JPH0745898A - Laser equipment - Google Patents

Abstract

(57) [Summary] [Object] To obtain a laser device using a medium doped with both thorium and holmium ions, which has high efficiency and high output with respect to holmium ions . CONSTITUTION: a laser medium with thorium and holmium were co-doped, and wavelength separation element light and Horomiumuion the first wavelength to separate a second light of a wavelength having a gain with a gain Soriumuion, first The first resonator and the first switching element that resonate and control the light of the wavelength, and the second resonator and the second switching element that resonate and control the light of the second wavelength. In addition, a laser medium doped with both thorium and holmium, a resonator including this laser medium, and a switching element that exclusively controls the Q of the resonator for light having a wavelength at which the thorium ion has a gain are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device using a medium doped with both Tm ³⁺ and Ho ³⁺ ions as a laser medium, and more particularly to a laser device for obtaining a giant pulse.

[0002]

2. Description of the Related Art As an optically pumped laser, several methods have been proposed for finally producing holmium (Ho ³⁺ ) ions. The simplest configuration is direct H
There is a method of exciting o ³⁺ ions, but this is not practical because of poor excitation efficiency. To improve this, a laser in which thorium (Tm ³⁺ ) ions are also present is used. That is, the light energy is once absorbed by Tm ³⁺ having a high absorption efficiency, and then transferred to Ho ³⁺ having a close energy level. FIG. 8 shows a first conventional example, which is an S.S.
R. Bowman et al. (IEEE J. Quantum Electron., Vol.2
7, p.1129〜1131, 1991) and Tm ³⁺ and Ho ³⁺
It is a block diagram of a Q-switched laser using a medium co-doped with ions as a laser medium. In the figure, 1 is a high reflection mirror, 2 is an output coupling mirror, and the high reflection mirror 1 and the output coupling mirror 2 are shown.
Constitutes a laser resonator. 3 is a laser rod made of a medium doped with both Tm ³⁺ and Ho ³⁺ ions, 4 is the optical axis of the resonator, 5 is laser output light, and 6 is Q of the resonator.
Is an excitation light source, 8 is excitation light, and 9 is a switching element control circuit.

FIG. 9 shows an energy diagram of this laser. The laser oscillation operation will be described with reference to FIGS. The switching element 6 brings the resonator into a low Q state. The laser rod 3 is excited by the excitation light 8 from the excitation light source 7.
Excite. Tm ³⁺ co-doped into laser rod 3
And Ho ³⁺ ions, the Tm ³⁺ ion becomes a sensitizer, and finally the Ho ³⁺ ion becomes an active ion that performs laser oscillation. Further, the laser rod 3 may be doped with Cr ³⁺ , Er ³⁺ ions having a wide absorption wavelength region as a sensitizer. The process of exciting Ho ³⁺ ions is as follows. The excitation light 8 first excites Tm ³⁺ ions directly or indirectly via Cr ³⁺ , Er ³⁺ ions or the like doped in the laser rod 3 to generate Tm ³⁺ ions at the ³ H ₄ level. To be done.

When the Tm ³⁺ ion of the ³ H ₄ level relaxes to the ³ F ₄ level by non-radiative transition, Tm ^{3+ of the} adjacent ground level
Energy is applied to the ions and they are excited to the ³ F ₄ level. By these two processes, that is, the cross relaxation process, two ³ F ₄ level Tm ³⁺ ions are produced from one ³ H ₄ level Tm ³⁺ ion, and the quantum efficiency can be doubled at maximum. it can. Due to the energy transfer from the Tm ³⁺ ion of the ³ F ₄ level, the Ho ³⁺ ion is the upper level of the laser.
Excited to the ⁵ I ₇ level. The ³ F ₄ level of the Tm ³⁺ ion and the ⁵ I ₇ level of the Ho ³⁺ ion are close to each other in energy level, and ⁵ I ₇ of the Ho ³⁺ ion which is an inverse process of the above energy transfer.
There is energy transfer from the level to the ³ F ₄ level of the Tm ³⁺ ion.

Ho ³⁺ ions are excited and laser rod 3
Has a sufficient gain, the switching element 6 brings the resonator for Ho ³⁺ into the high Q state. Then, stimulated emission is rapidly performed and laser oscillation occurs. At this time, a giant pulse is output as laser output light 5 from the output coupling mirror 2.

