JPS59116199A - Liquid phase epitaxial growth method of garnet - Google Patents

Abstract

PURPOSE:To grow a garnet film satisfying a prescribed performance index by specifying the range of growth temps. and further setting the supercooling temp. to the specified temp. or below in the epitaxial growth of the garnet film from a molten liquid consisting essentially of PBO. CONSTITUTION:When a garnet film for optical element is grown by a liquid phase epitaxial growth method from a molten liquid consisting essentially of PBO, the growth temp. and the super-cooling temp. are set to about 920-993 deg.C and to >= about 10 deg.C, respectively. A desired garnet film, e.g. Gd0.2Y2.8Fe5O12, Y3Fe5O12 is obtd., which satisfies alpha<0.6cm<-> eight absorbance and 75deg/dB performance index. Kinds of ions of rare earth elements replaced in the garnet are Eu, Tb, Nb or the like. In this manner, the reproducible garnet film can be obtd., which satisfies the prescribed performance index.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for growing a garnet liquid phase epitaxial film for optical elements. More specifically, the present invention relates to a growing method for reducing optical absorption loss.

The use of thick and thin garnet liquid-phase epitaxial films as non-reciprocal elements such as isolators and laser oscillation elements was reported in Lecture No. 882 of the 1982 IEICE General Conference and Proceedings on the Thirteenth.・Conference on Solid State Devices; Japanese Journal on Applied Fixtures (Proceedings of
the 13theonference on 5ol
id 8tate 1) evices.

Tokyo, 1981; Japanese J
of Applied Physics)
An attempt is made in Volume 21, Appendix 21-1, page 409.

One of the important material properties when used in these devices is optical absorption loss. It is desirable that the light absorption loss is small, such as #1. As a guideline, when using garnet liquid phase epitaxial Jll as an optical isolator, the figure of merit, which is the ratio of the Faraday rotation coefficient of garnet to the optical absorption loss, is required to be 75 deg/(I 8 or more. In this case, the incident polarization plane is rotated by 45 degrees, so the loss when light passes through the element must be 0.6 dl (or less. For example, when YIG is used as the material, its faraday Since the rotation coefficient is 215 deg/cn, the element length required to rotate the incident polarization plane by 45 degrees is 0.21 (
Im going to be. In other words, the optical absorption loss is 0.6 dB.
/m number must be below. The incident light intensity IO is
The light absorption coefficient α of YIG that satisfies (11 75 de g/former 3) when traveling by (m) in the element must therefore be α<0.66 -1. .

The required value of α varies depending on the material's 7Araday rotation coefficient, but the Faraday rotation coefficient of 19
When using Gd:YIG of 0 deg/cIn as an optical isolator material, it is necessary that α<0.60/L 1.

In this case, the light absorption coefficient of the garnet liquid phase epitaxial film for optical elements is often large, and it has been difficult to reduce the figure of merit of the material to a value below 75 deg/dB. The purpose of the present invention is to provide a garnet liquid phase epitaxial film for optical elements with a light absorption coefficient of α<0,6.
The objective is to provide conditions for growing a garnet film that will produce a garnet film.

The present inventor has experimentally discovered that there is a causal relationship between the growth conditions of the garnet liquid phase epitaxial family and the light absorption coefficient, and has thus accomplished the invention.

The principle of the present invention based on the experimental results will be described below.

1 in Figure 1. 2 and 3 use melts with liquidus temperatures of 930°C, 988°C, and 1003°C, respectively, to determine the supersaturation temperature (defined as the difference between the growth temperature and the liquidus temperature).
Wavelength 1.3μm when growing garnet film by changing
This shows the absorption coefficient of light. The light absorption coefficient increases exponentially as the film growth temperature decreases, that is, as the supercooling temperature increases. Figure 2 shows that the supercooling temperature Δ was obtained by preparing melts whose liquidus temperatures were continuously changed and growing a garnet film from these melts by changing the supercooling temperature.
Wavelength 1.3μm when T is 0.10 and 20℃
It shows the absorption coefficient of light. In the figure, 4-5 and 6 correspond to Δ'I'=O110 and 20°C. Note that the absorption coefficient at 8T=0°C is the value obtained by extrapolating the measured value of the absorption coefficient at a finite supercooling temperature to ΔT=0.

As is clear from this diagram, absorption is determined by two factors. One is absorption that occurs in the state of ΔT=0, and this absorption is determined equilibria once the liquidus temperature of the melt is determined. The other is absorption caused by kinetic effects as the film grows.

As is clear from Figure 2, the absorption at ΔT=0, that is, is determined equilibria, and the absorption is mostly at the liquidus temperature.
There is an area called window++. Approximately 930-10
Absorption is minimum in the range of 00°C. Corresponding to this
-, when ΔT=10℃, the absorption coefficient is α≦Q, 5cI
m' is a region where the film growth temperature is 915-995℃
Exist within the range of

That is, in the method for growing a garnet liquid phase epitaxial film for optical elements from a melt containing PbO as a main component, the supercooling temperature is 10°C or less, and the garnet film is grown at a temperature of 920°C or less. 993
This is a growth method characterized by setting the supercooling temperature to 10°C or less.

The present invention will be explained in more detail below using examples.

