JPH0341788A - Laser - Google Patents

Abstract

PURPOSE:To obtain a laser capable of performing a laser oscillation and a light amplification by one laser medium by a method wherein the laser is provided with an optical path modifying means to form the optical path of such a laser beam as to be able to lead out to the outside after the laser beam having a plane of polarization modified by a plane-of-polarization modifying means is directed again into the laser medium utilizing the reflection action of a polarizer and is amplified. CONSTITUTION:When a Pockels element control device 7a receives a delay pulse from a central control device 13, a voltage which is applied to a Pockels element 7 is made zero. If so, the action of a laser beam, whose plane of polarization has been modified by 90 deg. by the element 7, is stopped during the time when the voltage is zero. Thereby, a laser beam r0 having a plane of polarization parallel to the plane of the paper when it passes through a polarizer 6 is reflected by a totally reflecting mirror 4 and when the beam r0 is returned to the polarizer 6, it receives the action only of a lambda/4 plate 10 and is turned into a laser beam r1 (whose plane of polarization is vertical to the plane of paper), which is a linearly polarized light having a plane of polarization shifted by 90 deg. to that of the former laser beam. Therefore, this laser beam r1 is reflected by the polarizer 6, goes through a reflecting mirror 8, a beam expander 12, a reflecting mirror 9 and a polarizer 5, is directed into a laser medium 1, is light-amplified by the laser medium 1 to become a strong laser beam r2 and the laser beam r2 is reflected by the polarizer 6 and is led out to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser device in which a single laser medium performs laser oscillation and optical amplification of the laser light obtained by the oscillation.

[Prior Art] Laser devices that optically amplify oscillated laser light and output it as a powerful laser light have been known.

Conventional laser devices of this type generally use a plurality of laser media, and perform optical amplification by passing laser light oscillated by one laser medium to another laser medium.

Further, as another example, there is one described in Japanese Patent Application Laid-Open No. 62189778.

In this example, a wide slab-type laser medium is used, laser oscillation is performed in a part of this laser medium, and the oscillated laser beam is made incident on another part of the laser medium. It is designed to perform optical amplification.

[Problems to be Solved by the Invention] Incidentally, in the conventional laser device using the plurality of laser media described above, each stage of optical amplification stage has an optical amplification stage that is approximately the same as that of the laser oscillation stage. or more equipment is required. That is, in order to configure the optical amplification stage, at least the same laser medium as the laser oscillation stage, an excitation lamp, a power source for driving the excitation lamp, etc. are required.

For this reason, multiple amplification stages are used to achieve the desired high output.
When attempting to construct a laser device that produces high-quality laser light, there are problems in that the device becomes complicated and large, difficult to install and adjust, and the manufacturing cost becomes extremely high.

Furthermore, the method described in JP-A-62-189778 requires a special shaped laser medium that is significantly wider than a normal laser medium for laser oscillation, and in order to excite this laser medium, In this case, it is necessary to use a special excitation lamp depending on the width of the laser medium, or to use a plurality of lamps, resulting in the same inconvenience as in the case of using a plurality of laser media. It will happen.

The present invention has been made under the above-mentioned background, and includes:
The object of the present invention is to provide a laser device that can perform laser oscillation and optical amplification using a single laser medium.

[Means for Solving the Problems] The present invention solves the above problems by having the following configuration.

comprising a laser medium, an excitation light source that excites the laser medium, and a pair of light reflecting means disposed opposite to each other with the laser medium sandwiched therebetween in order to form a laser resonant optical path through the laser medium; A polarizing element that reflects linearly polarized light other than this particular linearly polarized light is inserted between each of the pair of light reflecting means and each end face of the laser medium d in the resonant optical path. and a polarization plane changing means for changing the polarization plane of the laser beam when extracting the laser oscillation light to the outside is provided in the laser beam path other than between the polarizing elements, and further, the polarization plane changing means A beam path changing means is provided for forming an optical path such that the laser beam whose polarization plane has been changed can be made to enter the laser medium again by utilizing the reflection action of the polarizing element, amplified, and then taken out to the outside. A configuration characterized by.

