JPH0667237A - Second harmonic wave generating element and its production - Google Patents
Second harmonic wave generating element and its productionInfo
- Publication number
- JPH0667237A JPH0667237A JP2137992A JP2137992A JPH0667237A JP H0667237 A JPH0667237 A JP H0667237A JP 2137992 A JP2137992 A JP 2137992A JP 2137992 A JP2137992 A JP 2137992A JP H0667237 A JPH0667237 A JP H0667237A
- Authority
- JP
- Japan
- Prior art keywords
- substrate
- periodic
- polarization
- polarization inversion
- linbo
- 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
- 238000004519 manufacturing process Methods 0.000 title claims description 10
- 230000010287 polarization Effects 0.000 claims abstract description 40
- 239000000758 substrate Substances 0.000 claims abstract description 37
- 230000000737 periodic effect Effects 0.000 claims abstract description 26
- 230000003287 optical effect Effects 0.000 claims abstract description 10
- 239000007769 metal material Substances 0.000 claims abstract description 5
- 230000001590 oxidative effect Effects 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 26
- 229910013641 LiNbO 3 Inorganic materials 0.000 claims description 17
- 230000003647 oxidation Effects 0.000 abstract description 12
- 238000007254 oxidation reaction Methods 0.000 abstract description 12
- 238000009792 diffusion process Methods 0.000 abstract description 9
- 239000000126 substance Substances 0.000 abstract description 4
- 239000000463 material Substances 0.000 abstract description 3
- 239000013078 crystal Substances 0.000 abstract description 2
- 238000005342 ion exchange Methods 0.000 abstract description 2
- 229910003327 LiNbO3 Inorganic materials 0.000 abstract 3
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 9
- 239000002184 metal Substances 0.000 description 7
- 229910004298 SiO 2 Inorganic materials 0.000 description 5
- 238000002513 implantation Methods 0.000 description 5
- 238000011068 loading method Methods 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 230000005684 electric field Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は短波長光の発生に利用す
る。特に、入射基本波光に対して二次高調波光を発生す
る二次高調波発生素子に関する。さらに詳しくは、基本
波光と二次高調波光との位相を疑似的に整合させるた
め、光導波路に沿って周期的に分極を反転させる方法に
関する。BACKGROUND OF THE INVENTION The present invention is used to generate short wavelength light. In particular, the present invention relates to a second harmonic generation element that generates second harmonic light with respect to incident fundamental wave light. More specifically, the present invention relates to a method of periodically inverting the polarization along the optical waveguide in order to make the phases of the fundamental wave light and the second harmonic light pseudo match.
【０００２】[0002]
【従来の技術】ＬｉＮｂＯ3 などの強誘電体は、二次の
非線形光学特性をもつことから、二次高調波発生素子と
して利用されている。このような素子では、効率よく二
次高調波を発生させるため、基本波の位相と二次高調波
の位相とを少なくとも疑似的に整合させる必要がある。2. Description of the Related Art Ferroelectric materials such as LiNbO 3 are used as a second harmonic generation element because they have second-order nonlinear optical characteristics. In such an element, in order to efficiently generate the second harmonic, it is necessary to at least pseudo-match the phase of the fundamental wave with the phase of the second harmonic.
【０００３】二つの波の位相を疑似的に整合させる構造
のひとつとして、光導波路に沿って分極を周期的に反転
させたものが知られている。分極を反転させる方法とし
ては、ＬｉＮｂＯ3 の場合、Ｔｉ拡散法、ＳｉＯ2 装荷
法、電子打ち込み法などが知られている。また、ＬｉＴ
ａＯ3 の分極を反転させる方法としては、プロトン交換
法が知られている。ＳｉＯ2 装荷法、電子打ち込み法お
よびプロトン交換法は比較的新しい方法であり、それぞ
れ、１９９１年第３８回応物春季予稿集２８ａ−ＳＦ−
１４、同２９ｐ−ＰＢ−８、同２８ａ−ＳＦ−１３に詳
しく説明されている。As one of the structures for pseudo-matching the phases of two waves, a structure in which polarization is periodically inverted along an optical waveguide is known. As a method of reversing the polarization, in the case of LiNbO 3 , a Ti diffusion method, a SiO 2 loading method, an electron implantation method and the like are known. Also, LiT
A proton exchange method is known as a method for reversing the polarization of aO 3 . The SiO 2 loading method, the electron implantation method, and the proton exchange method are relatively new methods, and the 38th Bibliographical Spring Proceedings of 1991, 28a-SF-, respectively.
