JP2007308327A - Manufacturing method of bismuth-substituted rare earth iron garnet thick film single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of reducing and stabilizing an insertion loss of a magnetic garnet. <P>SOLUTION: In the manufacturing method of a bismuth-substituted rare earth iron garnet thick film single crystal represented by the formula (R, Bi)<SB>3</SB>(Fe, M)<SB>5</SB>O<SB>12</SB>(wherein R is at least one kind selected among Eu, Gd, Ho, Yb and Y, and M is Al, Ga or both and its amount may be zero) and grown on a single crystal substrate by a liquid phase epitaxial growing method, a molten liquid obtained by dissolving a raw material of the bismuth-substituted rare earth iron garnet thick film single crystal to a molten material consisting of PbO-Bi<SB>2</SB>O<SB>3</SB>-B<SB>2</SB>O<SB>3</SB>is agitated at a holding step of about 1,000°C and a temperature falling step to a thick film growing temperature of 760-780°C, then the thick film single crystal is grown. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a bismuth-substituted rare earth iron-based garnet thick film single crystal by a liquid phase epitaxial growth method.

  In the past, devices using Faraday rotation have been developed and put into practical use in optical communications and optical information processing. In an optical communication device using a semiconductor laser oscillator, when reflected light from the end of an optical fiber cable or connector returns to the laser oscillator, noise increases and oscillation becomes unstable. In order to block such return light and ensure a stable oscillation state, an optical isolator using non-reciprocity of Faraday rotation is used.

  At present, in a communication system using an optical fiber cable, a band having a wavelength of 1.3 μm to 1.6 μm is used. There is a substituted rare earth iron-based garnet single crystal (hereinafter referred to as magnetic garnet). As a thick film single crystal, there is a material using Eu, Tb, Gd, Ho, Yb or the like as a rare earth element (Patent Document 1, etc.).

JP 2002-308696 A

As characteristics required for the magnetic garnet, in addition to the Faraday rotation effect, there is a low insertion loss, that is, a small attenuation of light in the magnetic garnet. In the conventional magnetic garnet, for example, in the general formula Gd _2.1 Bi _0.9 Fe _4.5 Al _0.3 Ga _0.2 O ₁₂ , the insertion loss is 0.03 to 0.15 dB at a wavelength λ = 1.55 μm, and the variation is large and stable. Insertion loss was not obtained.

  In view of the above problems, the present inventor has an object to provide a manufacturing method capable of reducing and stably inserting a magnetic garnet.

As a result of various investigations by the present inventors, in a melt obtained by dissolving a magnetic garnet component in a PbO—Bi ₂ O ₃ —B ₂ O ₃ melt, stirring with a Pt jig is continued from about 1000 ° C. to thick film. It was found that a magnetic garnet with reduced insertion loss and good reproducibility can be obtained by continuously performing the growth up to the single crystal growth start temperature and subsequently performing the thick film single crystal growth.

As described above, according to the present invention, the general formula (R, Bi) ₃ (Fe, M) ₅ O ₁₂ (where R is at least one selected from Y, Eu, Gd, Ho, Yb, M Represents Al, Ga, or both, and the amount of M includes zero). In a method for producing a magnetic garnet grown on a single crystal substrate by liquid phase epitaxial growth, PbO—Bi ₂ O ₃ —B By stirring the melt obtained by dissolving the magnetic garnet raw material in the melt composed of ₂ O ₃ from the holding at about 1000 ° C. to the growth starting temperature of the thick single crystal 760 to 780 ° C., a stable low insertion loss Magnetic garnet is obtained.

  The manufacturing method of the bismuth-substituted rare earth iron-based garnet thick film single crystal in one embodiment of the present invention is as follows.

