EP1576705A2 - Opto-electronic components with metal strip optical guidance - Google Patents

Opto-electronic components with metal strip optical guidance

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Publication number
EP1576705A2
EP1576705A2 EP03778379A EP03778379A EP1576705A2 EP 1576705 A2 EP1576705 A2 EP 1576705A2 EP 03778379 A EP03778379 A EP 03778379A EP 03778379 A EP03778379 A EP 03778379A EP 1576705 A2 EP1576705 A2 EP 1576705A2
Authority
EP
European Patent Office
Prior art keywords
component
multilayer heterostructure
deposit
metallic
optoelectronic component
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Withdrawn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
EP03778379A
Other languages
German (de)
French (fr)
Inventor
Jean-Yves Thales Intellectual Property BENGLOAN
Alfredo Thales Intellectual Property DE ROSSI
Carlo Thales Intellectual Property SIRTORI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thales SA
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Filing date
Publication date
Application filed by Thales SA filed Critical Thales SA
Publication of EP1576705A2 publication Critical patent/EP1576705A2/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Withdrawn legal-status Critical Current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
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0425—Electrodes, e.g. characterised by the structure
    • H01S5/04256—Electrodes, e.g. characterised by the structure characterised by the configuration
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/3401—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S2301/00—Functional characteristics
    • H01S2301/14—Semiconductor lasers with special structural design for lasing in a specific polarisation mode
    • H01S2301/145—TM polarisation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0425—Electrodes, e.g. characterised by the structure
    • H01S5/04254—Electrodes, e.g. characterised by the structure characterised by the shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/1046—Comprising interactions between photons and plasmons, e.g. by a corrugated surface
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
    • H01S5/1228—DFB lasers with a complex coupled grating, e.g. gain or loss coupling
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/34306—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength longer than 1000nm, e.g. InP based 1300 and 1500nm lasers

Definitions

  • the field of the invention is that of optoelectronic components with multilayer heterostructures, and in particular that of laser diodes emitting in transverse magnetic polarization, that is to say of which the electric emission field is polarized perpendicular to the plane of the layers of l heterostructure.
  • Multilayer electronic components mainly comprise an active area emitting in the middle or far infrared in magnetic transverse polarization, by exploiting, for example, the intersubband transitions of quantum wells (case of quantum cascade lasers called QCL).
  • This active area is between two layers called cladding layers.
  • the optical modes of propagation inside these layers also called dielectric modes are then characterized by an optical index noted effective index.
  • the confinement in a plane perpendicular to the plane of the layers of the optical mode is ensured by the index contrasts between each layer.
  • planar guide mode The confinement or the guidance of the mode in the plane of the layers is also necessary. In particular, it makes it possible to minimize the threshold current. This can only be obtained by local modification of the effective index of the planar mode of the layers.
  • etching is currently carried out by various known techniques such as, for example, ion beam etching with chemical assistance (CAIBE process for Chemical Assisted Ion Beam Etching) or reactive ion etching (RIE process for Reactive Ion Etching).
  • CAIBE process for Chemical Assisted Ion Beam Etching
  • RIE process reactive ion etching
  • the etching process can lead to a rough surface state, generating optical losses by diffusion.
  • Chemical etching reduces the roughness of the etched surfaces.
  • this process is difficult to master for structures of small dimensions, typically less than a micron, necessary for the components working in the mid infrared. Indeed, the chemical attack is selective and anisotropic and makes the reproducibility of the device difficult.
  • the object of the invention is to reduce these various problems associated with engraving while retaining a simple production method.
  • a polarized electromagnetic Transverse Magnetic wave can propagate in a guided way at the interface of a metal and a dielectric in the form of plasmon when the metal and the semiconductor have dielectric constants of opposite sign (P.Yeh, Optical Waves in Layered Media - Wiley, New-York, 1998).
  • this diode proves to be ineffective because, in this spectral range, the metal introduces significant losses.
  • the invention proposes to couple the surface plasmon and the dielectric mode of a planar dielectric guide so as to modulate the effective index of the dielectric mode in order to to obtain a resulting optical mode which is both guided and low loss.
  • This effect is obtained by depositing on the cladding layers of the optoelectronic component an upper zone of semiconductor material, then a metallic deposit on said zone, the optical thickness of the upper zone being chosen so as to obtain optimal coupling.
  • QCL type laser optical structures for example “Fabry-Pérot” type lasers, but also DFB (Distributed FeedBack) or ⁇ -DFB ( ⁇ -Distributed FeedBack) type lasers, ARROW (AntiResonant Reflecting Optical Waveguide) lasers or lasers based on photonic band gap cavities.
  • DFB Distributed FeedBack
  • ⁇ -DFB ⁇ -Distributed FeedBack
  • ARROW AntiResonant Reflecting Optical Waveguide
  • the shape of the metal deposit is simply adapted to each type of component.
  • the subject of the invention is an optoelectronic component with a multilayer heterostructure, successively comprising at least one substrate, an active area emitting in magnetic transverse polarization and an upper area made of semiconductor material, said component comprising an emission side face that is substantially perpendicular in the plane of the layers, and emitting by said lateral face an optical wave at a wavelength situated in the infrared, characterized in that said upper zone carries at least one metallic deposit and that the thickness of said upper zone is equal at a fraction of the emission wavelength, making it possible to have a resonance between on the one hand, a plasmonic surface mode linked to the metallic deposit and on the other hand a dielectric mode linked to the active area.
  • said metal deposit has the form of a metal strip.
  • said metallic deposit is composed of identical ribbons, parallel to each other and of direction parallel to the emission face.
  • said metallic deposit is composed of at least two identical sets of ribbons parallel to each other and of direction perpendicular to the lateral emission face.
  • said metallic deposit is composed of two identical sets of ribbons parallel to each other, the direction of said ribbons being inclined relative to the lateral emission face.
  • each of said sets of ribbons constitutes a Bragg mirror.
  • said metallic deposit is composed of a two-dimensional periodic pattern of metallic zones.
  • said pattern comprises at least one missing metallic zone.
  • the metal deposit has areas dedicated to the electrical connection.
  • the upper zone and the metal deposit comprises a layer of insulating material, said layer comprising sparing zones situated above the metal deposit, the electrical connection of the component being made at said level. savings zones.
  • the material of the insulating layer is preferably alumina.
  • the materials of the layers are based on gallium arsenide and aluminum (AlAsGa) or indium and aluminum phosphide (AlInP) or indium antimonide (InSb) or silicon-germanium alloys (SiGe) .
  • the metal of the deposit is gold or aluminum.
  • FIG. 1a and 1b show a perspective view and a top view of the device according to the invention in the case of a laser type "Fabry-Perot";
  • - Figure 2 shows, in the case of a QCL laser in
  • AIGaAs / GaAs the optical index profile of the different layers and the energy distribution of the dielectric optical mode as a function of this profile when the laser does not have a metallic deposit;
  • FIG. 3 represents, in the case of a QCL laser in AIGaAs / GaAS according to the invention, comprising an upper zone of thickness less than the thickness called resonance, the profile of optical index of the different layers and the energy distributions of the so-called “binder” and “anti-binder” optical modes;
  • FIG. 4 shows, in the case of a QCL laser in AIGaAs / GaAS according to the invention, comprising an upper zone of thickness equal to the thickness called resonance, the optical index profile of the different layers and the energy distributions of the coupled optical modes "binder” and "anti-binder”;
  • FIG. 5 represents, in the case of a QCL laser in AIGaAs / GaAS according to the invention, comprising an upper zone of thickness greater than the thickness called resonance, the optical index profile of the different layers and the energy distributions of the “binder” and “anti-binder” optical modes;
  • FIG. 7 shows the block diagram of a DFB type laser according to the invention
  • FIG. 8 shows the block diagram of an ARROW type laser according to the invention
  • FIG. 9 shows the block diagram of an ⁇ -DFB type laser according to the invention.
