Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
  • G02B6/3512—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror
  • G02B6/3514—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror the reflective optical element moving along a line so as to translate into and out of the beam path, i.e. across the beam path
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/3564—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details
  • G02B6/3584—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
  • G02B6/3512—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror
  • G02B6/3518—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
  • G02B6/3544—2D constellations, i.e. with switching elements and switched beams located in a plane
  • G02B6/3546—NxM switch, i.e. a regular array of switches elements of matrix type constellation
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
  • G02B6/3544—2D constellations, i.e. with switching elements and switched beams located in a plane
  • G02B6/3548—1xN switch, i.e. one input and a selectable single output of N possible outputs
  • G02B6/355—1x2 switch, i.e. one input and a selectable single output of two possible outputs
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/3564—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details
  • G02B6/3568—Mechanical details of the actuation mechanism associated with the moving element or mounting mechanism details characterised by the actuating force
  • G02B6/357—Electrostatic force
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/35—Optical coupling means having switching means
  • G02B6/3596—With planar waveguide arrangement, i.e. in a substrate, regardless if actuating mechanism is outside the substrate

Definitions

• the present invention relates to an optical micro-mirror switch as well as its production method.
• It relates more precisely to an optical switch able to transfer a light wave conveyed by an optical input channel to a first or a second optical output channel.
• the invention finds applications in all fields using optical switches and in particular in the field of telecommunications by optical means.
• one of the families of switches consists in bringing the light beam by a mechanical system capable of conveying said light light beam (for example a mobile beam provided with an optical guide) at the entrance to one of the optical exit channels; this principle is for example described in US Pat. No. 5,078,514, the other family of switches uses a micro-mirror capable of moving between the optical input channel and the two optical output channels of so as to allow either the passage by transmission of the light beam from the input channel to one of the output channels or the reflection passage of the beam from the input channel to the other output channel.
• the invention relates to this latter family of switches.
• FIGS. 1a and 1b illustrate precisely the use of micro-mirrors in free space, able to move in two positions between an input fiber 1 and two output fibers 3 and 5.
• the optical axis of the fiber 3 is in optical alignment with that of the fiber 1 while that of the fiber 5 is perpendicular to that of the fiber 1.
• the micro-mirror when the micro-mirror is in a position in which it does not come between the fibers 1 and 3 on the optical axis of said fibers, the light beam leaving the fiber 1 is transmitted to the fiber 3; and when the micro-mirror is in a position in which it is interposed between the fibers 1 and 3 on the optical axis of the said fibers, the light beam leaving the fiber 1 is reflected by the mirror and transmitted to the fiber 5.
• the micromirror 7 used moves in a translational movement.
• the arrows 8a and 8b represent the translational movement of the mirror respectively on Figures 1a and 1b. This translational movement is carried out in a plane containing that of the micro-mirror.
• the optical axis of the fiber 3 is also in optical alignment with that of the fiber 1 while that of the fiber 5 is arranged at 45 ° from that of the fiber 1.
• the micromirror 11 used moves in a rotational movement around a hinge 9 which is perpendicular to the optical axis of the fiber 1- and which is contained in the plane of the mirror.
• the arrow 10 in FIG. 2b represents the rotational movement of the mirror which is able to move 90 °.
• the micro-mirror when the micro-mirror is below the optical axis of the fiber 1, the light beam conveyed by the fiber 1 is transmitted to the fiber 3 while when the micromirror is interposed so that the beam light coming from fiber 1 is incident at 45 ° on it, it is reflected back to fiber 5.
• the rigid micro-mirrors used in these structures are difficult to transpose into integrated optics taking into account the fact that the technology for producing the optical guides and that of the mirrors are different and therefore hardly compatible.
• the object of the present invention is to propose an optical switch using a rigid micro-mirror which can be used both in integrated optics and in free space optics and therefore does not present the reliability problems of switches in integrated optics of the prior art.
• Another object of the invention is to provide an optical switch using a micro-mirror capable of being controlled by voltages which may be lower than those of the micro-mirrors described above.
• Another object of the invention is also to propose an optical switch using a micromirror minimizing optical losses and being able to have the fastest possible access time and to be insensitive to polarization and to wavelength.
• Another object of the invention is also to propose a method for producing a switch in integrated optics which is simple, easy to implement and therefore having good manufacturing efficiency.
