Photonic system comprising a photonic chip and a multiplane conversion device

Abstract

The invention relates to a photonic device (1) comprising a photonic chip (PIC) having at least one waveguide (WG) arranged in the principal plane (P) and at least one receiving zone (Z) arranged on a surface of the photonic chip (PIC), the waveguide (WG) and the receiving zone (Z) being optically coupled to each other to propagate internal light radiation consisting of at least one mode. The photonic device also comprises a multiplane conversion device (MPLC) assembled to the photonic chip (PIC) and comprising a first optical port (P1), optically associated with the receiving zone (Z) of the photonic chip (PIC), and a second optical port (P2) for receiving external radiation, the external light radiation being capable of propagating between the second optical port (P2) and the first optical port (P1) during a plurality of reflections and / or transmissions on microstructured areas of the multiplane conversion device (MPLC).Figure to be published with the abbreviation: Fig. 1.

Description

Title of the invention: Photonic system comprising a photonic chip and a multiplane conversion device. FIELD OF THE INVENTION

[0001] The present invention relates to the field of photonic systems. It has very varied applications, for example for inter- and intra-chip optical communications, particularly for data centers, for the realization of sensors in the field of biology or distance measurement (LIDAR), for telecommunications. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] Photonic integrated circuits (or photonic chips) are integrated circuits capable of generating, detecting, or manipulating light radiation. Like electronic integrated circuits, these circuits can incorporate multiple functional blocks, such as laser radiation sources, switches, modulators, and power distributors, these blocks being interconnected by waveguides. The combination of these blocks makes it possible to perform complex light radiation processing in a much smaller volume, at a lower cost, and with increased performance compared to non-integrated technologies using separate optical components.This is particularly notable for silicon-based photonic integrated circuits, which leverage highly mature microelectronic techniques for manufacturing electronic integrated circuits to mass-produce optical circuits. Some optical functional blocks may include, on a predominantly silicon platform, layers or vignettes of IILV semiconductors, formed by epitaxy or transferred by bonding onto this platform.

[0003] The chip remains in all cases planar in shape, and generally rectangular, having sides with dimensions on the order of a centimeter or a few centimeters and a relatively small thickness, on the order of a millimeter or a few millimeters. The smaller faces form slices of the photonic chip, and the larger faces form the main surfaces of the photonic chip.

[0004] In operation, the photonic chip is carried by a support, designated "PCB" (for "Printed Circuit Board" or "Printed circuit support") on which also rest the other electronic and / or optical components, integrated or not, of a more complex system.

[0005] It is often necessary to inject into a waveguide of a photonic chip a Light radiation is used for processing, or to extract light radiation that the chip has produced and / or processed. The light radiation injected into or extracted from the chip can propagate in free space or be guided by an optical fiber. Coupling occurs at an emission / reception zone of the chip.

[0006] The possible coupling configurations between the light radiation and the chip can be of the "in-plane of the chip" or "out-of-plane of the chip" type. Reference may be made in this regard to the document by Riccardo Marchetti, Cosimo Lacava, Lee Carroll, Kamil Gradkowski, and Paolo Minzioni, "Coupling strategies for Silicon photonics integrated chips [Invited]", Photon. Res. 7, 201-239 (2019).

[0007] Depending on whether this coupling is "in-plane" or "out-of-plane", the emission / reception area of ​​the photonic chip is arranged on one of its slices or on a main surface.

[0008] The aforementioned document indicates that this coupling, particularly when it occurs with optical fibers, is challenging. This is primarily due to the large disparity in size and modal distributions between external light radiation and that propagating in a waveguide of the photonic chip. More generally, the guided modes in a photonic chip differ from the guided modes in a fiber or those of free-space radiation, which induces optical losses at the coupling point occurring in the chip's emission / reception zone. For this reason, efficient coupling between the light radiation and the photonic chip presents a significant challenge. SUBJECT OF THE INVENTION

[0009] One object of the invention is to provide a solution, at least partial, to these problems. BRIEF DESCRIPTION OF THE INVENTION

[0010] To achieve this goal, the object of the invention proposes a photonic device comprising: - a photonic chip extending along a principal plane and comprising at least one waveguide disposed in the principal plane and at least one receiving zone disposed on a surface of the photonic chip, the waveguide and the receiving zone being optically coupled to each other to propagate an internal light radiation consisting of at least one mode; - a multiplane conversion device assembled to the photonic chip and comprising a first optical port, optically associated with the receiving area of ​​the photonic chip, and a second optical port for receiving external radiation, the external light radiation being capable of propagating from the second optical port to the first optical port during a plurality of reflections and / or transmissions on micro-structured areas of the multiplane conversion device, the micro-structured areas being configured to guide at least part of the external radiation received on the second optical port and conform this part to the mode of the internal light radiation at the level of the first optical port.

