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CN-122018077-A - Adapter for coupling light from a photonic circuit

CN122018077ACN 122018077 ACN122018077 ACN 122018077ACN-122018077-A

Abstract

The present description relates to an adapter for coupling light from a photonic circuit, which is 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). The optical adapter (100) includes a planar mirror on an upper surface thereof and a converging mirror on a lower surface thereof. The light beam (108) propagates by widening between the converging mirror inside the optical integrated circuit (101) and the transparent optical adapter (100), which path is folded back due to the upper plane mirror.

Inventors

  • Olivier Castani

Assignees

  • 原子能与替代能源委员会

Dates

Publication Date
20260512
Application Date
20251112
Priority Date
20241112

Claims (11)

  1. 1. An optical adapter (100), comprising: -a transparent area (111); -a converging mirror (113), the converging mirror (13) being located on one side of a first surface (111B) of the transparent area (111) and facing a second surface (111T) of the transparent area (111) opposite to the first surface (111B); -a first plane mirror (115), the first plane mirror (115) being located on one side of the second surface (111T) of the transparent area (111) and facing the first surface (111B); -a first optical port (117), said first optical port (117) being located on one side of said first surface (111B) and intended to be positioned opposite one end of a waveguide (201; 203) of an optical integrated circuit (101); -a second optical port (119), said second optical port (119) being located on one side of the second surface (111T), and -A second plane mirror (109), said second plane mirror (109) being located on a portion (111S) of said transparent area (111) protruding from a first surface (111B) thereof, said portion (111S) being intended to be inserted into a cavity (107) of said optical integrated circuit (101), The optical adapter (100) is intended to ensure propagation of a light beam (108) between the one end of the waveguide (201; 203) and the second optical port (119), the first plane mirror (115) and the converging mirror (113) being arranged such that the light beam (108) propagates between the first optical port (117) and the second optical port (119) by reflection on the first plane mirror (115) and the converging mirror (113), through the transparent region (111), the light beam (118) having a larger size (d 3 ) at the second optical port (119) than it has at the first optical port (117).
  2. 2. The adapter (100) according to claim 1, wherein the transparent region (111) further comprises at least one element (301; 401) for mechanically positioning the adapter (100) with respect to the optical integrated circuit (101).
  3. 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 area (111).
  4. 4. An adapter (100) according to claim 2 or 3, wherein the at least one mechanical positioning element (301; 401) comprises at least one pad (301) without optical function intended to be carried against the optical integrated circuit (101).
  5. 5. The adapter (100) according to any of claims 2 to 4, wherein the at least one mechanical positioning element (301; 401) further comprises at least one finger (401), the finger (401) being optically non-functional and intended to be inserted into a cavity (403) of the optical integrated circuit (101).
  6. 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 adapted to receive and transmit the light beam (108), respectively.
  7. 7. The adapter (100) according to any one of claims 1 to 6, wherein a first surface (111B) of the transparent region (111) is parallel to a second surface (111T) thereof, the first plane mirror (115) being parallel to the second surface (111T).
  8. 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 an optical connector (505) with one end of an optical fiber (509) terminating in the optical connector (505).
  9. 9. An optical device (500) comprising an optical integrated circuit (101) and an optical adapter (100) according to any of claims 1 to 8, the optical adapter (100) being mechanically integrated with the optical integrated circuit (101).
  10. 10. The device (500) of claim 9, wherein the optical adapter (100) is attached to the optical integrated circuit (101) by a layer of optically transparent adhesive (207).
  11. 11. The device (500) of claim 9 or 10, further comprising at least one optical connector (505) positioned opposite the second optical port (119) and terminating an end of an optical fiber (509) at the optical connector (505).

Description

Adapter for coupling light from a photonic circuit Technical Field The present description relates generally to the field of optical integrated circuits, also known as Photonic Integrated Circuits (PICs), and more particularly to optical coupling or optical coupling between an optical integrated circuit and one or more optical fibers. Background Optical integrated circuits, and in particular photonic circuits on silicon, can combine many functions on a single chip. This is an advantage over assemblies formed by assembling discrete parts, particularly in terms of volume reduction and optical losses. In photonic integrated circuits, light is guided in small-sized optical waveguides, typically less than one micron in width, which enable dense circuits to be formed. The optical integrated circuit communicates by exchanging light with an external system, performing such coupling of light while attempting to limit optical losses. 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. In optical integrated circuits, there are generally two types of optical waveguide coupling interfaces: 1) A vertical grating coupler operating due to diffraction of light on a periodic structure formed at the end of an optical waveguide to transmit light to the top of the chip, and more precisely at an angle close to the vertical of the chip, for example at an angle of 8 DEG (considered in a medium with refractive index equal to silica glass), the grating coupler being able to form a light beam with a diameter on the order of ten microns suitable for a single-mode optical fiber commonly used for optical communication, and 2) An edge coupler, typically located at the edge of the circuit and formed by an optical guide terminating at the edge of the chip, then light exits in line with the guide. The end portion of the guide may also have a structure that widens the optical mode before it exits the chip. The beam size is typically in the range of two to ten microns. The edge-coupled variant may include a cavity, such as a well, formed in the upper surface of the circuit that provides a channel for the output of the optical guide. In this case, the mirror located in the cavity opposite the end of the optical guide is capable of sampling the light by reflection in a direction out of the plane of the chip, typically a near vertical direction. Both types of interfaces enable the formation of a single-mode beam having a maximum diameter of approximately ten microns. In this case, direct coupling to the fiber is possible, but the beam diameter is kept small in the sense that it is necessary to position the fiber with a positioning accuracy of less than plus or minus 2 μm to obtain an acceptable coupling ratio. Such positioning accuracy is difficult to achieve and requires the use of dedicated, expensive, slow machines. To facilitate coupling and increase positioning tolerances, it is desirable to expand the diameter of the beam exiting the optical integrated circuit to tens of microns, for example, about 50 μm, which can release the positioning tolerances to plus or minus 10 μm and thereby make the assembly less sensitive, thus enabling the use of cheaper and faster machines. Various techniques have been provided to couple light between an optical integrated circuit and an optical fiber having a widened beam diameter. In all cases, an optical path long enough to widen the beam to the desired size is considered. The different techniques differ by the optical scheme used and the portion of the optical path along which the beam is widened. Furthermore, the case of edge coupling requires that the optical fiber be attached to the edge of a chip that is mechanically fragile. To avoid this disadvantage and attach the optical fiber to the upper surface of the chip while maintaining an optical configuration similar to edge coupling, a cavity may be formed from the upper surface of the chip, with a vertical wall in front of the end of the optical guide, such that the light beam exiting the optical guide passes through this wall and penetrates the cavity. Inside the cavity, a turning mirror is provided to intercept the beam and deflect it upwards so that it exits through the upper surface of the chip in a near vertical direction. The manufacture of such turning mirrors can be performed using various techniques and is an industrial problem. United states patents US 9817193, US 10209442, US 10459163 and US 10690848 and french patent FR 3066615 describe optical integrated circuits in which beam expansion is achieved across the thickness of the chip substrate and in which the back side of the chip includes optical functions, lenses or mirrors. This solution enables the integration of beam expansion functions inside the chip without additional elements. However, a disadvantage is that to pass through th