JPH0656468A - Laser glass - Google Patents

Abstract

PURPOSE:To provide a fluoride-based laser glass capable of emitting the 1.5mum band luminescence of Er<+3> in high efficiency by 0.8mum band excitation. CONSTITUTION:This fluoride-based laser glass contains at least Zr and/or Hf and Al ions as constituent, and, besides, Er ion and Eu and/or P ion as the sensitizer for Er ion and, F ion as constituent. The proportions of the respective ions in the total cations are, in terms of cationic %, an follows : Er ion, 0.2-15%; Eu ion, 0-5%; P ion, 0-5%; and Eu ion plus P ion, 0.1-10%. In case P ion is contained as a cation, O ion is also contained as an anion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a laser glass,
In particular, it relates to a fluoride laser glass having an oscillation wavelength in the 1.5 μm band.

[0002]

2. Description of the Related Art A 1.5 μm band oscillation laser is widely used as a light source for long-distance optical communication because it is in the minimum loss wavelength range of silica glass. This wavelength range is also used as a sensor light source such as a rangefinder light source by taking advantage of the high threshold of the laser light intensity that causes damage to the human eye and thus has high safety. . More recently, Er
It is clarified that a doped optical fiber can directly amplify propagating 1.5 μm band light and has excellent characteristics, and it is attracting attention as a technique capable of greatly extending a non-repeatered transmission distance. Er-doped glass has been conventionally used as a laser glass for oscillation or amplification in the 1.5 μm band. This utilizes the luminescence transition of Er ³⁺ from ⁴ I _13/2 to ⁴ I _15/2 (ground level).

Incidentally, silicate glass, phosphate glass, fluorophosphate glass, heavy metal fluoride glass, borate glass and the like are used for the laser glass matrix. However, with borate glass, Er ³⁺
The phonon energy coupled to is large, ⁴ I _13/2 to ⁴
Since the probability of non-radiation to I _15/2 increases, it is not very practical in terms of efficiency.

On the other hand, silicate glass is a fiber material for long-distance optical transmission, and its practical application has been widely studied. In this case, Er ³⁺ doped Ge, P co-doped silicate glass or the like is used, and by direct pumping with 1.48 μm LD, high gain (30 dB or more) and low noise amplification characteristics for 1.5 μm band signal light. Has been obtained.

In general, the 1.5 μm band emission spectrum from an Er ³⁺ -doped glass matrix has a narrow half-width in silicate glass and phosphate glass, and conversely in fluoride glass, particularly heavy metal fluoride glass. wide. This is for example the case of W. J. Miniscalc
o, J. Lightwave Tech, Vol. 9,
No. 2, (1991) 234 to 250, since rare earth ions can substitute only network elements in fluoride glass, the influence of the crystal field is weaker than in the case of oxide glass, and the Stark level is better than Stark splitting. It is explained that the shape of the emission band is determined by the inter-transition and the symmetry of the spectrum becomes higher.

By the way, a so-called wavelength multiplex waveguide technique has been developed in which a plurality of signal lights are propagated in the same transmission line using a 1.5 μm band laser. This technique is extremely important for high-density information processing and large capacity in optical communication, and is also important for simultaneously obtaining information of multiple objects in remote sensing such as distance measurement.

Er ^{3+ 4} I _13/2 → ⁴ I _{15/2 in} 1.5 μm band
When the transition is used for this wavelength-division-multiplexed waveguide, it is preferable that the half width of the emission band of 1.5 μm is wider than the narrow one as a property of the glass matrix. That is, a fluoride glass having a wide half-width of emission band has a wider bandwidth of high gain than a silicate glass or a phosphate glass having a narrow half-width, which is advantageous for amplification and multiplexing of oscillation wavelengths. Become.

In fact, ZrF ₄ --BaF ₂ --LaF ₃ --A
lF ₃ in -NaF (hereinafter referred ZBLAN) glass-based optical fiber, high-gain bandwidth of more than 30dB as 1.55μm band optical amplification characteristics of the Er ³⁺ is reported to reach 3.5 nm (Fukasaku et al, 1992 IEICE Spring Conference C-308 Proceedings Separate Volume 4, P.4-35
0). On the other hand, in the silica glass fiber, the high gain bandwidth is about 10 nm.

[0009]

As described above, a fiber made of fluoride, which is a matrix glass of Er ³⁺ having a wide high gain bandwidth, usually has an excitation light source of ⁴ I _{13/2 at} an emission level of ⁴ I _13/2 . An LD of 0.48 μm or 0.8 μm is used. However, 1.48 μm LD is InGaAsP / In
It is composed of P composition and has a high energy confinement effect of Ga.
Since it is smaller than the AlAs / GaAs composition, it is difficult to increase the output. Therefore, since a plurality of LDs are used for excitation at the same time, there are problems that the size of the excitation source becomes large and the cost becomes high.