  • - Figure 10 shows the block diagram of a laser photonic band prohibited according to the invention
  • - Figure 11 shows a first arrangement of the electrical connection of the component
  • FIG. 12 shows a second arrangement of the electrical connection of the component.
  • FIGS 1a and 1b show the device according to the invention in the case of a QCL (Quantum Cascade Laser) type laser with "Fabry-Pérot" cavity.
  • a QCL type laser comprises a multilayer heterostructure 7 successively comprising a substrate 5, a first layer 42 in a first semiconductor material, a second layer 32 in a second semiconductor material, an active area 3, a third layer 31 identical to 32 , a fourth layer 41 identical to 42, an upper zone 2, said zone 2 being covered with a metallic strip 1, the optical index of the first material being lower than that of the second material.
  • the set of layers 3, 31 and 32 forms the heart of the waveguide of the laser cavity which emits an optical mode 6 from the face side 8.
  • the plane mirrors of the "Fabry-Pérot" cavity are formed on the one hand by the emission side face 8 and on the other hand by the face 80 opposite and parallel to said side face 8.
  • the plane of the layers is in a plane (x, y)
  • the lateral face 8 and the opposite face 80 in a plane (x, z)
  • the direction of the metallic strip and the direction of emission of the optical mode are parallel to the axis Oy.
  • the optical mode 6 is confined in the direction Oz by the index contrast existing between the layers 41, 42 and the layers 31 , 32. It is confined in the direction Ox by the variation in effective index introduced by the metallic strip 1.
  • the substrate is made of GaAs
  • the active area is based on indium antimonide
  • layers 31 and 32 are made of GaAs
  • layers 41 and 42 are made of AIGaAs
  • the upper zone 2 is also made of GaAs
  • the metallic deposit is, for example, of gold.
  • the optical index along the transverse axis Oz to the layers depends on the material and the thickness in microns of said layers. It is represented on the bottom curve of FIG. 2.
  • a dielectric optical mode can propagate inside the component, the energy distribution of this dielectric optical mode depending on the index profile is shown on the top curve of this same figure.
  • the energy distribution has a “Gaussian” appearance along the Oz axis. In the absence of metallic deposit, it is however not confined along the axis Ox.
  • the plasmonic wave arises at the interface of two materials whose dielectric constants are of opposite sign. Indeed, in the medium infrared, the optical frequency of the plasmonic mode being lower than the plasma frequency, the dielectric constant of the metal is negative while that of the upper zone is positive. The amplitude of this surface mode decreases exponentially in the two media along the Oz axis, normal at the interface between the two media. The losses of a plasmonic mode are significant. The loss coefficient is often greater than 50 cm "1 .
  • the dielectric mode is also of transverse magnetic polarization
  • these two modes can interact, the interaction depending on the geometric thickness of the upper zone.
  • the two modes couple to form two hybrid modes called "binder” and "anti-binder", these hybrid modes can be described as linear combinations of the modes in interaction.
  • the hybridization of the modes therefore makes it possible to obtain both a binder mode confined along the axis Ox in the zone of the component located under the deposit and also having low losses insofar as it is not purely plasmonic.
  • the bottom curve the index profile of the different layers along an Oz axis. The double bar indicates the limit between the upper zone and the metal. • The middle curve: the energy distribution (E.M.N.L.) of the mode
  • the bottom curve the index profile of the different layers along an Oz axis.
  • the optimum thickness of the upper layer is approximately 1 micron.
  • the middle curve the energy distribution (EMNL) of the “anti-binder” mode according to this same index profile.
  • the upper curve the energy distribution (E.M.L) of the “binder” mode as a function of this same index profile.
  • E.M.L the energy distribution of the “binder” mode as a function of this same index profile.
  • the three curves of FIG. 5 represent for an upper zone having a thickness of 2 microns greater than the optimal thickness:
  • the bottom curve the index profile of the different layers along an Oz axis.
  • the middle curve the energy distribution (E.M.N.L.) of the mode
  • the curve of figure 6 represents the variation of the effective index
  • Semiconductor lasers have longitudinal multimode operation. This multimodal character is very inconvenient for many applications (focusing of the beam, propagation in optical fibers, etc.). To remedy this, distributed feedback lasers of the DFB (Distributed FeedBack) type are produced.
  • the principle is to introduce a periodic modulation of the effective index in the direction of propagation of the beam and, therefore, to perform a very selective frequency filtering, similar to that of the Bragg mirror. It is thus possible to render a laser diode single mode.
  • the effective index modulation can be obtained by depositing metal strips according to the invention on the heterostructure of the component.
  • Figure 7 gives the block diagram of a device of this type.
  • a multilayer heterostructure 7 defined in an orthogonal coordinate system (O, x, y, z)
  • the plane of the layers is in a plane (x, y)
  • the metallic ribbons 1 parallel to one another are implanted on the following multilayer heterostructure 7 the direction Ox
  • the emission side face 8 of the mode is in a plane (x, z)
  • mode 6 is emitted by this side face in a direction Oy perpendicular to the direction of the metal strips 1.
  • This type of guide allows a good horizontal optical confinement in the planar wave guides (J. Gehler, A. Brâuer and W. Karthe: Antiresonant reflecting optical waveguides in strip configuration - Appl. Phys. Letters 64 (3), 17 january 1994).
  • the principle is to make two Bragg mirrors parallel to each other on the heterostructure, the emission mode being confined in the space between these two mirrors. Only one transverse optical mode is present in this structure whatever the size of this mode, which represents the main advantage of this guidance.
  • Each mirror can be obtained by depositing at least two ribbons according to the invention on the heterostructure as it is presented in FIG. 8.
  • a multilayer heterostructure 7 defined in an orthogonal coordinate system (O, x, y, z)
  • the plane of the layers is in a plane (x, y)
  • the metallic ribbons 1 constituting the Bragg mirrors are implanted on the multilayer heterostructure 7 in the direction Oy
  • the emission side face 8 of the mode is in a plane (x, z )
  • mode 6 is emitted by this lateral face in a direction Oy parallel to the direction of the metallic ribbons 1.
  • DFB technology In high power applications requiring a larger optical mode size, DFB technology is no longer suitable.
  • An ⁇ -DFB type laser is then produced.
  • the principle is to confine the optical mode in a guiding structure inclined relative to the lateral exit face (REBartolo, WWBewIey, INurgaftman, CLFelix, JRMeyer and MJYang, Appl. Phys. Lett. 76 (2000), 3164).
  • the modes then carry out a zigzag path by successive reflections on the Bragg mirrors of the guiding structure and only those which are normal to the exit face can oscillate. This clearly improves the spatial coherence and the temporal coherence of the mode.
  • the inclined guiding structure can be obtained as for an ARROW type guide by means of metallic ribbons deposited on the heterostructure of the component as indicated in FIG. 9.
  • the plane of the layers is in a plane (x, y)
  • the metallic ribbons 1 constituting the Bragg mirrors are implanted on the multilayer heterostructure 7 in a direction inclined by an angle ⁇ with respect to the direction Ox
  • the emission side face 8 of the mode is in a plane (x, z)
  • mode 6 is emitted by this side face in the direction Oy after a zigzag course inside the component.
  • FIG. 10 represents an example of a two-dimensional photonic structure of this type.
  • the metal blocks 1 are implanted on the multilayer heterostructure 7 according to a regular pattern two-dimensional, only a block 11 is missing as indicated in FIG. 10. Under the location of the missing block 11, the optical field is the most intense.
  • connection pads 12 located outside the guide zones 1, interconnection zones 13 connecting the guide zones to the connection pads, as indicated in FIG. 11.

