JPH0574802B2 - - Google Patents
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- Publication number
- JPH0574802B2 JPH0574802B2 JP60118309A JP11830985A JPH0574802B2 JP H0574802 B2 JPH0574802 B2 JP H0574802B2 JP 60118309 A JP60118309 A JP 60118309A JP 11830985 A JP11830985 A JP 11830985A JP H0574802 B2 JPH0574802 B2 JP H0574802B2
- Authority
- JP
- Japan
- Prior art keywords
- substrate
- linbo
- refractive index
- phosphoric acid
- index layer
- 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 - Lifetime
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Description
【発明の詳細な説明】
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
導波路およびマイクロレンズの製造に用いる光素
子形成方法に関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming optical elements used in the manufacture of optical waveguides and microlenses used in the field of optical information processing using coherent light or the field of optical applied measurement and control. be.
従来の技術
従来、強誘電体基板であるLiNbO3基板にCrま
たはAl膜などを蒸着しフオトプロセスおよびエ
ツチングにより幅数μｍのスリツトを開けたもの
を安息香酸中で熱処理を行い高屈折率層（屈折率
差Δn＝0.13程度）を形成していた。（ジエー・エ
ル・ジヤツケル、シー・イー・ライス及びジエ
ー・ジエー・ベセルカ プロトン イクスチエン
ジ フオア ハイーインデツクス ウエイブガイ
ツ インLiNbO3”、アプライド フイジツクス
レター、41巻、７号、607−608貢（1982年）（J.
L.Jackel、C.E.Rice and J.J.Veselka、Proton
Exchange for High−index Waveguides in
LiNbO3”、Appl.Phys.Lett、Vol41、No.７、
pp607−608（1982）参照）以下光素子として光導
波路形成について説明する。第４図に従来のプロ
トン交換方法を用いた光導波路形成の具体的構成
を示す。１は強誘電体基板であるLiNbO3基板、
２は保護マスクとなるAl膜、３はフオトプロセ
スおよびエツチングにより保護マスク２上に形成
されたスリツトである。上記LiNbO3基板１は安
息香酸４中に浸されている。ちなみに安息香酸４
の解離指数は4.12で融点122℃、沸点248℃であ
る。安息香酸４が入れられた石英ビーカ５はヒー
タ６により熱処理温度Tcが200℃の温度に保たれ
ており安息香酸４はこの温度では液体である。こ
の安息香酸４中でLiNbO3基板１を60分熱処理を
行つた後、メタノールにより洗浄を行う。こうし
て安息香酸４中の水素とLiNbO3基板１中のリチ
ウムが交換し、高屈折率層７が形成される。この
高屈折率層７が0.5μｍ程度の光導波路となる。Conventional technology Conventionally, a ferroelectric LiNbO 3 substrate is deposited with a Cr or Al film, a slit several micrometers wide is made by photo processing and etching, and then heat treated in benzoic acid to form a high refractive index layer ( A refractive index difference Δn=about 0.13) was formed. (G.L. Jackel, C.E. Rice and G.G. Beselka, “Proton Index Wavelengths in LiNbO 3 ”, Applied Physics Letters, Vol. 41, No. 7, 607-608 (1982) ) (J.
L. Jackel, CERice and JJ Veselka, Proton
Exchange for High−index Waveguides in
LiNbO 3 ”, Appl.Phys.Lett, Vol41, No.7,
pp. 607-608 (1982)) Formation of an optical waveguide as an optical element will be explained below. FIG. 4 shows a specific configuration for forming an optical waveguide using the conventional proton exchange method. 1 is a LiNbO 3 substrate which is a ferroelectric substrate,
2 is an Al film serving as a protective mask, and 3 is a slit formed on the protective mask 2 by photo process and etching. The LiNbO 3 substrate 1 is immersed in benzoic acid 4. By the way, benzoic acid 4
The dissociation index is 4.12, the melting point is 122℃, and the boiling point is 248℃. A quartz beaker 5 containing benzoic acid 4 is kept at a heat treatment temperature Tc of 200° C. by a heater 6, and benzoic acid 4 is a liquid at this temperature. After heat-treating the LiNbO 3 substrate 1 in this benzoic acid 4 for 60 minutes, it is washed with methanol. In this way, hydrogen in benzoic acid 4 and lithium in LiNbO 3 substrate 1 are exchanged, and high refractive index layer 7 is formed. This high refractive index layer 7 becomes an optical waveguide of about 0.5 μm.
