JP3061937B2 - Metal vapor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal vapor laser apparatus for generating a metal vapor by discharging and heating a laser medium metal in a buffer gas and exciting the metal vapor to oscillate a laser.

[0002]

2. Description of the Related Art As is well known, lasers are utilized in various fields by utilizing characteristics such as excellent directivity and coherence of laser light. For example, there are applications to laser fusion and laser processing, which focus on high light-collecting properties and high energy densities.On the other hand, in recent years, attention has been focused on monochromaticity of laser light to selectively excite only the target substance, Utilization for high purification and removal of impurities is also being promoted.

Hereinafter, a metal vapor laser device, which is one type of a laser generator having such excellent characteristics, will be described with reference to FIG.

FIG. 5 shows a conventional metal vapor laser device. In general, a metal vapor laser apparatus 101 has a vacuum vessel 102 in which a buffer gas is sealed.
Inside 2, a heat insulating material 103 and a plasma tube 104 are arranged, and are formed in a substantially cylindrical shape as a whole. Discharge electrodes 105 and 106 are disposed near both ends of the plasma tube 104, and a closed space surrounded by the discharge electrodes 105 and 106 and the plasma tube 104 is a discharge unit 107.

The discharge electrodes 105 and 106 are connected to a pulse high voltage power supply 108 for applying a voltage. In addition, the vacuum vessel 102
Are closed by windows 109 and 110 to keep the inside of the vacuum vessel 102 sealed. Further, a resonator including an output mirror 111 and a total reflection mirror 112 is provided outside the windows 109 and 110. Further, inside the plasma tube 104, metal particles 113 which are a laser medium metal are mounted.

The vacuum vessel 102 has a buffer gas supply device 11
4 and the exhaust device 115 respectively. A buffer gas made of a rare gas such as neon or helium can be supplied into the vacuum vessel 102 by a buffer gas supply device 114. On the other hand, this buffer gas is supplied to the exhaust device 11
5 to be able to discharge.

When laser oscillation is performed by the metal vapor laser device 101, the buffer gas is supplied into the vacuum vessel 102 by the buffer gas supply device 114, and the buffer gas is exhausted from the vacuum container 102 by the exhaust device 115. Then, the discharge electrode 105,
A voltage is applied between 106 and the discharge unit 107 discharges. This discharge heats the plasma tube 104, and at the same time, heats and melts the metal particles 113 placed thereon to generate metal vapor. Then, the metal atoms existing as the vapor are excited by discharging with a voltage applied between the discharge electrodes 105 and 106, and the laser is oscillated using the mirrors 111 and 112 of the resonator.

The metal particles 113 include, for example, gold,
Copper or the like is used. The temperature of the metal particles 113 is 1500 ° C. to 1
Heat to 700 ° C.

[0009]

Incidentally, the laser output or the laser efficiency greatly depends on the temperature of metal particles as a laser medium. The reason why the laser output greatly depends on the temperature of the metal particles is that the density of the metal vapor is determined by the temperature of the metal particles. Therefore, in order to efficiently generate laser light and extract a larger laser output, it is necessary to control the temperature of metal particles so as to optimize the supply of an optimal amount of metal vapor into the plasma. . In order to optimize the temperature of the metal particles, the thermal conductivity of the heat insulating material and the energy input to the plasma are taken into consideration so that the temperature of the plasma tube is optimized. Need to decide.

However, it is difficult to obtain a plasma tube temperature as originally designed even when a predetermined discharge power is applied.
Even if the designed temperature is obtained at the start of laser oscillation, the thermal insulation properties of the heat insulating material change over time due to the effects of heat and electric discharge. Will happen. For this reason, a high-efficiency and high-output laser output cannot be obtained.

Accordingly, an object of the present invention is to provide a metal vapor laser device which facilitates temperature control of metal particles and has high efficiency and high output.