Abstract

The invention concerns opto-electronic components with multilayer heterostructures, and in particular laser diodes emitting magnetic transverse polarization. One of the technical problems of this type of component is to ensure proper confinement of emission optical modes in the plane of the layers by modulating the effective index, so as to obtain good optical quality of the emission mode. The invention proposes to perform modulation of the effective index of the planar guide mode by coupling it with the surface plasmon obtained by deposition of a metal layer on the component heterostructure, Thus the planar structure of the component is maintained while the desired effective index modulation is obtained. This arrangement is applicable to different types of laser structures, such as, for example, Fabry-Pérot type quantum cascade laser, but also DFB or A-DFB, ARROW type lasers or still photonic crystals. The shape of the metal deposit is simply adapted to each type of structure.

Description

COMPOSANTS OPTOELECTRONIQUES A GUIDAGE DE L'ONDE OPTIQUE PAR RUBAN METALLIQUE OPTOELECTRONIC COMPONENTS WITH METAL TAPE GUIDANCE OF THE OPTICAL WAVE
Le domaine de l'invention est celui des composants optoélectroniques à hétérostructures multicouches, et notamment celui des diodes laser émettant en polarisation transverse magnétique, c'est-à-dire dont le champ électrique d'émission est polarisé perpendiculairement au plan des couches de l'hétérostructure.The field of the invention is that of optoelectronic components with multilayer heterostructures, and in particular that of laser diodes emitting in transverse magnetic polarization, that is to say of which the electric emission field is polarized perpendicular to the plane of the layers of l heterostructure.
De nombreuses applications de ce type de composants nécessitent que le mode optique qui y règne présente des qualités spatiale et spectrale bien déterminées. Le confinement du mode optique intra- composant doit, par conséquent, être parfaitement maîtrisé.Many applications of this type of component require that the optical mode which prevails there have well-defined spatial and spectral qualities. The confinement of the intra-component optical mode must therefore be perfectly mastered.
Les composants électroniques multicouches comprennent principalement une zone active émettant dans le moyen ou le lointain infrarouge en polarisation transverse magnétique, en exploitant, par exemple, les transitions intersousbande des puits quantiques (cas des lasers à cascade quantique dits QCL). Cette zone active est comprise entre deux couches dites couches de cladding. Les modes optiques de propagation à l'intérieur de ces couches encore appelés modes diélectriques sont alors caractérisés par un indice optique noté indice effectif. Le confinement dans un plan perpendiculaire au plan des couches du mode optique est assuré par les contrastes d'indice entre chaque couche. On parle alors de mode de guide planaire. Le confinement ou le guidage du mode dans le plan des couches est également nécessaire. Il permet notamment de minimiser le courant de seuil. Celui-ci ne peut être obtenu que par modification locale de l'indice effectif du mode planaire des couches.Multilayer electronic components mainly comprise an active area emitting in the middle or far infrared in magnetic transverse polarization, by exploiting, for example, the intersubband transitions of quantum wells (case of quantum cascade lasers called QCL). This active area is between two layers called cladding layers. The optical modes of propagation inside these layers also called dielectric modes are then characterized by an optical index noted effective index. The confinement in a plane perpendicular to the plane of the layers of the optical mode is ensured by the index contrasts between each layer. We then speak of planar guide mode. The confinement or the guidance of the mode in the plane of the layers is also necessary. In particular, it makes it possible to minimize the threshold current. This can only be obtained by local modification of the effective index of the planar mode of the layers.
Pour réaliser cette modulation d'indice effectif, on réalise actuellement des gravures par différentes techniques connues comme, par exemple, la gravure par faisceau ionique à assistance chimique (procédé CAIBE pour Chemical Assisted Ion Beam Etching) ou la gravure ionique réactive (procédé RIE pour Reactive Ion Etching).To achieve this effective index modulation, etching is currently carried out by various known techniques such as, for example, ion beam etching with chemical assistance (CAIBE process for Chemical Assisted Ion Beam Etching) or reactive ion etching (RIE process for Reactive Ion Etching).
Le processus de gravure peut conduire à un état de surface rugueux, générant des pertes optiques par diffusion. La gravure chimique permet de réduire la rugosité des surfaces gravées. Cependant, ce processus est difficile à maîtriser pour des structures de faibles dimensions, typiquement inférieures au micron, nécessaires aux composants travaillant dans l'infrarouge moyen. En effet, l'attaque chimique est sélective et anisotrope et rend délicate la reproductibilité du dispositif.The etching process can lead to a rough surface state, generating optical losses by diffusion. Chemical etching reduces the roughness of the etched surfaces. However, this This process is difficult to master for structures of small dimensions, typically less than a micron, necessary for the components working in the mid infrared. Indeed, the chemical attack is selective and anisotropic and makes the reproducibility of the device difficult.
D'autre part, dans le cas où les composants sont destinés à émettre des faisceaux optiques de forte puissance, la gravure des couches rend plus difficile le montage du composant avec sa face épitaxiée tournée vers l'embase en vue d'améliorer la dissipation thermique, montage dit Epilayer-down.On the other hand, in the case where the components are intended to emit high-power optical beams, the etching of the layers makes it more difficult to mount the component with its epitaxial face turned towards the base in order to improve the heat dissipation , montage says Epilayer-down.
L'objet de l'invention est de réduire ces différents problèmes liés à la gravure tout en conservant un procédé de réalisation simple.The object of the invention is to reduce these various problems associated with engraving while retaining a simple production method.
Une onde électromagnétique polarisée Transverse Magnétique peut se propager de manière guidée à l'interface d'un métal et d'un diélectrique sous forme de plasmon lorsque le métal et le semiconducteur ont des constantes diélectriques de signe opposée (P.Yeh, Optical Waves in Layered Media - Wiley, New-York, 1998). Dans le moyen infrarouge, le principe d'une diode laser basée sur cet effet a été démontré (C. Sirtori, C. Gmachl, F.Capasso, J.Faist, D.L. Sivco, A.L.Hutchinson and A.Y.Cho, Long- wavelength (λ = 8 - 11.5μm) semiconductor lasers with waveguides based on surface plasmons, Optics Letters / Vol. 23, N° 17/ 1366, sept. 1 , 1998). Cependant, cette diode s'avère peu performante car, dans ce domaine spectral, le métal introduit des pertes importantes.A polarized electromagnetic Transverse Magnetic wave can propagate in a guided way at the interface of a metal and a dielectric in the form of plasmon when the metal and the semiconductor have dielectric constants of opposite sign (P.Yeh, Optical Waves in Layered Media - Wiley, New-York, 1998). In the medium infrared, the principle of a laser diode based on this effect has been demonstrated (C. Sirtori, C. Gmachl, F. Capasso, J. Faist, DL Sivco, ALHutchinson and AYCho, Long-wavelength (λ = 8 - 11.5μm) semiconductor lasers with waveguides based on surface plasmons, Optics Letters / Vol. 23, N ° 17/1366, Sept. 1, 1998). However, this diode proves to be ineffective because, in this spectral range, the metal introduces significant losses.
Afin de minimiser les pertes tout en gardant l'avantage du guidage de l'onde, l'invention propose de coupler le plasmon de surface et le mode diélectrique d'un guide diélectrique planaire de façon à moduler l'indice effectif du mode diélectrique afin d'obtenir un mode optique résultant qui soit à la fois guidé et à faibles pertes. Cet effet est obtenu en déposant sur les couches de cladding du composant optoélectronique une zone supérieure en matériau semi-conducteur, puis un dépôt métallique sur ladite zone, l'épaisseur optique de la zone supérieure étant choisie de façon à obtenir un couplage optimal.In order to minimize losses while retaining the advantage of guiding the wave, the invention proposes to couple the surface plasmon and the dielectric mode of a planar dielectric guide so as to modulate the effective index of the dielectric mode in order to to obtain a resulting optical mode which is both guided and low loss. This effect is obtained by depositing on the cladding layers of the optoelectronic component an upper zone of semiconductor material, then a metallic deposit on said zone, the optical thickness of the upper zone being chosen so as to obtain optimal coupling.
