JP3412706B2

JP3412706B2 - Optical multiplexer / demultiplexer

Info

Publication number: JP3412706B2
Application number: JP3740094A
Authority: JP
Inventors: 正憲飯田; 宏之朝倉
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1993-03-10
Filing date: 1994-03-08
Publication date: 2003-06-03
Anticipated expiration: 2018-06-03
Also published as: JPH06317705A

Description

DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【産業上の利用分野】本発明は、分光器や波長多重光通
信システムに用いる回折素子及びそれを用いた光合分波
装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffractive element used in a spectroscope or a wavelength division multiplexing optical communication system, and an optical multiplexing / demultiplexing apparatus using the same.

【０００２】[0002]

【従来の技術】近年、回折素子やそれを用いた光合分波
装置は、波長多重光通信システムのキーデバイスとして
様々な形態が提案され検討されている。特に、高密度波
長多重光通信では、用いられる光の波長間隔が狭く、多
数の波長が多重されるため、回折素子を用いた光合分波
器が有望視されている。しかしながら、広い波長範囲に
わたって高い回折効率を有する回折素子は一般にないの
が現状である。2. Description of the Related Art In recent years, various forms of a diffractive element and an optical multiplexer / demultiplexer using the same have been proposed and studied as a key device of a wavelength division multiplexing optical communication system. In particular, in high-density wavelength division multiplexing optical communication, since the wavelength interval of light used is narrow and a large number of wavelengths are multiplexed, an optical multiplexer / demultiplexer using a diffraction element is expected to be promising. However, at present, there is generally no diffraction element having high diffraction efficiency over a wide wavelength range.

【０００３】図９は、反射型の回折素子で、格子溝の断
面形状が鋸歯状であるものについての回折効率の波長依
存性を示している。図９は、R.Petit:Electromagnetic
Theory of Gratings <Springer-Verlag Berlin Heidelb
erg New York 1980>. Chap.6, p.164の文献より引用し
ている。図９において、ＴＥ偏光は、回折素子に入射す
る光のうち、偏光方向が格子溝方向に平行な成分であ
り、ＴＭ偏光は、回折素子に入射する光のうち、偏光方
向が格子溝方向に垂直な成分である。図９から分かるよ
うに、使用される入射光の波長、あるいは入射光の波長
と格子間隔との比、及び入射光の偏光方向により、回折
効率が大きく影響される。図９から、回折効率が高く、
かつＴＥ偏光とＴＭ偏光の回折効率の差異が小さい波長
範囲は非常に狭いことがわかる。例えば、回折効率が８
５％以上で両偏光の回折効率の差異が１０％以内の波長
範囲は、格子溝間隔を０.８μｍの回折格子で換算した
場合、４０ｎｍ以下である。FIG. 9 shows the wavelength dependence of the diffraction efficiency of a reflection type diffraction element having a grating groove having a sawtooth cross section. Fig. 9 shows R. Petit: Electromagnetic
Theory of Gratings <Springer-Verlag Berlin Heidelb
erg New York 1980>. Cited from the text of Chap. 6, p. 164. In FIG. 9, TE polarized light is a component whose polarization direction is parallel to the grating groove direction of light incident on the diffraction element, and TM polarized light is a component whose polarization direction is parallel to the grating groove direction of light incident on the diffraction element. The vertical component. As can be seen from FIG. 9, the diffraction efficiency is greatly affected by the wavelength of the incident light used, the ratio of the wavelength of the incident light to the grating interval, and the polarization direction of the incident light. From FIG. 9, the diffraction efficiency is high,
Further, it can be seen that the wavelength range in which the difference in the diffraction efficiency between the TE polarized light and the TM polarized light is small is very narrow. For example, if the diffraction efficiency is 8
The wavelength range where the difference between the diffraction efficiencies of the two polarized lights is 5% or more and the difference between the diffraction efficiencies of the two polarized lights is 10% or less is 40 nm or less when the grating groove interval is converted by a 0.8 μm diffraction grating.

【０００４】そこで、使用される光の波長を調整するた
めに、このような回折素子の回折格子の格子溝の上に透
光材を設ける提案もなされている。図１０はその一例を
示している。基板５１上に、格子溝を刻印した反射型回
折基板５２が形成され、その上に透光材５３が形成され
ている。[0004] In order to adjust the wavelength of the light used, a proposal has been made to provide a light transmitting material on the grating groove of the diffraction grating of such a diffraction element. FIG. 10 shows an example. On a substrate 51, a reflection type diffraction substrate 52 having a grating groove stamped thereon is formed, and a light transmitting material 53 is formed thereon.

【０００５】このような構成の回折素子に於いては、光
は回折素子表面５４より入射し、透過材５３を介して反
射型回折基板５２の回折格子により回折される。回折さ
れた光は、再び透過材５３を介して回折格子表面５４よ
り出射する。透過材５３の屈折率をｎとすれば、透過材
５３中の光は、等価的に１／ｎの波長を有することにな
る。従って、透光材５３の屈折率を調整することによ
り、入射光の回折時の波長を変化させることができるの
で、図９に示される回折効率の高い波長帯で光を回折さ
せることができる（例えば、特開昭６２−６１００２号
公報参照）。In the diffractive element having such a structure, light enters from the diffractive element surface 54 and is diffracted by the diffraction grating of the reflective diffractive substrate 52 via the transmitting material 53. The diffracted light exits from the diffraction grating surface 54 again through the transmitting material 53. Assuming that the refractive index of the transmitting material 53 is n, the light in the transmitting material 53 has a wavelength of 1 / n equivalently. Therefore, by adjusting the refractive index of the light transmitting material 53, the wavelength at the time of diffracting the incident light can be changed, so that the light can be diffracted in the wavelength band having a high diffraction efficiency shown in FIG. 9 ( For example, see JP-A-62-61002).

【０００６】また、分散する波長領域が異なる２つの回
折格子を組み合わせて用いることにより、２種類の波長
帯で光合分波を行う装置も提案されている。例えば、特
開平４−２８２６０３号公報には、図１１に示すような
光合分波器が記載されている。入力ファイバ６１からの
波長多重された光は、レンズ６３を介して第１の回折格
子６４に入射する。波長多重された光のうち、短波長領
域の光λ_a〜λ_cは、第１の回折格子６４によって波長分
散され、レンズ６３を介して、各々、出力ファイバ６２
_a〜６２_cに結合する。一方、長波長領域の光λ_d〜λ
_fは、第１の回折格子６４では波長分散されずに全反射
される。全反射された光は、第２の回折格子６５で波長
分散されて第１の回折格子６４に入射する。入射した光
は第１の回折格子６４で再び全反射され、レンズ６３を
介して、各々、出力ファイバ６２ｃ〜６２ｆに結合す
る。There has also been proposed an apparatus for performing optical multiplexing / demultiplexing in two kinds of wavelength bands by using a combination of two diffraction gratings having different wavelength regions to be dispersed. For example, Japanese Patent Application Laid-Open No. 4-282603 describes an optical multiplexer / demultiplexer as shown in FIG. The wavelength-multiplexed light from the input fiber 61 enters the first diffraction grating 64 via the lens 63. Of the wavelength-multiplexed light, lights λ _{a to} λ _{c in} the short wavelength region are wavelength-dispersed by the first diffraction grating 64, and each of the output fibers 62 through the lens 63.
to bind to _{a ~62} _c. On the other hand, light λ _{d to} λ in the long wavelength region
_f is totally reflected by the first diffraction grating 64 without wavelength dispersion. The light totally reflected is wavelength-dispersed by the second diffraction grating 65 and enters the first diffraction grating 64. The incident light is totally reflected again by the first diffraction grating 64, and is coupled to the output fibers 62c to 62f via the lens 63, respectively.

【０００７】[0007]

【発明が解決しようとする課題】しかしながら、上述の
従来技術においては、図１０のものにおいては、回折素
子表面３４から透過材３３を介して光が入射するため、
入射光の分光特性を長波長側に調整することはできる
が、反射型回折基板３２の本来持つ分光特性自体は、透
光材３３を設けることによって失われてしまう。また、
さらに広範囲な波長範囲、例えば０.８μｍ、１.３μ
ｍ、１.５５μｍ帯の光に対しても良好な分光特性を得
るためには、各々の波長帯に適した屈折率を有する異な
った透光材３３を配した回折素子を、別々に用意しなけ
ればならないといった問題点を有している。また、上述
の従来技術の図１１のものにおいても、やはり、２種類
の回折格子６４及び６５を用意しなければならない。回
折格子は高価であり、１つの装置に２つの回折格子を用
いることは装置全体の価格を低減する妨げとなってい
る。However, in the prior art described above, in FIG. 10, since light is incident from the diffractive element surface 34 via the transmitting material 33,
Although the spectral characteristic of the incident light can be adjusted to the longer wavelength side, the spectral characteristic itself of the reflective diffraction substrate 32 is lost by providing the light transmitting material 33. Also,
Wider wavelength range, for example, 0.8 μm, 1.3 μm
In order to obtain good spectral characteristics even for light in the 1.55 μm band, diffractive elements having different translucent materials 33 each having a refractive index suitable for each wavelength band are separately prepared. There is a problem that must be. Also in the prior art shown in FIG. 11, two types of diffraction gratings 64 and 65 must be prepared. Diffraction gratings are expensive, and the use of two diffraction gratings in one device hinders the cost of the entire device.

【０００８】また、特に、図１１のもののような場合に
は、２つの回折格子の配置を正確に調節するための装置
が必要となり、装置は更に高価なものとならざるを得な
い。In particular, in the case of FIG. 11, a device for precisely adjusting the arrangement of the two diffraction gratings is required, and the device must be more expensive.

【０００９】本発明は、上記課題を解決するためにな
されたものであり、その目的とするところは、１つの素
子で複数の波長帯に対して使用することができる回折素
子の効果を用いた光合分波装置を提供することにある。The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a diffractive element that can be used for a plurality of wavelength bands with one element.
An object of the present invention is to provide an optical multiplexing / demultiplexing device using the effect of a child .

