JP2011155193A - Co2 gas laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CO<SB>2</SB>laser amplifier for breaking the limit of a conventional example in the value of optical energy extractable in principle because a conventional CO<SB>2</SB>laser amplifier is small in optical energy extractable in principle. <P>SOLUTION: An angle formed by the direction of an optical axis of a CO<SB>2</SB>laser beam to be amplified and the flow direction of forced convection of a CO<SB>2</SB>laser gas is determined by a discharge cross-sectional area and discharge length of a space where the CO<SB>2</SB>laser gas is subjected to discharge excitation, and the direction of the optical axis of the CO<SB>2</SB>laser beam to be amplified and the flow direction of the forced convection are set as different directions, and an angle between these two directions is larger than a predetermined angle determined by the discharge cross-sectional area and the discharge length. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a pulse laser technology in a gas laser apparatus using a CO ₂ laser gas.

A pulse width less than 100ns of short pulse CO ₂ laser amplifier, CO ₂ laser amplifier for cooling by forced convection a CO ₂ laser gas is continuously (CW) discharge excitation laser the direction of gas flow by forced convection amplifies The direction was substantially the same as the optical axis of the light (see, for example, Patent Document 1). That is, conventionally, a high-speed axial flow type carbon dioxide laser has been used as the carbon dioxide laser (see, for example, Non-Patent Document 1).

In the high-speed axial flow type carbon dioxide laser, the laser gas is excited in a cylindrical discharge tube. Laser gas is flowed from one end of the cylindrical tube to the other end. The optical axis of the laser light also flows along the central axis of the cylindrical tube. That is, the laser gas flow direction and the optical axis direction are parallel to each other. The direction of the laser gas flow refers to a direction in which most of the laser gas flows in the laser gas existing in the discharge region determined by the shape of the discharge electrode. Hereinafter, unless otherwise specified, the direction of gas flow represents this meaning.

In order to use a carbon dioxide laser as an amplifier, the resonator mirror may be replaced with a window. That is, the laser output from the oscillator is amplified by the laser gas excited in the amplifier. The laser gas cools the CO ₂ laser gas by forced convection, and the direction of the gas flow by forced convection is substantially the same as the optical axis of the laser beam to be amplified.

In Patent Document 1, a pulse CO ₂ laser having an output of 10 W is arranged in an oscillation stage, and two CW (continuous wave) -CO ₂ lasers are arranged in an amplification stage. The pulsed CO ₂ laser in the oscillation stage can generate pulsed light at a high repetition frequency (for example, 100 kHz). In this example, the pulsed CO ₂ laser in the oscillation stage operates in a transverse mode and a single mode, and generates a laser beam having a wavelength in the vicinity of 10 μm. Low-power pulse light incident on the CW-CO ₂ laser at the amplification stage from the pulse CO ₂ laser at the oscillation stage travels through the carbon dioxide laser and is amplified, and a laser beam with high condensing performance and high energy is amplified. Output from the stage CW-CO ₂ laser.

Also, when used as an oscillator, two lasers with a rating of 5 kW and one laser with a rating of 15 kW are connected in series and amplified, and when a pulse laser with an average input of 10 W and a pulse width of 15 ns is amplified, It is shown that the average output is about 2 kW (see, for example, Non-Patent Document 2).

JP 2003-92199 A

Igor V. Foendov, et al. , Proceedings of the SPIE, Volume 6517, 65173J, 2007, Section 2 Tatsuya Ariga, et al. Proceedings of the SPIE, Volume 6151, 61513M, 2007, Section 3.2

The conventional CO ₂ laser amplifier has a problem that the amplification factor of the pulse laser is small. An object of the present invention is to provide a CO ₂ laser device having a high amplification factor of a pulse laser. Specifically, when used as an oscillator, an amplifier of the present invention is configured by using one CO ₂ laser having a rated output of about 5 kW, and a pulse laser having a pulse width of about 10 ns, a repetition frequency of 100 kHz, and an average output of 10 W. It is an object of the present invention to provide a device whose average output of amplified pulses exceeds 2 kW.

Further, in the conventional amplifier, since the laser gas flow is substantially parallel to the optical axis direction, the laser gas flows along the long side of the discharge region due to the laser gas flow, so that the laser gas is easily heated. In a typical case, there is a laser gas temperature increase of about 100 degrees.