On réalise ainsi une variation locale de l'indice effectif, suffisante pour assurer le guidage du mode dans le plan des couches sans altérer la structure planaire du composant et en supprimant les problèmes introduits par la gravure, le dépôt de métal ne présentant pas de difficultés techniques de réalisation.This produces a local variation of the effective index, sufficient to guide the mode in the plane of the layers without altering the planar structure of the component and eliminating the problems introduced. by etching, the deposition of metal presenting no technical difficulties of production.
Cette disposition s'applique notamment à différentes structures optiques de laser de type QCL, par exemple les lasers de type « Fabry- Pérot », mais également les lasers de type DFB (Distributed FeedBack) ou α-DFB (α-Distributed FeedBack), les lasers de type ARROW (AntiResonant Reflecting Optical Waveguide) ou encore les lasers basés sur des cavités de type à bande interdite photonique. La forme du dépôt métallique est simplement adaptée à chaque type de composant.This provision applies in particular to various QCL type laser optical structures, for example “Fabry-Pérot” type lasers, but also DFB (Distributed FeedBack) or α-DFB (α-Distributed FeedBack) type lasers, ARROW (AntiResonant Reflecting Optical Waveguide) lasers or lasers based on photonic band gap cavities. The shape of the metal deposit is simply adapted to each type of component.
Plus précisément, l'invention a pour objet un composant optoélectronique à heterostructure multicouches, comprenant successivement au moins un substrat, une zone active émettant en polarisation transverse magnétique et une zone supérieure en matériau semiconducteur, ledit composant comportant une face latérale d'émission sensiblement perpendiculaire au plan des couches, et émettant par ladite face latérale une onde optique à une longueur d'onde située dans l'infrarouge, caractérisé en ce que ladite zone supérieure porte au moins un dépôt métallique et que l'épaisseur de ladite zone supérieure est égale à une fraction de la longueur d'onde d'émission, permettant d'avoir une résonance entre d'une part, un mode de surface plasmonique lié au dépôt métallique et d'autre part un mode diélectrique lié à la zone active.More specifically, the subject of the invention is an optoelectronic component with a multilayer heterostructure, successively comprising at least one substrate, an active area emitting in magnetic transverse polarization and an upper area made of semiconductor material, said component comprising an emission side face that is substantially perpendicular in the plane of the layers, and emitting by said lateral face an optical wave at a wavelength situated in the infrared, characterized in that said upper zone carries at least one metallic deposit and that the thickness of said upper zone is equal at a fraction of the emission wavelength, making it possible to have a resonance between on the one hand, a plasmonic surface mode linked to the metallic deposit and on the other hand a dielectric mode linked to the active area.
Pour les composants de type laser « Fabry-Pérot », ledit dépôt métallique a la forme d'un ruban métallique. Pour les composants de type DFB (Distributed FeedBack), ledit dépôt métallique est composé de rubans identiques, parallèles entre eux et de direction parallèle à la face d'émission.For “Fabry-Pérot” laser type components, said metal deposit has the form of a metal strip. For components of the DFB (Distributed FeedBack) type, said metallic deposit is composed of identical ribbons, parallel to each other and of direction parallel to the emission face.
Pour les composants de type ARROW (AntiResonant Reflecting Optical Waveguide), ledit dépôt métallique est composé d'au moins deux ensembles identiques de rubans parallèles entre eux et de direction perpendiculaire à la face latérale d'émission.For components of the ARROW (AntiResonant Reflecting Optical Waveguide) type, said metallic deposit is composed of at least two identical sets of ribbons parallel to each other and of direction perpendicular to the lateral emission face.
Pour les composants de type α-DFB (α-Distributed FeedBack), ledit dépôt métallique est composé de deux ensembles identiques de rubans parallèles entre eux, la direction desdits rubans étant inclinée par rapport à la face latérale d'émission. Pour les lasers de type ARROW et α-DFB, chacun desdits ensembles de rubans constitue un miroir de Bragg.For components of the α-DFB (α-Distributed FeedBack) type, said metallic deposit is composed of two identical sets of ribbons parallel to each other, the direction of said ribbons being inclined relative to the lateral emission face. For ARROW and α-DFB type lasers, each of said sets of ribbons constitutes a Bragg mirror.
Enfin, dans le cas de dispositifs à bande photonique interdite, ledit dépôt métallique est composé d'un motif périodique bidimensionnel de zones métalliques. Pour assurer des guidages particuliers de l'onde, ledit motif comporte au moins une zone métallique manquante.Finally, in the case of devices with a prohibited photonic band, said metallic deposit is composed of a two-dimensional periodic pattern of metallic zones. To ensure particular guiding of the wave, said pattern comprises at least one missing metallic zone.
Avantageusement, le dépôt métallique comporte des plages dédiées à la connexion électrique. Dans un mode particulier de réalisation de ladite connexion, la zone supérieure et le dépôt métallique comporte une couche de matériau isolant, ladite couche comportant des zones d'épargne situées au-dessus du dépôt métallique, la connexion électrique du composant étant réalisée au niveau desdites zones d'épargne. Le matériau de la couche isolante est préférentiellement de l'alumine.Advantageously, the metal deposit has areas dedicated to the electrical connection. In a particular embodiment of said connection, the upper zone and the metal deposit comprises a layer of insulating material, said layer comprising sparing zones situated above the metal deposit, the electrical connection of the component being made at said level. savings zones. The material of the insulating layer is preferably alumina.
Avantageusement, les matériaux des couches sont à base d'arséniure de gallium et aluminium (AlAsGa) ou de phosphure d'indium et aluminium (AlInP) ou d'antimoniure d'indium (InSb) ou d'alliages silicium- germanium(SiGe). Le métal du dépôt est de l'or ou de l'aluminium.Advantageously, the materials of the layers are based on gallium arsenide and aluminum (AlAsGa) or indium and aluminum phosphide (AlInP) or indium antimonide (InSb) or silicon-germanium alloys (SiGe) . The metal of the deposit is gold or aluminum.
