FR2831282A1 - Optical wave transmission integrated optical structure having integrated principle part/distant secondary part with internal surface waves circulating and auxiliary phase modulated part control unit activated. - Google Patents

Abstract

The integrated optical structure has a principal part integrated with the optical transmission and a secondary part at a distance. The secondary part (5) has an internal surface (3) at a distance circulating the optical waves in a guide. There is an auxiliary secondary part (16) near the surface which is phase modulated, with a control unit (9,10,15).

Description

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OPTICAL DEVICE WITH INTEGRATED STRUCTURE
FOR TRANSMITTING AN OPTICAL WAVE
The present invention relates to the field of optical devices with integrated optical structure for transmitting an optical wave.

 Document WO 00 044 16 describes an optical semiconductor device which comprises, in a layer, a region having a rib so as to constitute an optical guide as well as resistive heating members making it possible to heat said region in order to vary the optical characteristics of this waveguide.

 Document WO 00/58 776 describes an optical semiconductor device which comprises a region having a rib so as to constitute an optical waveguide and, on either side of this region, parts making it possible to vary the number of carriers electric charge in this region so as to vary the optical characteristics of the waveguide.

 The aim of the present invention is to propose an optical device with integrated optical structure making it possible to act on an optical wave transmitted in a much more advantageous manner.

 The optical device with integrated optical structure for transmitting an optical wave according to the invention comprises at least one main part in which is integrated at least one optical transmission core so as to constitute at least one optical guide and at least one secondary part having an internal surface spanning at least part of the peripheral surface of said transmission core.

 According to the invention, said internal surface of said secondary part is placed at a distance from the peripheral surface of said transmission core such that the optical wave circulating in said

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 optical guide reaches said internal surface of said abutment; said secondary part has at least one auxiliary part adjacent to or adjacent to said surface and of which at least one optical property is modular; and, moreover, controllable means are adapted to act on said auxiliary part so as to modulate its aforementioned optical property in order to modify at least one characteristic of the transmitted optical wave, in particular its phase, during its passage in front of said part auxiliary.

 According to a variant of the invention, said auxiliary part of said secondary part constitutes at least part of a layer of said structure.

 According to another variant of the invention, said auxiliary part of said secondary part constitutes at least one wall extending laterally to said transmission core.

 According to a variant of the invention, said auxiliary part of said secondary part is made of a material, the aforementioned optical property of which can be modulated by electric, light or thermal controllable means.

 According to a variant of the invention, said auxiliary part of said secondary part is made of a material into which carriers of electrical charges can be introduced or injected under the effect of controllable electrical, light or thermal means.

 According to another variant of the invention, said auxiliary part of said secondary part is made of a material the stresses of which are liable to vary under the effect of controllable electrical, light or thermal means.

 The present invention will be better understood from the study of optical devices with integrated optical structure for transmitting an optical wave, described by way of nonlimiting examples and illustrated by the drawing in which: - Figure 1 shows a cross section of a first optical device with integrated structure according to the present invention; - Figure 2 shows a partial longitudinal section of the optical device of Figure 1;

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 - Figure 3 shows a diagram of the phase of the optical wave flowing in the optical device of Figures 1 and 2, in two places of the latter; - Figure 4 shows a cross section of a second optical device with integrated optical structure according to the present invention; - Figure 5 shows a partial longitudinal section of the optical device of Figure 4; - Figure 6 shows a diagram of the phase of the optical wave transmitted by the optical device of Figures 4 and 5, in two longitudinal locations thereof; - Figure 7 shows a cross section of a third optical device with integrated optical structure according to the present invention; - Figure 8 shows a partial longitudinal section of the optical device of Figure 7; - Figure 9 shows a cross section of a fourth optical device with integrated optical structure according to the present invention; - And Figure 10 shows a cross section of a fourth optical device with integrated optical structure according to the present invention.

 Referring to FIGS. 1 and 2, it can be seen that an integrated optical structure 1 has been shown which comprises a front main part 2 and a rear secondary part 3.

 The secondary part 3 comprises a base layer 4 made of a material such as silicon.

 The main part 2, which is formed on the surface 5 of the layer 4 of the secondary part 3, comprises a layer 6, for example made of undoped silica, into which is longitudinally integrated a longitudinal core 7a of optical transmission of square section or rectangular, for example made of doped silica, so as to constitute an optical waveguide 7.

 As seen in Figure 2, a curve 8 in the form of

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 bell represents the amplitude of an optical wave transported by the optical micro-guide 7, the part of maximum amplitude of which is located in the region of the optical transmission core 7a.

