OPTICAL MODULATION ELEMENT

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a light modulation device, and more particularly, to a light modulation device using a thin film made of material with an electro-optical effect.

Description of the Background Art

[0002] Conventionally, a waveguide type light modulation device where optical waveguides or modulation electrodes are formed on a substrate having an electro-optical effect, has been much used in an optical communication field or an optical measurement field.

[0003] Specially, an information transfer amount has a tendency to be increased accompanied by progress of multimedia and thus a widening of a light modulation frequency is demanded. As means for realizing the widening, an external modulation method by an LN modulator or the like employing LiNbO₃ (hereinafter, referred to as "LN") has been proposed. However, in order to realize the widening of the LN modulator, a velocity matching between a microwave which is a modulation signal and a light wave and reduction of driving voltages are required.

[0004] As means for solving such problems, it has been known conventionally that making a thickness of a substrate thin is intended to satisfy a velocity matching condition of a microwave and a light wave as well as to reduce driving voltages.

[0005] In the following Patent Document 1 or 2, an optical waveguide and modulation electrodes are formed on a substrate (hereinafter, referred to as "first substrate") with a thickness of below 30µm and another substrate (hereinafter, referred to as "second substrate") with a lower permittivity than the first substrate is bonded thereto, to reduce an effective refractive for the microwave for intending to match a velocity between the microwave and the light wave and further to maintain strength of the substrates.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. S64-18121

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-215519

[0008] In the Patent Document 1 or 2, LiNbO₃ is mainly used for the first substrate, and material with a lower permittivity than LN, such as quartz, glass, alumina or the like is used for the second substrate. A temperature drift or a DC drift accompanied by a temperature variation occurs in a combination of such material by a difference of a coefficient of linear expansion therebetween. Patent Document 2 discloses that, in order to remove such inconvenience, the bonding of the first substrate and the second substrate is performed by use of an adhesive with a coefficient of linear expansion close to the first substrate.

[0009] However, comparing a modulator using the LN substrate which has been manufactured conventionally with a modulator to make the LN substrate thin, as the substrate becomes thinner, light emitted or leaked from the optical waveguide, or light and the like incident on other than the optical waveguide from an optical fiber for incidence (hereinafter, such light is referred to as "faint light.") has a strong tendency to be confined within the substrates. In the conventional LN substrate, since the substrate is thick (e.g., 500 µm to 1000µm), there are sufficient areas which do not influence the waveguide (e.g., several µm in depth) and a spatial distribution density of light filled with the faint light (hereinafter, referred to as "faint light density") becomes lower. As a result, the faint light has little impact. However, when a thickness of the substrate is the same as a distance in a depth direction of the waveguide, since a faint light density propagating in a direction parallel to a surface of the substrate within the substrate becomes higher, the faint light propagates within the substrate to be re-incident on the optical waveguide or to be incident on an optical fiber for output connected to a light modulation device, resulting in deteriorating a S/N ratio of output light.

[0010] In addition, when a thin substrate is used for a light modulation device, since the thin substrate cannot give a sufficient strength, the thin substrate which is the first substrate and the second substrate are required to be bonded by a supplementing plate by use of an adhesive. In this case, when a refractive of the adhesive is lower than that of the thin substrate, the confinement of the faint light is more outstanding. For this reason, this applicant has proposed in Patent Document 3 that a light absorbing portion, a high refractive portion, a light guide portion or a concave portion is formed in an area excluding the optical waveguide and a periphery thereof in the thin substrate, to remove the faint light within the thin substrate.

[0011] Patent Document 3: Japanese Patent Application No. 2005-96447 (Application Date: March 29, 2005)

[0012] However, like Patent Document 2, there is a problem in that, when a surface, which is opposite to the thin substrate, of a adhesive layer of the supplanting plate is smoothed, the faint light emitted to other than the optical waveguide is reflected on the surface of the supplementing plate to be re-incident on the thin substrate, thereby recombining with the optical waveguide.