L'invention sera mieux comprise et d'autres avantages apparaîtront à la lecture de la description qui va suivre donnée à titre non limitatif et grâce aux figures annexées parmi lesquelles :The invention will be better understood and other advantages will appear on reading the description which follows given without limitation and thanks to the appended figures among which:
- les figures 1a et 1b représentent une vue en perspective et une vue de dessus du dispositif selon l'invention dans le cas d'un laser de type « Fabry-Pérot » ; - la figure 2 représente, dans le cas d'un laser QCL en- Figures 1a and 1b show a perspective view and a top view of the device according to the invention in the case of a laser type "Fabry-Perot"; - Figure 2 shows, in the case of a QCL laser in
AIGaAs/GaAs, le profil d'indice optique des différentes couches et la répartition d'énergie du mode optique diélectrique en fonction de ce profil lorsque le laser ne comporte pas de dépôt métallique ;AIGaAs / GaAs, the optical index profile of the different layers and the energy distribution of the dielectric optical mode as a function of this profile when the laser does not have a metallic deposit;
- la figure 3 représente, dans le cas d'un laser QCL en AIGaAs/GaAS selon l'invention, comportant une zone supérieure d'épaisseur inférieure à l'épaisseur dite de résonance, le profil d'indice optique des différentes couches et les répartitions d'énergie des modes optiques dits « liant » et « anti-liant » ;FIG. 3 represents, in the case of a QCL laser in AIGaAs / GaAS according to the invention, comprising an upper zone of thickness less than the thickness called resonance, the profile of optical index of the different layers and the energy distributions of the so-called “binder” and “anti-binder” optical modes;
- la figure 4 représente, dans le cas d'un laser QCL en AIGaAs/GaAS selon l'invention, comportant une zone supérieure d'épaisseur égale à l'épaisseur dite de résonance, le profil d'indice optique des différentes couches et les répartitions d'énergie des modes optiques couplés « liant » et « anti-liant » ;- Figure 4 shows, in the case of a QCL laser in AIGaAs / GaAS according to the invention, comprising an upper zone of thickness equal to the thickness called resonance, the optical index profile of the different layers and the energy distributions of the coupled optical modes "binder" and "anti-binder";
- la figure 5 représente, dans le cas d'un laser QCL en AIGaAs/GaAS selon l'invention, comportant une zone supérieure d'épaisseur supérieure à l'épaisseur dite de résonance, le profil d'indice optique des différentes couches et les répartitions d'énergie des modes optiques « liant » et « anti-liant » ;FIG. 5 represents, in the case of a QCL laser in AIGaAs / GaAS according to the invention, comprising an upper zone of thickness greater than the thickness called resonance, the optical index profile of the different layers and the energy distributions of the “binder” and “anti-binder” optical modes;
- la figure 6 représente les variations de l'indice effectif des modes optiques couplés « liant » et « anti-liant » en fonction de l'épaisseur de la zone supérieure ;- Figure 6 shows the variations of the effective index of the coupled optical modes "binder" and "anti-binder" depending on the thickness of the upper area;
- la figure 7 représente le schéma de principe d'un laser de type DFB selon l'invention ;- Figure 7 shows the block diagram of a DFB type laser according to the invention;
- la figure 8 représente le schéma de principe d'un laser de type ARROW selon l'invention ;- Figure 8 shows the block diagram of an ARROW type laser according to the invention;
- la figure 9 représente le schéma de principe d'un laser de type α-DFB selon l'invention ;- Figure 9 shows the block diagram of an α-DFB type laser according to the invention;
- la figure 10 représente le schéma de principe d'un laser à bande photonique interdite selon l'invention ; - la figure 11 représente une première disposition de la connectique électrique du composant ;- Figure 10 shows the block diagram of a laser photonic band prohibited according to the invention; - Figure 11 shows a first arrangement of the electrical connection of the component;
- la figure 12 représente une seconde disposition de la connectique électrique du composant.- Figure 12 shows a second arrangement of the electrical connection of the component.
Les figures 1a et 1b représentent le dispositif selon l'invention dans le cas d'un laser de type QCL (Quantum Cascade Laser) à cavité « Fabry-Pérot ». Classiquement, un laser de type QCL comporte une heterostructure multicouches 7 comprenant successivement un substrat 5, une première couche 42 dans un premier matériau semiconducteur, une seconde couche 32 dans un second matériau semiconducteur, une zone active 3, une troisième couche 31 identique à 32, une quatrième couche 41 identique à 42, une zone supérieure 2, la dite zone 2 étant recouverte d'un ruban métallique 1 , l'indice optique du premier matériau étant inférieur à celui du second matériau. L'ensemble des couches 3, 31et 32 forme le cœur du guide d'onde de la cavité laser qui émet un mode optique 6 par la face latérale 8. Les miroirs plans de la cavité « Fabry-Pérot » sont constitués d'une part par la face latérale d'émission 8 et d'autre part par la face 80 opposée et parallèle à ladite face latérale 8. Par rapport à un repère (O, x, y, z) orthogonal, le plan des couches est dans un plan (x, y), la face latérale 8 et la face opposée 80 dans un plan (x, z) et la direction du ruban métallique et la direction d'émission du mode optique sont parallèles à l'axe Oy. A l'intérieur du composant, le mode optique 6 est confiné dans la direction Oz par le contraste d'indice existant entre les couches 41 , 42 et les couches 31 , 32. Il est confiné dans la direction Ox par la variation d'indice effectif introduit par le ruban métallique 1.Figures 1a and 1b show the device according to the invention in the case of a QCL (Quantum Cascade Laser) type laser with "Fabry-Pérot" cavity. Conventionally, a QCL type laser comprises a multilayer heterostructure 7 successively comprising a substrate 5, a first layer 42 in a first semiconductor material, a second layer 32 in a second semiconductor material, an active area 3, a third layer 31 identical to 32 , a fourth layer 41 identical to 42, an upper zone 2, said zone 2 being covered with a metallic strip 1, the optical index of the first material being lower than that of the second material. The set of layers 3, 31 and 32 forms the heart of the waveguide of the laser cavity which emits an optical mode 6 from the face side 8. The plane mirrors of the "Fabry-Pérot" cavity are formed on the one hand by the emission side face 8 and on the other hand by the face 80 opposite and parallel to said side face 8. With respect to a orthogonal reference mark (O, x, y, z), the plane of the layers is in a plane (x, y), the lateral face 8 and the opposite face 80 in a plane (x, z) and the direction of the metallic strip and the direction of emission of the optical mode are parallel to the axis Oy. Inside the component, the optical mode 6 is confined in the direction Oz by the index contrast existing between the layers 41, 42 and the layers 31 , 32. It is confined in the direction Ox by the variation in effective index introduced by the metallic strip 1.
Dans le cas d'un laser QCL en AIGaAs/GaAs, le substrat est en GaAs, la zone active est à base d'antimoniure d'indium, les couches 31 et 32 sont en GaAs, les couches 41 et 42 sont en AIGaAs, la zone supérieure 2 est également en GaAs et le dépôt métallique est, par exemple, en or. L'indice optique suivant l'axe transversal Oz aux couches est fonction du matériau et de l'épaisseur en microns desdites couches. Il est représenté sur la courbe du bas de la figure 2. Lorsque le laser ne comporte pas de dépôt métallique, un mode optique diélectrique peut se propager à l'intérieur du composant, la répartition d'énergie de ce mode optique diélectrique en fonction du profil d'indice est représentée sur la courbe du haut de cette même figure. La répartition d'énergie a une allure « gaussienne » suivant l'axe Oz. En l'absence de dépôt métallique, elle n'est cependant pas confinée suivant l'axe Ox.In the case of an AIGaAs / GaAs QCL laser, the substrate is made of GaAs, the active area is based on indium antimonide, layers 31 and 32 are made of GaAs, layers 41 and 42 are made of AIGaAs, the upper zone 2 is also made of GaAs and the metallic deposit is, for example, of gold. The optical index along the transverse axis Oz to the layers depends on the material and the thickness in microns of said layers. It is represented on the bottom curve of FIG. 2. When the laser does not have a metallic deposit, a dielectric optical mode can propagate inside the component, the energy distribution of this dielectric optical mode depending on the index profile is shown on the top curve of this same figure. The energy distribution has a “Gaussian” appearance along the Oz axis. In the absence of metallic deposit, it is however not confined along the axis Ox.
Lorsque l'on ajoute le dépôt métallique sur la zone supérieure, deux modes optiques peuvent coexister dans la zone du composant située sous le dépôt :When adding the metallic deposit on the upper zone, two optical modes can coexist in the zone of the component located under the deposit:
• Le mode optique diélectrique précédent confiné selon l'axe Oz caractérisé par un premier indice effectif dépendant de l'épaisseur de la zone supérieure. • Un mode plasmonique ou plasmon, de polarisation transverse magnétique se propageant à l'interface métal-zone intermédiaire caractérisé par un second indice effectif dépendant également de l'épaisseur de la zone supérieure.• The previous dielectric optical mode confined along the Oz axis, characterized by a first effective index depending on the thickness of the upper zone. • A plasmonic or plasmon mode, of transverse magnetic polarization propagating at the metal-intermediate zone interface characterized by a second effective index also depending on the thickness of the upper zone.