14, 29p-PB-8 and 28a-SF-13.
【０００４】[0004]
【発明が解決しようとする課題】しかし、Ｔｉ拡散法
は、ＬｉＮｂＯ3 中にＴｉを拡散させるので、その部分
に屈折率差が生じ、二次高調波発生のための分極反転位
相整合には適していない。ＳｉＯ2 装荷法は、１０００
℃以上の高温処理を行うため、ＬｉＮｂＯ3 からＬｉイ
オンが脱離してＳｉＯ2 に拡散するアウトディフュージ
ョンの問題がある。電子打ち込み法は、反転部の境界が
ぼける傾向があり、また、装置が大がかりとなって量産
には向いていない。However, since the Ti diffusion method diffuses Ti in LiNbO 3 , a difference in refractive index is generated in that portion, and it is suitable for polarization inversion phase matching for generating a second harmonic. Not not. The SiO 2 loading method is 1000
Since the high temperature treatment of ℃ or more is performed, there is a problem of out diffusion in which Li ions are desorbed from LiNbO 3 and diffused into SiO 2 . The electron implantation method has a tendency that the boundary of the inversion portion is blurred, and the device is large in size, and is not suitable for mass production.
【０００５】また、プロトン交換法は、Ｌｉイオンをプ
ロトンに置換するため、Ｔｉ拡散の場合と同様に屈折率
差が生じ、しかも反転形状が最適なものとはいえない。Further, in the proton exchange method, since Li ions are replaced by protons, a difference in refractive index occurs as in the case of Ti diffusion, and the inverted shape cannot be said to be optimal.
【０００６】本発明は、このような課題を解決し、基板
に損傷を与えることなく簡単に分極を反転させることの
できる方法を提供することを目的とする。It is an object of the present invention to solve such problems and provide a method capable of easily reversing the polarization without damaging the substrate.
【０００７】[0007]
【課題を解決するための手段】本発明の第一の観点は二
次高調波発生素子の製造方法であり、強誘電体基板の表
面に接して金属材料による周期格子を設け、この周期格
子を熱酸化することにより分極反転を形成することを特
徴とする。A first aspect of the present invention is a method of manufacturing a second harmonic generation element, which comprises providing a periodic grating made of a metal material in contact with the surface of a ferroelectric substrate, and It is characterized in that polarization inversion is formed by thermal oxidation.
【０００８】周期格子のピッチは、コヒーレンス長また
はその整数倍にする。The pitch of the periodic grating is the coherence length or an integral multiple thereof.
【０００９】強誘電体基板としてはＬｉＮｂＯ3 基板が
よく、そのときには−Ｃ面に周期的な分極反転が形成さ
れる。A LiNbO 3 substrate is preferably used as the ferroelectric substrate, in which case periodic polarization inversion is formed on the −C plane.
【００１０】本発明の第二の観点はこの方法により製造
される素子であり、強誘電体基板に形成された周期的な
分極反転層と、この周期的な分極反転層と交差するよう
に前記強誘電体基板に形成された光導波路とを備えた二
次高調波発生素子において、強誘電体基板はＬｉＮｂＯ
3 基板であり、分極反転層は、このＬｉＮｂＯ3 基板の
−Ｃ面に、その基板の厚さに比べて十分に薄く形成され
たことを特徴とする。A second aspect of the present invention is an element manufactured by this method, wherein the periodic domain-inverted layer formed on the ferroelectric substrate and the periodic domain-inverted layer are crossed with each other. In a second harmonic generation device including an optical waveguide formed on a ferroelectric substrate, the ferroelectric substrate is LiNbO
3 is a substrate, the polarization inversion layer, the -C surface of the LiNbO 3 substrate, and characterized in that it is sufficiently thin compared to the thickness of the substrate.