• the invention relates to an optical switch comprising at least one optical input channel and at least first and second optical output channels as well as a micro-mirror capable of moving between an output of the channel optical input and inputs of the first and second optical output channels, the optical input channel and the first optical output channel having an identical optical axis, called the first optical axis and the second optical output channel having an optical axis said second optical axis, the micro-mirror comprising a reflecting part and an actuating part having an axis of rotation and capable of driving in rotation along a so-called tilting plane the reflecting part, the tilting plane being perpendicular to a plane containing the axis of rotation and said reflecting part comprising at least one reflecting face in a plane parallel to the tilting plane capable of reflecting hir a light wave coming from the entry channel towards the second exit channel, the first and second optical axes respectively forming an angle ⁇ with respect to an axis of symmetry, the optical switch further comprising a control device for making tilt the reflecting part, this
• the optical switch comprises a first optical input channel associated with a first and a second optical output channels and a second optical input channel associated with a third and a fourth optical channels output, the micromirror being able to be interposed either between an output of the first optical input channel and inputs of the first and second optical output channels, or between an output of the second optical input channel and inputs third and fourth optical output channels.
• the optical input and output channels are chosen independently of one another from optical fibers or optical guides.
• the optical input and output channels are produced respectively by optical guides in a substrate, said substrate further comprising a cavity capable of allowing rotation along the so-called tilting plane of the reflecting part.
• the tilting plane of the reflecting part and the axis of rotation of the actuating part are perpendicular.
• the reflective part which comprises the reflective face and the actuating part which generally comprises a set of electrodes and which forms a zone of attraction are decoupled, which allows the micro-mirror of the invention to use a leverage effect which multiplies the displacement of the reflecting part.
• the movement of the micro-mirror being generally obtained by the use of electrostatic forces generated by two sets of electrodes on which a potential difference is applied, the area of attraction being independent of the reflecting part, the surface of the electrodes of the actuating part can be large, which makes it possible to reduce the forces necessary to tilt the reflecting part and therefore the control voltages.
• the inter-electrode space which can be reduced, which also makes it possible to reduce the forces necessary to tilt the reflecting part.
• Each electrode set includes at least one electrode.
• the micro-mirror of the invention advantageously comprises' at least one stop capable of limiting the movement of the reflecting part.
• This stop is achieved for example, in the case of a switch with a single input channel and two output channels, by a bulge at one end of the reflecting part, the width of said bulge in a plane perpendicular to the plane tilting is greater than the width of the cavity in the same plane.
• the switch of the invention makes it possible to have a rapid response time for example of the order of ms or a few tens of ⁇ s, in particular thanks to the dimensions of the micro-mirror which can be reduced. It makes it possible to be insensitive to polarization and to the wavelength due to the use for switching over a transmission or reflection effect by a mirror.
• the micro-mirror is not limited to total reflection. Indeed, the reflecting part of the micro-mirror can make it possible to selectively reflect a single polarization or certain wavelengths and transmit respectively the other polarization or other wavelengths, the micro-mirror then plays the role of filter .
• the invention also relates to a method for producing the switch of the invention in integrated optics.
• This process includes the following steps: a) production in a first substrate, of at least one input optical guide, a first and a second output optical guide, a cavity and a second set of electrodes, the input optical guide and the first output optical guide having an identical optical axis called the first optical axis, the second output optical guide having an optical axis called the second optical axis, the first and second optical axes respectively forming an angle with respect to to an axis of symmetry (S), b) production in a second substrate of a micromirror and of a first set of electrodes, the micromirror being able to move between an output of the input optical guide and inputs of the first and second exit optical guides, the micro-mirror comprising a reflecting part and an actuating part having an axis - of rotation and capable of driving in rotation according to a so-called tilting plane the reflecting part, the tilting plane ement being perpen
• Steps a) b) and c) can be carried out in this order or in a different order. They can also be nested between them.
• the transfer of the second substrate to the first substrate can be carried out before the complete production of the micro-mirror.
• this actuating part can then play the function of the first set of electrodes; the production of said first set is then confused with the production of the actuating part of the mi ⁇ ro-mirror.
• the second substrate is a stack of a first support layer, a second layer and a third layer intended to form the micro-mirror.
• the first support layer is a layer of silicon
• the second layer is a layer of silicon oxide
• the third layer is a film of silicon, the micromirror being produced in said film.