L'onde plasmonique prend naissance à l'interface de deux matériaux dont les constantes diélectriques sont de signe opposé. En effet, dans le moyen infrarouge, la fréquence optique du mode plasmonique étant inférieure à la fréquence de plasma, la constante diélectrique du métal est négative alors que celle de la zone supérieure est positive. L'amplitude de ce mode de surface décroît exponentiellement dans les deux milieux selon l'axe Oz, normal à l'interface entre les deux milieux. Les pertes d'un mode plasmonique sont importantes. Le coefficient de perte est souvent supérieur à 50 cm"1.The plasmonic wave arises at the interface of two materials whose dielectric constants are of opposite sign. Indeed, in the medium infrared, the optical frequency of the plasmonic mode being lower than the plasma frequency, the dielectric constant of the metal is negative while that of the upper zone is positive. The amplitude of this surface mode decreases exponentially in the two media along the Oz axis, normal at the interface between the two media. The losses of a plasmonic mode are significant. The loss coefficient is often greater than 50 cm "1 .
Dans le cas où le mode diélectrique est également de polarisation transverse magnétique, ces deux modes peuvent interagir, l'interaction dépendant de l'épaisseur géométrique de la zone supérieure. Lorsque les deux indices effectifs se rapprochent, les deux modes se couplent pour former deux modes hybrides dits « liant » et « anti-liant », ces modes hybrides pouvant être décrits comme des combinaisons linéaires des modes en interaction. L'hybridation des modes permet donc d'obtenir à la fois un mode liant confiné selon l'axe Ox dans la zone du composant située sous le dépôt et présentant également de faibles pertes dans la mesure où il n'est pas purement plasmonique.In the case where the dielectric mode is also of transverse magnetic polarization, these two modes can interact, the interaction depending on the geometric thickness of the upper zone. When the two effective indices come together, the two modes couple to form two hybrid modes called "binder" and "anti-binder", these hybrid modes can be described as linear combinations of the modes in interaction. The hybridization of the modes therefore makes it possible to obtain both a binder mode confined along the axis Ox in the zone of the component located under the deposit and also having low losses insofar as it is not purely plasmonic.
Pour la configuration « Fabry-Pérot » du laser QCL décrit en figures 1 et 2, les trois courbes de la figure 3 représentent en l'absence de zone supérieure:For the “Fabry-Pérot” configuration of the QCL laser described in Figures 1 and 2, the three curves in Figure 3 represent in the absence of an upper zone:
• La courbe du bas : le profil d'indice des différentes couches selon un axe Oz. La double barre indique la limite entre la zone supérieure et le métal. • La courbe du milieu : la répartition d'énergie (E.M.N.L.) du mode• The bottom curve: the index profile of the different layers along an Oz axis. The double bar indicates the limit between the upper zone and the metal. • The middle curve: the energy distribution (E.M.N.L.) of the mode
« anti-liant » en fonction de ce même profil d'indice."Anti-binder" according to this same index profile.
• La courbe du haut : la répartition d'énergie (E.M.L) du mode « liant » en fonction de ce même profil d'indice.• The upper curve: the energy distribution (E.M.L) of the “binder” mode as a function of this same index profile.
Pour la configuration du laser QCL décrit en figures 1 et 2, les trois courbes de la figure 4 représentent pour une zone supérieure ayant une épaisseur optimale :For the configuration of the QCL laser described in FIGS. 1 and 2, the three curves of FIG. 4 represent for an upper zone having an optimal thickness:
• La courbe du bas : le profil d'indice des différentes couches selon un axe Oz. L'épaisseur optimale de la couche supérieure vaut environ 1 micron. • La courbe du milieu : la répartition d'énergie (E.M.N.L) du mode « anti-liant » en fonction de ce même profil d'indice.• The bottom curve: the index profile of the different layers along an Oz axis. The optimum thickness of the upper layer is approximately 1 micron. • The middle curve: the energy distribution (EMNL) of the “anti-binder” mode according to this same index profile.
• La courbe du haut : la répartition d'énergie (E.M.L) du mode « liant » en fonction de ce même profil d'indice. Pour la configuration du laser QCL décrit en figures 1 et 2, les trois courbes de la figure 5 représentent pour une zone supérieure ayant une épaisseur de 2 microns supérieure à l'épaisseur optimale :• The upper curve: the energy distribution (E.M.L) of the “binder” mode as a function of this same index profile. For the configuration of the QCL laser described in FIGS. 1 and 2, the three curves of FIG. 5 represent for an upper zone having a thickness of 2 microns greater than the optimal thickness:
• La courbe du bas : le profil d'indice des différentes couches selon un axe Oz. « La courbe du milieu : la répartition d'énergie (E.M.N.L.) du mode• The bottom curve: the index profile of the different layers along an Oz axis. "The middle curve: the energy distribution (E.M.N.L.) of the mode
« anti-liant » en fonction de ce même profil d'indice."Anti-binder" according to this same index profile.
• La courbe du haut : la répartition d'énergie (E.M.L) du mode « liant » en fonction de ce même profil d'indice.• The upper curve: the energy distribution (E.M.L) of the “binder” mode as a function of this same index profile.
La courbe de la figure 6 représente la variation de l'indice effectifThe curve of figure 6 represents the variation of the effective index
N.M.L pour le mode « liant » (courbe en trait plein) et la variation de l'indice effectif N.M.N.L pour le mode « anti-liant » (courbe en trait pointillé) en fonction de l'épaisseur de la zone supérieure. Le couplage optimal entre les deux modes est réalisé pour l'épaisseur correspondant à la quasi-égalité des indices effectifs.N.M.L for the "binder" mode (curve in solid line) and the variation of the effective N.M.N.L index for the "anti-binder" mode (curve in dotted line) depending on the thickness of the upper zone. The optimal coupling between the two modes is carried out for the thickness corresponding to the quasi-equality of the effective indices.
L'invention s'applique à différents types de composants optoélectroniques décrits ci-dessous, à titre non limitatif :The invention applies to different types of optoelectronic components described below, without implied limitation:
• Lasers à contre-réaction répartie de type DFB (Distributed FeedBack).• Distributed feedback type DFB (Distributed FeedBack) lasers.
Les lasers à semiconducteurs présentent un fonctionnement multimode longitudinal. Ce caractère multimodal est très gênant pour de nombreuses applications (focalisation du faisceau, propagation dans des fibres optiques,...). Pour y remédier, on réalise des lasers à contre-réaction répartie de type DFB (Distributed FeedBack). Le principe est d'introduire une modulation périodique de l'indice effectif dans la direction de propagation du faisceau et, de ce fait, d'effectuer un filtrage fréquentiel très sélectif, analogue à celui du miroir de Bragg. On peut ainsi rendre une diode laser monomode. La modulation d'indice effectif peut être obtenue en déposant des rubans métalliques selon l'invention sur l'hétérostructure du composant. La figure 7 donne le schéma de principe d'un dispositif de ce type. Sur une heterostructure multicouches 7 définie dans un repère (O, x, y, z) orthogonal, le plan des couches est dans un plan (x, y), les rubans métalliques 1 parallèles entre eux sont implantés sur l'hétérostructure multicouches 7 suivant la direction Ox, la face latérale d'émission 8 du mode est dans un plan (x, z), le mode 6 est émis par cette face latérale suivant une direction Oy perpendiculaire à la direction des rubans métalliques 1.Semiconductor lasers have longitudinal multimode operation. This multimodal character is very inconvenient for many applications (focusing of the beam, propagation in optical fibers, etc.). To remedy this, distributed feedback lasers of the DFB (Distributed FeedBack) type are produced. The principle is to introduce a periodic modulation of the effective index in the direction of propagation of the beam and, therefore, to perform a very selective frequency filtering, similar to that of the Bragg mirror. It is thus possible to render a laser diode single mode. The effective index modulation can be obtained by depositing metal strips according to the invention on the heterostructure of the component. Figure 7 gives the block diagram of a device of this type. On a multilayer heterostructure 7 defined in an orthogonal coordinate system (O, x, y, z), the plane of the layers is in a plane (x, y), the metallic ribbons 1 parallel to one another are implanted on the following multilayer heterostructure 7 the direction Ox, the emission side face 8 of the mode is in a plane (x, z), mode 6 is emitted by this side face in a direction Oy perpendicular to the direction of the metal strips 1.
