Adapter for coupling light from photonic circuit

Abstract

The present description relates to an adapter for coupling light from a photonic circuit, intended to be used as an interface on an optical integrated circuit (101) to produce a widened light beam (108) and thus facilitate coupling with an optical fiber (509) and / or an optical connector (505). An optical adapter (100) includes a plane mirror on an upper surface thereof and a convergent mirror on a lower surface thereof. The light beam (108) propagates by widening between the optical integrated circuit (101) and a convergent mirror inside the transparent optical adapter (100), the path being turned back due to the upper plane mirror.

Description

Technical Field

[0001] This description generally relates to the field of optical integrated circuits, also known as photonic integrated circuits (PICs), and more specifically, to optical coupling or optical coupling between optical integrated circuits and one or more optical fibers. Background Technology

[0002] Optical integrated circuits, particularly photonic circuits on silicon, can combine many functions on a single chip. This is an advantage compared to assemblies formed by assembling discrete components, especially in terms of size reduction and optical loss. In photonic integrated circuits, light is guided in small-sized optical waveguides, typically less than one micrometer wide, which allows for the formation of dense circuits. Optical integrated circuits communicate with external systems by exchanging light, performing this optical coupling while attempting to limit optical loss. In the case of single-mode optical beams intended for coupling, for example, in single-mode optical fibers, the problem of optical coupling is particularly critical due to the small diameter of the beams involved.

[0003] In optical integrated circuits, optical waveguide coupling interfaces typically come in two types:

[0004] 1) Vertical grating couplers, which operate by diffraction of light on a periodic structure formed at the end of an optical waveguide, to send light to the top of a chip, and more precisely, at an angle close to the vertical of the chip, such as 8° (considered in a medium with a refractive index equal to silica glass). Grating couplers can form beams on the order of approximately ten micrometers in diameter, suitable for single-mode optical fibers commonly used in optical communications; and

[0005] 2) Edge couplers, typically located at the edge of the circuit and formed by an optical guide terminating at the chip edge, with light exiting in a straight line along the guide. The end portion of the guide may also have a structure that broadens the optical pattern before it exits the chip. The beam size is typically in the range of two to ten micrometers. Variations of edge coupling may include cavities, such as wells, formed in the upper surface of the circuit, providing a channel to the output of the optical guide. In this case, a mirror located in the cavity opposite the end of the optical guide is able to sample the light by reflection in a direction outside the plane of the chip, typically near the vertical.

[0006] The two types of interfaces described above enable the formation of single-mode beams with a maximum diameter of approximately ten micrometers. Direct coupling with the optical fiber is possible in this case, but the beam diameter remains small, requiring the fiber to be positioned with a positioning accuracy of less than ±2 μm to achieve an acceptable coupling rate. This positioning accuracy is difficult to achieve and requires specialized, expensive, and slow machinery. To facilitate coupling and increase positioning tolerance, it is desirable to increase the diameter of the beam exiting the optical integrated circuit to tens of micrometers, for example, approximately 50 μm. This would allow the positioning tolerance to be reduced to ±10 μm and make the components less sensitive, thus enabling the use of cheaper and faster machinery.

[0007] Several techniques have been developed for coupling light between optical integrated circuits and optical fibers with broadened beam diameters. In all cases, a sufficiently long optical path is considered to allow the beam to be broadened to the desired size. The different techniques vary depending on the optical scheme used and the portion of the optical path (along its beam broadening).

[0008] Furthermore, edge coupling requires attaching the optical fiber to the edge of the chip, which is mechanically fragile. To avoid this drawback and attach the fiber to the upper surface of the chip while maintaining an optical configuration similar to edge coupling, a cavity can be formed from the upper surface of the chip. This cavity has a vertical wall in front of the end of the optical guide, allowing the light beam exiting the optical guide to pass through this wall and penetrate the cavity. Inside the cavity, a deflector is positioned to intercept the beam and deflect it upwards, causing it to exit through the upper surface of the chip in a near-vertical direction. The fabrication of this deflector can be performed using various techniques and is an industrial issue.

[0009] US patents US 9817193, US 10209442, US 10459163, and US 10690848, and French patent FR3066615 describe optical integrated circuits in which beamforming is achieved across the thickness of a chip substrate and where the back side of the chip includes optical functions, lenses, or mirrors. This solution enables the integration of beamforming functionality within the chip without additional components. However, a drawback is that to pass through the chip thickness between the guide region and the back side of the substrate, light must pass through the interface between silicon dioxide and silicon, and the high refractive index contrast between these materials means that a non-negligible portion of the light (approximately 15%) is reflected and lost at the interface. Placing an anti-reflective layer at this location is difficult and expensive for technical reasons. Another disadvantage is that the required optical functions (lenses or mirrors, depending on the case) are performed on the back side of the chip. Processing on the back side now involves higher manufacturing costs because the front side needs to be protected and then left unprotected. Another drawback is that the substrate thickness cannot be chosen independently of the desired mode diameter, because the length of the path in the substrate determines the size of the transmission mode, and its broadening is determined by the natural diffraction of the beam.