Accordingly, in the present invention, in order to suppress the temperature rise of the laser gas, a CO ₂ gas laser device that amplifies CO ₂ laser light that repeatedly oscillates with a short pulse with a pulse width of 100 ns or less and cools the CO ₂ laser gas. , determined by the angle between the direction and the CO ₂ flow direction of the forced convection of the laser gas of the optical axis of the CO ₂ laser beam to the amplifier, the discharge cross-sectional area of the space above CO ₂ laser gas is discharge excitation and the discharge length It was set as the structure to do.

In particular, in the present invention, the direction of the optical axis of the CO ₂ laser light to be amplified and the direction of the forced convection flow are set to different directions of a predetermined angle or more determined by the discharge cross-sectional area and the discharge length. The laser gas flows along the short side of the discharge region (the guideline for the flow along the short side is that the length of the laser gas crossing the discharge region is smaller than the third root of the volume of the discharge region). As compared with the above, the rise in the laser gas temperature is suppressed (the temperature rise is estimated to be several tens of degrees).

Small signal gain of a laser medium (small signal gain is an amplification factor per unit length when the input is close to zero. For example, a kW class laser is used to amplify a 10 W laser as in the text. In that case, the magnitude of the amplification factor can be considered to be determined by the magnitude of the small signal gain.) Is inversely proportional to the medium gas temperature to the power of 2.5. As shown in "Research on CO2 laser excitation" (1991 Nagoya University doctoral dissertation), it is desirable that the temperature rise be small.

In the present invention, as described above, the direction of the optical axis of the CO ₂ laser light to be amplified and the flow direction of the forced convection are set to different directions of a predetermined angle or more determined by the discharge cross-sectional area and the discharge length. By suppressing the temperature rise of the laser gas, the amplification factor is large (for example, when used as an oscillator, the amplifier of the present invention is configured using a CO ₂ laser medium having an output of about 5 kW at the maximum, and the pulse width is on the order of 10 ns. An object of the present invention is to provide a CO ₂ gas laser device in which when a pulse laser having a repetition frequency of 100 kHz and an average output of 10 W is amplified, the average output of the amplified pulses exceeds 2 kW.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide an apparatus with a large amplification factor of a pulse laser. For example, when an appropriate resonator mirror is attached and used as an oscillator, the amplifier of the present invention is configured using a CO ₂ laser medium having a rated output of about 5 kW, a pulse width of about 10 ns, a repetition frequency of 100 kHz, and an average output When a 10 W pulse laser is amplified, there is an effect that the average output of the amplified pulses can exceed 2 kW.

1 is a perspective view of a pulse CO ₂ laser amplifier according to a first embodiment of the present invention. It is a functional part illustration of the pulsed CO ₂ laser amplifier of the first embodiment of the present invention. Is a perspective view showing an example of a typical pulsed CO ₂ laser amplifier. It shows a comparison of the laser gas temperature rise in the case of using a pulsed CO ₂ laser amplifier of the prior art and the present invention. It is a perspective view of a pulsed CO ₂ laser amplifier of the second embodiment of the present invention. It is a functional part illustration of the pulsed CO ₂ laser amplifier of the second embodiment of the present invention. It is another illustration of the functional portion of the pulse CO ₂ laser amplifier of the second embodiment of the present invention. It is a block diagram showing an example of a pulse CO ₂ laser amplifier system according to the third embodiment of the present invention. Is a block diagram showing an example of a pulse CO ₂ laser amplifier system according to Embodiment 4 of the present invention.

Embodiment 1 FIG.
A perspective view of the pulsed CO ₂ laser amplifier of the present invention is shown in FIG.
In FIG. 1, the discharge electrode is composed of an upper discharge electrode 11a and a lower discharge electrode 11b. Duct and window holders 15a and 15b are attached to the upper discharge electrode 11a and the lower discharge electrode 11b. A duct 16b is attached to the duct / window holder 15b, a heat exchanger 14 is attached to the duct 16b, a blower 13 is attached to the heat exchanger 14, and a duct 16a is attached to the blower 13. Further, a pulse input side window 12a is attached to the duct / window holder 15a, and a pulse output side window 12b is attached to the duct / window holder 15b.
In FIG. 1, the laser gas is excited to be substantially continuous (CW) in a discharge region determined by the pair of discharge electrodes 11a and 11b. The discharge excitation is performed by applying an AC voltage between the discharge electrodes 11a and 11b.

