JPH05333394A - Wavelength conversion element - Google Patents
Wavelength conversion elementInfo
- Publication number
- JPH05333394A JPH05333394A JP13918092A JP13918092A JPH05333394A JP H05333394 A JPH05333394 A JP H05333394A JP 13918092 A JP13918092 A JP 13918092A JP 13918092 A JP13918092 A JP 13918092A JP H05333394 A JPH05333394 A JP H05333394A
- Authority
- JP
- Japan
- Prior art keywords
- conversion element
- wavelength conversion
- axis
- wavelength
- harmonic
- 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.)
- Pending
Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、光ディスク装置やレー
ザプリンタ等の情報処理機器、あるいは光計測等の光源
部に応用される波長変換素子に関し、特に、レーザ光を
基本波として第２高調波を発生する導波路型の波長変換
素子に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength conversion element applied to an information processing device such as an optical disk device or a laser printer, or a light source section for optical measurement, and more particularly to a second harmonic wave using a laser beam as a fundamental wave. The present invention relates to a waveguide-type wavelength conversion element that generates light.
【０００２】[0002]
【従来の技術】波長変換素子、特に第２高調波発生（Ｓ
ＨＧ）素子は、非線形効果を持つ光学結晶材料を用いて
波長λのレーザ光をλ／２の波長に変換する素子であ
る。従来、ＳＨＧ素子には高出力のコヒーレント光源と
非線形結晶のバルク形素子が用いられてきた。しかし現
在、光ディスク装置やレーザプリンタ装置等を小型化す
る要求が強いため、光源として半導体レーザがガスレー
ザに代わり用いられるようになってきた。この半導体レ
ーザを光源とする場合、その出力が数ｍＷ〜数１０ｍＷ
であるため、高い変換効率を得る必要上、薄膜導波路型
のＳＨＧ素子が用いられている。ここで、従来の導波路
型第２高調波発生素子としては、例えば、(１)特開平２
−２４２２３６号公報、(２)平成３年秋季第５２回応用
物理学会学術講演会予稿集１１ｐ−ＺＮ−９、等に開示
されたものが知られている。図６に従来技術(１)に開示
された導波路型第２高調波発生素子を示す。2. Description of the Related Art Wavelength conversion elements, especially second harmonic generation (S
The (HG) element is an element that converts a laser beam having a wavelength λ into a wavelength of λ / 2 by using an optical crystal material having a nonlinear effect. Conventionally, a high output coherent light source and a bulk element of a non-linear crystal have been used for the SHG element. However, at present, there is a strong demand for miniaturization of optical disk devices, laser printer devices, etc., so that semiconductor lasers have been used as light sources instead of gas lasers. When this semiconductor laser is used as a light source, its output is several mW to several tens mW.
Therefore, a thin film waveguide type SHG element is used in order to obtain high conversion efficiency. Here, as the conventional waveguide type second harmonic generation element, for example, (1)
No. 242236, (2) Autumn 1991, 52nd Annual Meeting of Japan Society of Applied Physics, Proceedings 11p-ZN-9, etc. are known. FIG. 6 shows a waveguide type second harmonic generation element disclosed in the prior art (1).
【０００３】図６において、符号１は非線形材料基板、
Ｇ１は基板１上に形成された導波路、ＺＤ１〜ＺＤｎは
非線形材料からなり且つ非線形分極が導波路の非線形分
極に対して反転している部分である。この素子の作製方
法としては、先ず、フォトリソグラフィー法等により基
板上にチタン（Ｔｉ）の周期的パターンを形成した後、
約１０００℃でＴｉを基板内に拡散することにより周期
的分極反転構造を作製する。次に、アルミニウムをマス
クとして導波路パターンを形成した後、３００℃の安息
香酸中でプロトン交換し、アニーリング処理により３次
元導波路を作製している。このような方法で作製した周
期的分極反転層と３次元導波路により、基本波と第２高
調波の位相を整合させることができ、高効率の波長変換
素子が構成できる。また、従来技術(１)の２番目の実施
例においては、非線形光学材料にＬｉＴａＯ3 結晶を用
いて、周期的分極反転を用いた疑似位相整合により第２
高調波発生を行なっている。In FIG. 6, reference numeral 1 is a nonlinear material substrate,
G1 is a waveguide formed on the substrate 1, ZD1 to ZDn are portions made of a non-linear material, and the non-linear polarization is inverted with respect to the non-linear polarization of the waveguide. As a method for manufacturing this element, first, a periodic pattern of titanium (Ti) is formed on a substrate by a photolithography method or the like,
A periodic domain-inverted structure is produced by diffusing Ti into the substrate at about 1000 ° C. Next, a waveguide pattern is formed using aluminum as a mask, and then proton exchange is performed in benzoic acid at 300 ° C., and a three-dimensional waveguide is manufactured by an annealing treatment. By using the periodically poled layer and the three-dimensional waveguide manufactured by such a method, the phases of the fundamental wave and the second harmonic can be matched, and a highly efficient wavelength conversion element can be constructed. In the second embodiment of the prior art (1), LiTaO 3 crystal is used as the nonlinear optical material, and the second phase is obtained by quasi phase matching using periodic polarization inversion.
