JP3006217B2 - Optical wavelength conversion element and method of manufacturing the same - Google Patents
Optical wavelength conversion element and method of manufacturing the sameInfo
- Publication number
- JP3006217B2 JP3006217B2 JP3255161A JP25516191A JP3006217B2 JP 3006217 B2 JP3006217 B2 JP 3006217B2 JP 3255161 A JP3255161 A JP 3255161A JP 25516191 A JP25516191 A JP 25516191A JP 3006217 B2 JP3006217 B2 JP 3006217B2
- Authority
- JP
- Japan
- Prior art keywords
- domain
- layer
- inverted layer
- optical
- wavelength conversion
- 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.)
- Expired - Fee Related
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/355—Non-linear optics characterised by the materials used
- G02F1/3558—Poled materials, e.g. with periodic poling; Fabrication of domain inverted structures, e.g. for quasi-phase-matching [QPM]
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/37—Non-linear optics for second-harmonic generation
- G02F1/377—Non-linear optics for second-harmonic generation in an optical waveguide structure
- G02F1/3775—Non-linear optics for second-harmonic generation in an optical waveguide structure with a periodic structure, e.g. domain inversion, for quasi-phase-matching [QPM]
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
- G02F1/3544—Particular phase matching techniques
- G02F1/3548—Quasi phase matching [QPM], e.g. using a periodic domain inverted structure
Description
【０００１】[0001]
【産業上の利用分野】本発明は、コヒーレント光を利用
する光情報処理分野、あるいは光応用計測制御分野に使
用する光波長変換素子およびその製造方法に関するもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength conversion element used in the field of optical information processing using coherent light or in the field of optical measurement and control, and a method of manufacturing the same.
【０００２】[0002]
【従来の技術】図４に従来の光導波路を基本とした光波
長変換素子の構成図を示す。以下0.84μｍの波長の基本
波に対する高調波発生（波長0.42μｍ）について図を用
いて詳しく述べる。（K.Mizuuchi, K.Yamamoto and T.T
aniuchi, Applied Physics Letters, Vol 58, 2732ペー
ジ, 1991年６月号、参照）．図４に示されるようにLiTa
O3基板１に光導波路２が形成され、さらに光導波路２に
は周期的に分極の反転した層３（分極反転層）が形成さ
れている。基本波Ｐ１と発生する高調波Ｐ２の伝搬定数
の不整合を分極反転層３および非分極反転層４の周期構
造で補償することにより高効率に高調波Ｐ２を出すこと
ができる。光導波路２の入射面１０に基本波Ｐ１を入射
すると、光導波路２から高調波Ｐ２が効率良く発生さ
れ、光波長変換素子として動作する。2. Description of the Related Art FIG. 4 shows a configuration diagram of a conventional optical wavelength conversion element based on an optical waveguide. Hereinafter, generation of harmonics (wavelength 0.42 μm) with respect to a fundamental wave having a wavelength of 0.84 μm will be described in detail with reference to the drawings. (K. Mizuuchi, K. Yamamoto and TT
aniuchi, Applied Physics Letters, Vol 58, p. 2732, June 1991, see). As shown in FIG.
An optical waveguide 2 is formed on an O 3 substrate 1, and a layer 3 (a domain-inverted layer) having periodically inverted polarization is formed in the optical waveguide 2. By compensating for the mismatch between the propagation constant of the fundamental wave P1 and the generated harmonic P2 by the periodic structure of the domain-inverted layer 3 and the non-domain-inverted layer 4, the harmonic P2 can be emitted with high efficiency. When the fundamental wave P1 is incident on the incident surface 10 of the optical waveguide 2, the harmonic wave P2 is efficiently generated from the optical waveguide 2 and operates as an optical wavelength conversion element.
