JP2005072131A - Laser oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser oscillator which can output laser light of a desired pulse width and can be designed easily. <P>SOLUTION: The laser oscillator comprises an optical resonator 6 which consists of a pair of mirrors 3 and 4 that are located with a laser medium 1 in between, a Q switch 2 which switches laser light excited inside the optical resonator 6, and an image transfer optical system 10 which is located inside the optical resonator 6 and adjusts the resonator length of the optical resonator 6 by transferring an image of light excited at a predetermined position inside the optical resonator 6 to a position separated by a prescribed distance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser oscillator, and more particularly to a laser oscillator that obtains high-power pulsed laser light using a Q switch.

  Conventionally, a high-energy laser beam used for a laser beam processing machine or the like is produced by, for example, a laser oscillator using a Q switch. For example, as shown in FIG. 4, this laser oscillator includes a solid-state laser medium (for example, Nd: YAG) 1 and a Q switch 2, a first reflecting mirror (total reflection mirror) 3 and a second reflecting mirror (partial reflection mirror) 4. Between the two. The solid laser medium 1 is energized by an excitation source 5 such as a krypton lamp and emits excitation light into the optical path.

  The laser oscillator configured as described above turns off the Q switch 2 to excite the solid-state laser medium 1. When the excitation proceeds sufficiently and the inversion distribution of the solid-state laser medium 1 reaches the highest range, the Q switch 2 is turned on. Then, the excitation light excited and emitted by the solid laser medium 1 reciprocates between the total reflection mirror 3 and the partial reflection mirror 4. This excitation light is repeatedly reflected between the total reflection mirror 3 and the partial reflection mirror 4 to cause optical resonance. The optical energy is amplified by this optical resonance, and pulsed high energy laser light is emitted from the partial reflection mirror 4. When the inversion distribution of the solid-state laser medium 1 is eliminated, the Q switch 2 is turned off and the solid-state laser medium 1 is excited again. By repeating such a process continuously, stimulated emission occurs continuously and efficiently, and high-energy laser light can be obtained.

Incidentally, it is known that the pulse width of the laser beam output from the laser oscillator configured as described above is proportional to the distance between the total reflection mirror 3 and the partial reflection mirror 4 (for example, non-patent). Reference 1). A laser apparatus that controls the output energy and pulse width of laser light by applying this principle is known (see, for example, Patent Document 1). In this laser apparatus, the distance between the total reflection mirror and the partial reflection mirror can be continuously varied for the purpose of continuously variably controlling the output energy and the pulse width. Further, there is known a laser apparatus that detects laser light that has undergone laser resonance with an optical resonator, adjusts the resonator length of the optical resonator based on the detection result, and varies the pulse width (for example, Patent Documents). 2).
Japanese Patent Laid-Open No. 9-282827 Japanese Patent Laid-Open No. 2002-151779 Emnon Yariv, “Quantum Electronics” (USA), 2nd edition, John Wiley & Sons, Inc., 1975, p. 141-142

  However, to change the pulse width of the laser beam of the laser oscillator described above, the optical resonator length can be changed, but the spatial characteristics such as the laser beam diameter and the spread angle change by changing the optical resonator length. I can't deny that. For this reason, in order to change the pulse width of the laser light, it is necessary to consider not only the optical resonator length but also the spatial characteristics, and there is a problem that the design of the optical resonator becomes complicated. Further, depending on the laser medium, the optical resonator length cannot be freely designed, and there is a problem that it is difficult to produce a laser oscillator that obtains a desired pulse width.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a laser oscillator that can be easily designed and can output laser light having a desired pulse width.

In order to achieve the above-described object, a laser oscillator according to the present invention includes an optical resonator including a pair of mirrors provided with a laser medium interposed therebetween,
A Q switch for switching the laser light pumped in the optical resonator;
An image transfer optical system that is disposed in the optical resonator and transfers an image of light at a predetermined position excited in the optical resonator to a position separated by a predetermined distance to adjust a resonator length of the optical resonator; It is characterized by comprising.

