JP2541090B2 - Laser oscillator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser device that oscillates in the eye-safe region.

[0002]

2. Description of the Related Art In recent years, it has been desired to make a laser used in the atmosphere eye-safe. Therefore, research and development of an eye-safe laser device have been promoted. To date, lasers that oscillate at eye-safe wavelengths range from 1.87 to 2.14μ.
Tm laser oscillating at m (Optics Letters (O
ptics Letters) vol. 15 1990
Year 486p), Ho laser oscillating at 2.1 μm (Optics Letters
s) vol. 15 1990 320p), 1.06
A report of optical parametric oscillation of 700 to 2200 nm by the second harmonic (532 nm) of the Nd laser of μm and the non-linear crystal LiB ₃ O ₅ (Proceedings of the 52nd Annual Meeting of the Japan Society for Applied Physics 11p-M-4) is there.

On the other hand, as a laser having YVO ₄ as a laser base material, a 1.06 μm laser using Nd activator is generally used. In addition, other reported examples of Tm activator laser (Optics Letters vol.
17 1992 189p).

Further, as a laser base material of a laser using Er activator, glass (Japanese Patent Application No. 61-226297), YLiF ₄ (Electronic Letters (El
electronics Letters) vol. 25
1989 1389p), Y ₃ A ₁₅ O ₁₂ and Y ₃ S
c ₂ Ga ₃ O ₁₂ (J. of Applied Physics)
vol. 70 1991, 7227p).

[0005]

However, the conventionally developed eye-safe laser has the following problems. That is, the optimum eye-safe wavelength is around 1.5 μm, and the oscillation wavelengths of conventional Tm lasers and Ho lasers deviate from this wavelength band. Further, in the optical parametric oscillation, the conversion loss due to the non-linear optical effect being passed twice cannot be avoided, and the oscillation intensity is very weak.

The oscillation wavelength of the Er glass laser is 1.5.
Although it is in the eye-safe region of μm, since the laser base material is glass, the oscillation wavelength is gradual, and it is difficult to manufacture the glass containing high concentration Er, so that a large glass laser is required and the entire laser device becomes large. In addition, there are problems such as low heat resistance. On the other hand, the other Er activator lasers have oscillation wavelengths not in the eye-safe region.

It is an object of the present invention to utilize an Er activator capable of oscillating in an optimum eye-safe wavelength band of 1.5 μm and to solve the problems of a glass laser, a solid-state laser matrix YVO.
_The purpose is to provide a high-efficiency laser that utilizes the _four .

[0008]

The inventors have found that the composition formula is Y
We succeeded in producing a single crystal composition in which the impurity represented by VO ₄ was mixed with Er (Japanese Patent Application No. 4-268891), and in this single crystal, ⁴ I of Er ³⁺ ion was added.
^{_{1 3/2 → 4 I 1}} 5/2 oscillates at the target wavelength by utilizing the energy transition YVO ₄ crystals were laser maternal Er: YVO ₄ to create a laser oscillator. That
At this time, the excitation light source is a semiconductor laser, and the polarization direction of the semiconductor laser oscillation light is perpendicular to the c-axis of the YVO ₄ crystal (σ-polarized light),
Alternatively, it has been found that a laser oscillation device can be obtained which is arranged in a parallel (π-polarized) positional relationship and can effectively utilize different spectral characteristics depending on the polarization direction.

Since the YVO ₄ crystal is a uniaxial crystal, the spectral characteristics differ depending on the direction of the crystal axis. The fluorescence characteristics of Er: YVO ₄ single crystal in σ-polarized light and in π-polarized light were clarified for the first time by the inventors, and as shown in FIGS.
Er: YVO ₄ is σ and π polarized light from 1480 nm to 162
It was found that there was fluorescence at 0 nm.

As a result, Er: YVO ₄ becomes a laser medium by the combination of the excitation medium and the resonator, and laser oscillation is possible in the eye-safe region of 1480 nm to 1620 nm. Here, the resonator is a Fabry-Perot interferometer in which two reflecting mirrors, which are a high-reflecting mirror having a high reflectance and an output mirror, are combined, and the same effect can be obtained by a mirror coat corresponding to a target wavelength.

In an Er: YVO ₄ laser device using a combination of Er: YVO ₄ , an excitation medium and a resonator, since the laser host is YVO ₄ , not only the problems of the Er glass laser are solved but also the solid-state laser is solved. Characteristic of
A laser with a sharp oscillation wavelength, a compact laser device and a high environmental resistance by increasing the concentration of activators was obtained. Also, YV
Since the O ₄ laser has a large absorption characteristic of pumping light among solid-state lasers, further improvement in efficiency and miniaturization and simplification of the device can be expected.