On the other hand, 0.8 μm GaAlAs / GaAs
The excitation using the LD utilizes the transition from ⁴ I _15/2 to ⁴ I _9/2 , and as shown in FIG. 3, ⁴ I _9/2 → ⁴ I
_11/2 → ⁴ through a two-stage non-radiative transition of I _13/2 ⁴ I _13/2 → ⁴
In the radiation transition process of I _15/2 , 1.53 μm light is emitted. However, as shown in FIG. 3, 0.8 μm band excitation has strong excitation level absorption, and 0.8 μm optical absorption of the ground level is generally weaker than excitation level absorption. For this reason, 0.
Although an 8 μm band LD can easily obtain a large output and is inexpensive, Er ³⁺ of 1.
It has been conventionally pointed out that the amplification gain of 5 μm band light is small.

An object of the present invention is to provide a fluoride laser glass capable of highly efficiently emitting Er ^{3+ in} the 1.5 μm band by excitation in the 0.8 μm band.

[0012]

FIG. 4 shows a 0.8 μm band LD excitation fluorescence spectrum when AZF (fluoroalumino zirconate) glass which is a conventional fluoride glass is doped with an appropriate amount of Er ³⁺ . . In FIG. 4A, E ₁ , E
_Two emission bands of ₂ and E ₃ are shown, and their origins are as shown in FIG. 4 (B).

That is, E which corresponds to the transition of ⁴ I _11/2 → ⁴ I _15/2 rather than the desired 1.53 μm fluorescence (E ₃ ).
₂ is much stronger. This result is due to the low efficiency of Er ³⁺ 1.5 μm band emission when excited by 0.8 μm band LD.
In addition to the excitation level absorption explained in FIG. 3, there is a point that the ⁴ I _11/2 level has a long lifetime.

The laser glass of the present invention capable of highly efficiently emitting in the 1.5 μm band emits at least Zr and / or Hf ions and Al ions as cations constituting the glass, and as an anion constituting the glass. A fluoride glass containing F ions, further containing Er ions as cations constituting the glass and Eu ions and / or P ions as a sensitizer for Er ions, and each of the total cations The ratio of ions is expressed in Cationic%, Er ions are 0.2 to 15%, Eu ions are 0 to
5%, P ions are 0 to 5%, the total amount of Eu ions and P ions is 0.1 to 10%, and when P ions are included as cations, O ions are also included as anions. It is a laser glass.

The present invention will be described in detail below. FIG. 5 is a diagram for explaining the principle of the present invention. When Eu ions are co-activated with Er ions, which are the luminescence center of the fluoride glass, energy transition due to resonance transfer occurs from the adjacent Er ions to the Eu ions as shown in FIG. 5 (A). That is, the excitation electron wave staying at the ⁴ I _11/2 level of Er ³⁺ is Eu
³⁺ results of quantum mechanical exchange interaction with, giving energy to _{^{Eu 3+, 4 I 11/2 → 4}} I of Er ³⁺ in phonons is not involved
_Excitation of Eu ³⁺ corresponding to _13/2 , ie ⁷ F _{0 of} Eu ³⁺
→ A transition to ⁷ F ₅ occurs. The excited Eu ³⁺ relaxes its energy through a non-radiative process.

On the other hand, since the maximum phonon energy in the fluoride glass matrix is 500 to 600 cm ^-1 as shown in FIG. 4B, the ⁴ I _13/2 level of Er ³⁺ and the Eu ^{3+ level} . Energy difference ΔE (= 150 between ⁷ F ₆ levels)
0 cm ^-1) are required multi-phonon processes to fill and therefore Eu from ⁴ I _13/2 level closely spaced Er ^3+
Almost no relaxation of energy involved in phonon to the ⁷ F ₆ level of ³⁺ occurs. Therefore, the 1.53 μm emission efficiency does not decrease due to the ⁴ I _13/2 → ⁴ I _15/2 transition.

As a result, by co-activating Eu ³⁺ , Er ³⁺
Increased non-radiative transition process from the ⁴ I _11/2 level of, ⁴ I _11/2
Level life is reduced. Therefore, ⁴ I _11/2 → ⁴ I
Emission transition of _15/2 (E ₂ emission band in FIG. 4) and ⁴ I _11/2 →
Excitation level absorption of ⁴ F _3/2 (Fig. 3) is suppressed.