[0010] A previous French patent application, FR 3050832, filed by the applicant, describes an optical element that, in the case of edge coupling, enables the sampling of a beam from a cavity by means of a reflector acting as a steering mirror. However, the optical element described in the aforementioned application does not have the function of broadening the beam.

[0011] French patent FR 3124001, previously granted to the applicant, discloses an optical integrated circuit with a transparent chip on top, in which the beam propagates while being broadened. The transparent chip includes a plane mirror on its upper surface, which is capable of folding the beam toward a collimating lens fabricated on the optical integrated circuit to produce a broadened beam. An advantage of this solution is that the positioning tolerance of the transparent chip is not constrained compared to the ±2μm required for direct coupling to an optical fiber. In the case of edge coupling, patent FR 3124001 describes the possibility of fabricating a steering mirror in the optical circuit opposite to the guide output. However, fabricating a steering mirror in the optical circuit, for example at the bottom of a cavity, can become tricky, and the manufacturer of the optical integrated circuit may decide not to include such a mirror in its manufacturing process.

[0012] U.S. Patent Application US 2023 / 025139, filed by Teramount, describes an optical scheme including a first optical element that focuses light onto an optical fiber, and a second optical element that focuses light into an optical port of an optical integrated circuit. This system is capable of performing a connection between the optical fiber and the optical circuitry while benefiting from unconstrained positioning tolerances. In fact, as per the aforementioned application… Figure 4 A and Figure 4 As described in B, the displacement of the upper block is compensated for by a change in the ray angle between the first and second optical elements. For example, a rightward shift of the upper block is compensated for by tilting a near-horizontal ray. This optical scheme requires two focusing optical elements. Furthermore, it is not intended to produce a broadened and collimated beam exiting upwards from the device. Summary of the Invention

[0013] There is a need to overcome all or part of the drawbacks of existing devices that allow optical coupling between optical circuits and one or more optical fibers.

[0014] For this purpose, an embodiment provides an optical adapter, including:

[0015] -Transparent areas;

[0016] - Converging lens, which (13) is located on one side of the first surface of the transparent region and faces the second surface of the transparent region opposite to the first surface;

[0017] - A first plane mirror, which is located on one side of the second surface of the transparent region and faces the first surface;

[0018] - A first optical port, located on one side of the first surface and intended to be positioned relative to one end of the waveguide of the optical integrated circuit; and

[0019] - A second optical port, which is located on one side of the second surface;

[0020] The optical adapter is designed to ensure the propagation of a light beam between one end of the waveguide and the second optical port. The first plane mirror and the converging mirror are arranged such that the light beam propagates between the first optical port and the second optical port through reflections on the first plane mirror and the converging mirror, passing through the transparent region, and the light beam has a larger size at the second optical port than it has at the first optical port.

[0021] According to an embodiment, the adapter also includes a second planar mirror located on a portion of a transparent area protruding from its first surface, the portion being designed to be inserted into a cavity of an optical integrated circuit.

[0022] According to an embodiment, the adapter does not include any optical elements other than the transparent area, the first plane mirror, and the converging mirror.

[0023] According to an embodiment, the transparent area further includes at least one element for mechanically positioning the adapter relative to the optical integrated circuit.

[0024] According to an embodiment, the at least one mechanical positioning element protrudes from the first surface of the transparent region.

[0025] According to an embodiment, the at least one mechanical positioning element includes at least one pad that does not have optical function and is intended to carry on an optical integrated circuit.

[0026] According to an embodiment, the at least one mechanical positioning element further includes at least one finger that has no optical function and is designed to be inserted into a cavity in an optical integrated circuit.

[0027] According to an embodiment, the first optical port and the second optical port are respectively adapted to receive and transmit light beams.

[0028] According to an embodiment, the first surface of the transparent region is parallel to its second surface, and the first plane mirror is parallel to the second surface.

[0029] According to an embodiment, the second optical port is intended to be positioned opposite the optical connector, such that one end of the optical fiber terminates at the optical connector.

[0030] An embodiment provides an optical device comprising an optical integrated circuit as described and an optical adapter, the optical adapter being mechanically integrated with the optical integrated circuit.

[0031] According to an embodiment, the optical adapter is attached to the optical integrated circuit via a layer of optically transparent adhesive.

[0032] According to an embodiment, it also includes at least one optical connector positioned opposite the second optical port and terminating the end of the optical fiber thereto. Attached Figure Description

[0033] The foregoing features and advantages, as well as others, will be described in detail in the remainder of this disclosure, with reference to the accompanying drawings, which are given by way of illustration and not limitation, in which:

[0034] Figure 1 These are simplified and partial side and cross-sectional views of an optical adapter assembled to an optical integrated circuit according to an embodiment, with indications of geometric symbols used in this disclosure;

[0035] Figure 2 yes Figure 1 A detailed view of the components, located at the horizontal level of the beam sampling area within the cavity;

[0036] Figure 3 yes Figure 1 Simplified and partial side and cross-sectional views of a variant of the optical adapter, including the carrier element;

[0037] Figure 4 yes Figure 1 A simplified and partial side and cross-sectional view of another variant of the optical adapter, including curved mirrors and positioning elements;

[0038] Figure 5 These are simplified and partial side and cross-sectional views of the optical device according to an embodiment, particularly illustrating the use of optical micro-connectors; and

[0039] Figure 6 The following are simplified and partial side and cross-sectional views of a variant of an optical integrated circuit and optical adapter in the case of beam coupling to a vertically coupled grating. Detailed Implementation

[0040] The same elements have been designated by the same reference numerals in the various figures. In particular, common structural and / or functional elements in different embodiments may have the same reference numerals and may have the same structure, dimensions, and material properties.

