JPS6150288B2 - - Google Patents
Info
- Publication number
- JPS6150288B2 JPS6150288B2 JP7602678A JP7602678A JPS6150288B2 JP S6150288 B2 JPS6150288 B2 JP S6150288B2 JP 7602678 A JP7602678 A JP 7602678A JP 7602678 A JP7602678 A JP 7602678A JP S6150288 B2 JPS6150288 B2 JP S6150288B2
- Authority
- JP
- Japan
- Prior art keywords
- light
- crystal
- optical modulator
- electric field
- medium
- 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
Links
- 230000003287 optical effect Effects 0.000 claims description 45
- 230000005684 electric field Effects 0.000 claims description 21
- 230000000694 effects Effects 0.000 claims description 11
- 230000010287 polarization Effects 0.000 claims description 10
- 230000005540 biological transmission Effects 0.000 claims description 5
- 230000007423 decrease Effects 0.000 claims description 4
- 230000000737 periodic effect Effects 0.000 claims description 4
- 238000013459 approach Methods 0.000 claims description 2
- 239000013078 crystal Substances 0.000 description 45
- 238000000034 method Methods 0.000 description 13
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 description 9
- 238000010586 diagram Methods 0.000 description 5
- 230000008033 biological extinction Effects 0.000 description 4
- 239000010409 thin film Substances 0.000 description 4
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 238000010897 surface acoustic wave method Methods 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Description
【発明の詳細な説明】
本発明はレーザ光の位相、偏光状態、強度など
を時間的に変調する光変調素子に関し、特に結晶
の電気光学効果を利用した光変調器に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical modulator that temporally modulates the phase, polarization state, intensity, etc. of a laser beam, and particularly relates to an optical modulator that utilizes the electro-optic effect of a crystal.
光変調素子はレーザ光を使つた多くのシステ
ム、例えば、光通信システム、光メモリシステ
ム、レーザ記録システム、レーザデイスプレイシ
ステムなど高速に大容量の情報を伝達し、読取
り、記録し、表示する装置には必要不可決な素子
である。光変調素子には、機械的な変形や振動を
使つたもの、音響光学効果を使つたもの、電気光
学効果を使つたものなどがある。これらのうちで
結晶の電気光学効果を使つた変調器は広い帯域幅
をもち、高速で光を変調できるという特長があ
る。 Light modulation elements are used in many systems that use laser light, such as optical communication systems, optical memory systems, laser recording systems, laser display systems, and other devices that transmit, read, record, and display large amounts of information at high speed. It is an element that is not necessary. Light modulation elements include those that use mechanical deformation or vibration, those that use an acousto-optic effect, and those that use an electro-optic effect. Among these, modulators that use the electro-optic effect of crystals have the advantage of having a wide bandwidth and being able to modulate light at high speed.