However, the transition process from the ⁴ I _11/2 level is
Since they are competing processes with each other, it is more desirable to add a device to make the non-radiative transition to the emission level ⁴ I _13/2 dominant.

This is the co-activation of P ions shown in FIG. 5 (B). That is, P is added to the fluoride glass matrix.
Inclusion of ions increases the phonon energy of the fluoride glass matrix. The phonon energy is sufficiently smaller than the energy difference ΔE (= 1500 cm ^-1 ) between ⁴ I _{13/2 of} Er ³⁺ and ⁷ F ₆ of Eu ³⁺ (<1
000 cm ^-1 ) so that the content of P ions is 5 ca
Adjust to t,% or less.

By adding P ions, the above-mentioned Er ^3+
4 I _11/2 → ⁴ I _13/2 non-radiative transition probability increases. That is, since this non-radiative transition is a multiphonon process, if the relaxation rate is W _MP , the observed lifetime τ of the ⁴ I _11/2 level is 1 / τ = 1 / A ₃₁ + 1 / A ₃₂ + W _MP + 1 / P _ESA + 1 / P _RT Here, A ₃₁ and A ₃₂ are respectively
Probability of natural light emission to ⁴ I _15/2 and ⁴ I _13/2 , and P _ESA
Is the excitation level absorption probability to ⁴ F _3/2 , and P _RT is the resonance transfer probability to Eu ³⁺ .

Increasing W _MP by adding P ions reduces the importance of other competing processes to the extent that ⁴ I
The energy storage on _13/2 can be increased. Even if the phonon energy of the fluoride glass matrix is increased by the addition of P ions, ⁴ I _13/2 → ⁴ I of Er ³⁺
_Since the energy difference of _15/2 is sufficiently larger than ⁴ I _11/2 → ⁴ I _13/2 , it is possible to avoid affecting the transition probability of 1.53 μm radiation.

P ion is effective whether contained in the raw material as P ₂ O ₅ or PO ₃ ^3- . Since the Eu ³⁺ co-activation and the P ion co-activation have different effects, either one of them may be co-activated, or both may be co-activated.

In the present invention, the concentration of each cation in the fluoride glass matrix is limited to the predetermined range as described above for the following reason. Er ³⁺ concentration at emission center [E
r ³⁺ ] is 0.2 cationic% (hereinafter c) for all cations in order to obtain a sufficiently high gain in optical amplification in the 1.5 μm band.
at. %) Or more, and 15 cat. %
If it exceeds, the concentration quenching is remarkable, so 0.2 to 15 ca
t. Limited to%. More preferably, [Er ³⁺ ] is 0.
5-12 cat. %.

Eu ions and P ions are E as described above.
It has a sensitizing effect on the 1.5 μm band emission of r ³⁺ . However, when [Eu ³⁺ ] and / or [P ⁵⁺ ] is 0.1 ca
t. %, The sensitizing effect is small, and 10 cat. %
Beyond that, the non-radiative transition becomes prominent in Er ^{3+ 4} I _13/2 → ⁴ I _15/2 . Therefore, [Eu ³⁺ ] and / or [P ⁵⁺ ] is 0.1-10 cat. %, More preferably 0.1 to 7 cat. %.

When Eu ions are used alone as a sensitizer, [Eu ³⁺ ] is 5 cat. When it exceeds%, Er ³⁺ is 1.
The 5 μm band emission is deactivated, while 0.1 cat. %, The sensitizing effect is small, so [Eu ³⁺ ] is 0.1 to 5 ca.
t. % Is preferable. Also, [Eu ³⁺ ] is ³ ca
t. If it exceeds%, the sensitizing effect will be saturated, so [E
u ³⁺ ] is 0.1 to ³ cat. % Is particularly preferred. Also P
When an ion is used alone as a sensitizer, [P ⁵⁺ ] is 5
cat. % By weight, the non-radiative transition probability from ⁴ I _13/2 to ⁴ I _15/2 is increased, the emission intensity is lowered, it is difficult enough dehydration of the glass matrix, whereas 0.1c
at. %, The sensitizing effect is small, so [P ⁵⁺ ] is 0.1 to 5 cat. % Is preferable. Also, [P ⁵⁺ ] is 4 cat. %, The effect is saturated, so [P ⁵⁺ ] is 0.1 to 4 cat. % Is particularly preferred.

The laser glass of the present invention contains Zr and / or Hf ions and Al ions as other essential glass constituent cations. The proportion of these cations in the total cations is not critical, but Zr and / R are 0.5 to 70 cat. %, Al ions are 2-45 ca
t. % Is preferable.