[0011] According to another aspect, the invention proposes a photonic device comprising: - a photonic chip extending along a principal plane and comprising at least one waveguide disposed in the principal plane and at least one emission zone disposed on a surface of the photonic chip, the waveguide and the emission zone being optically coupled to each other to propagate an internal light radiation consisting of at least one mode; - a multiplane conversion device assembled to the photonic chip and comprising a first optical port, optically associated with the emission area to receive the internal light radiation, and a second optical port to emit external radiation of a determined shape, the internal light radiation being capable of propagating from the first optical port to the second optical port during a plurality of reflections and / or transmissions on microstructured areas of the multiplane conversion device, the microstructured areas being configured to guide at least one mode of the internal light radiation received at the level of the first optical port and conform it to the shape determined at the level of the second optical port.

[0012] According to other advantageous and non-limiting features of the invention, taken alone or in any technically feasible combination: - the multiplane conversion device consists of a monolithic optical piece in which the external radiation propagates, the monolithic optical piece having at least one face bearing the microstructured areas; - the multiplane conversion device comprises two optical parts each having a reflective face, the reflective faces of the optical parts being arranged opposite each other, and at least one of the reflective faces bearing the microstructured areas; - one of the reflective optical parts is formed by a surface of the photonic chip; - the multiplane conversion device includes an assembly piece for joining the two reflective optical parts together; - the assembly piece is positioned as a spacer between the two reflective optical pieces or as a support for the two reflective optical pieces; - the emission or reception zone is arranged on a face called "main" of the photonic chip, parallel to the main plane; - the emission or reception area is arranged on a slice of the photonic chip (PIC), the slice forming a face of the photonic chip perpendicular to the main plane; - the second optical port (includes an optical fiber network (AF); - the second optical port includes at least one multimode fiber. - the first optical port includes a microlens array; - the first optical port includes an optical guide; - the optical guide includes a mirror, a prism or a periscope; - the photonic device includes a support on which the photonic chip and the multiplane conversion device are arranged; - the support includes a reflective layer forming one of the reflective optical parts of the multiplane conversion device; - the photonic chip includes at least one photodetector optically associated with the waveguide (WG). BRIEF DESCRIPTION OF THE FIGURES

[0013] Other features and advantages of the invention will become apparent from the detailed description of the invention which follows with reference to the accompanying figures in which:

[0014] [Fig.1]

[0015] The [Fig.1] represents a schematic diagram according to a first embodiment;

[0016] [Fig.2] Fig.2 represents a schematic diagram according to a second method of implementation lisation;

[0017] [Fig. 3] Fig. 3 represents a multiplane MPLC conversion device that can be operated in an optical system conforming to the invention;

[0018] [Fig.4] Fig.4 represents one implementation method of a device photonics according to the invention;

[0019] [Fig.5]

[0020] [Fig.6a]

[0021] [Fig.6b]

[0022] [Fig.6c]

[0023] [Fig. 7] Figures 5, 6a, 6b, 6c, 7 illustrate possible assemblies between a a multiplane conversion device and a photonic chip to form a photonic device according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The term "shape" of a light radiation shall be designated as the transverse distribution of the amplitude and phase of the mode or the combination of the transverse distributions of amplitude and phase of the modes composing this radiation.

[0025] Figures 1 and 2 illustrate the principles implemented in a photonic system which is the subject of this description. [Fig. 1] shows a side view of a first embodiment and [Fig. 2] a top view of a second embodiment.

[0026] These schematic diagrams show a photonic device 1, formed here of a simple PIC photonic chip to which a multiplane MPLC conversion device is assembled.

[0027] As is well known, the PIC photonic chip can incorporate, in an integrated manner within a package, a variety of active elements such as lasers, phase modulators, interferometers, and photodetectors, combined with passive elements such as waveguides and optical couplers, enabling the PIC chip to be fully functional. The chip can have an essentially rectangular shape and extend along a principal plane P.

[0028] In the context of this description, the PIC photonic chip contains at least one waveguide WG extending in the principal plane P of the PIC photonic chip. The waveguide WG is coupled to at least one emission zone or at least one reception zone disposed on a surface of the PIC photonic chip. The waveguide WG and the emission or reception zone are optically coupled to each other to propagate light radiation internal to the chip.

