JPS60217678A - Laser resonator - Google Patents

Abstract

PURPOSE:To obtain beams having intensity according to Gaussian distribution even in a resonator having one or more of Fresnel, and to acquire a high output laser proper to laser processing by gradually making coarse the surface roughness of a whole reflection mirror constituting a resonator with a proceeding toward an outer circumference thereof. CONSTITUTION:The surface roughness of an outer circumferential section except a section in the vicinity of the center is made coarse in at least one of reflecting mirrors 2, 3 for a laser resonator in which an enclosure, in which a laser medium 1 is encapsulated, and a plurality of the reflecting mirrors 2, 3 resonating laser beams are opposed to each another. With the total reflecting mirror such as one 3, the quality of a material is of oxygen-free copper, the surface is finished through diamond cutting, and surface roughness is made coarse gradually toward an outer circumference from the section of a diameter slightly smaller than the diameter of an aperture. Surface roughness is adjusted by using 100- 1000# abrasive paper, and the mean of surface roughness processed through a chucking to a lathe is brought to approximately 1mum. Accordingly, beams having the desired distribution of intensity can be obtained even on an application to a resonator having Fresnel of numeral 3.

Description

【発明の詳細な説明】 〔発明の利用分野〕 本発明は高出力レーザ発振器に関する。[Detailed description of the invention] [Field of application of the invention] The present invention relates to high power laser oscillators.

〔発明の背景〕[Background of the invention]

レーザは切断や泗接等の加工用熱源として普及しつつあ
る。加工に用いられるレーザけ、レンズ等で集光したと
きに小さなスポットに絞ノすることか必要であり、この
ためには、強要分布がガウス分布に近いビームが最も優
れている。ビームの強度分布は共振器で決定さｈるので
、小出力のレーザではガウス分布のビームが得やすい細
く長い形状の共振器が採用さｔｌている。共振器の形状
はフレネル数で表わされる。フレネル０はビーム半径の
二乗をレーザ波長と共振器畏の積で割った値である。ガ
ウス分布のビームを得るにはフレネル数が小さいほと容
易であり、一般にはフレネル委文を１以下にしている。Lasers are becoming popular as a heat source for processing such as cutting and welding. It is necessary to focus the light into a small spot when it is focused by a laser beam, lens, etc. used for processing, and for this purpose, a beam with a forced distribution close to a Gaussian distribution is best. Since the intensity distribution of the beam is determined by the resonator, a narrow and long resonator is used to easily obtain a beam with a Gaussian distribution in a low-output laser. The shape of the resonator is expressed by the Fresnel number. Fresnel 0 is the square of the beam radius divided by the product of the laser wavelength and the cavity size. The smaller the Fresnel number, the easier it is to obtain a beam with a Gaussian distribution, and the Fresnel number is generally set to 1 or less.

ところが、近年、レーザは高出力化し、例えは、（′、
０２レーザでは数に〜勺規模の出力のレーザが実用化さ
れるようになった。このような高出力レーザではフレネ
ル数を１以トにすると大形化を招き、実用的ではない。However, in recent years, the output power of lasers has increased, and for example, (′,
02 lasers have come into practical use with outputs on the order of several to a thousand. In such a high-power laser, if the Fresnel number is 1 or more, the size will increase, which is not practical.

ところがフレネル数を１よりも太きぐすると、カラス分
イ■の強度のビームを発撮きぞることは困難で、集光し
たときのスポットが太くなる欠点かあった。However, when the Fresnel number was set higher than 1, it was difficult to emit and trace a beam with the intensity of crow's width, and the problem was that the spot when focused became thicker.

〔発明の目的〕[Purpose of the invention]

本発明の目的は、加工に優れたガウス分布の強度をもつ
高出力レーザ発振器全提供するにある。An object of the present invention is to provide a high-power laser oscillator having a Gaussian distribution intensity that is excellent in processing.