Harmonics are being generated.
【０００４】[0004]
【発明が解決しようとする課題】光ディスク装置やレー
ザビームプリンタ等の情報処理機器、あるいは光応用計
測等では、小型でコヒーレントな光源として半導体レー
ザが用いられている。現在用いられている半導体レーザ
の発振波長は７８０ｎｍ、８３０ｎｍ等の近赤外光であ
るが、近年レーザ光の短波長化が進められている。例え
ば、光ディスク装置では、波長を短くすることによりレ
ーザ光のスポット径を小さくすることができるため、光
ディスクに書き込む情報量を増大させることが可能にな
る。また、レーザビームプリンタでは、波長を短くする
ことにより、微小画像を形成することができるため記録
密度を増大させることができ、解像度を向上させること
が可能になる。また、光応用計測では、波長を短くする
ことにより、計測精度の向上が可能になる。しかし、発
振波長が６００ｎｍ台の半導体レーザは得られている
が、緑色、青色光を室温で直接連続発振する半導体レー
ザは現在実現されていない。従って、緑色、青色光領域
のレーザ光はアルゴンイオンレーザ等の大型気体レーザ
によってしか得ることができなかった。A semiconductor laser is used as a compact and coherent light source in information processing equipment such as an optical disk device and a laser beam printer, or optical application measurement. The oscillation wavelength of the semiconductor laser currently used is near-infrared light of 780 nm, 830 nm, etc., but in recent years, the wavelength of laser light has been shortened. For example, in the optical disc device, the spot diameter of the laser beam can be reduced by shortening the wavelength, so that the amount of information written on the optical disc can be increased. Further, in the laser beam printer, by shortening the wavelength, a minute image can be formed, so that the recording density can be increased and the resolution can be improved. Further, in the optical applied measurement, the measurement accuracy can be improved by shortening the wavelength. However, although a semiconductor laser having an oscillation wavelength of about 600 nm has been obtained, a semiconductor laser that directly continuously oscillates green and blue lights at room temperature has not been realized at present. Therefore, the laser light in the green and blue light regions can be obtained only by a large gas laser such as an argon ion laser.
【０００５】そこで、このような大型レーザを用いるこ
と無く緑色、青色光領域のレーザ光を得るためには、前
述したように、非線形光学材料を用いた波長変換素子
（第２高調波発生素子）によりレーザ光を波長変換する
ことにより実現することが可能である。ここで、従来例
の方法で作製された第２高調波発生素子は、周期的分極
反転層を用いて基本波と第２高調波の位相を整合させて
いる。しかし、この場合、基本波の波長が設計波長から
変差している場合、従来例の第２高調波発生素子は基本
波に対する波長許容幅が０．３５ｎｍ程度と小さいた
め、第２高調波発生の位相整合条件がずれ、効率が低く
なるという欠点があった。本発明は上記事情に鑑みてな
されたものであって、安定に第２高調波を発生すること
のできる波長変換素子を実現することを目的とする。Therefore, in order to obtain laser light in the green and blue light regions without using such a large laser, as described above, a wavelength conversion element (second harmonic generation element) using a nonlinear optical material is used. Can be realized by converting the wavelength of the laser light. Here, in the second harmonic generation element manufactured by the method of the conventional example, the phases of the fundamental wave and the second harmonic are matched by using the periodically poled layer. However, in this case, when the wavelength of the fundamental wave is changed from the design wavelength, the second harmonic generation element of the conventional example has a small wavelength permissible width for the fundamental wave of about 0.35 nm. There is a drawback that the phase matching condition is deviated and the efficiency is lowered. The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a wavelength conversion element that can stably generate a second harmonic.
【０００６】[0006]
【課題を解決するための手段】上記目的を達成するた
め、請求項１の発明では、所定波長を有する基本波レー
ザ光を基板上または基板中に形成した非線形媒質からな
る３次元導波路内を通過させて高調波レーザ光を発生さ
せる波長変換素子において、形状の異なった複数本の３
次元導波路を有していることを特徴とする。In order to achieve the above object, in the invention of claim 1, the inside of a three-dimensional waveguide made of a non-linear medium in which a fundamental laser beam having a predetermined wavelength is formed on or in a substrate. In a wavelength conversion element that passes through and generates a harmonic laser beam, a plurality of 3
It is characterized by having a dimensional waveguide.
【０００７】請求項２の発明は、上記請求項１の波長変
換素子において、基本波レーザ光の波長をλとすると
き、基本波に対する導波モード光の伝搬定数をβ(λ)、
前記基本波の第２高調波に対する導波モード光に対する
伝搬定数をβ(λ／２)、そしてｍを自然数とすると、 Λ＝２(２ｍ−１)π／{β(λ／２)−２β(λ)} なる関係を満たすような周期Λの分極反転構造を第２高
調波発生部分に有していることを特徴とする。According to a second aspect of the present invention, in the wavelength conversion element according to the first aspect, when the wavelength of the fundamental laser light is λ, the propagation constant of the guided mode light with respect to the fundamental wave is β (λ),
When the propagation constant for the guided mode light for the second harmonic of the fundamental wave is β (λ / 2) and m is a natural number, Λ = 2 (2m−1) π / {β (λ / 2) −2β It is characterized in that it has a domain-inverted structure with a period Λ in the second harmonic generation portion so as to satisfy the relation (λ)}.
