EP1031051A1 - Optical device with waveguide for transferring electromagnetic energy in the form of a radiation beam - Google Patents

Optical device with waveguide for transferring electromagnetic energy in the form of a radiation beam

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Publication number
EP1031051A1
EP1031051A1 EP98954523A EP98954523A EP1031051A1 EP 1031051 A1 EP1031051 A1 EP 1031051A1 EP 98954523 A EP98954523 A EP 98954523A EP 98954523 A EP98954523 A EP 98954523A EP 1031051 A1 EP1031051 A1 EP 1031051A1
Authority
EP
European Patent Office
Prior art keywords
waveguide
radiation
wavelength
polyhedra
material structure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98954523A
Other languages
German (de)
French (fr)
Inventor
Alain Dereux
Christian Girard
Jean-Pierre Goudonnet
Christian Joachim
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Universite de Bourgogne
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Universite de Bourgogne
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Filing date
Publication date
Application filed by Universite de Bourgogne filed Critical Universite de Bourgogne
Publication of EP1031051A1 publication Critical patent/EP1031051A1/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector

Definitions

  • the present invention relates to an optical waveguide device for the transfer of electromagnetic energy in the form of a radiation beam - in sub-wavelength regime.
  • optical waveguides which are used for the transport of information over a long distance by means of photon beams guided in optical fibers.
  • these optical devices must necessarily have rectilinear structures of great length relative to the propagated wavelength.
  • these optical waveguides have a relatively large maximum transverse dimension and when several of these waveguides are arranged in parallel, they must be sufficiently distant from each other to avoid any optical coupling between them. This leads to information transmission devices of considerable bulk.
  • the incident radiation that is to say penetrating through the entry face of the waveguide, must be aligned along the propagation axis defined by the material structure of the waveguide and it is obvious that this requirement is not always easy to meet.
  • the present invention aims to remedy these drawbacks by providing an optical device with waveguide of reduced transverse dimension and functioning perfectly even when the incoming incident radiation is not aligned along the propagation axis, the angle d incidence of the input beam can be even greater than the critical angle of total reflection.
  • this optical waveguide device for the transfer of electromagnetic energy in the form of a radiation beam whose wavelength can be within the range of visible light and near infrared radiation, comprising a waveguide extending between an input medium and an output medium, having a transparent material structure vis-à-vis the transmitted radiation and elongated in the direction of propagation of the radiation, is characterized in that the material structure of the waveguide has a maximum transverse dimension D D , in the plane of the incident radiation beam I, which is less than half the length d ⁇ wave of the incident beam, the material structure of the waveguide presents inhomogeneities from the point of view of the optical refractive index in the direction of propagation Z of the radiation and the transferred radiation is collected at a sub-micron distance from the exit face of the waveguide of the optical device.
  • the optical waveguide device offers numerous advantages compared to the waveguides known to date. Firstly, it makes it possible to carry out controlled propagation of electromagnetic radiation over very short, submicron distances. It also makes it possible to put very close optical guides in parallel without any phenomenon of optical coupling between them occurring.
  • optical device The practical applications that can be envisaged for the optical device according to the invention are numerous and varied. It can in particular be used, because the maximum transverse dimension of the material structure of the waveguide is less than half the incident wavelength, for the optical reading of compact discs with very high information density. In optoelectronics, it can also be used to establish a junction between two electronic components, without requiring precise alignment of these two components.
  • FIG. 1 is a sectional view of an optical device with waveguide according to the invention
  • - Figure 2 is a diagram illustrating the variation of the transmission or optical conductivity ratio of the waveguide according to the invention.
  • FIG. 3 is a view in vertical section of an alternative embodiment of an optical device with waveguide according to the invention.
  • FIG. 4 is a plan view of the optical device shown in FIG. 3.
  • an optical device comprising an optical waveguide 1 for the transfer of electromagnetic energy, in the form of radiation between an input medium 2 and an output medium 3 likewise refractive index.
  • the electromagnetic radiation to be transmitted from the input medium 2 to the output medium 3, through the waveguide 1, is introduced into the medium 2 at any angle relative to the axis of propagation Z of the radiation.
  • This propagation axis Z is the axis of the waveguide 1 and it is perpendicular to the exit face 2a of the entry medium 2 and to the entry face 3a of the exit medium 3.