[Operation] In the above configuration, when the laser medium is excited by the laser excitation light source, laser oscillation occurs within the resonant optical path. In this case, this oscillated laser light becomes a specific polarized light due to the action of the polarizing element. Next, when an operation is performed to direct the laser beam to the outside, the polarization plane of the laser beam traveling in the laser beam path other than between the polarizing elements is changed by the polarization plane changing means. As a result, this laser light becomes linearly polarized light whose plane of polarization is different from that of the specific polarized light. And this straight! ! The polarized light is made to enter the laser medium again by the light beam path changing means using the reflection effect of the polarizing element, is amplified, and then taken out to the outside. That is, since laser oscillation and optical amplification are performed using one laser medium, there is no need to provide a separate laser medium, excitation lamp, etc. for optical amplification.

[Embodiments] (First Embodiment) FIG. 1 is a block diagram showing a laser device according to the first embodiment of the present invention, and FIG. 2 is a time chart showing the operation of the first embodiment. The first embodiment will be described in detail below with reference to the drawings.

In FIG. 1, the symbol above is a rod-shaped laser medium, and the symbol 2 is a rod-shaped laser medium.
is an excitation light source, 3 and 4 are total reflection mirrors for forming a laser resonant optical path, 5 and 6 are polarizing elements, 7 is a Pockels element as a means for changing the plane of polarization, and 8 and 9 are beam path changing devices. It is a reflecting mirror that is a means.

The diameter of the rod-shaped laser medium is 4 m, and the length is 80 m.
It is a cylindrical Nd:YAG crystal (manufactured by Allied Signal, Inc., USA) with both end faces cut at an angle of 3° with respect to the longitudinal direction, that is, the plane perpendicular to the optical axis direction. Note that both end faces are coated with anti-reflection coating (AR coating).

The excitation light source 2 is a flash lamp, and is disposed near the laser medium 1, and irradiates the laser medium 1 with pulsed excitation light to excite the laser medium 1. Note that this excitation light source 2 is controlled and driven by an excitation light source control device 2a.

The total reflection mirrors 3 and 4 are arranged on both sides of the laser medium 1 so that their reflective surfaces face each other in the optical axis direction of the laser medium 1.

The polarizing elements 5 and 6 allow linearly polarized light (P polarized light) whose polarization plane is parallel to the plane of the paper in FIG. 1 to pass through, while reflecting linearly polarized light (S polarized light) whose polarization plane is perpendicular to the plane of the paper,
For example, it is constructed by forming a multilayer dielectric film on a glass substrate.

These polarization cables 5 and 6 are arranged on both sides of the laser medium 1 in the optical axis direction of the laser medium 1, that is, on the laser optical path, and form a Brewster angle (approximately 57°) with respect to a plane orthogonal to the laser optical path. It is arranged like an eggplant.

The Pockels element 7 is controlled by a Pockels element control device 7a.
When a predetermined voltage (for example, 3.3 KV) is applied to the control device 7a, the polarization plane of the linearly polarized laser light that has traveled back and forth through the Pockels element 7 is set to 9.
0°, and when no voltage is applied, it passes through as is. Note that the drive timing and the like of the Pockels element control device 7a and the excitation light source 2a are controlled by a central control device 13.

Moreover, between the Pockels element 7 and the total reflection mirror 4, λ
/4Fi10 is arranged, and on the other hand, the Pockels element 7
A mode selector (2) is arranged between the polarizing element 6 and the polarizing element 6. The circle on the λ/4 plate changes the polarization plane of the linearly polarized laser beam that has reciprocated on the λ/4 plate 10 by 90'. Further, the mode selector 11 controls the output transverse mode of the laser beam.

The reflecting mirrors 8 and 9 reflect the laser beam reflected by the polarizing element 6 among the laser beams reflected by the total reflecting mirror 4, change the course of the beam, and direct the laser beam to the reflecting surface of the polarizing element 5. It is made incident.

In this case, the laser light reflected by the reflective surface of the polarizing element 5 travels in the optical axis direction of the laser medium l.

Note that a beam expander is arranged between the reflecting mirrors 8 and 9 to expand the beam cross-sectional area of the laser beam.

In the above configuration, the excitation light source 2 is driven by the excitation light source control device 2a while a voltage is applied to the Pockels device 7 by the Pockels device control device 7a based on the command of the central control device]. , the laser medium 1 is irradiated with a flash light onto the laser medium.
excite. FIG. 2(a) shows the excitation light source 2 at this time.
This shows a trigger pulse sent from the central controller 13 to the excitation light source controller 2a in order to start flash emission.From the rising point of this I rigger pulse, as shown in FIG. 2(b), , the excitation light source 2 emits development light for several hundred μsec.