The pulse CO ₂ laser amplifier of the present embodiment amplifies a pulse CO ₂ laser having a pulse width on the order of 10 ns. In FIG. 1, the laser gas is discharged in a substantially continuous (CW) manner in a discharge region determined by the pair of discharge electrodes 11a and 11b. The discharge excitation is performed by applying an AC voltage between the discharge electrodes 11a and 11b.
When the laser gas is excited by discharge, the temperature rises due to collisions between molecules and electrons. In order for the laser to operate normally, it is necessary to keep the temperature of the laser gas below a certain temperature. Therefore, the laser gas is circulated by forced convection by the function of the blower 13 and is cooled by the heat exchanger 14. The forced convection flow paths are duct and window holders 15a and 15b and ducts 16a and 16b, and the laser gas sent out from the blower 13 is a discharge determined by the inside of the duct 16a, the duct and window holder 15a, and the discharge electrodes 11a and 11b. The structure returns to the blower 13 through the region, the duct / window holder 15b, the inside of the duct 16b, and the heat exchanger 14 in this order.
The pulse input side window 12a is held in the duct / window holder 15a, and the pulse output side window 12b is held in the duct / window holder 15b.

The laser gas is sealed at a pressure of about 50 Torr in a space closed by the blower 13, the heat exchanger 14, the discharge electrodes 11a and 11b, the ducts 16a and 16b, the window holders 15a and 15b, and the windows 12a and 12b.
In this embodiment, the direction of forced convection gas flow in the discharge excitation space is different from the optical axis (traveling direction) of the amplified laser beam.

In the thus configured pulse CO ₂ laser amplifier, pulse CO ₂ laser having a pulse width of 10ns order have been introduced into the discharge region which is determined by the discharge electrodes 11a, 11b through the window 12a. The pulse laser is amplified in the discharge region and then extracted through the window 12b.

Now, in the pulse CO ₂ laser amplifier configured as described above, it is possible to suppress an increase in laser gas temperature as compared with a conventional amplifier. The reason for this will be described below.

The periphery of the discharge region of the amplifier of the present invention (see FIG. 1) is clearly shown in FIG. 2, and the length and area are defined. That is, regarding the discharge region, the length in the optical axis direction (discharge length) is L, the cross-sectional area perpendicular to the optical axis, that is, the area of the discharge cross-section (same as the discharge cross-sectional area), S _D , _r , S is the area of the gas flow path cross section of the laser gas flow, and θ is the angle formed by the optical axis (here, the optical axis direction) and the gas flow (here, the direction of the laser gas flow).

Hereinafter, in the configuration of the present invention and the conventional configuration, the temperature rise of the laser gas when the same discharge power W _di is input to the region where the laser beam is amplified will be compared.
First, in the case of the configuration of the present invention. In FIG. 2, it is considered that the discharge power of W _di is input to a region where the laser beam is amplified (a laser beam cross-sectional area S _r × cylinder region having a discharge length L). In this figure, the area of the discharge cross section is S _D and the area of the gas flow path cross section is S. In order to ensure a gas flow path that is as efficient as possible, the discharge space has a rectangular parallelepiped shape, and as a case for efficient amplification without wasting discharge power, the diameter of the circular laser beam is the length of the side of the discharge cross section. Considering the operation in the almost equal state, that is, the laser beam cross-sectional area: S _r ≈ (π / 4) × discharge cross-sectional area S _D , the following discussion will be made.

In order to perform efficient amplification without wasting discharge power, the closer the volume of the laser beam in the discharge space is to 100%, the better the condition. If the laser beam is a quadrangle that coincides with the discharge cross section, the volume of the laser beam occupying the discharge space is 100%, and the discharge power is not wasted most.

However, on the other hand, since an expensive optical system is necessary to make the circular laser beam emitted from the oscillator into a quadrangle, it is not realistic to amplify the quadrangle laser beam. Therefore, as described above, the discussion proceeds under the condition that the volume of the laser beam occupying the discharge space becomes maximum under the circular condition of the laser beam.

If the discharge power supplied to the entire discharge space (discharge cross-sectional area S _D × rectangle of discharge length L) is W _d , a uniform discharge field is formed in the discharge space in laser discharge,
W _di = (π / 4) × W _d (Formula 1)
It is.

とすると、一般に

が成り立つ。 Further, the gas flow rate is Q [m ³ / s], the gas volume specific heat is C [J / m ³ K], and the gas temperature rises when passing through the discharge field.