  • the electromagnetic radiation having to be transmitted is shown in Figure 1, in the form of an incident beam I which is not necessarily aligned along the axis of propagation Z of the radiation and whose angle of incidence ⁇ 0 , that is to say say the angle it forms with the axis of propagation Z, may even be greater than the critical angle of total reflection.
  • the waveguide 1 has inhomogeneities from the point of view of the optical refractive index in the direction of propagation of the radiation, that is to say in the direction of the axis Z.
  • This succession of inhomogeneities can be obtained by means of polyhedra 4 (studs or blocks in the example of the drawing) dielectric, semiconductor or metallic, regularly spaced in the direction of the axis of propagation Z.
  • the polyhedra 4 are made of a material of which the real part of the dielectric function at the wavelength considered is negative separated from each other by spaces of material 5 of which the real part of the dielectric function at the wavelength considered is positive.
  • the polyhedra 4 can also be made of a material whose real part of the dielectric function at the wavelength considered is positive separated from one another by spaces of material 5 whose real part of the dielectric function at the wavelength considered is negative.
  • the maximum transverse dimension D 0 is less than half of the incident wavelength ⁇ of the radiation in air or vacuum.
  • the dimension D 0 has been chosen equal to 240 nm.
  • the distance between the blocks 4 has been chosen to be substantially equal to half of this effective wavelength, that is to say at 200 nm.
  • the thickness of the polyhedra 4, that is to say in the direction of the axis of propagation Z, is not in itself critical and it was taken equal to 240 nm.
  • the distance L 0 between the input 2 and output 3 media that is to say the length of the waveguide 1
  • the distance L 0 between the input 2 and output 3 media was chosen to be equal to 2440 nm, that is to say very greater than the wavelength ⁇ of the incident beam, so that the optical tunnel effect between the two input 2 and output 3 media is negligible to the point of being almost undetectable.
  • the normalized intensity T (or even transmission or optical conductivity ratio) is defined as being the modulus squared of the ratio between the amplitude E (z p ) of the electric field at the output of the optical device and more particularly at a point P of abscissa Z p on the axis Z and the amplitude E 0 of the field incident electric, that is to say of the incident beam I.
  • the normalized intensity T is defined as being the modulus squared of the ratio between the amplitude E (z p ) of the electric field at the output of the optical device and more particularly at a point P of abscissa Z p on the axis Z and the amplitude E 0 of the field incident electric, that is to say of the incident beam I.
  • the curve A in solid lines represents the variation of the ratio T in the case of the use of a waveguide 1 having a maximum transverse dimension D 0 equal to 240 nm
  • the dashed curve B corresponds to a waveguide 1 according to the invention having a transverse dimension D 0 equal to 180 nm
  • the dashed curve C corresponds to a waveguide 1 devoid of the aforementioned inhomogeneities, that is to say made continuously from one and the same material such as glass.
  • the transmission or optical conductivity ratio T is usually between 0 and 1 in conventional optics. Mathematically this ratio cannot exceed 1 if we take stock of the powers transmitted over long distances.
  • the waveguide according to the invention is also subject to this constraint and the amount of electromagnetic energy transmitted over a long distance is negligible.
  • the ratio T locally, in the near zone or in the field near the exit of the waveguide, that is to say at very short distance from the entry face 3a of the exit medium 3 (position of the point P in FIG. 1) nothing prevents the ratio T from becoming greater than unity. It is therefore possible that the ratio T becomes greater than 1 if Z p approaches L 0 as can be seen in Figure 2.
  • the implementation and operation of the optical device according to the invention requires a means of local detection of the optical electromagnetic field.
  • This detection means is located at point P at a sub-micron distance from the output of the waveguide 1, that is to say of the inlet face 3a of the outlet medium 3.
  • Figures 3 and 4 show an alternative embodiment of the optical device according to the invention in which the waveguide 1, consisting of the succession of polyhedra 4 located at a distance from each other, is- arranged on the upper surface d 'a substrate 6 whose real part of the dielectric function at the wavelength considered is significantly lower than that of the input medium 2 and the output medium 3.
  • the injection of the optical signal can be performed in an evanescent mode (not radiative).