結晶の電気光学効果を使つた光変調器には、(1)
電気光学結晶の２つの主軸方向の偏光成分間の位
相遅延量を電気的に制御して光の偏光状態を変換
する光変調器、(2)電気光学結晶に空間的周期電界
を加え、それによつて生じた位相格子によつて光
をブラツク回折、またはラマン・ナース回折させ
て変調する光変調器、(3)屈折率楕円体の回転を生
じせしめる電気光学効果を使い、光透過方向に周
期的な電界を印加することによつて入射直線偏光
をこの偏光と直光する偏光成分に変換する光変調
器等がある。これらのうち、(2)の光変調器は電極
パターンによる回折が生ずることや、回折角度を
大きくするのが難しいために消光比が低いという
欠点がある。(1)の光変調器は普通、APP結晶、
KDP結晶、タンタル酸リチウム結晶等の電気光
学定数が大きい結晶を用いて作る。しかし、
ADP結晶やKDP結晶を用いた場合は、結晶に潮
解性があるので取扱いが難しいことや、高い電圧
が必要であるという欠点がある。タンタル酸リチ
ウム結晶を用いた場合は、印加電圧は低くてよい
が、周囲温度が変化したとき、電圧を加えなくて
も偏光状態が変化してしまうので高い消光比が得
られないという欠点がある。このタンタル酸リチ
ウムを用いた(1)の光変調器では２つの結晶を継続
して用いることにより温度補償を行なう方法が知
られているが結晶の均質性や高い製作精度を必要
とするので実用的ではない。また(1)の光変調器で
は入射光波長が限定されてしまう。一方、(3)の光
変調器は比較的低電圧で動作し、高い消光比が容
易に得られる。第１図は３の光変調器の構成を示
す図である。図において、１はＸ軸に垂直に切り
出し、Ｙ軸方向に光を透過させるように形成した
タンタル酸リチウム結晶である。結晶上にはイン
ターデイジタル電極２が設けられており、信号発
生器３が電極２に接続されている。ここで、電極
２の周期Λは、
２π／Λ＝２π｜ne−no｜／λ (1)
をほぼ満足する値に選ばれている。no、neはそ
れぞれ結晶１の常光、異常光に対する届折率、λ
は真空中の光波長である。結晶１の厚さはインタ
ーデイジタル電極の電極指間の間隔により薄くさ
れている。結晶の裏面には一様に電極が蒸着され
接続されている。入射光４はＸ軸方向の直線偏光
である。結晶１の出射側にはＺ軸方向の偏光成分
のみを通過する検光子６が置かれている。検光子
６を通過した光７は変調された出力光である。次
にこの３の光変調器の動作原理を説明する。信号
発生器３の電圧が０のとき、出射光５の偏光状態
は入射光４と同じであるので、出射光５は検光子
６により遮断され、出力光７の強度は０となる。
信号発生器３の電圧が０でないとき、結晶１中に
はＸ軸方向の電界がＹ方向に周期的に印加され
る。該電界と結晶１のポツケルス係数r51により
入射光４はＺ軸方向の偏光成分を有する光に変換
される。印加電圧を増すに従い、上記のＸ軸方向
の偏光からＺ軸方向の偏光に変換される割合は増
加し、ある電圧では100％変換される。以上の原
理により、出力光７は信号発生器３によつて変調
される。 Optical modulators using the electro-optic effect of crystals include (1)
(2) an optical modulator that converts the polarization state of light by electrically controlling the amount of phase delay between the polarization components in the two principal axes of the electro-optic crystal; (2) applying a spatially periodic electric field to the electro-optic crystal; (3) An optical modulator that modulates light by Black diffraction or Raman-Nurss diffraction using a phase grating generated by the process. There is an optical modulator that converts incident linearly polarized light into a polarized light component that is direct to the polarized light by applying an electric field. Among these, the optical modulator (2) has the disadvantage that diffraction occurs due to the electrode pattern and that the extinction ratio is low because it is difficult to increase the diffraction angle. (1) The optical modulator is usually an APP crystal,
It is made using a crystal with a large electro-optical constant such as KDP crystal or lithium tantalate crystal. but,
When ADP crystals or KDP crystals are used, there are drawbacks such as the fact that the crystals are deliquescent and therefore difficult to handle, and that high voltage is required. When using lithium tantalate crystals, the applied voltage can be low, but the drawback is that when the ambient temperature changes, the polarization state changes even without applying a voltage, making it impossible to obtain a high extinction ratio. . In the optical modulator (1) using lithium tantalate, a method is known in which temperature compensation is achieved by continuously using two crystals, but this requires crystal homogeneity and high manufacturing precision, so it is not practical. Not the point. Furthermore, in the optical modulator (1), the wavelength of incident light is limited. On the other hand, the optical modulator (3) operates at a relatively low voltage and can easily obtain a high extinction ratio. FIG. 1 is a diagram showing the configuration of a third optical modulator. In the figure, 1 is a lithium tantalate crystal cut perpendicularly to the X-axis and formed to transmit light in the Y-axis direction. An interdigital electrode 2 is provided on the crystal, and a signal generator 3 is connected to the electrode 2. Here, the period Λ of the electrode 2 is selected to a value that approximately satisfies 2π/Λ=2π|ne−no|/λ (1). no and ne are the delivered refractive indexes of crystal 1 for ordinary light and extraordinary light, respectively, and λ
is the wavelength of light in vacuum. The thickness of the crystal 1 is reduced by the spacing between the electrode fingers of the interdigital electrodes. Electrodes are uniformly deposited and connected to the back surface of the crystal. The incident light 4 is linearly polarized light in the X-axis direction. An analyzer 6 is placed on the output side of the crystal 1, which passes only the polarized light component in the Z-axis direction. The light 7 that has passed through the analyzer 6 is modulated output light. Next, the operating principle of these three optical modulators will be explained. When the voltage of the signal generator 3 is 0, the polarization state of the output light 5 is the same as that of the input light 4, so the output light 5 is blocked by the analyzer 6, and the intensity of the output light 7 becomes 0.
