JP2908680B2 - Upconversion laser material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in the field of optical memory, optical measurement, and optical information processing using laser light, particularly visible laser light, and is capable of obtaining laser light having a wavelength shorter than the excitation wavelength. Related to up-conversion laser materials.

[0002]

2. Description of the Related Art Up-conversion laser oscillation of bulk glass has not been confirmed so far, and up-conversion laser oscillation has been confirmed in a single mode glass fiber which can effectively utilize light confinement in a glass material. For example, a ZrF ₄ -based fluoride glass fiber doped with Tm ³⁺ is used, and a Kr ⁺ laser 647.1 is used.
Example in which an up-conversion laser oscillation of 455 nm was obtained at a temperature of 77 K by simultaneous excitation of two wavelengths of 67 nm and 676.4 nm [J. Y. Allain, et al. ,
Electron. Lett. 26,168 (199
0)], an example in which an up-conversion laser oscillation of 550 nm was obtained at room temperature by exciting a Kr ⁺ laser at 647.1 nm using a ZrF ₄ -based fluoride glass fiber doped with Ho ³⁺ [J. Y. Allain, et al. ,
Electron. Lett. 26, 262 (199
0)], using a ZrF ₄ -based fluoride glass fiber doped with Pr ³⁺ , by simultaneous excitation of Ti: sapphire laser at 1.01 μm and 850 nm at two wavelengths of 491 nm and 520 nm.
Example in which up-conversion laser oscillation of 620 nm and 620 nm was obtained [R. G. FIG. Smart, et al. , E
electron. Lett. 27, 1307 (199
1)].

[0003] However, these upconversion laser oscillations have been confirmed only in the case of a ZrF ₄ -based fluoride glass that can be made into a fiber. In a method utilizing optical confinement by a fiber shape, a more efficient upconversion laser is used. There is a problem in that it is difficult to use InF ₃ -based fluoride glass, chloride glass, bromide glass, and mixed halide glass, which are expected to cause laser oscillation, and Kr ⁺ laser or Ti: sapphire laser is used as an excitation light source. As described above, a laser which has very good coherence and can obtain an output of several hundred mW or more is required.

[0004]

SUMMARY OF THE INVENTION According to the present invention, optical confinement can be easily realized even in a glass composition in which fiber conversion is difficult and upconversion laser oscillation has not been confirmed so far, and Kr can be obtained around room temperature. ^An object of the present invention is to provide an up-conversion laser material that oscillates an up-conversion laser even in a compact semiconductor laser of about 150 mW as well as a ⁺ laser or Ti: sapphire laser.

[0005]

According to the present invention, there is provided a fluoride glass, a chloride glass, or a mixture of at least one of erbium, holmium, praseodymium, thulium, neodymium and cerium as rare earth element ions.
Bromide glass and chlorinated fluoride glass are disclosed in Japanese Patent Application No. Hei.
This can be achieved by forming a microsphere glass by the method described in No. 0392, polishing or the like.

When the microsphere glass is irradiated with a laser beam oscillated with light energy in the light absorption region of the rare earth element ions added as active ions, the active ions are changed from the first energy level to the first energy level. Higher second
From the second energy level or from a third energy level lower than the second energy level and higher than the first energy level.
Due to the energy transfer between the excited ions as shown in (a) or the excited state absorption (multi-step excitation) as shown in FIG. 1B, the energy is further shifted to the fourth energy level higher than the second energy level. Being excited to emit light from the fourth energy level or a fifth energy level lower than the fourth energy level and higher than the second energy level to the first energy level, The so-called up-conversion emission, which emits light having a wavelength shorter than the wavelength of the incident light, occurs inside the microsphere, and the up-conversion emission enters the interface between the inside and the outside of the microsphere at an angle larger than the critical angle. Light repeats total reflection at the interface. When the light that repeats the total reflection and rotates in the microsphere has the same phase, the light resonates, and the microsphere itself functions as a resonator, and the fourth energy level or the fifth energy level is used. By causing an inversion distribution between the first energy level and the fourth energy level.
Energy level or the fifth energy level and the first energy level
Oscillates a laser beam having a wavelength corresponding to the energy difference from the energy level.

In the present invention, the amount of active ions added is 50 to
A range of 5000 ppm is suitable, more preferably 3 ppm.
It is 00 to 1500 ppm. 50 active ions added
If less than ppm, the absorption efficiency of the excitation laser light is poor, and up-conversion laser oscillation is unlikely to occur,
When the amount of rare earth element ions added is 5000 ppm or more, concentration quenching occurs due to the interaction between rare earth element ions, and upconversion laser oscillation hardly occurs. In addition, luminous efficiency can be improved by co-adding Yb ³⁺ or the like as a sensitizing ion separately from the rare earth element ion.

[0008] The refractive index of the microsphere glass is preferably 1.3 or more in the laser oscillation wavelength range, and when it is less than 1.3, light cannot be effectively confined, and up-conversion laser oscillation hardly occurs.