【０００３】このような従来の光波長変換素子はプロト
ン交換法により作製された光導波路２を基本構成要素と
していた。この素子の製造方法について図を用いて説明
する。図５は従来の光波長変換素子の製造工程図であ
る。まず同図（ａ）でLiTaO3基板１に通常のフォトプロ
セスとドライエッチングを用いてＴａ６を周期状にパタ
ーニングする。次に同図（ｂ）でＴａ６パターンが形成
されたLiTaO3基板１に２６０℃、３０分間プロトン交換
を行いＴａ６で覆われていないスリット直下に厚み０．
８μｍのプロトン交換層８を形成する。次にＨＦ：ＨＮ
Ｆ3の１：１混合液にて２分間エッチングしＴａを除去
する。次に同図（ｃ）で５５０℃の温度で１分間熱処理
する。熱処理の上昇レートは５０℃／秒、冷却レートは
１０℃／秒である。これにより分極反転層３が形成され
る。プロトン交換層８はＬｉが減少しておりキュリー温
度が低下するため部分的に分極反転を行うことができ
る。さらに同図（ｄ）で上記分極反転層３中にプロトン
交換を用いて光導波路２を形成する。光導波路用マスク
としてＴａをストライプ状にパターニングを行うことで
Ｔａマスクに幅４μｍ、長さ１２ｍｍのスリットを形成
する。このＴａマスクで覆われた基板に２６０℃、１６
分間プロトン交換を行い０．５μｍの高屈折率層を形成
する。Ｔａマスクを除去した後４２０℃で３０秒間熱処
理を行う。プロトン交換された保護マスクのスリット直
下の領域は屈折率が０．０３程度上昇した光導波路２と
なる。分極反転層３の周期は１０．８μｍであり３次の
擬似位相整合構造となっていた。この従来の方法により
作製される光波長変換素子は波長0.84μｍの基本波Ｐ１
に対して、光導波路２の長さを９ｍｍ、基本波Ｐ１のパ
ワーを２７ｍＷにしたとき高調波Ｐ２のパワー０．１３
ｍＷ、変換効率０．５％が得られていた。[0003] Such a conventional optical wavelength conversion element has an optical waveguide 2 manufactured by a proton exchange method as a basic component. A method for manufacturing this element will be described with reference to the drawings. FIG. 5 is a manufacturing process diagram of a conventional optical wavelength conversion element. First, in FIG. (A) the LiTaO 3 substrate 1 by using the ordinary photo process and dry etching to pattern the Ta6 to periodic. Next, proton exchange is performed at 260 ° C. for 30 minutes on the LiTaO 3 substrate 1 on which the Ta6 pattern is formed in FIG.
An 8 μm proton exchange layer 8 is formed. Next, HF: HN
Etching is performed with a 1: 1 mixed solution of F 3 for 2 minutes to remove Ta. Next, heat treatment is performed at a temperature of 550 ° C. for 1 minute in FIG. The rate of increase in the heat treatment is 50 ° C./sec, and the cooling rate is 10 ° C./sec. Thereby, the domain-inverted layer 3 is formed. In the proton exchange layer 8, since the Li is reduced and the Curie temperature is lowered, the domain inversion can be partially performed. Further, in FIG. 3D, an optical waveguide 2 is formed in the domain-inverted layer 3 by using proton exchange. By patterning Ta in a stripe shape as an optical waveguide mask, a slit having a width of 4 μm and a length of 12 mm is formed in the Ta mask. 260 ° C., 16
The proton exchange is performed for 0.5 minutes to form a 0.5 μm high refractive index layer. After removing the Ta mask, heat treatment is performed at 420 ° C. for 30 seconds. The region immediately below the slit of the proton-exchanged protective mask becomes the optical waveguide 2 whose refractive index has increased by about 0.03. The period of the domain-inverted layer 3 was 10.8 μm, which was a tertiary quasi-phase matching structure. The optical wavelength conversion element manufactured by this conventional method has a fundamental wave P1 having a wavelength of 0.84 μm.
When the length of the optical waveguide 2 is 9 mm and the power of the fundamental wave P1 is 27 mW, the power of the harmonic P2 is 0.13.
mW and a conversion efficiency of 0.5% were obtained.
【０００４】また、１次の擬似位相整合構造の場合周期
は３．６μｍと小さく、そのため分極反転層の厚みは
１．５μｍとなる。この場合基本波Ｐ１が２７ｍＷで
０．３ｍＷの高調波Ｐ２が得られていた。変換効率は１
％であった。In the case of the first-order quasi-phase matching structure, the period is as small as 3.6 μm, so that the thickness of the domain-inverted layer is 1.5 μm. In this case, the fundamental wave P1 was 27 mW and a harmonic P2 of 0.3 mW was obtained. Conversion efficiency is 1
%Met.