【００１０】[0010]

【課題を解決するための手段】第１の本発明は、第１及
び第２の面を有する透明基板と、該第１の面に刻印され
た周期的な溝と、該周期的な溝が刻印された該第１の面
上に設けられた反射膜とから回折格子が形成され、該反
射膜が設けられた該第１の面に対応した第１の入射面
と、該第２の面に対応した第２の入射面を有する回折素
子と、該回折素子の該第１の入射面に光を入射させる第
１の光入力手段と、該第１の入射面に入射して該回折素
子によって回折された光を受け取る第１の受光手段と、
該第１の入射面に入射して該回折素子によって反射され
た光を受け取り、該回折素子の該第２の入射面に入射さ
せる第２の光入力手段と、該第２の入射面に入射して該
回折素子によって回折された光を受け取る第２の受光手
段とを備え、前記第１及び第２の光入力手段は、各々、
前記第１の入射面及び前記第２の入射面に入射する前記
光の入射角θが、リトロー角θＬとして、 θＬ−５°≦θ≦θＬ十５° であるように該光を入射させ、該第１の入射面に入射し
て回折された該光の波長λ１、及び前記反射された光の
波長λ２（但しλ２＞λ１）は、前記透明基板の屈折率
がｎ、前記溝の間隔（ピッチ）がｄであるとき、 λ２−λ１／２＞ｄｎ＝λ２／λ１の関係をみたしていることを特徴とする光合分波装置で
ある。According to a first aspect of the present invention, there is provided a transparent substrate having first and second surfaces, a periodic groove imprinted on the first surface, and a periodic groove formed on the first surface. A first entrance surface corresponding to the first surface on which the reflection film is provided, and a second entrance surface, wherein a diffraction grating is formed from the engraved reflection film provided on the first surface; A diffractive element having a second incident surface corresponding to the above, a first light input means for causing light to enter the first incident surface of the diffractive element, and a diffractive element incident on the first incident surface First light receiving means for receiving the light diffracted by
Second light input means for receiving light incident on the first incident surface and reflected by the diffractive element and impinging the light on the second incident surface of the diffractive element; and impinging on the second incident surface And second light receiving means for receiving the light diffracted by the diffractive element, wherein the first and second light input means each include:
The light incident on the first incident surface and the second incident surface
The light is incident so that the incident angle θ of the light is the Littrow angle θL such that θL−5 ° ≦ θ ≦ θL15 ° , and is incident on the first incident surface.
Wavelength λ1 of the diffracted light and the reflected light
The wavelength λ2 (where λ2> λ1) is the refractive index of the transparent substrate.
Is n and the interval (pitch) between the grooves is d, the relationship of λ2-λ1 / 2> dn = λ2 / λ1 is satisfied .

【００１１】第２の本発明は、第１及び第２の面を有す
る透明基板と、該策１の面に刻印された周期的な溝と、
該周期的な溝が刻印された該第１の面上に設けられた反
射膜とから回折格子が形成され、前記反射膜の上に設け
られた透明保護層を有し、該反射膜が設けられた該第１
の面に対応した第１の入射面と、該第２の面に対応した
第２の入射面を有する回折素子と、該回折素子の該第１
の入射面に光を入射させる第１の光入力手段と、該第１
の入射面に入射して該回折素子によって回折された光を
受け取る第１の受光手段と、該第１の入射面に入射して
該回折素子によって反射された光を受け取り、該回折素
子の該第２の入射面に入射させる第２の光入力手段と、
該第２の入射面に入射して該回折素子によって回折され
た光を受け取る第２の受光手段とを備え、前記第１及び
第２の光入力手段は、各々、前記第１の入射面及び前記
第２の入射面に入射する前記光の入射角θが、リトロー
角θＬとして、 θＬ−５°≦θ≦θＬ＋５° であるように該光を入射させ、該第１の入射面に入射し
て回折された該光の波長λ１、及び前記反射された光の
波長λ２（但しλ２＞λ１）は、前記透明基板の屈折率
がｎ、前記透明保護層の屈折率がｎ１、前記溝の間隔
（ピッチ）がｄであるとき、 λ２−λ１／２＞ｎｌ・ｄｎ＝ｎｌ・λ２／λ１の関係をみたしていることを特徴とする光合分波装置で
ある。 A second aspect of the present invention has first and second surfaces.
A transparent substrate, a periodic groove imprinted on the surface of the measure 1,
An anti-recess provided on the first surface on which the periodic groove is imprinted
A diffraction grating is formed from the reflective film and provided on the reflective film.
The transparent protective layer, and the first
A first incident surface corresponding to the surface of
A diffractive element having a second incident surface;
First light input means for making light incident on an incident surface of
Light incident on the incident surface of the
First light receiving means for receiving the light, and light incident on the first light incident surface
Receiving light reflected by the diffractive element;
Second light input means for entering the second incident surface of the child;
Incident on the second incident surface and diffracted by the diffraction element
And a second light receiving means for receiving the first light and the second light.
The second light input means respectively comprises the first incident surface and the
The incident angle θ of the light incident on the second incident surface is Littrow.
The light is incident so that the angle θL is θL−5 ° ≦ θ ≦ θL + 5 ° , and is incident on the first incident surface.
Wavelength λ1 of the diffracted light and the reflected light
The wavelength λ2 (where λ2> λ1) is the refractive index of the transparent substrate.
Is n, the refractive index of the transparent protective layer is n1, and the distance between the grooves is
When (pitch) is d, the optical multiplexing / demultiplexing device is characterized in that a relationship of λ2−λ1 / 2> nl · dn = nl · λ2 / λ1 is satisfied.
is there.

【００１２】第３の本発明は、前記第２の面には、反射
防止膜が形成されていることを特徴とする第１又は第２
の本発明の光合分波装置である。 According to a third aspect of the present invention, the second surface has a reflection surface.
A first or a second film, wherein a first protective film is formed.
Of the present invention.

【００１３】第４の本発明は、前記回折素子の前記反射
膜の形状は、前記溝に平行な所定の軸を中心とした１８
０度の回転に対して実質的に対称であることを特徴とす
る第１又は第２の本発明の光合分波装置である。 According to a fourth aspect of the present invention, there is provided the above-mentioned diffraction element,
The shape of the film is 18 around a predetermined axis parallel to the groove.
Characterized by being substantially symmetrical with respect to 0-degree rotation
A first or second optical multiplexer / demultiplexer according to the present invention.

【００１４】第５の本発明は、前記回折素子の前記第１
の入射面に関してリトロー配置された第１のレンズと、
該回折素子の前記第２の入射面に関してリトロー配置さ
れた第２のレンズと、を備えていることを特徴とする第
１又は第２の本発明の光合分波装置である。 According to a fifth aspect of the present invention, there is provided the diffraction element, wherein
A first lens Littrow arranged with respect to the entrance surface of
Littrow arrangement with respect to the second entrance surface of the diffraction element
A second lens,
An optical multiplexer / demultiplexer according to the first or second aspect of the present invention.

【００１５】第６の本発明は、第１及び第２の面を有す
る透明基板と、該第１の既に刻印された周期的な溝と、
該周期的な溝が刻印された該第１の面上に設けられた反
射膜とから回折格子が形成され、該反射膜が設けられた
該第１の面に対応した第１の入射面と、該第２の面に対
応した第２の入射面を有する回折素子と、該回折素子に
光を入射させる光入力手段と、該回折素子によって回折
された光を、該回折光の波長毎に受け取る受光手段と、
前記光入力手段からの光を前記回折素子の前記第１の入
射面に入射させる第１の配置と、該光入力手段からの光
を前記回折素子の前記第２の入射面に入射させる第２の
配置と、を可能とするために、該回折素子、該光入力手
段、及び該受光手段のうちの少なくとも１つの位置及び
／又は方向を変更するための配置手段とを備え、前記第
１及び第２の光入力手段は、各々、前記第１の入射面及
び前記第２の入射面に入射する前記光の入射角θが、リ
トロー角θＬとして、 θＬ−５°≦θ≦θＬ＋５° であるように該光を入射させ、該第１の入射面に入射し
て回折された該光の波長λ１、及び前記反射された光の
波長λ２（但しλ２＞λ１）は、前記透明基板の屈折率
がｎ、前記溝の間隔（ピッチ）がｄであるとき、 λ２−λ１／２＞ｄｎ＝λ２／λ１の関係をみたしていることを特徴とする光合分波装置で
ある。 A sixth aspect of the present invention has a first and a second surface.
A transparent substrate, the first already engraved periodic groove,
An anti-recess provided on the first surface on which the periodic groove is imprinted
A diffraction grating was formed from the reflective film and the reflective film was provided.
A first incident surface corresponding to the first surface and a second incident surface corresponding to the second surface;
A diffractive element having a corresponding second incident surface;
Light input means for inputting light and diffraction by the diffraction element
Has been light, a light receiving means for receiving each wavelength of the diffraction light,
The light from the light input means is transmitted to the first input of the diffraction element.
A first arrangement for incidence on the launch surface, and light from the light input means
Is incident on the second incident surface of the diffraction element.
The diffraction element, the light input means,
A step, and the position of at least one of said light receiving means;
And / or arrangement means for changing the direction.
The first and second light input means are respectively provided on the first incident surface and the first incident surface.
And the incident angle θ of the light incident on the second incident surface is
The light is made incident such that θL−5 ° ≦ θ ≦ θL + 5 ° as the trolley angle θL, and is incident on the first incident surface.
Wavelength λ1 of the diffracted light and the reflected light
The wavelength λ2 (where λ2> λ1) is the refractive index of the transparent substrate.
Is n and the interval (pitch) between the grooves is d, the relationship of λ2-λ1 / 2> dn = λ2 / λ1 is satisfied.
is there.