発明が解決しようとする課題
上記のような酸として安息香酸を用いた光素子
形成方法では、安息香酸の解離指数PKaが4.12と
大きく溶液中の水素濃度が低いため屈折率差Δn
を0.13以上大きくするのが困難である。また沸点
が248℃にあるためそれ以上高温にして拡散定数
を高めることが困難となり素子の作製に時間がか
かるなどの問題もあつた。Problems to be Solved by the Invention In the optical device formation method using benzoic acid as the acid as described above, the dissociation index PKa of benzoic acid is 4.12 and the hydrogen concentration in the solution is low, so the refractive index difference Δn
It is difficult to increase the value by more than 0.13. Furthermore, since the boiling point is 248°C, it is difficult to increase the diffusion constant by increasing the temperature higher than that, resulting in problems such as the time it takes to fabricate devices.
課題を解決するための手段
本発明の光素子形成方法は上記問題点を解決す
るため、リン酸中でLiNbxTa1-xO3（０≦ｘ≦１）
基板に熱処理を行い、前記基板に高屈折率層を形
成するものである。Means for Solving the Problems In order to solve the above-mentioned problems, the optical device forming method of the present invention uses LiNb x Ta 1-x O 3 (0≦x≦1) in phosphoric acid.
A high refractive index layer is formed on the substrate by subjecting the substrate to heat treatment.
作 用
本発明は上記手段によりリン酸中での熱処理時
において水素濃度が高いため容易に0.13以上の屈
折率差Δnを持つ高屈折率層を形成できる。しか
も高温処理が可能となるため素子の作製時間を大
幅に短縮することができる。Function The present invention can easily form a high refractive index layer having a refractive index difference Δn of 0.13 or more due to the high hydrogen concentration during heat treatment in phosphoric acid by the above-mentioned means. Moreover, since high-temperature processing becomes possible, the time for manufacturing elements can be significantly shortened.
実施例
本発明の光素子形成方法の第１の実施例を第１
図を用いて説明する。この第１の実施例では光素
子として光導波路の形成について説明する。１は
強誘電体基板であるLiNbO3基板、２はLiNbO3
基板１の＋Ｚ面上に形成された保護マスクとなる
Ti−Au膜でTiの膜厚500Å、Auの膜厚500Åで
ある。３はフオトプロセスおよびエツチングによ
り保護マスク２上に形成されたスリツトである。
上記LiNbO3基板１はリン酸８中に浸されてい
る。Example A first example of the method for forming an optical element of the present invention is described below.
This will be explained using figures. In this first embodiment, the formation of an optical waveguide as an optical element will be explained. 1 is LiNbO 3 substrate which is a ferroelectric substrate, 2 is LiNbO 3
Serves as a protective mask formed on the +Z surface of the substrate 1
The Ti-Au film has a Ti film thickness of 500 Å and an Au film thickness of 500 Å. 3 is a slit formed on the protective mask 2 by photo process and etching.
The LiNbO 3 substrate 1 is immersed in phosphoric acid 8.
リン酸はオルトリン酸（H3PO4）、ピロリン酸
（H4P2O7）の総称であり、ちなみに215℃以上の
温度ではリン酸８はオルトリン酸（PKa＝2.2）
とピロリン酸（PKa＝1.7）が混在している。リ
ン酸８が入れられた石英ビーカ５は温度コントロ
ーラ付のヒータ６により常にTc＝250℃の温度に
保たれている。LiNbO3基板１を４分間熱処理を
行い引き出した後流水で洗浄を行う。このように
して厚み0.5μｍの高屈折率層７が形成され、この
高屈折率層７が光導波路となる。 Phosphoric acid is a general term for orthophosphoric acid (H 3 PO 4 ) and pyrophosphoric acid (H 4 P 2 O 7 ), and by the way, at temperatures above 215°C, phosphoric acid 8 becomes orthophosphoric acid (PKa = 2.2)
and pyrophosphoric acid (PKa = 1.7). A quartz beaker 5 containing phosphoric acid 8 is constantly maintained at a temperature of Tc=250°C by a heater 6 equipped with a temperature controller. The LiNbO 3 substrate 1 is subjected to heat treatment for 4 minutes, and after being pulled out, it is washed with running water. In this way, a high refractive index layer 7 having a thickness of 0.5 μm is formed, and this high refractive index layer 7 becomes an optical waveguide.