[0012]

According to the present invention, there is provided a vacuum vessel to which a buffer gas is supplied, a discharge electrode disposed in the vacuum vessel, and a method of applying a voltage to the electrode. And a power supply for generating a discharge in a buffer gas by heating the laser medium metal placed in the vacuum vessel by the discharge to generate a metal vapor and exciting the metal vapor to oscillate a laser. In the laser device, buffer gas mixing means for mixing at least two or more gases to generate a buffer gas, temperature measurement means for measuring the temperature of the laser medium metal, and buffer gas based on the measurement result of the temperature measurement means And a means for controlling the mixing means to change the gas mixing ratio.

A vacuum vessel to which the buffer gas is supplied; a discharge electrode disposed in the vacuum vessel; and a power supply for generating a discharge in the buffer gas by applying a voltage to the electrode. In a metal vapor laser device that generates a metal vapor by discharging a laser medium metal mounted on a substrate by discharge and excites the metal vapor to oscillate a laser composed of two or more wavelength components, at least two types of gases are used. , A buffer gas mixing means for generating a buffer gas, a power ratio measurement means for measuring an output ratio of a wavelength component of the laser light, and a buffer gas mixing means based on the measurement result of the output ratio measurement means. And a means for changing the mixing ratio of the buffer gas.

[0014]

According to the present invention constructed as described above, since the discharge buffer gas is composed of two or more types, the plasma resistance can be freely changed by adjusting the mixing ratio of the gases. As a result, the power input into the plasma can be changed.

Most of the electric power supplied to the plasma becomes heat and is stored in the heat insulating material layer. Therefore, by changing the plasma resistance and changing the input power into the plasma, the temperature of the plasma tube, and further, the temperature of the laser medium metal (metal particles) placed in the plasma tube can be adjusted. By measuring the temperature of the laser medium metal and evaluating this temperature and adjusting the mixing ratio of the buffer gas, the density of the metal vapor can be optimized. Therefore, high-efficiency and high-output laser oscillation can be obtained.

There is a certain correlation between the laser output (laser efficiency) and the output ratio of the wavelength component.

For example, in a copper vapor laser using copper as a laser medium, a laser beam is composed of two components of green (511 nm) and yellow (578 nm).
Output ratio of green laser light to yellow laser light (hereinafter, referred to as
FIG. 7 shows a relationship between the “G / Y ratio”) and the laser output. The reason why there is a strong correlation between the laser output and the output ratio of the wavelength component is that the output dependency on the temperature of the metal particles differs depending on the wavelength.

By utilizing such a phenomenon, it is possible to measure the output ratio of the wavelength component of the laser beam and change the mixing ratio of the buffer gas based on the output ratio.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an apparatus configuration diagram showing a metal vapor laser apparatus according to a first embodiment of the present invention.

The metal vapor laser device 1 has a vacuum vessel 2 in which a buffer gas is sealed, in which a heat insulating material 3 and a plasma tube 4 are arranged, and formed as a substantially cylindrical shape as a whole. Have been. The plasma tube 4 is formed of, for example, a heat-resistant ceramic. In addition, the plasma tube 4
Discharge electrodes 5 and 6 are arranged in the vicinity of both ends, and a space surrounded by the discharge electrodes 5 and 6 and the plasma tube 4 is a discharge unit 7. The diameter of the discharge part 7 (the inner diameter of the plasma tube 4)
Here, an 80 mm (cross-sectional area of about 50 cm 2) is used.

The discharge electrodes 5 and 6 are connected to a pulse high voltage power supply 8 for applying a voltage. Further, both ends of the vacuum vessel 2 are closed by windows 9 and 10 to keep the inside of the vacuum vessel 2 in a sealed state. In addition, output mirrors are located outside windows 9 and 10.
A resonator including 11 and a total reflection mirror 12 is provided.
Further, metal particles 13 which are a laser medium metal are placed inside the plasma tube 4. In addition, as the metal particles 13,
For example, gold, copper, or the like is selected, but copper is used here.