  • the structure of the waveguide is periodic along the axis of propagation Z and the adjustment of the period or of the step p of the polyhedra 4 makes it possible to locate the maximum of the transmission curve (curve A of the Figure 2) in a domain of the optical or infrared spectrum defined beforehand.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Nanotechnology (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

The invention concerns an optical device with waveguide (1) for transferring electromagnetic energy in the form of a radiation beam (I) whose wavelength can be in the range of visible light and near infrared radiation, comprising a waveguide (1) extending between an input medium (2) and an output medium (3), having a material transparent structure with respect to the transmitted radiation and elongated in the radiation propagation direction (Z). The invention is characterised in that the waveguide (1) material structure has a maximum transverse dimension (Do), in the incident radiation beam (I) plane, which is less than half the wavelength lambda of the incident beam (I), the waveguide (I) material structure has inhomogeneities in the optical refractive index in the radiation propagation direction (Z) and the transferred radiation is collected at a submicronic distance from the optical device waveguide (1) output surface (3<u>a</u>).

Description

DISPOSITIF OPTIQUE A GUIDE D'ONDES POUR LE TRANSFERT D'ENERGIE ELECTROMAGNETIQUE SOUS FORME D'UN FAISCEAU DE WAVEGUIDED OPTICAL DEVICE FOR TRANSFERRING ELECTROMAGNETIC ENERGY IN THE FORM OF A BEAM
RAYONNEMENTRADIATION
La présente invention concerne un dispositif optique à guide d'ondes pour le transfert d'énergie électromagnétique sous forme d'un faisceau de rayonnement- en régime sub-longueur d'onde. On connaît déjà des guides d'ondes optiques qui sont utilisés pour le transport d'informations à grande distance au moyen de faisceaux de photons guidés dans des fibres optiques. Pour avoir des conditions de propagation bien nettes, ces dispositifs optiques doivent avoir nécessairement des structures rectilignés de grande longueur par rapport à la longueur d'onde propagée. Par ailleurs, ces guides d'ondes optiques ont une dimension transversale maximale relativement importante et lorsque plusieurs de ces guides d'ondes sont disposés en parallèle, ils doivent être suffisamment éloignés les uns des autres pour éviter tout couplage optique entre eux. Ceci conduit à des dispositifs de transmission d'informations d'un encombrement notable.The present invention relates to an optical waveguide device for the transfer of electromagnetic energy in the form of a radiation beam - in sub-wavelength regime. There are already known optical waveguides which are used for the transport of information over a long distance by means of photon beams guided in optical fibers. To have very clear propagation conditions, these optical devices must necessarily have rectilinear structures of great length relative to the propagated wavelength. Furthermore, these optical waveguides have a relatively large maximum transverse dimension and when several of these waveguides are arranged in parallel, they must be sufficiently distant from each other to avoid any optical coupling between them. This leads to information transmission devices of considerable bulk.
En outre, pour que ces guides d'ondes optiques connus puissent fonctionner d'une manière satisfaisante, le rayonnement incident, c'est-à-dire pénétrant à travers la face d'entrée du guide d'ondes, doit être aligné suivant l'axe de propagation défini par la structure matérielle du guide d'ondes et il est évident que cette exigence n'est pas toujours facile à respecter.In addition, for these known optical waveguides to be able to function satisfactorily, the incident radiation, that is to say penetrating through the entry face of the waveguide, must be aligned along the propagation axis defined by the material structure of the waveguide and it is obvious that this requirement is not always easy to meet.
La présente invention vise à remédier à ces inconvénients en procurant un dispositif optique à guide d'ondes de dimension transversale réduite et fonctionnant parfaitement même lorsque le rayonnement incident d'entrée n'est pas aligné suivant l'axe de propagation, l'angle d'incidence du faisceau d'entrée pouvant être même supérieur à l'angle critique de réflexion totale.The present invention aims to remedy these drawbacks by providing an optical device with waveguide of reduced transverse dimension and functioning perfectly even when the incoming incident radiation is not aligned along the propagation axis, the angle d incidence of the input beam can be even greater than the critical angle of total reflection.