【００１１】[0011]
【作用】本発明者らの研究によれば、ＬｉＮｂＯ3 基板
上に金属膜を設け、それを熱酸化すると、基板に分極反
転が形成されることが判明した。分極反転が形成される
領域は膜の周囲であった。また、分極反転が生じるのは
−Ｃ面であった。−Ｃ面に分極反転を生じさせる方法と
しては電子打ち込み法が知られているが、電子打ち込み
法では基板の裏面まで分極が反転し、本発明のように表
面近傍だけを反転させることはできない。−Ｃ面に分極
反転を形成する他の方法は現在のところ知られていな
い。According to the research conducted by the present inventors, it was found that when a metal film is provided on a LiNbO 3 substrate and the film is thermally oxidized, polarization inversion is formed on the substrate. The region where the polarization reversal was formed was around the membrane. In addition, polarization inversion occurred on the -C plane. An electron implantation method is known as a method of causing polarization inversion on the −C plane, but in the electron implantation method, the polarization is inverted to the back surface of the substrate, and only the vicinity of the surface cannot be inverted as in the present invention. No other method is currently known for forming a polarization reversal in the -C plane.
【００１２】この分極反転は表面に接した金属が酸化す
るときに生じるものであり、熱酸化の温度も６００℃以
下でよい。基板表面に膜を設けて加熱する点では従来の
ＳｉＯ2 装荷法に似ているが、温度がかなり低く、８０
０℃以上で生じるＬｉのアウトディフュージョンもない
ことから、全く別の現象であることがわかる。This polarization inversion occurs when the metal in contact with the surface is oxidized, and the temperature of thermal oxidation may be 600 ° C. or lower. It is similar to the conventional SiO 2 loading method in that a film is provided on the substrate surface and heated, but the temperature is considerably low and
Since there is no Li out-diffusion that occurs at 0 ° C. or higher, it can be seen that this is a completely different phenomenon.
【００１３】[0013]
【実施例】図１は本発明を実施した製造方法を示す図で
あり、三つの工程における斜視図を示す。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a manufacturing method embodying the present invention, showing perspective views in three steps.
【００１４】（ａ）に示す工程では、誘電体基板１の表
面に接して、金属材料による周期格子２を設ける。この
周期格子２を熱酸化し、生成された酸化物を除去する
と、（ｂ）に示すように、酸化物の周囲に分極反転層３
が形成される。これに、イオン交換またはＴｉ拡散によ
り光導波路４を形成し、二次高調波発生素子を得る。In the step shown in (a), the periodic grating 2 made of a metal material is provided in contact with the surface of the dielectric substrate 1. When the periodic lattice 2 is thermally oxidized to remove the produced oxide, the polarization inversion layer 3 is formed around the oxide as shown in (b).
Is formed. An optical waveguide 4 is formed on this by ion exchange or Ti diffusion to obtain a second harmonic generation element.
【００１５】誘電体基板１としてはＬｉＮｂＯ3 が適し
ている。ＬｉＮｂＯ3 を用いる場合には、その−Ｃ面に
周期格子２を設ける。周期格子２の材料としてはＴｉが
適している。周期格子２のピッチはコヒーレンス長また
はその整数倍とする。LiNbO 3 is suitable for the dielectric substrate 1. When LiNbO 3 is used, the periodic grating 2 is provided on the −C plane. Ti is suitable as a material for the periodic grating 2. The pitch of the periodic grating 2 is the coherence length or an integral multiple thereof.
【００１６】熱酸化の温度は５００〜６００℃で十分で
ある。A temperature of 500 to 600 ° C. is sufficient for the thermal oxidation.