As described above, since energy transfer from the ⁵ I ₇ level of Ho ³⁺ ions to the ³ F ₄ level of Tm ³⁺ ions exists, the energy accumulated in the laser rod 3 is H.
not concentrated in the ⁵ I ₇ level of o ³⁺ ion, of Ho ³⁺ ion ⁵
It is dispersed in the I ₇ level and the ³ F ₄ level of the Tm ³⁺ ion. The degree of dispersion differs depending on the concentration and temperature of each ion, but in Tm, Ho: YAG that is usually used, almost the same number of ions exist at both levels at room temperature. Also, Tm ³⁺
The time constant of energy transfer from the ³ F ₄ level of the ion to the ⁵ I ₇ level of the Ho ³⁺ ion is several to ten and several μsec, which is very long compared to the pulse width of the giant pulse. Therefore, the energy accumulated in the ⁵ I ₇ level of Ho ³⁺ ions is taken out by the rapid stimulated emission, but the energy accumulated in Tm ³⁺ ions cannot be used.

The following are lasers that have improved this. FIG. 10 shows a second conventional example, in which R.I. C. Stonema
n, L. Estrowitz (OPTICAL LETTERS, vol.1
7, No. 10, p. 736 to 738, 1992), which is an intracavity-pumped Ho: YAG laser.
In the figure, 10 is Tm: YAG and 11 is Ho: YA.
G and 12 are the first dielectric multilayer film formed on the end surface of Tm: YAG 10, and 13 is the second dielectric multilayer film formed on the end surface of Ho: YAG 11. Here, the first dielectric multilayer film 12 is highly reflective to light having a wavelength in the vicinity of 2.0 μm in which Tm ³⁺ ions have a gain and in the vicinity of 2.1 μm in which Ho ³⁺ ions have a gain, It is highly transmissive to light having a wavelength in the vicinity of 0.78 μm, which is the absorption wavelength range of Tm ³⁺ ions. The second dielectric multilayer film 13 is highly transmissive to light having a wavelength in the vicinity of 2.0 μm in which Tm ³⁺ ions have a gain and in the vicinity of 2.1 μm in which Ho ³⁺ ions have a gain. The surfaces of Tm: YAG10 and Ho: YAG11 on which the dielectric multilayer film is not formed are bonded to each other by optical contact. The output coupling mirror 2 is highly reflective to light having a wavelength near 2.0 μm where Tm ³⁺ ions have a gain and partially reflected to light having a wavelength near 2.1 μm where Ho ³⁺ ions have a gain. Is. The output coupling mirror 2 placed outside the first dielectric multilayer film 12 and the second dielectric multilayer film 13 constitutes a resonator.

FIG. 11 shows an energy diagram of this laser. Tm: YAG has a gain near 2.0 μm, while Ho: YAG absorbs light having a wavelength near 2.0 μm. Therefore, with a Tm: YAG laser, Ho:
It is possible to excite YAG. But Ho: Y
The absorption coefficient of light having a wavelength near 2.0 μm of AG is small. Therefore, H in the Tm: YAG laser resonator
The excitation efficiency is improved by inserting o: YAG and confining the oscillation light having a wavelength near 2.0 μm in the resonator.

The laser oscillation operation will be described with reference to FIG. The excitation light 8 having a wavelength in the vicinity of 0.78 μm, which is the absorption wavelength region of Tm: YAG, is transmitted from the first dielectric multilayer film 12 to T
m: incident on YAG10. The excitation light is absorbed and the Tm ³⁺ ion is excited to the ³ H ₄ level. Cross-relaxation, similar prior art example described above, Tm ³⁺ ions of the two ³ F ₄ level position than Tm ³⁺ ions of one ³ H ₄ level position is created, it can be doubled maximum quantum efficiency . Tm ³⁺ ions at the ³ F ₄ level have a gain in the vicinity of 2.0 μm. When excited and exceeds the threshold value, Tm: YAG10 oscillates in the vicinity of 2.0 μm.
Since the first dielectric multilayer film 12 and the output coupling mirror 2 which form the resonator are highly reflective to the light having the wavelength near 2.0 μm, the light having the wavelength near 2.0 μm is used as the resonator. Will be trapped in. (Hereinafter, a resonator constituted by a set of high-reflecting mirrors is a confinement type resonator.) Therefore, most of the oscillation light of Tm: YAG10 that resonates in the laser resonator is absorbed by Ho: YAG11. Can be made. By absorbing the oscillation light of Tm: YAG10, Ho ³⁺ ions are excited to the ⁵ I ₇ level. Ho: YA
G11 has a gain in the vicinity of 2.1 μm, and when it exceeds the threshold value, the laser output light 5 having a wavelength in the vicinity of 2.1 μm is output from the output coupling mirror 2.

