JPH0666494B2 - Metal vapor laser oscillation method for refractory metals - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for oscillating a metal vapor laser of a high melting point metal by vaporizing a high melting point metal such as vanadium or tantalum to oscillate a metal vapor laser.

[0002]

2. Description of the Related Art Conventionally, as a metal vapor laser for vaporizing a metal to optically excite the metal atom, one using mercury, copper or titanium as a metal is known.

By the way, techniques for vaporizing refractory metals such as vanadium and tantalum (hereinafter simply referred to as refractory metals) include sputtering for producing a thin film and a hollow cathode discharge lamp used for atomic absorption spectrometry.

However, as the oscillation technique of the metal vapor laser of these refractory metals, the fixed idea that the boiling point of the metal is high and metal vapor cannot be easily produced, and the difficulty of predicting a concrete method for photoexcitation. Therefore, there is still no one that optically excites the metal vapor of these refractory metals to cause laser oscillation.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method capable of laser-oscillating a metal vapor of a high melting point metal by optically exciting the metal vapor of a high melting point metal.

[0006]

According to a first aspect of the present invention, there is provided a metal vapor laser oscillation method for a refractory metal, wherein the refractory metal is vaporized to produce a metal vapor, and an excimer laser beam is applied to the metal vapor. Irradiation is used to photoexcite metal atoms.

[0007]

According to the metal vapor laser oscillation method of refractory metal according to claim 1, since the excimer laser beam is irradiated to the metal vapor of the refractory metal, the metal is selected from the excimer laser beams having various wavelengths. Laser light of wavelength and energy suitable for photoexcitation of
It is possible to reliably oscillate the metal vapor of the high melting point metal.

[0008]

EXAMPLES First, the principle of the invention will be described with reference to the case of vanadium as an example of a refractory metal, but the same applies to the case of tantalum as a refractory metal.

Generally, there is a relation of E = h · ν between the energy E and the frequency ν of light, where Planck's constant is h. Based on this relational expression, the ground level E _{1 of} vanadium atom is Energy gap E with excitation level E ₂
Converting _S (see Fig. 1) into the wavelength of light in vacuum, it is 308.2
It is 1 nm (nanometer).

It is predicted that if the vaporized vanadium atom is irradiated with light corresponding to the energy gap E _S , the vaporized vanadium atom may be photoexcited to cause laser oscillation. An XeCl excimer laser beam was found when an excimer laser was investigated for a laser beam having an oscillation wavelength.

Therefore, in practice, the vanadium metal is vaporized, and the vanadium atom vaporized under predetermined conditions is converted into Xe.
Upon irradiation with Cl excimer laser light, vaporized vanadium atoms lased.

In particular, when the vaporized vanadium atom was photoexcited by irradiating it with XeCl excimer laser light with a delay of several microseconds or more immediately after the vaporization of the vanadium atom, a laser oscillation with a good optical amplification factor was obtained.

Next, the outline of the oscillation device of the optically pumped vanadium laser used in the present invention will be described with reference to FIG.

In FIG. 2, 1 is a vapor chamber, 2 is a vapor generating laser device, and 3 is a photoexcitation laser device.

Here, a pulse YAG laser device is used as the vapor generation laser device 2 for generating vanadium vapor, and the pulse width of the YAG laser light is 1.5 ms.
(Milliseconds), oscillation wavelength of YAG laser light is about 1.06 μm
(Micrometer).

The photoexcitation laser device 3 used for photoexcitation of vaporized vanadium atoms is composed of an XeCl excimer laser device, and the laser output of the XeCl excimer laser device is 10 mJ (millijoules), XeCl excimer laser light. Pulse width of 10ns (nanosecond), this XeCl
The oscillation wavelength of the excimer laser light is the same as the absorption wavelength of the vanadium laser light by the YAG laser device which is the vapor generating laser device 2.

The steam chamber 1 is evacuated in advance by a vacuum pump.

Further, a vanadium plate 4 as a refractory metal is provided in the steam chamber 1. The vanadium plate 4 has a purity of 99%.

The vapor chamber 1 is provided with two quartz windows 5 and 6 for irradiating a YAG laser beam and an excimer laser beam, and two brewer windows 7 for outputting a purple vanadium laser beam. , 8 are provided.

The vapor chamber 1 is provided with an optical resonator,
This optical resonator is composed of two plane mirrors 9 and 10. The plane mirror 9 has a reflectance of 100% at a wavelength of 400 nm, and the plane mirror 10 has a reflectance of 90% at a wavelength of 400 nm.

The laser devices 2 and 3 oscillate in response to a trigger signal, which is generated by the pulse generator 11 and supplied to the vapor generating laser device 2.
The signal output as shown and delayed by the delay circuit 12 is supplied to the photoexcitation laser device 3.