• the second substrate is an SOI (Silicon On Insulator) wafer obtained, for example, by transferring a monocrystalline silicon film onto a silicon support comprising a layer of thermal oxide. This silicon film is optionally epitaxied according to the desired film thickness.
• Step b) of producing the micro-mirror comprises the following steps: etching of the first support layer then of the second layer so as to produce an opening in the substrate exposing part of the third layer, etching of the third layer so as to form the patterns corresponding to the reflecting part and actuating part of the micromirror and to release said parts from the rest of the third layer while allowing said layer to remain at the axis of rotation of the actuating part to allow maintenance from the micromirror to the second substrate, - deposition of a reflective layer on all or part of a lateral face of the reflecting part so as to produce the reflective face of the micromirror.
• the etching of the third layer is carried out so as to obtain a pattern for the reflecting part comprising " said stop.
• FIGS. la and lb illustrate a first example of known switch in free space
• Figures 2a and 2b illustrate a second example of known switch in free space
• Figures 3a, 3b and 3c illustrate an embodiment of a switch according the invention in integrated optics
• FIGS. 4a and 4b illustrate a variant of the previous example in which the micro-mirror has a stop
• FIG. 5 shows another example of a switch according to the invention with several inputs
• FIGS. 6a to 6g show an exemplary embodiment of the switch of Figures 3a, 3b and 3c.
• FIGS. 3a, 3b and 3c illustrate an exemplary embodiment of a switch according to the invention produced in integrated optics.
• Figure 3a is a top view of said switch.
• Figure 3b is a sectional view of the switch along a plane containing the reflective face of the micro-mirror.
• Figure 3c is a perspective view of the micro-mirror used in this switch.
• an optical input channel 31 and two optical output channels 35 are produced. and 37. These optical channels are formed in this example by optical guides.
• an optical guide consists of a central part generally called the heart and surrounding media located all around the heart and which may be identical to each other or different.
• the refractive index of the medium making up the heart must be different and in most cases higher than that of the surrounding media.
• the guide may be a planar guide, when the light confinement is in a plane containing the direction of light propagation or a microguide, when the light confinement is carried out in two directions transverse to the direction of propagation of the light. light.
• the guide will be likened to its central part. or heart and only the hearts of these guides are represented in all of the figures.
• surrounding medium substrate
• the surrounding mediums can be external to the substrate and for example be air.
• the substrate can be monolayer or multilayer.
• an optical guide in a substrate can be more or less buried in this substrate and in particular comprise guide portions buried at depths. variables. This is especially true in ion exchange technology in glass.
• the guides are shown at a constant depth in the substrate.
• the optical axis of the guides 31 and 37 is the same, while the optical axis of the guide 35 makes an angle 2 ⁇ with the optical axis of the guide 31.
• the guides .31 and 35 are arranged symmetrically with respect to an axis of symmetry S.
• the outlet of the guide 31 and the inlet of the guide 35 on the one hand and the inlet of the guide 37 on the other hand are separated by a cavity 39 able to allow the tilting of a micro-mirror 41 according to a tilting plane B.
• the micro-mirror 41 comprises a reflecting part 13 and an actuating part 15 having an axis of rotation 17 parallel to the axis of symmetry S; the reflecting part and the actuating part being integral with one another, the actuating part is capable of driving in rotation according to a so-called tilting plane the reflecting part.
• the tilting plane of the reflecting part is perpendicular to a plane containing the axis of rotation.
• the reflecting part comprises at least one reflecting face R in a plane parallel to the tilting plane of the reflecting part.
• This face R is capable of reflecting a light wave coming from the guide 31 towards the guide 35.
• the reflective face is shown with dotted lines.
• the switch further comprises a device for controlling the rotation of the actuating part so that the latter induces the tilting of the reflecting part and whether the latter can be interposed or not in the optical axis.
• This control device comprises, for example, as shown in FIG. 3b, a first set of electrodes J1 disposed on the actuating part, a second set of electrodes J2 disposed on the substrate, facing the first set, and means (not shown), to apply a potential difference between the two sets of electrodes.
• Each set of electrodes includes at least one electrode.
• the set Jl comprises a single electrode and the set J2 comprises two electrodes J21 and J22 opposite the electrode of the set Jl.