A cet effet, ce dispositif optique à guide d'ondes pour le transfert d'énergie électromagnétique sous la forme d'un faisceau de rayonnement dont la longueur d'onde peut être comprise dans la plage de la lumière visible et du rayonnement infrarouge proche, comportant un guide d'ondes s ' étendant entre un milieu d'entrée et un milieu de sortie, ayant une structure matérielle transparente vis-à-vis du rayonnement transmis et allongé dans le sens de propagation du rayonnement, est caractérisé en ce que la structure matérielle du guide d'ondes a une dimension transversale maximale DD, dans le plan du faisceau de rayonnement incident I, qui est inférieure à la moitié de la longueur d'onde λ du faisceau incident, la structure matérielle du guide d'ondes présente des inhomogénéités du point de vue de 1 ' indice de réfraction optique dans le sens de propagation Z du rayonnement et le rayonnement transféré est recueilli à une distance sub-micronique de la face de sortie du guide d'ondes du dispositif optique.To this end, this optical waveguide device for the transfer of electromagnetic energy in the form of a radiation beam whose wavelength can be within the range of visible light and near infrared radiation, comprising a waveguide extending between an input medium and an output medium, having a transparent material structure vis-à-vis the transmitted radiation and elongated in the direction of propagation of the radiation, is characterized in that the material structure of the waveguide has a maximum transverse dimension D D , in the plane of the incident radiation beam I, which is less than half the length d λ wave of the incident beam, the material structure of the waveguide presents inhomogeneities from the point of view of the optical refractive index in the direction of propagation Z of the radiation and the transferred radiation is collected at a sub-micron distance from the exit face of the waveguide of the optical device.
Le dispositif optique à guide d'ondes suivant l'invention offre de nombreux avantages par rapport aux guides d'ondes connus à ce jour. En premier lieu, il permet de réaliser des propagations contrôlées d'un rayonnement électromagnétique sur des distances très courtes, sub- microniques . Il permet également de mettre en parallèle des guides optiques très rapprochés sans qu'intervienne un phénomène de couplage optique entre eux.The optical waveguide device according to the invention offers numerous advantages compared to the waveguides known to date. Firstly, it makes it possible to carry out controlled propagation of electromagnetic radiation over very short, submicron distances. It also makes it possible to put very close optical guides in parallel without any phenomenon of optical coupling between them occurring.
Les applications pratiques envisageables pour le dispositif optique suivant l'invention sont nombreuses et variées. Il peut notamment être utilisé, du fait que la dimension transversale maximale de la structure matérielle du guide d'ondes est inférieure à la moitié de la longueur d'onde incidente, pour la lecture optique de disques compacts à très haute densité d'informations. En optoélectronique, il peut être également employé pour établir une jonction entre deux composants électroniques, sans exiger un alignement précis de ces deux composants.The practical applications that can be envisaged for the optical device according to the invention are numerous and varied. It can in particular be used, because the maximum transverse dimension of the material structure of the waveguide is less than half the incident wavelength, for the optical reading of compact discs with very high information density. In optoelectronics, it can also be used to establish a junction between two electronic components, without requiring precise alignment of these two components.
On décrira ci -après, à titre d'exemples non limitatifs, diverses formes d'exécution de la présente invention en référence aux dessins annexés sur lesquels :Various embodiments of the present invention will be described below, by way of non-limiting examples, with reference to the appended drawings in which:
- la figure 1 est une vue en coupe d'un dispositif optique à guide d'ondes suivant l'invention, - la figure 2 est un diagramme illustrant la variation du rapport de transmission ou de conductivité optique du guide d'ondes suivant l'invention.FIG. 1 is a sectional view of an optical device with waveguide according to the invention, - Figure 2 is a diagram illustrating the variation of the transmission or optical conductivity ratio of the waveguide according to the invention.
- la figure 3 est une vue en coupe verticale d'une variante d'exécution d'un dispositif optique à guide d'ondes suivant l'invention,FIG. 3 is a view in vertical section of an alternative embodiment of an optical device with waveguide according to the invention,
- la figure 4 est une vue en plan du dispositif optique représenté sur la figure 3.FIG. 4 is a plan view of the optical device shown in FIG. 3.
