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.

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