[0029] An emission zone or a reception zone corresponds to a portion of the surface of the PIC photonic chip at which light radiation emerges or is injected. For simplicity of writing, such a zone will be designated by the expression "emission / reception zone." This surface may correspond to a principal surface of the PIC chip, that is to say, a surface parallel to the principal plane P, or to a slice of the chip 1, that is to say, a surface perpendicular to the principal plane P. The term "active surface" will designate the surface of the chip on which the emission / reception zone is arranged. A PIC photonic chip of the photonic device 1 which is the subject of this description may comprise several emission / reception zones, arranged on the active surface in any suitable arrangement. These zones may, in particular, be arranged along a line or in a matrix on the active surface.

[0030] Light radiation internal to the PIC photonic chip is composed of at least one mode and therefore propagates in the waveguide WG to / from the emission / reception zone. At this zone, the internal radiation has a first shape determined by the mode(s) propagating in the waveguide WG.

[0031] The radiation propagating in the waveguide WG does not generally have a symmetrical shape in revolution: it can, for example, take an elongated shape liptic or rectangular with rounded corners, the major axis of the ellipse or the length of the rectangle being arranged in the principal plane P and the minor axis of the ellipse or the width of the rectangle being arranged perpendicular to this principal plane P.

[0032] Returning to the description of the schematic diagrams in Figures 1 and 2, the photonic system 1 also includes a multiplane MPLC conversion device. The multiplane MPLC conversion device is assembled, either directly or indirectly, to the PIC photonic chip, directly in the case of the schematic diagrams in Figures 1 and 2. The multiplane MPLC conversion device includes a first optical port PI, optically connected to the transmit / receive area of ​​the photonic chip by means of the assembly of the two elements together.

[0033] In the schematic diagram shown in [Fig. 1], the coupling between the MPLC multiplane conversion device and the PIC photonic chip is achieved "from above", outside the plane P of the chip. For this purpose, the emission / reception area Z of the PIC photonic chip is arranged on its main surface, optically coupled to the waveguide WG by means of a surface coupler such as a surface grating (according to the Anglo-Saxon terminology usually used in this field) or such as retroreflecting mirrors (in English).

[0034] In the schematic diagram shown in [Fig.2] (top view), the coupling between the MPLC multiplane conversion device and the PIC photonic chip is achieved "edge-on-edge", in the plane of the chip. In this configuration, the transmit / receive area Z of the PIC photonic chip is arranged on one of its edges, via an edge coupler (using the Anglo-Saxon terminology commonly employed in this field).

[0035] The MPLC multiplane conversion device also includes a second optical port P2 for receiving / emitting light radiation, referred to as "external", external to the photonic device 1. Light radiation is likely to propagate between the first optical port PI and the second optical port P2 during a plurality of reflections and / or transmissions on microstructured areas of the multiplane conversion device, as will be explained in more detail in a later section of this description.

[0036] The propagation of this light radiation is directed from the first optical port PI to the second port P2 when the source of this radiation is coupled to the first optical port PI, on the side of the PIC photonic chip, which is configured in this case "in transmitting mode". Conversely, the propagation of this light radiation is directed from the second optical port P2 to the first optical port PI when the source is located on the side of the second optical port P2, the PIC photonic chip being configured in this case "in receiving mode".

[0037] By "optical port" is meant any part or passage allowing the introduction / extraction of light radiation into the MPLC multiplane conversion device.

[0038] In all cases, the external light radiation, which emerges from the photonic system 1 through the second optical port P2 or is injected into the photonic system 1 through this second optical port P2, has a shape that is distinct from the first shape of the internal radiation propagating within the PIC photonic chip. The shape of the external radiation can be imposed by a waveguide, for example, an optical fiber or a bundle of optical fibers that connects the photonic system 1 to a source or receiver external to this system. It can also be imposed directly by this source or receiver when the propagation of the external light radiation between the photonic system 1 and this source or receiver occurs in free space.

[0039] By way of example, an external radiation carried by a single-mode optical fiber whose end would be placed at the level of the second optical port P2 produces, at the level of this second port, a light radiation of Gaussian shape, therefore exhibiting a rotational symmetry, which does not correspond to the generally elliptical shape of the internal radiation propagating in the waveguide WG of the PIC photonic chip.

[0040] The shape of the light radiation at the second optical port is not necessarily perfectly determined. Thus, propagation to this second optical port from a distant external source can cause significant distortion of the radiation, affecting its shape and potentially making it variable over time. This is also the case when propagation occurs partly via a multimode waveguide, as not all modes are activated with the same intensity over time, which can make the shape of the radiation from this fiber variable over time. The shape of this radiation can also be affected by temperature variations or mechanical stresses to which a fiber may be subjected.

