JPH0648768A - Laser glass emitting light at 0.8mum wavelength - Google Patents

Abstract

PURPOSE:To provide laser glass emitting light at 0.8mum wavelength and useful for optical communication and further a high-output laser and having high luminous intensity. CONSTITUTION:This fluoride laser glass comprises 7-19mol% Yb<3+> and 0.1-1.0mol% Tm<3+>. The laser glass contains, e.g. Zr, Hf, Al, Mg, Ca, Sr, Ba or Na as cations other than the Yb and Tm and at least fluorine as an anion. A laser beam at 0.8mum wavelength can be emitted by irradiating the laser glass with a semiconductor laser beam at 0.98mum wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Yb ³⁺ and Tm ^{3 +} -doped fluoride laser glass which emits 0.8 μm laser light.

[0002]

2. Description of the Related Art Recently, in order to utilize an inexpensive semiconductor laser and a silicon sensor, light around 0.8 .mu.m has received much attention as light for short-distance communication. Currently, research is being conducted on 0.85 μm Er ³⁺ -doped glass fiber laser by upconversion. However, this laser had low up-conversion efficiency and did not give satisfactory results.

On the other hand, 0.65 μm to 0.69 μm and 0.
Tm having strong absorption in the band of 78 μm to 0.8 μm
^{When 3+} is excited by a semiconductor laser of 0.68 μm or 0.79 μm, its energy is ³ F _{4 which has} a long fluorescence lifetime.
Therefore, they simultaneously emit light in the 0.8 to 0.82 μm band. In addition, Tm ³⁺ is calculated from the Judd-Ofelt theory.
The probability of radiation transfer from ³ F ₄ to ³ H ₆ is large, and the blunting ratio is 90% or more, so that it is expected as a laser-activated ion with high emission efficiency.

However, a 0.8 μm laser glass using Tm ³⁺ as an activating ion has not been known so far. Therefore, the present inventors previously developed a Tm ³⁺ -doped laser glass and applied for a patent [Japanese Patent Application No. 4-148523].
issue〕.

Apart from optical communication, development of high-power lasers for nuclear fusion and processing is also in progress. The currently known high-power laser is the Nd ³⁺ laser. However, there are problems such that the emission wavelength of Nd ³⁺ is 1.06 μ, which is a relatively long wavelength, the fluorescence lifetime is short, and the accumulated energy is not large.

The Tm ³⁺ -doped laser glass is excellent in that it has a short emission wavelength of 0.8 μm, an emission intensity higher than that of the Nd ³⁺ laser, and a long fluorescence lifetime. However, there is a demand for a laser having a higher output of 0.8 μm.

Therefore, an object of the present invention is to provide a Tm-doped laser glass which emits a 0.8 μm laser beam in which the emission intensity of the Tm ³⁺ -doped laser glass is further increased.

[0008]

The present invention provides Yb ³⁺ of 7 to 7
It relates to a fluoride laser glass containing 19 mol% and Tm ³⁺ of 0.1 to 1.0 mol%.

Fluoride glass is used as the medium glass in the glass of the present invention. Tm ³⁺ is added to various glasses such as silicate, germanate, fluorophosphate, aluminate, and fluoride glass, and the emission intensity and fluorescence lifetime at a wavelength of 0.8 μm are measured. The addition amount of Tm ³⁺ that represents the maximum intensity was determined, and the quantum efficiency of light emission of each glass was calculated. As a result, they have found that fluoride glass is the most suitable medium. It is speculated that this is because the phonon energy of the fluoride glass is the smallest.

Next, the amounts of Yb ³⁺ and Tm ³⁺ added will be described.

[0011] is excited only Tm ³⁺ from the ground state of the doped fluoride glass excited with a semiconductor laser of 0.68μ Tm ^{3+ (3} H ₆₎ to the ³ F ₃ level, then the underlying
Since ³ F ₄ is very small energy gap between the levels is thermally relaxed most of the energy from ³ F ₃ to ³ F _4. Then, radiative transition from ³ F ₄ to ³ H ₆ ground level causes emission of 0.8 μm. On the other hand, the present inventors have found that a stronger 0.8 μm laser emission can be obtained by adding Yb ³⁺ as a sensitizing ion in addition to Tm ³⁺ .