• a first position (shown in Figure 3b) in which one end of the reflecting part descends into the cavity 9 thanks to the electrostatic forces between the electrodes J1 and J21; the reflective face covering at least this end, then cuts the light wave
• the reflecting part of the micro-mirror has a side face which is wholly or partly reflecting; the part capable of reflecting on the lateral face is the reflective face.
• the lateral face is completely reflective and merged with the reflective face, but of course, only the part (useful part) of this lateral face intended to come to be interposed in the optical axis, could have been reflective.
• the actuating part (see FIGS. 3a and 3c) is produced by a central zone on which the electrode J1 is placed, with dimensions close to those of the central zone and a narrower zone on either side of the central zone, arranged along the axis of rotation, to connect the central area to a rigid structure.
• This narrower area forms a hinge for the actuating part.
• the rigid structure to which the movable part is connected is formed by a second substrate S2 disposed on the substrate 1.
• the reflective part is able to move in the plane tilting perpendicular to a plane containing the axis of rotation 17 of the actuating part. The latter makes it possible to tilt the reflecting part according to a leverage effect.
• the useful part of the reflective face can therefore be distant from the axis of rotation and the inter-electrode space can be small (for example a few ⁇ m).
• Figures 4a and 4b show an alternative embodiment of a micro-mirror of a switch in integrated optics
• Figure 4a is a perspective view of the micro-mirror
• Figure 4b is a bottom view thereof.
• This micro-mirror comprises, as previously, an actuating part 15 and a reflecting part 13. These parts are the same as those described with reference to FIGS. 3a to 3c except that the reflecting part also comprises at one of its ends, opposite to that having the useful part of the reflective face, a stop 23.
• This stop makes it possible to limit the displacement of the reflecting part outside the cavity. In this way, it makes it possible in particular to block the micro-mirror in a position for which the reflecting part does not intervene in front of the optical beam.
• the stop is produced for example by a bulge at the end of the reflecting part; the width of said bulge in a plane perpendicular to the tilting plane is greater than the width of the cavity along the same plane.
• FIG. 5 represents another example of a switch of the invention in integrated optics according to a top view.
• This switch comprises the same elements as those of FIG. 3a and in particular a first inlet guide 31 associated with a first outlet guide 35 and a second outlet guide 37 but it also includes a second inlet guide 31 ' associated with a third and a fourth output optical guides 35 'and 37'.
• the guides 31 'and 35' are located symmetrically with respect to an axis of symmetry S 'and form an angle ⁇ with this axis, respectively.
• the reflecting part 13 of the micro-mirror is able to be interposed either between the output of the first optical input guide and the inputs of the first and second optical output guides, or between the output of the second optical input guide and the inputs of the third and fourth optical output guides.
• FIGS. 6a to 6g illustrate an exemplary embodiment of the switch shown in Figures 3a to 3c.
• FIGS. 6a to 6d are sections along a plane parallel to the tilting plane and represent the production of the micro-mirror in a substrate S2
• FIG. 6e represents the preparation of the substrate SI comprising the optical guides
• FIGS. 6f and 6g are sections in a plane perpendicular to the switching plane of the switch after transfer of the micro-mirror to the substrate SI.
• the substrate S2 which is formed in this example by an SOI type wafer "Silicon On Insulator" which corresponds to a stack of three layers: a layer of silicon 50, a layer of silica 51 and a thin film advantageously 52 of monocrystalline silicon.
• FIG. 6b represents a step of epitaxy of the silicon film 52; this step makes it possible to adapt the thickness of the silicon layer to the desired thickness of the micro-mirror to be produced. Of course, if the initial thickness of the film 52 is sufficient, this epitaxy is not necessary.
• the thickness of the silicon layer 54 obtained after epitaxy is for example between 5 and 50 ⁇ m depending on the mechanical characteristics and the reflective surface involved.
• FIG. 6c represents the production of the micro-mirror by etching the layer 54 according to an appropriate pattern.
• two etchings are for example produced: a first etch making it possible to hollow out the central part of the micro-mirror, a second etch making it possible to free the micro-mirror from the rest of the layer 54 (the actuating part is no longer then connected to layer 54 only by the narrow zone corresponding to the hinge of the actuating part).