The YAG laser light from the laser device 2 is converged by the condenser lens 13 having a focal length of 100 mm, passes through the quartz window 5 and is applied to the vanadium plate 4.

As a result, the vanadium plate 4 is melted and the vanadium atoms forming the vanadium plate 4 are vaporized.

The photoexcitation laser device 3 composed of the XeCl excimer laser device is activated by a trigger pulse after waiting a predetermined delay time set by the delay circuit 12.

XeCl excimer laser light from the photoexcitation laser device 3 is guided to the vapor chamber 1 through the quartz window 6,
Photoexcitation of vaporized vanadium atoms.

That is, as shown in FIG. 1 and described above, the electrons of the vanadium atom are changed from the ground level E ₁ to the excitation level E ₂
And is excited by light. Then, when the excited electrons transit from the excitation level E ₂ to the metastable level E ₃ , the purple vanadium laser light is stimulated and emitted due to resonance.

The wavelength of this vanadium laser light is 409.54
9 nm. Here, the full width at half maximum is about 4ns and the pulse width is 11n.
A vanadium laser beam of s was obtained.

The maximum output of this pulsed laser light is 1.08 W
And the energy was 4.3 nJ.

The output of the vanadium laser light was measured by the spectrum meter 14. The spectrum meter 14 was connected to an oscilloscope 16 via a phototube 15, and the output of the vanadium laser light was measured by the phototube 15.

The gain of this vanadium laser light was about 0.46 / cm under the optimum conditions.

In this case, if the vapor chamber 1 is filled with a small amount of helium gas, the output of vanadium laser light and the optical amplification factor can be increased as shown in FIG.

Further, a laser action at a long wavelength different from the above was investigated by using the oscillation device.

In this investigation, the reflectance of the mirror 9 was set to about 88% in the wavelength range of 400 nm to 700 nm, and the reflectance of the mirror 10 was set to about 90% in the wavelength range of 500 nm to 650 nm. It was set to 3% at 409 nm. This is to facilitate the distinction from the above oscillation.

The irradiation energy of the YAG laser for vapor generation was set to 2.1 J, and the irradiation energy of the XeCl laser was set to about 15 mJ to make the photoexcitation more intense. The helium pressure in the steam chamber 1 was changed in the range of 1 Torr to several tens Torr to investigate the laser oscillation action.

In this investigation, the maximum output of 7.8 W is obtained when the helium in the steam chamber 1 is about 2.4 Torr, and the output of the vanadium laser light with respect to the delay time when the helium pressure is about 2.4 Torr is as shown in FIG. It looks like 4.

In FIG. 4, the wavelengths are 560 nm, 575 nm and 58 nm.
The total output of 2 nm and 638 nm is shown.

Table 3 shows the oscillation wavelength and gain of the vanadium laser of this investigation and the above example. 1
Is like.

This table. The delay time at 1 is 1.3 ms.

(Hereinafter, margin) From the above results, metal vanadium is irradiated with XeCl excimer laser light having a wavelength of about 308 nanometers and photoexcited, so that laser oscillation corresponding to each energy level shown in FIG. 5 is performed. It is a thing.

Next, the case where tantalum is used as the refractory metal will be described.

In this case, the ground level E of the tantalum atom
_When the energy gap E _S between ₁ and the excitation level E ₂ is converted into the wavelength of light in vacuum, it is 248.50 nm (nanometer).

Then, based on the above-mentioned principle, when an excimer laser is investigated for a laser beam having an oscillation wavelength of 248.50 nm, which should be irradiated to vaporized tantalum atoms,
There is KrF excimer laser light.

Therefore, as in the case of vanadium,
By vaporizing tantalum as a refractory metal and irradiating it with KrF excimer laser light, vaporized tantalum atoms can be oscillated.

A laser oscillation device for such tantalum may be constructed in substantially the same manner as the oscillation device of the optically pumped vanadium laser shown in FIG. 2, and the KrF excimer laser device is used as the optically excited laser device. Good.

That is, in the oscillation device, the mirror 9 has a reflectance of 88% in the wavelength range of 290 nm to 390 nm, and the mirror 10 has a reflectance of 90% in the same wavelength range. The pressure of helium in the steam chamber 1 is 2.4 Tor
r, a KrF excimer laser device is used as the photoexcitation laser device 3, and a tantalum plate is used in place of the vanadium plate 4.

The output of the tantalum laser beam by such an oscillating device is as shown in FIGS. 8 and 9.

As shown in FIG. 8, the output of the tantalum laser with respect to the output of the YAG laser of the vapor generating laser device 2 increases up to 2 J with respect to the increase of the output of the YAG laser, but does not increase further. Is.

