Search

US-20260126699-A1 - FIDELITY-RESTORABLE PHOTONIC LINEAR OPERATOR

US20260126699A1US 20260126699 A1US20260126699 A1US 20260126699A1US-20260126699-A1

Abstract

The present disclosure relates to implementations of a photonic circuit, and particularly to a photonic circuit that includes one or more matrix circuits. For example, the present disclosure relates to photonic circuit implementations of unitary matrices, and of arbitrary real and/or complex matrices factorized using unitary matrices, that utilize special generalized Mach-Zehnder interferometers (SGMZIs) as building blocks of various matrix circuit architectures.

Inventors

  • Nikolaos Pleros
  • Apostolos Tsakyridis
  • Georgios Giamougiannis
  • Angelina Totovic

Assignees

  • CELESTIAL AI INC.

Dates

Publication Date
20260507
Application Date
20250811

Claims (20)

  1. 1 .- 20 . (canceled)
  2. 21 . A special generalized Mach-Zehnder interferometer (SGMZI), comprising: a generalized Mach-Zehnder interferometer (GMZI) of n dimensions that couples optical signals between n input ports and n output ports, wherein: the GMZI is implemented by n interferometer paths optically coupled between a first n×n optical coupler and a second n×n optical coupler; and the GMZI includes a group of internal phase shifters in the n interferometer paths; and a group of external phase shifters at the n input ports or the n output ports of the GMZI, wherein the group of external phase shifters includes at least n−1 phase shifters.
  3. 22 . The SGMZI of claim 21 , wherein the group of internal phase shifters includes n or n−1 phase shifters.
  4. 23 . The SGMZI of claim 21 , wherein the group of external phase shifters is operable to set phases of output signals of the GMZI.
  5. 24 . The SGMZI of claim 21 , wherein a total number of phase shifters between the group of internal phase shifters and the group of external phase shifters equals 2n or 2n−1.
  6. 25 . The SGMZI of claim 21 , wherein the group of external phase shifters is operable to: cancel an accumulated phase within the GMZI; and introduce a target phase for elements of a transfer matrix represented by the SGMZI.
  7. 26 . The SGMZI of claim 21 , wherein: the first n×n optical coupler is a first n×n multi-mode interferometer (MMI); and the second n×n optical coupler is a second n×n MMI.
  8. 27 . The SGMZI of claim 21 , wherein: the group of external phase shifters is located at the n output ports of the GMZI; and the group of external phase shifters includes phase shifters at n−1 of the n output ports.
  9. 28 . The SGMZI of claim 21 , wherein the group of internal phase shifters is located in a diagonal matrix region optically coupled between the first n×n optical coupler and the second n×n optical coupler.
  10. 29 . The SGMZI of claim 21 , wherein the group of external phase shifters is operable to set relative phases of output optical signals corresponding to elements of a first column of a transfer matrix represented by the SGMZI.
  11. 30 . The SGMZI of claim 21 , wherein at least one phase shifter of the group of internal phase shifters or the group of external phase shifters includes at least one of an electro-optic phase shifter or a thermal phase shifter.
  12. 31 . A photonic circuit block, comprising: a group of special generalized Mach-Zehnder interferometers (SGMZIs) optically coupled in series, wherein each SGMZI in the group of SGMZIs includes: a generalized Mach-Zehnder interferometer (GMZI) of a respective n dimensions that couples optical signals between respective n input ports and respective n output ports, wherein: the GMZI is implemented by respective n interferometer paths optically coupled between a respective first n×n optical coupler and a respective second n×n optical coupler; and the GMZI includes a group of internal phase shifters in the respective n interferometer paths; and a group of external phase shifters at the respective n input ports or the respective n output ports of the GMZI, wherein the group of external phase shifters includes at least n−1 phase shifters.
  13. 32 . The photonic circuit block of claim 31 , wherein the group of SGMZIs includes: a first SGMZI having a first dimensionality; and a second SGMZI coupled in series to the first SGMZI, the second SGMZI having a second dimensionality that is greater than the first dimensionality.
  14. 33 . The photonic circuit block of claim 32 , further comprising a group of waveguide paths that optically couple the group of SGMZIs in series, wherein the group of waveguide paths includes a waveguide path that guides optical signals through the second SGMZI without guiding the optical signals through the first SGMZI.
  15. 34 . The photonic circuit block of claim 31 , wherein the group of SGMZIs includes SGMZIs having dimensionalities ranging from 1 to N.
  16. 35 . The photonic circuit block of claim 31 , wherein the group of SGMZIs is ordered in size-augmenting fashion.
  17. 36 . The photonic circuit block of claim 31 , wherein each SGMZI in the group of SGMZIs having a dimensionality of two or greater includes a pair of optical couplers, the pair of optical couplers associated with a given SGMZI having a dimensionality equal to a corresponding dimensionality of the given SGMZI.
  18. 37 . The photonic circuit block of claim 31 , wherein, for each SGMZI in the group of SGMZIs the group of external phase shifters is located at the respective n output ports of the GMZI of that SGMZI.