The laser glass of the present invention may contain cations other than the above-mentioned cations. As these cations, Y, La, Mg, Ca, S
Examples include cations such as r, Ba, Na, Li, Pb, Cd, Zn and In ions.

In the laser glass of the present invention, the anions basically consist of F ions, but the cations are P ions.
When it contains ions, O (oxygen) ions are also included as anions. The proportion of O ions in all the anions is preferably 6% or less in terms of anionic% (hereinafter referred to as an.%). The reason is 6an. If it exceeds%, the glass becomes unstable and a homogeneous glass cannot be obtained.

Although a part of the F ions can be replaced with Cl ions, the ratio of Cl ions to the content of F ions and Cl ions is an. %, If it exceeds 6%, the glass becomes unstable and a homogeneous glass cannot be obtained. % Or less is preferable.

The fluoride glass which is the matrix of the laser glass of the present invention includes Zr-Ba-La-Al.
-ZBLAN glass, which is Na-based fluoride glass; Zr
-AZF glass which is an Al type fluoride glass is mentioned.

As the former ZBLAN glass, zirconium fluoride 52 to 69 mol% and barium fluoride 10 to 24 m described in Japanese Patent Publication No. 61-24349 are used.
ol%, sodium fluoride 9-25 mol, lanthanum fluoride 1-7 mol% and aluminum fluoride 2-5 mo
Specific examples include those containing 1%.

As the latter AZF glass, AlF _{3 of} 20 to 45 mol% and ZrF described in JP-A-62-175039 and JP-B-4-37015 are used.
₄ and / or HfF ₄ 0.5 to 25 mol%, CaF ₂
0-42 mol%, SrF ₂ O-25 mol%, BaF
_{2 0~25mol%,} and fluoride glass containing total amount 20 to 70 mol% of CaF ₂ and SrF ₂ and BaF _2, a part of the F ion in the fluoride glass, glass concrete was replaced with Cl ions Take as an example. Furthermore, Electronics Letters 26 , N
o. It is also possible to use the AZF glass described in 22, 18, 37 (1990).

[0033]

EXAMPLES The present invention will now be described in more detail based on examples. Zr as a raw material for fluoride matrix
F ₄ , AlF ₃ , YF ₃ , MgF ₂ , CaF ₂ , SrF
₂ , BaF ₂ , NaF and NaCl were prepared, and HfF ₄ and LaF ₃ were further prepared as added heavy metal raw materials. Also,
ErF ₃ was prepared as the raw material for the emission center Er ³⁺ , and EuF ₃ and Ba (PO ₃ ) ₂ were prepared as the sensitizer raw materials of the present invention. These raw material components were weighed so as to have a predetermined molar concentration as shown in A-1 to A-5 of Table 1 and A-6 to A10 of Table 2, and sufficiently mixed to obtain a glass raw material composition. It was

[0034]

[Table 1]

[0035]

[Table 2] Tables 3 and 4 are glass raw material mixtures A-1 to A-1 in which the composition (mol%) of the raw material components is shown in Tables 1 and 2.
For 0, the ratio of each cation is expressed as Cationic% (ca
t. %), And the ratio of each anion is anionic% (an.
%).

[0036]

[Table 3]

[0037]

[Table 4] 40 g of each of the glass raw material compositions A-1 to A-10 was taken and placed in a carbon crucible, and then the carbon crucible was placed in a heating furnace, and 2 liters / mi of argon gas was placed in the furnace.
The temperature was raised while supplying n and NF ₃ gas at a rate of 50 ml / min. The sample was kept at 900 to 950 ° C. for 2 hours as it was, then rapidly cooled to 340 to 360 ° C., and then gradually cooled to around room temperature to obtain a disc-shaped fluoride glass sample having a diameter of 30 mm and a thickness of 10 mm.

For comparison with the fluoride glass of the present invention, comparative fluoride glass samples B-1 and B-2 which were not doped with Eu and P ions were prepared in the same manner as above. Table 5 shows the composition of the raw material components (mol%)
Table 6 shows the proportion of each cation (cat.%) And the proportion of each anion (an.%).

[0039]

[Table 5]

[0040]

[Table 6] Each glass sample prepared as described above is
The columnar glass having a size of 12 × 3 mm was processed, and each of the six columnar surfaces was mirror-polished. 0.8 μm for each sample
The peak emission intensity of the fluorescence in the 1.5 μm band that was excited by the oscillation LD and radiated was measured and compared under the same conditions. The laser light from the LD passed through the chopper and was applied to the sample as intermittent light, and the fluorescence was condensed by the lens and then dispersed. Each of the separated wavelength components was input to a Ge detector that was calibrated in advance for photoelectric conversion, and the signal voltage was amplified and recorded by a lock-in amplifier synchronized with the chopper.

