Adapter for coupling light from a photonic circuit

Abstract

To provide an optical adapter that can overcome all or some of the disadvantages of existing devices for optical coupling between an optical circuit and one or more optical fibers. [Solution] The present invention relates to an optical adapter (100) used as an interface on an optical integrated circuit (101) and configured to generate a spread optical beam (108) and thereby facilitate coupling with an optical fiber (509) and / or an optical connector (505). The optical adapter (100) has a plane mirror on its upper surface and a focusing mirror on its lower surface. The optical beam (108) propagates by spreading between the optical integrated circuit (101) and the focusing mirror within the transparent optical adapter (100), and the path is folded back by the upper plane mirror.

Description

[Technical Field]

[0001] This specification relates to the field of optical integrated circuits, also commonly known as photonic integrated circuits (PICs), and more specifically to the optical coupling between an optical integrated circuit and one or more optical fibers, i.e., optical coupling. [Background technology]

[0002] Optical integrated circuits, particularly photonic circuits on silicon, can combine many functions on a single chip. Such circuits offer advantages over assemblies formed by assembling separate components, especially in terms of reduced bulk and optical loss. In photonic integrated circuits, light is guided through small optical waveguides, typically less than 1 micrometer wide, making it possible to form high-density circuits. Optical integrated circuits communicate with external systems by exchanging light, and this optical coupling is performed while attempting to limit optical loss. The problem of optical coupling is particularly critical in the case of single-mode optical beams, for example, configured to be coupled in single-mode optical fibers, due to the small diameter of the optical beams involved.

[0003] In optical integrated circuits, there are generally two types of optical waveguide coupling interfaces: 1) A vertical grating coupler that operates by the diffraction of light on a periodic structure formed at the end of an optical waveguide, sending light to the top of the chip, and more precisely, sending light at an angle close to perpendicular to the chip, for example, an angle of 8° (an angle considered for a medium having a refractive index equal to that of silica glass), is compatible with single-mode optical fibers commonly used in optical communications, and is capable of forming an optical beam with a diameter of about 10 micrometers. 2) An edge coupler is typically formed by an optical guide positioned at the edge of the circuit and stopping at the edge of the chip, with light emitting along the optical guide. The end portion of the optical guide may further have a structure that broadens the optical modes before exiting the chip. The beam size is typically in the range of 2 to 10 micrometers. In a variation of the edge coupler, a cavity, such as a well, may be formed on the top surface of the circuit to provide access to the output of the optical guide. In this case, light can be sampled by reflecting it in a direction out of the plane of the chip, usually approximately perpendicular, using a mirror positioned in the cavity opposite the end of the optical guide. [Overview of the project] [Problems that the invention aims to solve]

[0004] The two types of interfaces described above make it possible to form a single-mode optical beam with a maximum diameter of approximately 10 micrometers. In this case, direct coupling with optical fibers is possible, but the beam diameter remains small in the sense that the optical fibers must be positioned with a positioning accuracy of less than ±2 μm to obtain an acceptable coupling rate. This positioning accuracy is difficult to achieve and requires the use of dedicated, expensive, and slow machines. To facilitate coupling and widen the positioning tolerance, it is desirable to widen the diameter of the optical beam emanating from the optical integrated circuit to several tens of micrometers, for example, approximately 50 μm. This allows the positioning tolerance to be relaxed to ±10 μm, thereby reducing the difficulty of assembly and enabling the use of cheaper and faster machines.

[0005] Several techniques are available for broadening the beam diameter to couple light between optical integrated circuits and optical fibers. In each case, a sufficiently long optical path is considered to broaden the light beam to the desired size. The various techniques differ depending on the optical mechanism used and the portion of the optical path to which the beam is broadened.

[0006] Furthermore, in the case of edge coupling, the optical fiber must be attached to the edge of the tip, making it mechanically fragile. To avoid this disadvantage and maintain an optical configuration similar to edge coupling, a cavity can be formed from the top surface of the tip to attach the optical fiber to the top surface of the tip. The cavity has a wall perpendicular to the front of the end of the optical guide, so that the beam exiting the optical guide passes through this wall and enters the cavity. Inside the cavity, a folding mirror is positioned to block and deflect the beam upward, so that the beam exits the top surface of the tip in a nearly perpendicular direction. The manufacture of this folding mirror can be carried out using various techniques, but it is an industrial challenge.

[0007] U.S. Patent Nos. 9,817,193, 1,0209,442, 1,0459,163, 1,0690,848, and French Patent No. 3,066615 describe optical integrated circuits that achieve beam expansion across the entire thickness of the chip substrate and have optical functions, lenses, or mirrors on the rear surface of the chip. This solution makes it possible to integrate beam expansion functionality within the chip without adding any additional elements. However, a disadvantage is that in order to pass through the thickness of the chip between the waveguide region and the rear surface of the substrate, light must pass through the interface between silica and silicon, and the large difference in refractive index between these materials means that a significant amount (about 15%) of light is reflected and lost at the interface. For technical reasons, it is difficult and costly to place an anti-reflective layer at this location. Another disadvantage is that the desired optical function (lens or mirror, as applicable) is mounted on the rear surface of the chip. Currently, performing processing on the rear surface requires protecting the front surface and then leaving it unprotected, which increases manufacturing costs. Another disadvantage is that the substrate thickness cannot be selected independently of the desired mode diameter, as the size of the transfer mode is determined by the length of the path within the substrate and its spread is determined by the natural diffraction of the beam.