Then, in general

Holds.

である。 Furthermore, regarding the gas flow rate, Q = Sv (Formula 3)
(S is the cross-sectional area of the gas flow path [m ² ], v is the gas flow velocity [m / s]). Also,
S = sqrt (S _D ) Lsin θ (Formula 4)
(Sqrt () means a square root. The same applies hereinafter.) From (Formula 1) (Formula 2) (Formula 3) (Formula 4), the gas temperature rise is

It is.

On the other hand, in the example of the conventional general amplifier shown in FIG. 3, the discharge power of W _di is input to the region (laser beam cross-sectional area S _r × discharge length L cylinder) where the laser beam is amplified as described above. think of. In this figure, the cross-sectional area S of the gas flow path cross section is equal to the discharge cross-sectional area _SD and substantially equal to the laser beam cross-sectional area _Sr.

As a case for performing amplification as efficiently as possible, a state in which a circular laser beam substantially coincides with the discharge cross section, that is, a state of S _r = _SD , will be discussed below.
If the discharge power supplied to the entire discharge space (discharge cross-sectional area S _D × discharge length L cylinder) is W _d ,
W _di = W _d (Formula 6)
It is.

は同様に成立し、ガス流量に関しては、レーザガス流が光軸方向とほぼ平行に放電管内を流れるため、
Ｑ＝Ｓｖ＝Ｓ_Ｄｖ （式３ａ）
となる。 Also,

Is established in the same way, and with regard to the gas flow rate, since the laser gas flow flows in the discharge tube substantially parallel to the optical axis direction,
Q = Sv = S _D v (Formula 3a)
It becomes.

である。 From (Formula 6) (Formula 2) (Formula 3a), the gas temperature rise is

It is.

The graph of FIG. 4 shows the conventional gas temperature increase (Formula 7) and the gas temperature increase of the present invention (Formula 5). Comparing the gas temperature rise of the conventional example (Formula 7) and the gas temperature rise of the present invention (Formula 5), the laser gas flow path is shifted in the direction different from the amplified laser beam by the angle shown in the following (Formula 8) For example, the increase in the laser gas temperature when the same discharge power as in the conventional example is input to the region where the laser beam is amplified can be made smaller than that in the conventional example (see FIG. 4).
θ ≧ arcsin (4 / π × sqrt (S _D ) / L) (Formula 8)

The small signal gain of the laser medium is inversely proportional to the medium gas temperature to the power of 2.5 (see Non-Patent Document: Dr. Masaki Kuzumoto, "Study on CO2 Laser Excitation by High Frequency Silent Discharge" (1991 Nagoya University Doctoral Dissertation)) Therefore, according to the present invention, a pulse CO ₂ laser amplifier having a large small signal gain of the laser medium can be provided. In the configuration of the present invention, the small signal gain is about 3 (1 / m).

As an example, when an amplifier of the present invention is configured using a CO ₂ laser medium having a maximum output of about 5 kW when used as an oscillator, a pulse laser having a pulse width of about 10 ns, a repetition frequency of 100 kHz, and an average output of 10 kW is amplified. The output is increased by 4 kW by the amplifier, and the average output of the amplified pulse is 14 kW.

When the discharge cross-sectional area S _D = 5 cm × 5 cm and the discharge length L = 20 cm, the angle θ formed by the forced convection gas flow direction and the optical axis (traveling direction) of the amplified laser beam should be 19 degrees or more. For example, the pulse CO ₂ laser amplifier is superior in amplification performance than the conventional technology. Further, when θ is 90 degrees, the most effective effect is obtained.

Embodiment 2. FIG.
The second embodiment will be described below with reference to FIG.
The pulse CO ₂ laser amplifier according to the _second embodiment amplifies a pulse CO ₂ laser having an average output of 10 W and a pulse width of 10 ns. In FIG. 5, the discharge electrode is composed of an upper discharge electrode 21a and a lower discharge electrode 21b. Duct and window holders 25a and 25b are attached to the upper discharge electrode 21a and the lower discharge electrode 21b. A duct 26b is attached to the duct / window holder 25b, a heat exchanger 24 is attached to the duct 26b, a blower 23 is attached to the heat exchanger 24, and a duct 26a is attached to the blower 23. Further, a pulse input side window 22a and a mirror 27a are attached to the duct / window holder 25a, and a pulse output side window 22b and a mirror 27b are attached to the duct / window holder 25b.