【０００８】また、請求項３の発明は、請求項２の波長
変換素子において、基板として非線形媒質ＬｉＴａＯ3
の−ｃ板を用いて、光の伝搬方向をｙ軸とし、これに垂
直なｚ軸を基板の−ｃ軸方向に合わせたとき、基本波に
電界方向がｚ軸に平行な偏波、第２高調波にｚ軸に平行
な偏波を用いたことを特徴とする。また、請求項４の発
明は、請求項２の波長変換素子において、基板として非
線形媒質ＬｉＮｂＯ3 のｃ板を用いて、光の伝搬方向を
ｙ軸とし、これに垂直なｚ軸を基板のｃ軸方向に合わせ
たとき、基本波に電界方向がｚ軸に平行な偏波、第２高
調波にｚ軸に平行な偏波を用いたことを特徴とする。According to a third aspect of the invention, in the wavelength conversion element of the second aspect, the nonlinear medium LiTaO 3 is used as the substrate.
When the y-axis is used as the light propagation direction and the z-axis perpendicular to this is aligned with the -c-axis direction of the substrate by using the -c plate of No. 3, the polarization in which the electric field direction is parallel to the z-axis to the fundamental wave, It is characterized in that polarized waves parallel to the z-axis are used for the two harmonics. According to a fourth aspect of the present invention, in the wavelength conversion element of the second aspect, a c-plate of a non-linear medium LiNbO 3 is used as a substrate, the light propagation direction is the y-axis, and the z-axis perpendicular thereto is the c-axis of the substrate. When aligned in the axial direction, a polarized wave whose electric field direction is parallel to the z axis is used for the fundamental wave, and a polarized wave parallel to the z axis is used for the second harmonic.
【０００９】請求項５の発明は、請求項１の波長変換素
子において、基板として非線形媒質ＬｉＮｂＯ3 のｃ板
を用いて、光の伝搬方向をｘ軸とし、基本波に電界方向
がｙ軸方向に平行な偏波、第２高調波に電界方向がｚ軸
に平行な偏波を用い、位相整合に非線形媒質ＬｉＮｂＯ
3 の複屈折性を用いたことを特徴とする。また、請求項
６の発明は、請求項２の波長変換素子において、異なっ
た周期Λを持つ複数個の分極反転構造を第２高調波発生
部分に有していることを特徴とする。According to a fifth aspect of the present invention, in the wavelength conversion element of the first aspect, a c-plate of a non-linear medium LiNbO 3 is used as a substrate, the light propagation direction is the x-axis, and the electric field direction of the fundamental wave is the y-axis direction. Parallel polarization to the second harmonic, the polarization of the electric field parallel to the z-axis to the second harmonic is used, and the nonlinear medium LiNbO is used for phase matching.
It is characterized by using birefringence of 3 . The invention of claim 6 is characterized in that, in the wavelength conversion element of claim 2, a plurality of polarization inversion structures having different periods Λ are included in the second harmonic generation part.
【００１０】[0010]
【作用】本発明では、所定波長を有する基本波レーザ光
を基板上または基板中に形成した非線形媒質からなる３
次元導波路内を通過させて高調波レーザ光を発生させる
波長変換素子において、形状の異なった複数本の３次元
導波路を有していることにより、基本波の波長変差に対
する許容幅を拡大することができ、従来よりも安定に第
２高調波を発生させることが実現できる。さらに、基本
波レーザ光の波長をλとするとき、基本波に対する導波
モード光の伝搬定数をβ(λ)、前記基本波の第２高調波
に対する導波モード光に対する伝搬定数をβ(λ／２)、
そしてｍを自然数とすると、 Λ＝２(２ｍ−１)π／{β(λ／２)−２β(λ)} なる関係を満たすような周期Λの分極反転構造を第２高
調波発生部分に有することにより、周期的分極反転構造
により第２高調波発生を行なう非線形媒質の種類をふや
すことが可能になる。また、位相整合可能な波長領域が
広がる。According to the present invention, the fundamental wave laser beam having a predetermined wavelength is formed on the substrate or in the substrate and is composed of a nonlinear medium.
A wavelength conversion element that generates harmonic laser light by passing through a three-dimensional waveguide has a plurality of three-dimensional waveguides with different shapes, thereby increasing the allowable width for the wavelength variation of the fundamental wave. Therefore, it is possible to generate the second harmonic wave more stably than before. Further, where the wavelength of the fundamental laser light is λ, the propagation constant of the guided mode light with respect to the fundamental wave is β (λ), and the propagation constant of the guided mode light with respect to the second harmonic of the fundamental wave is β (λ / 2),
When m is a natural number, a domain-inverted structure with a period Λ that satisfies the relationship of Λ = 2 (2m-1) π / {β (λ / 2) -2β (λ)} is used as the second harmonic generation part. With this structure, it is possible to increase the types of nonlinear media that generate the second harmonic due to the periodically poled structure. In addition, the wavelength range in which phase matching is possible is expanded.