[0008] French Patent Application No. 3050832, previously filed by the present applicant, describes an optical element that, in the case of edge coupling, enables sampling of a beam from a cavity using a reflector that functions as a folded mirror. However, the optical element described in the above application does not have the function of spreading the light beam.

[0009] French Patent No. 3124001, previously obtained by the present applicant, discloses an optical integrated circuit covered with a transparent chip, in which the beam propagates while spreading. The transparent chip has a plane mirror on its top surface, which allows the beam to be bent toward a collimating mirror manufactured on the optical integrated circuit, thereby generating a spread optical beam. The advantage of this solution is that the positioning tolerance of the transparent chip is relaxed compared to the ±2 μm required for direct coupling to an optical fiber. In the case of edge coupling, French Patent No. 3124001 describes the possibility of manufacturing a folded mirror on the optical integrated circuit opposite the guide output. However, it has been found that manufacturing a folded mirror on an optical integrated circuit, for example at the bottom of a cavity, is difficult, and manufacturers of optical integrated circuits may decide not to include such a mirror in their manufacturing process.

[0010] U.S. Patent Application Publication No. 2023 / 025139, filed by Teramount, describes an optical mechanism comprising a first optical element for focusing light onto an optical fiber and a second optical element for focusing light onto an optical port of an optical integrated circuit. This system enables connection between an optical fiber and an optical integrated circuit while relaxing positioning tolerances. In fact, as described in relation to Figures 4A and 4B of the above application, displacement of the upper block is compensated by a change in the angle of the light rays between the first and second optical elements. For example, a rightward shift of the upper block is compensated by the tilt of the light rays toward horizontal. This optical mechanism requires two focusing optical elements. Furthermore, it is not intended to spread out and parallelize the light beams exiting the device upward.

[0011] It is necessary to overcome all or some of the disadvantages of existing devices for optical coupling between an optical circuit and one or more optical fibers.

Means for Solving the Problem

[0012] For this purpose, an embodiment is an optical adapter, - a transparent region, - a condenser lens disposed on the first surface side of the transparent region and facing the second surface of the transparent region on the opposite side of the first surface, - a first plane mirror disposed on the second surface side of the transparent region and facing the first surface, - a first optical port disposed on the first surface side and configured to face one end of a waveguide of an optical integrated circuit, - a second optical port disposed on the second surface side and is provided with, the optical adapter is configured to guarantee the propagation of an optical beam between the one end of the waveguide and the second optical port, the first plane mirror and the condenser lens are arranged such that an optical beam propagates between the first optical port and the second optical port through the transparent region by reflection at the first plane mirror and the condenser lens, Provided is an optical adapter in which the size of the optical beam at the second optical port is larger than the size of the optical beam at the first optical port.

[0013] According to an embodiment, the optical adapter further includes a second plane mirror disposed in a protruding portion of the transparent region protruding from the first surface, and the protruding portion is configured to be inserted into a cavity of the optical integrated circuit.

[0014] According to an embodiment, the optical adapter does not include optical elements other than the transparent region, the first plane mirror, and the condenser lens.

[0015] According to one embodiment, the transparent region further includes at least one positioning element for mechanically positioning the optical adapter relative to the optical integrated circuit.

[0016] According to one embodiment, the at least one positioning element protrudes from the first surface of the transparent region.

[0017] According to one embodiment, the at least one positioning element has at least one non-optical pad configured to press against the optical integrated circuit.

[0018] According to one embodiment, the at least one positioning element further comprises at least one non-optical finger-like body configured to be inserted into the cavity of the optical integrated circuit.

[0019] According to the embodiment, the first optical port and the second optical port are each adapted to receive and emit a light beam.

[0020] According to the embodiment, the first surface of the transparent region is parallel to the second surface of the transparent region, and the first plane mirror is parallel to the second surface.

[0021] According to one embodiment, the second optical port is configured to be positioned opposite an optical connector to which one end of the optical fiber terminates.

[0022] The embodiment provides an optical device comprising an optical integrated circuit and an optical adapter as described, wherein the optical adapter is mechanically integrated with the optical integrated circuit.

[0023] According to one embodiment, the optical adapter is attached to the optical integrated circuit by a layer of optically transparent adhesive.

[0024] According to one embodiment, the optical device further comprises at least one optical connector positioned opposite the second optical port, with the end of the optical fiber being terminated therein. [Brief explanation of the drawing]

[0025] The features and advantages described herein are described in detail in the remainder of this disclosure of specific embodiments given as examples, with reference to the accompanying drawings, and are not intended to limit the invention.

[0026] [Figure 1] This is a simplified and partially shown side cross-sectional view of an optical adapter assembled in an optical integrated circuit according to the embodiment, along with the geometric notation used in this disclosure. [Figure 2] This is a detailed view showing the assembly of Figure 1 at the level of the beam sampling area within the cavity. [Figure 3] This is a simplified and partially shown side cross-sectional view of a modified optical adapter of Figure 1, which is equipped with a support. [Figure 4] This is a simplified and partially shown side cross-sectional view of another modified example of the optical adapter of Figure 1, which includes a curved mirror and a positioning element. [Figure 5] This is a simplified and partially illustrated side cross-sectional view of an optical device according to an embodiment, particularly illustrating the use of an optical microconnector. [Figure 6] This is a simplified and partially cross-sectional view showing modified examples of optical integrated circuits and optical adapters when a beam is coupled to a vertically coupled diffraction grating. [Modes for carrying out the invention]

[0027] The same elements are indicated by the same reference numeral in various drawings. In particular, structural and / or functional elements common to various embodiments may have the same reference numeral and may have the same structural, dimensional, and material properties.