Therefore, the laser medium 1 is excited and laser resonance light ro is generated. This laser resonance light r. The light reciprocates between the total reflection mirrors 3 and 4, but by passing through the polarizing elements 5 and 6, it becomes M-line polarized light having a plane of polarization parallel to the plane of the paper. At this time, since a voltage is applied to the Pockels element 7, the voltage enters the Pockels element 7, passes through the Pockels element 7 and the λ/4 plate, is reflected by the total reflection mirror 4, and is reflected again by the total reflection mirror 4. The laser light that has passed through the λ/4 and Pockels element 7 and returned is 9.
The 0° polarization plane is changed, and in the end, the light becomes linearly polarized light having the same polarization plane as before entering the Pockels element 7.

Therefore, in this state, the laser beam r□ continues to reciprocate between the total reflection mirrors 3 and 4.

Next, the central controller 13 sends to the Pockels element controller 7a a delay pulse that rises approximately 250 μsec after the rise of the trigger pulse. FIG. 2(C) shows this delay pulse.

When the Pockels element control unit W7a receives this delay pulse, as shown in FIG. 2(d), the voltage applied to the Pockels element 7 is set to zero for about 10 Orlsec from the rising point of the delay pulse. .

Then, during that time, the action of changing the polarization plane by 90° by the Pockels element 7 is stopped. As a result, the laser beam r□, which had a polarization plane parallel to the plane of paper when passing through the polarizing element 6, reaches the total reflecting mirror 4, is reflected by the total reflecting mirror 4, and is directed to the polarizing element 6. When it returns, it is subjected only to the action of the λ/4 plate 10 and becomes a linearly polarized laser beam rt whose plane of polarization is shifted by 90' with respect to the original laser beam (the plane of polarization is perpendicular to the plane of the paper).

Therefore, this laser beam r1 is reflected by the polarizing element 6, enters the laser medium 1 through the reflecting mirror 8, beam expander 12, reflecting mirror 9, and polarizing element 5, and is optically amplified by the laser medium 1. It becomes a powerful laser beam r2, which is reflected by the polarizing element 6 and taken out to the outside.

FIG. 2(e) shows the laser beam r2 taken out at this time.
This shows the pulse waveform of .

In addition, Fig. 2(f) and (g) are respectively shown in Fig. 2(f) and (g).
This is an enlarged view of the time axis in d) and (e), and as shown in FIG.
It is a puzzle light with an extremely narrow width of sec. Further, the laser beam r1 is controlled by the mode selector 11 to
For example, a high quality laser beam with a mode of T E M 00, before it enters the laser medium l,
The beam diameter is expanded to a predetermined size by the beam expander 12, and the beam is made incident on the laser medium. That is, high-quality laser light is amplified by fully utilizing the excitation region of the laser medium 1.

Therefore, the obtained laser beam r2 is extremely powerful, of good quality, and has a sharp pulse width.

(Second Embodiment) FIG. 3 is a block diagram showing the configuration of a laser device according to a second embodiment of the present invention. In this embodiment, a laser medium is sandwiched in order to form a laser resonant optical path through the laser medium. One of the pair of light reflecting means arranged opposite to each other is partially composed of a transmissive mirror, and through this partially transmissive mirror, a light beam having a specific plane of polarization is transmitted. ! This is different from the first embodiment, except that an oscillated laser beam consisting of polarized light is extracted, and the polarization plane of the extracted laser beam is changed and the laser beam is made to enter the laser medium again for amplification. They have almost similar ellipses. Therefore, the following description will focus on these differences.

In FIG. 2, numeral 201 is a rod-shaped laser medium, numeral 202 is an excitation light source, numeral 203 is a partially transmitting mirror, and numeral 2 is a rod-shaped laser medium.
04 is a total reflection mirror, 205 and 206 are polarizing elements, 207 is a Pockels element, 208, 209 and 2
Reference numeral 19 is a reflecting mirror serving as a beam path changing means, reference numeral 210 is a λ/2 plate serving as a polarization plane changing means, reference numeral 211 is a mode selector, and reference numeral 212 is a beam expander. Note that among these members, the partially transmitting mirror 203 and the λ/
Since the members other than the second plate 210 have the same functions as the corresponding members of the first embodiment, detailed explanation thereof will be omitted.

Furthermore, the excitation light source 202 and the Pockels element 207
There are also control devices for controlling the respective control devices and a central control device for controlling these control devices as in the first embodiment, but illustration and explanation of these will be omitted.