Sur la figure 1 est représenté un dispositif optique suivant l'invention comportant un guide d'ondes optique 1 pour le transfert d'énergie électromagnétique, sous forme d'un rayonnement entre un milieu d'entrée 2 et un milieu de sortie 3 de même indice de réfraction. Le rayonnement électromagnétique devant être transmis du milieu d'entrée 2 au milieu de sortie 3, à travers le guide d'ondes 1, est introduit dans le milieu 2 suivant un angle quelconque par rapport à l'axe de propagation Z du rayonnement. Cet axe de propagation Z est l'axe du guide d'ondes 1 et il est perpendiculaire à la face de sortie 2a du milieu d'entrée 2 et à la face d'entrée 3a du milieu de sortie 3. Le rayonnement électromagnétique devant être transmis est représenté sur la figure 1, sous la forme d'un faisceau incident I qui n'est pas forcément aligné suivant l'axe de propagation Z du rayonnement et dont l'angle d'incidence θ0, c'est-à-dire l'angle qu'il forme avec l'axe de propagation Z, peut même être supérieur à l'angle critique de réflexion totale. Suivant l'invention, le guide d'ondes 1 présente dans le sens de propagation du rayonnement, c'est-à-dire dans la direction de l'axe Z, des inhomogénéités du point de vue de 1 ' indice de réfraction optique. Cette succession d ' inhomogénéités peut être obtenue au moyen de polyèdres 4 (des plots ou pavés dans l'exemple du dessin) diélectriques, semi-conducteurs ou métalliques, espacés régulièrement dans le sens de l'axe de propagation Z. Ces polyèdres sont séparés les uns des autres par des interstices ou volumes d'un autre matériau 5. Dans une forme d'exécution de l'invention, les polyèdres 4 sont en un matériau dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est négative séparés les uns des autres par des espaces de matériau 5 dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est positive. Suivant une variante de réalisation les polyèdres 4 peuvent être aussi en un matériau dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est positive séparés les uns des autres par des espaces de matériau 5 dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est négative. Suivant l'une des caractéristiques du guide d'ondes 1 la dimension transversale maximale D0 est inférieure à la moitié de la longueur d'onde incidente λ du rayonnement dans l'air ou le vide. Dans un mode de réalisation pratique dans lequel cette longueur d'onde λ est égale à 600 nm, la dimension D0 a été choisie égale à 240 nm. Les milieux d'entrée 2 et de sortie 3, ainsi que les interstices 5 du guide d'ondes 1 ont été réalisés en verre, d'indice de réfraction n = 1,5, et les polyèdres 4 ont la forme de pavés d'indice de réfraction n = 2,1. De ce fait la longueur d'onde effective dans le verre a été de 600 : 1,5 nm = 400 nm. La distance entre les pavés 4 a été choisie sensiblement égale à la moitié de cette longueur d'onde effective, c'est-à-dire à 200 nm. L'épaisseur des polyèdres 4, c'est-à-dire dans le sens de l'axe de propagation Z, n'est pas en elle-même critique et elle a été prise égale à 240 nm. Enfin, la distance L0 entre les milieux d'entrée 2 et de sortie 3, c'est-à-dire la longueur du guide d'ondes 1, a été choisie égale à 2440 nm, c'est-à- dire très supérieure à la longueur d'onde λ du faisceau incident, afin que l'effet tunnel optique entre les deux milieux d'entrée 2 et de sortie 3 soit négligeable au point d'être quasiment indétectable.In Figure 1 is shown an optical device according to the invention comprising an optical waveguide 1 for the transfer of electromagnetic energy, in the form of radiation between an input medium 2 and an output medium 3 likewise refractive index. The electromagnetic radiation to be transmitted from the input medium 2 to the output medium 3, through the waveguide 1, is introduced into the medium 2 at any angle relative to the axis of propagation Z of the radiation. This propagation axis Z is the axis of the waveguide 1 and it is perpendicular to the exit face 2a of the entry medium 2 and to the entry face 3a of the exit medium 3. The electromagnetic radiation having to be transmitted is shown in Figure 1, in the form of an incident beam I which is not necessarily aligned along the axis of propagation Z of the radiation and whose angle of incidence θ 0 , that is to say say the angle it forms with the axis of propagation Z, may even be greater than the critical angle of total reflection. According to the invention, the waveguide 1 has inhomogeneities from the point of view of the optical refractive index in the direction of propagation of the radiation, that is to say in the direction of the axis Z. This succession of inhomogeneities can be obtained by means of polyhedra 4 (studs or blocks in the example of the drawing) dielectric, semiconductor or metallic, regularly spaced in the direction of the axis of propagation Z. These polyhedra are separated from each other by interstices or volumes of another material 5. In one embodiment of the invention, the polyhedra 4 are made of a material of which the real part of the dielectric function at the wavelength considered is negative separated from each other by spaces of material 5 of which the real part of the dielectric function at the wavelength