JPH10101493A - Bismuth-substituted garnet material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a Bi-substituted garnet material improved in crystallinity largely influencing the characteristics of the material and reduced in insertion loss, and to provide a method for producing the material. SOLUTION: Lead oxide is added to a GdBi garnet single crystal or TbBi garnet single crystal in an amount of 0.05-1.5wt.% converted into PbO. The GdBi garnet single crystal or TbBi garnet single crystal is raised by a liquid phase growth method. Therein, a thermal treatment temperature is controlled to a range of 1000-1150 deg.C, and the oxygen concentration of the atmosphere on the thermal treatment is controlled to a range of 20-100vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bismuth (Bi) -substituted garnet material, which is an optical garnet material having a Faraday effect, and a method for producing the same, and more particularly to GdBi grown by a liquid phase growth method (LPE method). Garnet and TbBi-based garnet single crystal thick film and an improvement in a method for producing the same.

[0002]

2. Description of the Related Art Hitherto, devices using Faraday rotation in optical communication have been developed and put into practical use. At the time of optical communication, when a semiconductor laser is used, oscillation becomes unstable when reflected light from an optical fiber cable, a connector, or the like returns to the semiconductor laser or the like. An optical isolator is used to prevent this instability.

A Bi-substituted rare earth iron garnet having a large Faraday rotation is grown by an LPE method, a flux method, or the like, and is used as an optical isolator in the near infrared region. In particular, since the growth by the LPE method is excellent in productivity, it is possible to supply an optical isolator material at low cost.

[0004] Among the Bi-substituted garnets, GdBi-based garnets and TbBi-based garnets are
The applied magnetic field is as small as about 1000 Oe or less, and there is a feature that a small permanent magnet can be used for the applied magnetic field.

Incidentally, it is desirable that the optical isolator has a higher transmittance for light in the forward direction and a lower transmittance for light in the reverse direction. Therefore, the garnet material used therein is required to have a large Faraday rotation coefficient of about 1000 deg / cm or more and a high light transmittance, that is, a low light absorption loss of 0.3 dB or less. Furthermore, high-performance optical isolators include:
A garnet material having an insertion loss of 0.1 dB or less is required.

The liquid phase growth of the Bi-substituted garnet used for such an optical isolator material is performed as follows. Lead oxide (PbO) in a platinum crucible,
Bismuth oxide (Bi ₂ O ₃ ) and boron oxide (B ₂ O ₃ ) are used as flux components, and garnet growing components [gadolinium oxide (Gd ₂ O ₃ ), terbium oxide (Tb ₂ O ₃ ), ferric oxide (Fe) ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ),
Gallium oxide (Ga ₂ O ₃ ) or the like] at about 900 to 1000 ° C.
After dissolving in the above to prepare a growth solution, the temperature is lowered to a supersaturated state. The garnet substrate is immersed in the solution, and a garnet crystal thick film is grown while rotating for a long time.

[0007]

As described above, when the Bi-substituted garnet is deposited and grown by the LPE method, it is very important to control the concentration of the supersaturated component, and the composition of the grown garnet changes depending on the temperature and the flow state of the solution. However, the material properties will also change. In the LPE method, the crystal growth state is managed by controlling the temperature of the solution, controlling the number of rotations of the substrate, and the like.

However, the composition of the deposited garnet has not yet been sufficiently controlled. Therefore, variations in characteristics occur, and the light transmittance is reduced, so that the insertion loss is increased.

[0009] Therefore, a technical problem of the present invention is to remove Bi ₂ O ₃ from a solution containing a large amount of Bi ₂ O ₃ component by the LPE method.
When depositing a Bi-substituted garnet containing ₂ O ₃ as a main component, in a composition that greatly affects material properties, the main constituent components of the garnet further contain an appropriate amount of elements and are subjected to heat treatment to reduce insertion loss. To provide a Bi-substituted garnet material and a method for producing the same.

[0010]

The present invention is characterized in that lead oxide is contained in a GdBi-based garnet single crystal or a TbBi-based garnet single crystal in a range of 0.05 to 1.5 wt% in terms of PbO. Bismuth-substituted garnet material.

The present invention also provides a method for forming a GdBi-based garnet single crystal or TbB on a garnet substrate by a liquid phase growth method.
In a method for producing a bismuth-substituted garnet material for growing an i-based garnet single crystal, lead oxide is contained in a GdBi-based garnet single crystal or a TbBi-based garnet single crystal.
A method for producing a bismuth-substituted garnet material, characterized in that it is contained in the range of 0.05 to 1.5 wt% in terms of bO.

