a relationship between the wavelengths of Ca.sub.0.5Yb.sub.0.5F.sub.2.5 and YbYO.sub.3 on the horizontal axis and the transmittance thereof on the vertical axis.

(2) FIG. 2 is a schematic drawing showing the structure of an optical isolator.

EXAMPLES EMBODYING THE INVENTION

(3) Now, examples of the present invention will be explained, but these shall not be construed to limit the scope of the present invention.

(4) The sintered body of the present invention basically comprises elements of Ca plus Yb plus F or Yb plus F in a manner as represented by the following formula:
Ca.sub.(1−x)Yb.sub.xF.sub.(2+x), 0.4≦x≦1.0.

(5) The sintered body of the present invention may further include one or more of elements Ce, Pr, Sm, Eu, and Y in a manner as represented by the following formula:
Ca.sub.(1−x−y)Yb.sub.xR.sub.yF.sub.(2+x+y), 0.4≦x≦1.0, 0≦y≦0.5
wherein R is one or more elements selected from Ce, Pr, Sm, Eu and Y.

(6) The sintered body of the present invention has an intensified transmittance of at least 60% for the lights of wavelength range of 140 nm through 450 nm, and in the case where one or more of the elements Ce, Pr, Sm, Eu, and Y is contained, it exhibits a transmittance of 70% or higher. Also, the sintered body of the present invention can secure high Verdet constant as well as excellent translucency so that it is a favorable material to make the Faraday rotator of optical isolators which are used in the applications of optical communication and optical measurement, since such an optical isolator using a Faraday rotator made of this sintered body can exhibits a high transmittance over a wide range of wavelength bands.

EXAMPLES

(7) We will now describe examples of the present invention.

Example 1

(8) Aqueous solution of calcium fluoride (CaF2) and aqueous solution of ytterbium fluoride are mixed together in ratios of 0.4:0.6, 0.5:0.5, 0.4:0.6, 0.2:0.8, and 0.0:1.0, respectively, and to each of these acetic acid was dripped to cause precipitation, and the precipitate was dried, whereby powdery fluorides of the above ratios were obtained. Then, these powders were molded by being pressed in a die, and were heated at temperatures of 700 through 1300 degrees C., and a sintered body having a relative density of 95% or higher was manufactured.

(9) This sintered body was subjected to a hot isotropic pressure (HIP) sintering in an inert atmosphere such as argon or nitrogen under a pressure of 500 through 3000 kg/cm2 at a temperature of 1000 through 1300 degrees C., whereby a translucent sintered body having a relative density of 99% or higher was manufactured.

(10) Then, this translucent sintered body was shaped into a body of 5 mm in outer diameter and 4 mm in thickness, and the both circular faces were polished; the measurements were conducted for transmittance and Verdet constant in the instances of wavelengths of 325 m and 194 nm, respectively, and results were as shown in Table 1. Incidentally, in Table 1, the ratio of F is not entered among the composition ratios. Also, with respect to Ca.sub.0.5Yb.sub.0.5F.sub.2.5, a transmission spectrum measurement was conducted and the result is as shown FIG. 1.

(11) TABLE-US-00001 TABLE 1 Optical Characteristics Composition Verdet constant Ca Yb R Transmittance (%) [min/(Oe .Math. cm)] 1 − x − y x y 325 nm 194 nm 325 nm 194 nm 0.6 0.4 0.0 90 90 0.21 0.62 0.5 0.5 0.0 90 90 0.23 0.73 0.4 0.6 0.0 89 87 0.32 0.98 0.2 0.8 0.0 87 86 0.43 1.32 0.0 1.0 0.0 76 70 0.55 1.67

(12) From the results shown in Table 1, it is seen that the transmittance was in any instance 70% or higher with respect to the light wavelengths of 325 nm and 194 nm; and in cases where Ca is contained the transmittance was in any instance 86% or higher and the Verdet constant was large enough.

Comparative Example 1

(13) Oxide single crystal bodies were made by FZ method which had a composition such that the ratio of Yb.sub.2O.sub.3:Y.sub.2O.sub.3 was 50:50 and 60:40; then they were machined to the same dimensions as in the case of Example 1, and when the transmittance was measured of them with respect to light wavelengths of 325 nm and 194 nm and in the case of 325 nm the Verdet constant was also measured. Table 2 shows the results. With respect to the sample of 50:50 ratio, a transmission spectrum measurement was also conducted and the result is as shown FIG. 1.