【００１１】[0011]
【実施例】以下、本発明を図示の実施例に基づいて詳細
に説明する。図１は本発明の一実施例を示す波長変換素
子の斜視図である。図１において、符号１は非線形材料
ＬｉＴａＯ3 からなる単結晶基板であり、基板方位は−
ｃ板である。また、符号２，３，４，５は基板１上に作
製した基板１よりも高い屈折率を持った３次元導波路、
６は非線形分極が周期的に反転している分極反転領域で
ある。尚、上記実施例の他に、ＬｉＮｂＯ3 基板や、Ｍ
ｇＯをドープしたＬｉＮｂＯ3 基板、ＫＴｉＯＰＯ4 基
板でも実現可能である。ここで、３次元導波路を導波す
る基本波の波長をλ、前記基本波に対する伝搬定数をβ
(λ)、前記基本波に対する第２高調波の伝搬定数をβ
(λ／２)、そしてｍを自然数とすると、 β(λ／２)−２β(λ)＝２(２ｍ−１)π／Λ なる関係を満たすように、３次元導波路の光伝搬方向に
分極反転の周期Λを設けることにより効率良く第２高調
波を発生させることができる。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the illustrated embodiments. FIG. 1 is a perspective view of a wavelength conversion element showing an embodiment of the present invention. In FIG. 1, reference numeral 1 is a single crystal substrate made of the nonlinear material LiTaO 3 , and the substrate orientation is −.
c plate. Reference numerals 2, 3, 4, 5 are three-dimensional waveguides having a higher refractive index than the substrate 1 formed on the substrate 1,
Reference numeral 6 is a domain-inverted region in which the nonlinear polarization is periodically inverted. In addition to the above embodiment, a LiNbO 3 substrate, M
It can also be realized by using a LiNbO 3 substrate doped with gO or a KTiOPO 4 substrate. Here, the wavelength of the fundamental wave guided through the three-dimensional waveguide is λ, and the propagation constant for the fundamental wave is β
(λ), the propagation constant of the second harmonic with respect to the fundamental wave is β
(λ / 2), and m is a natural number, in the light propagation direction of the three-dimensional waveguide so that the relationship β (λ / 2) -2β (λ) = 2 (2m-1) π / Λ is satisfied. By providing the polarization inversion period Λ, the second harmonic can be efficiently generated.
【００１２】上記波長変換素子の作製法としては、Ｌｉ
ＴａＯ3 の−ｃ板を洗浄後、Ｔａを用いて図１の分極反
転領域６形成部分以外の基板上をマスクし、周期的パタ
ーンを形成した後、ピロリン酸あるいは安息香酸等の溶
液中で約２６０℃の温度でプロトン交換を行なう。その
後、弗硝酸の混合液でＴａマスクを除去した後、ＬｉＴ
ａＯ3 結晶のキュリー点直下の温度（６００℃）で熱処
理することによりマスクされていない部分に分極が反転
した領域が形成される。この分極反転領域６の厚さは、
プロトン交換時間、熱処理時間等を変化させることによ
り調整できる。As a method for producing the above wavelength conversion element, Li is used.
After washing the TaO 3 -c plate, Ta was used to mask the substrate other than the portion where the domain-inverted regions 6 were formed in FIG. 1 to form a periodic pattern, which was then washed with a solution of pyrophosphoric acid or benzoic acid. Proton exchange is carried out at a temperature of 260 ° C. Then, after removing the Ta mask with a mixed solution of fluorinated nitric acid, LiT
By subjecting the aO 3 crystal to a heat treatment just below the Curie point (600 ° C.), a region where the polarization is inverted is formed in the unmasked portion. The thickness of this domain inversion region 6 is
It can be adjusted by changing the proton exchange time, heat treatment time and the like.
【００１３】分極反転領域形成後、３次元導波路２，
３，４，５は、Ｔａを用いて３次元導波路部分上面以外
をマスクした後、ピロリン酸、安息香酸等の溶液中で約
２６０℃程度の温度でプロトン交換することにより、マ
スクされていない部分に高屈折率層が形成されることに
より作製できる。ここで、マスクの３次元導波路部分の
幅を変えることにより、形成された導波路の幅は調整で
きるので、導波路２，３，４，５の幅はそれぞれ変えて
ある。さらに、導波路の数は上記実施例のように４本で
はなく複数本あってよい。また、Ｒｂ，Ｃｓ，Ａｇ等の
金属を約３００〜４００℃付近で拡散することによって
も３次元導波路を作製することが可能である。さらに、
基板にＫＴｉＯＰＯ4 結晶のｚ板を用いた場合には、Ｒ
ｂＮＯ3／Ｂａ(ＮＯ3)2の溶融塩をイオン源にすること
により、イオン交換により上記同様の３次元導波路が作
製可能である。これらの３次元導波路は単一モード導波
路であることが望ましい。After the domain inversion region is formed, the three-dimensional waveguide 2,
Nos. 3, 4, and 5 are not masked by masking parts other than the upper surface of the three-dimensional waveguide portion with Ta, and then exchanging protons in a solution of pyrophosphoric acid, benzoic acid, etc. at a temperature of about 260 ° C. It can be manufactured by forming a high refractive index layer in the portion. Since the width of the formed waveguide can be adjusted by changing the width of the three-dimensional waveguide portion of the mask, the widths of the waveguides 2, 3, 4, and 5 are changed. Further, the number of waveguides may be plural instead of four as in the above embodiment. It is also possible to fabricate a three-dimensional waveguide by diffusing metals such as Rb, Cs, and Ag at around 300 to 400 ° C. further,
When a KTiOPO 4 crystal z-plate is used as the substrate, R
By using a molten salt of bNO 3 / Ba (NO 3 ) 2 as an ion source, a three-dimensional waveguide similar to the above can be produced by ion exchange. These three-dimensional waveguides are preferably single mode waveguides.
