JP2002055368A - Wavelength converting laser device - Google Patents
Wavelength converting laser deviceInfo
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- JP2002055368A JP2002055368A JP2000244715A JP2000244715A JP2002055368A JP 2002055368 A JP2002055368 A JP 2002055368A JP 2000244715 A JP2000244715 A JP 2000244715A JP 2000244715 A JP2000244715 A JP 2000244715A JP 2002055368 A JP2002055368 A JP 2002055368A
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- Japan
- Prior art keywords
- laser
- nonlinear optical
- wavelength conversion
- optical crystal
- wavelength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は，１個または複数個
の非線形光学結晶を用いてレーザ光の波長を１／２以下
にし，短波長のレーザ光を得ようとするレーザ装置に関
する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device which uses one or a plurality of nonlinear optical crystals to reduce the wavelength of a laser beam to 1/2 or less to obtain a short wavelength laser beam.
【０００２】[0002]
【従来の技術】非線形光学結晶を用いる波長変換レーザ
装置では，波長変換の効率を上げる為に，位相整合と結
晶内部のパワー密度を上げる事が２大要素である。前者
は非線形光学結晶に入射するレーザ光と発生する高調波
レーザ光の位相を整合する事であり，通常は非線形光学
結晶の複屈折特性を利用し，位相整合条件を満たす特定
の角度で結晶を切り出し，それに沿ってレーザ光を入射
することで達成される。位相整合の許容角度は非常に狭
い為，結晶の方向とと入射レーザ光の光軸の厳密な調整
が必要となる。後者は非線形光学結晶の特性であり，パ
ワー密度を上げる程変換効率が高くなる。2. Description of the Related Art In a wavelength conversion laser device using a nonlinear optical crystal, two factors are to increase phase matching and power density inside the crystal in order to increase the efficiency of wavelength conversion. The former is to match the phases of the laser light incident on the nonlinear optical crystal and the generated harmonic laser light. Usually, the birefringence characteristic of the nonlinear optical crystal is used to adjust the crystal at a specific angle that satisfies the phase matching condition. This is achieved by cutting out and injecting a laser beam along the cutout. Since the allowable angle of phase matching is very narrow, it is necessary to strictly adjust the direction of the crystal and the optical axis of the incident laser light. The latter is a characteristic of the nonlinear optical crystal, and the higher the power density, the higher the conversion efficiency.
【０００３】しかしながら厳密な位相整合条件と高いパ
ワー密度を両立する事はきわめて難しい。これは以下の
理由による。[0003] However, it is extremely difficult to satisfy both strict phase matching conditions and high power density. This is for the following reason.
【０００４】レーザ光は理想的なTEM００モードであっ
ても，回折効果によりビーム直径に反比例するビーム広
がりを持つ。従ってパワー密度を上げようとして，ビー
ム直径を細くすると，回折によるビーム広がり角度が大
きくなって，位相整合条件を外れる様になり，効率が低
下する。逆に位相整合に主眼を置き，平行度の高いビー
ムを得ようとすると，パワー密度が上がらず，効率も上
がらない事になる。[0004] Even in the ideal TEM00 mode, the laser beam has a beam spread that is inversely proportional to the beam diameter due to the diffraction effect. Therefore, if the beam diameter is reduced in order to increase the power density, the beam divergence angle due to diffraction becomes large, so that the phase matching condition is deviated, and the efficiency is reduced. Conversely, if one focuses on phase matching to obtain a beam with high parallelism, the power density does not increase and the efficiency does not increase.
【０００５】他の問題としては，非線形光学結晶の光学
損傷のであり，高い変更効率を得ようとしてレーザ光の
パワー密度を上げ過ぎると非線形光学結晶の損傷を生じ
る確立が高くなり，結晶の寿命が短くなる。Another problem is the optical damage of the nonlinear optical crystal. If the power density of the laser beam is excessively increased in order to obtain a high change efficiency, the probability that the nonlinear optical crystal will be damaged increases, and the life of the crystal increases. Be shorter.
【０００６】一般的な非線形光学結晶を用いた波長変換
レーザ装置の概略図を図１に示す。ここではレーザ発振
器からのレーザ出力光（１）を凸レンズ（２）を用いて
非線形光学結晶（３）に集束する。結晶内部のビームプ
ロフィールを図２に示す。入射レーザ光は円錐形状
（４）に集束されるが，中心部は回折広がりとバランス
して，一定の長さでビームが擬似平行の領域（５）が形
成される。この部分で高いパワー密度と，位相整合を両
立させようとする考え方である。FIG. 1 is a schematic diagram of a wavelength conversion laser device using a general nonlinear optical crystal. Here, the laser output light (1) from the laser oscillator is focused on the nonlinear optical crystal (3) using the convex lens (2). FIG. 2 shows the beam profile inside the crystal. The incident laser light is converged into a conical shape (4), but the central portion is balanced with the diffraction spread to form a region (5) of a fixed length and a pseudo-parallel beam. The idea is to achieve both high power density and phase matching at this point.