The vacuum vessel 2 includes gas supply devices 14a, 14b, 14c
And the exhaust device 15. Here, helium is stored in the gas supply device 14a, neon is stored in the gas supply device 14b, and hydrogen is stored in the gas supply device 14c. Note that neon and helium are rare gases, and hydrogen is a molecular gas. A buffer gas is generated by mixing these gases. Note that the exhaust device 15 is configured by a rotary pump or the like. Gas supply devices 14a, 14
b, 14c are configured to communicate with the gas mixer 17 and
It is connected to the vacuum vessel 2 via 18.

The surface temperature of the metal particles 13 is measured by a temperature measuring device 30 composed of, for example, a radiation thermometer. The measurement signal from the temperature measurement device 30 is sent to the control operation device 31, where a predetermined operation process is performed. Further, the control arithmetic unit 31 outputs a control signal to the gas mixer 17, whereby the gas mixer 17
The mixing ratio of each gas according to 17 can be controlled.

When the laser is oscillated by the metal vapor laser device 1, first, the inside of the vacuum vessel 2 is evacuated, and one or both of the gas supply devices 14a and 14b are controlled to control the vacuum vessel 2.
Noble gas is supplied to the inside. Here, the gas supply device 14c
Valves are closed. And pulse high voltage power supply 8
Thus, a voltage is applied between the discharge electrodes 5 and 6, and discharge is performed in the discharge unit 7. This discharge heats and dissolves the metal particles 13 placed in the plasma tube 4 to generate metal vapor. Then, the metal atoms existing as the vapor are excited by electric discharge to generate light. The generated light is amplified by the output mirror 11 and the total reflection mirror 12, and the output mirror 11 emits a laser beam L.

In the present invention, the surface temperature of the metal particles 13 is measured by the temperature measuring device 30 while the laser L is oscillating. The measurement results are sequentially output to the control operation device 31. For example, the relationship between the temperature and the output as shown in FIG. And the actually measured surface temperature t1 of the metal particles 13 and the optimum temperature
If a deviation from t is found, a control signal is output to the gas mixer 17 to instruct the gas mixer 17 to adjust the gas mixing ratio to increase the surface temperature of the metal particles 13 to t. Gas mixer
Numeral 17 adjusts the gas mixture ratio by controlling the amount of opening and closing of the valves of the gas supply devices 14a and 14b and the gas supply device 14c.

According to the present invention having such a configuration, it is possible to easily change the discharge resistance by adjusting the mixing ratio of the gases, utilizing the fact that the discharge resistance differs depending on the type of gas. By changing the discharge resistance, the metal vapor density in the plasma is optimized, so that the temperature cannot be obtained as designed when the device is designed, or the heat insulating properties of the heat insulating material change over time due to the effects of heat and discharge. Even with this, it is possible to obtain a laser output with high efficiency and high output.

According to actual experiments, it was particularly effective to mix a small amount of a molecular gas such as hydrogen with a rare gas such as neon or helium as a buffer gas.
This is because the molecular gas has an extremely low vibrational excitation level as compared with the excitation energy level of a rare gas or metal atom. As a result, even if a small amount of the molecular gas is mixed, the electron temperature of the plasma is reduced, and the discharge resistance is increased as compared with the case where the buffer gas is composed of only a rare gas.

However, if the mixing amount of the molecular gas is increased too much, the electrons do not have enough energy to excite the metal vapor, which has the opposite effect. According to the experimental results, the mixing ratio of hydrogen, which is a molecular gas, is preferably set to 0.1% to 4.0% with respect to the total gas pressure, and particularly preferably in the range of 1.0% to 1.5%. It turned out to be optimal.

It is not necessary to constantly monitor the temperature of the metal particles 13, and it is sufficient if the temperature can be measured at least once at a certain time when the laser output is stably obtained. In other words, since the heat insulating property of the heat insulating material 3 is relatively moderate, the temperature is measured and evaluated only once at a certain time when the laser output is stably obtained. By maintaining the mixing ratio, a high laser output can be maintained.

