JPH05319855A - Fluoride glass for blue light emission - Google Patents

Abstract

PURPOSE:To increase electron density and to enhance blue light emission intensi ty by coactivating fluoride glass with Tm<3+> as a light emission center and Yb<3+> as a sensitizer. CONSTITUTION:Starting material for fluoride glass consisting of Al$3, ZrF4, YF3, CaF2, MgF2, SrF2, BaF2 and NaF is prepd., TmF3 and YbF3 are added to the starting material and they are melted by heating and rapidly cooled. The resulting glass is heated to the glass transition temp. and slowly cooled to obtain fluoride glass for emission of blue light excited by laser dioxide light having 0.97mum wavelength. This glass is fluoride glass coactivated with 0.01-0.1 cationic % Tm<3+> as a light emission center and 11-20 cationic % Yb<3+> as a sensitizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue light emitting fluoride glass, and more particularly to a 0.97 .mu.m laser diode excited blue light emitting fluoride glass suitable for photoexcitation lasers and displays.

[0002]

2. Description of the Related Art In recent years, laser diodes (LDs) and LD-pumped solid-state lasers have been developed which are compact and lightweight and have excellent mass productivity with the improvement of laser technology. These are widely used in consumer devices in addition to light sources for optical communication. For example, a laser printer, an optical disk, or a POS light source. Since the sensitivity of the optical sensor of these devices improves rapidly as the wavelength becomes shorter, it is desired to shorten the wavelength of the laser.

However, it is difficult for an LD to obtain light on the shorter wavelength side than red, due to material restrictions. Most recently blue LD
Was announced at the research stage, but its luminous efficiency is extremely low, and its practical application is still far away. On the other hand, in the LD pumped solid state laser,
Blue light emission has not been obtained yet by direct excitation.

If a compact, lightweight and long-life all-solid-state blue light-emitting laser can be obtained, compact lasers of the three primary colors will be available along with the conventionally developed red and green lasers, which can be used for projection type displays.

As a blue laser, a high output laser is obtained as a gas laser, and a frequency multiplication method for generating a second harmonic component (SHG) of an LD using a nonlinear optical material has been put into practical use. ..

However, since the gas laser is large and has a short life, on the other hand, the combination of the SHG material and the LD has a poor coherence of LD radiation, so that it cannot be said that the blue laser has high integrity.

Therefore, there is an attempt to develop a compact all-solid-state blue laser with an LD-excited glass laser.

For example, Tm ³⁺ activated quartz glass is
Reported that blue emission was obtained by excitation with 06 μm LD (Han
na et al, Optics Commun, 1
8 (2), (1990) 189) and 0.65 μm L
Report on blue emission when excited by D (Tabe et al., Proceedings of 3rd glass lecture for optoelectronics (1992)
14) etc.

[0009] These are obtained by exciting up from the ground level ³ H ₆ to the ¹ G ₄ level by utilizing the up-transition of Tm ^{3+ by} the excitation light multi-step absorption and obtaining blue light emitted by radiation relaxation. Is.

In addition to this, Hanna et al. Tm ³⁺ , Yb ³⁺
The co-activated silica glass fiber was excited by a 0.97 μm LD to obtain a blue emission of 0.47 μm. This is 0.
This is a method in which 97 μm light is first absorbed by the Yb ³⁺ sensitizer, and the energy is resonantly absorbed from there to Tm ³⁺ .

[0011]

The blue light-emitting glass that has been reported so far has been reported to have the above-mentioned Tm ³⁺ of ¹ G ₄ to ³ H.
_It uses the transition to ₆ (ground level). However, when Tm ³⁺ is solely activated, multistage photoabsorption transition is required for LD excitation, so that the excitation density of the ¹ G ₄ level is low and the blue emission intensity is very low.

Meanwhile Hanna et al Tm ^3+, in the active silica fibers with Yb ³⁺ both concentrations of Tm ³⁺ [Tm ^3+] is 0.15 wt%, the concentration of Yb ³⁺ [Yb ^3+] is 1 .5 wt
%, And the concentration of the sensitizer Yb ³⁺ is not sufficiently higher than that of [Tm ³⁺ ], so that the density excited by the ¹ G ₄ level is not so high and only weak blue light emission is obtained.

When only the radiation as weak as the above-mentioned conventional example can be obtained, it is difficult to overcome the internal loss and perform optical amplification, and a blue laser cannot be expected.

An object of the present invention is to provide a Tm ³⁺ , Yb ³⁺ co-activated LD-excited blue light-emitting glass capable of obtaining strong blue light emission capable of laser oscillation.

[0015]

According to the research conducted by the present inventors, LD excitation of Tm ³⁺ , Yb ³⁺ co-activated glass was performed, and anti-Stokes type blue light emission was made to the extent that laser oscillation was possible. It was found that optimizing the concentrations of the luminescent center and the sensitizer and selecting the glass material of the matrix are extremely important for strengthening.