[0028] For clarity, only steps and elements useful for understanding the embodiments described are shown and described in detail. In particular, applications for implementing optical integrated circuits and optical devices comprising such circuits are not described in detail, and the embodiments described are suitable for all or most applications for implementing optical integrated circuits and optical devices comprising such circuits, and in some cases are adapted within the scope of the skills of a person skilled in the art who has read this disclosure.

[0029] Unless otherwise specified, when referring to two elements connected to each other, this means a direct connection without any intermediate elements other than conductors; when referring to two elements linked to each other, this means that these two elements may be connected, or may be connected via one or more other elements.

[0030] In the following descriptions, when referring to absolute positions such as "front," "back," "top," "bottom," "left," and "right," or relative positions such as "top," "bottom," "upper side," and "lower side," or terms that specify orientation such as "horizontal" and "vertical," unless otherwise specified, these terms refer to the orientation of the drawing.

[0031] Unless otherwise specified, the expressions “approximately,” “roughly,” “substantially,” and “to the extent” represent plus or minus 10% or 10° of the corresponding value, preferably plus or minus 5% or 5°.

[0032] Unless otherwise specified, the expression "in contact with" means "in mechanical contact with".

[0033] Figure 1 is a simplified side cross-sectional view partially showing an optical adapter 100 assembled with an optical integrated circuit 101, also referred to as an integrated photonic circuit 101 or photonic chip 101 according to this embodiment.

[0034] The optical integrated circuit 101 is, for example, a photonic circuit on silicon, i.e., an optical circuit formed on a silicon substrate 103. In a modified example, the substrate 103 may be formed from a material other than silicon, such as a III-V semiconductor material or silicon carbide.

[0035] The optical integrated circuit 101 is, for example, - Electro-optical modulation function, - For example, a photodetection function using a photodiode, - Wavelength filtering function, - Optical path setting function, and - Electrical conduction function One or more basic functions (not shown in detail in the drawings) selected from these may be implemented.

[0036] In the illustrated example, one or more basic functions are implemented by one or more basic elements 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., formed of a single transparent material, or it may not be homogeneous, i.e., formed of several different transparent materials, and may optionally include cavities or air pockets. The concept of transparency is considered at the operating wavelength λ0 of the optical integrated circuit 101. The one or more materials of the transparent region 105 are selected from, for example, silica glass, silicon nitride, or a polymer that is transparent at the operating wavelength λ0.

[0037] The basic optical components are connected together by one or more optical guides, which typically have a central region, i.e., an optical core, and a peripheral region, i.e., an optical sheath, surrounding the central region, i.e., an optical core, where the refractive index of the peripheral region is lower than that of the central region. For example, the central region is formed of silicon or silicon nitride, and the peripheral region is formed of silica glass. As a variation, other types of optical circuits 101 can be conceived, for example, a circuit having an optical guide formed of a III-V semiconductor material can be conceived.

[0038] The optical link between the optical integrated circuit 101 and the outside of the optical integrated circuit is realized by at least one vertical optical coupler and / or at least one optical edge coupler having a diffraction grating.

[0039] Figure 1 shows the case of edge coupling in more detail. For example, the mode diameter can be advantageously broadened by transmitting light through a thin silicon nitride guide, in which case the mode diameter d1 is, for example, approximately 9.0 μm. In the case of a single-mode beam, the "mode diameter" is defined as the light intensity being 1 / e 2 This refers to the diameter decreasing by a coefficient of , where "e" represents the exponent relative to the center of the beam. The beam has, for example, a Gaussian shape.

[0040] The transparent region 105 has a thickness selected, for example, to encompass the entire optical mode of the coupler. For example, the beam axis is at a depth h1 approximately 7.0 μm below the top surface of the optical integrated circuit. For example, a cavity 107 is formed opposite the edge coupler to allow access to the beam and sampling of the beam. The cavity 107 has a depth h'1 approximately 7.0 μm below the beam axis. The center point of the beam at the end of the edge coupler is indicated by P1, from which the light begins to diffuse.

[0041] The optical adapter 100 is assembled on the optical circuit 101 and is capable of generating an upwardly spreading, parallel optical beam 108 in the orientation shown in Figure 1. In Figure 1, the beam 108 has an optical axis represented by a solid line and envelopes represented by two dotted lines on either side of the optical axis of the beam 108. In the illustrated example, the optical adapter includes a pick-off mirror 109 configured to be inserted into the cavity 107 to sample the beam exiting the coupler through the edge and orient it in a nearly vertical direction. In this example, the pick-off mirror 109 is a plane mirror. In Figure 1, the intersection point of the surface of the pick-off mirror 109 and the optical axis of the beam 108 from the coupler is shown as M1, and the orientation of the mirror 109 is considered such that the optical axis P1M1, which is initially horizontal, is oriented at an angle θ of approximately 16.0° with respect to the vertical after reflection by the mirror 109. To obtain the angle θ, the pick-off mirror 109 is tilted at an angle θ1 of 45°-θ / 2, which in this example is approximately 37.0°.

[0042] For example, the adapter 100 is mechanically and optically assembled on the circuit 101 using a transparent optical adhesive. To limit parasitic reflections at the interface between materials, the adhesive preferably has a refractive index close to that of the transparent region 105.

[0043] Furthermore, it is advantageous that the adapter 100 is formed of a transparent material, such as silica glass, having a refractive index close to that of the material of the transparent region 105. For simplicity, in the following description, the refractive index of the light beam 108 is assumed to be equal to that of silica glass. However, in practice, materials with various refractive indices may be used, taking into account the refraction angle and refractive loss due to parasitic reflections at the interface. For this purpose, optical simulation software tools, such as the software known by the trademark name "Zemax," may be used.

