JPH065798B2 - Laser amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser amplifier, and more particularly to a laser amplifier in the form of a box-type disk amplifier, in which destruction of a flash lamp due to electromagnetic force generated by current is significantly improved. Regarding

[Conventional technology]

A laser disk glass containing Neodymium (Nd) atoms is placed in the optical path of the laser beam, and the laser disk glass is irradiated with a flash lamp such as a xenon lamp. It is commonly known as an amplifier and is known in comparison with a rod amplifier.

There are also two types of disk amplifiers such as a cylinder type and a box type. The cylindrical type has a cylindrical case as a whole, and both ends of a case are glass windows for inputting and outputting laser light, and a required number of laser disk glasses are arranged inside. The cylinder forms a glass side wall made of quartz glass or the like over a required length, and a required number of flash lamps are arranged at equal intervals and in an equal circle around the glass side wall. However, among these flash lamps, one having a large amount of reactive irradiation energy to the laser disk glass is used as a dummy lamp only for supplying a current in consideration of optimization of electromagnetic force balance described later. The cylindrical dummy lamps have different relative positions of about 180 degrees.
One or two pieces are arranged and used.

On the other hand, the box type is as follows. That is, the case for housing the laser disk glass has a box shape, a window for laser input / output is used for the longitudinal surface, and quartz glass or the like is used for the two side surfaces, that is, the side surfaces parallel to the laser optical path. A shield glass is provided, and the laser disk glass is irradiated with excitation light from a flash lamp through the shield glass. Further, the flash lamps are arranged on the side of the shield glass at equal intervals, and are normally housed in a lamp chamber formed integrally with the case by using the shield glass as one surface thereof. Two dummy lamps are mounted on each side of the flash lamps at the intervals of the flash lamp arrangement from the upper and lower ends.

Such a box-type laser disk glass type laser amplifier has characteristics such as high efficiency and low cost as compared with a cylindrical type laser amplifier of the same type, and has been frequently used recently. These laser amplifiers are used in combination with a spatial filter for laser light that adjusts the beam width of the laser light and a Faraday rotator that gives a predetermined polarization angle to the laser light, etc., and use them in series to obtain the desired laser output. Has been done.

By the way, in a pump-type flash lamp of a disk-type laser amplifier used for such a purpose, an electromagnetic force due to a discharge current is induced, and a box type is a cylindrical type that maintains symmetry of mutual positional relationship. In comparison, the imbalance of the induced electromagnetic force is large.

This electromagnetic force is expressed by the following equation (1) between two adjacent flash lamps i and j, for example.

The parentheses in the equation (1) represent the force per unit length. The electromagnetic force F shown in the equation (1) is reciprocal when the directions of the discharge currents flowing through the two adjacent flash lamps are opposite to each other, and is reciprocal when the discharge currents are in the same direction. To work. Specifically, the magnitude of this electromagnetic force is about 29 when the discharge current is 6000 A (ampere) and the distance between the flash lamp centers is 25 mm due to high power laser amplification or the like.
It becomes 0 N / m (Newton / meter).

An electromagnetic force expressed by the equation (1) is induced between one flash lamp and all the other flash lamps. Therefore, each of the n flash lamps operates while receiving such an electromagnetic force, and there is a risk of destruction depending on its size.

This electromagnetic force appears in the form of repulsion due to the direction of the discharge current and the attractive force canceling each other out. Usually, the beam diameter is 10cm,
In a laser amplifier used to obtain a high-power laser such as several KJ (kilojoules), two flash lamps are used as one unit depending on the power supply conditions, etc. Therefore, the direction of discharge current is different for each flash lamp. It is often used as an inversion. Under such usage, it is clear that the effect of electromagnetic force is much smaller in the case of the cylindrical type in which the positions of the flash lamps are symmetrical to each other than in the box type of the type in which the flash lamps are distributed on two sides. is there.