Tm: YAG is a three-level laser, and energy is stored in Tm: YAG in the form of population inversion. The energy stored in this Tm: YAG is Ho:
It does not contribute to the oscillation of YAG, which is one of the factors that reduce the overall efficiency. Further, in the above configuration, Tm: YAG and H
Two laser media of o: YAG must be used,
There is a drawback that the configuration becomes complicated.

[0011]

Since the conventional laser device using the holmium ion as the sensitizer and the holmium ion as the active ion has been constructed as described above, the thorium ion and the holmium ion are in equilibrium. Since they are excited together while maintaining the state, there is a problem that the energy accumulated in the thorium ion is not used during the oscillation of the holmium ion and the efficiency is poor. In addition, an apparatus that separately excites thorium ions and holmium ions has a complicated structure and cannot be said to be efficient.

The present invention has been made to solve the above problems. First, energy is concentratedly accumulated in thorium ions, and then the energy is converted into light to excite the target holmium ions. The purpose of this is to obtain an efficient laser device that fully utilizes the energy stored in thorium ions.

[0013]

A laser device according to the present invention comprises a laser medium doped with both thorium and holmium, light of a first wavelength excited by thorium ions and a second wavelength excited by holmium ions. Wavelength separating element for separating the light of the first wavelength, the first resonator for resonating and controlling the light of the first wavelength and the first switching element, and the second resonator for resonating and controlling the light of the second wavelength And a second switching element. According to a second aspect of the present invention, in the first aspect of the invention, the wavelength separation element includes a dispersion type wavelength separation element that disperses light and separates the light in the dispersed direction. According to a third aspect of the present invention, in the laser apparatus of the first aspect, a transmissive wavelength separation element having a wavelength-dependent transmittance or reflectance is used as the wavelength separation element.

Further, in the laser device according to the fourth aspect, a laser medium doped with both thorium and holmium, a resonator containing this laser medium, and a Q of this resonator for light of a wavelength exclusively excited by the thorium ion. And a switching element for controlling the. The laser device according to claim 5 is the laser device according to claim 4.
In the invention, a resonator having a high reflection is used as a resonator, particularly for thorium ions.

[0015]

In the laser device of the present invention, the thorium ions and the holmium ions absorb energy by being excited by light. First, the thorium ions oscillate in the first resonator, and then most of the oscillated light is hollow. It is absorbed by mimium ions and becomes a giant pulse. Further, in the laser device according to the fourth aspect, first, thorium ions are oscillated in the confinement resonator by excitation with light, and then, most of the oscillated light is absorbed by the holmium ions by the switching operation to form a giant pulse. .

[0016]

EXAMPLES Example 1. Hereinafter, a first embodiment according to the first invention will be described with reference to the drawings. FIG. 1 is a block diagram of a laser device according to a first embodiment of the present invention. In the figure, 14
Is the first for light with wavelengths near 2.0 and 2.1 μm
High-reflecting mirror, 15 is a wavelength separation element, 16 is a second high-reflecting mirror for light having a wavelength near 2.0 μm, and 17 is 2.1 μm.
It is an output coupling mirror for light having a wavelength near m. Reference numeral 18 is a first switching element for light having a wavelength near 2.0 μm, and 19 is a second switching element for light having a wavelength near 2.1 μm. That is, the first high-reflecting mirror 14 and the second high-reflecting mirror 16 are connected via the wavelength separation element 15.
First confinement type that resonates light with a wavelength near 2.0 μm
Of the resonator. Similarly, the first high-reflecting mirror 14 and the output coupling mirror 17 form a second resonator that resonates light having a wavelength near 2.1 μm. The first and second resonators have the same optical axis on the laser rod 3. The wavelength separation element 15 includes thorium (Tm ³⁺ ) and holmium (H
o ³⁺ ) ion oscillation light of 2.0 and 2.
Light having a wavelength in the vicinity of 1 μm is separated. The first and second switching elements 18 and 19 are placed on the optical axes of the first and second resonators, respectively.