When the laser is oscillated again,
The mixing ratio used during the previous oscillation can be used as it is. Therefore, it is preferable to provide a memory or the like for storing the optimum mixing ratio and the mixing start timing used last time as data and to use the data again next time.

In the above embodiment, the structure for measuring the surface temperature of the metal particles 13 has been described. For example, when the surface temperature of the metal particles 13 is 1400 ° C., the temperature inside the plasma tube 4 is always 1450 ° C. If there is a relationship, the temperature inside the plasma tube 4 (1450 ° C.) may be measured instead of measuring the surface temperature (1400 ° C.) of the metal particles 13. When the metal particles 13 are used in a state of being placed on a container or the like, the surface temperature of the container may be measured.

Next, a second embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description will be omitted.

In a metal vapor laser device using metal particles such as gold or copper as a laser medium metal, laser oscillation of two or more colors occurs. For example, in a copper vapor laser, laser light is green (510.0 nm) and yellow (578.nm). 3 nm). The relationship between the temperature of the metal particles and the output of each component is different for each component of the laser beam.

FIG. 4 shows the correlation between the temperature of metal particles and each component in the case of a copper vapor laser. As is clear from the figure, the output of each component differs depending on the temperature of the metal particles.

FIG. 6 shows the correlation between the G / Y ratios. In the temperature range of 1300 ° C. to 1500 ° C. where laser oscillation occurs, the G / Y ratio has a one-to-one relationship with the temperature of the metal particles. It is possible to know whether it is low or high.

FIG. 3 shows a metal vapor laser device capable of optimizing the temperature by measuring the output ratio of the wavelength components. Here is a metal vapor laser device
21 is characterized in that a laser component measuring means 40 is provided. That is, the laser component measuring means 40 includes the mirror 22 that reflects a part of the laser light transmitted through the mirror 11 and the mirror 22.
A dichroic mirror 23 that reflects only a yellow component of the laser light reflected by 22 and transmits a green component, and detectors 24 and 25 that detect outputs of a green component and a yellow component, respectively.
And a calculator 26 for calculating the output amount of each component detected by the detectors 24 and 25 to obtain the G / Y ratio. Further, the G / Y ratio input from the arithmetic unit 26 is evaluated by the control arithmetic unit 27 and given to the gas mixer 17.
Thereby, the gas mixer 17 controls the opening and closing amounts of the valves of the gas supply devices 14a, 14b and 14c.

As described above, by utilizing the fact that the output ratio of the wavelength component such as the G / Y ratio has a correlation with the temperature, the mixing ratio of the buffer gas is adjusted from the detected output ratio. Since the discharge resistance changes and the metal vapor density in the plasma can be optimized as in the first embodiment, a high-efficiency and high-output laser output can be obtained.

In the second embodiment, the mixing ratio of the buffer gas is adjusted by using the output ratio of the two wavelength components. For example, an arbitrary ratio with respect to the entire laser output (sum of the outputs of the respective wavelength components) is adjusted. A configuration using a ratio of one wavelength component may be used. In the case where there are three wavelength components, the mixing ratio of the buffer gas can be adjusted using the ratio of any two wavelength components.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments.
Various modifications are possible.

For example, in each of the above embodiments, the gas mixer 17 is used to mix the buffer gas and the molecular gas.
It is also possible to mix a gas consisting of a rare gas species alone to form a buffer gas.

As the rare gas, neon, helium or the like can be used. Also, as the molecular gas,
Hydrogen, oxygen, nitrogen, carbon dioxide, carbon monoxide, methane,
Ethane gas, molecular gas containing hydrogen, or the like can be used. Regardless of which of these gases is selected, the same effect as in the above embodiment can be expected.