In FIG. 5, the discharge electrodes 21a and 21b, the windows 22a and 22b, the blower 23, the heat exchanger 24, the duct / window holders 25a and 25b, and the ducts 26a and 26b are the same as those in the first embodiment, and thus the description thereof is omitted. . The mirrors 27a and 27b are installed to turn back the path of the pulse laser beam introduced into the discharge region between the discharge electrodes 21a and 21b.
Also in the second embodiment, the direction of forced convection gas flow is different from the optical axis (traveling direction) of the amplified laser beam.

In the thus configured pulse CO ₂ laser amplifier, pulse CO ₂ laser having a pulse width of 10ns order is introduced into the discharge region through the window 22a. The pulse laser is sequentially folded by the mirrors 27a and 27b, and travels along a Z-shaped path. While the pulsed CO ₂ laser travels along the Z-type path, it is amplified in the discharge region between the discharge electrodes 21a and 21b and then taken out of the housing through the window 22b.

FIG. 7 is a functional explanatory diagram according to the second embodiment of the present invention. The above configuration has an optical path 1 from the window 22a to the mirror 27b, an optical path 2 from the mirror 27b to the mirror 27a, and an optical path 3 from the mirror 27a to the window 22b. In FIG. 7, the thick broken lines or the thick practices indicated by “optical path 1” to “optical path 3” indicate the center line of the laser beam in each optical path, and the thin broken line indicates the laser beam radial position in each optical path (the outer edge of the laser beam region). ). The optical path 1 and the optical path 2 share the same space in the hatched portion, and the optical path 2 and the optical path 3 also have a portion that shares the same space. The optical path 1 and the optical path 3 do not share the same space. In the above configuration, the optical path length corresponding to the hatched portion in each optical path (occupying the hatched portion) is shorter than the optical path length corresponding to the non-hatched portion (occupying the non-hatched portion). Yes. In the above, the optical path length means the length of the center line of the laser beam in each optical path.

In the pulse CO ₂ laser amplifier configured as described above, it is possible to suppress an increase in the laser gas temperature as compared with the conventional amplifier. This will be described below.
The periphery of the discharge region of the amplifier of the present invention (see FIG. 5) is clearly shown in FIG. 6, and the length and area are defined. A cross section obtained by cutting the discharge region along a plane perpendicular to the optical path is shown at the left end of FIG. 6, and a discharge cross section (the area of the discharge cross section is S _D ) and a laser beam cross section (the area of the laser beam cross section is S _r ) are drawn. It was.

In the amplifier of the present invention (see FIG. 6), it is considered that the discharge power of W _di is input to a region where the laser beam is amplified (laser beam cross-sectional area S _r × cylinder of discharge length L × 2). In order to perform stable discharge, the discharge cross section (area S _D ) has a square shape. Further, as a case for performing efficient amplification without wasting discharge power, a state in which a circular laser beam is substantially in contact with the upper and lower ends of the discharge cross section (see FIG. 6), that is, the laser beam cross-sectional area: S _r ≈ Considering the operation at π / 8 × discharge cross-sectional area (discharge cross-sectional area) _SD , the following discussion will be made.

とすると、一般に

が成り立つ。 When the discharge power supplied to the entire discharge space (discharge cross-sectional area S _D × discharge length L cuboid) is Wd, a uniform discharge field is formed in the discharge space in laser discharge,
W _di = (π / 8) × W _d (Formula 1a)
It is. Further, the gas flow rate is Q [m ³ / s], the gas volume specific heat is C [J / m ³ K], and the gas temperature rises when passing through the discharge field.

Then, in general

Holds.

である。 Furthermore, regarding the gas flow rate, Q = Sv (Formula 3)
(S is the cross-sectional area of the gas flow path [m ² ], v is the gas flow velocity [m / s]). Also,
S = sqrt (S _D ) Lsin θ (Formula 4)
It is. From (Formula 1a) (Formula 2) (Formula 4) (Formula 3), the gas temperature rise is

It is.

On the other hand, in the conventional general amplifier example (see FIG. 3), the discharge power of W _di is applied to the region (laser beam cross-sectional area S _r × discharge length L cylinder) where the laser beam is amplified as described above. Think about it. As a case for performing amplification as efficiently as possible, a state in which a circular laser beam substantially coincides with the discharge cross section, that is, a state of S _r = _SD , will be discussed below.