FIG. 1 shows that [Er ³⁺ ] is 1.0 cat. %, And the [Eu ³⁺ ] dependence of the emission intensity of the 1.5 μm band of the sample co-activated with Eu ³⁺ as the sensitizer is shown. Figure 1
Is a comparative sample B-1 which is not doped with Eu ^3+.
The emission intensity of is also shown.

As shown in the figure, samples A-1 to A
-4 has a matrix composition of Zr-Al-based fluoride glass, so-called AZF glass.
The matrix composition of -5 is so-called ZBLAN glass.

According to FIG. 1, in the case of AZF glass, 1 ca
t. It is shown that the emission intensity is increased about 16-fold by the co-activation of Eu ³⁺ in%. Further, ZBLAN glass is less likely to cause saturation of this effect, and is 2.5 cat. The emission intensity is increased about 20 times by the co-activation of Eu of 10%.

Compared to the sample of FIG. 1, [Er ³⁺ ] is 10
Although the concentration quenching is seen in the sample A-6 which is doubled in height,
Even so, it was observed that the emission intensity in the 1.5 μm band increased about 2.5 times as compared with the comparative sample B-2 in which no Eu was co-activated.

Next, the emission intensities of Samples A-7 to A-10 in which the matrix composition was almost the same as that of Comparative Sample B-1 and P ions were co-activated instead of Eu were compared with Comparative Sample B
FIG. 2 compares the emission intensities of −1.

The emission intensity in the 1.5 μm band increases with the concentration of P ions, and [P ⁵⁺ ] 2.0 cat. It can be seen that the addition of 5% increases about 5 times as compared with the case of no addition. In the data range of FIG. 2, still no brightness saturation is observed.

Separately, ⁴ I of Er ³⁺ by P ion co-activation
Taking the data of _11/2 → ⁴ I _13/2 transition efficiency increase and extrapolating from that data, the peak value of the data in Fig. 2 is [P ⁵⁺ ].
4 cat. %, And the luminescence intensity at that time is estimated to be about 10 times that of the case of no addition.

Eu ³⁺ was added to 1 cat. %, P ⁵⁺ at 2 cat.
% Co-activated [Er ³⁺ ] = 1cat. % -Doped ZBLA
It was observed that the N glass has a luminescence intensity of 1.5 μm band increased by about 18 times as compared with the case where no Eu and P ions were added.

The present invention has been described above with reference to the examples.
The present invention is not limited to these. For example,
It is easy for those skilled in the art to make various improvements, combinations, and changes.

[0050]

As described above, according to the present invention,
In a fluoride glass suitable for wavelength division multiplexing optical transmission, Er
³⁺ 1.5μm band emission intensity can be significantly increased compared to the conventional. As a result, there is provided a fluoride laser glass exhibiting extremely useful characteristics as a 1.5 μm band optical amplifier for optical communication and a 1.5 μm band oscillation laser glass for distance measurement.

[Brief description of drawings]

FIG. 1 is data showing a sensitizing effect of Eu ions according to an example.

FIG. 2 is data showing the sensitizing effect of P ions according to the example.

FIG. 3 is a diagram showing a transition process of 0.8 μm LD-excited Er ³⁺ 1.5 μm band emission.

FIG. 4 is a diagram showing fluorescence of 0.8 μm LD-excited Er ³⁺ -doped fluoride glass.

FIG. 5 is a principle explanatory diagram relating to a sensitizing action of Eu ions or P ions according to the present invention.

Claims (3)

[Claims] 1. A glass containing at least Zr and / or Hf ions and Al ions as cations,
A fluoride glass containing F ions as anions constituting the glass, further comprising Er ions as cations constituting the glass and Eu ions and / or P ions as a sensitizer for Er ions. The ratio of each ion in the total cations is represented by Cationic%, Er ion is 0.2 to 15%, Eu ion is 0 to 5%, P ion is 0 to 5%, and Eu ion and P ion are Total amount is 0.1
Laser glass characterized in that it is 10%, and when it contains P ions as cations, it also contains O ions as anions. 2. The laser glass according to claim 1, which contains only Eu ions as a sensitizer for Er ions, and the ratio of Eu ions in the total cations is 0.1 to 5% in terms of Cationic%. . 3. The laser glass according to claim 1, which contains only P ions as a sensitizer for Er ions, and the ratio of P ions in the total cations is 0.1 to 5% in terms of Cationic%. .