【０００７】さらに特開平5-159530に示される様に，２
枚の円筒レンズを用いて非線形光学結に楕円状にレーザ
光を収束する方法がある。この方法の概略図を図３に示
す。入射レーザビーム（６）は円筒レンズ（７）によ
り，非線形光学結晶（８）の位相整合方向（９）には集
束されず，位相整合方向と垂直な方向（１０）にのみ集
束される。Further, as disclosed in Japanese Patent Application Laid-Open No.
There is a method of converging laser light in an elliptical shape by nonlinear optical connection using a single cylindrical lens. A schematic diagram of this method is shown in FIG. The incident laser beam (6) is not focused by the cylindrical lens (7) in the phase matching direction (9) of the nonlinear optical crystal (8), but is focused only in the direction (10) perpendicular to the phase matching direction.
【０００８】また波長変換の効率を上げる為，外部光共
振器構造をとる場合もある。図４にその一例を示す。４
枚のミラー（１１）から成るリング共振器中に非線形光
学結晶（１２）が設置される。レーザ光が（１３）リン
グ共振器に入射され，波長変換された出力（１４）が得
られる。In some cases, an external optical resonator structure is employed to increase the efficiency of wavelength conversion. FIG. 4 shows an example. 4
A non-linear optical crystal (12) is placed in a ring resonator consisting of one mirror (11). The laser light is incident on the ring resonator (13), and the wavelength-converted output (14) is obtained.
【０００９】[0009]
【発明が解決しようとする課題】この様に，波長変換レ
ーザ装置では，非線形結晶に入射するレーザ光から波長
変換されたレーザ光への変換効率を高める為に，各種方
法が検討されている。実用的な波長変換レーザ装置に求
められる性能としては，変換効率が高い事，非線形光学
結晶の光学損傷が無く長時間使用できる事，位相整合等
の調整が簡単で長時間安定である事，等が条件となる。
従来これらの全ての満足させる事はできていない。特に
波長変換された光が紫外線の領域にある場合には，結晶
の損傷が大きな問題となる。As described above, in the wavelength conversion laser device, various methods have been studied in order to increase the conversion efficiency of the laser light incident on the nonlinear crystal into the wavelength-converted laser light. The performance required of a practical wavelength conversion laser device is that the conversion efficiency is high, that the nonlinear optical crystal can be used for a long time without optical damage, that the adjustment of phase matching, etc. is easy and stable for a long time, etc. Is a condition.
Heretofore, all of these have not been satisfied. Particularly when the wavelength-converted light is in the ultraviolet region, damage to the crystal becomes a serious problem.
【００１０】例えば，図１に示す凸レンズを用いてレー
ザ光を集束する方法では，位相整合条件より寧ろパワー
密度の増加に主眼をおいた構成である。一般に集束光学
系で，入射ビーム径を２ａ，入射ビームの広がり角を
θ，レンズの焦点距離をｆとすると，集束スポット径は
ｆθで表される。非線形光学結晶の位相整合の許容角度
Θとすると，レンズの集束と回折効果がバランスして形
成される擬似並行領域の長さは図２に示す様に，レーザ
光の収束が双曲線で行われる為，近似的にｆ３θΘ／ａ
２で求められる。ビーム径２ａ＝1ｍｍ，広がり角θ＝5
ｍｒａｄを焦点距離ｆ＝５０ｍｍのレンズで集束する
と，スポット径は２５０μm，非線形光学結晶の位相整
合の許容角度をΘ＜０．５ｍｒａｄとすれば，擬似平行
領域の長さは０．３mm程度となる。この方式の問題点は
パワー密度を上げようとして，集束スポット径を小さく
する程，有効な位相整合領域が短くなる事にあり，非線
形光学結晶のごく一部しか波長変換に寄与しない。総合
的な変換効率は高く出来ない。For example, the method of converging laser light using a convex lens shown in FIG. 1 focuses on increasing the power density rather than the phase matching condition. Generally, assuming that the diameter of the incident beam is 2a, the spread angle of the incident beam is θ, and the focal length of the lens is f in a focusing optical system, the focused spot diameter is represented by fθ. Assuming that the allowable angle 位相 of the phase matching of the nonlinear optical crystal is Θ, the length of the quasi-parallel region formed by balancing the focusing and diffraction effects of the lens is as shown in FIG. , Approximately f 3 θΘ / a
Required by 2 . Beam diameter 2a = 1mm, spread angle θ = 5
If mrad is focused by a lens having a focal length f = 50 mm, the spot diameter is 250 μm, and if the allowable angle of phase matching of the nonlinear optical crystal is Θ <0.5 mrad, the length of the pseudo-parallel region is about 0.3 mm. . The problem with this method is that as the focused spot diameter is reduced to increase the power density, the effective phase matching region becomes shorter, and only a small portion of the nonlinear optical crystal contributes to wavelength conversion. The overall conversion efficiency cannot be high.