は同様に成立し、ガス流量に関しては、レーザガス流が光軸方向とほぼ平行に放電管内を流れるため、
Ｑ＝Ｓｖ＝Ｓ_Ｄｖ （式３ａ）
となる。 If the discharge power supplied to the entire discharge space (discharge cross-sectional area S _D × discharge length L cylinder) is W _d ,
W _di = W _d (Formula 6)
It is. Also,

Is established in the same way, and with regard to the gas flow rate, since the laser gas flow flows in the discharge tube substantially parallel to the optical axis direction,
Q = Sv = S _D v (Formula 3a)
It becomes.

である。 From (Formula 6) (Formula 2) (Formula 4) (Formula 3a), the gas temperature rise is

It is.

Comparing the gas temperature rise of the conventional example (Formula 7) and the gas temperature rise of this section (Formula 5a), in the configuration of the present invention, the angle θ ≧ arcsin (8 / arcsin (8 / π * sqrt (S _D ) / L) (Formula 8a)
If the direction is different only, the increase in the laser gas temperature when the same discharge power as that in the conventional example is applied to the region where the laser beam is amplified can be reduced.

Since the small signal gain of the laser medium is inversely proportional to the medium gas temperature to the power of 2.5 (Source: Dr. Masaki Kuzumoto, “Research on Carbon Dioxide Laser Excitation by High Frequency Silent Discharge”), the present invention reduces the small signal gain of the laser medium. A large pulse CO ₂ laser amplifier can be provided.

For example, when used as an oscillator, when an amplifier of the present invention is configured using a CO ₂ laser medium having a rated output of about 5 kW, a pulse laser having a pulse width of about 10 ns, a repetition frequency of 100 kHz, and an average output of 10 W is amplified. The average power of the amplified pulses is about 2 kW.

When the discharge cross-sectional area S _D = 5 cm × 5 cm and the discharge length L = 20 cm, the angle θ formed by the direction of forced convection gas flow and the optical axis (traveling direction) of the amplified laser beam is 40 degrees or more. Thus, the pulse CO ₂ laser amplifier has a higher amplification performance than the conventional technique. Further, when θ is 90 degrees, the most effective effect is obtained.

Further, the gain of the amplifier is g ₀ (g ₀ = small signal gain per unit length) × (the laser beam and the medium) at an input with a relatively small power of an average output of 10 W at a pulse width of about 10 ns and a repetition frequency of 100 kHz. The interaction length between the laser beam and the medium can be increased by allowing the laser beam to pass through the different positions of the same medium more than twice. Can be amplified with higher efficiency than the system. That is, the effect of the present invention is that a laser beam having a relatively small power is amplified with higher efficiency than the conventional method in a configuration in which a larger power than the conventional one can be input to the region where the laser beam is amplified.

In the above embodiment, the pulse CO ₂ laser is amplified along the Z-shaped path. However, the pulse CO ₂ laser may be a folded path other than the Z-shaped path. Further, a configuration may be adopted in which a plurality of pulse laser beams are amplified before being incident on the amplifier, and the respective pulse laser beams are amplified in parallel in the amplifier. The same effects as those of the present embodiment can be obtained even with the above-described configuration using a folded path other than the Z-type or the configuration in which the amplifier is amplified in parallel.

Embodiment 3 FIG.
FIG. 8 is a diagram showing an example of a pulsed CO ₂ laser amplification system according to Embodiment 3 of the present invention. In FIG. 8, pulse amplifiers 31 and 32 are the pulse amplifiers described in the second embodiment, and pulse amplifiers 33, 34, and 35 indicate the pulse amplifiers described in the first embodiment.
Average output 10 W, pulse CO ₂ laser pulses CO ₂ laser amplifier 31 having a pulse width 10 ns, the laser beam shaping optical system 36, a pulse CO ₂ laser amplifier 32, the laser beam shaping optical system 37, a pulse CO ₂ laser amplifier 33, the laser The beam shaping optical system 38, the pulsed CO ₂ laser amplifier 34, the laser beam shaping optical system 39, and the pulsed CO ₂ laser amplifier 35 are sequentially amplified to obtain a CO ₂ laser having an average output of 20 kW. The laser beam shaping optical systems 36, 37, 38, and 39 are lasers of optimum sizes described in the first and second embodiments for the subsequent pulse CO ₂ laser amplifiers 32, 33, 34, and 35, respectively. Has the role of supplying a beam.