[0044] According to one embodiment, the optical adapter 100 includes a transparent region 111, a condensing mirror 113, for example a concave mirror, positioned on the first surface 111B (the lower surface of the transparent region 111 in the orientation of Figure 1) of the transparent region 111, and a plane mirror 115 positioned on the second surface 111T (the upper surface of the transparent region 111 in the orientation of Figure 1) of the transparent region 111, opposite the surface 111B. The plane mirror 115 and the condensing mirror 113 are positioned so that the beam 108 is reflected by the plane mirror 115 toward the surface 111B, and then reflected by the condensing mirror 113 toward the surface 111T, and the beam is parallel to the plane mirror 113. M2 indicates the point where the optical axis of the beam 108 intersects with the plane mirror 115 on the surface 111T, and M3 indicates the point where the optical axis intersects with the surface of the condensing mirror 113. Between the output of the edge coupler and the focusing mirror 113, the beam spreads along its path, and its total length L becomes P1M1 + M1M2 + M2M3.

[0045] The focusing mirror 113 can reflect and parallelize the beam 108. Furthermore, if the focusing mirror 113 is manufactured such that its surface forms an angle θ3 with respect to the horizontal at point M3, it is possible to further change the tilt of the optical axis. For this reason, the focusing mirror is said to be tilted at an angle θ3. In the illustrated example, it is desirable to obtain a beam perpendicular to the surface 111T. For this purpose, an inclination angle of θ3 = θ / 2 = 8.0° is selected.

[0046] After being reflected by the focusing mirror 113, the parallel light beam passes over the top surface of the adapter 100 and exits the adapter 100. P2 indicates the point where the optical axis of the beam from the focusing mirror intersects with the surface 111T of the adapter 100.

[0047] In the external optical medium positioned above the adapter 100, P3 indicates the center position of the waist of the Gaussian beam 108, and d3 indicates the diameter measured perpendicular to the optical axis. In the illustrated example, the optical medium above the adapter 100 is air. If the incident beam M3P2 is not perpendicular to the surface 111T, the refracted beam traveling along the optical axis P2P3 will exhibit a change of direction as it crosses this surface. In the illustrated example, the tilt of the focusing mirror 113 is selected to orient the beam perpendicular to the upper surface 111T of the adapter 100, so the optical axis remains perpendicular to this surface in the output medium above the adapter 100. Furthermore, referring to the concepts of real and virtual images in an optical system, point P3 can be said to be a real image in the output medium when it is above the surface 111T, and a virtual image in the output medium when it is below the surface 111T. In the example of the embodiment shown in Figure 1, point P3 is a real image.

[0048] In the illustrated example, the adapter 100 has a first optical port 117 or optical port 117 located on the surface 111B side and a second optical port 119 located on the surface 111T side. The optical port 117, referred to as the lower optical port or optical port, is defined by a surface centered on point P1 through which a beam 108 propagates with a diameter d1. The optical port 119, referred to as the upper optical port or optical port, is defined by a surface centered on point P3 through which a beam 108 propagates with a diameter d3. The adapter 100 ensures the propagation of the light beam 108 between the lower optical port 117 and the upper optical port 119. According to the principle of reversibility of light, the propagation of light can occur from the lower optical port 117 to the upper optical port 119, or from the upper optical port 119 to the lower optical port 117, with the same beam shape. For example, the upper optical port 119 has a diameter d3 that is at least five times larger than the diameter d1, for example, approximately 50 μm. This diameter is compatible with commercially available plug-in optical microconnectors.

[0049] For example, adapter 100 is, a) A plane mirror 115 is manufactured by photolithography, and then a metal layer formed of, for example, aluminum is etched. b) A step of protecting the plane mirror 115 with a silica layer, c) A step of inverting the wafer and bonding it to a temporary transfer substrate or handle, d) A step of thinning and polishing the wafer, and then forming a three-dimensional shape that defines the focusing mirror 113 and the pick-off mirror 109. e) For example, by depositing an aluminum layer on the surface 111B side, the surfaces of the focusing mirror 113 and the pick-off mirror 109 are coated with a metal film, followed by a photolithography process, and then a process of etching this layer, and f) The wafer is inverted onto a soft adhesive support, the temporary transfer substrate is removed, and the wafer is cut into chips on which the optical adapters 100 are formed. It is manufactured on a silica glass wafer by carrying out a series of processes.

[0050] The techniques used to define the three-dimensional shapes of the focusing mirror 113 and the pick-off mirror 109 include, for example, grayscale photolithography using a resist, followed by, for example, transfer etching with silica glass. Alternatively, the technique is lithography using a technique known as "nanoimprint lithography" using a three-dimensional mold. Alternatively, the technique is known as "selective laser etching," which involves direct writing with a laser followed by wet etching.

[0051] The assembly of the adapter 100 onto the optical integrated circuit 101 is performed, for example, using a pick-and-place type chip transfer device and an optically transparent adhesive. For example, an optical adhesive that polymerizes under ultraviolet light is used to mechanically fix the assembly after it has been placed. Subsequently, an adhesive that can withstand a temperature of about 250°C for about 2 minutes is used, so it is preferable that the assembly formed by the optical circuit 101 and the adapter 100 can withstand passing through a solder reflow oven at 250°C. It is preferable that the material forming the adapter 100 is selected to withstand the same stress.

[0052] An example of size adjustment is described below in relation to Figure 1. However, this example is not limiting, and those skilled in the art can perform other size adjustments based on the description in this disclosure.