In the blue light emitting glass of the present invention, fluoride glass is used as the base glass. Fluoride glass is a generic term for fluoride glass containing fluorine as a constituent element (network former) of a network structure. Preferred fluoride glasses include fluoroalumino zirconate glass (Japanese Patent Laid-Open No. 62-275039 and Japanese Patent Laid-Open No. 17433), and fluorophosphate glass (Japanese Patent Publication No.
4-6047, Japanese Patent Publication No. 58-14379,
Japanese Patent Publication No. 61-14093), Fluoralumino hafnate glass (Japanese Patent Laid-Open No. 62-275039) and ZBLAN glass (Zr, Ba, La, Al, Na).
A glass whose main component is fluoride. The same applies below).

The glass for blue light emission of the present invention is obtained by co-activating Tm ^3+, which is the emission center, and Yb ^3+, which is the sensitizer, on the above-mentioned base glass, and is excited by 0.97 μm LD. The taping concentration is 0.01 to 0.1 cat for the emission center Tm ^3+.
%, And the sensitizer Yb ³⁺ is preferably 11 to 20 cat%.

[Tm ³⁺ ] is outside the above range and [Yb ³⁺ ]
This is because the emission intensity becomes extremely weak in the concentration range of <11cat%, and the matrix glass devitrifies when [Yb ^{3 +} ]> 20cat%.

[0019]

FUNCTION FIG. 3 is a diagram for explaining the inter-level transition in which blue emission is obtained when Tm ³⁺ , Yb ³⁺ co-activated fluoride glass is excited by 0.97 μm LD.

As described above, in the present invention, [Yb ³⁺ ] is 100 to 1000 times higher than [Tm ³⁺ ]. For this reason, the 0.97 μm LD excitation light is first absorbed by Yb ³⁺ and used to transit electrons from the ground level ² F _7/2 to the excitation level ² F _5/2 . The energy of the ² F _5/2 level of Yb ³⁺ is ³ H of Tm ³⁺ , which is in the closest position by resonance transfer.
Transition to ₅ levels.

The energy of the ³ H ₅ level is temporarily relaxed to the ³ H ₄ level. This transition is non-radiative, but [Tm
³⁺ ] is so low that the fluorescence lifetime of the ³ H ₄ level is 18 m.
sec is extremely long, and the radiative transition probability from the ³ H ₄ level to the lower level is small.

Electrons in the ³ H ₄ level absorb the 0.97 μm laser beam and are excited to the ³ F ₃ level. Thermal relaxation from this level to the ³ F ₄ level is performed once, but the fluorescence lifetime of the ³ F ₄ level is also very long, 2 msec, and the downward radiation transition probability is small.

Therefore, the electrons of the ³ F ₄ level are again reduced to 0.
It absorbs 97 μm laser light and is excited to the ¹ G ₄ level. Then, 0.475 μm blue light is obtained by the radiative transition from the ¹ G ₄ level to the ³ H ₆ ground level of Tm ³⁺ .

In the above description, Tm ^{3+ 3} H ₄ →
^{Both the 3} F ₃ and ³ F ₄ → ¹ G ₄ transitions are 0.97 μm LD
Caused by light absorption. In addition to this, a mechanism by transfer of resonance energy from ² F _{5/2 of} Yb ³⁺ is also conceivable. Figure 3
This is also shown in.

On the other hand, FIG. 4 shows 0.68 μm of various Tm ³⁺ doped glasses (fluoride glass, fluorophosphate glass, germanium oxide salt glass, gallium oxide glass, aluminum oxide glass, silicon oxide glass). LD
0.79 μm light ( ³ F ₄ → ³ H ₆
(Corresponding to the transition of the above) and the intensity of Tm ³⁺ concentration [Tm ³⁺ ] dependence.

FIG. 4 shows that the fluoride glass emits the strongest fluorescence. This means that the fluoride glass has the highest density of Tm ^{3+ 3} F ₄ level.

That is, when fluoride glass is used as the host material of Tm ³⁺ , the highest level density of ³ F ₄ → ¹ G ₄ , which is the final stage of the upward transition for blue emission, is highest. ³
If the density of F ₄ is high, the electron density excited by ¹ G ₄ per unit time also becomes high, so that the strongest blue emission can be obtained.

Hereinafter, the present invention will be described in more detail based on examples.

[0029]

EXAMPLE FIG. 1 shows a case where a fluoroalumino zirconate (AZF) glass, which is a kind of fluoride glass, is used as a base material [Y
b3 ⁺ ] is fixed and [Tm ³⁺ ] is changed, 0.97μ
The change in blue emission intensity of mLD excitation is shown. [Yb ³⁺ ] is Yb
^In order to maximize the ³⁺ sensitizing effect, 19+ near the solid solubility limit
Cat% doped.