In the third embodiment, the sizes of the discharge regions of the pulse amplifiers 31, 32, 33, 34, and 35 arranged in each stage are equal. Therefore, when the pulse amplifier of the second embodiment (see FIG. 5) arranged at the front stage is compared with the pulse amplifier of the first embodiment (see FIG. 1) arranged at the rear stage, the apparatus of the second embodiment is implemented. Compared to the apparatus of aspect 1, the cross-sectional area of the laser beam is ¼, and the interaction length of the laser beam and the medium (discharge excitation laser gas) is about three times.
That is, if it is considered that the laser beam having the same power is amplified in the first or second embodiment, the light intensity of the laser beam is higher in the apparatus of the second embodiment than in the apparatus of the first embodiment. The interaction length of the laser beam and the medium (discharge excitation laser gas) is about 3 times.

In the first embodiment and the second embodiment, the saturation intensity is on the order of 1 kW. Therefore, when a pulse with an average output of 10 W order sufficiently lower than the saturation intensity is amplified, the saturation of the gain is almost negligible. The device of the second embodiment, whose interaction length is about three times longer than that of the first device, has a gain several times higher.

On the other hand, when a laser beam having a power equal to or greater than the saturation intensity is amplified, the effect of gain saturation is significant, and the amplification factor of the apparatus of the first embodiment is several times higher.
In the present embodiment, the pulse amplifier according to the second embodiment suitable for the amplification performance of the laser beam with the output number of 10 W class is preceded by the pulse amplifier according to the first embodiment suitable for the amplification performance of the laser beam with the output number of kW class. An amplifier is arranged in the subsequent stage to improve the efficiency of the entire amplification system.

In this embodiment, the amplification system is configured by five units in series. However, if the amplifier is configured by connecting two or more amplifiers including the amplifier of the first embodiment or the second embodiment in series, Similar effects can be achieved.

Embodiment 4 FIG.
FIG. 9 is a diagram showing an example of a pulsed CO ₂ laser amplification system according to Embodiment 4 of the present invention. In FIG. 9, pulse amplifiers 31, 32, 41, and 42 are the pulse amplifiers described in the second embodiment, and pulse amplifiers 33, 34, 35, 43, 44, and 45 are the pulse amplifiers described in the first embodiment. Show.
A pulse CO ₂ laser having an average output of 10 W and a pulse width of 10 ns is incident on the beam splitter 30 and is split into _two laser beams having an output of 5 W. One of the two laser beams is a pulse CO ₂ laser amplifier 31, a laser beam shaping optical system 36, a pulse CO ₂ laser amplifier 32, a laser beam shaping optical system 37, a pulse CO ₂ laser amplifier 33, a laser. The beam shaping optical system 38, the pulsed CO ₂ laser amplifier 34, the laser beam shaping optical system 39, and the pulsed CO ₂ laser amplifier 35 are sequentially amplified to obtain a CO ₂ laser having an average output of about 20 kW. Of the two laser beams, the other laser beam includes a pulse CO ₂ laser amplifier 41, a laser beam shaping optical system 46, a pulse CO ₂ laser amplifier 42, a laser beam shaping optical system 47, and a pulse CO ₂ laser amplifier 43. The laser beam shaping optical system 48, the pulsed CO ₂ laser amplifier 44, the laser beam shaping optical system 49, and the pulsed CO ₂ laser amplifier 45 are sequentially amplified to obtain a CO ₂ laser having an average output of about 20 kW. Laser beam shaping optics 36, 37, 38, 39 each follows a subsequent pulse CO ₂ laser amplifier 32, 33, 34, 35, and laser beam shaping optics 46, 47, 48, 49 each follows. The pulse CO ₂ laser amplifiers 42, 43, 44, and 45 have a role of supplying the laser beam having the optimum diameter described in the first and second embodiments.

In the fourth embodiment, all the discharge areas of the pulse amplifiers 31, 32, 33, 34, 35, 41, 42, 43, 44, 45 arranged in each stage have the same size. . Therefore, when the pulse amplifier of the second embodiment (see FIG. 5) arranged at the front stage is compared with the pulse amplifier of the first embodiment (see FIG. 1) arranged at the rear stage, the apparatus of the second embodiment is implemented. Compared to the apparatus of aspect 1, the cross-sectional area of the laser beam is ¼, and the interaction length of the laser beam and the medium (discharge excitation laser gas) is about three times.
That is, if it is considered that the laser beam having the same power is amplified in the first or second embodiment, the light intensity of the laser beam is higher in the apparatus of the second embodiment than in the apparatus of the first embodiment. The interaction length of the laser beam and the medium (discharge excitation laser gas) is about 3 times.