• Structures anti-guidantes de type ARROW (AntiResonant Reflecting Optical Waveguide)• ARROW anti-guiding structures (AntiResonant Reflecting Optical Waveguide)
Ce type de guide permet un bon confinement optique horizontal dans les guides d'onde planaire (J.Gehler, A.Brâuer and W.Karthe : Antiresonant reflecting optical waveguides in strip configuration - Appl. Phys. Letters 64 (3), 17 january 1994). Le principe est de réaliser deux miroirs de Bragg parallèles entre eux sur l'hétérostructure, le mode d'émission étant confiné dans l'espace situé entre ces deux miroirs. Un seul mode optique transversal est présent dans cette structure quelle que soit la taille de ce mode, ce qui représente l'avantage principal de ce guidage. De plus, il est aussi possible d'immuniser le guide ARROW des phénomènes de saturation spatiale du gain. Chaque miroir peut être obtenu en déposant au moins deux rubans selon l'invention sur l'hétérostructure comme il est présenté en figure 8. Sur une heterostructure multicouches 7 définie dans un repère (O, x, y, z) orthogonal, le plan des couches est dans un plan (x, y), les rubans métalliques 1 constituant les miroirs de Bragg sont implantés sur l'hétérostructure multicouches 7 suivant la direction Oy, la face latérale d'émission 8 du mode est dans un plan (x, z), le mode 6 est émis par cette face latérale suivant une direction Oy parallèle à la direction des rubans métalliques 1.This type of guide allows a good horizontal optical confinement in the planar wave guides (J. Gehler, A. Brâuer and W. Karthe: Antiresonant reflecting optical waveguides in strip configuration - Appl. Phys. Letters 64 (3), 17 january 1994). The principle is to make two Bragg mirrors parallel to each other on the heterostructure, the emission mode being confined in the space between these two mirrors. Only one transverse optical mode is present in this structure whatever the size of this mode, which represents the main advantage of this guidance. In addition, it is also possible to immunize the ARROW guide from the phenomena of spatial gain saturation. Each mirror can be obtained by depositing at least two ribbons according to the invention on the heterostructure as it is presented in FIG. 8. On a multilayer heterostructure 7 defined in an orthogonal coordinate system (O, x, y, z), the plane of the layers is in a plane (x, y), the metallic ribbons 1 constituting the Bragg mirrors are implanted on the multilayer heterostructure 7 in the direction Oy, the emission side face 8 of the mode is in a plane (x, z ), mode 6 is emitted by this lateral face in a direction Oy parallel to the direction of the metallic ribbons 1.
• Lasers de type α-DFB (α-Distributed FeedBack)• α-DFB (α-Distributed FeedBack) type lasers
Dans les applications de forte puissance nécessitant une taille plus grande du mode optique, la technologie DFB ne convient plus. On réalise alors un laser de type α-DFB. Le principe est de confiner le mode optique dans une structure guidante inclinée par rapport à la face latérale de sortie (R.E.Bartolo, W.W.BewIey, INurgaftman, C.L.Felix , J.R.Meyer and M.J.Yang, Appl. Phys. Lett. 76(2000), 3164). Les modes réalisent alors un trajet en zig-zag par réflexions successives sur les miroirs de Bragg de la structure guidante et seuls ceux qui sont normaux à la face de sortie peuvent osciller. On améliore ainsi nettement la cohérence spatiale et la cohérence temporelle du mode. La structure guidante inclinée peur être obtenue comme pour un guide de type ARROW au moyen de rubans métalliques déposés sur l'hétérostructure du composant comme il est indiqué sur la figure 9. Sur une heterostructure multicouches 7 définie dans un repère (O, x, y, z) orthogonal, le plan des couches est dans un plan (x, y), les rubans métalliques 1 constituant les miroirs de Bragg sont implantés sur l'hétérostructure multicouches 7 suivant une direction inclinée d'un angle α par rapport à la direction Ox , la face latérale d'émission 8 du mode est dans un plan (x, z), le mode 6 est émis par cette face latérale suivant la direction Oy après un parcours en zig-zag à l'intérieur du composant.In high power applications requiring a larger optical mode size, DFB technology is no longer suitable. An α-DFB type laser is then produced. The principle is to confine the optical mode in a guiding structure inclined relative to the lateral exit face (REBartolo, WWBewIey, INurgaftman, CLFelix, JRMeyer and MJYang, Appl. Phys. Lett. 76 (2000), 3164). The modes then carry out a zigzag path by successive reflections on the Bragg mirrors of the guiding structure and only those which are normal to the exit face can oscillate. This clearly improves the spatial coherence and the temporal coherence of the mode. The inclined guiding structure can be obtained as for an ARROW type guide by means of metallic ribbons deposited on the heterostructure of the component as indicated in FIG. 9. On a multilayer heterostructure 7 defined in a frame (O, x, y , z) orthogonal, the plane of the layers is in a plane (x, y), the metallic ribbons 1 constituting the Bragg mirrors are implanted on the multilayer heterostructure 7 in a direction inclined by an angle α with respect to the direction Ox, the emission side face 8 of the mode is in a plane (x, z), mode 6 is emitted by this side face in the direction Oy after a zigzag course inside the component.
• Structures photoniques bidimensionnelles. En procédant au dépôt de motifs bidimensionnels métalliques sur une heterostructure multicouches, on réalise des structures de type cristaux photoniques. En particulier, on peut réaliser des lasers à bande interdite avec défaut (Two-dimensional Photonic Band-gap defect Mode Laser- O.Painter, R.K.Lee, A.Scherer, A.Yariv, J.D. O'Brien, P.D.Dapkus, I.Kim - Science, 284, 1819). La figure 10 représente un exemple d'une structure photonique bidimensionnelle de ce type. Sur une heterostructure multicouches 7 définie dans un repère (O, x, y, z) orthogonal, le plan des couches est dans un plan (x, y), les pavés métalliques 1 sont implantés sur l'hétérostructure multicouches 7 suivant un motif régulier bidimensionnel, seul manque un pavé 11 comme indiqué sur la figure 10. Sous l'emplacement du pavé manquant 11 , le champ optique est le plus intense.• Two-dimensional photonic structures. By depositing two-dimensional metallic patterns on a multilayer heterostructure, photonic crystal type structures are produced. In particular, it is possible to produce prohibited band lasers with defect (Two-dimensional Photonic Band-gap defect Mode Laser- O. Painter, RKLee, A.Scherer, A.Yariv, JD O'Brien, PDDapkus, I. Kim - Science, 284, 1819). FIG. 10 represents an example of a two-dimensional photonic structure of this type. On a multilayer heterostructure 7 defined in an orthogonal coordinate system (O, x, y, z), the plane of the layers is in a plane (x, y), the metal blocks 1 are implanted on the multilayer heterostructure 7 according to a regular pattern two-dimensional, only a block 11 is missing as indicated in FIG. 10. Under the location of the missing block 11, the optical field is the most intense.
Le courant électrique nécessaire au fonctionnement du composant est amené par le dépôt métallique. Afin de ne pas perturber la géométrie des ondes émises, la connexion électrique ne peut être établie directement sur les zones du dépôt servant au guidage de l'onde. Aussi, il est avantageux que le dépôt métallique comprennent des plages de connexion 12 spécifiques situées hors des zones de guidage 1 , des zones d'interconnexion 13 reliant les zones de guidage aux plages de connexion, comme il est indiqué sur la figure 11.The electric current necessary for the operation of the component is brought by the metallic deposit. In order not to disturb the geometry of the waves emitted, the electrical connection cannot be established directly on the areas of the deposit used for guiding the wave. Also, it is advantageous for the metal deposit to include specific connection pads 12 located outside the guide zones 1, interconnection zones 13 connecting the guide zones to the connection pads, as indicated in FIG. 11.