【００１６】第７の本発明は、第１及び第２の面を有す
る透明基板と、該第１の面に刻印された周期的な溝と、
該周期的な溝が刻印された該第１の面上に設けられた反
射膜とから回折格子が形成され、前記反射膜の上に設け
られた透明保護層を有し、該反射膜が設けられた該第１
の面に対応した第１の入射面と、該第２の面に対応した
第２の入射面を有する回折素子と、該回折素子に光を入
射させる光入力手段と、該回折素子によって回折された
光を、該回折光の波長毎に受け取る受光手段と、前記光
入力手段からの光を前記回折素子の前記第１の入射面に
入射させる第１の配置と、該光入力手段からの光を前記
回折素子の前記第２の入射面に入射させる第２の配置
と、を可能とするために、該回折素子、該光入力手段、
及び該受光手段のうちの少なくとも１つの位置及び／又
は方向を変更するための制御手段とを備え、前記第１及
び第２の光入力手段は、各々、前記第１の入射面及び前
記第２の入射面に入射する前記光の入射角θが、リトロ
ー角θＬとして、 θＬ−５°≦θ≦θＬ十５° であるように該光を入射させ、該第１の入射面に入射し
て回折された該光の波長λ１、及び前記反射された光の
波長λ２（但しλ２＞λ１）は、前記透明基板の屈折率
がｎ、前記透明保護層の屈折率がｎ１、前記溝の間隔
（ピッチ）がｄであるとき、 λ２−λ１／２＞ｎ１・ｄｎ＝ｎｌ・λ２／λ１の関係をみたしていることを特徴とする光合分波装置で
ある。 A seventh aspect of the present invention has first and second surfaces.
A transparent substrate, a periodic groove imprinted on the first surface,
An anti-recess provided on the first surface on which the periodic groove is imprinted
A diffraction grating is formed from the reflective film and provided on the reflective film.
The transparent protective layer, and the first
A first incident surface corresponding to the surface of
A diffraction element having a second incident surface, and light incident on the diffraction element.
Light input means for emitting light, diffracted by the diffraction element
Light receiving means for receiving light for each wavelength of the diffracted light;
Light from the input means is applied to the first incident surface of the diffraction element.
A first arrangement for incidence, and light from the light input means
A second arrangement for making the light incident on the second incident surface of the diffraction element
And the diffractive element, the light input means,
And the position of at least one of said light receiving means and / or
Is provided with control means for changing the direction.
And a second light input means, respectively, the first input surface and the front
The incident angle θ of the light incident on the second incident surface is
The light is incident so that the angle θL is θL−5 ° ≦ θ ≦ θL15 ° , and is incident on the first incident surface.
Wavelength λ1 of the diffracted light and the reflected light
The wavelength λ2 (where λ2> λ1) is the refractive index of the transparent substrate.
Is n, the refractive index of the transparent protective layer is n1, and the distance between the grooves is
When the (pitch) is d, the optical multiplexing / demultiplexing device is characterized in that a relationship of λ2−λ1 / 2> n1 · dn = nl · λ2 / λ1 is satisfied.
is there.

【００１７】第８の本発明は、前記光入力手段からの光
をコリメートし、前記回折素子によって反射された光を
前記受光手段に集光するためのレンズを備えており、前
記第１の配置は、該回折素子の前記第１の入射面に関す
るリトロー配置であり、前記第２の配置は、該回折素子
の前記第２の入射面に関するリトロー配置であることを
特徴とする第６又は第７の本発明の光合分波装置であ
る。 According to an eighth aspect of the present invention, the light from the light input means is provided.
And collimates the light reflected by the diffraction element.
A lens for condensing light on the light receiving means;
The first arrangement relates to the first incident surface of the diffraction element.
Wherein the second arrangement is a diffraction element
Littrow arrangement with respect to the second incident surface of
A sixth or seventh optical multiplexer / demultiplexer according to the present invention, wherein
You.

【００１８】第９の本発明は、前記配置手段は、前記回
折素子を回転させる機構を備え、該回折素子を回転する
ことによって、前記第１及び第２の配置の−方から他方
へ配置替えを行うことを特徴とする第６又は第７の本発
明の光合分波装置である。 According to a ninth aspect of the present invention, the disposing means includes the
A mechanism for rotating the folding element is provided, and the diffraction element is rotated.
By doing so, the other of the first and second arrangements
The sixth or seventh aspect of the present invention, wherein the rearrangement is performed.
It is a light optical multiplexer / demultiplexer.

【００１９】第１０の本発明は、前記第２の面には、反
射防止膜が形成されていることを特徴とする第６又は第
７の本発明の光合分波装置である。 According to a tenth aspect of the present invention, the second surface has
A sixth or seventh aspect, wherein an anti-irradiation film is formed.
7 is an optical multiplexer / demultiplexer according to the present invention.

【００２０】第１１の本発明は、前記回折素子の前記反
射膜の形状は、前記溝に平行な軸を中心とした１８０度
の回転に対して実質的に対称であることを特徴とする第
６又は第７の本発明の光合分波装置である。 According to an eleventh aspect of the present invention, there is provided the diffraction element,
The shape of the film is 180 degrees around an axis parallel to the groove.
Characterized by being substantially symmetrical with respect to the rotation of
A sixth or seventh optical multiplexer / demultiplexer according to the present invention.

【００２１】[0021]

【００２２】[0022]

【００２３】[0023]

【００２４】[0024]

【００２５】[0025]

【００２６】[0026]

【００２７】[0027]

【００２８】[0028]

【００２９】[0029]

【００３０】[0030]

【００３１】[0031]

【００３２】[0032]

【００３３】[0033]

【００３４】[0034]

【００３５】[0035]

【００３６】[0036]

【作用】上述の構成により、本発明の回折素子は、回折
素子の第１の入射面（反射膜が設けられた側：表の面）
に入射して回折する光と、第２の入射面（反射防止膜が
設けられた面：裏の面）に入射し、透明基板を介して回
折する光との、２つの異なる波長帯の光を波長分散す
る。反射膜を、「表」と「裏」とで対称な形状に形成す
ることにより、第１及び第２の入射面に入射する各々の
光は、実質的に同一の分光特性（回折効率等）で波長分
散される。透明基板の屈折率を変化させることによっ
て、第２の入射面に入射して回折される光の波長を調整
できる。With the above arrangement, the diffractive element of the present invention has the first incident surface (the side on which the reflective film is provided: the front surface) of the diffractive element.
Light of two different wavelength bands: light that is incident and diffracted on the second incident surface (the surface on which the antireflection film is provided: the back surface) and is diffracted through the transparent substrate. Is wavelength-dispersed. By forming the reflection film in a symmetrical shape between the “front” and “back”, each light incident on the first and second incident surfaces has substantially the same spectral characteristics (diffraction efficiency, etc.). Wavelength dispersion. By changing the refractive index of the transparent substrate, the wavelength of the light that is incident on the second incident surface and diffracted can be adjusted.

【００３７】透明基板（及び／又は透明保護層）が、異
なる屈折率を持つ複数の部分を有している場合には、更
に異なる波長帯の光をも回折させて波長分散できる。When the transparent substrate (and / or the transparent protective layer) has a plurality of portions having different refractive indices, light in different wavelength bands can be further diffracted and wavelength-dispersed.

【００３８】波長多重された光（λ₁及びλ₂）が第１の
入射面に入力された場合、波長等の条件を適切に選んで
於くことにより、一方の波長帯（λ₂）の光は、回折さ
れずに全反射される。When the wavelength-multiplexed light (λ ₁ and λ ₂ ) is input to the first incident surface, the condition of one wavelength band (λ ₂ ) can be selected by appropriately selecting conditions such as the wavelength. Light is totally reflected without being diffracted.

【００３９】本発明の回折素子を用いた光合分波装置に
よれば、第１の光入力装置から上記の第１の入射面に入
射した波長多重光は、ある波長帯（λ₁）の光が波長分
散され、第１の受光装置で受け取られる。他の波長帯の
光は回折されず、一定の条件をみたす場合には反射膜に
よって全反射される。全反射された光（λ₂）は、回折
素子の第２の入射面に導かれ、透明基板を介して同様に
回折される。第２の入射面に入射して波長分散された光
は第２の受光装置で受け取られる。According to the optical multiplexer / demultiplexer using the diffraction element of the present invention, the wavelength division multiplexed light incident on the first incident surface from the first optical input device is a light of a certain wavelength band (λ ₁ ). Are wavelength-dispersed and received by the first light receiving device. Light in other wavelength bands is not diffracted and is totally reflected by the reflective film when certain conditions are satisfied. The totally reflected light (λ ₂ ) is guided to the second incident surface of the diffraction element, and is similarly diffracted through the transparent substrate. The wavelength-dispersed light that has entered the second incident surface is received by the second light receiving device.

【００４０】本発明の回折素子を用いた他の光合分波装
置は、回折素子、光入力装置、受光装置のうち少なくと
も１つの位置及び／又は方向を変える配置機構を設ける
ことにより、回折すべき波長に応じて回折素子の第１又
は第２の入射面を使い分けることにより、複数の波長帯
の光に対して波長分散を行う。Another optical multiplexer / demultiplexer using the diffraction element of the present invention should diffract by providing an arrangement mechanism for changing the position and / or direction of at least one of the diffraction element, the light input device, and the light receiving device. By selectively using the first or second incident surface of the diffraction element according to the wavelength, wavelength dispersion is performed on light in a plurality of wavelength bands.

【００４１】特に、回折素子を回転するための回転機構
部を設けた場合には、所望の波長の光が受光装置に集光
するように、回転機後部により回折格子の角度を調節す
る。特に波長多重光のうち、長波長側（λ₂）の光に対
して波長分散を行う場合は、回折素子の第２の入射面
（裏面）に光が入射するように、回転機構部により回折
素子を裏返すように回転させ、受光装置に所望の波長の
光が集光するように角度を調整する。In particular, when a rotation mechanism for rotating the diffraction element is provided, the angle of the diffraction grating is adjusted by the rear part of the rotating machine so that light of a desired wavelength is focused on the light receiving device. In particular, when wavelength dispersion is performed on light on the long wavelength side (λ ₂ ) of wavelength multiplexed light, the light is diffracted by the rotation mechanism so that the light is incident on the second incident surface (back surface) of the diffraction element. The element is rotated upside down, and the angle is adjusted so that light of a desired wavelength is collected on the light receiving device.

【００４２】[0042]

【実施例】以下に、本発明を実施例について、図面を参
照しながら説明する。Embodiments of the present invention will be described below with reference to the drawings.