Further, the present invention provides a heat treatment temperature of 1000-1000.
A method for producing a bismuth-substituted garnet material as described above, wherein the temperature is in the range of 1150 ° C.

Further, the present invention is the above-mentioned or the method for producing a bismuth-substituted garnet material, wherein the oxygen concentration of the atmosphere in the heat treatment is in the range of 20 to 100 vol%.

The present invention provides a Bi-substituted garnet material,
By containing 0.05 to 1.5 wt% of lead oxide in terms of PbO, the insertion loss of the garnet material can be reduced. This is presumably because the energy state in the crystal lattice is stabilized. PbO content of 0.0
The reason for setting the content to 5 to 1.5 wt% is that the effect of stabilizing the energy state becomes remarkable at 0.05 wt% or more, and the insertion loss is remarkably reduced. This is because instability occurs and the insertion loss increases significantly.

The heat treatment temperature is mainly related to the homogenization of the composition of the garnet crystal and the Pb ionization of PbO.
It is presumed that limiting the heat treatment temperature is effective in improving the regularity of the crystal lattice and improving the stability of the energy state due to ionization balance. Heat treatment temperature 10
The reason for setting the temperature in the range of 00 to 1150 ° C. is that at 1000 ° C. or higher, the regularity of the crystal lattice and the stability of the energy state are improved, and the insertion loss is significantly reduced.
If the temperature exceeds 50 ° C., it can be determined that the generation of Pb ⁺ becomes remarkable, the stability of the energy state decreases, and the insertion loss increases remarkably.

In the present invention, the oxygen concentration in the atmosphere during the heat treatment is limited. However, the heat treatment atmosphere is effective in reducing the vacancies of oxygen and suppressing the transition from Pb ²⁺ to Pb ⁺ . It is presumed that there is. The reason why the oxygen concentration in the heat treatment atmosphere is set in the range of 20 to 100 vol% is that 20 vol%
This is because the insertion loss is significantly reduced as described above.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS High purity powder such as Gd ₂ O ₃ is used as a raw material, and PbO—Bi ₂ O ₃ —B is used as a flux.
After growing a GdBi-based garnet thick film containing a predetermined amount of PbO on a Nd ₃ Ga ₅ O ₁₂ substrate by an LPE method using a ₂ O ₃ system, the substrate is removed, and heat treatment is performed under predetermined conditions. Thus, the Bi-substituted garnet material according to the first embodiment of the present invention is obtained.

Using a high purity powder such as Tb ₂ O ₃ as a raw material and a PbO—Bi ₂ O ₃ —B ₂ O ₃ system as a flux, (GdCa) ₃ (GaMg
Zr) TbB containing a predetermined amount of PbO on ₅ O ₁₂ substrate
After growing the i-based garnet thick film, the substrate is removed and heat-treated under predetermined conditions to obtain the Bi-substituted garnet material of the second embodiment of the present invention.

[0019]

Embodiments of the present invention will be described below.

Example 1 High-purity (99.9% or more) gadolinium oxide (Gd ₂ O ₃ ), ferric oxide (Fe)
₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), lead oxide (P
bO) and boron oxide (B ₂ O ₃ ) powder as raw materials, PbO concentration in the melt was changed from 0 to 60 wt%, and lead oxide was contained by the LPE method (GdBi).
₃ (FeGaAl) ₅ O ₁₂ garnet was grown. The substrate used at this time was Nd ₃ Ga ₅ O ₁₂ single crystal, the lattice constant was 15.509 angstroms, and the orientation of the substrate was <111>. Approximately 500μm thick as growing crystal
The main composition of Gd _2.1 Bi _0.9 Fe _4.6 Ga _0.2 O ₁₂
Eleven GdBi-based garnet thick film single crystals containing 0 to 2.97 wt% of O were obtained.

Next, after removing the substrate of this sample, 50
It was kept at 1100 ° C. for 20 hours in an atmosphere with an oxygen concentration of vol% and heat-treated. Next, both surfaces of these GdBi-based garnet samples were polished to obtain a sample plate having a thickness of about 350 μm. The composition of the GdBi-based garnet thick film described above was obtained as an average value of a total of 20 points by performing EPMA analysis on each side of each of these samples at 10 points.

Next, after subjecting these sample plates to a non-reflective coating treatment with a SiO ₂ film, a magnetic field of about 1 kOe is applied,
The insertion loss at a wavelength of 1.3 μm was measured. In FIG.
4 shows the relationship between the PbO content of a GdBi-based garnet thick film crystal and insertion loss. From FIG. 1, the PbO content is 0.05 to
It can be seen that the insertion loss tends to decrease in the range of 1.5 wt%.