【００１４】また、３次元導波路はＴｉ，Ｃｕ等を約１
０００℃程度の温度で拡散することによっても作製でき
る。この場合、基板にＬｉＮｂＯ3 結晶を用いた場合に
は、そのキュリー点が約１１００℃であるのでポーリン
グを行なって分極方向を揃える必要は無いが、ＬｉＴａ
Ｏ3 結晶を用いた場合には、キュリー点が約６００℃で
あるので、３次元導波路作製後、結晶のｃ軸方向にキュ
リー点近くの温度で電界を印加し分極を揃える必要があ
る。また、ＬｉＴａＯ3 結晶は、光損傷しきい値が高い
ため光損傷に強い特徴がある。The three-dimensional waveguide contains Ti, Cu, etc. at about 1
It can also be manufactured by diffusing at a temperature of about 000 ° C. In this case, when a LiNbO 3 crystal is used as the substrate, its Curie point is about 1100 ° C., so it is not necessary to perform poling to align the polarization directions.
When an O 3 crystal is used, the Curie point is about 600 ° C., and therefore, it is necessary to apply an electric field in the c-axis direction of the crystal at a temperature near the Curie point to make the polarization uniform after manufacturing the three-dimensional waveguide. In addition, the LiTaO 3 crystal has a high optical damage threshold value and thus has a characteristic of being highly resistant to optical damage.
【００１５】上記実施例において、ＬｉＴａＯ3 結晶を
用いた場合、波長０．８３μｍの基本波では基板の屈折
率の波長分散は、常光に相当する電界方向がｘ方向を向
いているＥx00 モードを用いた場合で２．１５３８、異
常光に相当する電界方向がｚ方向を向いているＥz00 モ
ードを用いた場合で２．１５７８、波長０．４１５μｍ
の第２高調波の波長では常光に相当する電界方向がｘ方
向を向いているＥx00モードを用いた場合で２．２４１
４、異常光に相当する電界方向がｚ方向を向いているＥ
z00 モードを用いた場合で２．２８１４である。ここ
で、導波路深さが２．０μｍ、導波路と基板との間の屈
折率差が０．０１ある場合の、Ｅz00 モードの基本波の
波長０．８３μｍにおける、導波路幅に対する等価屈折
率分散は図２のようになる。また、Ｅz00 モードの基本
波の波長０．４１５μｍにおける導波路幅に対する等価
屈折率分散は図３のようになる。In the above embodiment, when LiTaO 3 crystal is used, the wavelength dispersion of the refractive index of the substrate in the fundamental wave having a wavelength of 0.83 μm is the Ex 00 mode in which the electric field direction corresponding to ordinary light is in the x direction. 2.1538 when used, 2.1578 when Ez 00 mode in which the electric field direction corresponding to extraordinary light is in the z direction, and wavelength 0.415 μm
2.241 in the case of using the Ex 00 mode in which the electric field direction corresponding to ordinary light is in the x direction at the wavelength of the second harmonic of
4. The electric field direction corresponding to extraordinary light is in the z direction E
It is 2.2814 when the z 00 mode is used. Here, when the waveguide depth is 2.0 μm and the refractive index difference between the waveguide and the substrate is 0.01, the equivalent refraction with respect to the waveguide width at the wavelength of the fundamental wave of Ez 00 mode is 0.83 μm. The rate dispersion is as shown in FIG. Also, the equivalent refractive index dispersion with respect to the waveguide width at the wavelength of the fundamental wave of the Ez 00 mode at 0.415 μm is as shown in FIG.
【００１６】上記実施例において、基本波に対する等価
屈折率をＮ(λ)、前記基本波の第２高調波に対する等価
屈折率をＮ(λ／２)、ｍを自然数とすると、 β(λ／２)−２β(λ)＝２(２ｍ−１)π／Λ β(λ)＝２πＮ(λ)／λ から、 Λ＝２(２ｍ−１)π／{β(λ／２)−２β(λ)} =(２ｍ−１)λ／２{Ｎ(λ／２)−Ｎ(λ)} の関係を満たす周期Λμｍの分極反転構造があれば高効
率な第２高調波の発生が得られる。In the above embodiment, when the equivalent refractive index for the fundamental wave is N (λ), the equivalent refractive index for the second harmonic of the fundamental wave is N (λ / 2), and m is a natural number, β (λ / 2) -2β (λ) = 2 (2m-1) π / Λ β (λ) = 2πN (λ) / λ From Λ = 2 (2m-1) π / {β (λ / 2) -2β ( λ)} = (2m-1) λ / 2 {N (λ / 2) -N (λ)} with a domain-inverted structure with a period Λμm, the highly efficient generation of the second harmonic can be obtained. ..