[0013] A light modulation device as defined in the preambles of claims 1 and 3 is disclosed in EP 1 455 219 A1.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] The present invention is directed to solve such problems and to provide a light modulation device capable of not only restricting the faint light propagating in the adhesive layer from being re-incident on the thin substrate but also increasing an adhesive strength of the thin substrate and the supplementing plate.

MEANS FOR SOLVING THE PROBLEM

[0015] For solving such problems, the invention provides a light modulation device according to claim 1.

[0016] According to one embodiment of the invention as claimed in claim 1, the bonding surface of the supplementing plate is formed as a concavo-convex structure.

[0017] This embodiment as claimed in claim 2 is further restricted by the feature that the height of a convex of the concavo-convex structure is over 1/10 of the predetermined wavelength of the faint signal light propagating in the adhesive layer.

[0018] The invention further provides a light modulation device according to claim 3.

[0019] The invention according to claim 4 is further restricted by the feature that, in the light modulation device according to anyone of claims 1 to 3, the optical waveguide is set such that the propagation constant for signal light of said given predetermined wavelength propagating in the optical waveguide differs in subsequent parts of the optical waveguide.

EFFECTS OF THE INVENTION

[0020] According to the invention related to claim 1, since, in a light modulation device having a thin substrate made of material with an electro-optical effect and with a thickness of below 20 µm; an optical waveguide formed on a surface of the thin substrate or the other surface thereof; and a modulation electrode formed on the surface of the thin substrate and for modulating light passing through the optical waveguide, which comprises a supplementing plate adapted to be bonded to the thin substrate via an adhesive layer, wherein a bonding surface of the supplementing plate is formed as a rough surface relative to a bonding surface of the thin substrate, it is possible to scatter faint light incident on the adhesive layer from the thin substrate on the rough surface of the bonding surface of the supplementing plate, to restrict the faint light from being re-incident on the thin substrate from the adhesive layer. Furthermore, since the bonding surface of the supplementing plate is formed as the rough surface, a contact area with the adhesive layer can be increased, to increase an adhesive strength of the thin substrate and the supplementing plate.

[0021] Since a roughness of the rough surface is over 1/10 of a wavelength of faint light propagating in the adhesive layer, the faint light can be scattered on the bonding surface of the supplementing plate effectively.

[0022] According to the invention related to claim 2, since a bonding surface of the supplementing plate is formed as a concave-convex structure, a contact area with the adhesive layer can be increased, to increase an adhesive strength of the thin substrate and the supplementing plate.

[0023] Since a height of a convex of the concavo-convex structure is over 1/10 of a wavelength of faint light propagating in the adhesive layer, the faint light can be scattered on the bonding surface of the supplementing plate effectively.

[0024] According to the invention related to claim 3, since, in a light modulation device having a thin substrate made of material with an electro-optical effect and with a thickness of below 20µm; an optical waveguide formed on a surface of the thin substrate or the other surface thereof; and a modulation electrode formed on the surface of the thin substrate and for modulating light passing through the optical waveguide, which comprises a supplementing plate adapted to be bonded to the thin substrate via an adhesive layer, wherein a bonding surface of the supplementing plate is formed as a inclined surface which is inclined with respect to a bonding surface of the thin substrate, faint light incident on the adhesive layer from the thin substrate is reflected on the inclined surface to be changed towards other than thin substrate in a direction thereof, thereby restricting the faint light from being re-incident on the thin substrate or the optical waveguide from the adhesive layer.
In addition, since the bonding surface of the supplementing plate is formed as the inclined surface, a contact area with the adhesive layer can be increased, to increase an adhesive strength of the thin substrate and the supplementing plate.

[0025] According to the invention related to claim 4, since the optical waveguide is set such that a propagation constant of a light wave propagating in the optical waveguide differs partially, the effect of removing the faint light from the supplementing plate together with the effect of preventing the recombination of the faint light by adjustment of the propagation constant can prevent the faint light from recombining with the optical waveguide more effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 

Fig. 1 is a sectional view to illustrate an embodiment 1 related to a light modulation device of the present invention;

Fig. 2 is a sectional view to illustrate an embodiment 2 related to a light modulation device of the present invention; and

Fig. 3 is a sectional view to illustrate an embodiment 3 related to a light modulation device of the present invention.