[0012]

According to the energy level diagram of Er ^{3 +} in the YVO ₄ crystal of FIG. 3, the energy transition of excited Er ^{3 +} occurs as follows. _{^{4 I 1 5/2 → 4}} I 9/2 ( excitation by input _{^{light) 4 I 9/2 → 4}} I 1 3/2 ( non-radiative transitions) after being excited to the upper level in this way, ⁴ I _{1 5/2} by stimulated emission level, for oscillating a laser light of 1.5μm band.

[0013]

(Embodiment 1) FIGS. 4 and 5 show an example of a laser oscillator according to the present invention. The excitation light source related to the laser oscillation is the flash lamp 1 or the semiconductor laser 2. In the flash lamp excitation laser oscillator shown in FIG. 4, the excitation light is radiated and reflected by the Er: YVO ₄ crystal 5 to which the magnesium fluoride / zeolite antireflection coating 4 corresponding to the target wavelength is added by the configuration of the lamp house 3. The mirror 6 and the output mirror 7 form a laser resonator structure.

In the semiconductor laser pumped laser oscillator shown in FIG. 5, the pumping light is applied to the Er: YVO ₄ crystal 5 through the optical fiber 8. The Er / YVO ₄ crystal 5 has a TiO ₂ / SiO ₂ high reflection mirror coat 9 corresponding to the target wavelength as shown in the figure, a magnesium fluoride / zeolite antireflection coat 4, and an oscillation wavelength of a semiconductor laser as an excitation light source. (807 nm)
Is coated with a magnesium fluoride / zeolite anti-reflective coating 10. A laser resonator structure is formed by combining these coats and the output mirror 7. A concave lens is used for the output mirror, and the output light is collimated.

(Embodiment 2) FIG. 6 shows a second embodiment of the present invention.

A semiconductor laser 2 is used as an excitation light source related to laser resonance, and the excitation light is irradiated onto the Er: YVO ₄ crystal 5 by a condenser lens 11. Here, in order to effectively utilize the spectral characteristic of Er: YVO ₄ due to the difference in polarization direction, the oscillation light of the semiconductor laser 2 and the c-axis of the Er: YVO ₄ crystal 5 are perpendicular (σ-polarized) or parallel. The arrangement is such that the positional relationship is (π-polarized). The Er: YVO ₄ crystal 5 has a TiO ₂ / SiO ₂ high reflection mirror coat 9 corresponding to the target wavelength as shown in the figure, a magnesium fluoride / zeolite nonreflective coat 4, and an oscillation wavelength of a semiconductor laser of excitation light. 807n
A magnesium fluoride / zeolite non-reflective coating 10 corresponding to m is provided, and a resonator structure is formed together with the output mirror 7. A concave lens is used for the output mirror in order to collimate the output laser light.

It was found that the laser oscillating device according to Examples 1 and 2 provided a laser oscillated light of 1530 nm, and the stability of this laser oscillation was very high.

[0018]

According to the present invention, 1480 nm to 16
A solid-state laser capable of oscillating 20 nm was obtained. as a result,
It is possible to provide a highly efficient and highly reliable eye-safe small-sized solid-state laser, and various applications are considered especially in the industrial field where laser light is used in the air.

[Brief description of drawings]

FIG. 1 Er: YVO at 1400-1700 nm.
_{It is} the fluorescence characteristic of ₄ (at the time of σ polarization).

FIG. 2 Er: YVO at 1400-1700 nm.
_{It is} the fluorescence characteristic of ₄ (when π-polarized).

FIG. 3 is an energy level diagram of Er ³ + in a YVO ₄ crystal.

FIG. 4 is a laser oscillation device diagram showing the first embodiment of the present invention.

FIG. 5 is a laser oscillation device diagram showing the first embodiment of the present invention.

FIG. 6 is a laser oscillator diagram showing a second embodiment of the present invention.

[Explanation of symbols]

1 Flash Lamp 2 Semiconductor Laser 3 Lamp House 4 Magnesium Fluoride / Zeolite Non-Reflective Coating Corresponding to Target Wavelength 5 Er: YVO ₄ Crystal 6 Reflecting Mirror 7 Output Mirror 8 Optical Fiber 9 TiO ₂ / SiO ₂ Corresponding to Target Wavelength System high reflection mirror coat 10 Magnesium fluoride / zeolite antireflection coat for semiconductor laser oscillation wavelength 807 nm 11 Condensing lens

Claims (1)

(57) [Claims] 1. Use of energy transition ⁴ I _{1 3 2} → ⁴ I ₁ 5/2 of Er ^{3 +} ion of a single crystal composition in which impurity Er is mixed in a composition represented by a composition formula YVO _4. Is an Er: YVO ₄ laser device that oscillates at a wavelength of 1480 nm to 1620 nm by
Body laser, polarization direction of semiconductor laser oscillation light and YVO
₄ The c-axis of the crystal must be vertical or parallel.
A laser oscillating device.