The above-mentioned dummy lamp is intended to eliminate the destruction and deterioration of the flash lamp due to such electromagnetic force as much as possible, and its usage promotes the canceling effect of the electromagnetic force and balances the electromagnetic force applied to each flash lamp. The effect of is reduced equivalently. As described above, in the box type laser amplifier, dummy lamps are arranged at positions equal to the arrangement intervals of the flash lamps from the upper and lower ends of the flash lamp groups arranged at equal intervals on two planes parallel to each other. We are trying to reduce the influence of electromagnetic force emphasized in the vicinity.

FIG. 5 is an explanatory diagram showing an example of an arrangement of flash lamps of a conventional laser amplifier.

For Figure 5, showing a state in which an even number of 16 flash lamps and four dummy lamps are arranged at equal intervals d _o respectively. When an even number of flash lamps are used as shown in FIG. 5, the central flash lamp cannot be clearly specified by one like 2-8 or 3-8 in FIG. The effect of offsetting the repulsion and the attraction force based on the above is also reduced, and the position of the dummy lamp is not selected to be the minimum electromagnetic force position. Therefore, the effect of the dummy lamp on the reduction of the electromagnetic force is greatly reduced as a whole.

[Problems to be solved by the invention]

However, in such a conventional box type laser amplifier as described above, the dummy lamps for balancing the electromagnetic force are arranged at the same positions as the arrangement intervals of the flash lamps. As you can see
The generated electromagnetic force depends on the distance between the flash lamps if the magnitude and direction of the discharge current are the same, so it is necessary to consider this distance condition in order to reduce the influence of the electromagnetic force. Since the dummy lamps are also arranged at the same array intervals as the flash lamps, the effect on the balance of the electromagnetic force must be extremely insufficient.

The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a means for arranging the dummy lamp at an optimum distance that minimizes the electromagnetic force, thereby greatly reducing the risk of destruction of the flash lamp by the electromagnetic force. To provide a type of laser amplifier.

[Means for solving problems]

The laser amplifier of the present invention is a box-type disk amplifier type laser amplifier, in which an odd number of pumping flash lamps to be arranged on each of two right and left planes parallel to the laser optical path are arranged in parallel and at equal intervals. The dummy lamps for arranging the electromagnetic force and acting on the flash lamp row are arranged at positions from both ends of the flash lamps to minimize the electromagnetic force.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention.

The laser amplifier shown in FIG. 1 is in the form of a box-type disk amplifier, and is a dummy lamp 1-a, which is arranged at a distance d from both ends of a flash lamp row on two left and right planes parallel to each other with respect to the laser optical path. 1-b, 1-c, 1-
d, an odd number of 15 flash lamps 2-1 to 2-15 and 3-1 to 3-1 arranged in parallel with each other and at equal intervals
5, reflectors 4-a, 4-b (not shown) that constitute concave reflectors for the flash lamps,
Laser disk glass 5-a, 5-b, laser input window 6-a, laser output window 6-b,
Lamp chambers 7-a and 7-b as independent chambers for accommodating flash lamps and dummy lamps, shield glasses 8-a and 8-b for irradiating flash lamp excitation light, and a case 9 are provided. .

FIG. 2 is a cross sectional view of the embodiment shown in FIG. The embodiment shown in FIG. 1 will be described below with reference to FIG.

Flash lamps 2-1 to 2-15 and 3-1 to 3-3-
The two 15 are operated in units of two, so that the direction of the discharge current is alternately inverted for each flash lamp.

FIG. 3 is an illustration of the arrangement and current direction of the flash lamps shown in FIG. Dummy lamps 1-a to 1-d are arranged at a distance d from the upper and lower ends of the flash lamp row. Each of the flash lamps carries a discharge current from the back side of the paper surface indicated by P to the vertical front side and from the front side of the paper surface indicated by the Q direction to the vertical back side, and any flash lamp described above is connected to all the other flash lamps. The electromagnetic force expressed by equation (1) works. The four dummy lamps are arranged so as to pass a current in the opposite direction of the adjacent flash lamps and be separated from the flash lamps by a distance d. This distance d is selected as a position where the electromagnetic force reducing effect of the dummy lamp is maximized, that is, a position where the electromagnetic force acting on the flash lamp array is minimized. This position is the sum of the brute force of repulsion and attraction due to the electromagnetic force acting between the two flash lamps. For each combination of two dummy loads and 15 flash lamps, the formula (1) is used for each flash lamp. A simulation is performed based on the above calculation, and the simulation value of each flash lamp is set as the position where the simulation value becomes the minimum.