リン酸８は解離指数PKaが２程度と低く、水
素濃度が高いためΔn＝0.14程度の高屈折率層を
形成できる。またリン酸８は水に可溶なためプロ
トン交換後の洗浄も容易である。さらにリン酸４
は安価である。またリン酸４は蒸発が少い上に融
点が室温以下であるので蒸発しても固化して周囲
に付着し作業を妨げることもない。 Since phosphoric acid 8 has a low dissociation index PKa of about 2 and a high hydrogen concentration, it is possible to form a high refractive index layer with Δn=about 0.14. Further, since phosphoric acid 8 is soluble in water, cleaning after proton exchange is easy. Furthermore, phosphoric acid 4
is cheap. Furthermore, since phosphoric acid 4 evaporates less and has a melting point below room temperature, even if it evaporates, it will not solidify and adhere to the surroundings and hinder work.
なおLiNbO3１の＋Ｚ面または−Ｚ面は酸によ
る化学損傷を受けにくくプロトン交換を行うには
有利である。 Note that the +Z face or -Z face of LiNbO 3 1 is less susceptible to chemical damage by acids and is advantageous for proton exchange.
次に本発明の光素子形成方法の第２の実施例に
ついて第２図を用いて説明する。第２の実施例で
は光素子としてマイクロレンズを形成する方法を
示している。第２図はマイクロレンズ形成工程を
示す断面図で、第１図におけるLiNbO3基板１上
のスリツト３がレンズとなる円形部９に変わつて
いる。第１の実施例と同様にリン酸８中でプロト
ン交換を行う。第３図にプロトン交換時間に対す
るプロトン交換深さの関係を示す。第３図よりＴ
＝280℃の温度では6.3時間の熱処理を行うことに
より10μｍの深さの高屈折率層７が得られる。こ
れに対して10μｍの深さを得るためにはＴ＝230
℃の安息香酸ではほぼ100時間かかり、高温処理
が製造時間の短縮に大いに寄与していることがわ
かる。また同様にフレネルレンズ、グレーテイン
グレンズなどの形成にも使用できる。 Next, a second embodiment of the optical device forming method of the present invention will be described with reference to FIG. The second embodiment shows a method of forming a microlens as an optical element. FIG. 2 is a cross-sectional view showing the microlens forming process, in which the slit 3 on the LiNbO 3 substrate 1 in FIG. 1 has been replaced with a circular portion 9 that will become a lens. Proton exchange is performed in phosphoric acid 8 in the same manner as in the first example. FIG. 3 shows the relationship between the proton exchange time and the proton exchange depth. From Figure 3, T
At a temperature of =280°C, a high refractive index layer 7 with a depth of 10 μm can be obtained by performing heat treatment for 6.3 hours. On the other hand, to obtain a depth of 10 μm, T = 230
Benzoic acid at ℃ takes approximately 100 hours, indicating that high-temperature treatment greatly contributes to shortening the production time. It can also be similarly used to form Fresnel lenses, grating lenses, etc.
なお実施例では強誘電対基板として良質の結晶
が得易いLiNbO3基板を用いたが他にLiTaO3な
ども使用できる。LiTaO3はLiNbO3に比べて拡
散定数が小さいため高温処理が極めて有効とな
る。 In the embodiment, a LiNbO 3 substrate from which high-quality crystals can easily be obtained was used as the ferroelectric pair substrate, but other materials such as LiTaO 3 can also be used. Since LiTaO 3 has a smaller diffusion constant than LiNbO 3 , high-temperature treatment is extremely effective.
また、300℃以上の温度でも液体であるリン酸
を用いることにより蒸気も少なく安定かつ再現性
良く高温でのプロトン交換が行える。また、リン
酸を用いたプロトン交換により高屈折率層（Δn
＝0.14）を化学損傷をほとんど受けずに得ること
ができる。なお、解離指数PKaが１以下の酸で
は化学損傷を起こし易く使用できない。 Furthermore, by using phosphoric acid, which is liquid even at temperatures above 300°C, proton exchange at high temperatures can be performed stably and reproducibly with little vapor. In addition, a high refractive index layer (Δn
= 0.14) can be obtained with almost no chemical damage. Note that acids with a dissociation index PKa of 1 or less cannot be used because they tend to cause chemical damage.