Next, the laser oscillation operation will be described. The laser rod 3 is excited by the excitation light 8 from the excitation light source 7. The first and second switching elements 18 and 19 keep the first and second resonators in the low Q state. Therefore, the excitation light 8 is absorbed, and the Tm ³⁺ and Ho ³⁺ ions in the laser rod 3 both accumulate energy. The first resonator is a resonator for light having a wavelength near 2.0 μm by the wavelength separating element 15. After being sufficiently excited, the first switching element 18
This brings the first resonator into the high Q state. Thus, the Tm ³⁺ ions suddenly oscillate in the first resonator. Since the first resonator is a confinement type resonator, the oscillation light in the first resonator is mostly absorbed by Ho ³⁺ ions in the laser rod 3 sharing the optical axis. . That is, the energy accumulated in the Tm ³⁺ ion is transferred to the Ho ³⁺ ion.

The second resonator is a resonator for light having a wavelength near 2.1 μm by the wavelength separating element 15. The oscillation light in the first resonator is absorbed and Ho
^{When the 3+} ions have sufficient energy, the second switching element 19 brings the second resonator into the high Q state. In this way, the Ho ³⁺ ions rapidly oscillate in the second resonator, and a giant pulse having a wavelength near 2.1 μm is obtained from the output coupling mirror 17.

The energy stored in Ho ³⁺ ions is H
Energy transfer from o ³⁺ ion to Tm ³⁺ ion again,
Lost due to up conversion. The time constant of movement at this time is several μsec to ten and several μsec.
In order to reduce the influence of the loss, the switching timing of the second switching element 19 is set so that oscillation occurs when the Ho ³⁺ ions have the maximum gain.
That is, the oscillation of the Ho ³⁺ ions is made to occur from the time when the intensity of the oscillation light of the Tm ³⁺ ions in the first resonator is maximized to the end of the oscillation. The time of movement at this time is within 300 nsec. That is, the pulse width of the oscillation light of Ho ³⁺ ions and Tm ³⁺ ions is at most 2 to 300 nsec. Therefore, the amount of loss in the Tm ³⁺ direction can be reduced in the Q-switched laser having the above configuration due to the magnitude of the time constant in the opposite direction, and the efficiency of Ho ³⁺ generation is improved. As described above, the configuration of the laser oscillator according to the present invention makes it possible to obtain a highly efficient and high output giant pulse.

Example 2. FIG. 2 shows the second aspect of the first invention.
It is a block diagram which shows the Example of. The second embodiment of FIG. 2 uses a dispersion prism as the wavelength separation element in the first embodiment of FIG. In FIG. 2, 20 is a dispersion prism.

Referring to FIG. Dispersion prism 20
The incident angle of the light incident on is different depending on the wavelength. Therefore, the first and second resonators are configured according to the emission angles of light having wavelengths of 2.0 μm and 2.1 μm and so as to have the same optical axis on the laser rod 3.
The principle of the laser oscillation operation of the second embodiment is the same as that of the first embodiment shown in FIG. Although not described in detail, this configuration has a feature that the oscillation wavelength can be selected more finely.

Example 3. FIG. 3 shows a third aspect of the first invention.
It is a block diagram which shows the Example of. The third embodiment of FIG. 3 uses a diffraction grating as the wavelength separation element in the first embodiment of FIG. In FIG. 3, reference numeral 21 is a diffraction grating.

Referring to FIG. The light incident on the diffraction grating 21 has a different emission angle depending on the wavelength, as in the dispersion prism 20 of the second embodiment shown in FIG. Therefore, the second of FIG.
The first and second resonators are configured in the same manner as in the above embodiment. The principle of the laser oscillation operation of the third embodiment is the same as that of FIG.
Is the same as the embodiment described above. This configuration has a feature that the oscillation wavelength can be finely selected.