【０００５】[0005]
【発明が解決しようとする課題】上記のような光導波路
を基本とした光波長変換素子では高効率変換が可能な１
次の擬似位相整合の場合、分極反転層の厚みが光導波路
に比べて小さく、そのため光導波路を伝搬する光と分極
反転層のオーバーラップも小さくなっていた。この従来
の作製方法では分極反転層は半円形状となるため分極反
転層幅と厚みが比例しこれ以上深くすることができなか
った。そのため変換効率が理論にたいして１／４程度に
低下してしまうといった問題があった。An optical wavelength conversion element based on an optical waveguide as described above is capable of high-efficiency conversion.
In the case of the following quasi-phase matching, the thickness of the domain-inverted layer is smaller than that of the optical waveguide, and therefore, the overlap between light propagating through the optical waveguide and the domain-inverted layer is also small. In this conventional manufacturing method, since the domain-inverted layer has a semicircular shape, the width and the thickness of the domain-inverted layer are proportional and cannot be further increased. Therefore, there is a problem that the conversion efficiency is reduced to about 1/4 of the theory.
【０００６】[0006]
【課題を解決するための手段】本発明は、上記課題を解
決するため光波長変換素子およびその製造方法に新たな
工夫を加えることにより、高効率変換可能な光波長変換
素子およびその製造方法を提供するものである。非線形
光学結晶と、前記結晶に周期的に形成された周期的分極
反転層と、前記結晶深部に形成されたスラブ状の分極反
転層とを備え、前記周期的分極反転層の底部と、前記ス
ラブ状分極反転層の上部とがつながって構成されてい
る、光波長変換素子とする。 非線形光学結晶表面には光
導波路が形成され、前記光導波路よりも分極反転層の方
が深くなっているのが好ましい。 また、非線形光学結晶
と、前記結晶に周期的に形成された再反転層とを備え、
前記再反転層が形成されることにより、分極反転層が周
期的に形成されている、光波長変換素子とする。 また、
非線形光学結晶内部にスラブ状に分極反転層を形成する
工程と、前記結晶表面に周期状に分極反転層を形成する
とともに、前記周期的分極反転層の底部と前記スラブ状
分極反転層の上部とがつながるよう形成する工程とを有
する、光波長変換素子の製造方法とする。 非線形光学結
晶表面に光導波路を形成し、前記光導波路よりも分極反
転層の方が深くなっているのが好ましい。 また、非線形
光学結晶表面にスラブ状の分極反転層を形成する工程
と、前記スラブ状の分極反転層に、周期状の高屈折率層
を形成する工程と、前記高屈折率層を熱処理し、前記ス
ラブ状分極反転層に周期状の再反転層を形成する工程と
を有する、光波長変換素子の製造方法とする。 SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a light wavelength conversion device and a method for manufacturing the same, which provide a light wavelength conversion device capable of high efficiency conversion.
An element and a method for manufacturing the same are provided. non-linear
Optical crystal and periodic polarization periodically formed in said crystal
An inversion layer, and a slab-like polarization counterpart formed in the deep part of the crystal.
And a bottom portion of the periodic domain-inverted layer;
The lab-like domain-inverted layer is connected to the top
A light wavelength conversion element. Light on the nonlinear optical crystal surface
A waveguide is formed, and the domain-inverted layer is formed more than the optical waveguide.
Is preferably deeper. In addition, nonlinear optical crystals
And a reinversion layer periodically formed in the crystal,
Due to the formation of the re-inversion layer, the polarization inversion layer
The light wavelength conversion element is formed periodically. Also,
Formation of domain-inverted layer in slab shape inside nonlinear optical crystal
Forming a domain-inverted layer periodically on the crystal surface
And the bottom of the periodic domain-inverted layer and the slab shape.
Forming a connection with the upper part of the domain-inverted layer.
A method for manufacturing an optical wavelength conversion element. Nonlinear optical connection
An optical waveguide is formed on the crystal surface, and the polarization reversal is higher than that of the optical waveguide.
Preferably, the translocation layer is deeper. Also, nonlinear
Step of forming slab-shaped domain-inverted layer on optical crystal surface
And a periodic high refractive index layer on the slab-shaped domain-inverted layer.
Forming a high-refractive-index layer,
Forming a periodic re-inversion layer in the lab-like domain-inverted layer;
And a method for manufacturing a light wavelength conversion element.