[0041] As stated in the introductory part of this application, the shape of the external radiation is generally not adapted to the first shape of the light radiation determined by the mode(s) propagating in the PIC photonic chip. Due to this difference in shape, the coupling of the light radiation to the PIC chip is subject to significant losses.

[0042] To counter this, the MPLC multiplane conversion device is configured to perform a shape conversion to the radiation propagating between the first and second optical ports. Photonic chip capable of operating in emission mode

[0043] When the PIC photonic chip is capable of operating in emission mode, for example When it includes a light source coupled by the waveguide WG to an emission zone, the MPLC multiplane converter can be configured to transform the optical mode produced at this emission zone, at the first optical port PI, into external radiation with a selectable shape. In other words, the MPLC multiplane converter is configured to guide the internal light received at the first optical port PI and conform it to the chosen (i.e., determined) shape at the second optical port P2. This shape can be specifically chosen to efficiently inject itself into an optical fiber located at its second optical port P2, for example, by producing Gaussian-shaped radiation at this second optical port.

[0044] If the internal radiation within a WG waveguide of the photonic chip is composed of a plurality of modes, it is possible to configure the MPLC multiplane conversion device as a spatial demultiplexer, some at least of the modes of this internal radiation being able to be isolated from each other and transformed to, for example, be injected into a dedicated optical fiber at the level of the second optical port P2.

[0045] When the PIC photonic chip comprises one or more light sources whose radiation is distributed across a plurality of disjoint waveguides, the MPLC multiplane conversion device can be configured to transform the optical mode composing the internal radiation propagating in each waveguide WG into radiation whose shape, at the second optical port P2, allows its efficient injection into a dedicated optical fiber. Alternatively, the optical modes propagated collectively by the waveguides to the emission zones of the PIC photonic chip can be processed by the MPLC multiplane conversion device, configured as a spatial multiplexer, to be respectively conformed to the modes of a multimode optical fiber.

[0046] When the shape of the radiation produced at the second optical port P2 is not constrained by a waveguide, optical fiber, or optical fiber bundle, for example, and the external radiation is intended to propagate in free space, it may nevertheless be desirable for this external radiation to consist of modes chosen from a predetermined family of modes, to facilitate its processing downstream of propagation. This could, for example, be a family of Hermite-Gauss modes (with a circular or elliptical support), or generalized Hermite-Gauss, Laguerre-Gauss, Slepian, LP, or OAM modes, or any spatial unitary transformation of these mode families.

[0047] The MPLC multiplane conversion device can perform other treatments on the radiation produced by the PIC photonic chip besides those aimed at transforming its shape. This device can, for example, perform a coherent or incoherent combination of the radiation produced. Photonic chip capable of functioning in reception

[0048] The PIC photonic chip can also be adapted to operate in receive mode to process internal radiation propagating in the waveguide WG. This processing can be of any kind, for example, detecting the intensity of this radiation by means of a photodetector, or combining internal radiation propagating in a plurality of waveguides WG of the chip. It can also involve coherent detection via a local oscillator, phase-change demodulation by interfering two consecutive symbols, or improving the eye diagram.

[0049] The MPLC multiplane conversion device can be configured in this case to guide at least a portion of the external radiation received at the second optical port P2 and conform this portion to the mode(s) of the internal light radiation at the first optical port PL

[0050] When this external light radiation is guided to the second optical port P2 of the MPLC multiplane conversion device by an optical fiber, this device can be configured to transform the typically Gaussian shape of the light radiation produced by this optical fiber into a shape corresponding to the optical mode associated with the waveguide WG of the PIC photonic chip.

[0051] When external radiation is guided by several fibers or by a multimode optical fiber, the MPLC multiplane conversion device can be configured to decompose this external radiation according to at least some of the modes guided by the fiber or fibers and to inject it into a plurality of waveguides WG of the photonic chip, via a plurality of receiving zones to which these waveguides are respectively coupled.

[0052] Similarly, when external radiation propagates in free space to the second optical port P2, the MPLC multiplane conversion device can be configured to spatially decompose at least a portion of this radiation into a plurality of modes, and to guide the propagation of these modes to the first optical port PI and conform them to the optical modes of one or a plurality of waveguides WG of the PIC photonic chip.

[0053] The MPLC multiplane conversion device can perform other treatments on the radiation produced by the PIC photonic chip besides those aimed at transforming its shape. This device can, for example, perform a coherent or incoherent combination of the radiation produced.

[0054] Configuration of a multiplane conversion device.