〔発明の棚、要〕[Shelf of inventions, essential]

従来のレーザ共振器の構成を第１図に示す。同図では最
も隋１１単な構成を示すが、高出力レーザでは多くは折
返し形の共振器が用いられる。レーザ媒質１は、例えば
、ＣＯ２レーザでは内部にＣＯ２゜Ｎ、、Ｈｅを主成分
とする希薄なカスが封入され、グロー放゛電によって励
起される。レーザ光は一対の反射骨間、即ち半透明の出
力師２と、全反制鴨３間で往復反射する間にレーザ媒′
Ｊｄ、１によって増幅され、その一部が出力峻２からレ
ーザ光４として外部に取り出される。出力悦２と全反釦
砺′＋３間にはアシく一チャ５と呼はれる内径２ａの中
空円板が挿入される。アパーチャ５はビーム径を制限し
、共振器内の、部品のアシイメントの計容差を大きくし
たり、質的に優れたビームを得る目的で用いられ、一般
には、全反射釦３の近傍に配置される。The configuration of a conventional laser resonator is shown in FIG. Although the figure shows the simplest configuration, a folded resonator is often used in high-output lasers. For example, in the case of a CO2 laser, the laser medium 1 has a dilute gas containing CO2, N, and He as main components sealed therein, and is excited by glow discharge. The laser beam is reflected back and forth between a pair of reflective bones, that is, a semi-transparent output shield 2 and a total anti-reflection duck 3, while the laser medium'
It is amplified by Jd, 1, and a part of it is taken out from the output beam 2 as a laser beam 4. A hollow disc having an inner diameter 2a, called a reel 5, is inserted between the output button 2 and the full release button +3. The aperture 5 is used to limit the beam diameter, increase the difference in the alignment of components within the resonator, and obtain a beam with excellent quality, and is generally placed near the total reflection button 3. be done.

今、出力ｌｌ＃２の曲率半径をＲ１３、全反射＠Ｃ３の
曲率半径をＲ７、共振器長、即ち、出力徘２と全反射＠
３間の距離をＬとし、Ｒ１、Ｒ，２、Ｉｌ、ａを共振器
パラメータと呼ぶ。レーザ媒債１が一様媒質で、フレネ
ル数が非常に小さいときは、ガウスの強度分布をもつビ
ームを得るには共振器パラメータを式（１）が満足する
ように、かつ、左辺が右辺よりもできるたけ小さくなる
ようＶＣ選ぶことにより達成できる。実際には、レーザ
媒ηｌは一様ではないので式（１）とはわずかにずれる
ことがある。Now, the radius of curvature of output #2 is R13, the radius of curvature of total reflection @C3 is R7, and the resonator length, that is, output #2 and total reflection @
The distance between 3 is defined as L, and R1, R,2, Il, and a are called resonator parameters. When the laser medium 1 is a uniform medium and the Fresnel number is very small, in order to obtain a beam with a Gaussian intensity distribution, the resonator parameters must be set so that equation (1) is satisfied, and the left side is smaller than the right side. This can be achieved by selecting a VC so that it is as small as possible. In reality, since the laser medium ηl is not uniform, there may be a slight deviation from equation (1).

ここに、λはレーザの波長である。Here, λ is the wavelength of the laser.

ところがフレネル数（ａ２／λＬ）が１に比べて大きく
なると、式（１）を満足するように共振器パラメータを
選んでも目標とするガウスの強度分布をもつビームは発
振しない。この問題を解決するために発明者らは実験及
び計算により検討した。この検討には共振器長りが５ｍ
の折返し形ＣＵ２　レーザを用いた。先ず、フレネル数
が０．８になるように内径１３ｍのアパーチャ５を用い
た実験では、出力鏡２を出た直後のレーザ光４の強度分
布は目標通りガウス分布であった。更に、出力鏡２から
１５ｍ先における強度分布もガウス分布であった。However, when the Fresnel number (a2/λL) becomes larger than 1, a beam with the target Gaussian intensity distribution will not oscillate even if the resonator parameters are selected to satisfy equation (1). In order to solve this problem, the inventors conducted experiments and calculations. For this study, the resonator length is 5 m.
A folded CU2 laser was used. First, in an experiment using an aperture 5 with an inner diameter of 13 m so that the Fresnel number was 0.8, the intensity distribution of the laser beam 4 immediately after exiting the output mirror 2 was a Gaussian distribution as expected. Furthermore, the intensity distribution 15 m ahead from the output mirror 2 was also a Gaussian distribution.