ところで熱処理を行う温度が170℃以下では拡
散定数が低く工業的に問題である。また熱処理を
行う温度が300℃以上では酸の状態が大きく変化
し易く再現性が悪くなる。 However, if the heat treatment temperature is 170° C. or lower, the diffusion constant is low, which is an industrial problem. Furthermore, if the temperature at which the heat treatment is performed is 300° C. or higher, the state of the acid tends to change significantly, resulting in poor reproducibility.
発明の効果
本発明による光素子形成方法のように、リン酸
中でLiNbxTa1-xO3（０≦ｘ≦１）基板を熱処理
し、プロトン交換を行うことでLiNbxTa1-xO3
（０≦ｘ≦１）基板に従来得られなかつた高屈折
率層を形成できる上に、高温処理ができプロトン
交換時間を大幅に短縮できる。Effects of the Invention As in the method for forming an optical device according to the present invention, LiNb x Ta 1-x O 3 (0≦x≦1) is heat-treated in phosphoric acid to perform proton exchange . O 3
(0≦x≦1) In addition to being able to form a high refractive index layer on the substrate, which has not been previously possible, high temperature treatment can be performed and the proton exchange time can be significantly shortened.
第１図は本発明の光素子形成方法の第１の実施
例を説明するための図、第２図は本発明の光素子
形成方法の第２の実施例を用いたマイクロレンズ
形成工程を説明するための図、第３図はプロトン
交換時間に対するプロトン交換深さの関係を示す
図、第４図は従来の光素子形成方法を説明するた
めの図である。
１……LiNbO3、２……保護マスク、３……ス
リツト、７……高屈折率層、８……リン酸。
FIG. 1 is a diagram for explaining a first embodiment of the optical device forming method of the present invention, and FIG. 2 is a diagram for explaining a microlens forming process using the second embodiment of the optical device forming method of the present invention. FIG. 3 is a diagram showing the relationship between the proton exchange depth and the proton exchange time, and FIG. 4 is a diagram for explaining the conventional method for forming an optical element. 1... LiNbO 3 , 2... Protective mask, 3... Slit, 7... High refractive index layer, 8... Phosphoric acid.
Claims (1)
板に熱処理を行い、前記基板に高屈折率層を形成
すること特徴とする光素子形成方法。 ２ 熱処理を行う温度Ｔが170℃≦Ｔ≦300℃の範
囲であることを特徴とする特許請求の範囲第１項
記載の光素子形成方法。 ３ LiNbxTa1-xO3（０≦ｘ≦１）の＋Ｚ面また
は−Ｚ面を用いることを特徴とする特許請求の範
囲第１項記載の光素子形成方法。[Claims] 1. A method for forming an optical device, which comprises: heat-treating a LiNb x Ta 1-x O 3 (0≦x≦1) substrate in phosphoric acid to form a high refractive index layer on the substrate. . 2. The optical device forming method according to claim 1, wherein the temperature T at which the heat treatment is performed is in the range of 170°C≦T≦300°C. 3. The optical device forming method according to claim 1, wherein the +Z plane or the -Z plane of 3 LiNb x Ta 1-x O 3 (0≦x≦1) is used.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60118309A JPS61275806A (en) | 1985-05-31 | 1985-05-31 | Optical device formation method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60118309A JPS61275806A (en) | 1985-05-31 | 1985-05-31 | Optical device formation method |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4097601A Division JP2538161B2 (en) | 1992-04-17 | 1992-04-17 | Method for manufacturing optical waveguide and lens |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61275806A JPS61275806A (en) | 1986-12-05 |
| JPH0574802B2 true JPH0574802B2 (en) | 1993-10-19 |
Family
ID=14733487
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60118309A Granted JPS61275806A (en) | 1985-05-31 | 1985-05-31 | Optical device formation method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61275806A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1324261C (en) * | 1988-05-03 | 1993-11-16 | Jeffrey Bruce Bindell | Proton-exchange method of forming optical waveguides |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS607403A (en) * | 1983-06-28 | 1985-01-16 | Canon Inc | Forming method of thin film type optical waveguide |
-
1985
- 1985-05-31 JP JP60118309A patent/JPS61275806A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61275806A (en) | 1986-12-05 |
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Legal Events
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|---|---|---|---|
| EXPY | Cancellation because of completion of term |