When the voltage of the signal generator 3 is not zero, an electric field in the X-axis direction is periodically applied to the crystal 1 in the Y-direction. The electric field and the Pockels coefficient r 51 of the crystal 1 convert the incident light 4 into light having a polarization component in the Z-axis direction. As the applied voltage increases, the rate of conversion from the polarized light in the X-axis direction to the polarized light in the Z-axis direction increases, and at a certain voltage, the conversion is 100%. Based on the above principle, the output light 7 is modulated by the signal generator 3.
この３の光変調器では電圧を印加しないとき、
入射光の偏光状態は温度によつて影響されないの
で高い消光比を得ることができる。また、印加電
圧は前述の２のADP結晶やKDP結晶を用いた光
変調器よりは小さくてよい。しかし、周囲温度が
変化すると、｜ne−no｜の値が変化し、位相整
合条件を示す(1)式が満たされなくなるので変調効
率が低下してしまう。この温度特性の欠点を改善
するための手段として、電極の周期をΛを中心と
して光透過方向に連続的に変化させる方法が特願
昭52−8534号（特開昭53−93856号）の明細書
に、そして｜ne−no｜の値が光透過方向に連続
的に変化している結晶を変調媒体として用いる方
法が特願昭52−92852号の明細書にそれぞれ示さ
れている。上記の方法を用いると変調可能な温度
範囲は広くすることができる。しかし、変調効率
の温度特性には変動が生じてしまう。その原因は
用いる結晶の長さが有限であり、電極本数が有限
であるためである。一例として、長さ20mm、25℃
においてne−no＝3.164×10-3であるタンタル酸
リチウム結晶上に電極指幅と電極指間隔の比を一
定として電極周期を156μｍから284μｍまで変化
させたインターデイジタル電極を設けた光変調器
において80V／100μの電界を印加したときの変
調効率の温度特性を第２図に示す。第２図からわ
かるように10℃から40℃にわたつて大きな変調効
率が得られるがその範囲には30％以上の変動が生
じている。また(1)式から明らかなように(3)の光変
調器では、変調効率は入射光の波長入が変化して
も温度変化に対する変動と同様の変動が生ずる。 In this third optical modulator, when no voltage is applied,
Since the polarization state of the incident light is not affected by temperature, a high extinction ratio can be obtained. Further, the applied voltage may be smaller than the above-mentioned 2 optical modulator using ADP crystal or KDP crystal. However, when the ambient temperature changes, the value of |ne−no| changes, and equation (1) representing the phase matching condition is no longer satisfied, resulting in a decrease in modulation efficiency. As a means to improve this drawback of temperature characteristics, a method is disclosed in Japanese Patent Application No. 52-8534 (Japanese Unexamined Patent Publication No. 53-93856) in which the period of the electrode is continuously changed in the light transmission direction with Λ as the center. Japanese Patent Application No. 52-92852 discloses a method of using a crystal in which the value of |ne-no| continuously changes in the light transmission direction as a modulation medium. Using the above method, the modifiable temperature range can be widened. However, variations occur in the temperature characteristics of modulation efficiency. This is because the length of the crystal used is finite and the number of electrodes is finite. As an example, length 20mm, 25℃
In an optical modulator in which an interdigital electrode is provided on a lithium tantalate crystal with ne-no = 3.164 × 10 -3 with a constant ratio of electrode finger width and electrode finger spacing and the electrode period is varied from 156 μm to 284 μm. Figure 2 shows the temperature characteristics of modulation efficiency when an electric field of 80V/100μ is applied. As can be seen from Figure 2, a large modulation efficiency is obtained from 10°C to 40°C, but there is a variation of more than 30% in that range. Furthermore, as is clear from equation (1), in the optical modulator of (3), even if the wavelength input of the incident light changes, the modulation efficiency fluctuates in the same manner as the fluctuation due to temperature change.
