# US 2024/0201441 A1 · Multilevel retro-coupling device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2024/0201441 A1 - Document ID: US20240201441A1 - Status: Published application - Kind: A1 - Application number: 18/541,198 - Filed: 2023-12-15 - Published: 2024-06-20 - Earliest claimed: 2022-12-19 - Assignees: Commissariat A L'energie Atomique Et Aux Energies Alternatives - Applicants: Commissariat A L'energie Atomique Et Aux Energies Alternatives - Inventors: Kyllian MILLARD; Christophe MARTINEZ - Web page: https://patentgrep.com/patent/US20240201441A1 ## CPC - G02B 6/12002: {Three-dimensional structures} - G02B 6/26: Optical coupling means (G02B6/36, G02B6/42 take precedence) - G02B 6/125: Bends, branchings or intersections - G02B 27/0172: {characterised by optical features} - G02B 6/0076: {Stacked arrangements of multiple light guides of the same or different cross-sectional area} - G02B 2006/12104: {Mirror; Reflectors or the like} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A multilevel retro-coupling device for an electromagnetic radiation, including at least one first level (n1) and one second level (n2) at least partially superposed, the first level including a first waveguide intended to guide a propagation of the light radiation in a first direction (s1) and the second level comprising a second waveguide intended to guide the propagation of the light radiation in a second direction (s2) opposite the first direction, the device including: a coupling portion, wherein the first and second waveguides are coupled by moving them closer to one another, such that the electromagnetic radiation is propagated from the first level (n1) to the second level (n2), and at least one reflector at an end of the coupling portion, configured to reflect the electromagnetic radiation. ## Claims ### Claim 1 A multilevel retro-coupling device for a light radiation, comprising at least one first level (n1) extending along a first plane (xy1) and a second level (n2) extending along a second plane (xy2) parallel to the first plane (xy1), said first and second levels being at least partially superposed in a direction (z) normal to the first and second planes (xy1, xy2), the first level comprising at least one first waveguide configured to guide a propagation of the light radiation in a first direction (s1) and the second level comprising at least one second waveguide configured to guide the propagation of the light radiation in a second direction (s2) opposite the first direction, the device comprising: a coupling portion, wherein the first and second waveguides are coupled by moving them closer to one another, such that the light radiation is propagated from the first level (n1) to the second level (n2) by evanescent coupling, and at least one reflector at an end of the coupling portion, configured to reflect the light radiation. ### Claim 2 (depends on 1) The device according to claim 1, wherein the reflector is formed by an interruption of the first and second waveguides in a plane (xz) normal to the first and second propagation directions (S1, S2). ### Claim 3 (depends on 1) The device according to claim 1, wherein the reflector is formed by a block interrupting the first and second waveguides, said block being based on a reflective material, such as aluminium. ### Claim 4 (depends on 1) The device according to claim 1, wherein the coupling portion has a length L=Lc/2 in a propagation direction of the light radiation, Lc being the characteristic coupling length for a transfer of a propagation mode of the light radiation from the first waveguide to the second waveguide. ### Claim 5 (depends on 1) The device according to claim 1, wherein the reflector is formed by a first Bragg mirror coupled to the first waveguide and by a second Bragg mirror coupled to the second waveguide, said first and second Bragg mirrors being superposed in the normal direction (z). ### Claim 6 (depends on 5) The device according to claim 5, wherein the coupling portion has a length L=Lc/2−δ in a propagation direction of the light radiation, Lc being the characteristic coupling length for a transfer of a propagation mode of the light radiation from the first waveguide to the second waveguide, and δ>0 being a penetration length of the mode in the first and second Bragg mirrors. ### Claim 7 (depends on 1) An optical projection system comprising a multilevel retro-coupling device according to claim 1, wherein the second level (n2) corresponds to a projection level (p2), said system further comprising an electrode, called lower electrode, below the projection level (p2). ### Claim 8 (depends on 7) The system according to claim 7, wherein the first level (n1) corresponds to an addressing level (a1) and the lower electrode is located below the addressing level (a1). ### Claim 9 (depends on 7) The system according to claim 7, wherein the first level (n1) corresponds to an addressing level (a1) and the lower electrode is located between the projection level (p2) and the addressing level (a1). ### Claim 10 (depends on 7) The system according to claim 7, wherein the first level (n1) corresponds to an intermediate level (ai) and the lower electrode is located at the same level (n1) as the intermediate level (ai), the system further comprising an addressing level (a0) located below the lower electrode and the intermediate level (ai). ### Claim 11 (depends on 7) The system according to claim 7, wherein the at least one first level (n1) comprises a first addressing level (a10) comprising waveguides configured to guide a propagation of a first light radiation having a first wavelength λ1, a second addressing level (a20) comprising waveguides configured to guide a propagation of a second light radiation having a second wavelength λ2, a third addressing level (a30) comprising waveguides configured to guide a propagation of a third light radiation having a third wavelength λ3, and wherein the projection level (p2) comprises waveguides configured to respectively guide the propagations of the first, second and third light radiations, said first, second and third addressing levels (a10, a20, a30) being located at different depths dp1, dp2, dp3 with respect to the projection level (p2) in the normal direction (z). ### Claim 12 (depends on 11) The system according to claim 11, wherein λ3×λ2>λ1, and dp3>dp2>dp1. ### Claim 13 (depends on 1) The system according to claim 1, wherein the reflector comprises at least one first Bragg mirror configured to reflect the first wavelength λ1, at least one second Bragg mirror configured to reflect the second wavelength λ2, and at least one third Bragg mirror configured to reflect the third wavelength λ3, said first, second and third Bragg mirrors being located at one same depth dp0 with respect to the projection level (p2) in the normal direction (z), and wherein the waveguides of the first, second and third addressing levels (a10, a20, a30) are optically connected to the first, second and third Bragg mirrors by least one guide portion of intermediate depth dpmi (i=1 . . . 3) such that dp3>dpmi≥dp0. ### Claim 14 (depends on 13) The system according to claim 13, wherein the waveguides of the first addressing level (a10) are coupled to the at least one first Bragg mirror without guide portion of intermediate depth and dp1 32 dp0, the waveguides of the second addressing level (a20) are connected to the at least one second Bragg mirror by a guide portion of intermediate depth dpm1=dp0, the waveguides of the third addressing level (a30) are connected to the at least one third Bragg mirror by a guide portion of intermediate depth dpm2=dp2 and by a guide portion of intermediate depth dpm3=dp0.