FIG. 1 shows an energy level diagram of a fluoride glass obtained by adding Yb ³⁺ as a sensitizing ion to Tm ³⁺ . When Yb ³⁺ is excited with 0.98 LD, Yb ³⁺
From ² F _7/2 (ground state) to ² F _5/2 , and Yb
Energy is transferred from ^{3+ 2} F _5/2 to Tm ^{3+ 3} H ₅ . Then Tm ³⁺ ions ³ H ₅ level position of the Tm ³⁺ is ³ H ₄
Thermally relax up to. Next, from ³ H _{4 of} Tm ³⁺ , 1.03 μm emission energy of Yb ³⁺ is further received to cause up-conversion to ³ F ₂ (ESA: upper level absorption). From ³ F ₂ of Tm ³⁺ after relaxation thermally to ³ F ₄
Radiation transition from ³ F ₄ to ³ H ₆ , which is the ground state, causes emission of 0.8 μm.

Further, as shown in FIG. 4, when the amount of Yb ³⁺ is fixed and the amount of Tm ³⁺ is increased, the fluorescence lifetime of Yb ³⁺ is reduced. This is due to the addition of Tm ³⁺ to Yb ³⁺ to T
Indicates that energy is transferred to m ³⁺ , that is, Tm ³⁺ emission is sensitized by Yb ^3+.

The amount of Tm ³⁺ added was 0.
Emission of 0.8 μm is particularly strong in the range of 1 to 1.0 mol%.
On the other hand, the amount of Yb ³⁺ added is in the range of 7 to 19 mol% as shown in FIG. 3, and the emission intensity at 0.8 μm is high. In addition, Yb ³⁺
Is more than 19 mol%, the glass may devitrify, so the upper limit is appropriately set to 19 mol%. Yb ³⁺ is particularly preferably 10 to 19 mol%.

Further, the laser glass of the present invention is, for example, as a cation constituting the glass, for example, Zr ion, Hf ion, Al ion, Mg ion, Ca ion, Sr ion, Ba ion, Yb ion, Tm. Ion, and the ratio of each ion in the cation is expressed in mol%, and the total amount of Zr ion and Hf ion is 1 to 25%,
20 to 45% of Al ions, 20 to 70% of total amount of Mg ions, Ca ions, Sr ions and Ba ions, Yb
Ions are 7 to 19%, Tm ions are 0.1 to 1.0%, and at least F ions are contained as anions constituting the glass, and the proportion of F ions in the anions is 80 in terms of mol%. ~ 100% fluoride glass.

As cations other than Yb ion and Tm ion, Zr ion, Hf ion, Al ion, Mg
Ions, Ca ions, Sra ions, and Ba ions can be used. Of these, Zr ions, Hf ions, and Al ions are components that form the glass skeleton,
These amounts are preferable because they increase the stability of the glass against crystallization within the above limits. Further, Mg ion, Ca ion, Sr ion, and Ba ion are glass modifying components, and their amounts are preferably within the above-mentioned limits because they enhance the stability against crystallization of glass and improve the chemical durability.

Further, alkali metal ions such as Li ion, Na ion, K ion and Cs ion, Y ion, S
c ion, Gd ion, Zn ion, Pb ion, Cd
Ions, In ions, Ga ions and the like also increase the stability of the glass against crystallization and can be used as the cation component of the glass. Alkali metal ions reduce the chemical durability of the glass when the amount is large, so 20 mol% or less is preferable, and the amount of Y ions, Sc ions, Gd ions, Zn ions, Pb ions, and Cd ions is large. On the contrary, since it deteriorates the stability of glass against crystallization, it is preferably 20 mol% or less. Similarly, Sc ions, In ions, and Ga ions are preferably 5 mol% or less.

Next, the anion will be described. F ions are the basic component of glass. Further, by substituting with F ions, Cl ions, Br ions, and I ions can be contained. The amount is 20% for Cl ion, B
If the content of each of r ion and I ion exceeds 10%, the glass tends to crystallize and the chemical durability is deteriorated. Therefore, Cl ion is 0 to 20 mol%, Br ion is 0 to 1
0 mol% and I ion are limited to 0 to 10 mol%. If the amount of F ions is less than 80%, it becomes difficult to obtain a glass having high stability against crystallization.
The total amount of r ions and I ions is limited to 20 mol% or less.

In the laser glass of the present invention, raw materials such as high-purity fluoride and / or chloride are mixed and prepared so as to have a predetermined composition, and melted at 950 to 1000 ° C. in an argon atmosphere, and then a glass melt is prepared. It can be obtained by slow cooling.

The laser glass of the present invention has a wavelength of about 0.9.
By irradiating with a semiconductor laser of 8 μm, it is possible to obtain about 0.1
It is possible to generate a laser beam of 8 μm.