 The distance e separating the front internal surface 5 of the layer 4 from the secondary part 3, on which the main part 2 and the rear face of the optical transmission core 7a is formed, is such that the optical wave circulating in the micro-guide optic 7 as represented by curve 8 reaches this internal surface 5.

une région n+, et une région longitudinale 10, par exemple dopée au bore, de façon à constituer une région p+, ces régions 9 et 10 étant adjacentes à la surface interne 5 et présentant une distance d les séparant et une longueur 1. Dans la couche de base 4 est ainsi formé un dispositif bipolaire 4a du type diode. On either side of the projection of the optical transmission core 7a on the surface 5 of the secondary part 3 and opposite, the base layer 4 constituting this part has a doped longitudinal region 9, for example at arsenic, so as to constitute

an n + region, and a longitudinal region 10, for example doped with boron, so as to constitute a p + region, these regions 9 and 10 being adjacent to the internal surface 5 and having a distance d separating them and a length 1. In the base layer 4 is thus formed a bipolar device 4a of the diode type.

 The layer 6 of the main part 2 has, above the longitudinal regions 9 and 10, wells or recesses 11 and 12 in which is deposited an electrically conductive material so as to form metallizations of electrical connection 13 and 14 These metallizations 13 and 14 are electrically connected to a circuit 15 for power supply and control.

 The longitudinal regions 9 and 10 determine between them an auxiliary part 16 of the layer 4 of the secondary part 3, adjacent or adjacent to the internal surface 5, which runs at a distance along the longitudinal transmission core 7a.

 In the absence of supply of the bipolar system 4a, the auxiliary part 16 comprises a density of carriers of electrical charges, the value of which depends substantially on the doping of the material constituting the base layer 4.

 As a result, when the longitudinal regions 9 and 10 are not supplied with electrical energy, the propagation of the optical wave transported by the optical micro-guide 7 is not substantially

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 not affected by the presence of the bipolar system 4a when it passes in front of the auxiliary part 16 of the secondary part 3.

 In the presence of a supply of the bipolar system 4a, the density of electric charge carriers in the auxiliary part 16 is modified.

 As a result, when the longitudinal regions 9 and 10 are supplied with electrical energy by the circuit 15, the optical properties, in particular the refractive index, of the auxiliary part 16 of the secondary part 3 are modified. This modification or variation is a function of the quantity of carriers of electrical charges which it contains and therefore of the value of the electrical energy delivered to the bipolar system 4a by the circuit 15.

 The modification of the optical properties of the auxiliary part 16 of the secondary part 3, distant from the transmission core 7a, generates a modification of the characteristics of the optical wave, in particular of its phase, during its passage in front of this auxiliary part 16.

 More particularly, as can be seen in diagram 17 of FIG. 3, the phase of an optical wave taken after it has passed in front of the auxiliary region 16, as a function of the deviation from the median plane of the optical micro-guide 7 perpendicular to the internal surface 5 and in the case of a polarization of an optical wave in TE mode, passes from a slightly arched curve 18 to a slightly arched curve 19 offset.

 In an exemplary embodiment, the optical transmission core 7a can have a thickness of approximately 4.5 microns and a width of approximately 6.5 microns, the distance e separating the auxiliary part 16 and the transmission core 7a can be equal to approximately 12 microns, the width d of the auxiliary part 16 separating the doped longitudinal regions 9 and 10 can be between 10 and 30 microns and the length 1 of these regions can be between 10 and 3000 microns.

 Referring to Figures 4 and 5, we see that there is shown an optical device with integrated optical structure 20 which comprises a

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 rear base layer 21, for example made of silicon, on which a front main part 22 is formed which comprises a layer 23, for example made of undoped silica, in which a longitudinal optical transmission core 24a is formed so as to constitute a microphone - optical guide 24.

 The optical structure 20 also comprises a secondary part 25 which comprises a longitudinal strip 26 situated in front of the optical transmission core 7a and integrated in the layer 23 of the main part 22.

 This rectangular longitudinal strip 26 extends parallel to the interface 27 between the layers 21 and 22 and has a rear internal face 28 which runs along the front face of the longitudinal optical transmission core 24a, at a distance e such that, as in 'previous example, the optical wave transported by the optical micro-guide 24 reaches this internal face 28. The longitudinal strip 26 is rectangular and has a width d and a length 1.

 The front face 29 of the layer 23 carries two longitudinal strips 30 and 31 which extend above and at a distance from the longitudinal edges of the integrated strip 26 and which constitute electrodes. These electrodes 30 and 31 are connected to an electrical power supply and control circuit 32.