[0041] For clarity, only those steps and elements useful for understanding the described embodiments have been shown and described in detail. In particular, the applications of implementing optical integrated circuits and optics including such circuits have not been detailed, and the described embodiments are compatible with all or most applications of implementing optical integrated circuits and optics including such circuits, which can be adapted to the extent that those skilled in the art are capable of reading this disclosure.

[0042] Unless otherwise stated, when referring to two elements connected to each other, it means that there is no direct connection between them except through a conductor, and when referring to two elements coupled to each other, it means that the two elements can be connected or can be connected via one or more other elements.

[0043] In the following description, reference is made to absolute position qualifiers, such as the terms “front,” “back,” “top,” “bottom,” “left,” “right,” etc., or relative position qualifiers, such as the terms “above,” “below,” “higher,” “lower,” etc., or orientation qualifiers, such as “horizontal,” “vertical,” etc., unless otherwise stated, to the orientation shown in the accompanying drawings.

[0044] Unless otherwise specified, the expressions “approximately,” “about,” “basically,” and “roughly” indicate plus or minus 10% or 10°, preferably plus or minus 5% or 5°.

[0045] Unless otherwise stated, the phrase "in contact with" means "in mechanical contact with".

[0046] Figure 1 The images show simplified and partial side and cross-sectional views of an optical adapter 100 equipped with an optical integrated circuit 101 (also known as an integrated photonic circuit 101 or a photonic chip 101) according to an embodiment.

[0047] The optical integrated circuit 101 is, for example, a photonic circuit on silicon, that is, an optical circuit formed on a silicon substrate 103. As a variant, the substrate 103 may be made of a material other than silicon, for example, a III-V semiconductor material, silicon carbide, etc.

[0048] The optical integrated circuit 101 can implement one or more basic functions (not detailed in the accompanying drawings), such as those selected from the following:

[0049] - Electro-optic dimming function;

[0050] - The function of a photodetector, for example, by means of a photodiode;

[0051] - Wavelength filtering function;

[0052] -Optical routing function; and

[0053] - Electrical conduction function.

[0054] In the illustrated example, one or more basic functions are implemented by one or more basic components formed in a transparent region 105 located on the surface of the optical integrated circuit 101. The transparent region 105 may be homogeneous, i.e., made of a single transparent material, or heterogeneous, i.e., made of multiple different transparent materials, and may include cavities or air pockets. The concept of transparency is considered at the operating wavelength λ0 of the optical integrated circuit 101. One or more materials of the transparent region 105 may be selected, for example, from silica glass, silicon nitride, polymers that are transparent at the operating wavelength λ0, etc.

[0055] Basic optical components are coupled together, for example, by one or more optical guides, which typically include a central region, or optical core, surrounded by a peripheral region, or optical sheath, having a lower refractive index than the central region. As an example, the central region is made of silicon or silicon nitride, and the peripheral region is made of silicon dioxide glass. As variations, other types of optical circuits 101 are conceivable, such as circuits including optical guides made of III-V semiconductor materials.

[0056] The optical link between the optical integrated circuit 101 and the outside of the circuit is achieved by means of at least one vertical optical coupler with a diffraction grating and / or at least one optical edge coupler.

[0057] Figure 1 The case of edge coupling is illustrated more specifically. As an example, the mode diameter can be advantageously widened by diverting light into a thin silicon nitride guide, for which the mode diameter d1 is, for example, approximately 9.0 μm. In the case of a single-mode beam, "mode diameter" refers to the light intensity reduction factor 1 / e relative to the beam center. 2The diameter of the beam is given by the exponent, where "e" represents the exponent. The beam has, for example, a Gaussian shape.

[0058] The transparent region 105 has, for example, a thickness selected to encompass the entire optical mode of the coupler. As an example, the beam axis is located at a depth h1 equal to approximately 7.0 μm below the upper surface of the optical integrated circuit. A cavity 107 is formed, for example, opposite the edge coupler to allow access to and sampling of the beam. The cavity 107 has a depth h'1, for example, approximately 7.0 μm below the beam axis. A marked point P1 is located at the beam center at the end of the edge coupler, from which light begins to diverge.