DESCRIPTION OF REFERENCE NUMERALS

[0027] 

1: THIN SUBSTRATE

2: OPTICAL WAVEGUIDE

3: MODULATION ELECTRODE

4: ADHESIVE LAYER

5: SUPPLEMENTING PLATE

10: ROUGH SURFACE

11: CONCAVO-CONVEX STRUCTURE

12: INCLINED SURFACE

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0028] Hereinafter, embodiments of the present invention will be described using suitable examples.

[0029] Fig. 1 illustrates an embodiment 1 related to a light modulation device of the present invention. Fig. 1 is a sectional view of the light modulation device, which includes a thin substrate 1 with a thickness of below 20 µm and made of material with an electro-optical effect, an optical waveguide 2 formed on a surface of the thin substrate, and a modulation electrode 3 for modulating light passing through the optical waveguide. In addition, the optical waveguide 2 may be formed on the other surface of the thin substrate 1.

[0030] Furthermore, the thin substrate 1 is bonded to a supplementing plate 5 via an adhesive 4.

[0031] The optical waveguide 2 may be formed by diffusing Ti or the like on a surface of the substrate, using a thermal diffusion method or a proton exchanging method. In addition, like that disclosed in Patent Document 4, the optical waveguide may be configured by forming a ridge on the surface of the thin substrate 1 fitting to a shape of the optical waveguide.

[0032] The modulation electrode 3 such as a signal electrode or a ground electrode may be formed by formation of electrode pattern of Ti/Au, a gold-plate method and the like. Moreover, if necessary, a buffer layer (not shown) of a dielectric such as SiO₂ may be provided on the surface of the substrate after formation of the optical waveguide, to form the modulation electrode on the buffer layer.

[0033] Patent Document 4: Japanese Patent Application Laid-Open No. H6-289341

[0034] As material with an electro-optical effect, for example, lithium niobate, lithium tantalite, PLZT (lead zirconate titanate), quartz-based material, and a combination thereof are available. In particular, the lithium niobate (LN) crystal with high electro-optical effect is employed suitably.

[0035] According to a method of manufacturing the thin substrate 1 including the light modulation device, the above-described optical waveguide is formed on a substrate with a thickness of several hundreds µm, and the other surface of the substrate is grinded to create a thin substrate with a thickness of below 20µm. Then, the modulation electrode is formed on the surface of the thin substrate. In addition, the other surface of the substrate may be grinded after formation of the optical waveguide or the modulation electrode. Further, since the thin substrate is in danger of destruction due to a thermal impact upon formation of the optical waveguide or a mechanical impact according to handling of the thin substrate upon various processes, a process where such thermal or mechanical impact is applied thereto easily is preferably performed before making the substrate thin by grinding.

[0036] As material used for the supplementing plate 5, various kinds of material are available, for example, in addition to use of material identical to the thin substrate, material with a lower permittivity than the thin substrate, such as quartz, glass, alumina and so on may be used, or material with a crystalline orientation different from the thin substrate may be used like that disclosed in Patent Document 4. However, selection of material with coefficient of linear expansion identical to the thin substrate is preferably in stabilizing a modulation characteristic of the light modulation device relative to a temperature variation. If it is difficult to select material identical thereto, an adhesive for bonding the thin substrate and the supplementing plate is selected as material with a coefficient of linear expansion identical to the thin substrate as disclosed in patent document2.

[0037] For the bonding of the thin substrate 1 and the supplementing plate 5, various kinds of adhesive material, for example, an epoxy based adhesive, a thermosetting adhesive, an ultraviolet thermosetting adhesive, solder glass, or, a thermosetting, a photo curable or a light-increasing-viscosity resin adhesive sheet or the like may be used as the adhesive 4.