[0053] The calculations are disclosed for the operating wavelength λ0 = 1.310 μm (the wavelength measured in a vacuum), but can be substituted for any other wavelength. All materials traversed are in a state where the refractive index n of silica glass, i.e., n = 1.447, is present at this wavelength.

[0054] The lower optical port 117 is considered to be centered at a point P1 located at a depth h1 below the upper surface of the optical integrated circuit 101, where h1 is, for example, 7.0 μm. The lower optical port 117 is considered to emit a circular Gaussian single-mode beam with diameter d1 = 9.0 μm. The Rayleigh length of this beam in a medium with refractive index n is z R =nπ(d1 / 2) 2 / λ0 ≈ 70.3 μm. Intensity 1 / e 2 The total beam divergence angle evaluated is △θ≈d1 / z R Approximately 128 mrad is approximately 7.3°.

[0055] The optical axis of light beam 108 is tilted at an angle θ = 16.0° with respect to the vertical direction in the path between M1, M2, and M3.

[0056] Since the pick-off mirror 109 is a plane mirror inclined at an angle θ1 = 45° - θ / 2 = 37.0°, the light beam on the initially horizontal optical axis is reflected at an angle θ with respect to the vertical. The distance x1 = 10 μm between P1 and M1 is selected.

[0057] The adapter 100 is manufactured such that the upper surface 111T of the adapter 100 is at a position h2 = 189.8 μm above the upper surface of the optical integrated circuit 101. The plane mirror 115 that bends the light beam 108 is disposed on the surface 111T.

[0058] Since the condenser lens 113 is manufactured with an inclination angle θ3 = θ / 2 = 8.0 °, the optical axis of the beam 108 becomes perpendicular to the upper surface of the adapter on the path M3P2 after reflection. With respect to the point M3, a position h3 = 8.3 μm above the surface of the optical integrated circuit 101 is selected. In this case, the length of the optical path between P1 and M3 is L = P1M1 + M1M2 + M2M3 = x1 + (2h2 + h1 - h3) / cos(θ) ≒ 403.5 μm. The horizontal distance between M1 and M2 is x2 = (h2 + h1)tan(θ) ≒ 56.4 μm, and the horizontal distance between M2 and M3 is x3 = (h2 - h3)tan(θ) ≒ 52.0 μm.

[0059] A condenser lens 113 with a spherical surface having a focal length f = 394.0 μm corresponding to a radius of curvature R = 2f ≒ 788.0 μm is selected. δs represents the distance along the optical axis between the light source point P1 and the focus of the condenser lens, and δs = L - f = 9.5 μm. The image of the lower optical port 117 formed by the condenser lens 113 in the medium above the adapter 100 has a waist represented by the formula d3 = d1f(z R 2 +δs 2 ) -1 / 2 ≒ 50.0 μm. The diameter of this 50 μm beam is compatible with the optical plug-in micro-connectors available from connector manufacturers. The intensity 1 / e 2Evaluated as follows, the total divergence angle of the beam exiting into the air is △θ3 = 4λ0 / (πd3) ≈ 33 mrad ≈ 1.9 °. In this way, a wider beam is obtained in which the diameter increases from 9 to 50 μm and the divergence angle decreases from 7.3 to 1.9 °.

[0060] To obtain higher accuracy, the fact that the light beam strikes the focusing mirror 113 at an oblique angle of incidence θ / 2 with respect to the axis of the focusing mirror 113 can be taken into consideration. Therefore, as a variation, an ellipsoid can be selected in which the radius at the incident plane (the plane in Figure 1) is R1 = 2 f / cos(θ / 2) and the radius at the sagittal plane (perpendicular to the incident plane containing the optical axis) is R2 = 2fcos(θ / 2). Generally, those skilled in the art can determine the ideal surface using optical design software.

[0061] In the described state, the waist of beam 108 observed in silica after the focusing mirror 113 is s' = 1 / (1 / f - 1 / (L + z) on the optical axis from the center M3 of the focusing mirror 113. R 2 It is positioned at a distance represented by / δs)) ≈ 689 μm. The beam waist height h5 observed in the air above the top surface of the adapter can be estimated to be h5 = (s'-h2+h3) / n+h2 ≈ 540 μm. This value is the height of the upper optical port 119 centered at point P3 above the top surface 111T of the adapter 100. In this case, when the optical microconnector is assembled, it is positioned so that the optical input of the optical microconnector coincides with the upper optical port 119 of the adapter 100.

[0062] Furthermore, the majority of the geometric shape is configured so that the adapter 100 can be assembled to the optical integrated circuit 101 without any collisions between surfaces. In the pick-off mirror 109, W1 and H1 represent the width and height of the portion of the pick-off mirror 109 to the left of point M1, respectively. H1 = 5.0 μm is chosen to ensure a margin of h'1 - H1 = 2.0 μm between the bottom of the pick-off mirror 109 and the optical integrated circuit 101. W1 = H1 / tan(θ1) ≈ 6.6 μm can be estimated. In the portion of the pick-off mirror 109 to the right of point M1, there are no geometric constraints if the cavity 107 is sufficiently wide, i.e., if the cavity 107 is wider than x1 + h1 / tan(θ1) ≈ 16.6 μm. In this case, the pick-off mirror 109 can be wider to the right of M1 than to the left. For example, a cavity 107 wider than 20 μm is selected.