[0059] The optical adapter 100 is mounted on the optical circuit 101 and enables the generation of an upwardly oriented, broadened, and collimated beam 108. Figure 1 Orientation. In Figure 1 In the diagram, beam 108 includes an optical axis symbolized by a solid line and an envelope symbolized by two dashed lines located on either side of the optical axis of beam 108. In the illustrated example, the adapter includes a pickup mirror 109 designed to be inserted into cavity 107 to sample and guide the beam exiting the coupler through the edge in a near-vertical direction. Mirror 109 is a plane mirror in this example. Figure 1 Note the presence of a point marked M1 where the surface of mirror 109 intersects with the optical axis of beam 108 originating from the coupler, and consider the orientation of mirror 109 such that the initially horizontal optical axis P1M1, after reflection on mirror 109, is oriented at an angle θ relative to the vertical, approximately 16.0°. To obtain angle θ, the tilt angle θ1 of mirror 109 is taken, which is equal to 45° - θ / 2, that is, approximately 37.0° in this example.

[0060] For example, mechanical and optical components of adapter 100 on circuit 101 are obtained by means of transparent optical adhesive. The adhesive preferably has a refractive index close to that of the transparent region 105 in order to limit parasitic reflections at the interface between materials.

[0061] Furthermore, the adapter 100 is advantageously made of a transparent material with a refractive index close to that of the material in the transparent region 105, such as silica glass. In the following description, for simplicity, it is assumed that the refractive index seen by the beam 108 is entirely equal to that of the silica glass. However, in practice, considering the angle of refraction and losses due to parasitic reflections at the interface, materials with different refractive indices can be used. Optical simulation software tools, such as those known under the trade name "Zemax," can be used for this purpose, for example.

[0062] According to an embodiment, the optical adapter 100 includes a transparent region 111, located on one side of a first surface 111B of the transparent region 111 (in... Figure 1 The converging mirror 113 (e.g., a concave mirror) is located on the lower surface of region 111 in the orientation of the region 111, and on one side of the second surface 111T opposite to surface 111B in the transparent region 111 (in the orientation of the region 111). Figure 1 A plane mirror 115 (oriented at the upper surface of region 111) is used. The plane mirror 115 and the converging mirror 113 are arranged such that the beam 108 is reflected by the plane mirror 115 towards surface 111B, and then reflected and collimated by the converging mirror 113 towards surface 111T. M2 specifies the intersection point of the optical axis of the beam 108 with the plane mirror 115 on surface 111T, and M2 also specifies the intersection point of the optical axis with the surface of the converging mirror 113. Between the output of the edge coupler and the converging mirror 113, the beam travels along its path along a path equal to... The total length L becomes wider.

[0063] Converging lens 113 is capable of reflecting and collimating beam 108. If converging lens 113 is manufactured such that its surface forms an angle θ3 relative to the horizontal at point M3, it is also capable of modifying the tilt of the optical axis. This converging lens is then referred to as tilted at angle θ3. In the example shown, it is desirable to obtain a beam vertically oriented to surface 111T. For example, for this purpose, a beam composed of… The given angle of inclination.

[0064] After being reflected by the converging lens 113, the collimated beam exits the adapter 100 through its upper surface. P2 specifies the point where the optical axis of the beam originating from the converging lens intersects the surface 111T of the adapter 100.

[0065] In the external optical medium above adapter 100, P3 specifies the center position of the waist of the Gaussian beam 108, and d3 specifies its diameter as measured perpendicular to the optical axis. In the illustrated example, the optical medium above adapter 100 is air. If the incident beam M3P2 is not perpendicular to surface 111T, then the refracted beam oriented along the optical axis P2P3 exhibits a change in direction as it passes through this surface. In the illustrated example, the tilt of the converging lens 113 is selected to orient the beam perpendicularly to the upper surface 111T of adapter 100, such that the optical axis remains perpendicular to this surface in the output medium above adapter 100. Furthermore, referring to the concepts of real and virtual images in optics, it can be said that if point P3 is above surface 111T, it is a real image in the output medium, and if it is below surface 111T, it is a virtual image in the output medium. Figure 1 In the example of the embodiment shown, point P3 is a real image.

[0066] In the illustrated example, adapter 100 has a first optical port 117 or light port 117 located on one side of surface 111B, and a second optical port 119 located on one side of surface 111T. Optical port 117, referred to as the lower optical port or light port, is defined by a surface centered at point P1 of a beam 108 with a propagation diameter of d1. Optical port 119, referred to as the upper optical port or light port, is defined by a surface centered at point P3 of a beam 108 with a propagation diameter of d3. Adapter 100 ensures that beam 108 propagates between the lower optical port 117 and the upper optical port 119. According to the principle of the reversibility of light, this propagation can occur from the lower port 117 to the upper port 119 or from the upper port 119 to the lower port 117 with the same beam shape. As an example, the diameter d3 of the upper port 119 is at least five times the diameter d1, for example, equal to approximately 50 μm. This diameter is compatible with commercially available plug-in optical micro-connectors.

[0067] As an example, adapter 100 is manufactured on a silicon dioxide glass wafer by performing the following sequential steps:

[0068] a) The plane mirror 115 is fabricated by photolithography, and then a metal layer, for example, made of aluminum, is etched.

[0069] b) Protect plane mirror 115 with a silicon dioxide layer;

[0070] c) Flip the wafer and bond it to a temporary transfer substrate or handle;

[0071] d) Thinning and polishing the wafer, and then forming a three-dimensional shape that defines the converging mirror 113 and the pickup mirror 109;

[0072] e) Metallize the surfaces of mirrors 113 and 109, for example by depositing an aluminum layer on one side of surface 111B, followed by photolithography and then etching the layer; and

[0073] f) Flip the wafer onto a soft adhesive support, remove the temporary transfer substrate, and cut the wafer into chips, each chip forming an optical adapter 100.