【００４３】（実施例１）図１（ａ）は本発明の第１の
実施例における回折素子３０の構成を示すものである。
本実施例に於ける回折素子は、透明な基板２の一方の表
面３１に、ピッチｄで格子溝が刻印され、その上に反射
膜１が形成されている。反射膜１は、反射膜としての特
性を有しつつ、膜厚は十分に薄く形成される。例えば、
反射膜１は、アルミニウムなどの反射率の高い金属の
膜、あるいは誘電体多層膜を格子表面３１に設けること
により形成できる。反射膜１は、膜厚が５０〜３００ｎ
ｍ、好ましくは１００ｎｍ程度であれば格子溝の形状を
損なうことなく均一に形成することができる。透明基板
２は、代表的にはガラスが用いられ、使用する光の波長
に対して透光性を有する基板材料であればよい。以下、
この明細書に於いて「透明」というときには、使用する
光の波長に対して透光性を有することを意味する。(Embodiment 1) FIG. 1A shows the structure of a diffraction element 30 according to a first embodiment of the present invention.
In the diffraction element of this embodiment, a grating groove is engraved on one surface 31 of the transparent substrate 2 at a pitch d, and the reflection film 1 is formed thereon. The reflective film 1 is formed to have a sufficiently small thickness while having characteristics as a reflective film. For example,
The reflection film 1 can be formed by providing a metal film having a high reflectance such as aluminum or a dielectric multilayer film on the lattice surface 31. The reflection film 1 has a thickness of 50 to 300 n.
m, preferably about 100 nm, the grating grooves can be formed uniformly without impairing the shape. The transparent substrate 2 is typically made of glass, and may be a substrate material having a light-transmitting property with respect to the wavelength of light to be used. Less than,
In this specification, "transparent" means that it has a light-transmitting property with respect to the wavelength of light used.

【００４４】表面３１の格子溝の形状は、好ましくは、
表面３１に形成される回折格子が、その表裏両面で対称
となるように刻印される。ここに、対称とは、格子溝に
平行な所定の軸を中心とした実質上１８０度の回転に対
して重なるような、実質的に対称的形状をしている。例
えば、図１（ａ）に於いては、格子溝は正弦波形状に示
され、所定の軸は、０度のところである。もっとも、格
子溝の形状はこれに限られるものではない。The shape of the lattice grooves on the surface 31 is preferably
The diffraction grating formed on the front surface 31 is engraved so as to be symmetrical on both front and back surfaces. Here, the symmetry has a substantially symmetrical shape so as to overlap with a rotation of substantially 180 degrees about a predetermined axis parallel to the lattice groove. For example, in FIG. 1A, the grating grooves are shown in a sine wave shape, and the predetermined axis is at 0 degrees. However, the shape of the lattice groove is not limited to this.

【００４５】次に、この回折素子３０の動作を図１
（ａ）を参照しながら説明する。図１（ａ）に示される
透明基板２の上方から、反射膜１に波長λ₁の光が角度
θ₀で入射した場合、回折素子３０は、反射型の回折格
子として機能する。このとき、１次回折される回折光の
角度αは、下記の式（１）で表される。ここで、回折角
αは、回折光が格子面の法線となす角である。尚、以下
の議論では、１次の回折光について説明する。Next, the operation of the diffraction element 30 will be described with reference to FIG.
This will be described with reference to FIG. When light of wavelength λ ₁ is incident on the reflective film 1 at an angle θ ₀ from above the transparent substrate 2 shown in FIG. 1A, the diffraction element 30 functions as a reflective diffraction grating. At this time, the angle α of the first-order diffracted light is represented by the following equation (1). Here, the diffraction angle α is an angle formed by the diffracted light and the normal to the lattice plane. In the following discussion, first-order diffracted light will be described.

【００４６】 sinθ₀＋sinα＝λ₁／ｄ（１）特に、回折素子を３０リトロー配置（Littrow mountin
g）する場合には、入射角θ₀と回折角αとがほぼ等しく
なり、回折効率を最大にすることができる。このとき、
近似的にθ₀＝α＝θ_L（θ_L：リトロー角）とすれば、
式（１）より、 sinθ₀＝λ₁／（２ｄ）（２）となる。光の入射角θ₀がリトロー角θ_Lを中心として±
５度程度の範囲内にあれば、回折効率が高く、回折効率
の偏光依存性も少ない。この条件の下で、角度θ₀で回
折素子３０に入射した光は、波長λ₁に応じた回折角α
で回折される。例えば、入射光が波長λ₁近傍の複数の
波長λ_a、λ_b、・・・の光を含んでいる場合、各々の波
長に応じた角度α_a、α_b、・・・で回折される。Sin θ ₀ + sin α = λ ₁ / d (1) In particular, 30 Littrow arrangements of diffraction elements (Littrow mountin)
g), the incident angle θ ₀ is substantially equal to the diffraction angle α, and the diffraction efficiency can be maximized. At this time,
If approximately θ ₀ = α = θ _L (θ _L : Littrow angle),
From equation (1), sin θ ₀ = λ ₁ / (2d) (2) The light incident angle θ ₀ is ±± around the Littrow angle θ _L
When it is within the range of about 5 degrees, the diffraction efficiency is high and the polarization dependence of the diffraction efficiency is small. Under this condition, light incident on the diffraction element 30 at an angle θ ₀ has a diffraction angle α corresponding to the wavelength λ _1.
Diffracted by For example, when the incident light includes light of _a plurality of wavelengths λ _a , λ _b ,... Near the wavelength λ ₁ , the light is diffracted at angles α _a , α _b ,. .

【００４７】一方、図１（ａ）に於いて、透明基板２の
下方から、波長λ₂の光が、透明基板２を介して反射膜
１に入射する場合を考える。波長λ₂の光は、透明基板
２の裏面３２に角度φで入射し、透明基板２中で、角度
θ₀’で反射膜１に入射する。透明基板２の屈折率をｎ
とすると、このとき、角度θ₀’及びφの関係は、スネ
ルの法則から式（３）のように表せる。On the other hand, in FIG. 1A, a case where light of wavelength λ ₂ is incident on the reflection film 1 via the transparent substrate 2 from below the transparent substrate 2 will be considered. The light having the wavelength λ ₂ is incident on the back surface 32 of the transparent substrate 2 at an angle φ, and is incident on the reflective film 1 at an angle θ ₀ ′ in the transparent substrate 2. Let the refractive index of the transparent substrate 2 be n
Then, at this time, the relationship between the angles θ ₀ ′ and φ can be expressed as in equation (3) from Snell's law.

【００４８】ｎ・sinθ₀’＝sinφ （３）また、透明基板２の中での光の等価波長λ₂’は、次式
（４）で表せる。N · sin θ ₀ ′ = sin φ (3) The equivalent wavelength λ ₂ ′ of light in the transparent substrate 2 can be expressed by the following equation (4).

【００４９】 λ₂’＝λ₂／ｎ（４）従って、波長λ₂’が波長λ₁に実質的に等しく、そして
θ₀’がθ₀に実質的に等しくなるように、屈折率ｎ及び
入射角φを選択することにより、反射膜１による透明基
板２の中での波長λ₂の光の回折は、透明基板２を介さ
ない波長λ₁の光の回折と実質的に同じものとなる。回
折素子３０は、波長λ₁及びλ₂の光の両方に対して、同
様の回折効率を有する反射型回折格子として機能する。
また、格子溝の形状を表裏対称に形成すれば、回折素子
３０は、波長λ₂に対しても、波長λ₁に対する分光特性
と同じ分光特性を有することになる。Λ ₂ ′ = λ ₂ / n (4) Thus, the refractive indices n and n are such that wavelength λ ₂ ′ is substantially equal to wavelength λ ₁ and θ ₀ ′ is substantially equal to θ _0. By selecting the incident angle φ, the diffraction of light of wavelength λ _{2 in} the transparent substrate 2 by the reflection film 1 becomes substantially the same as the diffraction of light of wavelength λ ₁ without passing through the transparent substrate 2. . The diffraction element 30 functions as a reflection type diffraction grating having the same diffraction efficiency with respect to both lights of wavelengths λ ₁ and λ ₂ .
Further, by forming the shape of the grating grooves on the front and back symmetrically, the diffraction element 30, also with respect to the wavelength lambda _2, will have the same spectral characteristics and the spectral characteristics with respect to the wavelength lambda _1.

【００５０】なお、透明基板２の裏面３２は平面とする
ことが望ましい。裏面３２の格子溝配列方向に対する方
向（角度）は、格子溝配列方向と必ずしも平行である必
要はない。例えば、図１（ｂ）に示すようなプリズム状
の形状の透明基材２１の一面３１に格子溝を刻印して回
折素子３３を構成することもできる。It is desirable that the rear surface 32 of the transparent substrate 2 be flat. The direction (angle) of the back surface 32 with respect to the lattice groove arrangement direction does not necessarily need to be parallel to the lattice groove arrangement direction. For example, the diffraction element 33 can be formed by engraving a grating groove on one surface 31 of the transparent base material 21 having a prism shape as shown in FIG.

【００５１】このように、本実施例によれば、格子溝が
刻印されている面（反射膜１）の表裏両面に入射される
異なる波長の光に対して分光特性を同じくすることがで
き、１つの素子で２つ以上の波長帯に利用可能な回折素
子を構成することができる。As described above, according to the present embodiment, the spectral characteristics can be made the same for light of different wavelengths incident on the front and back surfaces of the surface (reflection film 1) on which the grating grooves are engraved. One element can constitute a diffraction element that can be used in two or more wavelength bands.

【００５２】（実施例２）図２は、本発明の第２の実施
例の回折素子２０を示している。回折素子２０は、透明
基板２の裏面３２に反射防止膜４を備えている。その他
の点は実施例１で説明した回折素子３０と同様である。(Embodiment 2) FIG. 2 shows a diffraction element 20 according to a second embodiment of the present invention. The diffraction element 20 includes an antireflection film 4 on the back surface 32 of the transparent substrate 2. Other points are the same as those of the diffraction element 30 described in the first embodiment.

