JPH0278283A - Laser device - Google Patents

Abstract

PURPOSE:To improve a laser output by a method wherein an intermediate mirror is provided to a halfway point of an exciting region, an optimum resonator is constituted in the exciting region, an optimum reflectivity is given to the mirror, and the resonator is effectively utilized. CONSTITUTION:An exciting section 3 constitutes a resonator being sandwiched in between a total reflection mirror 2 and an intermediate mirror 5, and an exciting section 4 is provided between an output mirror 1 and the intermediate mirror 5. The region of the exciting section 3 is composed of the laser medium large in a gain coefficient and small in a saturation gain, and the region of the exciting section 4 consists of the laser medium small in a gain coefficient and Large in a saturation gain. And, the intermediate mirror 5 has a specified transmittance, laser rays of the exciting section 4 penetrate into the exciting section 3 and are reflected by the total reflection mirror 2 to return to the exciting section 3. Then, if the reflectivity of the intermediate mirror 5 is made large in a gain coefficient and the reflectivity of the output mirror 1 is made small in a gain coefficient, an adequate resonator can be obtained. Then, a laser output can be obtained independently of the volume of an exciting input, and a laser device can operate up to at a high output power.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a laser device having an improved configuration of an excitation section in a laser oscillator having a plurality of types of laser media.

(Prior Art) Conventional laser devices often have one laser medium, and the characteristics at the excitation section are determined only by the one medium used. Therefore, in a laser device that has a pumping part of a laser medium with a large gain coefficient and a small saturation gain, the laser output is easy to emit but the obtained laser output is low; Laser devices with an excitation section have the characteristic that although large outputs can be obtained, oscillation is difficult to occur.

Additionally, in order to compensate for these characteristics, laser devices having two excitation regions have been considered.

FIG. 8 shows an example of a conventionally used laser device having a pumping section of a laser medium with a large gain coefficient and a small saturation gain. In this laser device, a total reflection mirror 2 is provided on one side of an excitation section 3 of a laser medium with a large gain coefficient and a small saturation gain, and an output mirror 1 is provided on the other side. At this time, the reflectance of the output mirror 1 is set to be somewhat high, such as 70% to 99%.

The relationship between the output and the excitation input of the laser at that time is shown in the ninth section.
Shown in the figure. In such a laser device, a characteristic is obtained in which the laser output starts from a low excitation input and increases linearly in accordance with the input.

On the other hand, FIG. 10 shows an example of a conventionally used laser device having a pumping section of a laser medium with a small gain coefficient and a large saturation gain. In this laser device, a total reflection mirror 2 is provided on one side of a laser medium excitation section 4 with a small gain coefficient and a large saturation gain, and an output mirror 1 is provided on the other side. At this time, the reflectance of the output mirror is set to be somewhat low, such as 10% to 60%.

The relationship between the output and the excitation input of the laser at that time is expressed as
It is shown in Figure 1. In such a laser device, a laser output is not obtained at a low excitation input, but a characteristic is obtained in which the laser output rapidly increases linearly in accordance with the input after a certain threshold value is exceeded.

In line with these, laser devices have also been considered that have two excitation regions: an excitation region of a laser medium with a large gain coefficient and a small saturation gain 1q, and an excitation region of a laser medium with a small gain coefficient and a large saturation gain. FIG. 12 shows an example of a laser device having two regions. In this laser device, a total reflection mirror 2 is provided at one end of an excitation section consisting of an excitation section 3 of a laser medium with a large gain coefficient and a small saturation gain, and an excitation section 4 of a laser medium with a small gain coefficient and a large saturation gain. An output mirror 1 is provided on the other side.

The only way to extract the laser beam from this laser device is to extract it from the output mirror 1.
Since there is only one plate, its reflectivity has been decided to be one type for this co-pregnant organ. Once the reflectance of the output mirror 1 is determined, the output characteristics are determined by the relationship between the gain coefficient and saturation gain of the output mirror and the excitation section.

However, when the output mirror 1 with a high reflectance is used in the laser device shown in FIG. 12, the oscillation characteristics are determined by the excitation region with a very high gain coefficient, and the output characteristics change depending on the excitation input as shown in FIG. It starts to oscillate even in small places. However, when a mirror with such a high reflectance is used, the energy density inside the cocirculator becomes high, and the mirror tends to be damaged and the Cp output becomes saturated.

On the other hand, when a mirror with a low reflectance is used, the oscillation characteristics are determined by the excitation region with a very high saturation gain, and its output characteristics do not oscillate in areas where the excitation input is small, as shown in Fig. Oscillation begins when the value is large. At this time, since the reflectance is low, the energy density inside the mirror will not increase, the mirror will not be damaged, and there is no possibility that the output will tend to be saturated. On the other hand, a problem arises in that no laser output can be obtained at low input levels.

Such problems occur not only in laser devices that use two types of laser media, but also in laser devices in general that use three or more types of laser media with different characteristics.

(Problems to be Solved by the Invention) The present invention provides a laser that makes it possible to improve the laser output by making good use of the relationship between these laser media and the output mirror and fully demonstrating the characteristics of each excitation medium. The purpose is to provide equipment.

[Structure of the Invention] (Means for Solving the Problems) The laser device of the present invention has a plurality of excitation regions using a plurality of different laser media, and these plurality of excitation regions are combined to form one laser. An excitation section of the device is configured, the excitation section has a total reflection mirror at one end, an output mirror at the other end, and an intermediate mirror having a predetermined transmittance is provided between the plurality of excitation regions. This is a structural feature.