In this case, the purpose of making the number of flash lamps odd is
A complete vertical array of symmetry is obtained including the dummy lamp centering on the eighth flash lamp located in the center of the flash lamp, thereby optimizing the canceling effect of the electromagnetic force depending on the discharge current direction.

Flash lamp spacing d _o In this embodiment, the distance d to the dummy lamp is 25mm and has a 37mm.

By setting the dummy lamp position like this, the influence of the electromagnetic force is reduced, and particularly, the influence of the electromagnetic force is great at both ends of the flash lamp.
It is useful for significantly suppressing the influence on the 3-15 and the adjacent flash lamps adjacent thereto.

Here, the laser light input from the window 6-a passes through the laser disk glasses 5-a and 5-b and is output from the window 6-b.
a and 5-b are flash lamps 2-1 to 2-15 and 3-
It is photoexcited by 1-3 to 15 and increases the energy of the laser light passing through it. The flash lamp flashes at a predetermined duty and the reflector 4
-Shield glass 8 including reflection by a and 4-b-
laser disk glass 5-a, 5-through a, 8-b
Excite b.

Each of the laser disk glasses 5-a and 5-b has an oval disk glass, and is arranged with its vertical surface inclined by a predetermined angle α. As shown in the cross-sectional view of FIG. 2, the elliptical light receiving surface of the laser disk glass arranged at an angle of α behaves as a circle for a large-diameter laser beam to be input and is effective for a flash lamp. Provide an irradiation field. Further, the inclination of the angle α is such that a Brewster (Brewster) for completely transmitting the input large-diameter laser light.
Ster) angle, that is, tan ⁻¹ α = n (n is the refractive index of the laser disk glass).

In this way, the laser light amplified to the predetermined energy level by the double amplification by the laser disk glasses 5-a and 5-b while receiving the excitation light from the flash lamp is output from the window 6-b.

In the present embodiment, the distance d at which the dummy lamp should be arranged is selected at the position where the electromagnetic force is in the minimum state as described above. The effect will be described more specifically as follows.

FIG. 4 is a flash lamp acting electromagnetic force characteristic chart showing an example of characteristics of electromagnetic force applied to the flash lamp shown in FIG.

The characteristics A, B and C shown in FIG. 4 are that the number of flash lamps to be arranged per reflector surface, that is, to each of the left and right two surfaces parallel to the laser beam is 16, 15 and 15, and The distance d from the lamp row to the dummy lamp is 25 mm, 25 mm and 37 respectively.
It shows the characteristics of the electromagnetic force applied to each flash lamp in mm. However, the electromagnetic force acting on the flash lamps has vertical symmetry with respect to the center of the arrangement of the flash lamps, and therefore FIG. 4 shows the characteristics relating to the lower half of the arrangement. That is, the lamp No. (1) corresponds to the eighth flash lamp from the top when the odd number is 15, and No. (8) corresponds to the 15th flash lamp. Furthermore, when the flash lamp is an even number 16, No. (1) to No. (8) correspond to 9 to 16, and 1 to 8 are symmetrically arranged at the folded upper position. Become.

The vertical axis of FIG. 4 represents the electromagnetic force (N / m), and the electromagnetic force of the cylindrical disk amplifier is shown as a relative value as a scale for comparative reference. This cylindrical disk amplifier has a configuration in which four dummy lamps and 32 flash lamps are arranged in an equal circle. Therefore, as in the case of the characteristic A, an example using a total of 32 even flash lamps is taken as an example. The value 1 corresponds to an electromagnetic force of 33 N / m acting on each flash lamp.