【００１７】ここで、導波路幅が５．０μｍで、基本波
に波長０．８３μｍのＥz00 モードを用い、第２高調波
に波長０．４１５μｍのＥz00 モードを用いた場合、１
次の疑似位相整合を行なうための分極反転の周期は３．
２４μｍ、３次の疑似位相整合を行なうための分極反転
の周期は９．７２μｍになる。プロトン交換導波路では
Ｅz00 モードのみが導波するので、このような偏波を用
いる必要がある。ここでは、図１に示す実施例のよう
に、上記の周期で分極反転領域６を形成し、導波路２は
３．０μｍ、導波路３は４．０μｍ、導波路４は５．０
μｍ、導波路５は６．０μｍのように導波路幅を変化さ
せた。ここで各導波路における基本波と第２高調波の等
価屈折率は、図２、図３で示すような分散を示す。従っ
て、導波路２では位相整合がとれる基本波の波長が０．
８３４６μｍ、導波路３では０．８３１５μｍ、導波路
５では０．８２８６μｍであるので、±０．００５μｍ
程度の基本波の波長に対する変差は導波路を選択するこ
とにより補償できる。導波路の選択は微動台を用いて端
面から入射したり、プリズムカプラーを用いて選択的に
導波光を励起することによって実現できる。さらに、よ
り大きい範囲に渡って、より細かい間隔で導波路幅を変
化させることにより、より基本波に対する位相整合許容
幅を広げることが可能である。また、このような構造
は、前記導波路作製法によって作製可能である。Here, when the waveguide width is 5.0 μm and the Ez 00 mode having a wavelength of 0.83 μm is used for the fundamental wave and the Ez 00 mode having a wavelength of 0.415 μm is used for the second harmonic, 1
The period of the polarization inversion for the next quasi phase matching is 3.
The period of the polarization inversion for performing the third-order quasi phase matching of 24 μm is 9.72 μm. Since only the Ez 00 mode is guided in the proton exchange waveguide, it is necessary to use such polarization. Here, as in the embodiment shown in FIG. 1, the domain-inverted regions 6 are formed with the above-described period, the waveguide 2 is 3.0 μm, the waveguide 3 is 4.0 μm, and the waveguide 4 is 5.0 μm.
μm, and the waveguide 5 has a waveguide width changed to 6.0 μm. Here, the equivalent refractive index of the fundamental wave and the second harmonic in each waveguide exhibits dispersion as shown in FIGS. Therefore, in the waveguide 2, the wavelength of the fundamental wave that is phase-matched is 0.
8346 μm, 0.8315 μm in the waveguide 3, and 0.8286 μm in the waveguide 5, so ± 0.005 μm
The variation of the fundamental wave with respect to the wavelength can be compensated by selecting a waveguide. The selection of the waveguide can be realized by using a fine movement stage to make the light incident from the end face or by using a prism coupler to selectively excite the guided light. Furthermore, by changing the waveguide width at a finer interval over a larger range, it is possible to further widen the phase matching allowable width for the fundamental wave. Further, such a structure can be manufactured by the above-mentioned waveguide manufacturing method.
【００１８】また、上記実施例の他に、図４に示すよう
に、基板にＬｉＮｂＯ3 結晶のｚ板を用いても同様な効
果を得ることが可能である。また、基本波の波長が１．
０μｍ以上である場合には、周期的分極反転層が無くて
も位相整合が可能である。この場合、素子は図４の周期
分極反転層６が無い構造になる。さらに図５に示すよう
に、導波方向に、周期Λを変えた分極反転構造６を複数
個形成することにより、基本波の波長変化許容幅をより
広くすることが可能になる。In addition to the above-mentioned embodiment, the same effect can be obtained by using a z-plate of LiNbO 3 crystal as the substrate as shown in FIG. The wavelength of the fundamental wave is 1.
When the thickness is 0 μm or more, phase matching is possible without the periodic domain inversion layer. In this case, the device has a structure without the periodic domain inversion layer 6 shown in FIG. Further, as shown in FIG. 5, by forming a plurality of polarization inversion structures 6 having different periods Λ in the waveguiding direction, it is possible to further widen the wavelength variation permissible width of the fundamental wave.
【００１９】[0019]
【発明の効果】以上説明したように、請求項１の発明で
は、所定波長を有する基本波レーザ光を基板上または基
板中に形成した非線形媒質からなる３次元導波路内を通
過させて高調波レーザ光を発生させる波長変換素子にお
いて、形状の異なった複数本の３次元導波路を有してい
ることにより、基本波の波長変差に対する許容幅を拡大
することができ、従来よりも安定に第２高調波を発生さ
せることが実現できる。また、従来のガスレーザよりも
小型化が図れ、さらに同一基板上に大量に作製可能であ
るのでコストダウンが図れる。As described above, according to the first aspect of the invention, the fundamental wave laser light having a predetermined wavelength is passed through the three-dimensional waveguide formed of the non-linear medium formed on or in the substrate to generate the harmonic wave. Since the wavelength conversion element that generates the laser light has a plurality of three-dimensional waveguides having different shapes, it is possible to expand the allowable range for the wavelength variation of the fundamental wave, and more stable than before. Generation of the second harmonic can be realized. Further, the gas laser can be downsized as compared with the conventional gas laser, and since a large amount can be manufactured on the same substrate, the cost can be reduced.