【００１１】一方，図３に示す円筒凸レンズを用いてレ
ーザ光を集束する方法では，位相整合に主眼を置き，非
線形光学結晶の位相整合方向と垂直な方向でレーザ光の
入射角度に鈍感な方向に集束し，位相整合距離を十分に
とり，かつレーザ光パワー密度を上げることを目的とし
ている。この方式は図１の例で示した問題点は解消され
る。しかし通常レーザ発振器からのレーザ出力光はビー
ム広がり角度が数ｍｒａｄであるのに対し，非線形光学
結晶の位相整合の許容角度は１ｍｒａｄ以下となる場合
が多く，完全な位相整合は困難である。この方式の成功
例としては，文献Japanese Journal of Applied Physic
s Vol31 (1992)ppL682に発表されたArイオンレーザの光
共振器内部に設置した例がある。この場合は，光共振器
内部のレーザ光強度が外部のレーザ光強度に比較して１
桁程度高くなり，かつ光共振器内部での光の兵高度が十
分に高いため，高い効率で波長変換が行われている。こ
の形式で共振器外部で波長変換を行った場合，円凸筒レ
ンズは通常の凸レンズに比べて集束径が大きくレーザ光
のパワー密度が低い事，また位相整合条件も完全で無い
事から，高効率の波長変換は行われない。特に変換され
た波長が紫外線の領域に達する，可視レーザ光からの波
長変換では，位相整合角度の許容限度が１ｍｒａｄ以下
になる物が多く，高い変換効率は得られない。On the other hand, in the method of focusing a laser beam using a cylindrical convex lens as shown in FIG. 3, the main focus is on phase matching, and a direction insensitive to the incident angle of the laser beam in a direction perpendicular to the phase matching direction of the nonlinear optical crystal. The objective is to increase the laser light power density by focusing sufficiently on the laser beam and providing a sufficient phase matching distance. This method solves the problem shown in the example of FIG. However, the laser output light from the laser oscillator usually has a beam divergence angle of several mrad, whereas the allowable angle of the phase matching of the nonlinear optical crystal is often 1 mrad or less, and perfect phase matching is difficult. A successful example of this method is the Japanese Journal of Applied Physic
s Vol. 31 (1992) ppL682 has an example of installation inside an optical resonator of an Ar ion laser. In this case, the laser light intensity inside the optical resonator is 1 compared with the external laser light intensity.
The wavelength conversion is performed with high efficiency because it is about an order of magnitude higher and the altitude of light inside the optical resonator is sufficiently high. When wavelength conversion is performed outside the resonator in this manner, the circular convex cylindrical lens has a high focusing diameter and a low power density of laser light compared to a normal convex lens, and the phase matching conditions are not perfect. No wavelength conversion of efficiency is performed. In particular, in wavelength conversion from visible laser light, in which the converted wavelength reaches the ultraviolet range, there are many cases where the allowable limit of the phase matching angle is 1 mrad or less, and high conversion efficiency cannot be obtained.
【００１２】また図４に示す外部光共振器を用いる波長
変換では，共振器にレーザ光を閉じ込める事で高いパワ
ー密度が得られ，また共振器内部の定在波の条件により
レーザのパワー密度が高くすることが可能で高い波長変
換効率が可能である。しかしこの方式では入射レーザ光
の縦モード周波数と，外部光共振器の縦モード周波数を
厳密に整合させる必要があり，通常外部共振器のミラー
をピエゾエレクトロニクス素子等で位置の制御を可能と
し，外部光共振器へのレーザ光の入射光をモニターし
て，フィードバックをかける方法が必要になる。装置が
大掛かりで複雑になる問題があった。また光共振器の定
在波条件を得る為，４個のミラーの内の数個を凹面にす
る事が必須であり，光共振器内部でのビームの平行性は
あまり高く無く，位相整合条件が完全にはならないとい
う問題点があった。In the wavelength conversion using the external optical resonator shown in FIG. 4, a high power density can be obtained by confining the laser beam in the resonator, and the power density of the laser depends on the condition of the standing wave inside the resonator. It is possible to increase the wavelength conversion efficiency. However, in this method, the longitudinal mode frequency of the incident laser light and the longitudinal mode frequency of the external optical resonator must be strictly matched. Usually, the position of the mirror of the external resonator can be controlled by a piezo-electronic element or the like. A method of monitoring the incident light of the laser light on the optical resonator and applying feedback is required. There was a problem that the device was large and complicated. In order to obtain the standing wave condition of the optical resonator, it is necessary to make some of the four mirrors concave, and the parallelism of the beam inside the optical resonator is not very high. However, there was a problem that it was not perfect.
【００１３】そこで，本発明は非線形光学素子を用いる
波長変換レーザ装置において，上記の問題点を解決し，
波長変換効率が高く，かつ非線形光学素子の寿命が長
く，簡単な光学構成で，高出力が可能な，波長変換レー
ザ装置を提供する事を目的とする。Therefore, the present invention solves the above problems in a wavelength conversion laser device using a nonlinear optical element.
It is an object of the present invention to provide a wavelength conversion laser device having a high wavelength conversion efficiency, a long life of a nonlinear optical element, a simple optical configuration, and a high output.