[0074] The technique used to define the three-dimensional shape of the converging mirror 113 and the pickup mirror 109 is, for example, grayscale photolithography in a resist followed by transfer etching, for example, in silica glass. Alternatively, the technique is lithography using a technique known as "nanoimprint lithography" with a three-dimensional mold. Alternatively, the technique is direct laser writing followed by wet etching, a technique known as "selective laser etching".

[0075] The assembly of adapter 100 onto optical integrated circuit 101 is performed, for example, by means of a chip transfer device, such as a pick-and-place type, and using an optically transparent adhesive. Optical adhesive polymerized under ultraviolet radiation is used, for example, to mechanically secure the component after its assembly. Preferably, an adhesive capable of subsequently withstanding temperatures on the order of 250°C for approximately 2 minutes is used, so that the assembly formed by optical circuit 101 and adapter 100 can withstand reflow soldering at 250°C. The material forming adapter 100 is preferably selected to withstand the same stress.

[0076] The following will combine Figure 1 Examples of fixed dimensions are described. However, these examples are not limiting, and other dimensions are available to those skilled in the art based on the indications of this disclosure.

[0077] Disclosed for operating wavelength The calculation (of the wavelength measured in a vacuum) can be performed, but it can be converted to any other wavelength. One is to place the cross-materials at that wavelength with the refractive index n of silica glass, i.e. .

[0078] It is assumed that the lower optical port 117 is centered at point P1 located at a depth h1 below the upper surface of the optical integrated circuit 101, for example... It is assumed that the transmit diameter of port 117 is... A circular Gaussian single-mode beam. The Rayleigh length of this beam in a medium with refractive index n is... In 1 / e 2 The total beam divergence evaluated under the intensity is .

[0079] The optical axis of beam 108 is selected at an angle relative to the vertical during its path between M1, M2, and M3. .

[0080] Pickup Mirror 109 is based on angle A tilted plane mirror is used so that the initial horizontal optical axis is reflected at an angle θ relative to the vertical. The distance between P1 and M1 is chosen. .

[0081] The adapter 100 is manufactured such that its upper surface 111T is at a height above the upper surface of the optical integrated circuit 101. The plane mirror 115, which folds the beam 108, is located on the surface 111T.

[0082] Converging mirror 113 at an angle The manufacturing process ensures that the optical axis of beam 108, after reflection, is perpendicular to the upper surface of the adapter on path M3P2. For point M3, the height above the surface of optical integrated circuit 101 is selected. In this case, the optical path length between P1 and M3 is The horizontal distance between M1 and M2 is And the horizontal distance between M2 and M3 is .

[0083] Select focal length The spherical converging mirror 113 corresponds to the radius of curvature. δs specifies the distance along the optical axis between the source point P1 and the focal point of the converging lens. The image of the lower optical port 117 formed by the converging lens 113 in the medium above the adapter 100 has a diameter of The beam waist. This 50μm beam diameter is compatible with optical insertion miniature connectors supplied by connector manufacturers. Given 1 / e 2 The intensity assessment measures the total divergence of the beam emerging from the air. This results in a wider beam, with the diameter increasing from 9 μm to 50 μm, and a lower divergence, decreasing from 7.3° to 1.9°.

[0084] For higher accuracy, the fact that the beam is incident (strikes) onto the converging mirror 113 at an angle of incidence θ / 2 relative to the axis of mirror 113 can be taken into account. Therefore, as a variation, the incident plane ( Figure 1 In-plane radius And within the sagittal plane (perpendicular to the incident plane containing the optical axis) the radius The surface is an ellipsoid. Typically, those skilled in the art can determine the ideal surface using optical design software.

[0085] In the described scenario, the beam waist of the beam 108 seen in the silica behind the converging mirror 113 is located on the optical axis behind the center M3 of the mirror 113, at a distance of... The height h5 of the beam waist as seen in the air above the upper surface of the adapter can be derived as follows: This value is the height of the upper optical port 119 above the upper surface 111T of the adapter 100, centered at point P3. In this case, if an optical micro-connector is fitted, the latter is positioned so that its optical input coincides with the upper optical port 119 of the adapter 100.

[0086] Furthermore, most of the geometry is designed to enable the adapter 100 to be mounted onto the optical integrated circuit 101 without any collisions between surfaces. For the pickup mirror 109, W1 and H1 specify the width and height of the portion of mirror 109 to the left of point M1, respectively. People choose... To allow for a margin between the bottom of the pickup mirror 109 and the optical integrated circuit 101. It can be deduced that... For the portion of mirror 109 to the right of point M1, if cavity 107 is wide enough, i.e., if its width is greater than... If there are no geometric constraints, then the pickup mirror 109 can be wider on the right side of M1 than on the left. For example, a cavity 107 wider than 20 μm can be chosen.