[0055] In a very general way, a multiplane conversion device performs a unitary transformation of the shape of an incident light ray. This transformation can be precisely described in modal form, that is to say, in de defining a relationship between modes of a first family of modes defined in a first transverse plane (for example, at the first optical port P1) and modes of a second family of modes defined in a second transverse plane (for example, at the second optical port P2). The mode families are generally formed from orthonormal bases and allow for the optimal decomposition of any light radiation at each of the optical ports.

[0056] Within the framework of this description, the modes of the first family may, for example, be chosen to correspond to the optical modes of a waveguide or a plurality of waveguides WG of the PIC photonic chip. The modes of the second family may be those that best decompose the external radiation, for example, Gaussian modes spatially associated with the optical fibers of a fiber bundle coupled to the second optical port, or modes arranged spatially in a matrix to capture and decompose external radiation propagating in free space. Other types of decomposition are possible, for example, from families of Hermite-Gauss modes (having a circular or elliptical support), or generalized Hermite-Gauss, Laguerre-Gauss, Slepian, LP, or OAM modes, or any spatial unitary transformation of these mode families.

[0057] It is recalled that in a multiplane conversion device, the light radiation propagating through it undergoes a succession of reflections and / or transmissions, each reflection and / or transmission being followed by propagation of the radiation in free space. At least some of the optical components on which the reflections and / or transmissions occur, and which guide the propagation of the light radiation in the multiplane conversion device, have micro-structured zones on which the reflections and / or transmissions occur and which modify the shape of this light radiation to implement a chosen unitary transformation of the spatial modes.

[0058] By "microstructured zones" we mean that the surface of the optical component exhibits, on each of these zones, a relief which can, for example, be broken down into "pixels" whose dimensions can range from a few microns to a few hundred microns. These may be metasurfaces. The relief, or each pixel of this relief, has a variable elevation relative to a mean plane defining the surface in question, of at most a few microns or at most a few hundred microns. Regardless of the nature of the microstructuring of the zones, an optical component exhibiting such zones forms a phase mask introducing a local phase shift within the cross-section of the radiation reflected or transmitted there.

[0059] Thus, the light radiation propagating between the first and second optical ports P1,P2, within the MPLC multiplane conversion device undergoes a A succession of local phase shifts separated by propagations. The succession of these elementary transformations (for example, at least four successive transformations such as 8, 9, 10, 12, 13, 14, or even at least 20 transformations) establishes a global transformation of the spatial profile of the radiation (its shape, according to the chosen definition of this term). It is thus possible to configure the micro-structured zones of reflection or transmission to decompose and transform incident radiation of a predetermined shape into emerging light radiation exhibiting another predetermined shape—that is, radiation whose spatial arrangement can be very precisely controlled within an output plane of the multiplane conversion device.

[0060] The theoretical foundations and examples of practical implementation of an MPLC device can be found in the documents “Programmable unitary spatial mode manipulation”, Morizur et al., J. Opt. Soc. Am. A / Vol. 27, No. 11 / November 2010; N. Fontaine et al., (ECOC, 2017), “Design of High Order Mode-Multiplexers using Multiplane Light Conversion”; US9250454 and US2017010463. These documents describe, in particular, the digital design methods that can be used to determine the phase profile of the device's phase masks (i.e., the microstructured areas) according to the established unitary mode transformation. The phase masks can then be produced from the established digital model, for example, by etching or photolithography of the optical component that carries them in order to microstructure it. The microstructuring applied to the optical components configures the chosen architecture to implement the desired transformation.

[0061] A multiplane conversion device can be composed of a plurality of optical components that guide the transmission / reflection sequence. Reference may be made, in particular, to document EP3785064, which illustrates such an embodiment. Alternatively, the device can consist of a single, so-called "monolithic" optical component, within which the light radiation is reflected a plurality of times onto internal surfaces (see document EP3732525). At least some of these internal surfaces may bear the microstructured areas.

[0062] With reference to [Fig. 3], and by way of example, a multiplane MPLC conversion device that can be used in the optical device 1 described herein is shown. In the architecture shown, the MPLC consists of two reflective optical pieces 2a, 2b arranged opposite each other. Microstructured phase masks 3 are carried by one of these pieces. This forms a multipass cavity in which the incident radiation is reflected and phase-shifted a plurality of times at each microstructured mask 3 to transform the incident radiation. Here, the phase masks are all carried by A phase 2a plate with microstructured areas forming the masks, the second optical element 2b being a simple mirror. It is of course possible to have masks applied to each of the optical elements 2a and 2b.

[0063] The shape transformation performed by the MPLC multiplane conversion device of a photonic device 1 of the present description ensures a quality coupling, exhibiting reduced optical losses, between the photonic chip 1 and its external environment.