【００５３】数式（３）から分かるように、一般に、波
長λ₂の光が透明基板２の裏面３２（４１）に入射する
角度φは、透明基板２の中を伝搬して反射膜１に入射す
る角度θ₀’よりも大きくなるため、波長λ₂の光は裏面
３２で反射され易い。そこで、透明基板２の裏面に反射
防止膜４をもうけて裏面４１とすることにより、透明基
板２へ入射する光の透過強度を高める事が出来る。As can be seen from the equation (3), generally, the angle φ at which the light having the wavelength λ ₂ is incident on the back surface 32 (41) of the transparent substrate 2 is transmitted through the transparent substrate 2 and incident on the reflection film 1. Is larger than the angle θ ₀ ′, the light of wavelength λ ₂ is easily reflected on the back surface 32. Therefore, by forming an anti-reflection film 4 on the back surface of the transparent substrate 2 to form the back surface 41, the transmission intensity of light incident on the transparent substrate 2 can be increased.

【００５４】波長λ₂の光が、入射角θ₀で反射膜１に入
射し、回折角α’で回折される場合には、式（１）と同
様に、次式（５）をみたす。When light having a wavelength λ ₂ is incident on the reflection film 1 at an incident angle θ ₀ and is diffracted at a diffraction angle α ′, the following expression (5) is satisfied, similar to the expression (1).

【００５５】 sinθ₀＋sinα’＝λ₂／ｄ（５）ここで、波長λ₂の光が反射膜１で回折されずに全て反
射されるならば、波長λ₂の回折光の回折角α’は、次
式（６）をみたしている。但し、λ₂＞λ₁であるとして
いる。Sin θ ₀ + sin α ′ = λ ₂ / d (5) Here, if all the light of wavelength λ ₂ is reflected by the reflection film 1 without being diffracted, the diffraction angle α ′ of the diffracted light of wavelength λ ₂ Satisfies the following equation (6). However, it is assumed that λ ₂ > λ ₁ .

【００５６】 sinα’＞１（６）入射角θ₀はリトロー角θ_Lである場合には、式（２）が
成り立つので、式（６）に式（５）及び（２）を代入す
ると、次式（７）が得られる。Sinα ′> 1 (6) When the incident angle θ ₀ is the Littrow angle θ _L , Equation (2) is satisfied. Therefore, when Equations (5) and (2) are substituted into Equation (6), The following equation (7) is obtained.

【００５７】 λ₂−λ₁／２＞ｄ（７）従って、波長λ₁及びλ₂が上式（７）の関係をみたして
いれば、これらの波長のが多重された光が回折素子２０
（または３０）に入射した場合、波長λ₁の光のみが回
折され、波長λ₂の光は全反射される。[0057] _{_{λ 2 -λ 1/2> d}} (7) Therefore, if the wavelength lambda ₁ and lambda ₂ satisfies the relationship of the equation (7), the light of these wavelengths are multiplexed diffraction element 20
(Or 30), only the light of wavelength λ ₁ is diffracted, and the light of wavelength λ ₂ is totally reflected.

【００５８】一方、波長λ₂の光が回折素子２０（また
は３０）の裏面４１（３２）から入射した場合には、透
明基板２の屈折率ｎが次式（８）ｎ＝λ₂／λ₁ （８）をみたしていれば、波長λ₂の光の透明基板中での等価
波長はλ₁となるため、波長λ２で入射した光は全反射
されることなく反射膜１で回折される。On the other hand, when the light of wavelength λ ₂ is incident from the back surface 41 (32) of the diffraction element 20 (or 30), the refractive index n of the transparent substrate 2 is given by the following equation (8): n = λ ₂ / λ ₁ (8), since the equivalent wavelength of the light of wavelength λ ₂ in the transparent substrate is λ ₁ , the light incident at wavelength λ 2 is diffracted by the reflection film 1 without being totally reflected. You.

【００５９】（実施例３）次に、本発明の第３の実施例
の回折素子３４について図３を参照しながら説明する。
回折素子３４においては、反射膜１の上面に透明保護層
５が形成されている。その他の点は実施例１で説明した
回折素子３０と同様である。(Embodiment 3) Next, a diffraction element 34 according to a third embodiment of the present invention will be described with reference to FIG.
In the diffraction element 34, the transparent protective layer 5 is formed on the upper surface of the reflection film 1. Other points are the same as those of the diffraction element 30 described in the first embodiment.

【００６０】波長λ₃の光が透明保護層５の上面５１に
入射角ψで入射し、透明保護層５を伝搬して反射膜１に
入射角θ’で入射するとき、透明保護層５の屈折率をｎ
₁とすると、入射角ψとθ’との関係は、次式（９）で
与えられる。When light having a wavelength λ ₃ is incident on the upper surface 51 of the transparent protective layer 5 at an incident angle ψ and propagates through the transparent protective layer 5 and is incident on the reflective film 1 at an incident angle θ ′, the light of the transparent protective layer 5 Refractive index is n
Assuming that ₁ , the relationship between the incident angle ψ and θ ′ is given by the following equation (9).

【００６１】ｎ₁・sinθ’＝sinψ （９）透明保護層５の中を伝搬する光の等価波長λ₃’は次式
（１０）で与えられる。 λ₃’＝λ₃／ｎ₁ （１０）従って、ｎ₁＝λ₁／λ₃であるような屈折率ｎ₁を有する
透明保護層５を用い、θ’＝θ₀（＝θ_L）となるように
入射角ψを調節することにより、回折格子３４に入射し
た波長λ₃の光は、第１の実施例の回折素子３０に入射
した波長λ₁の光が回折される場合と同様の回折効率及
び分光特性で回折される。N ₁ · sin θ ′ = sinψ (9) The equivalent wavelength λ ₃ ′ of light propagating in the transparent protective layer 5 is given by the following equation (10). λ ₃ ′ = λ ₃ / n ₁ (10) Therefore, using a transparent protective layer 5 having a refractive index n ₁ such that n ₁ = λ ₁ / λ ₃ , and θ ′ = θ ₀ (= θ _L ) By adjusting the incident angle ψ such that the light of the wavelength λ ₃ incident on the diffraction grating 34 is the same as the case where the light of the wavelength λ ₁ incident on the diffraction element 30 of the first embodiment is diffracted. Diffracted with diffraction efficiency and spectral characteristics.

【００６２】透明基板２中に於ける入射光の振舞いは、
透明基板２の屈折率をｎとして、第１の実施例と同様に
式（３）及び（４）で表せる。The behavior of the incident light in the transparent substrate 2 is as follows:
Assuming that the refractive index of the transparent substrate 2 is n, it can be expressed by Expressions (3) and (4) as in the first embodiment.

【００６３】また、波長λ₂の光が角度ψで回折素子３
４の上面５１に入射し、保護膜５中を伝搬して反射膜１
３に角度θ’で入射した光が、反射膜１で回折されずに
全反射される条件は、実施例２で説明したのと同様に、
以下のようにして求められる。透明保護層５の中に於
いて、等価波長λ₂”＝λ₂／ｎ₁及び等価波長λ₃’＝λ
₃／ｎ₁＝λ₁について、式（７）が成り立つので、 λ₂−λ₃／２＞ｎ₁・ｄ（１１）ｎ＝ｎ₁・λ₂／λ₃ （１２）本実施例によれば、反射膜１上に透明保護層５を設ける
ことにより、格子表面が外気より遮断され腐食などをお
さえて長期にわたる使用に耐えられるようにすることが
できる。The light of wavelength λ ₂ is diffracted by the diffraction element 3 at an angle ψ.
4 and propagates in the protective film 5 to be reflected on the reflective film 1.
3 is totally reflected without being diffracted by the reflection film 1 in the same manner as described in the second embodiment.
It is determined as follows. In the transparent protective layer 5, the equivalent wavelength λ ₂ ″ = λ ₂ / n ₁ and the equivalent wavelength λ ₃ ′ = λ
About ₃ / n _₁ = _λ _1, since Equation (7) _{_{holds, λ 2 -λ 3/2>}} n 1 · d (11) n = n 1 · λ 2 / λ 3 (12) According to the present embodiment For example, by providing the transparent protective layer 5 on the reflection film 1, the lattice surface can be shielded from the outside air, corrosion can be suppressed, and it can be used for a long time.

【００６４】（実施例４）図４は、本発明の第４の実施
例の回折素子３５を示している。回折素子３５は、透明
基板２の裏面３２に反射防止膜４を備え、更に透明保護
層５の表面５１に反射防止膜６を設けている。その他の
点は実施例３で説明した回折素子３４と同様である。(Embodiment 4) FIG. 4 shows a diffraction element 35 according to a fourth embodiment of the present invention. The diffraction element 35 has an anti-reflection film 4 on the back surface 32 of the transparent substrate 2, and further has an anti-reflection film 6 on the front surface 51 of the transparent protective layer 5. Other points are the same as those of the diffraction element 34 described in the third embodiment.

【００６５】このような構成により、回折素子３５の上
面５２及び下面４１へ入射する光の反射を押え、効率よ
く透明保護層５及び透明基板２に伝搬させることができ
る。With such a configuration, reflection of light incident on the upper surface 52 and the lower surface 41 of the diffraction element 35 can be suppressed, and the light can be efficiently transmitted to the transparent protective layer 5 and the transparent substrate 2.

【００６６】（実施例５）図５（ａ）及び（ｂ）は、本
発明の第５の実施例の回折素子３６及び３７を示してい
る。回折素子３６の透明基板２及び透明保護層５は、各
々屈折率の異なる複数の部分から形成されている。図５
（ａ）に示されるように、例えば、透明基板２は、屈折
率ｎ₃の部分及びｎ₄の部分の２つ部分から形成されてい
る。屈折率ｎ_kの部分に入射した波長λの光は、等価波
長λ’＝λ／ｎ_k（ｋ＝３，４）で回折されるため、回
折素子３６は、裏面３２に入射する２つの波長領域（λ
＝ｎ_kλ₁，ｋ＝３，４）の光を回折することができる。
透明保護層５も同様に、屈折率ｎ₁の部分及びｎ₂の部分
の２つ部分から形成されてい場合、回折素子３６は、上
面５１に入射する２つの波長領域（λ＝ｎ_kλ₁，ｋ＝
１，２）の光を回折することができる。異なる屈折率を
有する部分は２つに限らず、また、必要に応じて、透明
基板２又は透明保護層５の一方にのみ設けることもでき
る。(Embodiment 5) FIGS. 5A and 5B show diffraction elements 36 and 37 according to a fifth embodiment of the present invention. The transparent substrate 2 and the transparent protective layer 5 of the diffraction element 36 are formed from a plurality of portions each having a different refractive index. FIG.
As shown in (a), for example, the transparent substrate 2 is formed from two portions, a portion having a refractive index of n _{3 and} a portion having a refractive index of n ₄ . The light of the wavelength λ incident on the portion of the refractive index _nk is diffracted at the equivalent wavelength λ ′ = λ / _nk (k = 3, 4). Region (λ
= N _k λ ₁ , k = 3, 4) can be diffracted.
Likewise transparent protective layer 5, if formed from two portions of the parts and n ₂ of the portion of the refractive index n _1, the diffraction element 36, the two wavelength ranges to be incident on the upper surface 51 (λ = n _k λ ₁ , K =
1, 2) light can be diffracted. The number of portions having different refractive indices is not limited to two, and may be provided only on one of the transparent substrate 2 and the transparent protective layer 5 as necessary.