本発の目的は上述した従来の光変調器よりも温
度変化及び入射光波長の変化に対する変調効率の
変動が小さい高性能な光変調器を提供することに
ある。 An object of the present invention is to provide a high-performance optical modulator whose modulation efficiency varies less with respect to temperature changes and changes in incident light wavelength than the conventional optical modulators described above.
本発明によれば、電気光学効果を有する光変調
媒体と、該媒体の光透過方向に周期的な電界を印
加する手段とを含み、該透過光の偏光成分の少な
くとも一部を該偏光成分と直光する偏光成分に変
換する光変調器において、前記光変調媒体の少な
くとも一部で前記印加電界の大きさを光透過方向
に沿つて順次変化させることにより、従来の光調
器の温度特性及び入射光波長に対する特性を改善
することができ、特に、前記光変調媒体の周辺部
において、印加する電界の大きさを該媒体の光の
入出射端に近づくに従つて減少させることによ
り、温度変化及び入射光波長変化に対して変調効
率の変動が小さい安定な光変調器を得ることがで
きる。 According to the present invention, the present invention includes a light modulating medium having an electro-optic effect and a means for applying a periodic electric field in the light transmission direction of the medium, and converts at least a part of the polarized light component of the transmitted light into the polarized light component. In an optical modulator that converts light into a direct polarized light component, the temperature characteristics and It is possible to improve the characteristics with respect to the wavelength of incident light, and in particular, by reducing the magnitude of the applied electric field at the periphery of the light modulation medium as it approaches the light input/output end of the medium, temperature changes can be improved. Furthermore, it is possible to obtain a stable optical modulator in which the modulation efficiency fluctuates little with respect to changes in the wavelength of incident light.