considered is positive. According to an alternative embodiment, the polyhedra 4 can also be made of a material whose real part of the dielectric function at the wavelength considered is positive separated from one another by spaces of material 5 whose real part of the dielectric function at the wavelength considered is negative. According to one of the characteristics of the waveguide 1, the maximum transverse dimension D 0 is less than half of the incident wavelength λ of the radiation in air or vacuum. In a practical embodiment in which this wavelength λ is equal to 600 nm, the dimension D 0 has been chosen equal to 240 nm. The input 2 and output 3 media, as well as the interstices 5 of the waveguide 1 were made of glass, with a refractive index n = 1.5, and the polyhedra 4 have the shape of blocks of refractive index n = 2.1. Therefore the effective wavelength in the glass was 600: 1.5 nm = 400 nm. The distance between the blocks 4 has been chosen to be substantially equal to half of this effective wavelength, that is to say at 200 nm. The thickness of the polyhedra 4, that is to say in the direction of the axis of propagation Z, is not in itself critical and it was taken equal to 240 nm. Finally, the distance L 0 between the input 2 and output 3 media, that is to say the length of the waveguide 1, was chosen to be equal to 2440 nm, that is to say very greater than the wavelength λ of the incident beam, so that the optical tunnel effect between the two input 2 and output 3 media is negligible to the point of being almost undetectable.
Sur la figure 2 sont représentées des courbes donnant la variation de l'intensité normalisée T du champ électromagnétique en fonction de la longueur d'onde λ du rayonnement. L'intensité normalisée T (ou encore rapport de transmission ou de conductivité optique) est définie comme étant le module au carré du rapport entre l'amplitude E(zp) du champ électrique à la sortie du dispositif optique et plus particulièrement en un point P d'abscisse Zp sur l'axe Z et l'amplitude E0 du champ électrique incident, c'est-à-dire du faisceau incident I. Sur le diagramme de la figure 2, la courbe A en trait plein représente la- variation du rapport T dans le cas de l'utilisation d'un guide d'ondes 1 ayant une dimension transversale maximale D0 égale à 240 nm, la courbe B en tirets correspond à un guide d'ondes 1 suivant l'invention ayant une dimension transversale D0 égale à 180 nm, et la courbe C en pointillés correspond à un guide d'ondes 1 dépourvu des inhomogénéités précitées, c'est-à-dire réalisé d'une manière continue en un seul et même matériau tel que le verre. Le rapport de transmission ou de conductivité optique T est habituellement compris entre 0 et 1 en optique classique. Mathématiquement ce rapport ne peut excéder 1 si l'on fait le bilan des puissances transmises à grande distance. Le guide d'ondes suivant l'invention est également soumis à cette contrainte et la quantité d'énergie électromagnétique transmise à grande distance est négligeable. Par contre, localement, dans la zone proche ou dans le champ proche de la sortie du guide d'ondes, c'est-à-dire à très courte distance de la face d'entrée 3a du milieu de sortie 3 (position du point P sur la figure 1) rien n'empêche que le rapport T devienne supérieur à l'unité. Il est donc possible que le rapport T devienne supérieur à 1 si Zp s'approche de L0 comme on peut le voir sur la figure 2.In FIG. 2 are shown curves giving the variation of the normalized intensity T of the electromagnetic field as a function of the wavelength λ of the radiation. The normalized intensity T (or even transmission or optical conductivity ratio) is defined as being the modulus squared of the ratio between the amplitude E (z p ) of the electric field at the output of the optical device and more particularly at a point P of abscissa Z p on the axis Z and the amplitude E 0 of the field incident electric, that is to say of the incident beam I. In the diagram of FIG. 2, the curve A in solid lines represents the variation of the ratio T in the case of the use of a waveguide 1 having a maximum transverse dimension D 0 equal to 240 nm, the dashed curve B corresponds to a waveguide 1 according to the invention having a transverse dimension D 0 equal to 180 nm, and the dashed curve C corresponds to a waveguide 1 devoid of the aforementioned inhomogeneities, that is to say made continuously from one and the same material such as glass. The transmission or optical conductivity ratio T is usually between 0 and 1 in conventional optics. Mathematically this ratio cannot exceed 1 if we take stock of the powers transmitted over long distances. The waveguide according to the invention is also subject to this constraint and the amount of electromagnetic energy transmitted over a long distance is negligible. On the other hand, locally, in the near zone or in the field near the exit of the waveguide, that is to say at very short distance from the entry face 3a of the exit medium 3 (position of the point P in FIG. 1) nothing prevents the ratio T from becoming greater than unity. It is therefore possible that the ratio T becomes greater than 1 if Z p approaches L 0 as can be seen in Figure 2.