【００１４】[0014]
【課題を解決するための手段】本発明は上記課題を解決
するため，レーザ発振器からのレーザ光を先ずコリメー
ト光学系により平行度を高め，この後非線形光学結晶に
入射させることを特徴とするものである。In order to solve the above-mentioned problems, the present invention is characterized in that a laser beam from a laser oscillator is first increased in parallelism by a collimating optical system, and thereafter is incident on a nonlinear optical crystal. It is.
【００１５】さらにコリメート光学系により平行度を高
めたレーザ光を円筒レンズにより，非線形光学結晶の位
相整合方向と垂直方向に集束する手段を設けたものであ
る。Further, there is provided means for converging the laser beam, whose parallelism has been increased by the collimating optical system, in a direction perpendicular to the phase matching direction of the nonlinear optical crystal by means of a cylindrical lens.
【００１６】レーザ発振器からのレーザ光を２個の非線
形光学結晶に順次入射する形式の波長変換レーザ装置に
おいて，非線形光学結晶に入射するレーザ光の一方また
は両方をコリメート光学系により，平行度を高めること
を特徴とする。In a wavelength conversion laser device of a type in which laser light from a laser oscillator is sequentially incident on two nonlinear optical crystals, one or both of the laser beams incident on the nonlinear optical crystal are increased in parallelism by a collimating optical system. It is characterized by the following.
【００１７】さらに両方の結晶について，コリメート光
学系により平行度を高めたレーザ光を円筒レンズによ
り，非線形光学結晶の位相整合方向と垂直方向に集束す
る手段を設けたものである。Further, for both crystals, there is provided means for converging the laser light, whose parallelism has been increased by the collimating optical system, in a direction perpendicular to the phase matching direction of the nonlinear optical crystal by means of a cylindrical lens.
【００１８】上記のコリメート光学系を用いる波長変換
レーザ装置において，コリメート光学系の倍率を入射レ
ーザビームの広がり角θと非線形光学結晶の位相整合の
許容角度をΘの比率の逆数であるθ／Θに等しくなるよ
うにしたものである。In the wavelength conversion laser apparatus using the above-described collimating optical system, the magnification of the collimating optical system is defined as the reciprocal of the ratio of the divergence angle θ of the incident laser beam and the phase matching of the nonlinear optical crystal to the ratio of Θ / 逆. It is made to be equal to.
【００１９】上記の波長変換レーザ装置において，レー
ザ発振器と１個の非線形光学結晶を組み合わせた場合，
レーザ発振器がNd-YAGレーザ，Nd-YVO4レーザ，Nd-YLF
レーザであり，非線形光学結晶がBBO，LBO，KTPの構成
としたものである。In the above wavelength conversion laser device, when a laser oscillator and one nonlinear optical crystal are combined,
Laser oscillator is Nd-YAG laser, Nd-YVO4 laser, Nd-YLF
It is a laser with a nonlinear optical crystal composed of BBO, LBO, and KTP.
【００２０】上記の波長変換レーザ装置において，レー
ザ発振器と２個の非線形光学結晶と組み合わせた場合，
レーザ発振器がNd-YAGレーザ，Nd-YVO4レーザ，Nd-YLF
レーザであり，第１の非線形光学結晶がBBO，LBO，KTP
で，第２の非線形光学結晶がBBOまたはCLBOの構成とし
たものである。In the above wavelength conversion laser device, when a laser oscillator and two nonlinear optical crystals are combined,
Laser oscillator is Nd-YAG laser, Nd-YVO4 laser, Nd-YLF
Laser and the first nonlinear optical crystal is BBO, LBO, KTP
Thus, the second nonlinear optical crystal has a structure of BBO or CLBO.
【００２１】[0021]
【発明の実施の形態】以下に本発明の一実施例について
図面を用いて説明する。図5は本発明の実施例の原理を
説明する為の光学系の概略図である。レーザ発振器（１
５）のレーザ出力光（１６）を集束光学系を用いず，非
線形光学素子（１７）に入射する場合を示す。レーザ出
力光（１６）は必ず何らかの広がり角度θ（１８）を持
っている。これは，ビーム直径２ａに起因する回折広が
りと，レーザ光の共振器設計に起因する，広がりの２点
がある。レーザ波長をλ，レーザ発振器の共振器長をL
とすれば，前者は０．２４４×λ／２ａ，後者は０．９
４×√（λ／Ｌ）で表される。ビーム広がり角度θが非
線形光学結晶の位相整合許容角度Θに比較して小さけれ
ば，全てのビームを有効に位相整合することが可能であ
るが，通常その条件を満足させることは困難である。例
えばＮｄ−ＹＡＧレーザの出力ビーム広がりは通常数ｍ
ｒａｄあるのに対し，典型的な波長変換用非線形光学結
晶であるＢＢＯの許容角度は1ｍｒａｄ程度であり，位
相整合条件が成立しない。DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a schematic diagram of an optical system for explaining the principle of the embodiment of the present invention. Laser oscillator (1
The case where the laser output light (16) of 5) is incident on the nonlinear optical element (17) without using the focusing optical system is shown. The laser output light (16) always has some spread angle θ (18). There are two points, a diffraction spread caused by the beam diameter 2a, and a spread caused by the design of the resonator of the laser beam. Laser wavelength is λ, resonator length of laser oscillator is L
Then, the former is 0.244 × λ / 2a, and the latter is 0.944 × λ / 2a.