以下に図面を参照して本発明を詳細に説明す
る。第３図は本発明による光変調器の一実施例を
示す図であり、光変調器の上面図である。図にお
いて、１１は第１図に示した結晶１と同じ材質で
全く同じ方位、形状をもつたタンタル酸リチウム
結晶である。１４は入射光であり、１５は出射
光、１６はＺ軸方向の偏光成分のみを通過する検
光子であり、１７は出力光である。結晶１１上に
は斜線で示した2N本の電極A1，A2，……，ＡNと
B1，B2，……，ＢNが設置されている。そして
A1，A2，……，ＡNにはそれぞれ＋V1，＋V2，…
…，＋ＶNが印加され、B1，B2，……，ＢNにはそ
れぞれ−V1，−V2，……，−ＶNが印加される。結
晶の裏側には全体に一様な電極が設置されアース
されている。電極周期はＹ方向に連続的に変化し
ている。ここで、印加電圧の大きさは、
Vj＝Vo（ｊ＝ｋ、ｋ＋１、……、Ｎ−１）、V1
＜……＜Vk＝Vo、Vo＝ＶN-l＞ＶN-l+1＞……＞
ＶN-1＞ＶNの関係を満たすように選ばている。こ
のとき結晶の両端の部分では、結晶の端に行くに
従つて除々に印加電界が減少する。本実施例の光
変調器の構成は、電極構造、電圧の印加方法を除
いて第１図の光変調器と同じであり、基本的な動
作原理も同じある。ただし、本実施例において
は、上述のように印加電界を結晶の端で除々に減
少させることにより、第１図の従来の光変調器で
生ずる電極本数が有限であるための影響、すなわ
ち効率の変動を減少させることができる。一例と
して、第２図に特性を示した光変調器と同じ結晶
を用い、第２図の例と同じ電極指幅、電極指間隔
で同じ対数の電極を第３図に示した光変調器のよ
うに、各対ごとに分割して設置した光変調器にお
いて、結晶の両端からそれぞれ2.4mmの部分に、
印加する電圧を端に行く従つてほぼ正弦的に減少
させたときの変調効率の温度特性を第４図に示
す。第４図からわかるように、本実施例では第２
図に示した従来の光変調器の温度特性よりも非常
に効率の変動の小さい特性が得られる。また、入
射光波長の変化に対しても従来の光変調器よりも
変調効率の変動が小さいのはいうまでもない。本
発明による効果は、弾性表面波のトランスジユー
サの周波数特性を改善させるために用いられる電
極の重みづけによる効果とよく類似している。 The present invention will be described in detail below with reference to the drawings. FIG. 3 is a diagram showing an embodiment of the optical modulator according to the present invention, and is a top view of the optical modulator. In the figure, reference numeral 11 is a lithium tantalate crystal made of the same material as crystal 1 shown in FIG. 1 and having exactly the same orientation and shape. 14 is incident light, 15 is output light, 16 is an analyzer that passes only the polarized light component in the Z-axis direction, and 17 is output light. On the crystal 11, there are 2N electrodes A 1 , A 2 , ..., A N indicated by diagonal lines.
B 1 , B 2 , ..., B N are installed. and
A 1 , A 2 , ..., A N have +V 1 , +V 2 , ..., respectively.
..., +V N are applied, and -V 1 , -V 2 , ..., -V N are applied to B 1 , B 2 , ..., B N , respectively. On the back side of the crystal, a uniform electrode is placed over the entire surface and grounded. The electrode period changes continuously in the Y direction. Here, the magnitude of the applied voltage is Vj = Vo (j = k, k+1, ..., N-1), V 1
<...<Vk=Vo, Vo=V Nl >V N-l+1 >...>
It is selected to satisfy the relationship V N-1 > V N. At this time, at both ends of the crystal, the applied electric field gradually decreases toward the ends of the crystal. The structure of the optical modulator of this embodiment is the same as that of the optical modulator shown in FIG. 1 except for the electrode structure and voltage application method, and the basic operating principle is also the same. However, in this example, by gradually reducing the applied electric field at the edge of the crystal as described above, the effect of the finite number of electrodes that occurs in the conventional optical modulator shown in FIG. Fluctuations can be reduced. As an example, the optical modulator shown in FIG. 3 is constructed using the same crystal as the optical modulator whose characteristics are shown in FIG. In the optical modulators installed separately for each pair, 2.4 mm apart from both ends of the crystal,
FIG. 4 shows the temperature characteristics of the modulation efficiency when the applied voltage is decreased almost sinusoidally toward the end. As can be seen from FIG. 4, in this example, the second
Characteristics with much smaller fluctuations in efficiency than the temperature characteristics of the conventional optical modulator shown in the figure can be obtained. Furthermore, it goes without saying that the modulation efficiency fluctuates less than in conventional optical modulators with respect to changes in the wavelength of incident light. The effect of the present invention is very similar to the effect of electrode weighting used to improve the frequency characteristics of surface acoustic wave transducers.