La courbe A de variation du rapport T, pour une valeur de D0 = 240 nm, fait apparaître clairement une bande passante, appelée encore "résonance", de part et d'autre de la longueur d'onde de 600 nm pour laquelle un guide d'ondes continu (courbe C) est opaque.The curve A of variation of the ratio T, for a value of D 0 = 240 nm, clearly shows a bandwidth, also called "resonance", on either side of the wavelength of 600 nm for which a continuous waveguide (curve C) is opaque.
D'après ce qui précède on voit que la mise en oeuvre et l'exploitation du dispositif optique suivant l'invention exige un moyen de détection locale du champ électromagnétique optique. Ce moyen de détection est situé au point P à une distance sub-micronique de la sortie du guide d'ondes 1, c'est-à-dire de la face d'entrée 3a du milieu de sortie 3.From the above it can be seen that the implementation and operation of the optical device according to the invention requires a means of local detection of the optical electromagnetic field. This detection means is located at point P at a sub-micron distance from the output of the waveguide 1, that is to say of the inlet face 3a of the outlet medium 3.
Les figures 3 et 4 représentent une variante d'exécution du dispositif optique suivant l'invention dans laquelle le guide d'ondes 1, constitué de la succession de polyèdres 4 situés à distance les uns des autres, est- disposé sur la surface supérieure d'un substrat 6 dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est nettement inférieure à celles du milieu d'entrée 2 et du milieu de sortie 3. Avec une telle configuration, l'injection du signal optique peut être effectuée suivant un mode évanescent (non radiatif) . Comme précédemment, la structure du guide d'ondes est périodique le long de l'axe de propagation Z et l'ajustement de la période ou du pas p des polyèdres 4 permet de localiser le maximum de la courbe de transmission (courbe A de la figure 2) dans un domaine du spectre optique ou infrarouge défini au préalable. Figures 3 and 4 show an alternative embodiment of the optical device according to the invention in which the waveguide 1, consisting of the succession of polyhedra 4 located at a distance from each other, is- arranged on the upper surface d 'a substrate 6 whose real part of the dielectric function at the wavelength considered is significantly lower than that of the input medium 2 and the output medium 3. With such a configuration, the injection of the optical signal can be performed in an evanescent mode (not radiative). As before, the structure of the waveguide is periodic along the axis of propagation Z and the adjustment of the period or of the step p of the polyhedra 4 makes it possible to locate the maximum of the transmission curve (curve A of the Figure 2) in a domain of the optical or infrared spectrum defined beforehand.

Claims

REVENDICATIONS
1 - Dispositif optique à guide d'ondes (1) pour le transfert d'énergie électromagnétique sous la forme d'un faisceau de rayonnement (I) dont la longueur d'onde peut être comprise dans la plage de la lumière visible et du rayonnement infrarouge proche, comportant un guide d'ondes (1) s 'étendant entre un milieu d'entrée (2) et un milieu de sortie (3), ayant une structure matérielle transparente vis-à-vis du rayonnement transmis et allongé dans le sens de propagation du rayonnement (Z) , caractérisé en ce que la structure matérielle du guide d'ondes (1) a une dimension transversale maximale (D0) , dans le plan du faisceau de rayonnement incident (I), qui est inférieure à la moitié de la longueur d'onde λ du faisceau incident (I), la structure matérielle du guide d'ondes (1) présente des inhomogénéités du point de vue de 1 ' indice de réfraction optique dans le sens de propagation du rayonnement (Z) et le rayonnement transféré est recueilli à une distance sub- micronique de la face de sortie (3a) du guide d'ondes (1) du dispositif optique. 2 - Dispositif suivant la revendication 1 caractérisé en ce que la structure matérielle du guide d'ondes (1) est constituée d'une succession de polyèdres de matériau diélectrique (4) séparés régulièrement les uns des autres par des espaces d'air ambiant (5) ou de matériau diélectrique d'indice de réfraction inférieur à celui des polyèdres (4) .1 - Optical waveguide device (1) for the transfer of electromagnetic energy in the form of a radiation beam (I) whose wavelength can be included in the range of visible light and radiation near infrared, comprising a waveguide (1) extending between an input medium (2) and an output medium (3), having a transparent material structure vis-à-vis the transmitted radiation and elongated in the direction of propagation of the radiation (Z), characterized in that the material structure of the waveguide (1) has a maximum transverse dimension (D 0 ), in the plane of the incident radiation beam (I), which is less than half the wavelength λ of the incident beam (I), the material structure of the waveguide (1) exhibits inhomogeneities from the point of view of the optical refractive index in the direction of propagation of the radiation (Z ) and the transferred radiation is collected at a sub- micron of the output face (3a) of the waveguide (1) of the optical device. 2 - Device according to claim 1 characterized in that the material structure of the waveguide (1) consists of a succession of polyhedra of dielectric material (4) regularly separated from each other by ambient air spaces ( 5) or dielectric material with a refractive index lower than that of polyhedra (4).