It is expressed by 4 × √ (λ / L). If the beam spread angle θ is smaller than the phase matching allowable angle の of the nonlinear optical crystal, all the beams can be phase-matched effectively, but it is usually difficult to satisfy the condition. For example, the output beam spread of an Nd-YAG laser is usually several meters.
In contrast, the allowable angle of BBO, which is a typical nonlinear optical crystal for wavelength conversion, is about 1 mrad, and the phase matching condition is not satisfied.
【００２２】図６は本発明の第１の実施例である。レー
ザ発振器（１９）からのレーザ出力光（２０）はビーム
広がり角度θを有し，発振器の出力端から次第に広が
る。前述の様にビーム広がり角度はビーム径に依存する
回折広がり角度と光共振器の構成に依存する部分があ
る。レーザ光をコリメータ光学系（２１）を通過したレ
ーザビーム（２２）は光共振器の構成に依存する角度広
がりを補償し，ビーム径に依存する回折広がりの限界値
まで広がり角度を減少させる事ができる。非線形光学結
晶（２３）の位相整合許容角度がビーム径に依存する回
折広がりと同程度の場合には，波長変換が効率よく行わ
れる。FIG. 6 shows a first embodiment of the present invention. The laser output light (20) from the laser oscillator (19) has a beam spread angle θ and gradually spreads from the output end of the oscillator. As described above, there are portions where the beam spread angle depends on the diffraction spread angle depending on the beam diameter and the configuration of the optical resonator. The laser beam (22) passing the laser beam through the collimator optical system (21) compensates for the angular spread depending on the configuration of the optical resonator, and can reduce the spread angle to the limit value of the diffraction spread depending on the beam diameter. it can. When the allowable angle of phase matching of the nonlinear optical crystal (23) is substantially equal to the diffraction spread depending on the beam diameter, the wavelength conversion is performed efficiently.
【００２３】図７は本発明の第２の実施例を示す。本実
施例では，レーザ発振器の出力光はビーム広がり角度θ
を有している。ここではコリメータを倍率ｍの拡大光学
系とする。回折理論では，ビームの広がり角度がビーム
径に反比例するため，非線形光学結晶（２８）の部位で
のビーム広がり角度（２７）はθ／ｍとなる。この値が
非線形光学結晶（２８）の位相整合許容角度Θに等しく
する事で，波長変換が効率よく行われる。コリメータ光
学系の倍率ｍ＝θ／Θの条件が導き出される。この構成
によりコリメート光学系の倍率ｍを最適化する事で，レ
ーザ光のビーム広がり角度と，非線形光学結晶の位相整
合角度に拘らず，最適な位相整合条件を達成し，高い変
換効率を得る事が可能になる。FIG. 7 shows a second embodiment of the present invention. In the present embodiment, the output light of the laser oscillator has a beam spread angle θ
have. Here, the collimator is a magnifying optical system with a magnification of m. In the diffraction theory, the beam spread angle (27) at the portion of the nonlinear optical crystal (28) is θ / m because the beam spread angle is inversely proportional to the beam diameter. By making this value equal to the phase matching allowable angle の of the nonlinear optical crystal (28), wavelength conversion can be performed efficiently. The condition of the magnification m = θ / Θ of the collimator optical system is derived. By optimizing the magnification m of the collimating optical system with this configuration, optimal phase matching conditions can be achieved and high conversion efficiency can be achieved regardless of the beam spread angle of the laser beam and the phase matching angle of the nonlinear optical crystal. Becomes possible.
【００２４】図８は本発明の第４の実施例である。図８
（ａ）は非線形光学結晶（３３）の位相整合方向，図８
（ｂ）は位相整合と垂直の方向から見た図である。ここ
ではレーザ発振器（２９）の出力レーザ光（３０）をコ
リメート光学系（３１）により一旦ビーム広がり角度を
最適化し，更に円筒レンズ（３３）により非線形光学結
晶（３３）の位相整合方向と垂直な方向に集束する。こ
の光学構成では，位相整合方向については，図７に示す
コリメート光学系と同様なビーム広がり角度の最適化が
行われるのと同時に，波長変更に関して入射角度が鈍感
な位相整合と垂直な方向に集束する事で，非線形光学結
晶（３３）内部でのビーム断面積を小さくし，レーザ光
密度を高める事で，波長変換効率が高まる。本実施例の
他の特徴は，図１および図３で示す従来の単一のレンズ
で集束する方法に比べ，位相整合角度の最適化と集束に
よるレーザ光強度の最適化が，各々コリメート光学系
（３１）と円筒レンズ（３３）によって完全に独立に行
える点にあり，両者共に最適化が容易であるという特徴
がある。また非線形光学結晶内部のレーザ光強度は円筒
レンズ（３３）の焦点距離に反比例して一義的に決まる
為，結晶を劣化させることなく，高い波長変換効率を得
る最適なレーザ強度を得るための条件としてこの円筒レ
ンズの焦点距離の最適化のみで容易に行う事が可能であ
る。FIG. 8 shows a fourth embodiment of the present invention. FIG.