[0009] The size of the microsphere glass is not particularly limited, but in consideration of handling, a range of 50 to 2000 µm is suitable, and a range of 200 to 1000 µm is more preferable. Since the leakage of light due to the diffraction effect becomes relatively smaller as the microsphere size increases, the Q value of the microsphere resonator increases, and upconversion laser oscillation occurs at a low threshold, but the Q value increases. Since many resonance modes are present and the spectrum of the oscillation line becomes complicated, it is preferable to determine the size of the microsphere according to the purpose of use.

The fine glass material is preferably a fluoride glass, a chloride glass, a bromide glass, or a chlorofluoride glass. In particular, in consideration of chemical durability and mechanical strength, AlF ₃ based, InF ₃ system and ZrF ₄ based fluoride glass are more preferable. In consideration of the oscillation efficiency, a glass having a smaller phonon energy is preferable, but a glass having a material intrinsic absorption at the excitation light wavelength and the up-conversion laser oscillation wavelength is not preferable because the emission efficiency is reduced.

[0011]

The up-conversion laser glass is formed into a microsphere shape to confine light, and the microsphere itself is used as a resonator, so that the Q value of the resonator can be increased. Up-conversion laser oscillation can be performed even with a glass composition that did not oscillate unless fiberized.

[0012]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

FIG. 2 shows an embodiment of an up-conversion microsphere laser according to the present invention, wherein 1 is an excitation light source, 2 is a condenser lens, 3 is a rare earth-doped microsphere glass, 4 is an elliptical reflector, 5 is a fiber and 6 is a condenser lens. The excitation light source is a semiconductor laser, and the diameter of the rare earth-doped microsphere is 300 μm.
45 mol% In to which 700 ppm Er ³⁺ is added
F ₃ -30 mol% PbF ₂ -25 mol% ZnF ₂ fluoride glass.
No. 0392. .

[0014] The laser beam of 800nm from the excitation light source 1 is condensed by a lens 2, by irradiating as shown at 7 in Figure 3 to the end of the rare earth-doped microspheres 3, ⁴ of the Er ³⁺ I _15/2
→ ⁴ I _9/2 excitation and ⁴ I _11/2 → ⁴ F by ⁴ F _7/2 excitation
_{That 3/2} → ⁴ I _15/2 laser beam 550nm due to transition was obtained was confirmed from the existence of the oscillation spectrum and thresholds (100 mW).

In this embodiment, InF ₃ doped with Er ³⁺ is used.
It was used -PbF ₂ -ZnF ₂ based fluoride glass microspheres, 65mol% ZrF ₄ -35mo added with Tm ³⁺
It was also confirmed that laser light of 480 nm was obtained by dye laser excitation (650 nm) using 1% BaF ₂ fluoride microsphere glass.

Further, as a laser medium, ZrF ₄ -B
Using aCl ₂ -based mixed halide glass and AgBr-PbBr-based bromide glass, Ho ³⁺ , P
Up-conversion laser light can be obtained by changing the excitation wavelength of each of the microspheres to which r ³⁺ , Ce ^3+, or Nd ³⁺ is added.

[0017]

As described above, by forming the up-conversion laser glass material into a microsphere shape,
The optical confinement effect can be realized, and at the same time, the microsphere itself is used as a resonator, making it possible to increase the Q value of the resonator compared to an up-conversion laser using a bulk crystal. Up-conversion laser oscillation can be performed at room temperature even with a composition or a glass composition that did not oscillate unless fiberized.

[Brief description of the drawings]

FIG. 1 shows an up-conversion excitation mechanism. (A) Energy transfer between excited ions (b) Excited state absorption (multi-step excitation)

FIG. 2 is a configuration diagram showing an embodiment of an up-conversion laser using a rare-earth-doped microsphere glass as an up-conversion laser material.

FIG. 3 shows an example of excitation light irradiation on a rare earth-doped microsphere glass.

[Explanation of symbols]

 1. Excitation light source 2. 2. Condensing lens 3. Rare earth doped microsphere glass Elliptical reflector 5. Optical fiber 6. Condensing lens 7. Focused excitation laser

Continuing from the front page (72) Inventor Natsumura Nishimura 5253 Oki Ube, Oji, Ube, Yamaguchi Prefecture Inside Central Glass Co., Ltd. Ube Research Laboratories (56) References JP-A-6-219777 (JP, A) JP-A-63-177483 (JP, A) JP-A-3-116794 (JP, A) JP-B-42-21600 (JP, A) B2) Special Table 63-503495 (JP, A) International Publication 92/20125 (WO, A1) Ceramics Vol. 26, No. 2, p. 144-148 (58) Fields investigated (Int. Cl. ⁶ , DB name) ) H01S 3/06 H01S 3/16-3/17

Claims (1)

(57) [Claims] 1. A rare earth element ion containing at least one of erbium, holmium, praseodymium, thulium, neodymium and cerium, and having a content of 5
The particle size is in the range of 0 to 5000 ppm, and the particle size is 50 to 200 ppm.
An up-conversion laser material, which is a microsphere glass having a diameter of 0 μm, and the glass is fluoride glass, chloride glass, bromide glass, or chlorinated fluoride glass.