次に、フレネル数が３になるように内径２５ｍｍのアパ
ーチャ５を用いた実験では、出力坤２を出た直後のレー
ザ光４０強度分布は第２図（ａＪ　ｒ（示すように、目
標とはかけ離れた非常に乱れた強度分布であった。更に
、出力棚Ｉから１５ｎｌ先では、第２図（ｂ）に示すよ
うに、目槓通りのガウス分布の強度分布であった。この
現象′ｆ追及した結、ｙ、原因はアパーチャ５によって
増幅途中のビームの周辺部が削られ、聯界面で回折によ
る高調波が発生し、この高調波が減衰しながら伝搬して
くるためで、高調波成分を消滅させるにはフレネル数が
１に相当する距離以上を伝（坂させる必髪があり、従っ
てフレネル数が１以上の共振器ではビームへの高調波の
重畳は避けられないことがわかった。Next, in an experiment using an aperture 5 with an inner diameter of 25 mm so that the Fresnel number was 3, the intensity distribution of the laser beam 40 immediately after exiting the output 2 was The intensity distribution was far from each other and extremely disordered.Furthermore, as shown in Fig. 2(b), the intensity distribution 15nl ahead from the output shelf I was a Gaussian distribution as expected.This phenomenon'f As a result of investigation, the cause is that the peripheral part of the beam during amplification is scraped by the aperture 5, harmonics are generated due to diffraction at the interface, and these harmonics propagate while being attenuated. In order to eliminate the beam, it is necessary to propagate the beam over a distance corresponding to a Fresnel number of 1 or more, and therefore, in a resonator with a Fresnel number of 1 or more, it was found that the superposition of harmonics on the beam is unavoidable.

本発明は、共振器を構成する全反ＪＪ、ｌ―の面粗さを
外周にゆくに従って徐々に粗くすることによって、従来
のアパーチャのようにビーム周辺部を急に切断するのを
防ぎ、フレネル数が１以上の共振器における高調波の発
生を防止する。別の方法として、反射鏡の表面に誘電体
皮膜を＃着し、反射率が中心部で高く、外周に向って徐
々に低くする方法も考えられるが、このような肪′眠体
皮膜は耐ビーム強度が弱く信頼性に乏しいので高出力レ
ーザには適さない上、８１価である。In the present invention, the surface roughness of the full anti-JJ, l- that constitutes the resonator is gradually made rougher toward the outer periphery, thereby preventing sudden cutting of the beam periphery like in conventional apertures, and Fresnel The generation of harmonics in resonators having one or more resonators is prevented. Another method is to deposit a dielectric film on the surface of the reflector so that the reflectance is high in the center and gradually decreases toward the outer periphery, but such a dielectric film is difficult to resist. The beam intensity is low and reliability is poor, so it is not suitable for high-power lasers, and it has a valence of 81.

〔発明の実施例〕[Embodiments of the invention]