[0038] In the light modulation device as shown in Fig. 1, faint light occurs in the thin substrate other than the optical waveguide from a light splitter or a light summer of the optical waveguide formed in the thin substrate, or from a bonding portion of an optical fiber for incidence and the light modulation device. In addition, when a thickness of the thin substrate is thin, and, in particular, the thickness thereof is set to below 20µm, a problem is easy to happen that the faint light propagates in the thin substrate to be incident on the optical waveguide or an optical fiber for output. Especially, a main object of the present invention is to prevent a light wave incident on the adhesive layer from the thin substrate 1 from being incident on the thin substrate back to recombine with the optical waveguide and so on.

[0039] In order to prevent the light wave propagating in the adhesive layer 4 from being re-incident on the thin substrate 1, in the light modulation device of the present invention, a bonding surface where the supplementing plate 5 is bonded to the thin substrate 1 is formed as a rough surface 10 compared with a bonding surface (a lower surface of the thin substrate 1 in Fig. 1) of the thin substrate 1, as shown in Fig. 1. The formation of the rough surface 10 scatters the faint light in the adhesive layer on the rough surface to restrict the faint light from being re-incident on the thin substrate 1. Furthermore, since the bonding surface of the supplementing plate is formed as the rough surface, a contact area with the adhesive layer can be increased, to increase an adhesive strength of the thin substrate and the supplementing plate.

[0040] In addition, the rough surface extends in a transverse direction as well as in a direction vertical to a sectional surface in Fig. 1.

[0041] Since the rough surface 10 is required to serve as a scattering surface for the faint light, a roughness d1 of the corresponding rough surface preferably has a value of over 1/10 (λ/10) relative to a wavelength λ of the faint light propagating in the adhesive layer.

[0042] If the roughness of the rough surface is lower than λ /10, the faint light cannot be scattered effectively.

[0043] Subsequently, an embodiment 2 related to the light modulation device of the present invention will be described.

[0044] Fig. 2 is a diagram to illustrate the embodiment 2 of the light modulation device, in which like reference numerals are used for like elements in Fig. 1.

[0045] A characteristic of the embodiment 2 is that a bonding surface where the supplementing plate 5 is bonded to the thin substrate 1 is formed as a concavo-convex structure 11.

[0046] The formation of the concavo-convex structure 11 scatters the faint light in the adhesive layer on the concavo-convex structure to restrict the faint light from being re-incident on the thin substrate 1. In addition, since the bonding surface of the supplementing plate is formed as the concavo-convex structure, a contact area with the adhesive layer can be increased, to increase an adhesive strength of the thin substrate and the supplementing plate.

[0047] In addition, the concavo-convex structure extends in a transverse direction as well as in a direction vertical to a sectional surface in Fig. 2.

[0048] Since the concavo-convex structure 11 is also required to serve as a scattering surface for the faint light like the rough surface 10 in Fig. 1, a height d2 of the convex of the corresponding concavo-convex structure 11 preferably has a value of over 1/10 (λ/10) relative to a wavelength λ of the faint light propagating in the adhesive layer.

[0049] If the height of the convex is lower than λ/10, the faint light cannot be scattered effectively.

[0050] Successively, an embodiment 3 related to the light modulation device of the present invention will be described.

[0051] Fig. 3 is a diagram to illustrate the embodiment 3 of the light modulation device, in which like reference numerals are used for like elements in Figs. 1 and 2.

[0052] A characteristic of the embodiment 3 is that a bonding surface where the supplementing plate 5 is bonded to the thin substrate 1 is formed as an inclined surface 12 which is inclined with respect to the thin substrate 1, particularly, a bonding surface (a lower surface of the thin substrate 1 in Fig. 3) of the thin substrate 1.

[0053] By the formation of the inclined surface 12, the faint light in the adhesive layer is reflected on the inclined surface 12 to be changed towards other than thin substrate 1 in a direction thereof, thereby restricting the faint light from being re-incident on the thin substrate 1.