Preferably, the image transfer optical system includes a plurality of lenses provided coaxially with a predetermined distance between the laser medium or the Q switch and one mirror of the optical resonator, It is desirable to be configured to hold the image of the output light with respect to the image constant.
More preferably, the image transfer optical system includes two lenses provided coaxially with a predetermined distance between one mirror of the optical resonator facing the Q switch, It is desirable to keep the output light image relative to the image constant.

  According to the laser oscillator configured as described above, an image transfer optical system that adjusts the resonator length of the optical resonator by transferring the excited light image to a position separated by a predetermined distance is provided in the optical resonator. Therefore, it is possible to easily design a laser oscillator that outputs laser light having a desired pulse width without changing the spatial characteristics of the laser light in the resonator.

Hereinafter, a laser oscillator according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a functional configuration diagram showing a schematic configuration of a laser oscillator according to the present invention. In this figure, the same members as those in FIG. 4 are assigned the same reference numerals as in FIG.
In FIG. 1, reference numerals 3 and 4 denote a total reflection mirror and a partial reflection mirror, which are provided so as to face each other to form an optical resonator 6. The optical resonator 6 is provided with a laser medium 1 sandwiched between a total reflection mirror 3 and a partial reflection mirror 4. The laser medium 1 is excited by an excitation source 5 such as a krypton lamp. Further, in the optical resonator 6, a Q switch 2 that transmits or reflects the excitation light that is excited by the excitation source 5 and emitted from the laser medium 1 is provided. An image transfer optical system 10 that adjusts the resonator length of the optical resonator 6 is provided in the optical path of the laser light in the optical resonator 6. The image transfer optical system 10 includes a plurality of lenses, and plays a role of holding an output light image with respect to an input light image input to the image transfer optical system 10 constant.

  Basically, in the laser oscillator configured as described above, the present invention is characterized in that the image transfer optical system 10 is inserted into the optical path in the optical resonator 6 and the image transfer optical system. The image of the output light with respect to the image of the input light input to is kept constant. That is, an optical resonator of a basic optical system including an optical resonator 6 including a pair of mirrors 3 and 4 provided with a laser medium 1 interposed therebetween and a Q switch 2 for switching laser light excited by the optical resonator 6. An image transfer optical system 10 that adjusts the resonator length of the optical resonator 6 by transferring an image of light at a predetermined position excited in the optical resonator 6 to a position separated by a predetermined distance is disposed in the optical resonator 6. It is a feature.

  In the laser oscillator according to the present invention having such a characteristic, in order to change the pulse width of the laser light output from the laser oscillator, the interval between the total reflection mirror 3 and the partial reflection mirror 4 (a desired pulse width) ( The resonator length) may be changed. This is because, as described above, there is a correlation between the optical resonator length and the pulse width of the laser beam. Specifically, the pulse width of the laser light obtained from the laser oscillator (hereinafter referred to as the reference laser oscillator) shown in FIG. 2 is [w], and the laser has a pulse width [2w] that is twice this pulse width. In order to obtain light, the distance (distance) L between the total reflection mirror 3 and the partial reflection mirror 4 provided in the reference laser oscillator may be doubled.

  At this time, in order to obtain laser oscillators having different pulse widths while maintaining the spatial characteristics of the reference laser oscillator other than the pulse width, a predetermined reference point B is determined in the optical path of the reference laser oscillator. For example, the reference point B is defined between the Q switch 2 and the partial reflection mirror 4 as shown in FIG. At this time, it is assumed that the distance between the reference point B and the end face of the Q switch 2 is [a], and the distance between the reference point B and the end face of the partial reflection mirror 4 is [b].

Next, a resonator length (a distance between the total reflection mirror 3 and the partial reflection mirror 4) for obtaining a desired pulse width is obtained by calculation. For example, when the resonator length of the reference laser oscillator is [L] and the pulse width is [w], and the desired pulse width is doubled [2w], the resonator length is doubled [2L]. do it.
On the other hand, if the focal length of the first lens 11 is [f1] and the focal length of the second lens 12 is [f2], the focal length of each lens may be set so as to satisfy the following expression.

[2L−L = 2 (f1 + f2)]
∴ [L = f1 + f2]
Then, the image transfer optical system 10 formed by the two lenses 11 and 12 having the focal length obtained by this equation is inserted into the optical path between the Q switch 2 and the partial reflection mirror 4 as shown in FIG. That's fine.