[0063] In the focusing mirror 113, W3 and H3 represent the width and height of the portion of the focusing mirror 113 located to the left of point M3, respectively. The diameter of the light beam 108 hitting the focusing mirror 113 is d 33 =d1(1+(L / z R ) 2 ) 1 / 2 This is approximately 52.5 μm. To reflect most of the incident beam, we select W3 = 1.5 d3 / 2 = 37.5 μm. H3 = W3 tan(θ3) ≈ 5.3 μm can be estimated. Therefore, the margin between the bottom of the focusing mirror 113 and the surface 111B of the adapter 100 is h3 - H3 ≈ 3.0 μm, preventing collision with surface 111B. The portion of the focusing mirror 113 to the right of point M3 is higher and there is no risk of collision with the optical integrated circuit 101. By selecting the distance h4 = 15.0 μm between the bottom surface 111B of the adapter 100 and the top surface of the optical integrated circuit 101, the width of the focusing mirror 113 to the right of point M3 can be (h4 - h3) / tan(θ3) ≈ 47.7 μm. Therefore, the focusing mirror 113 can be wider to the right of point M3 than to the left.

[0064] Because the pick-off mirror 109 is cut off at the bottom, some of the light is lost without being reflected. This cut-off is at a distance x from the light source point P1.11 The procedure is performed at a position of approximately 3.4 μm = x1 - W1, and the diameter of the light beam 108 at this position is d 11 =d1(1+(x 11 / z R ) 2 ) 1 / 2 ≈ 9.0 μm. Therefore, by cutting off at a distance H1 below point M1, lc1 = 1 / 2 (1 + erf(-√2 (2 H1) / d 11 A light loss of approximately 1.3% occurs, where "erf" is the Gaussian error function.

[0065] Similarly, the light beam 108 hitting the focusing mirror 113 is cut off to the left of point M3 at a distance W3, and lc3 ≈ 1 / 2 (1 + erf(-√2 (2 W3 / d 33 This results in a light loss of approximately 0.2% (in this calculation, the effect of the tilt angle θ3 of the focusing mirror 113 is negligible). The portion of the focusing mirror 113 located to the right of point M3 is larger than the portion located to the left, so the light loss on the right side of the focusing mirror 113 is smaller and negligible in this case.

[0066] The bending of the optical beam 108 is caused by reflection from the plane mirror 115 located on the upper surface 111T of the adapter 100. The optical axis intersects the plane mirror 115 at point M2, and the propagation distance between P1 and M2 is L2 = x1 + (h2 + h1) / cos(θ) ≈ 215 μm. Therefore, the diameter of beam 108 is d2 = d1(1 + (L2 / z R ) 2 ) 1 / 2 This is approximately 28.9 μm. The horizontal length of the beam is d 22=d2 / cos(θ) ≈ 30.1 μm. The plane mirror 115 can be extended to the left of point M2 without direct restriction. However, the plane mirror 115 cannot be extended indefinitely to the right of point M2 because it would block a portion of the beam that exits the adapter 100 after being reflected by the focusing mirror 113. Therefore, a width of W2 = 20.5 μm is selected for the edge of the plane mirror 115 to the right of point M2. In this state, a portion of the light is not reflected by the plane mirror 115, and lc2 = 1 / 2(1 + erf(-√2 (2 W2) / d 22 A loss of approximately 0.3% occurs. Simultaneously, a portion of the light emanating from the upper surface 111T is blocked by the plane mirror 115, resulting in a loss of approximately 0.6% lc4 ≈ 1 / 2(1 + erf(-√2 (2 (x3-W2) / d3))) (the diameter of beam 108 at the upper surface 111T is approximated by d3 to avoid complicating the notation).

[0067] In total, the geometric loss mentioned above is lc1 + lc2 + lc3 + lc4 ≈ 2.4%, which is very low for most applications. In addition to this loss, there is a loss due to reflection from the metal surface of the mirror, with reflection from the aluminum surface resulting in a loss of about 3.1%. The cumulative loss after three reflections is l m It is approximately 9.3%. These losses can be reduced by using metals that reflect light well, such as gold or silver.

[0068] Furthermore, the total footprint in the x-direction for forming the entire optical system is x1 + x2 + x3 + d3 / 2 ≈ 144 μm, making it compact.

[0069] The sensitivity of the optical system to changes in the geometric structure of adapter 100 and changes in the position of adapter 100 on the optical integrated circuit 101 is described below in relation to Figure 1. Adapter 100 propagating light between the optical integrated circuit 101 and an optical microconnector (not shown in Figure 1) is considered, and an acceptable range that allows more than 90% transmission is determined individually for each error.

[0070] When the adapter 100 is shifted relative to the optical integrated circuit 101, the lower optical port 117 connected to the adapter 100 is shifted relative to the optical port present in the optical integrated circuit 101. Depending on the shift in the three spatial directions x, y, and z, the optical transfer coefficient is T ≈ (1 + δx 2 / (2 z R ) 2 ) exp(-4 (δy 2 +δz 2 ) / d1 2 ) becomes. In this equation, δx is z R It is assumed to be much smaller, which is a condition that is actually easy to achieve. The positioning tolerance can be estimated to be δy(90%)=δz(90%)=1.5 μm and δx(90%)=47 μm. Positioning may be observed to be more critical in the y and z directions. In the y direction, correct alignment may be assisted by positioning elements such as finger-like bodies or tabs configured to fit into complementary cavities extending from the top surface of the optical integrated circuit 101 across the thickness of the optical integrated circuit 101. In the z direction, correct positioning may be ensured by supports whose height is selected so 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.