In addition to copper as the laser medium metal, gold,
The present invention can also be applied to a vapor laser device using metal particles of another element such as strontium.

As shown in FIG. 4, the peak output temperature of the green component is lower than the peak output temperature of the yellow component.
That is, when one component light is required, the temperature of the metal particles may be optimized so that the required component light is maximized. Therefore, the temperature can be optimized by adjusting the mixing ratio of the buffer gas.

The work of measuring the temperature of the metal particles, checking the supply timing of the molecular gas, the work of supplying the molecular gas, and the work of adjusting the gas mixture ratio are not necessarily performed automatically. It is also possible to perform by operation.

Although the discharge portion has a diameter of 80 mm here, it is of course possible to apply a discharge portion having a diameter larger than 80 mm or a diameter smaller than 80 mm. Further, the cross-sectional shape of the discharge portion is not limited to a circle, but may be a polygon.

[0047]

As described above, according to the metal vapor laser apparatus of the present invention, the temperature of the laser medium metal is measured and evaluated, and the mixing ratio of the buffer gas is adjusted to adjust the metal vapor. This makes it possible to optimize the density. Therefore, high-efficiency and high-output laser oscillation can be obtained.

[Brief description of the drawings]

FIG. 1 is a device configuration diagram showing a metal vapor laser device according to a first embodiment of the present invention.

FIG. 2 is a graph showing a correlation between metal particle temperature and laser output.

FIG. 3 is a device configuration diagram showing a metal vapor laser device according to a second embodiment of the present invention.

FIG. 4 is a graph showing a correlation between metal particle temperature and laser output of each component.

FIG. 5 is an apparatus configuration diagram showing a metal vapor laser apparatus according to a conventional technique.

FIG. 6 is a graph showing a correlation between a G / Y ratio and a laser output.

[Explanation of symbols]

 1, 21: Metal vapor laser device 2: Vacuum container 4: Plasma tube 5, 6: Discharge electrode 8: Pulse high voltage power supply 13: Metal particles 14: Buffer gas supply device 16: Molecular gas supply device 17: Gas mixer 30: temperature detector 40: laser component measuring means L: laser beam

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ikuo Watanabe 1 Kosuka Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside Toshiba Research Institute, Inc. Address Toshiba Research Institute Co., Ltd. (72) Inventor Tomoko Ogawa 1 Koga Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Research Institute Co., Ltd. (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 3 / 097 H01S 3/036 H01S 3/227

Claims (3)

(57) [Claims] 1. A vacuum vessel to which a buffer gas is supplied, a discharge electrode disposed in the vacuum vessel, and a power supply for generating a discharge in the buffer gas by applying a voltage to the electrode. In a metal vapor laser device that heats a laser medium metal placed in the vacuum vessel by electric discharge to generate a metal vapor and excites the metal vapor to oscillate a laser, at least two or more gases are mixed. Buffer gas mixing means for generating a buffer gas by heating, a temperature measuring means for measuring the temperature of the laser medium metal, and controlling the buffer gas mixing means based on the measurement result of the temperature measuring means to adjust a gas mixing ratio. A metal vapor laser device, comprising: means for changing. 2. A vacuum vessel to which a buffer gas is supplied, a discharge electrode arranged in the vacuum vessel, and a power supply for generating a discharge in the buffer gas by applying a voltage to the electrode, In a metal vapor laser device which heats a laser medium metal placed in the vacuum vessel by electric discharge to generate a metal vapor and excites the metal vapor to oscillate a laser composed of components having two or more wavelengths, Buffer gas mixing means for mixing at least two kinds of gases to generate a buffer gas; output ratio measurement means for measuring an output ratio of wavelength components of laser light; and a buffer gas based on a measurement result of the output ratio measurement means. Means for controlling the mixing means to change the mixing ratio of the buffer gas. 3. The metal vapor laser device according to claim 1, wherein said at least two kinds of gases include a molecular gas.