Il est également possible, afin de conserver la géométrie des dépôts métalliques, de déposer sur la surface du composant une couche de matériau électriquement isolant 14, ladite couche comportant des zones d'épargne situées au-dessus du dépôt métallique, la connexion électrique 15 du composant étant réalisée au niveau desdites zones d'épargne comme il est indiqué sur la figure 12. It is also possible, in order to preserve the geometry of the metallic deposits, to deposit on the surface of the component a layer of electrically insulating material 14, said layer comprising sparing zones located above the metallic deposit, the electrical connection 15 of the component being produced at said savings zones as indicated in FIG. 12.

Claims

REVENDICATIONS
1. Composant optoélectronique à heterostructure multicouches (7) comprenant successivement au moins un substrat (5), une zone active1. Optoelectronic component with multilayer heterostructure (7) successively comprising at least one substrate (5), an active area
(3) émettant en polarisation transverse magnétique et une zone supérieure (2) en matériau semiconducteur, ledit composant comportant une face latérale (8) d'émission sensiblement perpendiculaire au plan des couches, et émettant par ladite face latérale (8) une onde optique (6) à une longueur d'onde située dans l'infrarouge, caractérisé en ce que ladite zone supérieure (2) porte au moins un dépôt métallique (1) et que l'épaisseur de ladite zone supérieure (2) est égale à une fraction de la longueur d'onde d'émission, permettant d'avoir une résonance entre un mode de surface plasmonique lié au dépôt métallique (1) et un mode diélectrique lié à la zone active (3).(3) emitting in transverse magnetic polarization and an upper zone (2) of semiconductor material, said component comprising a lateral face (8) of emission substantially perpendicular to the plane of the layers, and emitting by said lateral face (8) an optical wave (6) at a wavelength situated in the infrared, characterized in that said upper zone (2) carries at least one metallic deposit (1) and that the thickness of said upper zone (2) is equal to one fraction of the emission wavelength, making it possible to have a resonance between a plasmonic surface mode linked to the metal deposit (1) and a dielectric mode linked to the active zone (3).
2. Composant optoélectronique à heterostructure multicouches selon la revendication 1 , caractérisé en ce que ledit dépôt métallique a la forme d'un ruban métallique droit.2. Optoelectronic component with multilayer heterostructure according to claim 1, characterized in that said metallic deposit has the form of a straight metallic strip.
3. Composant optoélectronique à heterostructure multicouches selon la revendication 1 , caractérisé en ce que ledit dépôt métallique est composé de rubans (1) identiques, parallèles entre eux et de direction parallèle à la face latérale d'émission (8).3. Optoelectronic component with multilayer heterostructure according to claim 1, characterized in that said metallic deposit is composed of identical ribbons (1), mutually parallel and of direction parallel to the lateral emission face (8).
4. Composant optoélectronique à heterostructure multicouches selon la revendication 1 , caractérisé en ce que ledit dépôt métallique est composé d'au moins deux ensembles identiques de rubans (1) parallèles entre eux et de direction perpendiculaire à la face latérale d'émission (8).4. optoelectronic component with multilayer heterostructure according to claim 1, characterized in that said metallic deposit is composed of at least two identical sets of ribbons (1) parallel to each other and of direction perpendicular to the lateral emission face (8) .
5. Composant optoélectronique à heterostructure multicouches selon la revendication 1 , caractérisé en ce que ledit dépôt métallique est composé d'au moins deux ensembles identiques de rubans (1) parallèles entre eux, la direction desdits rubans étant inclinée par rapport à la face latérale d'émission. 5. optoelectronic component with multilayer heterostructure according to claim 1, characterized in that said metallic deposit is composed of at least two identical sets of ribbons (1) parallel to each other, the direction of said ribbons being inclined relative to the lateral face d 'program.
6. Composant optoélectronique à heterostructure multicouches selon les revendications 4 et 5, caractérisé en ce que lesdits deux ensembles identiques de rubans (1) forment des miroirs de Bragg.6. optoelectronic component with multilayer heterostructure according to claims 4 and 5, characterized in that said two identical sets of ribbons (1) form Bragg mirrors.
7. Composant optoélectronique à heterostructure multicouches de type cristal photonique selon la revendication 1 , caractérisé en ce que ledit dépôt métallique est composé d'un motif périodique bidimensionnel de zones métalliques (1).7. Optoelectronic component with multilayer heterostructure of photonic crystal type according to claim 1, characterized in that said metallic deposit is composed of a two-dimensional periodic pattern of metallic zones (1).
8. Composant optoélectronique à heterostructure multicouches de type cristal photonique selon la revendication 7, caractérisé en ce que ledit motif comporte au moins une zone métallique manquante (11).8. Optoelectronic component with multilayer heterostructure of photonic crystal type according to claim 7, characterized in that said pattern comprises at least one missing metallic zone (11).
9. Composant optoélectronique à heterostructure multicouches selon l'une des revendications précédentes, caractérisé en ce que le dépôt métallique comporte des plages (12) dédiées à la connexion électrique.9. Optoelectronic component with multilayer heterostructure according to one of the preceding claims, characterized in that the metal deposit comprises areas (12) dedicated to the electrical connection.
10. Composant optoélectronique à heterostructure multicouches selon la revendication 9, caractérisé en ce que la zone supérieure (2) et le dépôt métallique (1) comporte une couche de matériau isolant (14), ladite couche comportant des zones d'épargne situées au-dessus du dépôt métallique, la connexion électrique (15) du composant étant réalisée au niveau desdites zones d'épargne.10. optoelectronic component with multilayer heterostructure according to claim 9, characterized in that the upper zone (2) and the metal deposit (1) comprises a layer of insulating material (14), said layer comprising savings zones located at- above the metal deposit, the electrical connection (15) of the component being made at said savings zones.
11. Composant optoélectronique à heterostructure multicouches selon la revendication 10, caractérisé en ce que le matériau de la couche isolante est de l'alumine.11. optoelectronic component with multilayer heterostructure according to claim 10, characterized in that the material of the insulating layer is alumina.
12. Composant électronique à heterostructure multicouches selon l'une des revendications précédentes, caractérisé en ce que les matériaux des différentes couches (2, 3, 31 , 32, 41 et 42) sont à base d'arséniure de gallium et aluminium (AlAsGa) ou de phosphure d'indium et aluminium (AlInP) ou d'antimoniure d'indium (InSb) ou d'alliages silicium-germanium (SiGe). 12. Electronic component with multilayer heterostructure according to one of the preceding claims, characterized in that the materials of the different layers (2, 3, 31, 32, 41 and 42) are based on gallium arsenide and aluminum (AlAsGa) or indium aluminum phosphide (AlInP) or indium antimonide (InSb) or silicon-germanium alloys (SiGe).
13. Composant électronique à heterostructure multicouches selon l'une des revendications précédentes, caractérisé en ce que le matériau d'au moins une couche est à base d'arséniure de gallium (AsGa).13. Electronic component with multilayer heterostructure according to one of the preceding claims, characterized in that the material of at least one layer is based on gallium arsenide (AsGa).
14. Composant électronique à heterostructure multicouches selon l'une des revendications précédentes, caractérisé en ce que le métal du dépôt (1) est de l'or ou de l'aluminium. 14. Electronic component with multilayer heterostructure according to one of the preceding claims, characterized in that the metal of the deposit (1) is gold or aluminum.
EP03778379A 2002-10-01 2003-09-30 Opto-electronic components with metal strip optical guidance Withdrawn EP1576705A2 (en)

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FR0212133 2002-10-01
FR0212133A FR2845208A1 (en) 2002-10-01 2002-10-01 OPTOELECTRONIC COMPONENTS WITH METAL TAPE GUIDANCE OF THE OPTICAL WAVE
PCT/FR2003/002867 WO2004032297A2 (en) 2002-10-01 2003-09-30 Opto-electronic components with metal strip optical guidance

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