(Operation) The operation of the present invention having the above-described configuration is as follows.For example, if the present invention is applied to a laser device having two types of laser media as explained in the above-mentioned prior art, the gain coefficient can be changed. The excitation region of a laser medium with a very small saturation gain is sandwiched between a total reflection mirror and an intermediate mirror, forming one common camera.In addition, the excitation region of a laser medium with a small gain coefficient and a large saturation gain It will be sandwiched between the output mirror and the intermediate mirror.

In this case, the intermediate mirror has a certain degree of transmittance, so the laser light in this excitation region enters the other region from the intermediate mirror, but there is a total reflection mirror at the end of that region. It is totally reflected and returns to the original area. Therefore, the excitation region of the laser medium where the gain (d coefficient is small and the saturation gain 1q is large) is the same as being sandwiched between the output mirror and the total reflection mirror.

Therefore, if the reflectance of this intermediate mirror is appropriately selected to have a large gain coefficient, and the reflectance of the output mirror is appropriately selected to be one with a large saturation gain, excitation of a laser medium with a small gain coefficient and a large saturation gain can be achieved. Optimal resonator configurations and mirror reflectances can be provided for two excitation regions: the excitation region of a laser medium with a large gain coefficient and a small saturation gain.

In this way, in the present invention, an appropriate resonator configuration can be achieved for each excitation region by disposing an intermediate mirror having an appropriate transmittance for the laser medium constituting the excitation region in the middle of each excitation region. can give.

(Example) Examples of the laser device having two excitation regions according to the present invention as described above are shown in FIGS. 1 to 7, and will be specifically described. Note that the same parts as in the prior art shown in FIGS. 8 to 12 are denoted by the same reference numerals, and explanations thereof will be omitted.

In the embodiment shown in FIG. 1, the present invention is applied to a carbon dioxide laser.

A carbon dioxide laser has a characteristic that when the operating pressure is low, the gain coefficient is large and the saturation gain is small, and when the operating pressure is high, the gain coefficient is small and the saturation gain is large.

In FIG. 1, the excitation region 3 of the laser medium has a low operating gas pressure, that is, a large gain coefficient and a small saturation gain.
can be sandwiched between the total reflection mirror 2 and the intermediate mirror 5 to form one resonator. In addition, the excitation region 11J, 4 of the laser medium where the operating gas pressure is high, that is, the gain coefficient is small and the saturation gain is large, is the output mirror 1 and the intermediate mirror 4.
sandwiched between. However, this intermediate mirror 5 has a certain degree of transmittance, and the laser light in this excitation region enters another region from the intermediate mirror 5, but there is a total reflection mirror 2 at the end of that region. There, it is totally reflected and returns to the original area. Therefore, the excitation region I or 4 of the laser TS quality, which has a small gain coefficient and a large saturation gain, is sandwiched between the output mirror 1 and the total reflection mirror 2! It will be the same as here.

Therefore, if the reflectance of the intermediate mirror 5 is appropriately selected to have a large gain coefficient, and the reflectance of the output mirror 1 is appropriately selected to be one with a large saturation gain, an appropriate value of 1 can be obtained for each of them.
A dragonfly will be formed.

As a result, such a laser device can smoothly obtain an output without distinction, from a small output with a small excitation input to a high output with a large excitation input. The applicant found that the laser output characteristics were best when the reflectance of the intermediate mirror was set to about 70% and the reflectance of the output mirror was set to about 30% in the configuration of the embodiment shown in FIG. there were.

In the above embodiment, the resonators are connected in series, but as shown in FIG.
The resonator may be constructed by bending it into a U-shape. Further, they can be arranged in a Z-shape as shown in FIG. 4, or in an L-shape as shown in FIG. Zarani L
When the prisms are arranged in a letter shape, it is also possible to use a prism 7 whose corner part has reflectance on one surface as shown in FIG.

Furthermore, as shown in FIG. 7, the total reflection mirror 8 may be a grating in order to provide wavelength selectivity.

Further, although a case has been shown in which differences in gain characteristics in carbon dioxide lasers are used, any laser medium may be used as long as the laser medium has a difference in gain characteristics. For example, various types of lasers can be considered, such as excimer lasers with different mixing ratios of excimer gas and buffer gas, glass lasers and YAG lasers with different Cr doping rates.

Although we have briefly described lasers with two media, it goes without saying that these can be extended to lasers with three or more media using the same principles.

[Effects of the Invention] As explained above, in the present invention, by simply providing an intermediate mirror in the middle of each excitation region, it is possible to achieve the optimal co-imager configuration and mirror reflection for each excitation region. In addition, each excitation region can be used effectively, and a laser output can be obtained even with a small excitation input, allowing continuous operation to a high output.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a basic embodiment of a laser device according to the present invention, FIG. 2 is a characteristic diagram thereof, and FIGS. 3 to 7 are block diagrams showing other embodiments of the present invention, respectively. 9 to 14 are configuration diagrams of conventionally used laser devices and characteristic diagrams showing their characteristics. 1... Output mirror, 2... Total reflection mirror, 3...
Excitation section (high saturation intensity), 4...excitation section (high gain intensity)
, 5... intermediate mirror, 6... return mirror, 7.
... Prism, 8... Grating.

Claims (1)

[Claims] (1) It has multiple excitation regions using multiple different laser media, and these multiple excitation regions are combined to form an excitation section of a single laser device, and total reflection occurs at one end of the excitation section. 1. A laser device comprising a mirror, an output mirror at the other end, and an intermediate mirror having a predetermined transmittance between the plurality of excitation regions.