 When the electrodes 30 and 31 are supplied with electrical energy by the circuit 32, an electric field is established to which the longitudinal strip 26 which constitutes an auxiliary part is subjected.

 Under the effect of this electric field, the optical properties, in particular its refractive index, of the longitudinal strip 26 change. It follows that when an optical wave transported by the optical micro-guide 24 passes in front of the longitudinal strip 26, its optical characteristics, in particular its phase, are modified accordingly.

 Referring to FIG. 6, it can be seen that a diagram 33 has been shown of the phase of an optical wave after it has passed in front of the longitudinal strip 26. This diagram shows, in

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 function of the distance from the median plane of the optical guide 24 perpendicular to the internal face 28 of the longitudinal strip 26 and in the case of polarization in TE mode, a curve 34 of the phase of the optical wave in the absence of an electric field in the longitudinal strip 26 and a curve 35 offset from the phase of the optical wave in the presence of an electric field in the longitudinal strip 26.

 By way of example, the longitudinal strip 26 can be made of a material whose optical properties can be adjusted by applying an electric or magnetic field, in particular lithium tantalate, lithium niobate or quartz.

 In an exemplary embodiment, the transmission core 24a may have a width and a thickness of approximately 4.5 microns, the longitudinal strip 26 may have a thickness of approximately 0.7 microns, its width d may be between 2 and 25 microns and its length l can be between 10 and 3000 microns. The distance e between the transmission core 24a and the auxiliary strip 26 can be between 6 and 12 microns. The distance between the transmission core 24a and the base layer 24 can be between 6 and 12 microns and the distance between the longitudinal strip 26 and the front face 29 can be between zero and 4 microns.

 Referring to FIGS. 7 and 8, it can be seen that an optical device with integrated optical structure 36 has been shown which comprises a rear base layer 37, for example made of silicon, and a front main part 38 which comprises a layer 38a, for example in undoped silica, and a longitudinal transmission core 39a, for example in doped silica, integrated in the layer 38a so as to constitute an optical micro-guide 39.

 The optical structure 36 comprises a secondary part 40 which comprises a longitudinal well or recess 41 formed from the rear in the base layer 37 and to a determined depth such that a longitudinal strip 43 remains between the bottom of the well 41 and the interface 42 between the base layer 37 and the layer 38a of the main part 38, the well 41 extending longitudinally

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 facing the transmission core 39a so that the longitudinal strip 43 has a width d and a length 1.

 The walls of the well 41 and the rear face of the base layer 37 are covered with an insulating layer 44.

 A layer 45 of an electrically conductive material, such as aluminum, covers, in the well 41, the insulating layer 44 and has, on either side of the well 41, longitudinal parts of electrical connection 45a and 45b on its rear face. These connection parts 45a and 45b are connected to a circuit 48 for power supply and control.

 As in the previous examples, the distance e separating the front internal surface 42 of the layer 43 from the secondary part 40, on which the main part 38 is formed, and the rear face of the optical transmission core 39a is such that the wave optics circulating in the optical micro-guide 39 as represented by the curve 49 reaches this internal surface 42.

 When the layer 44 is supplied with electrical energy by the supply and control circuit 48, there is a rise in the temperature of the auxiliary layer 43. This rise in temperature has the effect of modifying the optical properties, more particularly its refractive index, of the auxiliary layer 43 so that, when an optical wave circulates in the optical guide 39, the optical characteristics of this optical wave, in particular its phase, are modified.

 In particular, the modification of the phase of the optical wave can correspond to that of one of FIGS. 3 and 6.

 As an exemplary embodiment, the transmission core 39a may have a width and a thickness of approximately 4.5 microns, the auxiliary layer 43 may have a thickness between 1 and 10 microns, its width d may be between 10 and 50 microns and a length 1 can be between 100 and 3000 microns. The distance e between the transmission core 39a and the auxiliary layer 43 can be between 8 and 20 microns.

 Referring to Figures 9 and 10, we see that we have

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 shown an optical device with integrated optical structure 50 which comprises a base layer 51, for example made of silicon, on which a main part 52 is formed which comprises a layer 53, for example made of undoped silica, in which a longitudinal core is integrated of optical transmission 54a, for example of doped silica, so as to form an optical guide 54.

 The structure 50 further comprises a secondary part 55 which preferably comprises a masking layer 56 deposited on the front face 57 of the layer 53 and in which is formed an opening 58 which runs at a distance along the upper face of the longitudinal transmission core 52a .