[0054] In addition, since the bonding surface of the supplementing plate is formed as the inclined surface, a contact area with the adhesive layer can be increased, to increase an adhesive strength of the thin substrate and the supplementing plate.

[0055] Although the shape of the inclined surface 12 is represented to be inclined by an inclined angle δ with respect to the thin substrate 1 within a plane vertical to a propagation direction of the light wave in the optical waveguide 2 in Fig. 3, the present invention is not limited thereto, but it may be configured so that the inclined surface is inclined with respect to the thin substrate 1 within a plane parallel to a propagation direction of the light wave in the optical waveguide.

[0056] In addition, the inclined surface 12 which is inclined in a predetermined direction only with respect to the bonding surface of the thin substrate 1 is possible as shown in Fig. 3 as well as a mountain-shape inclined surface which is lowered in a height thereof as goes to left and right from the center of Fig. 3 is possible.

[0057] A value of the inclined angle δ of the inclined surface 12 may be set to any value, if the value is in a range where most of the faint light reflected on the bonding surface of the supplementing plate is not incident on the thin substrate 1 or the optical waveguide 2.

[0058] As illustrated in the embodiments 1 to 3 related to the light modulation device of the present invention, the shape of the bonding surface of the supplementing plate 5 is largely different from the shape of the bonding surface of the thin substrate 1 which is bonded thereto via the same adhesive layer. For this reason, when the supplementing plate 5 is transformed by a thermal expansion, a thermal stress from the supplementing plate 5 may be in danger of local concentration without uniform application to the thin substrate 1. Such concentration of the thermal stress is a cause to deteriorate optical characteristics of the light modulation device.

[0059] Therefore, a thickness of the adhesive layer is preferably over 10µm in order to mitigate the thermal stress from the supplementing plate 5.

[0060] In addition, in the light modulation device of the present invention, even if the faint light is re-incident on the thin substrate from the adhesive layer, the optical waveguide is designed and adjusted so that a propagation constant of the light wave propagating in the optical waveguide differs partially, to restrict recombination of the faint light and the optical waveguide as disclosed in Patent Document 5. In this way, the effect of removing the faint light from the supplementing plate according to the embodiments 1 to 3 together with the effect of preventing the recombination of the faint light by adjustment of the propagation constant can prevent the faint light from recombining with the optical waveguide more effectively.

[0061] As a method of adjusting the propagation constant, there is a method of adjusting a width of the optical waveguide or a method of diffusing or loading material for changing a propagation constant, for example, MgO, SiO₂, TiO₂ or ZnO on the optical waveguide or a periphery thereof, and this changes a refractive of the optical waveguide.

[0062] Patent Document 5: Japanese Patent Application No. 2005-101307 (Application date: March 31, 2005)

INDUSTRIAL APPLICABILITY

[0063] As described above, according to the present invention, it is possible to provide a light modulation device capable of not only preventing faint light propagating in an adhesive layer from being re-incident on a thin substrate but also increasing an adhesive strength between the thin substrate and a supplementing plate.

Claims

1. A light modulation device having a thin substrate (1) of a thickness below 20 µm; made of material with an electro-optical effect; an optical waveguide (2) formed on one of the major surfaces of the thin substrate (1); a modulation electrode (3) formed on a major surface of the thin substrate (1) and being arranged to modulate signal light of a predetermined wavelength passing through the optical waveguide (2),
and a supplementing plate (5) bonded to the thin substrate (1) via an adhesive layer (4),
characterized in that
the bonding surface of the supplementing plate (5) is formed as a rough surface (10) relative to the bonding surface of the thin substrate (1);
wherein the rough surface (10) is adapted to scatter faint signal light propagating in the adhesive layer (4) in order to restrict the faint signal light from being re-incident on the thin substrate (1) and
wherein the roughness of the rough surface (10) is over 1/10 of the predetermined wavelength of faint signal light propagating in the adhesive layer (4).