【００２０】請求項２の波長変換素子においては、基本
波レーザ光の波長をλとするとき、基本波に対する導波
モード光の伝搬定数をβ(λ)、前記基本波の第２高調波
に対する導波モード光に対する伝搬定数をβ(λ／２)、
そしてｍを自然数とすると、 Λ＝２(２ｍ−１)π／{β(λ／２)−２β(λ)} なる関係を満たすような周期Λの分極反転構造を第２高
調波発生部分に有することにより、請求項１の効果に加
えて、周期的分極反転構造により第２高調波発生を行な
う非線形媒質の種類をふやすことが可能になる。また、
位相整合可能な波長領域が広がる。In the wavelength conversion element of claim 2, when the wavelength of the fundamental wave laser light is λ, the propagation constant of the guided mode light with respect to the fundamental wave is β (λ), and with respect to the second harmonic of the fundamental wave. The propagation constant for guided mode light is β (λ / 2),
When m is a natural number, a domain-inverted structure with a period Λ that satisfies the relation of Λ = 2 (2m-1) π / {β (λ / 2) -2β (λ)} is used as the second harmonic generation part. With this, in addition to the effect of claim 1, it is possible to increase the types of nonlinear media that generate the second harmonic due to the periodically poled structure. Also,
The wavelength range in which phase matching is possible expands.
【００２１】請求項３の波長変換素子においては、請求
項１，２の効果に加えて、非線形媒質にＬｉＴａＯ3 結
晶を用いることにより、安定に周期的分極反転層を形成
できる。また光損傷に強いため、より安定に第２高調波
を発生させることができる。In the wavelength conversion element of claim 3, in addition to the effects of claims 1 and 2, by using LiTaO 3 crystal as the nonlinear medium, the periodically poled layer can be stably formed. Further, since it is resistant to optical damage, it is possible to more stably generate the second harmonic.
【００２２】請求項４の波長変換素子においては、請求
項１，２の効果に加えて、非線形媒質にＬｉＮｂＯ3 結
晶を用いることにより、より低コストで波長変換素子が
実現できる。According to the wavelength conversion element of claim 4, in addition to the effects of claims 1 and 2, the wavelength conversion element can be realized at a lower cost by using LiNbO 3 crystal for the nonlinear medium.
【００２３】請求項５の波長変換素子においては、請求
項１の効果に加えて、直接モード間の位相整合がとれる
ため、高効率化が図れる。また、製造工程の軽減による
コストダウンが図れる。In the wavelength conversion element of the fifth aspect, in addition to the effect of the first aspect, the phase matching between the direct modes can be achieved, so that the efficiency can be improved. Further, the cost can be reduced by reducing the manufacturing process.
【００２４】請求項６の波長変換素子においては、請求
項１，２の効果に加えて、基本波の波長変差に対する許
容幅をさらに拡大することができ、より安定に第２高調
波を発生させることが実現できる。In the wavelength conversion element of claim 6, in addition to the effects of claims 1 and 2, the allowable range for the wavelength variation of the fundamental wave can be further expanded, and the second harmonic wave can be generated more stably. Can be realized.
【図１】本発明の一実施例を示す波長変換素子の斜視図
である。FIG. 1 is a perspective view of a wavelength conversion element showing an embodiment of the present invention.
【図２】図１に示す波長変換素子において、導波路深さ
が２．０μｍ、導波路と基板との間の屈折率差が０．０
１ある場合の、Ｅz00 モードの基本波の波長０．８３μ
ｍにおける、導波路幅に対する等価屈折率を示す図であ
る。FIG. 2 is a wavelength conversion element shown in FIG. 1, in which the waveguide depth is 2.0 μm and the refractive index difference between the waveguide and the substrate is 0.0.
When there is 1, the fundamental wave wavelength of Ez 00 mode is 0.83μ
It is a figure which shows the equivalent refractive index with respect to the waveguide width in m.
【図３】図１に示す波長変換素子において、導波路深さ
が２．０μｍ、導波路と基板との間の屈折率差が０．０
１ある場合の、Ｅz00 モードの基本波の波長０．４１５
μｍにおける導波路幅に対する等価屈折率を示す図であ
る。FIG. 3 shows a wavelength conversion element shown in FIG. 1 having a waveguide depth of 2.0 μm and a refractive index difference of 0.0 between the waveguide and the substrate.
When there is 1, the wavelength of the fundamental wave of Ez 00 mode is 0.415
It is a figure which shows the equivalent refractive index with respect to the waveguide width in (micrometer).
【図４】本発明の別の実施例を示す波長変換素子の斜視
図である。FIG. 4 is a perspective view of a wavelength conversion element showing another embodiment of the present invention.
【図５】本発明のさらに別の実施例を示す波長変換素子
の斜視図である。FIG. 5 is a perspective view of a wavelength conversion element showing still another embodiment of the present invention.