第５図は本発明による光変調器の他実施例を示
す斜視図である。第５図において、２１はＸ軸に
垂直に切り出し、Ｙ軸方向に光透過させるように
形成したタンタル酸リチウム結晶である。ただ
し、本実施例においては、結晶２１の厚さは一様
ではなく、光の入出射端において、Ｙ方向に端に
行くに従つて除々に厚くなつている。結晶上には
周期ΛがＹ方向に除々に変化したインターデイジ
タル電極２２が設けられており、信号発生器器２
３によつてＸ軸方向の電界がＹ方向に周期的に印
加される。印加電界の大きさは結晶の中心部分で
は一様であるが厚さが大きい結晶の両端では除々
に減少している。本実施例においても第４図の実
施例と同様な効果が得られ安定な温度特性が得ら
れる。本実施例は、第４図に示す実施例に比べ、
電圧の印加方法が簡単である。第５図において、
２４は入射光、２５は出射光、２６は検光子であ
り、２７は出力光である。 FIG. 5 is a perspective view showing another embodiment of the optical modulator according to the present invention. In FIG. 5, 21 is a lithium tantalate crystal cut perpendicularly to the X-axis and formed to transmit light in the Y-axis direction. However, in this embodiment, the thickness of the crystal 21 is not uniform, and gradually becomes thicker toward the end in the Y direction at the light input/output end. An interdigital electrode 22 whose period Λ gradually changes in the Y direction is provided on the crystal, and the signal generator 2
3, an electric field in the X-axis direction is periodically applied in the Y-direction. The magnitude of the applied electric field is uniform at the center of the crystal, but gradually decreases at both ends of the crystal, where the thickness is large. In this embodiment as well, effects similar to those of the embodiment shown in FIG. 4 can be obtained, and stable temperature characteristics can be obtained. In this embodiment, compared to the embodiment shown in FIG.
The voltage application method is simple. In Figure 5,
24 is incident light, 25 is output light, 26 is an analyzer, and 27 is output light.
以上述べたように本発明によれば、周期的な電
界を印加して入射光の偏光方向を変換する電気光
学変調器において、変調媒体の端に行くに従つて
印加電界の大きさを除々に減少させることによ
り、従来よりも優れた温度特性をもちかつ、入射
光の波長変動に対しても安定な光変調器を得るこ
とができる。 As described above, according to the present invention, in an electro-optic modulator that applies a periodic electric field to convert the polarization direction of incident light, the magnitude of the applied electric field is gradually reduced toward the edge of the modulation medium. By decreasing the amount, it is possible to obtain an optical modulator that has better temperature characteristics than conventional ones and is stable against wavelength fluctuations of incident light.
なお、本発明に用いる変調媒体およびその形
状、電極形状、印加電界を変化させる手段および
その印加電界の変化のさせ方等は上記の実施例に
限定されるものではない。例えば、変調媒体とし
ては、屈折率楕円体の回転を生じせしめる電気光
学定数を有するものであればよく、例えば、タン
タル酸リチウムとニオブ酸リチウムの混晶を用い
ることができる。また、印加電界を変化させる手
段としては、抵抗値がほぼ連続的に変化している
抵抗体やそれぞれ異なる容量値を持つ容量を介し
て一定の電圧を印加することも可能である。ま
た、電界の変化のさせ方は直線状、放物線状等
種々の形で変化させても温度特性は従来よりも大
きく改善される。なお、本発明において、電界の
変化のさせ方を端に行くに従つて単調に減少させ
ないで任意の関数形で変化させることによつて所
望の温度特性または入射光の波長に対する特性を
得ることができる。インターデイジタル電極型弾
性表面波トランスジユーサの電極に重みづけを行
なうことによつて周波数特性を変えることができ
ることが知られているが、それと同様に本発明に
よる光変調器において、印加電界の大きさに分布
をつけることによつて温度特性または入射光の波
長に対する特性を変えることができる。 Note that the modulation medium used in the present invention, its shape, electrode shape, means for changing the applied electric field, method of changing the applied electric field, etc. are not limited to the above embodiments. For example, the modulation medium may be anything that has an electro-optic constant that causes rotation of the index ellipsoid, and for example, a mixed crystal of lithium tantalate and lithium niobate may be used. Further, as means for changing the applied electric field, it is also possible to apply a constant voltage through a resistor whose resistance value changes almost continuously or through capacitors each having a different capacitance value. Furthermore, even if the electric field is varied in various ways, such as linearly or parabolically, the temperature characteristics can be greatly improved compared to the conventional method. In addition, in the present invention, desired temperature characteristics or characteristics with respect to the wavelength of incident light can be obtained by changing the electric field in an arbitrary functional form rather than decreasing monotonically toward the end. can. It is known that the frequency characteristics of an interdigital electrode type surface acoustic wave transducer can be changed by weighting the electrodes. By adding a distribution to the wavelength, it is possible to change the temperature characteristics or the characteristics with respect to the wavelength of the incident light.