[0071] Due to an error of angle θ1, the lower optical port is mainly tilted at an angle of 2δθ1 relative to the vertical, so the optical transfer coefficient is T ≈ exp(-4 (2δθ1 / △θ)). 2 ) Therefore, δθ1(90%) can be estimated to be 10.3mrad = 0.59°.

[0072] By considering the displacement δz = 2Lδθ3 of the lower optical port 117 relative to the optical integrated circuit, the error in angle θ3 can be taken into account. T ≈ exp(-4 (2Lδθ3 / d1)) 2 ) and δθ3(90%) = 1.8 mrad = 0.10° can be estimated. Such precision in the manufacture of the deflection mirror 109 can be achieved, for example, by grayscale photolithography, nanoimprint lithography, or selective laser etching.

[0073] Due to the adapter's thickness h2 error, the lower optical port 117 is shifted relative to the optical integrated circuit 101 by δz = 2Lδh2sin(θ). T ≈ exp(-4(2δh2sin(θ) / d1)) 2 ) and δh2(90%) = 2.6 μm can be estimated. In practice, it is possible to thin and polish silica glass wafers while controlling the thickness with a higher precision than this tolerance range.

[0074] An optical integrated circuit 101 comprising the adapter 100 according to the present invention may be used with an optical fiber connector configured to receive a spread optical beam. The optical fiber connector may be, for example, a connector having microlenses at the end of the optical fiber (available from Senko), or a ferrule (available from USConec) that deflects light from the optical fiber using a curved folded mirror, serving as both an angle deflector and a beam collimator. Depending on the geometric structure of the optical connector in question, the orientation of the optical connector relative to the adapter 100 and the optical integrated circuit 101 is adjusted so that the optical axes are aligned.

[0075] The present invention enables the use of any type of optical connector. It is sufficient to set the thickness of the adapter 100 and the size of the focusing mirror 113 of the adapter 100 to have a diameter equal to the nominal mode diameter of the optical connector in question and to produce a broadened beam at the required height for this optical connector.

[0076] In summary, the adapter 100 has low optical loss and can be associated with a variety of commercially available connectors without being limited to a specific connector at the design stage, except for the diameter and position of the beam waist assumed for the connector. Furthermore, by using the optical adapter 100, the optical functions related to beam spreading are concentrated solely in the adapter 100, which simplifies the design and manufacture of the optical integrated circuit 101.

[0077] Figure 2 is a detailed view showing the assembly of the optical adapter 100 and the optical integrated circuit 101 from Figure 1.

[0078] 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 is used as an etching stop layer. However, this example is not limiting, and the etching may, in a variation, be stopped 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 has a protruding portion 111S that protrudes from the lower surface 111B of the transparent region 111, and the protruding portion 111S is configured to be inserted into the cavity 107. The mirror 109 is positioned 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 has a central region 201C, i.e., a core, surrounded by a peripheral region, i.e., a sheath, formed by the transparent region 105. The central region 201C has a refractive index greater than that of the peripheral region 105. Furthermore, in this example, another waveguide 203 is positioned above waveguide 201 in a line perpendicular to the end of waveguide 201, enabling light to be transmitted from waveguide 201 to the output port 205 of the optical integrated circuit 101, which is positioned opposite the planar pick-off mirror 109 of the optical adapter 100. Similar to waveguide 201, waveguide 203 has a central region 203C, i.e., a core, surrounded by a peripheral region, i.e., a sheath, formed by the transparent region 105. Waveguide 203 differs from waveguide 201 in that it propagates, for example, modes of a larger diameter. In a modified example, waveguide 203 may not be provided.

[0079] In the illustrated example, for example, a transparent region 207 obtained by polymerization of an adhesive layer placed between the optical integrated circuit 101 and the adapter 100 fills the free space extending between the upper surface of the optical integrated circuit 101 and the lower surface 100B of the adapter 100.

[0080] Figure 3 is a simplified and partially shown side cross-sectional view of a modified example of the optical adapter 100 shown in Figure 1.

[0081] In the illustrated example, the transparent region 111 further includes a mechanical positioning element 301, such as a non-optical pad, configured to protrude from the lower surface 111B of the transparent region 111 and press against the upper surface of the circuit 101. This makes it possible to adjust the distance separating the adapter 100 from the circuit 101 along the vertical axis "z".

[0082] Furthermore, in this example, the transparent region 111 has a lower portion 303 facing the upper surface of the circuit 101 and an upper portion 305 facing outward opposite the lower portion 303. For example, the upper portion 305 is a silica glass plate, and the lower portion 303 is a polymer formed by grayscale photolithography or "nanoimprint lithography" technology. In a variation, the lower portion 303 and the upper portion 305 are formed from the same transparent material, such as silica glass, and the surface is formed by, for example, "selective laser etching" technology.

[0083] In the illustrated example, the optical integrated circuit 101 has an optical output port 205 located on the end side of the waveguide 203 facing the cavity 107.

[0084] Figure 4 is a simplified and partially cross-sectional view showing another modified example of the optical adapter 100 of Figure 1.

[0085] In this modification, the transparent region 111 has a non-optical protruding portion 401 configured to protrude from the lower surface 111B of the adapter 100 and be inserted into the cavity 403 of the optical integrated circuit 101. The protruding portion 401 has, for example, a tooth-like, finger-like, or tab-like shape and functions as a mechanical positioning element for the optical adapter 100 relative to the optical integrated circuit 101. The protruding portion 401 makes it possible to easily and / or improve the alignment of the adapter 100 relative to the circuit 101, particularly along the horizontal axis "x" or in the horizontal plane "xy".