【図６】従来技術の一例を示す導波路型第２高調波発生
素子の斜視図である。FIG. 6 is a perspective view of a waveguide type second harmonic generation element showing an example of a conventional technique.
１・・・基板 ２，３，４，５・・・３次元導波路 ６・・・分極反転領域（分極反転層） 1 ... Substrate 2, 3, 4, 5 ... Three-dimensional waveguide 6 ... Polarization inversion region (polarization inversion layer)
Claims (6)
または基板中に形成した非線形媒質からなる３次元導波
路内を通過させて高調波レーザ光を発生させる波長変換
素子において、形状の異なった複数本の３次元導波路を
有していることを特徴とする波長変換素子。1. A wavelength conversion element for generating a harmonic laser light by passing a fundamental wave laser light having a predetermined wavelength through a three-dimensional waveguide made of a non-linear medium formed on or in a substrate, and having a different shape. A wavelength conversion element having a plurality of three-dimensional waveguides.
本波レーザ光の波長をλとするとき、基本波に対する導
波モード光の伝搬定数をβ(λ)、前記基本波の第２高調
波に対する導波モード光に対する伝搬定数をβ(λ／
２)、そしてｍを自然数とすると、 Λ＝２(２ｍ−１)π／{β(λ／２)−２β(λ)} なる関係を満たすような周期Λの分極反転構造を第２高
調波発生部分に有していることを特徴とする波長変換素
子。2. The wavelength conversion element according to claim 1, wherein when the wavelength of the fundamental wave laser light is λ, the propagation constant of the guided mode light with respect to the fundamental wave is β (λ), and the second harmonic of the fundamental wave. The propagation constant for the guided mode light for the wave is β (λ /
2), and when m is a natural number, a polarization inversion structure with a period Λ that satisfies the relation of Λ = 2 (2m-1) π / {β (λ / 2) -2β (λ)} A wavelength conversion element characterized in that it is included in the generation part.
板として非線形媒質ＬｉＴａＯ3 の−ｃ板を用いて、光
の伝搬方向をｙ軸とし、これに垂直なｚ軸を基板の−ｃ
軸方向に合わせたとき、基本波に電界方向がｚ軸に平行
な偏波、第２高調波にｚ軸に平行な偏波を用いたことを
特徴とする波長変換素子。3. The wavelength conversion element according to claim 2, wherein a -c plate of a non-linear medium LiTaO 3 is used as a substrate, the light propagation direction is defined as the y axis, and the z axis perpendicular to this is the -c of the substrate.
A wavelength conversion element characterized in that, when aligned in the axial direction, a polarized wave whose electric field direction is parallel to the z-axis is used for the fundamental wave and a polarized wave parallel to the z-axis is used for the second harmonic.
板として非線形媒質ＬｉＮｂＯ3 のｃ板を用いて、光の
伝搬方向をｙ軸とし、これに垂直なｚ軸を基板のｃ軸方
向に合わせたとき、基本波に電界方向がｚ軸に平行な偏
波、第２高調波にｚ軸に平行な偏波を用いたことを特徴
とする波長変換素子。4. The wavelength conversion element according to claim 2, wherein a c-plate of a non-linear medium LiNbO 3 is used as the substrate, the light propagation direction is the y-axis, and the z-axis perpendicular to this is the c-axis direction of the substrate. A wavelength conversion element characterized in that, when combined, a polarized wave whose electric field direction is parallel to the z-axis is used for the fundamental wave and a polarized wave parallel to the z-axis is used for the second harmonic.
板として非線形媒質ＬｉＮｂＯ3 のｃ板を用いて、光の
伝搬方向をｘ軸とし、基本波に電界方向がｙ軸方向に平
行な偏波、第２高調波に電界方向がｚ軸に平行な偏波を
用い、位相整合に非線形媒質ＬｉＮｂＯ3 の複屈折性を
用いたことを特徴とする波長変換素子。5. The wavelength conversion element according to claim 1, wherein a c-plate of a non-linear medium LiNbO 3 is used as a substrate, the propagation direction of light is the x-axis, and the electric field direction is parallel to the fundamental wave in the y-axis direction. A wavelength conversion element characterized in that a polarized wave whose electric field direction is parallel to the z axis is used for a wave and a second harmonic, and birefringence of a nonlinear medium LiNbO 3 is used for phase matching.
なった周期Λを持つ複数個の分極反転構造を第２高調波
発生部分に有していることを特徴とする波長変換素子。6. The wavelength conversion element according to claim 2, wherein the second harmonic generation portion has a plurality of polarization inversion structures having different periods Λ.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13918092A JPH05333394A (en) | 1992-05-29 | 1992-05-29 | Wavelength conversion element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13918092A JPH05333394A (en) | 1992-05-29 | 1992-05-29 | Wavelength conversion element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05333394A true JPH05333394A (en) | 1993-12-17 |
Family
ID=15239430
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13918092A Pending JPH05333394A (en) | 1992-05-29 | 1992-05-29 | Wavelength conversion element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05333394A (en) |
-
1992
- 1992-05-29 JP JP13918092A patent/JPH05333394A/en active Pending
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