The secondary part 55 further comprises, at a distance from the opening 58 of the layer 56, a laser emitter 59 connected to a circuit 60 for supplying electrical energy and for control and fixed for example by a layer of glue 56a
The emitter 59 is arranged and adapted so as to cause a photo-excitation of an auxiliary region 61 of the base layer 51 through the main part 50 transparent to the emission. This excitation of the auxiliary region 61 has the effect of modifying its optical properties and more particularly its refractive index.

 As in the previous examples, the distance e separating the internal surface 62 of the layer 51, spanning the optical transmission core 54a from a distance, and the rear face of the optical transmission core 54a is such that the optical wave transported by the microphone -optical guide 54 as represented by the curve 63 reaches this internal surface 62.

 As in the previous examples, when the auxiliary region 61 of the base layer 51 is excited by the emitter 59, the optical characteristics, in particular its phase, of an optical wave transported by the optical guide 54 are modified during its passage in front of this auxiliary region 61.

 In particular, the modification of the phase of the optical wave can correspond to that of one of FIGS. 3 and 6.

 As an exemplary embodiment, the transmission core

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 39a may have a width and a thickness of approximately 4.5 microns, the auxiliary region 61 may have a width d of between 10 and 50 microns and a length 1 of between 100 and 3000 microns.

The distance e between the transmission core 39a and the auxiliary region 61 can be between 8 and 20 microns.

 In a variant, the transmitter 59 could be placed at the rear and act on the auxiliary part 61 which would be provided at the bottom of a well.

 In general, it follows from the above examples that the modification of at least one characteristic of the optical wave transported by the optical guide of the optical structures described occurs without modification of the optical properties of their main part and more particularly without modification of the optical properties of their optical transmission core.

 The variation of at least one characteristic of the optical wave transported by the optical guide of the optical structures described in the preceding examples depends on or is a function of the positioning of the auxiliary part of their secondary part, distant from their optical transmission core, of the dimensioning of this auxiliary part, of the variation of the optical properties of this auxiliary part which can be commanded or controlled by their supply and control circuit.

 The examples have been described by considering that only the phase of the transported optical wave is modified. However, the secondary part of the optical structures described could also be used to cause attenuation or amplification of the optical wave transported.

 The examples described use electrical, thermal and electronic characteristics of the aforementioned auxiliary parts in order to modify the optical properties of the latter. Combined uses of these characteristics or the implementation of other characteristics are immediately possible.

 As examples of applications, the optical structures described can be used in Mach- interferometers

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 Zehnder, known per se, so as to constitute variable optical wave attenuators, optical wave switches or optical wave samplers or extractors or devices serving as compensators for mode dispersions or birefringence compensators.

 The present invention is not limited to the examples described above. Many alternative embodiments are possible without departing from the scope defined by the appended claims.

Claims (6)

1. Optical device with integrated optical structure for transmitting an optical wave, comprising at least one main part in which is integrated at least one optical transmission core so as to constitute at least one optical guide and at least one secondary part having a internal surface running at a distance from at least part of the peripheral surface of said transmission core, characterized in that said internal surface (5,28, 42,62) of said secondary part (3,25, 40,61) is placed at a distance from the peripheral surface of said transmission core such that the optical wave circulating in said optical guide reaches said internal surface of said secondary part, that said secondary part has at least one auxiliary part (16,26, 43,61) adjacent or adjacent to said surface and of which at least one optical property is modular, and that it further comprises controllable means (9, 10,15; 30,31, 32; 45,48; 59,60) adapted to act on said auxiliary part so as to modulate its aforementioned optical property in order to modify at least one characteristic of the transmitted optical wave, in particular its phase, during its passage in front of said auxiliary part.  2. Device according to claim 1, characterized in that said auxiliary part of said secondary part constitutes at least part of a layer of said structure.  3. Device according to one of claims 1 and 2, characterized in that said auxiliary part of said secondary part constitutes at least one wall extending laterally to said transmission core.  4. Device according to any one of the preceding claims, characterized in that the said auxiliary part of the said secondary part is made of a material the above-mentioned optical property of which can be modulated by electric, light or thermal controllable means. <Desc / Clms Page number 13>  5. Device according to any one of the preceding claims, characterized in that said auxiliary part of said secondary part is made of a material into which carriers of electrical charges can be introduced or injected under the effect of electrically controllable, luminous means or thermal.  6. Device according to any one of the preceding claims, characterized in that said auxiliary part of said secondary part is made of a material whose stresses are liable to vary under the effect of controllable electrical, light or thermal means.