Example 4. FIG. 4 is a fourth diagram according to the first invention.
It is a block diagram which shows the Example of. Reference numeral 22 is a first interference filter, and 23 is a second interference filter.

Referring to FIG. The first interference filter 22 is highly transmissive to light having a wavelength near 2.1 μm,
It is highly reflective for light with a wavelength near 2.0 μm. The second interference filter 23 is highly transmissive for light having a wavelength near 2.0 μm and highly reflective for light having a wavelength near 2.1 μm. The second high-reflecting mirror 16 and the first interference filter 22 constitute a confinement-type third resonator that resonates light having a wavelength near 2.0 μm. Also, the output coupling mirror 1
7 and the second interference filter 23 constitute a fourth resonator that resonates light having a wavelength near 2.1 μm. The third and fourth resonators are configured to have the same optical axis on the laser rod 3. The principle of laser oscillation operation is shown in Fig. 1.
Of the first embodiment. Since this configuration has only a single optical axis, the configuration is easy and no optical axis adjustment is required.

Example 5. FIG. 5 shows a fifth aspect of the first invention.
It is a block diagram which shows the Example of. The fifth embodiment of FIG. 5 has a configuration in which the second interference filter 23 of the fourth embodiment of FIG. 4 is omitted.

Referring to FIG. 2.0 and 2.
The first high-reflecting mirror 14 and the first interference filter 22 for light with a wavelength near 1 μm constitute a confinement-type third resonator that resonates light with a wavelength near 2.0 μm. Similarly, the first high-reflecting mirror 14 and the output coupling mirror 17 constitute a fourth resonator that resonates light having a wavelength near 2.1 μm.
The third and fourth resonators are configured to have the same optical axis on the laser rod 3. The principle of the laser oscillation operation is the same as that of the first embodiment shown in FIG.

Example 6. FIG. 6 is a block diagram showing an embodiment according to the second invention. Reference numeral 24 is an output coupling mirror that is partially reflective to light having a wavelength near 2.1 μm and highly reflective to light having a wavelength near 2.0 μm. First high-reflecting mirror 1
4 and the output coupling mirror 24 form a resonator. FIG. 7 shows Ho ³⁺ ions ⁵ I ₇ in one embodiment according to the second invention.
It is a diagram showing the relationship between the distribution density of the level of the distribution density and Tm ³⁺ ions ³ F ₄ level position.

Next, the laser oscillation operation will be described with reference to FIGS. The laser rod 3 is excited by the excitation light 8 from the excitation light source 7. Then, the switching element 18 switches the resonator from the low Q state to the high Q state. At this time, it is necessary that the distribution density of the Tm ³⁺ ion ³ F ₄ level exceeds the threshold level and that the Ho ³⁺ ion ⁵ I ₇ level does not exceed the threshold level. Ho ³⁺ in laser rod 3 related to distribution density
Since the densities of Tm ³⁺ ions and Tm ³⁺ ions cannot be changed once they are manufactured, the excitation intensity and, if necessary, the reflectance of the output coupling mirror 24 are selected so as to satisfy this condition. In this state, since the Tm ³⁺ ion exceeds the threshold value, Tm ³⁺ oscillates and is excited in the resonator. The resonator is 2.0
Since it is a confinement type with respect to light having a wavelength in the vicinity of μm, most of the oscillation light is absorbed by Ho ³⁺ ions in the laser rod 3. Oscillation of Tm ³⁺ ions is rapidly performed by the Q switch operation by the switching element 18. Thus Tm ³⁺
The oscillation light of the ions rapidly increases, and the Ho ³⁺ ions absorb the oscillation light to oscillate exceeding the threshold value. Since this transition occurs suddenly, it becomes a so-called gain switch state,
An oscillation similar to that of the Q switch can be obtained. Therefore, a giant pulse of the oscillation light of Ho ³⁺ ions is obtained from the output coupling mirror 22.

As described above, with the structure of the laser according to the second invention, first, the Tm ³⁺ ion is selectively resonated, the energy is transferred through the oscillation light, and the Ho ³⁺ ion is oscillated. By performing the same operation as the gain switch, it is possible to obtain a giant pulse with high efficiency and high output without requiring a plurality of switching elements.