2. The light modulation device according to claim 1, wherein the bonding surface of the supplementing plate (5) is formed as a concavo-convex structure (11) and the height of a convex of the concavo-convex structure (11) is over 1/10 of the predetermined wavelength of the faint signal light propagating in the adhesive layer (4).

3. A light modulation device having a thin substrate (1) of a thickness below 20 µm made of material with an electro-optical effect; an optical waveguide (2) formed on one of the major surfaces of the thin substrate (1); a modulation electrode (3) formed on a major surface of the thin substrate (1) and being arranged to modulate signal light of a predetermined wavelength passing through the optical waveguide (2),
and a supplementing plate (5) bonded to the thin
substrate (1) via an adhesive layer (4),
characterized in that
the bonding surface of the supplementing plate (5) is formed as an inclined surface (12) which is inclined with respect to the bonding surface of the thin substrate (1);
wherein the inclined surface (12) is arranged such that faint signal light propagating in the adhesive layer (4) is reflected on the inclined surface (12) so as to restrict the faint signal light from being re-incident on the thin substrate (1).

4. The light modulation device according to any one of claims 1 to 3, wherein the optical waveguide (2) is set such that the propagation constant for signal light of said given predetermined wavelength propagating in the optical waveguide differs in subsequent parts of the optical waveguide.

Ansprüche

1. Lichtmodulationsvorrichtung mit einem dünnen Substrat (1) mit einer Dicke von weniger als 20 µm, gefertigt aus einem Material mit einer elektrooptischen Wirkung; einem optischen Wellenleiter (2), der auf einer der größeren/Haupt-Oberflächen des dünnen Substrats (1) gebildet ist; einer Modulationselektrode (3), die auf einer größeren/Haupt-Oberfläche des dünnen Substrats (1) gebildet und so angeordnet ist, dass sie Signallicht einer vorbestimmten Wellenlänge moduliert, das durch den optischen Wellenleiter (2) hindurchgeht, und einer Zusatzplatte (5), die über eine Haftschicht (4) an das dünne Substrat (1) gebunden ist,
dadurch gekennzeichnet, dass
die Bindefläche der Zusatzplatte (5) als eine raue Oberfläche (10) in Bezug auf die Bindefläche des dünnen Substrats (1) gebildet ist;
wobei die raue Oberfläche (10) dazu geeignet ist, schwaches Signallicht, das sich in der Haftschicht (4) ausbreitet, zu streuen, um das schwache Signallicht derart zu beschränken, dass es auf dem dünnen Substrat (1) nicht erneut einfällt, und
wobei die Rauheit der rauen Oberfläche (10) über 1/10 der vorbestimmten Wellenlänge des schwachen Signallichts, das sich in der Haftschicht (4) ausbreitet, beträgt.

2. Lichtmodulationsvorrichtung nach Anspruch 1, wobei die Bindefläche der Zusatzplatte (5) als eine konkav-konvexe Struktur (11) gebildet ist und die Höhe einer Wölbung der konkav-konvexen Struktur (11) über 1/10 der vorbestimmten Wellenlänge von schwachem Signallicht, das sich in der Haftschicht (4) ausbreitet, beträgt.

3. Lichtmodulationsvorrichtung mit einem dünnen Substrat (1) mit einer Dicke von weniger als 20 µm, gefertigt aus einem Material mit einer elektrooptischen Wirkung; einem optischen Wellenleiter (2), der auf einer der größeren/Haupt-Oberflächen des dünnen Substrats (1) gebildet ist; einer Modulationselektrode (3), die auf einer größeren/Haupt-Oberfläche des dünnen Substrats (1) gebildet und so angeordnet ist, dass sie Signallicht einer vorbestimmten Wellenlänge moduliert, das durch den optischen Wellenleiter (2) hindurchgeht, und einer Zusatzplatte (5), die über eine Haftschicht (4) an das dünne Substrat (1) gebunden ist,
dadurch gekennzeichnet, dass
die Bindefläche der Zusatzplatte (5) als eine geneigte Oberfläche (12) gebildet ist, die in Bezug auf die Bindefläche des dünnen Substrats (1) geneigt ist;
wobei die geneigte Oberfläche (12) derart angeordnet ist, dass schwaches Signallicht, das sich in der Haftschicht (4) ausbreitet, auf der geneigten Oberfläche (12) reflektiert wird, um das schwache Signallicht so zu beschränken, dass es auf dem dünnen Substrat (1) nicht erneut einfällt.