(A) is the phase matching direction of the nonlinear optical crystal (33), FIG.
(B) is a diagram viewed from a direction perpendicular to the phase matching. Here, the output laser light (30) of the laser oscillator (29) is once optimized by a collimating optical system (31) to optimize the beam divergence angle, and the cylindrical lens (33) is further perpendicular to the phase matching direction of the nonlinear optical crystal (33). Focus in the direction. In this optical configuration, as for the phase matching direction, optimization of the beam spread angle is performed in the same manner as in the collimating optical system shown in FIG. By doing so, the beam cross-sectional area inside the nonlinear optical crystal (33) is reduced, and the laser light density is increased, thereby increasing the wavelength conversion efficiency. Another feature of the present embodiment is that the optimization of the phase matching angle and the optimization of the laser beam intensity by focusing are performed by the collimating optical system, respectively, as compared with the conventional focusing method using a single lens shown in FIGS. (31) and the cylindrical lens (33) can be performed completely independently of each other, and both have a feature that optimization is easy. Also, since the laser light intensity inside the nonlinear optical crystal is uniquely determined in inverse proportion to the focal length of the cylindrical lens (33), conditions for obtaining the optimum laser intensity for obtaining high wavelength conversion efficiency without deteriorating the crystal. It can be easily performed only by optimizing the focal length of the cylindrical lens.
【００２５】図９は本発明の第４の実施例であり，レー
ザ光を２回の波長変換を行い，４次高調波で短波長レー
ザ光を得るものである。レーザ発振器（３４）からの基
本波レーザ出力光（３５）は第１のコリメータ（３６）
により第１の非線形光学結晶（３８）の位相整合角度に
適合したビーム広がり角度に補正されたレーザビーム
（３７）となり非線形光学結晶（３８）に入射し，２次
高調波（３９）が発生する。２次高調波（３９）はダイ
クロイックミラー（４０）により，基本波成分を除去
し，第２の非線形光学結晶（４３）の位相整合角度に適
合したビーム広がり角度になるように，第２のコリメー
タ（４１）によって補正される。更に円筒レンズ（４
２）で第２の非線形光学結晶（４３）の位相整合方向と
垂直方向に集束され，４次高調波（４４）が発生する。FIG. 9 shows a fourth embodiment of the present invention, in which a laser beam is subjected to wavelength conversion twice to obtain a short-wavelength laser beam at the fourth harmonic. A fundamental laser output light (35) from the laser oscillator (34) is supplied to a first collimator (36).
As a result, a laser beam (37) corrected to a beam spread angle suitable for the phase matching angle of the first nonlinear optical crystal (38) is incident on the nonlinear optical crystal (38), and a second harmonic (39) is generated. . The second harmonic (39) is removed by the dichroic mirror (40) to remove the fundamental wave component, and the second collimator is adjusted so that the beam spread angle matches the phase matching angle of the second nonlinear optical crystal (43). It is corrected by (41). Furthermore, a cylindrical lens (4
In 2), the light is focused in the direction perpendicular to the phase matching direction of the second nonlinear optical crystal (43), and the fourth harmonic (44) is generated.
【００２６】図９の実施例では，２次高調波発生の為に
第１のコリメータでビーム広がり角度を補正したが，レ
ーザ発振器からのレーザ出力光のビーム広がりが小さい
場合には，第１のコリメータを省略しても良い。In the embodiment shown in FIG. 9, the beam spread angle is corrected by the first collimator in order to generate the second harmonic. However, if the beam spread of the laser output light from the laser oscillator is small, the first beam spreads. The collimator may be omitted.
【００２７】図９の実施例では，レーザ光強度が十分な
２次高調波発生については，第一の非線形光学結晶（３
８）に対して，特に集束光学系を用いず平行光のままで
高調波発生を行っている。基本波発振器のレーザ出力光
のビーム直径と出力光強度によって，円筒レンズによっ
て位相整合方向と垂直な方向についての集束光学系を形
成しても良い。In the embodiment shown in FIG. 9, the second nonlinear optical crystal (3
With respect to 8), harmonics are generated with parallel light without using a focusing optical system. A focusing optical system in a direction perpendicular to the phase matching direction may be formed by a cylindrical lens according to the beam diameter of the laser output light from the fundamental wave oscillator and the output light intensity.
【００２８】図９の実施例において，基本波レーザ発振
器がNd-YAGレーザ，Nd-YVO4レーザ，またはNd-YLFレー
ザ等の１μ近傍の波長を有するレーザ光出力であり，第
１の非線形光学結晶がBBOまたはLBOまたはKTPであり，
第２の非線形光学結晶がBBOまたはCLBOを用いる事によ
り260nm近傍の紫外4次高調波を発生する。In the embodiment shown in FIG. 9, the fundamental laser is a laser light output having a wavelength of about 1 μm, such as an Nd-YAG laser, an Nd-YVO4 laser, or an Nd-YLF laser, and the first nonlinear optical crystal. Is BBO or LBO or KTP,
The second nonlinear optical crystal generates an ultraviolet fourth harmonic near 260 nm by using BBO or CLBO.