[0021]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 As starting materials, ZrF ₄ was 11.6 mol%, AlF ₃ was 22.9 mol%, MgF ₂ was 3.4 mol%, CaF ₂ was 14 mol%, and SrF ₂ was 12.4 mol%. %, BaF ₂ is 1
1.5 mol%, NaF 2.4 mol%, NaCl 2.
7 mol%, YbF ₃ 19 mol%, TmF ₃ 0.3 mol%
Were weighed and mixed to obtain a batch.

Then, the obtained batch is put in a crucible made of carbon and placed in a heating furnace, and the inside of the furnace is heated to melt at 980 ° C. for 1 hour under an argon gas atmosphere to melt a glass melt. Got Then, the obtained glass melt was gradually cooled in the air while being put in the crucible to solidify the glass in the crucible, and cooled to room temperature in a slow cooling furnace to obtain zircoaluminofluoride glass (AZF).

Example 2 Zircoaluminum was prepared in the same manner as in Example 1 except that the raw materials were weighed and mixed so that the amount of TmF ₃ was 0.1, 0.6, 0.9 or 1.2 mol%. A nofluoride glass was obtained. The obtained glass and the glass of Example 1 were each 980n.
The emission intensity at 0.8 μm was determined by pumping with an m diode laser. The result is shown in FIG. From this result, it was found that the emission intensity of 0.8 μm was increased in the range of Tm ion concentration of 0.1 to 1.0 mol%.

Example 3 A zircoaluminofluoride glass was obtained in the same manner as in Example 1 except that the raw materials were weighed and mixed so that the amount of YbF ₃ was 7, 10, 13 or 16 mol%. The obtained glass and the glass of Example 1 were each pumped with a 980 nm diode laser to determine the emission intensity at 0.8 μm. The result is shown in FIG.

From these results, the Yb ion concentration was 7 mol%.
From the above, it was found that the emission intensity at 0.8 μm was high, especially at 10 to 19 mol%.

Example 4 The raw materials were weighed and mixed so that the amount of TmF ₃ was 0.1, 0.3, 0.5, 1.0 or 2.0 mol%, and the amount of YbF ₃ was 10 mol%. In the same manner as in Example 1, zircoaluminofluoride glass was obtained. The fluorescence lifetime of Yb ³⁺ was measured for each of the obtained glasses. The results are shown in Fig. 4.

From FIG. 4, in the glass containing Yb ³⁺ and Tm ³⁺ , when Tm ³⁺ was increased at a constant Yb ³⁺ of 10 mol%, the fluorescence lifetime of Yb ³⁺ was decreased and Tm ^{3+ was} added. Shows that the energy is transferred from Yb ³⁺ to Tm ³⁺ .
That is, it shows that the emission of Tm ³⁺ is sensitized by Yb ³⁺ .

[0029]

According to the present invention, an inexpensive semiconductor laser is used as an excitation light source to obtain a Tm ³⁺ -doped fluoride laser glass having a long fluorescence lifetime and a large emission efficiency of 0.8 μm, which has a large quantum efficiency. .

[Brief description of drawings]

FIG. 1 is an energy level diagram of Yb ³⁺ and Tm ³⁺ .

FIG. 2 shows the relationship between the Tm ion amount and the emission intensity when the Yb ion amount is fixed and the Tm ion amount is changed.

FIG. 3 shows the relationship between the Yb ion amount and the emission intensity when the Tb ion amount is fixed and the Yb ion amount is changed.

FIG. 4 shows the relationship between the amount of Tm ions and the fluorescence lifetime of Yb ³⁺ when the amount of Tb ions is changed while keeping the amount of Yb ions constant.

Claims (3)

[Claims] 1. A Yb ³⁺ and 7-19 mol% and Tm ³⁺ 0.1 to 1.0 mole% containing fluorides laser glasses. 2. Zr is used as a cation constituting glass.
Ions, Hf ions, Al ions, Mg ions, Ca ions, Sr ions, Ba ions, Yb ions, and Tm ions, and the ratio of each ion in the cations is mol%.
The total amount of Zr ions and Hf ions is 1 to 25 on the display.
%, Al ions are 20 to 45%, and the total amount of Mg ions, Ca ions, Sra ions, and Ba ions is 20 to 70.
%, Yb ions 7 to 19%, Tm ions 0.1 to
A fluoride laser glass, which is 1.0%, contains at least F ions as anions constituting the glass, and the proportion of F ions in the anions is 80 to 100% in terms of mol%. 3. The laser glass according to claim 1 or 2 is irradiated with a semiconductor laser having a wavelength of about 0.98 μm to 0.8.
A method of generating a μm laser beam.