• the first etching must be carried out from the face of the film 54 opposite the face present in the opening 33. This etching is carried out through an appropriate mask (not shown) and makes it possible in particular to thin the film 54 outside of the zones intended to form the two ends E1 and E2 of the reflecting part.
• the second etching can be carried out from one or other of the faces of the layer 54.
• the mask (not shown) used for this etching must make it possible to etch the layer 54 over its entire remaining thickness so as to obtain the outline of the micro-mirror, that is to say the reflecting part and the movable part as shown in view from above in Figure 3a or Figure 4b in the case of the use of a stop.
• the first and second etchings are chosen independently of one another from an anisotropic chemical etching, for example with a KOH solution or an anisotropic dry etching, for example reactive ion etching from fluorinated gases SF6.
• the layer 54 is itself conductive, as is the case for silicon, then this conductive deposition is not necessary and the part of the layer 54 corresponding to the actuating part then forms the electrode itself.
• FIG. 6e is shown, in section in a plane containing the inlet guide 31 and the outlet guide 37, the substrate SI.
• the optical guides can be produced in the substrate, by all integrated optics techniques and in particular by ion exchange techniques in glass, or by techniques for depositing silica on silicon or on glass or even on fused silica.
• a cavity 39 is also produced in the substrate, for example for a glass substrate, this cavity can be obtained by etching of a chemical type from hydrofluoric acid through a mask (not shown).
• this cavity is preferably produced by an anisotropic dry etching in order to obtain etching blanks of very good perpendicularity with respect to the surface of the substrate.
• This cavity can also be produced by mechanical sawing such as a polished sawing.
• a conductive deposit is also made on the surface of the substrate SI (before or after the cavity is made) which is etched so as to obtain the electrodes J12 and J22 of the set J2.
• This deposit is for example a layer of metallic material such as aluminum, gold, chromium deposited by evaporation or sputtering and etched by chemical etching or reactive ion etching so as to obtain the two electrodes J21 and J22.
• the electrical connections (not shown) of these electrodes to supply means are also produced.
• FIGS. 6f and 6g illustrate the switch of the invention after transfer of the substrate S2 onto the substrate SI so that the micro-mirror is facing the cavity and in particular that the reflecting part can have a rocking movement at inside the latter.
• the reflective part of the micro-mirror is in the high position, in other words, the reflective face is not interposed in the optical axis of the guides 31 and 37 and the light beam conveyed by the guide 31 is transmitted directly via the cavity
• the reflecting part of the micro-mirror is in the low position, in other words, the reflecting face is interposed in the cavity 39 with the optical axis of the guide 31 and the light beam conveyed by the guide 31 is reflected by the reflective face towards the guide 35 which is not in the section plane of FIG. 6g.
• the transfer of the substrate S2 onto the substrate SI can be carried out by all the known techniques and in particular by the techniques of molecular adhesion or again by an appropriate bonding (for example a bead of polymer adhesive) or also by brazing.
• a stack of the substrate S2 as shown in FIG. 6a can also be produced by a silicon support on which a thermal oxidation is carried out to form the layer of silica and finally a deposit of polycrystalline silicon of thickness suitable for producing the micro -mirror.
• the substrate S2 is transferred to the substrate SI after the realization of the micro-mirror; of course the substrate S2 can be transferred onto the substrate SI before the production of said micro-mirror or at least before its release so that the transfer takes place with a more rigid structure mechanically.
• the embodiments described above relate to switches in integrated optics using optical guides.
• the switch of the invention can be made in free space.
• the input and output guides are optical fibers which can be placed in a substrate in which rails (for example "v" grooves) have been arranged to hold said fibers.
• a cavity for moving the micro-mirror can also be provided between the ends of the fibers.
• the micro-mirror can be as in the case of optical guides placed on an independent substrate, transferred onto the fiber substrate.

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• Physics & Mathematics (AREA)
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• Optics & Photonics (AREA)
• Mechanical Light Control Or Optical Switches (AREA)

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  • 2002-01-18 FR FR0200598A patent/FR2835062B1/fr not_active Expired - Fee Related
• 2003
  • 2003-01-16 US US10/501,528 patent/US20050163417A1/en not_active Abandoned
  • 2003-01-16 CA CA002473080A patent/CA2473080A1/fr not_active Abandoned
  • 2003-01-16 WO PCT/FR2003/000130 patent/WO2003062889A2/fr not_active Application Discontinuation
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