【００１７】図２は金属の膜厚および酸化温度と分極反
転との関係の一例を示す図である。この例は、ＬｉＮｂ
Ｏ3 基板の−Ｃ面にＴｉ膜を設け、そのＴｉ膜を熱酸化
させたときの条件を示す。酸化時間は、酸化温度が４２
０℃の場合には４時間、それより高温度の場合には２時
間とした。分極反転はＴｉ膜の側部のＬｉＮｂＯ3 に生
じた。Ｔｉ膜が薄い場合には、分極反転が形成されない
（図には×印で示す）か、または薄いもの（図には△印
で示す）しか形成されなかった。また、Ｔｉ膜が厚すぎ
る場合には、この範囲の酸化時間では完全に酸化させる
ことができず、分極反転は形成されなかった。しかし、
Ｔｉ膜の厚さがある程度以上あり、しかもＴｉ膜が完全
に酸化されたときには、十分な分極反転が形成された。FIG. 2 is a diagram showing an example of the relationship between the film thickness and oxidation temperature of the metal and the polarization reversal. In this example, LiNb
O 3 and Ti film is provided -C surface of the substrate, showing the condition when the Ti film was thermally oxidized. The oxidation time is 42
When it was 0 ° C., it was 4 hours, and when it was higher, it was 2 hours. The polarization reversal occurred in LiNbO 3 on the side of the Ti film. When the Ti film was thin, no polarization reversal was formed (indicated by X in the figure) or only thin (indicated by Δ in the figure) was formed. Further, when the Ti film was too thick, it could not be completely oxidized within this range of oxidation time, and polarization inversion was not formed. But,
When the Ti film had a certain thickness or more and the Ti film was completely oxidized, sufficient polarization reversal was formed.
【００１８】図３は分極反転が形成されたＬｉＮｂＯ3
の断面写真であり、図４はそれを説明する図である。図
３の写真は、Ｔｉ膜の厚さ１５０ｎｍ、酸化温度５８０
℃、酸化時間２時間の条件で分極反転を形成し、−Ｙ面
をエッチングした状態のものである。分極反転層の厚さ
ｄは２〜３μｍ、ピッチΛは約２０μｍである。FIG. 3 shows that LiNbO 3 with polarization inversion formed.
4 is a cross-sectional photograph of FIG. 4, and FIG. 4 is a diagram for explaining it. The photograph in FIG. 3 shows a Ti film having a thickness of 150 nm and an oxidation temperature of 580.
The polarization inversion was formed under the conditions of the temperature of 2 ° C. and the oxidation time of 2 hours, and the −Y plane was etched. The domain inversion layer has a thickness d of 2 to 3 μm and a pitch Λ of about 20 μm.
【００１９】[0019]
【発明の効果】以上説明したように、本発明の二次高調
波発生素子の製造方法は、金属を熱酸化することにより
それに接する強誘電体の分極を反転させることができ
る。熱酸化の温度は従来からの分極反転方法に比較して
低く、温度による結晶の損傷は少なく、Ｌｉのアウトデ
ィフュージョンも生じない。また、分極反転のために外
部電界を印加する必要もない。さらに、屈折率の変化も
なく、すぐれた二次高調波発生特性を得ることができ
る。As described above, according to the method of manufacturing the second harmonic generating element of the present invention, the polarization of the ferroelectric substance in contact with the metal can be inverted by thermally oxidizing the metal. The temperature of the thermal oxidation is lower than that of the conventional polarization inversion method, the crystal is less damaged by the temperature, and the Li out diffusion does not occur. Further, it is not necessary to apply an external electric field for reversing the polarization. Further, it is possible to obtain excellent second harmonic generation characteristics without changing the refractive index.
【図１】本発明を実施した製造方法を示す図。FIG. 1 is a diagram showing a manufacturing method embodying the present invention.
【図２】金属の膜厚および酸化温度と分極反転との関係
の一例を示す図。FIG. 2 is a diagram showing an example of a relationship between a metal film thickness and an oxidation temperature and polarization reversal.
【図３】分極反転が形成されたＬｉＮｂＯ3 の断面写
真。FIG. 3 is a cross-sectional photograph of LiNbO 3 in which polarization inversion is formed.
【図４】図３の構造を説明する図。FIG. 4 is a diagram illustrating the structure of FIG.