In the first embodiment and the second embodiment, the saturation intensity is on the order of 1 kW. Therefore, when a pulse with an average output of 10 W order sufficiently lower than the saturation intensity is amplified, the saturation of the gain is almost negligible. The device of the second embodiment, whose interaction length is about three times longer than that of the first device, has a gain several times higher.

On the other hand, when a laser beam having a power equal to or greater than the saturation intensity is amplified, the effect of gain saturation is significant, and the amplification factor of the apparatus of the first embodiment is several times higher.
In the present embodiment, the pulse amplifier according to the second embodiment suitable for the amplification performance of the laser beam with the output number of 10 W class is preceded by the pulse amplifier according to the first embodiment suitable for the amplification performance of the laser beam with the output number of kW class. An amplifier is arranged in the subsequent stage to improve the efficiency of the entire amplification system.

In this embodiment, although not shown in FIG. 9, the laser beam of one oscillator that generates pulse laser light before amplification in FIG. 9 is divided and amplified in parallel. One. On the other hand, when two sets of the system of the third embodiment are prepared, two oscillators are required. In this embodiment, the output is the same as when two systems of the third embodiment are prepared, that is, two laser beams of about 20 kW, and the oscillator is compared with two systems of the third embodiment. Obtained with one less configuration. Since an oscillator includes an optical crystal, it is more expensive than an amplifier. In the present embodiment, an inexpensive system can be provided as compared with the case where two systems of the third embodiment are prepared.

In this embodiment, the amplification system is configured by 5 series × 2 parallel, but two or more amplifiers including the amplifier of Embodiment 1 or Embodiment 2 are connected in series or in parallel. A configured amplifier can produce the same effect.

DESCRIPTION OF SYMBOLS 1 Discharge tube, 6a, 6b Discharge electrode, 11a, 11b Discharge electrode, 12a, 12b Window, 13 Blower, 14 Heat exchanger, 15a, 15b Duct and window holder, 16a, 16b Duct, 21a, 21b Discharge electrode, 22a, 22b Window, 23 Blower, 24 Heat exchanger, 25a, 25b Duct and window holder, 26a, 26b Duct, 27a, 27b Mirror, 29a, 29b Discharge electrode, 30 Beam splitter, 31, 32, 33, 34, 35, 41 , 42, 43, 44, 45 Pulse CO ₂ laser amplifier, 36, 37, 38, 39, 46, 47, 48, 49 Laser beam shaping optical system.

Claims (6)

A CO ₂ gas laser device that amplifies CO ₂ laser light that repeatedly oscillates with a short pulse with a pulse width of 100 ns or less, and cools the CO ₂ laser gas by circulating the CO ₂ laser gas excited by continuous discharge by forced convection. In things,
The angle between the direction and the CO ₂ flow direction of the forced convection of the laser gas of the optical axis of the CO ₂ laser beam to the amplifier, the CO ₂ laser gas is determined by the discharge cross-sectional area of the space to be discharged excited discharge length A CO ₂ gas laser device. The direction of the optical axis of the CO ₂ laser light to be amplified and the direction of the flow of forced convection are different directions of a predetermined angle or more determined by the discharge cross-sectional area and the discharge length. The CO ₂ gas laser device described in 1. The said predetermined angle is arcsin (4 / (pi) * sqrt ( _SD ) / L), when the said discharge cross-sectional area is _{SD and the} said discharge length is L, It is characterized by the above-mentioned. CO ₂ gas laser device. The predetermined angle is, the discharge cross-sectional area of _{S D,} when the above discharge length is L, according to claim 2, characterized in that the _{arcsin (8 / π × sqrt (} S D) / L) CO ₂ gas laser device. The CO ₂ laser light passes through the CO ₂ laser gas at least twice, and the optical path of the laser light passes through two or more optical paths whose optical path length overlapping with other optical paths is shorter than optical path length not overlapping with other optical paths. The CO ₂ gas laser device according to claim 1 or 2, wherein the CO ₂ gas laser device is included. The CO ₂ gas laser device according to claim 1 or 2, wherein two or more amplifiers are connected in series or in parallel, or connected in a combination of series and parallel.

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