【００２９】[0029]
【発明の効果】以上説明したように，本発明によれば，
従来の波長変換レーザ装置にあった，変換効率の低さ，
結晶の劣化，装置の複雑化と調整の困難さ等の問題点が
解消され，効率が高く，長寿命で，かつ簡単な光学系の
構成の波長変換レーザ装置を得ることが可能となるもの
である。本発明による波長変換装置により，波長が３０
０ｎｍより短い紫外線レーザ光が容易に得られる。As described above, according to the present invention,
Low conversion efficiency compared to conventional wavelength conversion laser devices,
Problems such as deterioration of crystals, complication of the device and difficulty in adjustment are solved, and it becomes possible to obtain a wavelength conversion laser device having a high efficiency, a long life, and a simple optical system configuration. is there. With the wavelength conversion device according to the present invention, the wavelength
Ultraviolet laser light shorter than 0 nm can be easily obtained.
【図１】一般的な非線形光学結晶を用いた波長変換レー
ザの概略図FIG. 1 is a schematic diagram of a wavelength conversion laser using a general nonlinear optical crystal.
【図２】非線形光学結晶に集束された，レーザビームの
形状FIG. 2 Shape of laser beam focused on nonlinear optical crystal
【図３】円筒レンズを用いて非線形光学結晶にレーザ光
を集束させる概略図FIG. 3 is a schematic diagram of focusing a laser beam on a nonlinear optical crystal using a cylindrical lens.
【図４】外部リング共振器による波長変換光学系の構成
図FIG. 4 is a configuration diagram of a wavelength conversion optical system using an external ring resonator.
【図５】本発明の実施例を説明する為の，光学構成図FIG. 5 is an optical configuration diagram for explaining an embodiment of the present invention.
【図６】本発明の第１の実施例FIG. 6 shows a first embodiment of the present invention.
【図７】本発明の第２の実施例FIG. 7 shows a second embodiment of the present invention.
【図８】本発明の第３の実施例FIG. 8 shows a third embodiment of the present invention.
【図9】本発明の第４の実施例FIG. 9 shows a fourth embodiment of the present invention.
１ レーザ発振器からのレーザ出力光 ２ 凸レンズ ３ 非線形光学結晶 ４ 入射レーザ光の円錐形状 ５ レーザビームが擬似平行の領域 ６ 入射レーザビーム ７ 円筒レンズ ８ 非線形光学結晶 ９ 位相整合方向 １０ 位相整合方向と垂直な方向 １１ ４枚のミラー １２ 非線形光学結晶 １３ レーザ光 １４ 波長変換した出力 １５ レーザ発振器 １６ レーザ出力光 １７ 非線形光学素子 １８ レーザ光の広がり角度 １９ レーザ発振器 ２０ レーザ出力光 ２１ コリメータ光学系 ２２ コリメートされたレーザビーム ２３ 非線形光学結晶 ２４ レーザ発振器 ２５ レーザ出力光 ２６ コリメータ光学系 ２７ コリメートされたレーザビームの広がり角度 ２８ 非線形光学結晶 ２９ レーザ発振器 ３０ コリメータ光学系 ３１ 円筒レンズ ３２ 非線形光学結晶 ３３ 円筒レンズ ３４ レーザ発振器 ３５ レーザ出力光 ３６ 第１のコリメータ光学系 ３７ コリメートされたレーザ光 ３８ 第１の非線形光学結晶 ３９ 発生した２次高調波 ４０ 基本波と２次高調波を分離するダイクロイック光
学系 ４１ 第２のコリメータ光学系 ４２ 円筒レンズ ４３ 第２の非線形光学結晶 ４４ 発生した4次高調波REFERENCE SIGNS LIST 1 laser output light from laser oscillator 2 convex lens 3 nonlinear optical crystal 4 cone shape of incident laser light 5 region where laser beam is pseudo-parallel 6 incident laser beam 7 cylindrical lens 8 nonlinear optical crystal 9 phase matching direction 10 perpendicular to phase matching direction Direction 11 Four mirrors 12 Nonlinear optical crystal 13 Laser light 14 Wavelength-converted output 15 Laser oscillator 16 Laser output light 17 Nonlinear optical element 18 Spread angle of laser light 19 Laser oscillator 20 Laser output light 21 Collimator optical system 22 Collimated Laser beam 23 nonlinear optical crystal 24 laser oscillator 25 laser output light 26 collimator optical system 27 spread angle of collimated laser beam 28 nonlinear optical crystal 29 laser oscillator 30 collimator optical system 31 cylindrical lens 32 nonlinear optical crystal Reference Signs List 33 cylindrical lens 34 laser oscillator 35 laser output light 36 first collimator optical system 37 collimated laser light 38 first nonlinear optical crystal 39 generated second harmonic 40 dichroic optics for separating fundamental wave and second harmonic System 41 Second collimator optical system 42 Cylindrical lens 43 Second nonlinear optical crystal 44 Generated fourth harmonic
Claims (7)
せ，該レーザ発振器の波長とは異なる波長のレーザ光を
得る，波長変換レーザ装置において，該レーザ発振器の
出力光の平行度を高める為のコリメータ光学系を具備す
る事を特徴とする，波長変換レーザ装置。1. A wavelength conversion laser device which combines a laser oscillator and a nonlinear optical crystal to obtain a laser beam having a wavelength different from the wavelength of the laser oscillator, wherein a collimator optics for increasing the parallelism of the output light of the laser oscillator. A wavelength conversion laser device characterized by having a system.