[0087] For converging lens 113, W3 and H3 specify the width and height of the portion of lens 113 to the left of point M3, respectively. The diameter of the beam 108 incident on converging lens 113 is determined by... Given. In order to reflect most of the incident beam, people choose It can be deduced that... The allowance between the bottom of the converging lens 113 and the surface 111B of the adapter 100 is therefore... This prevents collisions with surface 111B. The portion of converging lens 113 to the right of point M3 is higher, and therefore there is no risk of collision with optical integrated circuit 101. The distance between the lower surface 111B of adapter 100 and the upper surface of optical integrated circuit 101 is selected. The width of mirror 113 to the right of point M3 can be Converging lens 113 can therefore be wider on the right side of M3 than on the left side.

[0088] Because the pickup mirror 109 is truncated at the bottom, some light is lost because it is not reflected. The truncation occurs at a distance from the source point P1. At that distance, the diameter of beam 108 is: Therefore, the cutoff at a distance H1 below point M1 results in optical loss, which is caused by... Given, where "erf" is the Gaussian error function.

[0089] Similarly, the beam 108 incident on the converging lens 113 is truncated on the left side at a distance W3 from point M3, resulting in optical loss. (The effect of the tilt angle θ3 of the converging lens 113 is negligible in this calculation). Since the portion of the converging lens 113 to the right of M3 is larger than that to the left, the optical loss on the right side of the converging lens 113 is lower and can be ignored in this case.

[0090] The folding of beam 108 occurs through reflection from plane mirror 115 located on the upper surface 111T of adapter 100. The optical axis intersects plane mirror 115 at point M2, and the propagation distance between P1 and M2 is: The diameter of beam 108 is then determined by... Given. Its length in the horizontal direction is... The plane mirror 115 can extend to the left of M2 without immediate limitation. However, it cannot extend to the right of M2 indefinitely, as it would block a portion of the beam reflected from the adapter 100 by the converging mirror 113. The width of the plane mirror 115 at the right edge of point M2 is then selected. In this situation, some light is not reflected by plane mirror 115, which leads to light loss. At the same time, some of the light emanating from the upper surface 111T is blocked by the plane mirror 115, resulting in light loss. (The diameter of the beam 108 on the upper surface 111T is approximately d3 to avoid symbol overload).

[0091] In summary, the geometric loss mentioned is This is very low for most applications. In addition, there is loss due to the metallic reflection of the mirror; the loss from reflection on an aluminum surface is approximately 3.1%. For triple reflection, the cumulative loss is... Using metals that reflect light better, such as gold or silver, can reduce these losses.

[0092] Furthermore, the total footprint of the entire optical system in the x-direction is: It is compact.

[0093] In the following text Figure 1 The description details the sensitivity of the optical system to changes in the geometry of adapter 100 and its positioning on optical integrated circuit 101. Considerations are made regarding the optical integrated circuit 101 and the optical micro-connector (…). Figure 1 An adapter 100 (not shown) transmits light between the two sources and determines a tolerance that allows more than 90% of the transmission for each individually taken error.

[0094] When adapter 100 is displaced relative to optical integrated circuit 101, the lower optical port 117 connected to adapter 100 is displaced relative to the optical port present in optical integrated circuit 101. Depending on the displacement in the three spatial directions x, y, and z, the light transmittance coefficient is... This expression already assumes that δx is more than z. R Much smaller, which is an easily achievable condition in practice. The positioning tolerance can be derived as follows: It can be observed that positioning in the y and z directions is more critical. In the y direction, proper alignment can be aided by positioning elements (such as fingers or tabs) designed to fit into complementary cavities extending from the upper surface of the optical integrated circuit 101 across the thickness of the optical integrated circuit 101. In the z direction, proper alignment can be ensured by bearings whose height is selected such that the lower optical port 117 of the adapter 100 is at the same height as the optical port of the optical integrated circuit 101.

[0095] The error in angle θ1 mainly causes the lower optical port to tilt relative to the vertical at an angle 2δθ1, resulting in a transmission coefficient of... It can be deduced that... .

[0096] This can be addressed by considering the offset of optical port 117 relative to the optical integrated circuit. Let's consider the error in angle θ3. And it can be deduced Such precision in the manufacture of the deflector 109 can be achieved, for example, through grayscale lithography, nanoimprint lithography, or selective laser etching.

[0097] An error in the thickness h2 of the adapter causes the lower optical port 117 to shift relative to the optical integrated circuit 101. . And it can be deduced In practice, silica glass wafers can be thinned and polished with a thickness control precision better than this tolerance.

[0098] The optical integrated circuit 101 equipped with the adapter 100 according to the invention can be used with fiber optic connectors designed to receive broadened beams. This is, for example, a connector with microlenses at the end of the fiber (available from Senko) or a ferrule that deflects light from the fiber by means of a curved deflector, acting both as an angle deflector and for beam collimation (available from USConec). Depending on the geometry of the optical connector in question, its orientation relative to the adapter 100 and relative to the optical integrated circuit 101 is adjusted to align the optical axes.

[0099] This invention enables the use of any type of optical connector. The dimensions of the thickness of the adapter 100 and its converging lens 113 are sufficient to produce a broadened beam with a diameter equal to the nominal mode diameter of the optical connector under consideration and positioned at the required height of this connector.