Example 1 M! of the composition shown in Table 1! Gd O,2Y using ll solution
2.8F'esOt2 Garnet liquid phase epitaxy A
/ film was grown. The liquidus temperature for this ml is 1003℃, and the absorption coefficient at a wavelength of 1.3μm extrapolated to the liquidus temperature (supercooling yjA degrees Δ1゛=0℃) is α2Q, lOInoi
'Met.

In addition, the 0.55 absorption coefficient at the supercooling temperature Δ'I' = tO"C (growth temperature is 993°C) is α = 0.55 -1, and the Faraday rotation coefficient of the material of Sea 1 is 190d.
eg/dB, it was possible to satisfy the figure of merit of 75deg/dB. However, when ΔT=15° C., the performance index of α-1,95Ga-1, ab, and 75deg/dB could not be satisfied.

Example 2 Using a melt having the composition shown in Table 1, Y a l' e s
(J, 26-Garnet) A 7ff1.411 epitaxial film was grown. The liquidus temperature of this melt is 988℃, and the wavelength 1.3μ extrapolated to the liquidus temperature (supercooling temperature Δ1゛=0℃)
The absorption coefficient of m was α20.1t)ht”. Also, the supercooling temperature IAeΔT=1 +)°C (i.e., the growth vMA
The number of absorbed threads at 978°C is α”-0.35
tim” and the rotation coefficient of this material is 2.
Since it is 15deg/-, the index is 75deg/
I was able to satisfy dB.

In addition, when the supercooling temperature is 20℃, α=0.80
in, and could not satisfy the figure of merit of 75 deg/dB.

Example 3 Using a melt having the composition shown in Table 1, Ga 0.2 Y 2
．． A 8F e 5012 garnet liquid phase epitaxial film was grown. The liquidus temperature of this melt was 952°C, and the absorption coefficient at a wavelength of 1.3 μm extrapolated to the liquidus temperature (supercooling temperature Δ'v - 0°C) was α = 0.15K-1. . Also, supercooling temperature ΔT = 10℃ (growth temperature 942℃)
The absorption coefficient is α"0.40 GB", and since the Faraday rotation coefficient of this material is 190 deg/Qe, the figure of merit of 75 deg/dB can be satisfied.

However, when ΔT-15℃, α20.65℃
1n'', failing to satisfy the figure of merit of 75 deg/dB.

Example 4 Using a melt having the composition shown in Table 1, Gd O02Y 2,
An 8F e 5012 garnet phase epitaxial film was grown.

The liquidus temperature of this melt was 930°C, and the absorption coefficient at a wavelength of 1.3 μm extrapolated to the liquidus temperature (supercooling temperature Δ'P-0°C) was α=0.1. Also, the supercooling temperature ΔT
The absorption coefficient at = to ℃ (920 ℃ as the growth temperature) is α2Q, 5m', and since the Faraday rotation coefficient of this material is 190 deg/ah, the figure of merit is 75d.
I was able to satisfy eg/dB. In addition, when ΔT-11'C is used, α=3.55m'', and the figure of merit is 75deg.
/dB could not be satisfied.

However, in the case of Comparative Examples 1 and 2 shown below, α<0.6o that satisfies the figure of merit of 75 deg/dB.
It was not possible to obtain an absorption coefficient of n.

Comparative Example 1 Gdo, zY2. sF
e 5012 garnet liquid phase epitaxial film was grown.

The liquidus temperature of this melt was 1005°C, and the absorption coefficient at a wavelength of 1.3 μm extrapolated to the liquidus temperature (supercooling temperature Δ′r−0°C) was α”0.15C1n 1 . Supercooling temperature Δ″r=xo℃ ('R growth temperature is 995℃
), and since the Faraday rotation coefficient of this material was 190 deg/cm, the figure of merit of 75 deg/dB could not be satisfied.

Comparative Example 2 Using a melt having the composition shown in Table 1, Udo, 2 Y2.
A B Fe 5012 garnet liquid phase epitaxial film was grown.

The liquidus temperature of this melt was 928°C, and the absorption coefficient at a wavelength of 1.3 μm extrapolated to the liquidus temperature (supercooling temperature Δ'I' = Q°C) was α = 0.15. , supercooling temperature Δ
The absorption coefficient at T = 10°C (918°C as a growth temperature) is α20.68a@'', and the 7-Alade rotation coefficient of this material is 190 deg/e, so the figure of merit is 75.
deg/dB could not be satisfied.

In addition, the type of rare earth ion to be replaced with garnet is Gd.
In addition, when changing to Hu, 'rb, Nd, etc., the effect was similar, and a figure of merit of 75 deg/dB or more was obtained.

As explained above, by using the present invention, a garnet liquid phase epitaxial film for optical elements having a figure of merit of 75 deg/dB or more can be obtained with good reproducibility.

[Brief explanation of drawings]

Figure 1 shows the relationship between film growth temperature and light absorption at 1.3 μm; Diagram showing the relationship between 11-Figure 1

Claims (1)

[Claims] 1) In a method for growing a garnet liquid phase epitaxial film for optical elements from #ag as a main component of k'bOt, garnet whose Qif value is a supercooling temperature of 10°C or less. A method for growing epitaxial films. 2) Growth temperature of garnet liquid phase epitaxial gland is 92
The garnet liquid phase epitaxial growth method according to claim 1, wherein the temperature is 0 to 993°C.