【００６７】図５（ｂ）に示される回折素子３７は、透
明基板２の裏面３２に反射防止膜４を備え、更に透明保
護層５の表面５１に反射防止膜６を設けている。その他
の点は回折素子３６と同様である。このような構成によ
り、回折素子３５の上面５２及び下面４１へ入射する光
の反射を押え、効率よく透明保護層５及び透明基板２に
伝搬させることができる。反射防止膜は上面５１又は下
面３２のどちらか一方にのみ設けてもよい。The diffraction element 37 shown in FIG. 5B has an anti-reflection film 4 on the rear surface 32 of the transparent substrate 2 and an anti-reflection film 6 on the front surface 51 of the transparent protective layer 5. Other points are the same as those of the diffraction element 36. With such a configuration, reflection of light incident on the upper surface 52 and the lower surface 41 of the diffraction element 35 can be suppressed, and the light can be efficiently transmitted to the transparent protective layer 5 and the transparent substrate 2. The antireflection film may be provided on only one of the upper surface 51 and the lower surface 32.

【００６８】（実施例６）次に、本発明の回折素子を用
いた光合分波装置を図６を参照しながら説明する。Embodiment 6 Next, an optical multiplexing / demultiplexing apparatus using the diffraction element of the present invention will be described with reference to FIG.

【００６９】図６は本発明の第２の実施例の回折素子２
０を用いた場合の光合分波装置の構成図である。回折素
子は、この他に、上述の実施例における回折素子３０、
または３４〜３７を用いてもよい。回折素子２０、レン
ズ７、第１の入力ファイバ１０、及び第１の受光ファイ
バアレイ１２はリトロー配置されている。回折素子２
０、レンズ９、第２の入力ファイバ１１、及び第２の受
光ファイバアレイ１３も同様である。レンズ８は、回折
素子２０の反射膜１で全反射された光を第２の入力ファ
イバ１１に導くためのものである。FIG. 6 shows a diffraction element 2 according to a second embodiment of the present invention.
It is a block diagram of the optical multiplexing / demultiplexing device when 0 is used. The diffractive element is, in addition to this, the diffractive element 30 in the above-described embodiment,
Alternatively, 34 to 37 may be used. The diffraction element 20, the lens 7, the first input fiber 10, and the first light receiving fiber array 12 are arranged in a Littrow arrangement. Diffraction element 2
The same applies to the lens 0, the lens 9, the second input fiber 11, and the second light receiving fiber array 13. The lens 8 is for guiding the light totally reflected by the reflection film 1 of the diffraction element 20 to the second input fiber 11.

【００７０】第１の入力ファイバ１０から出射される光
は波長多重されており、例えば、図７に示されるような
スペクトル分布を有している。短波長側の波長多重光１
４は、波長λ_a、λ_b、λ_c、及びλ_dのスペクトル成分を
有するの波長帯であり、長波長側の波長多重光１５は、
波長λ_e、λ_f、λ_g、及びλ_hののスペクトル成分を有す
るの波長帯である。以下、短波長側の波長帯をλ₁、長
波長側の波長帯をλ₂と表すことにする。The light emitted from the first input fiber 10 is wavelength-division multiplexed and has, for example, a spectrum distribution as shown in FIG. Short wavelength side multiplexed light 1
Reference numeral 4 denotes a wavelength band having spectral components of wavelengths λ _a , λ _b , λ _c , and λ _d .
Wavelength bands having spectral components at wavelengths λ _e , λ _f , λ _g , and λ _h . Hereinafter, the wavelength band on the short wavelength side is represented by λ ₁ , and the wavelength band on the long wavelength side is represented by λ ₂ .

【００７１】以下、本発明の光合分波装置について、そ
の動作を説明する。ここでは光分波器の動作について説
明するが、光の入力と出力を逆にすれば、光合波器の動
作も全く同様に考えることができる。The operation of the optical multiplexer / demultiplexer according to the present invention will be described below. Here, the operation of the optical demultiplexer will be described. However, if the input and output of light are reversed, the operation of the optical multiplexer can be considered in exactly the same way.

【００７２】波長λ_a〜λ_hで波長多重された光は、第１
の入力ファイバ１０から出射され、レンズ７によってコ
リメートされて、回折素子２０の反射膜１を設けた格子
面１９に入射角θ₀で入射する。回折素子２０の反射膜
１を設けた格子面１９は、短波長側の波長域λ₁の波長
多重光１４に対して、回折効率の高い波長分散能力を有
している。波長λ_a〜λ_dの光は式（１）に従って波長分
散され、再びレンズ７を介して第１の受光ファイバアレ
イ１２のそれぞれの光ファイバに集束する。図６には、
波長λ_dの光について模式的に示されている。このよう
にして、波長λ_a〜λ_dの光は、波長分離されて受光ファ
イバアレイ１２の各々光ファイバから出力される。一
方、長波長側の波長域λ₂の波長多重光１５は、式
（７）の不等式を満足しているので、反射膜１を設けた
格子面１９では回折及び波長分散されずに全反射され
る。全反射された波長λ_e〜λ_hの光は、レンズ８を介し
て第２の入力ファイバ１１に導かれる。Light multiplexed at wavelengths λ _{a to} λ _h is the first light.
Out of the input fiber 10, is collimated by the lens 7, and is incident on the grating surface 19 of the diffraction element 20 provided with the reflection film 1 at an incident angle θ ₀ . Lattice plane 19 provided with the reflective film 1 of the diffraction element 20, to the wavelength-multiplexed light 14 of the wavelength region lambda ₁ of the short wavelength side, and has a high wavelength dispersion capability diffraction efficiency. The light of the wavelengths λ _{a to} λ _d is wavelength-dispersed according to the equation (1), and is again focused on each optical fiber of the first light receiving fiber array 12 via the lens 7. In FIG.
It is schematically shown with respect to the light having a wavelength lambda _d. In this manner, the light having the wavelengths λ _{a to} λ _d is wavelength-separated and output from each optical fiber of the light receiving fiber array 12. On the other hand, the wavelength-division multiplexed light 15 in the wavelength region λ ₂ on the long wavelength side satisfies the inequality expression (7), and is totally reflected without diffraction and wavelength dispersion on the grating surface 19 provided with the reflective film 1. You. Light of wavelengths λ _{e to} λ _h totally reflected is guided to the second input fiber 11 via the lens 8.

【００７３】第２の入力ファイバ１１から出射された波
長多重光１５は、レンズ９によってコリメートされ、回
折素子２０の反射防止膜４を設けた裏面４１に入射角φ
で入射する。透明基板２の屈折率ｎは式（６）をみたし
ているので、波長帯λ₂の波長多重光１５は、透明基板
２を介して、反射膜１によって同様に高い回折効率で波
長分散される。波長分散された各々の波長λ_e〜λ_hの光
は、レンズ９を介して第２の受光ファイバアレイ１３の
各々の光ファイバに結合され、出力される。The wavelength-division multiplexed light 15 emitted from the second input fiber 11 is collimated by the lens 9 and incident on the back surface 41 of the diffraction element 20 on which the antireflection film 4 is provided.
Incident. Since the refractive index n of the transparent substrate 2 satisfies the expression (6), the wavelength multiplexed light 15 in the wavelength band λ ₂ is similarly wavelength-dispersed with high diffraction efficiency by the reflection film 1 via the transparent substrate 2. You. The wavelength-dispersed lights of the wavelengths λ _{e to} λ _h are coupled to the respective optical fibers of the second light-receiving fiber array 13 via the lens 9 and output.

【００７４】回折素子２０は、格子間隔ｄが、例えば、
格子溝本数が１２００本／ｍｍであるようなブレーズド
（blazed）回折格子を用いると、回折効率の高いものと
なる。例えば、短波長側の波長域λ₁が０.８μｍ帯、長
波長側の波長域λ₂が１.３μｍ帯であるような波長多重
光の光分波をを行う場合には、透明基板２の屈折率ｎを
１.５〜１.６に設定すればよい。この場合、第１の入力
ファイバ１０から回折素子２０へ入射する光の入射角θ
₀は約３０度であり、第２の入力ファイバ１１から回折
素子２０へ入射する光の入射角は約５４度となる。透明
基板２の材質としてはガラスや透明樹脂などの誘電帯材
料を用いればよい。The diffraction element 20 has a lattice spacing d of, for example,
If a blazed diffraction grating having a number of grating grooves of 1200 / mm is used, the diffraction efficiency becomes high. For example, when performing light demultiplexing of wavelength-division multiplexed light such that the wavelength region λ ₁ on the short wavelength side is in the 0.8 μm band and the wavelength region λ ₂ on the long wavelength side is in the 1.3 μm band, the transparent substrate 2 May be set to 1.5 to 1.6. In this case, the incident angle θ of the light incident on the diffraction element 20 from the first input fiber 10
₀ is about 30 degrees, and the incident angle of light incident on the diffraction element 20 from the second input fiber 11 is about 54 degrees. As a material of the transparent substrate 2, a dielectric band material such as glass or transparent resin may be used.

【００７５】このように、本実施例によれば、１つの回
折素子を用いることによって、２つの波長帯で回折効率
の高い光合分波装置を得ることができる。即ち、入射光
の挿入損失が低く、且つ広い帯域出波長分散を行うこと
ができる光合分波装置を構成することができる。As described above, according to the present embodiment, an optical multiplexer / demultiplexer having high diffraction efficiency in two wavelength bands can be obtained by using one diffraction element. That is, it is possible to configure an optical multiplexer / demultiplexer that has low insertion loss of incident light and can perform wide band wavelength dispersion.