(14) TABLE-US-00002 TABLE 2 Optical Characteristics Composition Transmittance Verdet constant Yb.sub.2O.sub.3 Y.sub.2O.sub.3 (%) [min/(Oe .Math. cm)] X y 325 nm 194 nm 325 nm 194 nm 0.5 0.5 50 <1 0.24 *** 0.6 0.4 48 <1 0.32 *** *** transmittance was too low for measurement of Verdet constant

(15) From the results shown in Table 2, it is seen that in Comparative Example 1, the transmittance was in any instance 50% or lower with respect to the light wavelength of 325 nm. In the case of 195 nm, the transmittance was too low to allow measurement of the Verdet constant.

Example 2

(16) Employing the same procedure as described in Example 1, a powder was obtained, which was a mixture of calcium fluoride (CaF.sub.2), ytterbium fluoride and rare earth fluorides. This powder was molded by being pressed in a die, and was heated at temperatures of 700 through 1300 degrees C., and a sintered body having a relative density of 95% or higher was manufactured.

(17) This sintered body was subjected to a hot isotropic pressure (HIP) sintering in an inert atmosphere such as argon or nitrogen under a pressure of 500 through 3000 kg/cm2 at a temperature of 1000 through 1300 degrees C., whereby a translucent sintered body having a relative density of 99% or higher was manufactured.

(18) Then, this translucent sintered body was shaped into a body of 5 mm in outer diameter and 4 mm in thickness, and the both circular faces were polished; the measurements were conducted for transmittance and Verdet constant in the instances of wavelengths of 325 m and 194 nm, respectively, and results were as shown in Table 3. Also in Table 3, the ratio of F is not entered among the composition ratios. Also, with respect to Ca.sub.0.5Y.sub.0.5F.sub.2.5, a transmission spectrum measurement was conducted and the result is as shown FIG. 3.

(19) TABLE-US-00003 TABLE 3 Optical Characteristics Composition Verdet constant Ca Yb R Transmittance (%) [min/(Oe .Math. cm)] 1 − x − y x y 325 nm 194 nm 325 nm 194 nm 0.10 0.5 Y 0.4 89 88 0.24 0.74 0.20 0.6 Y 0.2 86 86 0.31 0.94 0.20 0.7 Ce 0.1 86 84 0.40 1.15 0.25 0.6 Pr 0.15 88 88 0.26 0.78 0.20 0.6 Eu 0.2 84 84 0.28 1.00 0.20 0.5 Sm 0.3 86 86 0.24 0.76 0.00 0.5 Sm 0.5 88 88 0.23 0.72

(20) From the results shown in Table 3, it was confirmed that it was possible to obtain materials of which the transmittance was 84% or higher with respect to the light wavelengths of 325 nm and 194 nm and of which the Verdet constant was large enough.

Example 3

(21) The sintered body Ca.sub.0.2Yb.sub.0.3F.sub.2.8 obtained in Example 1 was shaped into a body of 5 mm in outer diameter and 5.2 mm in thickness, and the both circular faces were polished and coated with a 325 nm-thick air-resistive AR (antireflection) layer; the thus prepared piece was put within the magnet to construct a Faraday rotator. Then the insertion loss and the extinction ratio were measured of this Faraday rotator, and they were 0.2 dB and 35 dB, respectively, which are considered excellent.

(22) On either end of the magnet a Glan-Thompson prism made of MgF.sub.2 (insertion loss 0.5 dB; extinction ratio 48 dB) was set and fixed in a manner such that the relative angle was 45 degrees, and thus an optical isolator was constructed. Then this optical isolator was measured for the insertion loss and it was found that the forward direction insertion loss was 1.2 dB and the reverse direction loss was 32.5 dB, which are excellent for an optical isolator.

Example 4

(23) The sintered body Ca.sub.0.2Yb.sub.0.3F.sub.2.8 obtained in Example 1 was shaped into a body of 5 mm in outer diameter and 2.0 mm in thickness, and the both circular faces were polished and coated with a 194 nm-thick air-resistive AR layer; the thus prepared piece was put within the magnet to construct a Faraday rotator. Then the insertion loss and the extinction ratio were measured of this Faraday rotator, and they were 0.3 dB and 33 dB, respectively, which are considered excellent.

(24) On either end of the magnet a Glan-Thompson prism made of MgF.sub.2 (insertion loss 0.65 dB; extinction ratio 45 dB) was set and fixed in a manner such that the relative angle was 45 degrees, and thus an optical isolator was constructed. Then this optical isolator was measured for the insertion loss and it was found that the forward direction insertion loss was 1.6 dB and the reverse direction loss was 31.2 dB, which are excellent for an optical isolator.

REPRESENTATION OF REFERENCE NUMERALS

(25) 1: Faraday rotator 2: polarizer (Glan-Thompson) 3: magnet 4: stainless steel ring