AlF as a fluoride powder raw material₃25.
1cat%, ZrF_FourTo 12.8cat%, YF₃1
1.1cat%, CaF₂15.4cat%, MgF
₂3.7cat%, SrF₃13.6cat%, B
aF₂Of 12.6cat%, NaF of 5.6cat%,
YbF was added to the powder obtained by weighing and mixing.₃19c
at%, TmF₃Xcat% (0.005%<x<
0.3%).

This powder was added to a platinum crucible (internal volume 100c).
It was filled in c) and kept at 950 ° C. for 45 minutes in a nitrogen stream. Through this step, the raw material glass is sufficiently melted. Then, it was rapidly cooled to room temperature in a nitrogen stream.

Next, the obtained glass was put into a carbon crucible, heated to a glass transition point of 398 ° C., held for 20 minutes, and then slowly cooled to around room temperature at a rate of 10 ° C./hr,
Tm ³⁺ , Yb ³⁺ co-activated AZF glass is obtained.

Excitation of AZF glass was performed with a 0.97 μm emission GaAlAs LD with an output of 50 mW.
The 0.475 μm fluorescence intensity from the glass is R22 after spectroscopy.
It was measured through 28 Photomaru.

[Tm ³⁺ ] of the data in FIG. 1 is 0.06 ca.
It shows that the intensity of 0.475 μm blue light becomes the strongest at t% (0.1 wt%). Fluorescence intensity is x <
In the area of 0.03cat%, it sharply decreases and x <0.01
Cat% is not practical. Also, x> 0.06ca
A decrease in fluorescence intensity is also seen in the t% region. This is because Y increases from the ³ F ₄ level of Tm ³⁺ as [Tm ³⁺ ] increases.
It is considered that this is because the reverse energy transfer of b ^{3+ to} the ² F _5/2 level is increased. This is because, as described above, the density of the ³ F ₄ level of Tm ³⁺ is highest in the fluoride glass matrix.

Therefore, considering practicality, [Tm
³⁺ ] is preferably in the range of 0.01 to 0.1 cat%.

Next, [Tm ³⁺ ] was fixed at 0.06 cat%, which has the highest blue light intensity, and the change in blue light intensity was investigated using [Yb ³⁺ ] as a parameter.

As the base glass, the same AZF glass as in the above example was used, and Tm ³⁺ , Yb ³⁺ co-activated fluoride glass was obtained by the same manufacturing process as above.

[Yb ³⁺ ] was changed within the range of 10 to 20 cat%. The result is shown in FIG.

The blue light intensity of 0.49 μm is [Yb ³⁺ ]
In the experimental range, it increases monotonically. But,
In the region of [Yb ³⁺ ] <11cat%, the emission intensity is sharply weakened, and when [Yb ^{3 +} ]> 20cat%, devitrification occurs on the glass surface.

Therefore, preferred [Yb ³⁺ ] is 11 to
It is in the range of 20 cat%.

In the above examples, the fluoride glass matrix was AZF glass. However, as a result of the examination by the present inventors, similar results were obtained with other fluoride glasses such as fluoralumino hafnate glass and ZBLAN glass. That is, Tm co-activated with sensitizer Yb ^{3+
The 3+} 0.97 μm excitation and 0.475 μm blue emission are enhanced in all fluoride glasses containing fluorine as a constituent element of the network structure.

The blue emission intensity of 0.475 μm is orders of magnitude higher than the fluorescence intensity obtained from the blue emission glass which has been conventionally reported.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to this. For example, various improvements in the composition and manufacturing method of fluoride glass,
It will be apparent to those skilled in the art that changes, combinations and the like are possible.

[0044]

As described above, according to the present invention,
It is possible to obtain a glass that emits blue light having an intensity far exceeding that of the conventional example. The fluorescence intensity is large enough to cause laser oscillation. Therefore, a blue light-emitting glass laser can be put to practical use by combining the currently used nonlinear optical effect material and LD.

[Brief description of drawings]

FIG. 1 is a 0.97 μm LD excitation 0.475 μ of the embodiment.
Data showing the relationship between fluorescence intensity and [Tm ³⁺ ] in m blue light-emitting glass.

FIG. 2 shows 0.97 μm LD excitation 0.475μ of the example.
m Data showing the relationship between fluorescence intensity and [Yb ³⁺ ] in blue light-emitting glass.

FIG. 3 is an explanatory diagram of excitation and transition processes of Tm ³⁺ , Yb ³⁺ co-activated fluoride glass.

Shows the [Tm ^3+] dependent ³ F ₄ → ³ H ₆ transition emission intensity of FIG. 4 Tm ³⁺ doped various glass.

Claims (2)

[Claims] 1. A fluorinated glass in which Tm ^{3+ of the} luminescent center and Yb ^{3+ of the} sensitizer are co-activated.
Fluoride glass for 7 μm laser diode light excitation blue emission. 2. The Tm ³⁺ concentration [Tm ³⁺ ] is 0.01.
~ 0.1 Cationic percent (cat%), said Y
The fluoride glass for blue light emission according to claim 1, wherein the concentration of b ³⁺ [Yb ³⁺ ] is 11 to 20 cat%.