[0086] In the illustrated example, the non-optical protruding portion 401 is formed in the lower portion 303 of the transparent region 111.

[0087] Although only one protrusion 401 is shown in Figure 4, this example is not limiting, and the adapter 100 may, not to mention as a variation, have further non-optical protrusions 401 configured to be inserted into a cavity pre-formed on the upper surface of the circuit 101.

[0088] Figure 5 is a simplified and partially shown side cross-sectional view of the optical device 500 according to the embodiment.

[0089] In the illustrated example, the optical device 500 comprises the assembly described above in relation to Figure 4, which has an optical integrated circuit 101 and an optical adapter 100. The optical device 500 further comprises a support 501, or a socket, or a base, which is integrated with the top surface of the optical integrated circuit 101 and surrounds the optical adapter 100. The support 501 is particularly capable of mechanically positioning a microconnector at an appropriate location on the optical adapter 100. In this example, the support 501 has an opening 503 positioned opposite the upper optical port 119 of the optical adapter 100. The opening 503 allows the optical beam 108 propagated by the adapter 100 to pass through.

[0090] In the illustrated example, the optical device 500 further comprises an optical connector 505, such as a micro-optical connector, which is inserted into an opening 503 of the support 501. In the illustrated example, the optical connector 505 has a focusing mirror 507, such as a concave mirror, which can reflect light from the optical adapter 100 toward the optical fiber 509, and one end of the optical fiber is terminated at the optical connector 505. In this example, the optical conjugate point of the optical port 119 via the focusing mirror 507 is provided at the aforementioned end of the optical fiber 509.

[0091] The advantage of the optical device 500 is that by using the light beam 108 spread at the level of the optical port 119, the positioning tolerance of the optical connector 505 can be increased, thus allowing the use of an optical connector that can be plugged into a socket 501 located on the optical integrated circuit 101. This spread light beam can be obtained by assembling the optical adapter 100 onto the optical integrated circuit 101.

[0092] Figure 6 is a simplified and partially shown side cross-sectional view of a modified optical integrated circuit 101.

[0093] In the illustrated example, 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 waveguide 201, formed, for example, by partially etching a periodic structure into the waveguide core 201C. This diffraction grating forms an optical port 205 for receiving or emitting the light beam 108.

[0094] In this case, the optical integrated circuit 101 does not have a cavity 107, and the optical adapter 100 does not have a protruding portion 111S of the transparent region 111 that protrudes from the surface 111B and the planar folded mirror 109. For example, the optical adapter 100 has no optical functions other than those implemented by the planar mirror 115, the focusing mirror 113, and the transparent region 111.

[0095] Various embodiments and modifications are described. Those skilled in the art will understand that certain features of these various embodiments and modifications may be combined, and other modifications will be conceivable to those skilled in the art. In particular, adapting the optical device 500 to the case of coupling with a diffraction grating, as described above in relation to Figure 6, is within the scope of the skills of those skilled in the art based on the description in this disclosure.

[0096] Finally, the actual implementation of the embodiments and modifications described is within the scope of the skill of those skilled in the art based on the functional descriptions above. In particular, the embodiments described are not limited to the specific examples of materials and dimensions described in this disclosure.

Claims

1. It is an optical adapter, - Transparent area and, - A focusing mirror positioned on the first surface side of the transparent region and facing the second surface of the transparent region on the opposite side of the first surface, - A first plane mirror positioned on the second surface side of the transparent region and facing the first surface, - A first optical port, which is positioned on the first surface side and configured to be positioned opposite one end of the waveguide of the optical integrated circuit, - The second optical port located on the second surface side, - A second plane mirror positioned on the protruding portion of the transparent region that protrudes from the first surface and It is equipped with, The aforementioned protruding portion is configured to be inserted into the cavity of the optical integrated circuit, The optical adapter is configured to ensure the propagation of the light beam between the one end of the waveguide and the second optical port. The first plane mirror and the focusing mirror are arranged such that the light beam propagates through the transparent region between the first optical port and the second optical port by reflection from the first plane mirror and the focusing mirror. An optical adapter in which the size of the light beam at the second optical port is larger than the size of the light beam at the first optical port.

2. The optical adapter according to claim 1, wherein the transparent region further comprises at least one positioning element for mechanically positioning the optical adapter with respect to the optical integrated circuit.

3. The optical adapter according to claim 2, wherein the at least one positioning element protrudes from the first surface of the transparent region.

4. The optical adapter according to claim 2 or 3, wherein the at least one positioning element has at least one non-optical pad configured to press against the optical integrated circuit.

5. The optical adapter according to claim 2 or 3, wherein the at least one positioning element further comprises at least one non-optical finger-shaped body configured to be inserted into the cavity of the optical integrated circuit.

6. The optical adapter according to any one of claims 1 to 3, wherein the first optical port and the second optical port are each adapted to receive and emit a light beam.

7. The optical adapter according to any one of claims 1 to 3, wherein the first surface of the transparent region is parallel to the second surface of the transparent region, and the first plane mirror is parallel to the second surface.

8. The optical adapter according to any one of claims 1 to 3, wherein the second optical port is configured to be positioned opposite an optical connector to which one end of an optical fiber terminates.

9. An optical device comprising an optical integrated circuit and an optical adapter according to any one of claims 1 to 3, wherein the optical adapter is mechanically integrated with the optical integrated circuit.

10. The optical device according to claim 9, wherein the optical adapter is attached to the optical integrated circuit by a layer of optically transparent adhesive.

11. The optical device according to claim 9, further comprising at least one optical connector positioned opposite the second optical port and having an end of an optical fiber terminated at it.

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