The output of the tantalum laser with respect to the output of the KrF excimer laser light of the photoexcitation laser device 3 increases as the output of the KrF excimer laser increases as shown in FIG. .

From the above, the output of this tantalum laser was investigated by setting the output of the YAG laser of the vapor generating laser device 2 to 2 J and the KrF of the photoexcitation laser device 3.
The excimer laser output was 10 mJ.

The state of the tantalum laser output under these conditions is shown in FIG. 6 against the delay time. The maximum output of this tantalum laser has a delay time of 1.
It is about 47W in 3ms.

The output of the tantalum laser shown in FIG.
It is shown as the total laser output of each wavelength in the following table, and the gain of the laser of each wavelength is as follows.

[0052] From the above results, tantalum was irradiated with KrF excimer laser light having a wavelength of about 249 nanometers and photoexcited, whereby laser oscillation corresponding to each energy level shown in FIG. 7 was performed. It is a thing.

In laser oscillation of a metal vapor of a refractory metal such as vanadium or tantalum, the temperature of the metal vapor is high, so that the Doppler width related to absorption is wide and the wavelength of the excitation laser beam is slightly shifted. There is an advantage that it can be excited even if there is.

Further, although excimer laser light is used to excite the vapor of refractory metal, the excimer laser has a wide wavelength range and high output, so that a laser suitable for the type of refractory metal is used. Light can be selected, and the vapor of refractory metal vapor can be easily excited.

Although the embodiments have been described above, sputtering, electron beam, a high power laser such as a YAG laser, a hollow cathode discharge, or the like can be used as a means for generating vanadium or tantalum vapor. In addition,
When a high-power laser is used, the high-power laser light is divided into several laser lights and the spots of the divided laser lights are irradiated so as to be linear on the vanadium plate 4 or the tantalum plate, whereby these high melting points It is also possible to reliably vaporize the metal.

[0056]

As described above, according to the metal vapor laser oscillation method of refractory metal according to the first aspect, excimer laser light is irradiated to the metal vapor of refractory metal.
It is possible to select a laser beam having a wavelength and energy suitable for photoexcitation of the metal from excimer laser beams having various wavelengths, and it is possible to reliably oscillate a metal vapor of a refractory metal. .

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a schematic diagram of an oscillation device of an optically pumped vanadium laser according to the present invention.

FIG. 3 is an output characteristic diagram of an optically pumped vanadium laser.

FIG. 4 is a state diagram of a vanadium laser output with respect to a delay time.

FIG. 5 is an explanatory diagram of energy level levels related to a vanadium laser.

FIG. 6 is a state diagram of tantalum laser output with respect to delay time.

FIG. 7 is an explanatory diagram of energy level levels related to a tantalum laser.

FIG. 8 is an output state diagram of a tantalum laser with respect to a YAG laser output.

FIG. 9 is an output state diagram of a tantalum laser with respect to a KrF excimer laser output.

[Explanation of symbols]

 1 steam chamber 2 laser device for steam generation 3 laser device for photoexcitation 4 vanadium plate

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 8934-4M H01S 3/23 Z

Claims (6)

[Claims] 1. A metal vapor laser oscillation method for a refractory metal, which comprises vaporizing a refractory metal to generate metal vapor, and irradiating the metal vapor with excimer laser light to photoexcite metal atoms. 2. The metal vapor laser oscillation method for a refractory metal according to claim 1, wherein the wavelength of the excimer laser light corresponds to an energy gap between a ground level and an excitation level of refractory metal atoms. A method for lasing a metal vapor laser of a refractory metal. 3. The metal vapor laser oscillation method for refractory metal according to claim 2, wherein the refractory metal is vanadium, XeCl excimer laser light having a wavelength of about 308 nanometers is used as excimer laser light. A metal vapor laser oscillation method for a refractory metal characterized by being used. 4. The metal vapor laser oscillation method for refractory metal according to claim 2, wherein the refractory metal is tantalum, and the KrF excimer laser light having a wavelength of about 249 nanometers is used as the excimer laser light. A method for lasing a metal vapor laser of a refractory metal. 5. The method for oscillating a metal vapor laser of a refractory metal according to claim 3, wherein the vanadium vapor is irradiated with XeCl excimer laser light in a vacuum or in the presence of a small amount of helium gas. Metal vapor laser oscillation method of melting point metal. 6. The metal vapor laser oscillation method for a refractory metal according to claim 4, wherein the tantalum vapor is irradiated with KrF excimer laser light in a vacuum or in the presence of a small amount of helium gas. Metal vapor laser oscillation method of melting point metal.