  19. 38 . The photonic circuit block of claim 31 , wherein, for each SGMZI in the group of SGMZIs, the respective first n×n optical coupler and the respective second n×n optical coupler each comprise a respective n×n multi-mode interferometer (MMI).
  20. 39 . The photonic circuit block of claim 31 , wherein the photonic circuit block represents a transfer matrix expressed as a product of respective transfer matrices implemented by the group of SGMZIs.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 17/957,812, filed Sep. 30, 2022, which claims priority to U.S. Provisional Patent Application No. 63/261,974, filed on Oct. 1, 2021, which is incorporated by reference herein in its entirety. BACKGROUND OF THE DISCLOSURE In the emerging field of photonic computing, various approaches have been proposed to implement arbitrary linear operators, represented as matrices of any values, with programmable photonic circuits composed of optical splitters and couplers, controllable phase and/or amplitude modulators, etc. Such implementations are commonly based on Singular Value Decomposition (SVD), which factorizes an arbitrary matrix into a diagonal matrix and two unitary matrices, along with further decomposition of the unitary matrices into products of block matrices. The unitary matrix decomposition translates, in the photonic circuit implementation, to partitioning the circuit into smaller blocks of components. To date, the dominant block matrix utilized in photonics for unitary matrix decomposition has been the 2×2 unitary matrix, U(2), which can be realized as a Mach-Zehnder interferometer augmented by two phase shifters. Theoretically, an arbitrary N×N matrix can be implemented with U(2) nodes followed by N phase shifters in N−1 steps of programming. In practice, however, non-ideal, lossy components often result in a loss in fidelity, that is, a discrepancy between the targeted matrix and its practical implementation. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an example schematic diagram of a Special Generalized Mach-Zhender Interferometer (SGMZI) in accordance with one or more embodiments described herein. FIG. 2 illustrates an example schematic diagram of a unitary matrix circuit in accordance with one or more embodiments described herein. FIG. 3A illustrates an example schematic diagram of an arbitrary matrix circuit in accordance with one or more embodiments described herein. FIG. 3B illustrates a more detailed example schematic diagram of the arbitrary matrix circuit shown in FIG. 3A. FIG. 4 illustrates an example structural implementation of an electro-optical system-in-package. DETAILED DESCRIPTION The present disclosure relates to implementations of a photonic circuit, and particularly to a photonic circuit that includes one or more matrix circuits. More specifically, the present disclosure relates to photonic circuit implementations of unitary matrices, and of arbitrary real and/or complex matrices factorized using unitary matrices, that utilize special generalized Mach-Zehnder interferometers (SGMZIs) as building blocks of various matrix circuit architectures. In the described photonic matrix circuits, SGMZIs are optically coupled in series, ordered by dimensionality and in a size-augmenting manner, between sets of input and output waveguides. Phase shifters in the SGMZIs provide the requisite degrees of freedom for setting the matrix values of the unitary matrix. As an illustrative example, one or more embodiments described herein relate to a unitary matrix configuration (e.g., a unitary matrix circuit architecture). For example, one or more embodiments described herein include a photonic circuit, which may include one or more unitary matrix circuits. One or more embodiments of the unitary matrix circuit includes a plurality of SGMZIs, a plurality of waveguide paths, and a fidelity restoration block. The plurality of SGMZIs may include a first SGMZI having a first dimensionality and a second SGMZI having a second dimensionality (greater than the first dimensionality) coupled in series to the first SGMZI. The plurality of waveguide paths may include a first waveguide path that guides signals through both the first and second SGMZIs and a second waveguide path that guides signals through the second SGMZI (e.g., without conducting signals through the first SGMZI). The fidelity restoration block may include attenuators for balancing outputs of the unitary matrix circuit. As another illustrative example, one or more embodiments described herein relate to an arbitrary matrix configuration (e.g., an arbitrary matrix circuit architecture). For example, one or more embodiments described herein include a photonic circuit, which may include one or more arbitrary matrix circuits. One or more embodiments of the arbitrary matrix circuit includes a first matrix block including a first plurality of SGMZIs coupled in series in order of dimensionality from a lowest dimensionality of the plurality of SGMZIs to a highest dimensionality of the plurality of SGMZIs. The arbitrary matrix circuit may additionally include a second matrix block including a second plurality of SGMZIs coupled in series in reverse order of dimensionality relative to the order of dimensionality that the first plurality of SGMZIs are ordered within the first matrix block. Each of the matrix blocks may include similar features