[0064] For simplicity of presentation, Figures 1 to 3 illustrate a photonic system in which a single external light beam is coupled to a single waveguide WG of the PIC chip. As already stated, it is of course possible to implement more complex couplings. Thus, the chip can be equipped with a plurality of transmit / receive zones, some of these zones being able to operate in transmit mode and others in receive mode. In such a case, the MPLC multiplane converter is configured to associate portions of an external light beam with the transmit / receive zones.

[0065] The MPLC multiplane photonic device may contain parts other than those shown in [Fig. 3]. These may include, for example, optical components such as a mirror, a prism, microlenses, or any other component that guides external light radiation into the MPLC multiplane device or guides light radiation between the first optical port PI and the emission / reception area Z. It may also include a support, or a plurality of supports assembled together, for positioning the reflective optical parts and optical components of the MPLC device relative to each other, or even for assembling the MPLC multiplane conversion device to the PIC photonic chip.

[0066] Similarly, the photonic device 1 may include elements other than the PIC photonic chip and the MPLC multiplane converter. It may thus include a support, for example of the printed circuit board or interposer type, on which the PIC photonic chip rests and which includes traces or vias for electrical connection to which the chip is electrically connected. This support may carry other chips, electronic or photonic, electrically or optically connected to each other. This support may allow the assembly of the MPLC multiplane converter so that the first optical PI port of this device is optically coupled to the transmit / receive area of ​​the chip.The PIC chip can be equipped on its active surface, bearing the transmit / receive area or plurality of transmit / receive areas, with optical adaptation parts such as a prism and / or collimating and / or shaping lenses which constitute or form part of the first optical PI port of the MPLC device. Implementation methods

[0067] In an advantageous configuration, the PIC photonic chip and the MPLC multiplane conversion device are integrated. For example, a main surface of the PIC photonic chip can form one of the reflective optical parts 2a, 2b defining the multipass cavity of the MPLC multiplane conversion device. To this end, this main surface can be coated, by deposition, with a thin layer of a reflective material. It is also possible to microstructure this surface so that it carries the microstructured masks s3 designed to transform the incident radiation.

[0068] By way of illustration, [Fig. 4] represents an optical device 1 for combining a photonic chip PIC and a bundle of optical fibers F, for example single-mode fibers. These fibers collectively propagate light radiation consisting of modes that are spatially separated from each other and whose shape is generally Gaussian.

[0069] The MPLC multiplane conversion device, as shown in [Fig. 4], consists of a first reflective optical piece 2a carrying the semi-structured masks 3. It is positioned opposite a main face of the PIC photonic chip. This main face is provided with a reflective layer which constitutes, in a sense, the second reflective optical piece 2b of the MPLC multiplane conversion device, and which, in combination with the first optical piece 2a, defines the multipass cavity of this device.

[0070] The second optical port of the MPLC device is here formed by a fiber array (FA). It should be noted that in this field, the term "fiber array" refers to the mechanical component located at the end of a bundle of optical fibers to hold them together in a very precise arrangement, for the purpose of coupling these fibers. The ends of the fibers can be arranged along a line or in a plane, and both of these implementation methods are compatible with a photonic device 1 according to the invention.

[0071] Returning to the description of [Fig. 4], the second optical port of the MPLC device consists of the FA optical fiber array, which retains and precisely positions the ends of a bundle of single-mode F optical fibers. The light radiation produced at this second optical port can be decomposed into a family of Gaussian modes, more generally referred to as the "second family of modes," each mode of the family being spatially aligned with the end of a fiber retained in the FA fiber bundle.

[0072] The first optical port of the MPLC device illustrated in [Fig. 4] is here formed by an ML microlens array. The ML microlens array is arranged on the main face of the PIC photonic chip (the active face of this chip) at the locations of the emission / reception zones arranged on this surface. More specifically, each microlens of the ML microlens array is positioned opposite one of these zones, in order to ensure optical coupling between a microlens and a WG waveguide, a cross-section of which can be seen in [Fig.4].

[0073] The light radiation produced at the first optical port PI can be decomposed using a first family of modes, this first family forming a basis for decomposition. This first family can be composed of modes that overlap spatially with the microlenses of the microlens array ML, and thus with an emission / reception area of ​​the photonic chip PIC. Each of these modes can have a shape corresponding to the mode (or a mode) of the internal radiation propagating in a waveguide of the photonic chip.

[0074] As detailed in the aforementioned documents concerning the design of a multiplane MPLC conversion device, the microstructured zones 3 carried by the optical component 2a are configured to perform a modal conversion aimed at respectively matching the modes of the first and second families of modes. The energies present in the modes of one of these families are transported and respectively conformed to the modes of the other family of modes during successive reflections of the radiation on the microstructured masks 3 during its propagation in the cavity of the multiplane MPLC conversion device.