【０００７】[0007]
【作用】本発明の光波長変換素子およびその製造方法に
よれば、非線形光学結晶、例えばＬｉＮｂxＴａ1-xＯ3
（０≦ｘ≦１）内部に形成されたスラブ状の分極反転層
を利用することで、分極反転層の形状を縦長にし、結晶
中に深い周期状の分極反転層を形成することができる。
これにより、光導波路とのオーバーラップが増し、変換
効率が大幅に向上する。According to the optical wavelength conversion element and the method of manufacturing the same of the present invention, a nonlinear optical crystal, for example, LiNbxTa1-xO3
(0 ≦ x ≦ 1) By using the slab-shaped domain-inverted layer formed inside, the domain-inverted layer can be elongated vertically, and a deep periodic domain-inverted layer can be formed in the crystal.
Thereby, the overlap with the optical waveguide is increased, and the conversion efficiency is greatly improved.
【０００８】[0008]
【実施例】第１の実施例として本発明の光波長変換素子
の製造方法について図を使って説明する。図１はその製
造工程図である。同図（ａ）でまずLiTaO3基板１にピロ
燐酸中でのプロトン交換により厚み２．５μｍのプロト
ン交換層５を形成する。次に同図（ｂ）で赤外線加熱装
置を用いて５５０℃、１５秒間熱処理を行いLiTaO3基板
１の内部にスラブ状の分極反転層７を形成する。プロト
ン交換層５はＬｉが減少しておりキュリー温度が低下す
るため部分的に分極反転ができる。また、分極反転層は
プロトン交換層と基板の境界１ａから発生しまわりに広
がる。そのため、この分極反転層７は表面から２．２μ
ｍのところから２．８μｍまでの深さまで形成された。
次に同図（ｃ）で通常のフォトプロセスとドライエッチ
ングを用いてＴａ６を周期状にパターニングした後、Ｔ
ａ６によるパターンが形成されたLiTaO3基板１に２６０
℃、３０分間プロトン交換を行いスリット直下に厚み
０．８μｍのプロトン交換層８を形成する。その後Ｈ
Ｆ：ＨＮＦ3の１：１混合液にて２分間エッチングしＴ
ａを除去する。次に同図（ｄ）で赤外線加熱装置を用い
て５５０℃の温度で１分間熱処理する。熱処理の上昇レ
ートは５０℃／秒、冷却レートは１０℃／秒である。こ
れにより分極反転層３が形成される。これは分極反転層
３が近傍の分極反転層７と結合しようとする作用によ
る。この分極反転層３はスラブ状の分極反転層７と接続
された形となる。そのため分極反転層３の深さは２．２
μｍとなる。次に上記分極反転層３に対してプロトン交
換を用いて光導波路２を形成する。同図（ｅ）で光導波
路用マスクとしてＴａをストライプ状にパターニングを
行った後、Ｔａマスクに幅４μｍ、長さ１２ｍｍのスリ
ットが形成されたものに２６０℃、１６分間ピロ燐酸中
でプロトン交換を行った後、赤外線加熱装置を用いて４
２０℃で３０秒熱処理を行った。これにより屈折率が
０．０３程度上昇した光導波路２が形成される。最後に
Ｔａを除去した後、蒸着によりSiO2を３０００Ａ付加し
た。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a first embodiment, a method for manufacturing an optical wavelength conversion device of the present invention will be described with reference to the drawings. FIG. 1 is a manufacturing process diagram. In FIG. 1A, a proton exchange layer 5 having a thickness of 2.5 μm is formed on a LiTaO 3 substrate 1 by proton exchange in pyrophosphoric acid. Next, in FIG. 3B, heat treatment is performed at 550 ° C. for 15 seconds using an infrared heating device to form a slab-shaped domain-inverted layer 7 inside the LiTaO 3 substrate 1. In the proton exchange layer 5, since Li is reduced and the Curie temperature is lowered, polarization inversion can be partially performed. The domain-inverted layer is generated from the boundary 1a between the proton exchange layer and the substrate and spreads around. Therefore, the domain-inverted layer 7 is 2.2 μm from the surface.
m to a depth of up to 2.8 μm.
Next, as shown in FIG. 3C, Ta6 is patterned in a periodic manner using a normal photo process and dry etching.
260 is applied to the LiTaO 3 substrate 1 on which the pattern by a6 is formed.