以下、本発明の一実施例を框３図、第４図によって説明
する。第３図は本発明によるＣ０２レーザ共振器の構成
図であり、第４図は、第３図の中の全反射ＬＭ３の拡大
図である。全反射軛３は材質が無酸素銅で、ダイヤモン
ド切削で面仕上けをした後、第１図に示すアパーチャ径
２ａよりもやや小さい径の部分から外筒に向って面粗さ
を徐々に粗くした。面粗さの調整には１００番〜１００
０番の研磨紙を用い、旋盤にチャックして加工した面粗
さの平均は１μｒＩＩ程度である。本実施例によれば、
フレネル数が３の共振器に適用しても、目標とする強度
分布のビー二を得た。An embodiment of the present invention will be described below with reference to Figures 3 and 4. FIG. 3 is a block diagram of a C02 laser resonator according to the present invention, and FIG. 4 is an enlarged view of total reflection LM3 in FIG. The material of the total reflection yoke 3 is oxygen-free copper, and after the surface is finished by diamond cutting, the surface roughness is gradually increased from a portion with a diameter slightly smaller than the aperture diameter 2a shown in Fig. 1 toward the outer cylinder. did. No. 100 to 100 for adjusting surface roughness
The average surface roughness obtained by machining using No. 0 abrasive paper and chucked on a lathe is about 1 μrII. According to this embodiment,
Even when applied to a resonator with a Fresnel number of 3, the target intensity distribution was obtained.

この説明は全反射鏡について述べたが、高出力レーザで
は折返し形レーザが用いられるので、この場合には、折
返し斜に本発明を適用してもよい。Although this description has been made regarding a total reflection mirror, since a folded laser is used in a high-power laser, the present invention may be applied to a folded diagonal in this case.

また、面粗さの調整は、反射率が急激に変化しない限り
、外周部で特に＃’ｌｌ＜Ｌなくとも一様でも効果があ
る。Further, the adjustment of the surface roughness is effective even if #'ll<L is uniform at the outer periphery, as long as the reflectance does not change suddenly.

〔発明の効果〕〔Effect of the invention〕

本発明によれは、フレネル数が１以上の共振器でもガウ
ス分布の分用を−もつビームが得られ、レーザ加工に適
した高出力レーザを捉供できる。According to the present invention, a beam having a Gaussian distribution can be obtained even in a resonator having a Fresnel number of 1 or more, and a high-power laser suitable for laser processing can be provided.

【図面の簡単な説明】[Brief explanation of the drawing]

ｖ、１図は従来の共振器の４ｆ＞成因、第２図は彼！１
ツのレーザの分用分布１３＜１、第３１メ１は本発明に
−おける共振器の構成図、第４図ｔゴ第３図の中の全反
射経′１の拡大断面図である。 １・・・レーザ媒質、２・・・出力６ｆ【３・・・全反
則錐（，４・・・レーザ光、５アバ〜チヤ。 代理人　弁理士　高槁明！；− 宅１図 槽Ｂ図　も作図v, Figure 1 shows the 4f > origin of the conventional resonator, Figure 2 shows he! 1
31 is a block diagram of a resonator according to the present invention, and is an enlarged sectional view of the total reflection path '1 in FIG. 3. 1...Laser medium, 2...Output 6f [3...Full cone (, 4...Laser light, 5 aba~chia. Agent: Patent attorney Akira Takamaki!;- House 1 Tank B Also draw diagrams

Claims (1)

【特許請求の範囲】 １、　レーザ媒質を封入した外囲器と、レーザビームを
共振させる？Ｍ数の反則−を対置したレーザ共振器にお
いて、 前記反射税のうち少くとも１つ（ｄ、中心刊近を除く外
胸部の而粗さを＄ト１　＜　したことを％徴とするレー
ザ共振器。 ２、前記反帽年（の面相さを外周にゆ（Ｋ従って、徐々
に和くしたことを特徴とする特許請求の糾囲第１項ｄ［
ｉ載のレーザ共振器。 ３　前記レーザ共振器のフレネル数が１以上であること
を特徴とする特許請求の範囲第１ｊｔ、ｌまたけ第２項
記載のレーザ共振器。[Claims] 1. Make the laser beam resonate with the envelope enclosing the laser medium? In a laser resonator in which M number of irregularities are placed opposite each other, at least one of the above-mentioned reflection taxes (d, laser resonance whose % characteristic is that the roughness of the external thorax excluding the central area is $ 1 < 1) 2. Paragraph 1 d of the patent claim, characterized in that the face of the hat is gradually softened toward the outer periphery.
i-mounted laser resonator. 3. The laser resonator according to claim 1, wherein the laser resonator has a Fresnel number of 1 or more.