[0075] Of course, the various elements shown in the example illustrated in [Fig. 4] are by no means exhaustive. In particular, other types of modes could be chosen than those shown in the illustration.

[0076] The assembly of the MPLC multiplane conversion device to the PIC photonic chip may involve additional components, such as alignment cubes. These cubes allow for precise control of the position and orientation of the elements to be assembled relative to one another. Examples of possible assemblies are presented in the remainder of this description, with reference to Figures 5 to 7. For the sake of clarity, the components forming the first and second optical ports of the MPLC multiplane device have been omitted from the figures. However, it is understood that the photonic devices shown in these figures may include such components, in accordance with the general description provided in the preceding sections of this description.

[0077] Figure 5 thus represents a first example of an assembly between a multiplane MPLC converter and a PIC photonic chip to form a photonic device 1. This device 1 comprises a support S having a main face on which the PIC photonic chip resides. It may be a printed circuit board support on which other electronic and / or optical components also rest (not re presented), optically / electrically connected to each other to form a functional system.

[0078] An exposed slice of the PIC photonic chip carries the transmit / receive area Z or a plurality of such areas. A waveguide WG of the PIC chip is optically associated with this area Z via an edge coupler integrated into the chip. The MPLC multiplane converter is formed of two facing reflective optical pieces 2a, 2b, one of which carries the microstructured masks 3. As previously stated, these masks could be carried by one or both of these optical pieces 2a, 2b. The two optical pieces 2a, 2b are held assembled together, in the example shown, by means of an assembly piece 2c arranged, for example, as a spacer between the two reflective optical pieces 2a, 2b or forming a support for assembling the slices of the two reflective optical pieces 2a, 2b. In the example reproduced in the [Fig.[5] One of the optical parts 2a,2b is assembled by one of its edges (i.e., a face of this optical part perpendicular to the reflective face defining one side of the multipass cavity) to the main face of the support S (the face on which the PIC photonic chip is also assembled). The MPLC multiplane conversion device is positioned on the support S, relative to the PIC photonic chip, in an arrangement ensuring optical coupling between the PIC photonic chip and the MPLC multiplane conversion device.

[0079] Figure 6a represents a photonic device 1 in which the coupling between the MPLC multiplane converter and the PIC photonic chip is achieved this time via a surface coupling of the PIC photonic chip associated with the waveguide WG. The transmit / receive area Z of the PIC chip is located on the exposed main face of this chip, its other main face resting on the support S. The MPLC multiplane converter, as in the example of Figure 5, is composed of two reflective optical parts 2a, 2b, assembled to each other by means of the assembly part 2c, a spacer or support for these parts 2a, 2b. In this Figure 6a, and to allow optical coupling between the two elements, one of the reflective optical parts 2a, 2b is assembled edge-to-edge with the edge of the support S.

[0080] Fig. 6b represents a variant of the example in Fig. 6a. In this variant, the reflective optical part 2b of Fig. 6a is implemented by a reflective layer formed directly on the support S.

[0081] Figure 6c represents yet another variant of Figure 6a. In this variant, the assembly piece for the two optical parts takes the form of a second support S2. This second support S2 is assembled to the support S on which the PIC photonic chip resides to allow optical coupling of the multiplane conversion device to this PIC chip.

[0082] Figure 7 shows a side view (upper part of the figure) and a top view (lower part of the figure) of a photonic device 1 in which the coupling between the MPLC multiplane converter and the PIC photonic chip implements an optical guide 4 for the light radiation. This optical guide 4 can be formed of at least one mirror, a prism, a periscope, or a combination of these elements. It allows the direction of radiation propagation to be modified to enable its coupling to the PIC chip. This optical guide can form a component of the first PI port of the MPLC multiplane converter.

[0083] The photonic device of the example shown has a support S on which rests the photonic chip 1 and the two reflective optical parts 2a, 2b forming the multiplane conversion device. Radiation propagates in a first direction within the multiplane conversion device, here parallel to the support S. This direction intercepts the optical guide 4. The latter is positioned directly above the emission / reception zone Z of the photonic chip PIC. The optical guide directs the radiation along a second propagation direction more conducive to its coupling to the chip, here perpendicular to the plane of the PIC chip.

[0084] One can naturally consider a device according to the invention employing an optical guide 4 coupling the MPLC multiplane conversion device by edge to the PIC photonic chip.