１ 誘電体基板 ２ 周期格子 ３ 分極反転層 ４ 光導波路 1 Dielectric Substrate 2 Periodic Lattice 3 Polarization Inversion Layer 4 Optical Waveguide
─────────────────────────────────────────────────────
─────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成４年２月１０日[Submission date] February 10, 1992
【手続補正１】[Procedure Amendment 1]
【補正対象書類名】図面[Document name to be corrected] Drawing
【補正対象項目名】図３[Name of item to be corrected] Figure 3
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【図３】 ─────────────────────────────────────────────────────
[Figure 3] ─────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成４年１２月１１日[Submission date] December 11, 1992
【手続補正１】[Procedure Amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】図面の簡単な説明[Name of item to be corrected] Brief description of the drawing
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【図面の簡単な説明】[Brief description of drawings]
【図１】本発明を実施した製造方法を示す図。FIG. 1 is a diagram showing a manufacturing method embodying the present invention.
【図２】金属の膜厚および酸化温度と分極反転との関係
の一例を示す図。FIG. 2 is a diagram showing an example of a relationship between a metal film thickness and an oxidation temperature and polarization reversal.
【図３】ＬｉＮｂＯ３基板上に形成された微細な分極反
転のパターンを表す断面写真。FIG. 3 is a cross-sectional photograph showing a fine domain-inverted pattern formed on a LiNbO 3 substrate.
【図４】図３の構造を説明する図。FIG. 4 is a diagram illustrating the structure of FIG.
【符号の説明】 １ 誘電体基板 ２ 周期格子 ３ 分極反転層 ４ 光導波路[Explanation of Codes] 1 Dielectric Substrate 2 Periodic Lattice 3 Polarization Inversion Layer 4 Optical Waveguide
Claims (3)
し、 この周期的な分極反転と交差するように前記強誘電体基
板に光導波路を形成する二次高調波発生素子の製造方法
において、 前記強誘電体基板の表面に接して金属材料による周期格
子を設け、この周期格子を熱酸化することにより前記分
極反転を形成することを特徴とする二次高調波発生素子
の製造方法。1. A method for manufacturing a second harmonic generation element, wherein a periodic polarization inversion is formed on a ferroelectric substrate, and an optical waveguide is formed on the ferroelectric substrate so as to intersect with the periodic polarization inversion. 2. A method for manufacturing a second harmonic generation element, wherein a periodic grating made of a metal material is provided in contact with the surface of the ferroelectric substrate, and the polarization inversion is formed by thermally oxidizing the periodic grating.
り、−Ｃ面に周期的な分極反転を形成する請求項１記載
の二次高調波発生素子の製造方法。2. The method for manufacturing a second harmonic generation element according to claim 1, wherein the ferroelectric substrate is a LiNbO 3 substrate, and periodic polarization inversion is formed on the −C plane.
反転層と、 この周期的な分極反転層と交差するように前記強誘電体
基板に形成された光導波路とを備えた二次高調波発生素
子において、 前記強誘電体基板はＬｉＮｂＯ3 基板であり、 前記分極反転層は、このＬｉＮｂＯ3 基板の−Ｃ面に、
その基板の厚さに比べて十分に薄く形成されたことを特
徴とする二次高調波発生素子。3. A secondary device comprising a periodic domain-inverted layer formed on a ferroelectric substrate, and an optical waveguide formed on the ferroelectric substrate so as to intersect with the periodic domain-inverted layer. In the harmonic generating device, the ferroelectric substrate is a LiNbO 3 substrate, and the polarization inversion layer is on the −C plane of the LiNbO 3 substrate.
A second harmonic generation element characterized by being formed sufficiently thinner than the thickness of the substrate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2137992A JPH0667237A (en) | 1992-02-06 | 1992-02-06 | Second harmonic wave generating element and its production |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2137992A JPH0667237A (en) | 1992-02-06 | 1992-02-06 | Second harmonic wave generating element and its production |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0667237A true JPH0667237A (en) | 1994-03-11 |
Family
ID=12053463
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2137992A Pending JPH0667237A (en) | 1992-02-06 | 1992-02-06 | Second harmonic wave generating element and its production |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0667237A (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03191332A (en) * | 1989-12-20 | 1991-08-21 | Matsushita Electric Ind Co Ltd | Production of optical waveguide and optical wavelength converting element |
-
1992
- 1992-02-06 JP JP2137992A patent/JPH0667237A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03191332A (en) * | 1989-12-20 | 1991-08-21 | Matsushita Electric Ind Co Ltd | Production of optical waveguide and optical wavelength converting element |
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