なお、本発明において、変調媒体の厚さを小さ
くし、変調媒体を薄片化することによつて、変調
に必要な電圧を低下せしめ、より高い変調効率を
得ることができる。上記の薄片化の手段として
は、変調媒体を機械的に研磨して薄くする方法、
蒸着、スパツタ等により他の基板上に変調媒体を
設置する方法、変調媒体の表面に金属等を拡散せ
しめ、そこに光波を通過せしめる方法、他の基板
上に変調媒体薄膜を結晶成長させる方法等があ
る。上記方法によつて変調媒体薄膜の厚さを数十
ミクロン以下にした場合には、通常、薄膜光導波
路と呼ばれ、光波が該薄膜中に閉じ込められて進
行することが知られている。このとき、光波は複
数個の伝搬モードに分離されるので、対象とする
伝搬モードの等価的な屈折率を考慮して光変調器
を設計しなければならない。 In the present invention, by reducing the thickness of the modulation medium and making the modulation medium thin, the voltage required for modulation can be lowered and higher modulation efficiency can be obtained. The above-mentioned means of thinning include a method of mechanically polishing the modulation medium to make it thin;
Methods of installing a modulation medium on another substrate by vapor deposition, sputtering, etc., methods of diffusing metal, etc. on the surface of the modulation medium and allowing light waves to pass through it, methods of growing crystals of a thin film of the modulation medium on another substrate, etc. There is. When the thickness of the modulation medium thin film is reduced to several tens of microns or less using the above method, it is usually called a thin film optical waveguide, and it is known that light waves propagate while being confined within the thin film. At this time, since the light wave is separated into a plurality of propagation modes, the optical modulator must be designed in consideration of the equivalent refractive index of the target propagation mode.
第１図は従来の光変調器を示す斜視図、第２図
は従来の光変調器の温度特性を示す図、第３図、
第５図は本発明による光変調器の実施例を示す
図、第４図は本発明による光変調器の温度特性の
一例を示す図である。図において１，１１，２１
はタンタル酸リチウム結晶、２，２２はインター
デイジタル電極、３，２３は信号発生器、４，１
４，２４は入射光、５，１５，２５は出射光、
６，１６，２６は検光子、７，１７，２７は出力
光である。
Fig. 1 is a perspective view showing a conventional optical modulator, Fig. 2 is a diagram showing temperature characteristics of a conventional optical modulator, Fig. 3,
FIG. 5 is a diagram showing an embodiment of the optical modulator according to the invention, and FIG. 4 is a diagram showing an example of the temperature characteristics of the optical modulator according to the invention. 1, 11, 21 in the figure
is a lithium tantalate crystal, 2, 22 is an interdigital electrode, 3, 23 is a signal generator, 4, 1
4, 24 are incident lights, 5, 15, 25 are output lights,
6, 16, and 26 are analyzers, and 7, 17, and 27 are output lights.