In the first step, a predetermined amount of the metal oxide powder raw material is weighed. In the second step, (R, Bi) ₃ (Fe, M) ₅ O ₁₂ (where R is at least one selected from Eu, Gd, Ho, Yb, Y, and M is Al, Ga or Both are shown, and the amount of M includes zero). The raw material powder of the bismuth-substituted rare earth iron-based garnet represented by the PbO—Bi ₂ O ₃ —B ₂ O ₃ flux powder and the oxygen concentration of the atmospheric gas Melt while setting. In the third step, the melt is stirred with plate-like Pt while being held at a temperature of 980 to 1020 ° C. corresponding to each composition. In the fourth step, the temperature is lowered to a thick film growth start temperature 760 to 780 ° C. corresponding to each composition while continuing the same stirring as in the previous step. In the fifth step, a thick single crystal is grown by LPE (liquid phase epitaxial growth) on a substrate that matches the lattice constant. In the sixth step, the substrate is removed by polishing to obtain the bismuth-substituted rare earth iron garnet thick film single crystal of the present embodiment.

  Next, examples limited to a bismuth-substituted rare earth iron-based garnet thick film single crystal having a specific composition will be described.

99.99% pure gadolinium oxide Gd ₂ O ₃ , ferric oxide Fe ₂ O ₃ , aluminum oxide Al ₂ O ₃ , gallium oxide Ga ₂ O ₃ , and 99.9% pure lead oxide PbO, bismuth oxide Bi Using a powder of ₂ O ₃ and boron oxide B ₂ O ₃ and a PbO—Bi ₂ O ₃ —B ₂ O ₃ system as a flux, an Nd having a lattice constant of 2 inches in diameter and a = 1.2509 nm by the LPE method. A magnetic garnet of the general formula Gd _2.1 Bi _0.9 Fe _4.5 Al _0.3 O ₁₂ was grown on a ₃ Ga ₅ O ₁₂ (hereinafter referred to as NGG) substrate to a thickness of 600 to 660 μm.

  At this time, the oxygen concentration of the atmospheric gas being grown was set to 18%. Further, the stirring with the Pt jig was continuously performed at 1000 ° C. for 8 hours and for 3 hours 30 minutes during the temperature drop to the thick film growth temperature of 765 ° C. After the growth, the substrate was cut into 11 mm × 11 mm, and then the NGG substrate was removed by polishing to obtain a thick film single crystal sample.

  Next, both surfaces are mirror-finished by chemical mechanical polishing (hereinafter referred to as MC polishing) to a thickness of 500 μm with a Faraday rotation angle of 45 deg at 1.55 μm, and a non-reflective coating film for a wavelength of 1.55 μm is applied to both surfaces. The insertion loss was measured.

  As a comparative example, the result of insertion loss of a thick film single crystal obtained by conventional stirring at 1000 ° C. for 8 hours (that is, when stirring was not performed during the temperature drop from 1000 ° C. to thick film growth start temperature) Is shown in Table 1 and FIG. In addition, both Example 1 and the comparative example are the results of 50 lots in total grown 10 times in 5 liquid phase epitaxial growth furnaces.

  As shown in Table 1 and FIG. 1, in Example 1, a low insertion loss of 0.02 to 0.04 dB was stably obtained, but in the comparative example, the variation in insertion loss was 0.03 to 0.13 dB. Large and unstable.

The figure which shows the histogram of the insertion loss of Example 1 and a comparative example of this invention.

Claims (1)

General formula (R, Bi) ₃ (Fe, M) ₅ O ₁₂ (where R is at least one selected from Eu, Gd, Ho, Yb, Y, and M is Al, Ga, or both) In the method for producing a bismuth-substituted rare earth iron-based garnet thick film single crystal grown on a single crystal substrate by a liquid phase epitaxial growth method, the PbO—Bi ₂ O ₃ —B ₂ A melt obtained by dissolving the raw material of the bismuth-substituted rare earth iron-based garnet thick film single crystal in a flux composed of O ₃ is stirred at a holding temperature of 980 to 1020 ° C., and a thick film growth start temperature 760 to 780 is maintained from the holding temperature. A method for producing a bismuth-substituted rare earth iron-based garnet thick film single crystal, which is stirred while the temperature is lowered to ° C.

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