[0100] In summary, adapter 100 features low optical loss and can be associated with a variety of commercially available connectors, eliminating the need for binding to a specific connector during design, except for the diameter and position of the beam waist desired through such a connector. Furthermore, the use of optical adapter 100 simplifies the design and manufacture of optical integrated circuit 101, as the optical functions related to beam widening are concentrated solely within adapter 100.

[0101] Figure 2 yes Figure 1 A detailed view of the assembly of the optical connector 100 and the optical integrated circuit 101.

[0102] In the illustrated example, a cavity 107 is formed in the optical integrated circuit 101 by etching the transparent region 105 of the transparent layer 105 down to the substrate 103, which serves as an etch stop layer. However, this example is not limiting, and as a variation, etching may stop before reaching the substrate 103, in which case the cavity 107 has a depth less than the thickness of the transparent region 105. The transparent region 111 of the optical adapter 100 includes a portion 111S protruding from the lower surface 111B of the region 111, the portion 111S being intended to be inserted into the cavity 107. A mirror 109 is located on the protruding portion 111S. This enables edge coupling of the waveguide 201 formed in the transparent region 105 of the circuit 101. In the illustrated example, the waveguide 201 includes a central region 201C or core surrounded by a peripheral region or sheath formed by the transparent region 105. The refractive index of the central region 201C is greater than that of the peripheral region 105. Furthermore, in this example, another waveguide 203 is located on top of waveguide 201 and is vertically aligned with the end of waveguide 201, so that light can be transmitted from waveguide 201 to the output port 205 of optical integrated circuit 101 located opposite the planar pickup mirror 109 of optical adapter 100. Similar to waveguide 201, waveguide 203 includes a central region 203C or core surrounded by a peripheral region or sheath formed by a transparent region 105. Waveguide 203 differs from waveguide 201 in that, for example, it propagates a larger diameter mode. As a variant, waveguide 203 may be omitted.

[0103] In the illustrated example, for instance, a transparent region 207, obtained by polymerization of an adhesive layer between the optical integrated circuit 101 and the adapter 100, fills the free space extending between the upper surface of the circuit 101 and the lower surface 100B of the adapter 100.

[0104] Figure 3 yes Figure 1 Simplified and partial side and cross-sectional views of a variant of the optical adapter 100.

[0105] In the example shown, the transparent region 111 also includes a mechanical positioning element 301, such as a pad without optical function, which protrudes from the lower surface 111B of region 111 and is intended to be supported on the upper surface of circuit 101. This allows the distance between the disconnect adapter 100 and circuit 101 to be adjusted along the vertical axis "z".

[0106] Furthermore, in this example, the transparent region 111 includes a lower portion 303 facing the upper surface of circuit 101 and an upper portion 305 facing outwards opposite to the lower portion 303. For example, portion 305 is a silica glass plate and portion 303 is a polymer formed by grayscale lithography or by nanoimprint lithography. As a variant, portions 303 and 305 are made of the same transparent material, such as silica glass, and the surfaces are formed, for example, by selective laser etching.

[0107] In the example shown, the optical integrated circuit 101 has an optical output port 205 located on the end side of the waveguide 203 opposite to the cavity 107.

[0108] Figure 4 yes Figure 1 A simplified and partial side and cross-sectional view of another variant of the optical adapter 100.

[0109] According to this variant, the transparent region 111 includes a portion 401 without optical function, which protrudes from the lower surface 111B of the adapter 100 and is intended to be inserted into the cavity 403 of the optical integrated circuit 101. The portion 401 has a shape such as teeth, fingers, or tabs and acts as a mechanical positioning element for the optical adapter 100 relative to the optical integrated circuit 101. The portion 401 enables and / or improves the alignment of the adapter 100 relative to the circuit 101, particularly alignment along the horizontal axis "x" or alignment in the horizontal plane "xy".

[0110] In the example shown, a portion 401 without optical function is formed in portion 303 of region 111.

[0111] Despite Figure 4 Only one part 401 is shown in the figure, but this example is not limiting, and as a variation, the adapter 100 may of course include more parts 401 without optical function, which are designed to be inserted into cavities previously formed in the upper surface of the circuit 101.

[0112] Figure 5 These are simplified and partial side and cross-sectional views of the optical device 500 according to the embodiment.

[0113] In the example shown, the optical device 500 includes previously mentioned... Figure 4The described component includes an optical integrated circuit 101 and an optical adapter 100. The optics 500 also includes a support 501, or socket, or base, which is integrated with the upper surface of the optical integrated circuit 101 and surrounds the optical adapter 100. The support 501 particularly functions to allow mechanical placement of a micro-connector in a suitable location above the optical adapter 100. In this example, the support 501 has an opening opposite the upper optical port 119 of the optical adapter 100. The opening 503 allows a light beam 108 propagated by the adapter 100 to pass through.