3 - Dispositif suivant la revendication 1 caractérisé en ce que la structure matérielle du guide d'ondes (1) est constituée d'une succession de polyèdres (4) de matériau dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est négative séparés les uns des autres par des espaces de matériau (5) dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est positive. 4 - Dispositif suivant la revendication 1 caractérisé en ce que la structure matérielle du guide d'ondes (1) est constituée d'une succession de polyèdres (4) de matériau dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est positive séparés les uns des autres par des espaces de matériau (5) dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est négative.3 - Device according to claim 1 characterized in that the material structure of the waveguide (1) consists of a succession of polyhedra (4) of material including the real part of the dielectric function at the wavelength considered is negative separated from each other by spaces of material (5) whose real part of the dielectric function at the wavelength considered is positive. 4 - Device according to claim 1 characterized in that the material structure of the waveguide (1) consists of a succession of polyhedra (4) of material whose real part of the dielectric function at the considered wavelength is positive separated from each other by spaces of material (5) whose real part of the dielectric function at the wavelength considered is negative.
5 - Dispositif suivant l'une quelconque des revendications précédentes caractérisé en ce que les polyèdres (4) sont espacés les uns les autres d'une distance sensiblement égale à la moitié de la longueur d'onde effective du rayonnement dans les polyèdres (4) .5 - Device according to any one of the preceding claims, characterized in that the polyhedra (4) are spaced from each other by a distance substantially equal to half the effective wavelength of the radiation in the polyhedra (4) .
6 - Dispositif suivant l'une quelconque des revendications précédentes caractérisé en ce que le milieu d'entrée (2) et le milieu de sortie (3) ont un même indice de réfraction. 7 - Dispositif suivant l'une quelconque des revendications précédentes caractérisé en ce la structure matérielle du guide d'ondes (1) est formée sur un substrat (6) dont la partie réelle de la fonction diélectrique à la longueur d'onde considérée est nettement inférieure à celles du milieu d'entrée (2) et du milieu de sortie (3) . 6 - Device according to any one of the preceding claims, characterized in that the inlet medium (2) and the outlet medium (3) have the same refractive index. 7 - Device according to any one of the preceding claims, characterized in that the material structure of the waveguide (1) is formed on a substrate (6) whose real part of the dielectric function at the wavelength considered is clearly lower than those of the input medium (2) and the output medium (3).
EP98954523A 1997-11-10 1998-11-05 Optical device with waveguide for transferring electromagnetic energy in the form of a radiation beam Withdrawn EP1031051A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9714206A FR2770911B1 (en) 1997-11-10 1997-11-10 WAVEGUIDED OPTICAL DEVICE FOR TRANSFERRING ELECTROMAGNETIC ENERGY IN THE FORM OF A RADIATION BEAM
FR9714206 1997-11-10
PCT/FR1998/002367 WO1999024853A1 (en) 1997-11-10 1998-11-05 Optical device with waveguide for transferring electromagnetic energy in the form of a radiation beam

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US5577141A (en) * 1995-03-10 1996-11-19 Lucent Technologies Inc. Two-dimensional segmentation mode tapering for integrated optic waveguides

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