[0031]

As described above, according to the present invention, Tm ³⁺
Both Ho ³⁺ ions in the laser device using doped laser medium, first selectively the energy stored in the Tm ³⁺ ions by the light oscillation is absorbed in Ho ³⁺ ions, thereby Ho ³⁺ To oscillate the ions, Ho
There is an effect that a giant pulse with high efficiency and high output can be obtained for ³⁺ ions.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a laser device that is an embodiment of the present invention.

FIG. 2 is a configuration diagram of a laser device that is another embodiment of the present invention.

FIG. 3 is a configuration diagram of a laser device which is still another embodiment of the present invention.

FIG. 4 is a configuration diagram of a laser device which is still another embodiment of the present invention.

FIG. 5 is a configuration diagram of a laser device which is still another embodiment of the present invention.

FIG. 6 is a configuration diagram of a laser device according to an embodiment of the present invention.

7 is a diagram showing a relationship among thorium ions, holmium ion densities, and oscillation light in the example of FIG.

FIG. 8 is a configuration diagram of a laser device of a first conventional example.

FIG. 9 is a diagram showing an energy diagram of a conventional laser device.

FIG. 10 is a configuration diagram of a laser device of a second conventional example.

FIG. 11 is a diagram showing an energy diagram of a laser device of a second conventional example.

[Explanation of symbols]

 14 First High-Reflecting Mirror 15 Wavelength Separation Element 16 Second High-Reflecting Mirror 17 Output Coupling Mirror 18 First Switching Element 19 Second Switching Element 20 Dispersion Prism 21 Diffraction Grating 22 First Interference Filter 23 Second Interference filter 24 Output coupling mirror

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[Procedure amendment]

[Submission date] December 28, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 4

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

A pumped laser according to the prior art light, several methods to ultimately holmium (Ho ³⁺⁾ excite ions have been proposed. The simplest configuration is direct H
There is a method of exciting o ³⁺ ions, but this is not practical because of poor excitation efficiency. To improve this, a laser in which thorium (Tm ³⁺ ) ions are also present is used. That is, the light energy is once absorbed by Tm ³⁺ having a high absorption efficiency, and then transferred to Ho ³⁺ having a close energy level. FIG. 8 shows a first conventional example, which is an S.S.
R. Bowman et al. (IEEE J. Quantum Electron., Vol.2
7, p.1129〜1131, 1991) and Tm ³⁺ and Ho ³⁺
It is a block diagram of a Q-switched laser using a medium co-doped with ions as a laser medium. In the figure, 1 is a high reflection mirror, 2 is an output coupling mirror, and the high reflection mirror 1 and the output coupling mirror 2 are shown.
Constitutes a laser resonator. 3 is a laser rod made of a medium doped with both Tm ³⁺ and Ho ³⁺ ions, 4 is the optical axis of the resonator, 5 is laser output light, and 6 is Q of the resonator.
Is an excitation light source, 8 is excitation light, and 9 is a switching element control circuit.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

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[0013]

A laser device according to the present invention comprises a laser medium doped with both thorium and holmium , a second wavelength light having a gain of a thorium ion and a second gain of a holmium ion. Wavelength separating element for separating the light of the first wavelength and the first for resonating and controlling the light of the first wavelength
The resonator and the first switching element, and the second resonator and the second switching element that resonate and control the light of the second wavelength. The laser device according to claim 2 is the laser device according to claim 1.
In the invention described above, as the wavelength separation element, a dispersion type wavelength separation element that disperses light and separates the light in the dispersed direction is used.
According to a third aspect of the present invention, in the laser apparatus of the first aspect, a transmissive wavelength separation element having a wavelength-dependent transmittance or reflectance is used as the wavelength separation element.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Further, in the laser device of claim 4, a laser medium doped with both thorium and holmium, a resonator containing this laser medium, and exclusively the thorium ion has a gain.
And a switching element that controls the Q of the resonator with respect to light of one wavelength. According to a fifth aspect of the present invention, in the fourth aspect of the invention, as the resonator, a resonator having high reflectivity for thorium ions is used.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

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[0015]