  The insertion position of the image transfer optical system 10 is positioned so that the focal length [f1] of the first lens 11 is the distance [a] between the reference point B and the end face of the Q switch 2 described above. Then, the second lens 12 is positioned at the position of the sum [f1 + f2] of the focal length [f1] of the first lens 11 and the focal length [f2] of the second lens 12. Then, the focal length [f2] of the second lens 12 of the image transfer optical system 10 matches the distance [b] between the reference point B and the end face of the partial reflection mirror 4.

  At this time, the image of the laser beam formed at the focal length [f1] (reference point B) of the first lens 11 passes through the image transfer optical system 10 and the focal length [f2] ( Projected as an image of laser light having the same spatial characteristics to the projection point P). Since this image is formed at a point coincident with the distance [b] between the reference point B in the optical path of the reference laser oscillator and the end face of the partial reflection mirror 4, the laser formed on the partial reflection mirror 4 by the reference laser oscillator. It is possible to obtain an image having the same light and spatial characteristics.

  Conversely, even in the laser light reflected by the partial reflection mirror 4, the same image is formed at a point corresponding to the distance [a] between the original reference point B and the end face of the Q switch 2. Spatial characteristics of do not change. That is, in the laser oscillator according to the present invention, the image of the output light with respect to the image of the input light is fixed by the image transfer optical system 10 including a plurality of lenses provided coaxially in the optical resonator 6 at a predetermined distance. Therefore, even if the resonator length is changed, if the focal length of the image transfer optical system 10 is set as described above, laser light having an arbitrary pulse width can be obtained without changing the optical characteristics. Become.

  In order to reduce the change in optical characteristics, it is preferable to use lenses having the same optical characteristics as the first and second lenses 11 and 12. For example, when the pulse width is double that of the reference pulse oscillator as described above, if the focal lengths of the respective lenses are equal [f = f1 = f2], [f = L / 4 = 0.25L The focal length of the lens may be set so as to satisfy the above.

  In the above-described embodiment, the image transfer optical system 10 is interposed between the Q switch 2 and the partial reflection mirror 4. However, it may be inserted at an arbitrary position in the laser beam path of the optical resonator 6. Absent. For example, the image transfer optical system 10 may be inserted in the optical path between the laser medium 1 and the Q switch 2 or in the optical path between the laser medium 1 and the total reflection mirror 3. In any case, the image transfer optical system 10 that satisfies a desired resonator length may be used as in the above-described embodiment.

In the above-described embodiments, the image transfer optical system 10 including two lenses (the first lens 11 and the second lens 12) has been described for easy understanding. Needless to say, two or more lenses may be combined as long as the image of the output light with respect to the image is kept constant.
In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

It is a schematic block diagram which shows an example of the laser oscillator which concerns on one Embodiment of this invention. It is a schematic block diagram which shows the basic optical system of a laser oscillator. It is a figure which shows the relationship of the focal distance of the image transfer optical system in the laser oscillator which concerns on one Embodiment of this invention. It is a schematic block diagram which shows an example of the conventional laser oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser medium 2 Q switch 3 Total reflection mirror 4 Partial reflection mirror 5 Excitation source 6 Optical resonator 10 Image transfer optical system 11 First lens 12 Second lens

Claims (3)

An optical resonator comprising a pair of mirrors provided with a laser medium in between;
A Q switch for switching the laser light pumped in the optical resonator;
An image transfer optical system which is disposed in the optical resonator and transfers an image of light at a predetermined position excited in the optical resonator to a position separated by a predetermined distance to adjust the resonator length of the optical resonator; A laser oscillator comprising:   The image transfer optical system includes a plurality of lenses coaxially provided at a predetermined distance between the laser medium or the Q switch and one mirror of the optical resonator, and outputs an image of input light. 2. The laser oscillator according to claim 1, wherein the laser image is held constant.   The image transfer optical system is composed of two lenses coaxially provided with a predetermined distance between one mirror of the optical resonator facing the Q switch, and output light for an image of input light. The laser oscillator according to claim 1, wherein the image is held constant.

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