Proton exchange is performed at 30 ° C. for 30 minutes to form a proton exchange layer 8 having a thickness of 0.8 μm immediately below the slit. Then H
Etch with a 1: 1 mixture of F: HNF 3 for 2 minutes
a is removed. Next, a heat treatment is performed at 550 ° C. for 1 minute using an infrared heating device in FIG. The rate of increase in the heat treatment is 50 ° C./sec, and the cooling rate is 10 ° C./sec. Thereby, the domain-inverted layer 3 is formed. This is due to the effect that the domain-inverted layer 3 tries to combine with the domain-inverted layer 7 in the vicinity. The domain-inverted layer 3 is connected to the slab-shaped domain-inverted layer 7. Therefore, the depth of the domain-inverted layer 3 is 2.2.
μm. Next, the optical waveguide 2 is formed on the domain-inverted layer 3 by using proton exchange. In FIG. 3E, after Ta is patterned into a stripe shape as an optical waveguide mask, proton exchange in pyrophosphoric acid at 260 ° C. for 16 minutes is performed on a Ta mask having a slit having a width of 4 μm and a length of 12 mm. After performing the above, 4
Heat treatment was performed at 20 ° C. for 30 seconds. Thus, the optical waveguide 2 whose refractive index has increased by about 0.03 is formed. Finally, after removing Ta, 3000 A of SiO 2 was added by vapor deposition.
【０００９】上記のような工程により分極反転層３およ
び光導波路２が製造された。この分極反転層３の厚み
２．２μｍは光導波路２の厚みｄは１．８μｍに比べ大
きく完全にオーバーラップされておりこのため有効に波
長変換が行われる。分極反転層３の周期は３．６μｍで
あり波長０．８４ｎｍに対して動作する。また、この光
導波路２の非分極反転層４と分極反転層３の屈折率変化
はなく、光が導波する場合の伝搬損失は小さい。光導波
路２に垂直な面を光学研磨し入射部および出射部を形成
した。このようにして光波長変換素子が製造できる。[0009] The domain-inverted layer 3 and the optical waveguide 2 were manufactured by the steps described above. The thickness 2.2 μm of the domain-inverted layer 3 completely overlaps the thickness d of the optical waveguide 2 which is larger than 1.8 μm, so that the wavelength conversion is effectively performed. The period of the domain-inverted layer 3 is 3.6 μm, and operates at a wavelength of 0.84 nm. Further, there is no change in the refractive index between the non-polarization inversion layer 4 and the polarization inversion layer 3 of the optical waveguide 2, and the propagation loss when light is guided is small. A plane perpendicular to the optical waveguide 2 was optically polished to form an incident part and an outgoing part. Thus, an optical wavelength conversion element can be manufactured.
【００１０】また、この素子の長さは９ｍｍである。基
本波Ｐ１として半導体レーザ光（波長０．８４μｍ）を
入射部より導波させたところシングルモード伝搬し、波
長０．４２μｍの高調波Ｐ２が出射部より基板外部に取
り出された。光導波路２の伝搬損失は1dB/cmと小さく高
調波Ｐ２が有効に取り出された。低損失化の原因の１つ
として燐酸により均一な光導波路が形成されたことがあ
る。基本波２７ｍＷの入力で１．２ｍＷの高調波（波長
０．４２μｍ）を得た。この場合の変換効率は４．５％
であり従来のものにくらべて４倍の高効率化が図られて
いる。図２に分極反転層幅と分極反転層厚みの関係を示
す。本発明の光波長変換素子の製造方法によれば従来の
方法にくらべ１次の擬次位相整合周期に必要な幅１．８
μｍのところで分極反転層の厚みが１．４倍も深くなっ
ている。[0010] The length of this element is 9 mm. When a semiconductor laser beam (wavelength: 0.84 μm) was guided from the incident portion as the fundamental wave P1, single-mode propagation occurred, and a harmonic P2 having a wavelength of 0.42 μm was extracted from the emission portion to the outside of the substrate. The propagation loss of the optical waveguide 2 was as small as 1 dB / cm, and the harmonic P2 was effectively extracted. One of the causes of the low loss is that a uniform optical waveguide is formed by phosphoric acid. A harmonic of 1.2 mW (wavelength 0.42 μm) was obtained by inputting a fundamental wave of 27 mW. The conversion efficiency in this case is 4.5%
The efficiency is four times higher than that of the conventional one. FIG. 2 shows the relationship between the domain-inverted layer width and the domain-inverted layer thickness. According to the method of manufacturing an optical wavelength conversion element of the present invention, the width required for the first-order pseudo-order phase matching period is 1.8 compared to the conventional method.