In the laser device of the present invention, the thorium ions and the holmium ions absorb energy by being excited by light. First, the thorium ions oscillate in the first resonator, and then most of the oscillated light is hollow. Holmium ions are oscillated in the second resonator after being absorbed by the ions.
And get a giant pulse. Further, in the laser apparatus according to claim 4, first Soriumuion with excitation by light is oscillated by the switching operation, most of the oscillation light is absorbed in Horomiumuion, utilization of Horomiumuion
Gains increase sharply. Then holmium ions oscillate
And get a giant pulse.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Next, the laser oscillation operation will be described. The laser rod 3 is excited by the excitation light 8 from the excitation light source 7. The first and second switching elements 18 and 19 keep the first and second resonators in the low Q state. Therefore, the excitation light 8 is absorbed, and the Tm ³⁺ and Ho ³⁺ ions in the laser rod 3 both accumulate energy. The first resonator is a resonator for light having a wavelength near 2.0 μm by the wavelength separating element 15. After being sufficiently excited, the first switching element 18
This brings the first resonator into the high Q state. Thus, the Tm ³⁺ ions suddenly oscillate in the first resonator. Because the first resonator is a trapping type resonator, the oscillation light in the first resonator, in the laser rod 3 that shares the optical axis, energy of the oscillation light in Ho ³⁺ ions
Most of the rugies are absorbed. That is, the energy accumulated in the Tm ³⁺ ion is transferred to the Ho ³⁺ ion.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

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Next, the laser oscillation operation will be described with reference to FIGS. The laser rod 3 is excited by the excitation light 8 from the excitation light source 7. Then, the switching element 18 switches the resonator from the low Q state to the high Q state. At this time, it is necessary that the distribution density of the Tm ³⁺ ion ³ F ₄ level exceeds the threshold level and that the Ho ³⁺ ion ⁵ I ₇ level does not exceed the threshold level.
It Excitation intensity and output coupling mirror 2 should meet this condition.
4 reflectance, Ho ³⁺ and Tm at laser rod 3
Select the density of ³⁺ ions. Since the density of Ho ³⁺ and Tm ³⁺ ions in the laser rod 3 related to the distribution density cannot be changed once manufactured, the pumping intensity and the reflectance of the output coupling mirror 24 are usually selected so as to satisfy this condition. To do. In this state, since the Tm ³⁺ ion exceeds the threshold value, Tm ³⁺ oscillates and is excited in the resonator. Since the resonator is a confinement type with respect to light having a wavelength near 2.0 μm, most of the oscillation light is absorbed by Ho ³⁺ ions in the laser rod 3. Oscillation of Tm ³⁺ ions is rapidly performed by the Q switch operation by the switching element 18. In this way, the oscillating light of Tm ³⁺ ions suddenly increases,
Ho ³⁺ ions absorb this and exceed the threshold to oscillate. Since this transition occurs abruptly, a so-called gain switch state occurs, and oscillation similar to that of the Q switch is obtained. Therefore, a giant pulse of the oscillation light of Ho ³⁺ ions is obtained from the output coupling mirror 22.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

[0031]

As described above, according to the present invention, Tm ³⁺
In a laser device using a laser medium co-doped with both Ho ³⁺ ions and Ho ³⁺ ions, first, energy stored in Tm ³⁺ ions is selectively oscillated to be absorbed by Ho ³⁺ ions, and thereby Ho ³⁺ ions are absorbed. Ho ³⁺ to oscillate
There is an effect that a giant pulse with high efficiency and high output can be obtained for ions.

Claims (5)

[Claims] 1. A laser medium doped with both thorium and holmium, a wavelength separation element for separating light of a first wavelength excited by thorium ions and light of a second wavelength excited by holmium ions, A first resonator and a first switching element that resonate and control the light of the first wavelength, and a second resonator and a second switching element that resonate and control the light of the second wavelength. Laser device. 2. The laser device according to claim 1, wherein the wavelength separation element is a dispersion type wavelength separation element which disperses light and separates the light in the dispersed direction. 3. The laser device according to claim 1, wherein a transmission type wavelength separation element having a transmittance or a reflectance depending on a wavelength is used as the wavelength separation element. 4. A laser medium doped with both thorium and holmium, a resonator containing the laser medium, and a switching element for controlling the Q of the resonator with respect to light of a wavelength exclusively excited by thorium ions. Laser device. 5. The laser device according to claim 4, wherein the resonator is a resonator highly reflective of thorium ions.