【００７６】（実施例７）次に、本発明のもう一つの実
施例による光合分波装置について、図８（ａ）及び
（ｂ）を参照しながら説明する。(Embodiment 7) Next, an optical multiplexer / demultiplexer according to another embodiment of the present invention will be described with reference to FIGS. 8 (a) and 8 (b).

【００７７】図８（ａ）及び（ｂ）において、回折素子
２０、レンズ７、入力ファイバ１０、及び受光ファイバ
１６は、リトロー配置されている。受光素子２０は、回
転機構部１７によって、格子溝方向に平行な回転軸を中
心に回転させることができる。即ち、レンズ７を介して
入射する光に対して、回折素子２０の表裏両面（１９及
び４１）を用いることができ、各々の面に入射する光の
入射角を調節することができる。図８（ａ）は短波長側
の波長域λ₁の波長多重光１４を選択的に波長分散する
場合の構成であり、図８（ｂ）は長波長帯の波長域λ₂
の波長多重光１５を選択的に波長分散する場合の構成で
ある。回折素子は、この他に、上述の実施例における回
折素子３０、または３４〜３７を用いてもよい。8A and 8B, the diffraction element 20, the lens 7, the input fiber 10, and the light receiving fiber 16 are arranged in a Littrow arrangement. The light receiving element 20 can be rotated by the rotation mechanism 17 about a rotation axis parallel to the lattice groove direction. That is, the front and rear surfaces (19 and 41) of the diffraction element 20 can be used for the light incident through the lens 7, and the incident angles of the light incident on each surface can be adjusted. 8 (a) is selectively in the case of wavelength dispersion constitutes the wavelength-multiplexed light 14 of the wavelength region lambda ₁ of the short wavelength side, FIG. 8 (b) wavelength region of long wavelength lambda ₂
This is a configuration in the case where the wavelength-division multiplexed light 15 is selectively wavelength-dispersed. Alternatively, the diffraction element 30 or 34 to 37 in the above-described embodiment may be used.

【００７８】以上のように構成された光合分波装置につ
いて、以下、上記図７、図８（ａ）及び（ｂ）を参照し
ながらその動作を説明する。The operation of the optical multiplexer / demultiplexer configured as described above will be described below with reference to FIGS. 7, 8A and 8B.

【００７９】図８（ａ）及び（ｂ）において、波長λ_a
〜λ_hで波長多重された光は、入力ファイバ１０から出
射され、レンズ７によってコリメートされて、回折素子
２０に入射する。図８（ａ）の場合、合分波装置は、入
射光が回折素子２０の反射膜１を設けた格子面１９に入
射角θで入射するように配置されている。入射角θがθ
₀にほぼ等しいとき、波長域λ₁の波長多重光１４は、回
折素子２０によって高い回折効率で波長分散される。入
力ファイバ１０と受光ファイバ１６とは隣接して配置さ
れているため、式（２）で表わされる入射角度、即ちリ
トロー角で回折される波長の回折光のみが受光ファイバ
１６に結合する。このとき、波長域λ₂の光は、回折素
子２０によって回折されないため、波長域λ₁の光のみ
が、以下のようにして選択的に波長分散される。In FIGS. 8A and 8B, the wavelength λ _a
To [lambda] _h light wavelength-multiplexed in is emitted from the input fiber 10 is collimated by the lens 7 is incident on the diffraction element 20. In the case of FIG. 8A, the multiplexing / demultiplexing device is arranged so that the incident light is incident on the grating surface 19 of the diffraction element 20 on which the reflection film 1 is provided at an incident angle θ. Incident angle θ is θ
When substantially equal to ₀ , the wavelength division multiplexed light 14 in the wavelength range λ ₁ is wavelength-dispersed by the diffraction element 20 with high diffraction efficiency. Since the input fiber 10 and the light receiving fiber 16 are disposed adjacent to each other, only the incident light represented by the equation (2), that is, the diffracted light having the wavelength diffracted at the Littrow angle is coupled to the light receiving fiber 16. In this case, light in the wavelength region lambda _2, since not diffracted by the diffraction element 20, only light in the wavelength region lambda ₁ is selectively chromatic dispersion in the following manner.

【００８０】図８（ａ）で、入射角θ＝θ_aのときに波
長λ_aの光が受光ファイバ１６に結合していたとする。
回折素子２０を回転機構部１７により反時計方向に微少
に回転させ、入射角をθ_b、θ_c、θ_dと変化させるに従
い、波長λ_b，λ_c，λ_dの光を順次受光ファイバ１６に
結合させることができる。[0080] In FIG. 8 (a), the light of the wavelength lambda _a is bonded to the light receiving fiber 16 when the incident angle θ = θ _a.
As the diffraction element 20 is slightly rotated counterclockwise by the rotation mechanism 17 and the incident angles are changed to θ _b , θ _c , and θ _d , the light of wavelengths λ _b , λ _c , and λ _d are sequentially transmitted to the light receiving fiber 16. Can be combined.

【００８１】次に、長波長側の波長域λ₂の波長多重光
１５を選択的に波長分散させる場合には、回転機構部１
７により、入射光に対して回折素子２０を裏返すように
回転させ、図８（ｂ）に示される様に配置する。これに
より、入力ファイバ１０から出射された波長多重光は、
入射角φで裏面４１に入射し、反射防止膜４及び透明基
板２を介して格子面（反射膜１）に入射する。そして、
波長多重光１５は、波長多重光１４の場合と同様に、回
折素子２０によって高い回折効率で波長分散される。上
述したのと同様に、回転機構部１７によって入射角を調
節することによって、所望の波長λ_e〜λ_hの光を受光フ
ァイバ１６に結合させ、選択的に出力させることができ
る。Next, when the wavelength-division multiplexed light 15 of the wavelength region λ ₂ on the long wavelength side is selectively wavelength-dispersed, the rotating mechanism 1
7, the diffraction element 20 is rotated so as to be turned over with respect to the incident light, and is arranged as shown in FIG. Thereby, the wavelength multiplexed light emitted from the input fiber 10 is
The light is incident on the back surface 41 at an incident angle φ, and is incident on the grating surface (reflection film 1) via the antireflection film 4 and the transparent substrate 2. And
The wavelength-division multiplexed light 15 is wavelength-dispersed with high diffraction efficiency by the diffraction element 20, as in the case of the wavelength-division multiplexed light 14. As described above, by adjusting the angle of incidence by the rotation mechanism 17, light of desired wavelengths λ _{e to} λ _h can be coupled to the light receiving fiber 16 and selectively output.

【００８２】以上のように、本実施例によれば、１つの
回折素子を回転させることによって、２つの波長帯にお
いて回折効率の高い波長分散を選択的に行い、１本の受
光ファイバから出力することができる。即ち、入射光の
挿入損失が低く、且つ広い帯域出波長分散を行うことが
できる。更に、実施例６に比べ、第２の入力ファイバ及
び第２の受光ファイバアレイを備える必要がない。回転
機構１７としては、高精度に位置決めできるステッピン
グモータや、その他の回転機構を制御する各種の駆動方
法によっても実現（inplement）できる。As described above, according to this embodiment, by rotating one diffractive element, chromatic dispersion having high diffraction efficiency is selectively performed in two wavelength bands, and output from one light receiving fiber. be able to. That is, it is possible to reduce the insertion loss of the incident light and perform wide band wavelength dispersion. Furthermore, unlike the sixth embodiment, there is no need to provide a second input fiber and a second light receiving fiber array. The rotation mechanism 17 can also be implemented (implemented) by a stepping motor capable of positioning with high accuracy, or other various driving methods for controlling the rotation mechanism.

【００８３】本実施例では回折素子２０を回転させる例
を挙げたが、入力ファイバ１０や受光ファイバ１６を移
動させることによっても同等の効果を挙げることができ
る。この場合、高精度な移動機構、例えばピエゾ素子等
の積層形圧電素子や光ピックアップに応用されるリニア
アクチュエータを用いることにより実現できる。In this embodiment, the example in which the diffraction element 20 is rotated has been described. However, the same effect can be obtained by moving the input fiber 10 and the light receiving fiber 16. This can be realized by using a highly accurate moving mechanism, for example, a laminated piezoelectric element such as a piezo element or a linear actuator applied to an optical pickup.

【００８４】なお、本実施例では回折素子２０を用いて
説明したが、例えば、回折素子３４又は３５を用いた場
合には、２つの波長帯だけでなく、更に多くの波長帯に
於いて高い回折効率で波長分散を行うことができる。本
発明は、特に０.８μｍ帯と１.３μｍ帯での多重数の多
い波長多重光通信に有用である。Although the present embodiment has been described using the diffractive element 20, for example, when the diffractive element 34 or 35 is used, not only two wavelength bands but also higher wavelength bands are used. Wavelength dispersion can be performed with diffraction efficiency. INDUSTRIAL APPLICABILITY The present invention is particularly useful for wavelength multiplexed optical communication having a large number of multiplexes in the 0.8 μm band and the 1.3 μm band.

【００８５】[0085]

【発明の効果】以上述べたところから明らかなように、
本発明によれば、１つの素子で複数の波長帯に対して、
高い回折効率で使用することができる回折素子を用いる
ことにより、複数の波長帯に対して、高い回折効率で波
長分散を行うことのできる光合分波装置を提供すること
ができる。さらに、複数の回折格子を用いる必要がない
ため、光分波装置を簡単な構成で低価格で提供すること
ができる。As is apparent from the above description,
According to the present invention, for a plurality of wavelength bands with one element,
By using a diffraction element that can be used with high diffraction efficiency, it is possible to provide an optical multiplexing / demultiplexing device that can perform chromatic dispersion with high diffraction efficiency in a plurality of wavelength bands. Further, since there is no need to use a plurality of diffraction gratings, the optical demultiplexer can be provided with a simple configuration at a low price.

[Brief description of the drawings]

【図１】（ａ）及び（ｂ）は、本発明の第１の実施例に
おける回折素子の構成を示す図である。FIGS. 1A and 1B are diagrams showing a configuration of a diffraction element according to a first embodiment of the present invention.