At μm, the thickness of the domain-inverted layer is 1.4 times deeper.
【００１１】なおこのような短時間処理を行うには急速
加熱が可能な赤外線加熱装置が適している。An infrared heating device capable of rapid heating is suitable for performing such a short-time treatment.
【００１２】次に本発明の光波長変換素子の製造方法を
用いた第２の実施例について説明する。図３はその製造
工程図である。同図（ａ）でまずLiTaO3基板１にピロ燐
酸中でのプロトン交換により厚み１μｍのプロトン交換
層５を形成する。次に同図（ｂ）で５５０℃、２分熱処
理を行いLiTaO3基板１の表面にスラブ状の分極反転層７
を形成する。プロトン交換層はＬｉが減少しておりキュ
リー温度が低下するため部分的に分極反転ができる。こ
の分極反転層７は表面から厚み２．２μｍのところまで
形成された。次に同図（ｃ）で通常のフォトプロセスと
ドライエッチングを用いてＴａ６を周期状にパターニン
グする。次にＴａ６によるパターンが形成されたLiTaO3
基板１に２６０℃、２０分間プロトン交換を行いスリッ
ト直下に厚み０．５μｍのプロトン交換層８を形成す
る。次にＨＦ：ＨＮＦ3の１：１混合液にて２分間エッ
チングしＴａ６を除去する。次に同図（ｄ）で赤外線加
熱装置により５５０℃の温度で１分間熱処理する。熱処
理の上昇レートは５０℃／秒、冷却レートは１０℃／秒
である。これにより分極反転層７中に再反転層９が形成
される。この再反転層９は分極反転層７を越え反転され
てない領域に達したところで停止する。次に上記再反転
層９の残りの部分である分極反転層３に対してプロトン
交換を用いて光導波路２を形成する。同図（ｅ）で光導
波路用マスクとしてＴａをストライプ状にパターニング
を行った後、Ｔａマスクに幅４μｍ、長さ１２ｍｍのス
リットが形成されたものに２６０℃、１６分間ピロ燐酸
中でプロトン交換を行った後、Ｔａマスクを除去する。
次に、赤外線加熱装置を用いて４２０℃で３０秒熱処理
を行い屈折率が０．０３程度上昇した光導波路２が形成
される。最後に蒸着によりSiO2を３０００Ａ付加した。Next, a description will be given of a second embodiment using the method for manufacturing an optical wavelength conversion element according to the present invention. FIG. 3 is a manufacturing process diagram. 1A, a proton exchange layer 5 having a thickness of 1 μm is formed on a LiTaO 3 substrate 1 by proton exchange in pyrophosphoric acid. Next, a heat treatment is performed at 550 ° C. for 2 minutes in the same figure (b) to form a slab-shaped domain-inverted layer 7 on the surface of the LiTaO 3 substrate 1.
To form In the proton exchange layer, since Li is reduced and the Curie temperature is lowered, polarization inversion can be partially performed. This domain-inverted layer 7 was formed to a thickness of 2.2 μm from the surface. Next, in FIG. 3C, Ta6 is patterned in a periodic manner using a normal photo process and dry etching. Next, LiTaO 3 on which a pattern of Ta6 is formed
Proton exchange is performed on the substrate 1 at 260 ° C. for 20 minutes to form a proton exchange layer 8 having a thickness of 0.5 μm immediately below the slit. Next HF: HNF 3 of 1: removing 2 minutes etching Ta6 at 1 mixture. Next, in FIG. 3D, heat treatment is performed for 1 minute at a temperature of 550 ° C. by an infrared heating device. The rate of increase in the heat treatment is 50 ° C./sec, and the cooling rate is 10 ° C./sec. Thereby, the re-inversion layer 9 is formed in the domain-inverted layer 7. This re-inversion layer 9 stops when it reaches a region where it has not been inverted beyond the domain-inverted layer 7. Next, the optical waveguide 2 is formed on the domain-inverted layer 3 as the remaining portion of the re-inverted layer 9 by using proton exchange. In FIG. 3E, after Ta is patterned into a stripe shape as an optical waveguide mask, proton exchange in pyrophosphoric acid at 260 ° C. for 16 minutes is performed on a Ta mask having a slit having a width of 4 μm and a length of 12 mm. Is performed, the Ta mask is removed.