Claims (1)
の光透過方向に周期的な電界を印加する手段とを
含み、該透過光の偏光成分の少なくとも一部を該
偏光成分と直交する偏光成分に変換して光を変調
する光変調器において、前記光変調媒体の少なく
とも一部で前記印加電界の大きさが光透過方向に
沿つて順次変化していることを特徴とする光変調
器。 ２ 光変調媒体の少なくとも一部で、印加する電
界の大きさを該媒体の光の入出射端に近づくに従
つて減少させた特許請求の範囲第１項記載の光変
調器。[Scope of Claims] 1. A light modulating medium having an electro-optic effect, and means for applying a periodic electric field in the light transmission direction of the medium, and converting at least a part of the polarized light component of the transmitted light into the polarized light component. An optical modulator that modulates light by converting it into a polarization component perpendicular to the polarization component, characterized in that the magnitude of the applied electric field changes sequentially along the light transmission direction in at least a portion of the optical modulation medium. light modulator. 2. The optical modulator according to claim 1, wherein the magnitude of the electric field applied to at least a portion of the optical modulation medium decreases as it approaches the light input/output end of the medium.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7602678A JPS554018A (en) | 1978-06-22 | 1978-06-22 | Light modulator |
| US06/261,081 US4387343A (en) | 1978-06-22 | 1981-05-06 | Electrooptic light modulator including weighted interdigital electrodes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7602678A JPS554018A (en) | 1978-06-22 | 1978-06-22 | Light modulator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS554018A JPS554018A (en) | 1980-01-12 |
| JPS6150288B2 true JPS6150288B2 (en) | 1986-11-04 |
Family
ID=13593303
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7602678A Granted JPS554018A (en) | 1978-06-22 | 1978-06-22 | Light modulator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS554018A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4387343A (en) * | 1978-06-22 | 1983-06-07 | Nippon Electric Co., Ltd. | Electrooptic light modulator including weighted interdigital electrodes |
| JPS5732734U (en) * | 1980-07-29 | 1982-02-20 | ||
| JPS62113154U (en) * | 1986-01-08 | 1987-07-18 |
-
1978
- 1978-06-22 JP JP7602678A patent/JPS554018A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS554018A (en) | 1980-01-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Chang | Noncollinear acousto‐optic filter with large angular aperture | |
| US5153770A (en) | Total internal reflection electro-optic modulator | |
| US3874782A (en) | Light-guiding switch, modulator and deflector employing antisotropic substrate | |
| Yamada | Electrically induced Bragg-diffraction grating composed of periodically inverted domains in lithium niobate crystals and its application devices | |
| US4866406A (en) | Wide-band optical modulator | |
| US6353690B1 (en) | Electrically adjustable diffraction grating | |
| US4243300A (en) | Large aperture phased element modulator/antenna | |
| JPH08122718A (en) | Macromolecular-waveguide type te-tm mode converter | |
| US4196977A (en) | Electro-optic modulator/deflector | |
| US3930718A (en) | Electro-optic modulator | |
| US4607909A (en) | Method for modulating a carrier wave | |
| JPS6157613B2 (en) | ||
| De Barros et al. | High-speed electro-optic diffraction modulator for baseband operation | |
| US20050002101A1 (en) | Dynamically controllable light modulator using phase diffraction grating and display using the same | |
| EP0100418B1 (en) | Opto-optical light deflector | |
| JPS6150288B2 (en) | ||
| JPS6149649B2 (en) | ||
| US4387343A (en) | Electrooptic light modulator including weighted interdigital electrodes | |
| EP1403692A1 (en) | Electro-optic devices | |
| US4299449A (en) | Acoustooptic modulator | |
| JPS6212487B2 (en) | ||
| JPS6150289B2 (en) | ||
| JPH05297332A (en) | Optical modulator | |
| JPS6211329B2 (en) | ||
| JP2758540B2 (en) | Light modulation element and light modulation device using the same |