【図２】本発明の第２の実施例における回折素子の構成
を示す図である。FIG. 2 is a diagram illustrating a configuration of a diffraction element according to a second embodiment of the present invention.

【図３】本発明の第３の実施例における回折素子の構成
を示す図である。FIG. 3 is a diagram illustrating a configuration of a diffraction element according to a third embodiment of the present invention.

【図４】本発明の第４の実施例における回折素子の構成
を示す図である。FIG. 4 is a diagram illustrating a configuration of a diffraction element according to a fourth embodiment of the present invention.

【図５】（ａ）及び（ｂ）は、本発明の第５の実施例に
おける回折素子の構成を示す図である。FIGS. 5A and 5B are diagrams showing a configuration of a diffraction element according to a fifth embodiment of the present invention.

【図６】本発明による光合分波装置の構成を示す図であ
る。FIG. 6 is a diagram showing a configuration of an optical multiplexer / demultiplexer according to the present invention.

【図７】波長λ_a〜λ_hの波長多重光のスペクトル分布を
表す概念図である。7 is a conceptual diagram showing a spectrum distribution in the wavelength-multiplexed light of wavelength λ _a ~λ _h.

【図８】（ａ）及び（ｂ）は、本発明によるもう一つの
光合分波装置の構成を示す図である。FIGS. 8A and 8B are diagrams showing a configuration of another optical multiplexer / demultiplexer according to the present invention.

【図９】回折効率の波長及び格子間隔依存性を示した図
である。FIG. 9 is a diagram illustrating the dependence of diffraction efficiency on wavelength and grating interval.

【図１０】従来の回折素子の構成を示す図である。FIG. 10 is a diagram showing a configuration of a conventional diffraction element.

【図１１】従来の光合分波装置の構成を示す図である。FIG. 11 is a diagram showing a configuration of a conventional optical multiplexer / demultiplexer.

[Explanation of symbols]

１反射膜２透明基板４反射防止膜７レンズ８レンズ９レンズ１０第１の入力ファイバ１１第２の入力ファイバ１２第１の受光ファイバアレイ１３第２の受光ファイバアレイ２０回折素子 1 Reflective film 2 Transparent substrate 4 Anti-reflective coating 7 Lens 8 lenses 9 lenses 10 First input fiber 11 Second input fiber 12 First light receiving fiber array 13 Second light receiving fiber array 20 Diffraction element

───────────────────────────────────────────────────── フロントページの続き (56)参考文献特開昭46−7390（ＪＰ，Ａ) 特開昭55−101922（ＪＰ，Ａ) 特開平２−109015（ＪＰ，Ａ) 特開平４−211202（ＪＰ，Ａ) 特開昭54−79057（ＪＰ，Ａ) 特開平３−230106（ＪＰ，Ａ) 特開平４−282603（ＪＰ，Ａ) 特開昭62−61002（ＪＰ，Ａ) 特開平２−219002（ＪＰ，Ａ) (58)調査した分野(Int.Cl.⁷，ＤＢ名) G02B 5/18 G02B 6/28 - 6/293 ──────────────────────────────────────────────────続き Continuation of the front page (56) References JP-A-46-7390 (JP, A) JP-A-55-101922 (JP, A) JP-A-2-109015 (JP, A) JP-A-4-107 JP-A-54-79057 (JP, A) JP-A-3-230106 (JP, A) JP-A-4-282603 (JP, A) JP-A-62-161002 (JP, A) JP-A-2-219002 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 5/18 G02B 6/28-6/293

Claims

(57) [Claims]

A transparent substrate having first and second surfaces;
A diffraction grating is formed from a periodic groove imprinted on the first surface and a reflective film provided on the first surface engraved with the periodic groove, and the reflective film is provided. A diffractive element having a first incident surface corresponding to the first surface, a second incident surface corresponding to the second surface, and causing light to be incident on the first incident surface of the diffractive element. First light input means, first light receiving means for receiving light diffracted by the diffraction element incident on the first incident surface, and light incident on the first incident surface and reflected by the diffraction element Second light input means for receiving the reflected light and making the light incident on the second incident surface of the diffraction element, and a second light receiving means for receiving the light incident on the second incident surface and diffracted by the diffraction element. Light receiving means, wherein the first and second light input means are each provided with the first light input means.
The incident angle θ of the light incident on the launch surface and the second incident surface
Is incident as the Littrow angle θL such that θL−5 ° ≦ θ ≦ θL15 ° , the wavelength λ1 of the light incident on the first incident surface and diffracted,
And the wavelength λ2 of the reflected light (where λ2> λ1)
Indicates that the refractive index of the transparent substrate is n and the distance between the grooves (pitch) is
H) When d is d, the relationship of λ2-λ1 / 2> dn = λ2 / λ1 is satisfied .

2. A transparent substrate having first and second surfaces,
A diffraction grating is formed from a periodic groove imprinted on the surface of the measure 1 and a reflection film provided on the first surface on which the periodic groove is imprinted. A diffractive element having a transparent protective layer provided, a first incident surface corresponding to the first surface provided with the reflective film, and a second incident surface corresponding to the second surface; First light input means for making light incident on the first incident surface of the diffractive element, and first light receiving means for receiving light diffracted by the diffractive element incident on the first incident surface. Second light input means for receiving light incident on the first incident surface and reflected by the diffractive element, and incident on the second incident surface of the diffractive element; and a second light receiving means for receiving the light diffracted by the incident to the diffraction element, said first and second optical input means, respectively, the 1 of input
The incident angle θ of the light incident on the launch surface and the second incident surface
Is incident as the Littrow angle θL such that θL−5 ° ≦ θ ≦ θL + 5 ° , the wavelength λ1 of the light incident on the first incident surface and diffracted,
And the wavelength λ2 of the reflected light (where λ2> λ1)
Means that the refractive index of the transparent substrate is n and the refractive index of the transparent protective layer is n
When the ratio is n1 and the interval (pitch) between the grooves is d, the relationship of λ2−λ1 / 2> nl · dn = nl · λ2 / λ1 is satisfied .

Wherein said the second surface, the optical multiplexing and demultiplexing device according to claim 1 or 2, characterized in that the anti-reflection film is formed.

The shape of the reflective film of claim 4, wherein the diffraction element, according to claim 1, characterized in that it is substantially symmetrical relative to the rotation of 180 degrees around the parallel predetermined axis in the groove or
3. The optical multiplexer / demultiplexer according to 2 .

5. A first lens having a Littrow arrangement with respect to the first incidence surface of the diffraction element, and a second lens having a Littrow arrangement with respect to the second incidence surface of the diffraction element. The optical multiplexer / demultiplexer according to claim 1 or 2 , wherein

6. A transparent substrate having first and second surfaces ,
The first already engraved periodic groove, and the periodic groove
Diffraction from the engraved reflective film provided on the first surface
A grating is formed on the first surface on which the reflection film is provided.
And a second input surface corresponding to the second surface.
A diffractive element having a projection surface and light incident on the diffractive element
A light input means, the light diffracted by the diffraction element, said
Light receiving means for receiving each wavelength of diffracted light, and the light input means
Incident on the first incident surface of the diffraction element
A first arrangement, and light from the light input means is transmitted to the diffraction element.
A second arrangement in which the light is incident on the second incident surface of
The diffraction element, the light input means, and the light receiving
Changing the position and / or orientation of at least one of the means.
And first and second light input means, each of the first and second light input means.
The incident angle θ of the light incident on the launch surface and the second incident surface
Is incident as the Littrow angle θL such that θL−5 ° ≦ θ ≦ θL + 5 ° , the wavelength λ1 of the light incident on the first incident surface and diffracted,
And the wavelength λ2 of the reflected light (where λ2> λ1)
Indicates that the refractive index of the transparent substrate is n and the distance between the grooves (pitch) is
H) When d is d, the relationship of λ2-λ1 / 2> dn = λ2 / λ1 is satisfied .

7. A transparent substrate having first and second surfaces,
A periodic groove engraved on the first surface; and the periodic groove
Diffraction from the engraved reflective film provided on the first surface
A transparent protection provided with a grating and provided on the reflective film
A layer corresponding to the first surface on which the reflective film is provided.
A first incident surface and a second incident surface corresponding to the second surface
Having a diffraction element and a light input for inputting light to the diffraction element
Means for diffracting the light diffracted by the diffractive element.
Light receiving means for receiving for each wavelength of
A first method of making light incident on the first incident surface of the diffraction element;
And the light from the light input means is transmitted to the diffractive element.
A second arrangement for incidence on the second entrance surface.
For the diffraction element, the light input means, and the light receiving means.
Change the position and / or orientation of at least one of them
Control means for controlling the first and second light input means, respectively.
The incident angle θ of the light incident on the launch surface and the second incident surface
Is incident as the Littrow angle θL such that θL−5 ° ≦ θ ≦ θL15 ° , the wavelength λ1 of the light incident on the first incident surface and diffracted,
And the wavelength λ2 of the reflected light (where λ2> λ1)
Means that the refractive index of the transparent substrate is n and the refractive index of the transparent protective layer is n
When the ratio is n1 and the interval (pitch) between the grooves is d, the relationship of λ2-λ1 / 2> n1 · dn = nl · λ2 / λ1 is satisfied .

8. A lens for collimating light from the light input means and condensing light reflected by the diffraction element on the light receiving means, wherein the first arrangement includes a diffraction element. 8. The optical coupling device according to claim 6 , wherein the Littrow arrangement is related to the first incident surface of the diffraction element, and the second arrangement is a Littrow arrangement related to the second incident surface of the diffraction element. Wave device.

9. The arrangement means includes a mechanism for rotating the diffraction element, and by rotating the diffraction element,
The optical multiplexer / demultiplexer according to claim 6, wherein rearrangement is performed from one of the first and second arrangements to the other.

10. The optical multiplexer / demultiplexer according to claim 6, wherein an antireflection film is formed on the second surface.

11. The shape of the reflection film of the diffraction element is:
The optical multiplexer / demultiplexer according to claim 6 , wherein the optical multiplexer / demultiplexer is substantially symmetric with respect to a rotation of 180 degrees about an axis parallel to the groove.