The horizontal axis shows the distance from the center of the flash lamp array and the correspondence (lamp No.). The value X of the dummy lamp (DL) is (8) and ((8)) for characteristics A and B, respectively. 25
mm, and in the case of characteristic C, it becomes 37 mm from (8). Here, ((1)) and ((8)) show the positions of even 16 flash lamps, 25 mm is the interval between the flash lamps, and 37 mm is an odd 15 flash lamps with the minimum electromagnetic force acting on each flash lamp. This is the position of the Dami lamp. Further, the discharge current in this case is 6000 A as an example.

The meaning of FIG. 4 is as follows. That is,
An even number of 16 flash lamps are used, and dummy lamps 1-a, 1-b, 1-are further arranged at positions with the same arrangement interval of 25 m.
In the characteristic A when c and 1-d are arranged, the electromagnetic force acting on the dummy lamp exceeds 280 N / m, and the electromagnetic force acting on each flash lamp is much higher than the characteristics B and C. Further, the electromagnetic force acting becomes larger as it approaches the array end as a whole. This shows a basic problem that in a box-type planar array flash lamp, the effect of canceling the electromagnetic force effect due to the current direction decreases toward the array end. The characteristic B is a characteristic in which the electromagnetic force canceling effect is improved by setting the number of flash lamps to an odd number while keeping the distance d to the dummy lamp unchanged. Including the maximum value of the electromagnetic force, it shows a remarkable decrease as a whole as compared with the case of the characteristic A. That is, this effect can be obtained only under the odd-numbered arrangement condition. However, the No. 8 lamp at the end of the array still receives a high level of electromagnetic force. On the other hand, at the center of the array, the electromagnetic force acting on the flash lamp in the cylindrical disk amplifier is suppressed to a value far below.

Next, the characteristic C is an odd number 1 where the dummy lamp position is 37 mm.
This is the case of 5 flash lamps. The distance d set as 37 mm is set as the position where the electromagnetic force calculated between the flash lamps in a brute force manner based on the equation (1) becomes the minimum, so that the whole is more than the case of the characteristic B. The electromagnetic force is further reduced. However, a considerable level of electromagnetic force works on the dummy lamp at the extreme end, but conversely speaking, the existence of such a dummy lamp greatly suppresses the destruction of other flash lamps due to the electromagnetic force. . In the case of the present embodiment, thus, the electromagnetic force acting over the entire flash lamp including the array end and its vicinity is suppressed below in the case of the cylindrical type,
It is said that the possibility of breaking the flash lamp due to electromagnetic force has been significantly improved.

〔The invention's effect〕

The laser amplifier of the present invention is in the form of a box-type disk amplifier, and by arranging dummy lamps at arrangement positions different from those of the flash lamps at positions where the electromagnetic force acting on the flash lamps from both ends of the flash lamp row is minimized, There is an effect that the possibility of destroying the flash lamp due to electromagnetic force can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view of the embodiment shown in FIG. 3, FIG. 3 is an explanatory view of the arrangement and current direction of the flash lamp shown in FIG. 1, and FIG. 4 shows an example of characteristics of electromagnetic force applied to the flash lamp shown in FIG. FIG. 5 is a flash lamp array explanatory diagram showing an example of the array of flash lamps of a conventional laser amplifier. 1-a, 1-b, 1-c, 1-d ... Dummy lamp, 2
-1 to 2-15, 3-1 to 3-15 ... Flash lamp, 4-a, 4-b ... Reflector, 5-a, 5-b ...
... laser disk glass, 6-a, 6-b ... window, 7-a, 7-b ... lamp chamber, 8-a, 8--
b ... shield glass, 9 ... case.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-35684 (JP, A) JP 61-43878 (JP, B2)

Claims (1)

[Claims] 1. In a box-type disk amplifier type laser amplifier, an odd number of flash lamps for excitation, which are to be arranged on each of two right and left planes parallel to the laser optical path, are arranged in parallel and at equal intervals. In addition, the dummy lamp for balancing the electromagnetic force acting on the flash lamp array is arranged at a position from both ends of the flash lamp array that minimizes the electromagnetic force.