Next, heat treatment is performed at 420 ° C. for 30 seconds using an infrared heating device to form the optical waveguide 2 whose refractive index is increased by about 0.03. Finally, 3000 A of SiO 2 was added by vapor deposition.
【００１３】上記のような工程により分極反転層３およ
び光導波路２が製造された。この光導波路２の厚みｄは
１．８μｍであり分極反転層３の厚み２．２μｍに比べ
小さく有効に波長変換される。分極反転層３の周期は
３．６μｍであり波長０．８４ｎｍに対して動作する。
また、この光導波路２の非分極反転層４と分極反転層３
の屈折率変化はなく、光が導波する場合の伝搬損失は小
さい。光導波路２に垂直な面を光学研磨し入射部および
出射部を形成した。このようにして光波長変換素子が製
造できる。また、この素子の長さは９ｍｍである。基本
波Ｐ１として半導体レーザ光（波長０．８４μｍ）を入
射部より導波させたところ、波長０．４２μｍの高調波
Ｐ２が出射部より基板外部に取り出された。基本波８０
ｍＷの入力で１０ｍＷの高調波（波長０．４２μｍ）を
得た。この場合の変換効率は１２％る。光損傷はなく高
調波出力は非常に安定していた。The domain-inverted layer 3 and the optical waveguide 2 were manufactured by the steps described above. The thickness d of the optical waveguide 2 is 1.8 μm, which is smaller than the thickness of the domain-inverted layer 3 of 2.2 μm, and the wavelength is effectively converted. The period of the domain-inverted layer 3 is 3.6 μm, and operates at a wavelength of 0.84 nm.
Further, the non-polarization inversion layer 4 and the polarization inversion layer 3 of the optical waveguide 2
Does not change, and the propagation loss when light is guided is small. A plane perpendicular to the optical waveguide 2 was optically polished to form an incident part and an outgoing part. Thus, an optical wavelength conversion element can be manufactured. The length of this element is 9 mm. When a semiconductor laser beam (wavelength: 0.84 μm) was guided from the incident portion as the fundamental wave P1, a harmonic P2 having a wavelength of 0.42 μm was extracted outside the substrate from the emission portion. Fundamental wave 80
With the input of mW, a harmonic of 10 mW (wavelength 0.42 μm) was obtained. The conversion efficiency in this case is 12%. There was no light damage and the harmonic output was very stable.
【００１４】なお実施例では非線形光学結晶としてLiTa
O3を用いたがLiNbO3、KNbO3、ＫＴＰ等の強誘電体にも
適用可能である。In the embodiment, LiTa is used as the nonlinear optical crystal.
Although O 3 is used, the present invention is applicable to ferroelectrics such as LiNbO 3 , KNbO 3 , and KTP.
【００１５】[0015]
【発明の効果】以上説明したように、本発明の光波長変
換素子およびその製造方法によれば、スラブ状の分極反
転層を作製しこのスラブ状の分極反転層に対して後から
形成される周期状の分極反転層の結合を利用すること
で、従来の方法に比べて深い分極反転層を形成すること
ができ、光波長変換素子の変換効率を大幅に向上させる
ことができる。As described above, the optical wavelength conversion of the present invention is performed.
According to the switching element and the method for manufacturing the same, a conventional slab-shaped domain-inverted layer is formed, and the slab-shaped domain-inverted layer is combined with a periodically-formed domain-inverted layer to form a conventional domain-inverted layer. A deeper domain inversion layer can be formed as compared with the method, and the conversion efficiency of the optical wavelength conversion element can be greatly improved.
【図１】本発明の第１の実施例の光波長変換素子の製造
方法の工程断面図FIG. 1 is a process sectional view of a method for manufacturing an optical wavelength conversion element according to a first embodiment of the present invention.
【図２】分極反転層幅と分極反転層厚みとの関係を示す
図FIG. 2 is a diagram illustrating a relationship between a domain-inverted layer width and a domain-inverted layer thickness.
【図３】本発明の第２の実施例の光波長変換素子の製造
方法の工程断面図FIG. 3 is a process sectional view of a method for manufacturing an optical wavelength conversion element according to a second embodiment of the present invention.