Furthermore, in this embodiment, the laser resonant system is arranged such that a partially transmitting mirror 2 is used instead of the total reflecting mirror 3 in the first embodiment.
03 and the λ/4 plate l○ in the first embodiment is removed from the laser resonant system. In this embodiment, the role of the Pockels element 207 is slightly different from that of the first embodiment in that it performs the function of a Q switch to obtain laser oscillation, but the operation timing etc. are shown in FIG. This is the same as in the first embodiment. Reflector 2 serving as the beam path changing means
08.209 and 219 are the Bockel elements 207
Pulse oscillation laser beam rO is generated by operating the Q switch.
When the light is taken out through the partially transmitting mirror 203, it is reflected to change its course, and is guided to be incident on the reflective surface of the polarizing element 205 at a predetermined angle.

A λ/2 plate 210 is interposed between the reflecting mirrors 209 and 219, and a beam expander 212 is interposed between the reflecting mirrors 208 and 209.

The λ/2 plate 210 changes the polarization plane of the linearly polarized laser beam ro having a polarization plane parallel to the plane of the paper by 90° to change it into laser light r1 having a polarization plane perpendicular to the plane of the paper. Therefore, this laser beam r1 is reflected by the polarizing element 205, enters the laser medium 1 again, and is amplified to become an intense laser beam r2. Since this laser beam r2 is linearly polarized light having a polarization plane perpendicular to the plane of the paper, it is reflected by the polarizing element 206 and taken out to the outside.

As a result, as in the first embodiment, it is possible to obtain the laser beam r2 that is strong, of good quality, and has a sharp pulse width.

In each of the above embodiments, a rod-type laser medium is used as the laser medium, but a slab-type laser medium may also be used. Also, the material is Nd:YLF
, Nd:GLass or Nd:GGG.

Further, in the first embodiment, the λ/4 plate 10 may be removed, and the timing at which voltage is applied to the Pockels element 7 may be reversed to that in the first embodiment.

That is, the same effect can be obtained even if the voltage is not applied all the time and the voltage is applied only at the moment when the laser beam is extracted.

[Effects of the Invention] As described in detail above, the present invention includes a laser medium, an excitation light source that excites the laser medium, and a laser medium that is sandwiched between the laser medium and facing each other in order to form a laser resonant optical path through the laser medium. a pair of light reflecting means disposed so that a specific linearly polarized light passes therethrough, and a polarizing element that reflects linearly polarized light other than this specific linearly polarized light is used in the resonant optical path to reflect the pair of light beams. Polarized light disposed between each of the reflecting means and each end face of the laser medium, and changing the polarization plane of the laser beam when the laser oscillation light is extracted to the outside during the laser beam path other than between the polarizing elements. A plane changing means is provided, and the laser light whose polarization plane has been changed by the polarization plane changing means can be made to enter the laser medium again by utilizing the reflection action of the polarizing element, amplified, and then taken out to the outside. The tank bottom is characterized by a light beam path changing means that forms an optical path such that a high-quality, high-output laser beam can be obtained, and the tank bottom can be formed compactly and easily installed. - A laser device is obtained that is easy to adjust and is inexpensive to manufacture.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a laser device according to a first embodiment of the present invention, FIG. 2 is a time chart showing the operation of the first embodiment, and FIG. 3 is a laser device according to a second embodiment of the present invention. FIG. 1.201...Rod type laser medium, 2.202...
- Excitation light source, 3, 4, 204... Totally reflecting mirror for forming a laser resonant optical path, 203... Partially transmitting mirror, 5.
205, 6, 206... polarizing element, 7, 207...
Pockels element, 8,208,9,209,219...
・Reflector serving as a beam course changing means, 11,211...Mode selector, 12,212...Beam expander

Claims (1)

[Scope of Claims] A laser medium, an excitation light source that excites the laser medium, and a pair of light reflection means that are disposed opposite to each other with the laser medium in between to form a laser resonant optical path through the laser medium. and a polarizing element that allows a specific linearly polarized light to pass through and reflects linearly polarized light other than the specific linearly polarized light, is provided in the resonant optical path between each of the pair of light reflecting means and each of the laser medium. A polarization plane changing means is provided between the end face and the laser beam path other than between the polarizing elements to change the polarization plane of the laser beam when extracting the laser oscillation light to the outside; A light beam path that forms an optical path in which the laser beam whose polarization plane has been changed by the plane changing means can be made to enter the laser medium again by utilizing the reflection action of the polarizing element, be amplified, and then taken out to the outside. A laser device characterized by being provided with a changing means.