[0114] In the illustrated example, the optical device 500 also includes an optical connector 505, such as a micro-optical connector, which is inserted into the opening 503 of the support 501. In the illustrated example, the optical connector 505 includes a converging mirror 507, such as a concave mirror, which enables light originating from the optical adapter 100 to be reflected toward the optical fiber 509, one end of which terminates at the optical connector 505. In this example, the optical conjugate of the optical port 119 is located at the end of the optical fiber 509 via the converging mirror 507.

[0115] The advantage of the optics 500 lies in the fact that using a broadened beam 108 at the level of the optical port 119 increases the positioning tolerance for the optical connector 505, enabling the use of an optical connector that can be inserted into a socket 501 positioned on the optical integrated circuit 101. Assembly of the optical adapter 100 to the optical integrated circuit 101 makes it possible to obtain the broadened beam.

[0116] Figure 6 These are simplified and partial side and cross-sectional views of a variant of the optical integrated circuit 101.

[0117] In the example shown, the optical coupling between the waveguide 201 of the optical integrated circuit 101 and the optical adapter 100 is achieved by a diffraction grating located at the end of the guide 201 and formed, for example, by etching a periodic structural portion into the core 201C of the guide. This diffraction grating forms an optical port 205 for receiving or emitting a beam 108.

[0118] In this case, the optical integrated circuit 101 does not include the cavity 107 and the optical adapter 100 does not include the portion 111S protruding from the surface 111B of the transparent region 111 and from the plane steering mirror 109. As an example, the optical adapter 100 does not include optical functions other than those implemented by the plane mirror 115, the converging mirror 113 and the transparent region 111.

[0119] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations can be combined, and other variations will readily conceive of by those skilled in the art. In particular, the optical device 500 pairs as previously described... Figure 6 The described case of coupling via a diffraction grating is adaptable to the capabilities of those skilled in the art based on the instructions of this disclosure.

[0120] Finally, the actual implementation of the described embodiments and variations is within the capabilities of those skilled in the art based on the functional indications given above. In particular, the described embodiments are not limited to the specific examples of materials and dimensions mentioned in this disclosure.

Claims

1. An optical adapter (100), comprising: -Transparent area (111); - Converging lens (113), the converging lens (13) is located on one side of the first surface (111B) of the transparent region (111) and faces the second surface (111T) of the transparent region (111) opposite to the first surface (111B). - First plane mirror (115), the first plane mirror (115) is located on one side of the second surface (111T) of the transparent area (111) and faces the first surface (111B). - A first optical port (117) is located on one side of the first surface (111B) and is intended to be positioned opposite one end of the waveguide (201; 203) of the optical integrated circuit (101); - A second optical port (119), the second optical port (119) being located on one side of the second surface (111T); and - A second plane mirror (109) is located on a portion (111S) of the transparent region (111) that protrudes from its first surface (111B), the portion (111S) being designed to be inserted into the cavity (107) of the optical integrated circuit (101). The optical adapter (100) is designed to ensure the propagation of a light beam (108) between one end of the waveguide (201; 203) and the second optical port (119), wherein the first plane mirror (115) and the converging mirror (113) are arranged such that the light beam (108) propagates between the first optical port (117) and the second optical port (119) through the transparent region (111) by reflection on the first plane mirror (115) and the converging mirror (113), and the light beam (118) has a larger dimension (d3) at the second optical port (119) than it has at the first optical port (117) with a dimension (d1).

2. The adapter (100) according to claim 1, wherein, The transparent area (111) also includes at least one element (301; 401) for mechanically positioning the adapter (100) relative to the optical integrated circuit (101).

3. The adapter (100) according to claim 2, wherein, The at least one mechanical positioning element (301; 401) protrudes from the first surface (111B) of the transparent region (111).

4. The adapter (100) according to claim 2 or 3, wherein, The at least one mechanical positioning element (301; 401) includes at least one pad (301) without optical function, which is intended to be supported against the optical integrated circuit (101).

5. The adapter (100) according to any one of claims 2 to 4, wherein, The at least one mechanical positioning element (301; 401) further includes at least one finger (401) that has no optical function and is designed to be inserted into the cavity (403) of the optical integrated circuit (101).

6. The adapter (100) according to any one of claims 1 to 5, wherein, The first optical port (117) and the second optical port (119) are respectively adapted to receive and transmit the light beam (108).

7. The adapter (100) according to any one of claims 1 to 6, wherein, The first surface (111B) of the transparent region (111) is parallel to its second surface (111T), and the first plane mirror (115) is parallel to the second surface (111T).

8. The adapter (100) according to any one of claims 1 to 7, wherein, The second optical port (119) is intended to be positioned opposite the optical connector (505) such that one end of the optical fiber (509) terminates in the optical connector (505).

9. An optical device (500), comprising: An optical integrated circuit (101) and an optical adapter (100) according to any one of claims 1 to 8, wherein the optical adapter (100) is mechanically integrated with the optical integrated circuit (101).

10. The device (500) according to claim 9, wherein, The optical adapter (100) is attached to the optical integrated circuit (101) by a layer of optical transparent adhesive (207).

11. The device (500) according to claim 9 or 10 further includes at least one optical connector (505) positioned opposite the second optical port (119) and terminating the end of the optical fiber (509) at the optical connector (505).

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