【図４】従来の光波長変換素子の構成図FIG. 4 is a configuration diagram of a conventional optical wavelength conversion element.
【図５】従来の方法による光波長変換素子の製造方法の
工程断面図FIG. 5 is a process sectional view of a method for manufacturing an optical wavelength conversion element by a conventional method.
１ ＬｉＴａＯ3基板 ２ 光導波路 ３ 分極反転層 ５ 高屈折率層 ７ スラブ状の分極反転層 Ｐ１ 基本波 Ｐ２ 高調波REFERENCE SIGNS LIST 1 LiTaO 3 substrate 2 optical waveguide 3 domain-inverted layer 5 high refractive index layer 7 slab-shaped domain-inverted layer P1 fundamental wave P2 harmonic
フロントページの続き (56)参考文献 特開 平３−191332（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) G02F 1/37 Continuation of the front page (56) References JP-A-3-191332 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) G02F 1/37
Claims (6)
形成された周期的分極反転層と、前記結晶深部に形成さ
れたスラブ状の分極反転層とを備え、前記周期的分極反
転層の底部と、前記スラブ状分極反転層の上部とがつな
がって構成されている、光波長変換素子。1. A non-linear optical crystal, comprising: a periodically poled layer periodically formed in the crystal; and a slab-shaped poled layer formed in a deep part of the crystal. An optical wavelength conversion element, wherein a bottom portion and an upper portion of the slab-shaped domain-inverted layer are connected to each other.
され、前記光導波路よりも分極反転層の方が深くなって
いる、請求項１に記載の光波長変換素子。2. The optical wavelength conversion device according to claim 1, wherein an optical waveguide is formed on the surface of the nonlinear optical crystal, and the domain-inverted layer is deeper than the optical waveguide.
（０≦ｘ≦１）である、請求項１または２に記載の光波
長変換素子。3. The non-linear optical crystal is LiNbxTa1-xO3.
The optical wavelength conversion device according to claim 1, wherein (0 ≦ x ≦ 1).
転層を形成する工程と、前記結晶表面に周期状に分極反
転層を形成するとともに、前記周期的分極反転層の底部
と前記スラブ状分極反転層の上部とがつながるよう形成
する工程とを有する、光波長変換素子の製造方法。4. A step of forming a domain-inverted layer in a slab shape inside a nonlinear optical crystal, forming a domain-inverted layer periodically on the crystal surface, and forming a bottom of the periodic domain-inverted layer and the slab-shaped polarization. Forming the optical wavelength conversion element so as to be connected to the upper part of the inversion layer.
し、前記光導波路よりも分極反転層の方が深くなってい
る、請求項４に記載の光波長変換素子の製造方法。5. The method according to claim 4 , wherein an optical waveguide is formed on the surface of the nonlinear optical crystal, and the domain-inverted layer is deeper than the optical waveguide.
転層を形成する工程と、前記スラブ状の分極反転層に、
周期状の高屈折率層を形成する工程と、前記高屈折率層
を熱処理し、前記スラブ状分極反転層に周期状の再反転
層を形成する工程とを有する、光波長変換素子の製造方
法。6. A step of forming a slab-shaped domain-inverted layer on the surface of a nonlinear optical crystal,
Forming a periodic high-refractive-index layer; and heat-treating the high-refractive-index layer to form a periodic re-inversion layer on the slab-shaped domain-inverted layer. .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3255161A JP3006217B2 (en) | 1991-10-02 | 1991-10-02 | Optical wavelength conversion element and method of manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3255161A JP3006217B2 (en) | 1991-10-02 | 1991-10-02 | Optical wavelength conversion element and method of manufacturing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05107579A JPH05107579A (en) | 1993-04-30 |
| JP3006217B2 true JP3006217B2 (en) | 2000-02-07 |
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ID=17274913
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3255161A Expired - Fee Related JP3006217B2 (en) | 1991-10-02 | 1991-10-02 | Optical wavelength conversion element and method of manufacturing the same |
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| Country | Link |
|---|---|
| JP (1) | JP3006217B2 (en) |
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1991
- 1991-10-02 JP JP3255161A patent/JP3006217B2/en not_active Expired - Fee Related
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|---|---|
| JPH05107579A (en) | 1993-04-30 |
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