[0085] Of course the invention is not limited to the modes of implementation described and alternative embodiments can be made without departing from the scope of the invention as defined by the claims.

Claims

Demands

1. Photonic device (1) comprising: - a photonic chip (PIC) extending along a principal plane (P) and having at least one waveguide (WG) disposed in the principal plane (P) and at least one receiving zone (Z) disposed on a surface of the photonic chip (PIC), the waveguide (WG) and the receiving zone (Z) being optically coupled to each other to propagate an internal light radiation consisting of at least one mode, the internal radiation having a first form at the level of the receiving zone (Z);- a multiplane conversion device (MPLC) assembled to the photonic chip (PIC) and comprising a first optical port (PI), optically associated with the receiving area (Z) of the photonic chip (PIC), and a second optical port (P2) for receiving external radiation having a second shape, distinct from the first shape, the external light radiation being capable of propagating from the second optical port (P2) to the first optical port (PI) during a plurality of reflections and / or transmissions on microstructured areas of the multiplane conversion device (MPLC), the microstructured areas being configured to guide at least a part of the external radiation received on the second optical port (P2) and conform this part to the first shape of the internal light radiation at the level of the first optical port (PI).;

2. Photonic device (1) comprising: - a photonic chip (PIC) extending along a principal plane (P) and having at least one waveguide (WG) disposed in the principal plane (P) and at least one emission zone (Z) disposed on a surface of the photonic chip (PIC), the waveguide (WG) and the emission zone (Z) being optically coupled to each other to propagate internal light radiation consisting of at least one mode, the internal radiation having a first form at the level of the zone reception (Z); - a multiplane conversion device (MPLC) assembled to the photonic chip (PIC) and comprising a first optical port (PI), optically associated with the emission zone (Z) to receive the internal light radiation, and a second optical port (P2) to emit an external radiation of a determined shape, distinct from the first shape, the internal light radiation being capable of propagating from the first optical port (PI) to the second optical port (P2) during a plurality of reflections and / or transmissions on microstructured areas of the multiplane conversion device (MPLC), the microstructured areas being configured to guide at least one mode of the internal light radiation received at the level of the first optical port (PI) and conform it to the shape determined at the level of the second optical port (P2).

3. Photonic device (1) according to any one of the preceding claims wherein the multiplane conversion device (MPLC) is composed of a monolithic optical piece in which the external radiation propagates, the monolithic optical piece having at least one face bearing the micro-structured areas.

4. Photonic device (1) according to claim 1 or 2 wherein the multiplane conversion device (MPLC) comprises two optical parts each having a reflective face (2a,2b), the reflective faces of the optical parts (2a,2b) being arranged opposite each other, and at least one of the reflective faces bearing the microstructured areas.

5. Photonic device (1) according to the preceding claim in which one of the reflective optical parts (2a,2b) is formed by a surface of the photonic chip (PIC).

6. Photonic device (1) according to claim 4 in which the multiplane conversion device (MPLC) includes an assembly piece (2c) for assembling the two reflective optical pieces together.

7. Photonic device (1) according to the preceding claim in which the assembly piece (2c) is arranged as a spacer between the two reflective optical pieces (2a,2b) or as a support for the two reflective optical pieces (2a,2b).

8. Photonic device (1) according to any one of the preceding claims wherein the emission or reception area is disposed on a so-called "main" face of the photonic chip (PIC), parallel to the main plane (P).

9. Photonic device (1) according to any one of claims 1 to 7 in which the emission or reception area is disposed on a slice of the photonic chip (PIC), the slice forming a face of the photonic chip perpendicular to the principal plane (P).

10. Photonic device (1) according to any one of the preceding claims wherein the second optical port (P2) comprises an optical fiber array (FA).

11. Photonic device (1) according to any one of the preceding claims wherein the second optical port (P2) comprises at least one multimode fiber.

12. Photonic device (1) according to any one of the preceding claims wherein the first optical port (PI) comprises a microlens array (ML).

13. Photonic device (1) according to any one of the preceding claims wherein the first optical port (PI) comprises an optical guide (4).

14. Photonic device (1) according to the preceding claim in which the optical guide (4) comprises a mirror, a prism or a periscope.

15. Photonic device (1) according to any one of the preceding claims comprising a support (S) on which are disposed the photonic chip (PIC) and the multiplane conversion device (MPLC).

16. Photonic device (1) according to the preceding claim when combined with claim 4, wherein the support (S) comprises a reflective layer forming one of the reflective optical parts (2a,2b) of the multiplane conversion device (MPLC).

17. Photonic device (1) according to any one of the preceding claims wherein the photonic chip comprises at least one photodetector optically associated with the waveguide (WG).