ータ光学系を通過したレーザ光を，前記非線形光学結晶
の位相整合方向と直角な方向に集束する為の円筒レンズ
を具備する事を特徴とする，請求項２の波長変換レーザ
装置。2. The wavelength conversion laser device according to claim 1, further comprising a cylindrical lens for focusing the laser light passing through the collimator optical system in a direction perpendicular to a phase matching direction of the nonlinear optical crystal. The wavelength conversion laser device according to claim 2.
み合わせ，該レーザ発振器のレーザ光を一方の非線形光
学結晶により異なる波長のレーザ光に変換し，さらにそ
のレーザ光を他の非線形光学結晶によりさらに異なる波
長のレーザ光に変換する，波長変換レーザ装置におい
て，２個の非線形光学結晶にレーザ光を入射する光学系
の一方または両方が，前段のレーザ発振器または波長変
換レーザ装置の出力光の平行度を高める為のコリメータ
光学系を有することを特徴とする，波長変換レーザ装
置。3. A laser oscillator and two nonlinear optical crystals are combined, and the laser light of the laser oscillator is converted into laser light of a different wavelength by one nonlinear optical crystal, and the laser light is converted by another nonlinear optical crystal. Further, in a wavelength conversion laser device for converting laser light having different wavelengths, one or both of the optical systems for injecting the laser light into the two nonlinear optical crystals are parallel to the output light of the preceding laser oscillator or the wavelength conversion laser device. A wavelength conversion laser device having a collimator optical system for increasing a degree.
する光学系でコリメータ光学系と，該非線形光学結晶の
位相整合方向と直角な方向に集束する為の円筒レンズを
併用する事を特徴とする，請求項３の波長変換レーザ装
置。4. An optical system for injecting a laser beam into said two nonlinear optical crystals, wherein a collimator optical system and a cylindrical lens for focusing in a direction perpendicular to the phase matching direction of said nonlinear optical crystals are used together. 4. The wavelength conversion laser device according to claim 3, wherein
晶の前段のレーザ発振器またはレーザ装置のビーム広が
り角と該非線形光学結晶の位相整合許容角度の比率の逆
数とする事を特徴とする請求項１，請求項２，請求項３
または請求項４の波長変換レーザ装置。5. The magnification of the collimator optical system is a reciprocal of a ratio between a beam divergence angle of a laser oscillator or a laser device in a stage preceding the nonlinear optical crystal and an allowable angle of phase matching of the nonlinear optical crystal. Claim 1, Claim 2, Claim 3
Alternatively, the wavelength conversion laser device according to claim 4.
ーザまたはNd-YLFレーザであり，非線形光学結晶がBBO
またはLBOまたはKTPであり，レーザ発振器の波長の１／
２の波長のレーザ光を得る事を特徴とする請求項１，請
求項２または請求項５の波長変換レーザ装置。6. The laser oscillator is an Nd-YAG laser, an Nd-YVO4 laser or an Nd-YLF laser, and the nonlinear optical crystal is a BBO.
Or LBO or KTP, which is 1 /
6. The wavelength conversion laser device according to claim 1, wherein a laser beam having a wavelength of 2 is obtained.
ーザまたはNd-YLFレーザであり，第1の非線形光学結晶
がBBOまたはLBOまたはKTPであり，第2の非線形光学結晶
がBBOまたはCLBOであり，レーザ発振器の１／４の波長
のレーザ光を得る事を特徴とする請求項３，請求項４ま
たは請求項５の波長変換レーザ装置。7. The laser oscillator is an Nd-YAG laser, an Nd-YVO4 laser or an Nd-YLF laser, the first nonlinear optical crystal is BBO, LBO or KTP, and the second nonlinear optical crystal is BBO or CLBO. 6. The wavelength conversion laser device according to claim 3, wherein a laser beam having a wavelength one quarter of that of the laser oscillator is obtained.
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| JP2017191324A (en) * | 2012-05-22 | 2017-10-19 | ケーエルエー−テンカー コーポレイション | Solid-state laser and inspection system using 193-nm laser |
| US10199149B2 (en) | 2014-10-03 | 2019-02-05 | Kla-Tencor Corporation | 183NM laser and inspection system |
| US10439355B2 (en) | 2013-02-13 | 2019-10-08 | Kla-Tencor Corporation | 193nm laser and inspection system |
| US10495582B2 (en) | 2014-03-20 | 2019-12-03 | Kla-Tencor Corporation | System and method for reducing the bandwidth of a laser and an inspection system and method using a laser |
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| JPH11258645A (en) * | 1998-03-13 | 1999-09-24 | Sony Corp | Wavelength converting device |
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