(Embodiment 2) In the same manner as in Embodiment 1, Pb
GdBi-based garnet thick film crystal containing 0.8 wt% of O is grown, and after removing the substrate, 1 g is grown in a 50 vol% oxygen atmosphere.
After heat treatment at 000-1200 ° C for 20 hours, polishing
The insertion loss was measured. The result is shown in FIG. FIG. 2 shows that when the heat treatment temperature is in the range of 1000 to 1150 ° C., the insertion loss is reduced as compared with the non-heat treatment.

(Embodiment 3) In the same manner as in Embodiment 1, Pb
GdBi-based garnet thick film crystal containing 0.8 wt% of O is grown, and after removing the substrate, the oxygen concentration is reduced to 0 to 100 vol%.
After heat treatment at 1100 ° C. for 20 hours in a nitrogen mixed atmosphere changed to above, polishing was performed, and insertion loss was measured. The result is shown in FIG. From FIG. 3, the oxygen concentration of the atmosphere is 20 to
At 100 vol%, it can be seen that the insertion loss is reduced.

Example 4 Terbium oxide (Tb ₂ O ₃ ) and ferric oxide (Fe) of high purity (99.9% or more)
₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), lead oxide (Pb
O) and boron oxide (B ₂ O ₃ ) powder as raw materials, and a (GdCa) ₃ (GaMgZr) ₅ O ₁₂ substrate (lattice constant 12.490 Å, substrate orientation <11
1)) In the same manner as in Example 1, PbO was set to 0, 0.
A TbBi-based garnet thick film (about 500 μm thick) having a composition of 8 wt% Tb _2.1 Bi _0.9 Fe ₅ O ₁₂ was grown.

Next, in the same manner as in Example 1, after removing the substrate, heat treatment, polishing, and measurement were performed. Table 1 shows the measurement results of the insertion loss.

[0027]

As shown in Table 1, the insertion loss of the TbBi-based garnet thick film was as follows for a heat-treated sample with a PbO content of 0.8 wt%.
It can be seen that it has been reduced.

It should be noted that the present invention is not limited to the compositions and wavelengths of the above-described embodiments, but rather the GdB manufactured by the LPE method.
The present invention can be applied to i-based garnet and TbBi-based garnet, and the effect of the present invention can be expected as long as the measurement wavelength does not correspond to the absorption spectrum of garnet.

The garnet shown in the above embodiment has a Faraday rotation coefficient at a wavelength of 1.3 μm of about 1100 d.
eg / cm or more, and the saturation magnetization is about 200 G for GdBi-based garnet and about 600 to 8 for TbBi-based garnet.
00G, which indicates characteristics that can be used as a Faraday rotation element, for example, an optical isolator.

[0031]

As described above, according to the present invention, it is possible to provide a Bi-substituted garnet material having improved crystallinity, which greatly affects material properties, and reduced insertion loss, and a method for producing the same. Was.

[Brief description of the drawings]

FIG. 1. PbO in a GdBi-based garnet thick film crystal
The figure which shows the relationship between content and insertion loss.

FIG. 2 is a diagram showing a relationship between a heat treatment temperature and an insertion loss in a GdBi-based garnet thick film crystal.

FIG. 3 is a diagram showing a relationship between oxygen concentration in a heat treatment atmosphere and insertion loss in a GdBi-based garnet thick film crystal.

Claims (4)

[Claims] 1. A GdBi-based garnet single crystal or TbB
Lead oxide in the i-based garnet single crystal was calculated to be 0.1% in terms of PbO.
A bismuth-substituted garnet material, which is contained in the range of 0.5 to 1.5 wt%. 2. A method for producing a bismuth-substituted garnet material for growing a GdBi-based garnet single crystal or a TbBi-based garnet single crystal on a garnet substrate by a liquid phase growth method, comprising the steps of:
Lead oxide in the i-based garnet single crystal was calculated to be 0.1% in terms of PbO.
A method for producing a bismuth-substituted garnet material, wherein the content is in the range of from 0.5 to 1.5 wt%. 3. The method for producing a bismuth-substituted garnet material according to claim 2, wherein the heat treatment temperature is in the range of 1000 to 1150 ° C. 4. The oxygen concentration of the atmosphere in the heat treatment is 20.
The method for producing a bismuth-substituted garnet material according to claim 2 or 3, wherein the content is in the range of 100 vol% to 100 vol%.