4. Lichtmodulationsvorrichtung nach einem der Ansprüche 1 bis 3, wobei der optische Wellenleiter (2) so eingestellt ist, dass der Übertragungsfaktor für Signallicht der gegebenen vorbestimmten Wellenlänge, das sich in dem optischen Wellenleiter ausbreitet, in nachfolgenden Teilen des optischen Wellenleiters unterschiedlich ist.

Revendications

1. Dispositif de modulation lumineuse ayant un fin substrat (1) présentant une épaisseur en dessous de 20 µm constituée d'un matériau ayant un effet électro-optique, un guide d'ondes optiques (2) formé sur une des surfaces plus grandes/importantes du fin substrat (1), une électrode de modulation (3) formée sur une surface plus grande/importante du fin substrat (1) et étant conçue pour moduler le signal lumineux d'une longueur d'ondes prédéterminée passant à travers le guide d'ondes optiques (2), et une plaque de renforcement (5) collée au fin substrat (1) par l'intermédiaire d'une couche adhésive (4),
caractérisé par le fait que
la surface de collage de la plaque de renforcement (5) est formée en tant que surface rugueuse (10) par rapport à la surface de collage du fin substrat (1);
dans lequel la surface rugueuse (10) est prévue pour diffuser un faible signal lumineux se propageant dans la couche adhésive (4) afin de limiter le faible signal lumineux de revenir en incidence sur le fin substrat (1) et
dans lequel la rugosité de la surface rugueuse (10) représente plus d'1/10ème de la longueur d'ondes prédéterminée d'un faible signal lumineux se propageant dans la couche adhésive (4).

2. Dispositif de modulation lumineuse selon la revendication 1, dans lequel la surface de collage de la plaque de renforcement (5) est formée en tant que structure concavo-convexe (11) et la hauteur d'un convexe de la structure concavo-convexe (11) représente plus d'1/10ème de la longueur d'ondes prédéterminée du faible signal lumineux se propageant dans la couche adhésive (4).

3. Dispositif de modulation lumineuse ayant un fin substrat (1) d'une épaisseur située en dessous de 20 µm constituée d'un matériau ayant un effet électro-optique; un guide d'ondes optiques (2) formé sur une des surfaces plus grandes/importantes du fin substrat (1); une électrode de modulation (3) formée sur une surface plus grande/importante du fin substrat (1) et étant conçue pour moduler un signal lumineux d'une longueur d'ondes prédéterminée passant à travers le guide d'ondes optiques (2) ; et une plaque de renforcement (5) collée au fin substrat (1) par l'intermédiaire d'une couche adhésive (4),
caractérisé par le fait que
la surface de collage de la plaque de renforcement (5) est formée en tant que surface inclinée (12) qui est inclinée par rapport à la surface de collage du fin substrat (1);
dans lequel la surface inclinée (12) est conçue de telle sorte qu'un faible signal lumineux dans la couche adhésive (4) est réfléchi sur la surface inclinée (12) de manière à limiter le faible signal lumineux de revenir en incidence sur le fin substrat (1).

4. Dispositif de modulation lumineuse selon l'une quelconque des revendications 1 à 3, dans lequel le guide d'ondes optiques (2) est défini de telle sorte que la constante de propagation pour le signal lumineux de ladite longueur d'onde donnée prédéterminée se propageant dans le guide d'ondes optiques est différente dans les sections suivantes du guide d'ondes optiques.

Drawing