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Reflectionless excitation of arbitrary photonic structures: a general theory

  • A. Douglas Stone , William R. Sweeney , Chia Wei Hsu , Kabish Wisal and Zeyu Wang
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Frontiers in Optics and Photonics
This chapter is in the book Frontiers in Optics and Photonics

Abstract

We outline and interpret a recently developed theory of impedancematching or reflectionless excitation of arbitrary finite photonic structures in any dimension. The theory includes both the case of guided wave and free-space excitation. It describes the necessary and sufficient conditions for perfectly reflectionless excitation to be possible and specifies howmany physical parameters must be tuned to achieve this. In the absence of geometric symmetries, such as parity and time-reversal, the product of parity and time-reversal, or rotational symmetry, the tuning of at least one structural parameter will be necessary to achieve reflectionless excitation. The theory employs a recently identified set of complex frequency solutions of theMaxwell equations as a starting point, which are defined by having zero reflection into a chosen set of input channels, and which are referred to as R-zeros. Tuning is generically necessary in order to move an R-zero to the real frequency axis, where it becomes a physical steady-state impedancematched solution, which we refer to as a reflectionless scattering mode (RSM). In addition, except in singlechannel systems, the RSM corresponds to a particular input wavefront, and any other wavefront will generally not be reflectionless. It is useful to consider the theory as representing a generalization of the concept of critical coupling of a resonator, but it holds in arbitrary dimension, for arbitrary number of channels, and even when resonances are not spectrally isolated. In a structure with parity and time-reversal symmetry (a real dielectric function) or with parity-time symmetry, generically a subset of the R-zeros has real frequencies, and reflectionless states exist at discrete frequencies without tuning. However, they do not exist within every spectral range, as they do in the special case of the Fabry-Pérot or two-mirror resonator, due to a spontaneous symmetry-breaking phenomenon when two RSMs meet. Such symmetry-breaking transitions correspond to a new kind of exceptional point, only recently identified, at which the shape of the reflection and transmission resonance lineshape is flattened. Numerical examples of RSMs are given for one-dimensional multimirror cavities, a two-dimensionalmultiwaveguide junction, and a multimode waveguide functioning as a perfect mode converter. Two solution methods to find R-zeros and RSMs are discussed. The first one is a straightforward generalization of the complex scaling or perfectly matched layer method and is applicable in a number of important cases; the second one involves a mode-specific boundary matching method that has only recently been demonstrated and can be applied to all geometries for which the theory is valid, including free space andmultimode waveguide problems of the type solved here.

Abstract

We outline and interpret a recently developed theory of impedancematching or reflectionless excitation of arbitrary finite photonic structures in any dimension. The theory includes both the case of guided wave and free-space excitation. It describes the necessary and sufficient conditions for perfectly reflectionless excitation to be possible and specifies howmany physical parameters must be tuned to achieve this. In the absence of geometric symmetries, such as parity and time-reversal, the product of parity and time-reversal, or rotational symmetry, the tuning of at least one structural parameter will be necessary to achieve reflectionless excitation. The theory employs a recently identified set of complex frequency solutions of theMaxwell equations as a starting point, which are defined by having zero reflection into a chosen set of input channels, and which are referred to as R-zeros. Tuning is generically necessary in order to move an R-zero to the real frequency axis, where it becomes a physical steady-state impedancematched solution, which we refer to as a reflectionless scattering mode (RSM). In addition, except in singlechannel systems, the RSM corresponds to a particular input wavefront, and any other wavefront will generally not be reflectionless. It is useful to consider the theory as representing a generalization of the concept of critical coupling of a resonator, but it holds in arbitrary dimension, for arbitrary number of channels, and even when resonances are not spectrally isolated. In a structure with parity and time-reversal symmetry (a real dielectric function) or with parity-time symmetry, generically a subset of the R-zeros has real frequencies, and reflectionless states exist at discrete frequencies without tuning. However, they do not exist within every spectral range, as they do in the special case of the Fabry-Pérot or two-mirror resonator, due to a spontaneous symmetry-breaking phenomenon when two RSMs meet. Such symmetry-breaking transitions correspond to a new kind of exceptional point, only recently identified, at which the shape of the reflection and transmission resonance lineshape is flattened. Numerical examples of RSMs are given for one-dimensional multimirror cavities, a two-dimensionalmultiwaveguide junction, and a multimode waveguide functioning as a perfect mode converter. Two solution methods to find R-zeros and RSMs are discussed. The first one is a straightforward generalization of the complex scaling or perfectly matched layer method and is applicable in a number of important cases; the second one involves a mode-specific boundary matching method that has only recently been demonstrated and can be applied to all geometries for which the theory is valid, including free space andmultimode waveguide problems of the type solved here.

Chapters in this book

  1. Frontmatter i
  2. Preface v
  3. Contents vii
  4. Part I: Optoelectronics and Integrated Photonics
  5. Disorder effects in nitride semiconductors: impact on fundamental and device properties 3
  6. Ultralow threshold blue quantum dot lasers: what’s the true recipe for success? 23
  7. Waiting for Act 2: what lies beyond organic lightemitting diode (OLED) displays for organic electronics? 31
  8. Waveguide combiners for mixed reality headsets: a nanophotonics design perspective 41
  9. On-chip broadband nonreciprocal light storage 75
  10. High-Q nanophotonics: sculpting wavefronts with slow light 83
  11. Thermoelectric graphene photodetectors with sub-nanosecond response times at terahertz frequencies 89
  12. High-performance integrated graphene electro-optic modulator at cryogenic temperature 99
  13. Asymmetric photoelectric effect: Auger-assisted hot hole photocurrents in transition metal dichalcogenides 105
  14. Seeing the light in energy use 115
  15. Part II: Lasers, Active optical devices and Spectroscopy
  16. A high-repetition rate attosecond light source for time-resolved coincidence spectroscopy 119
  17. Fast laser speckle suppression with an intracavity diffuser 131
  18. Active optics with silk 139
  19. Nanolaser arrays: toward application-driven dense integration 151
  20. Two-dimensional spectroscopy on a THz quantum cascade structure 173
  21. Homogeneous quantum cascade lasers operating as terahertz frequency combs over their entire operational regime 183
  22. Toward new frontiers for terahertz quantum cascade laser frequency combs 189
  23. Soliton dynamics of ring quantum cascade lasers with injected signal 197
  24. Part III: Fiber Optics and Optical Communications
  25. Propagation stability in optical fibers: role of path memory and angular momentum 213
  26. Perspective on using multiple orbital-angularmomentum beams for enhanced capacity in freespace optical communication links 229
  27. Part IV: Biomedical Photonics
  28. A fiber optic–nanophotonic approach to the detection of antibodies and viral particles of COVID-19 241
  29. Plasmonic control of drug release efficiency in agarose gel loaded with gold nanoparticle assemblies 253
  30. Metasurfaces for biomedical applications: imaging and sensing from a nanophotonics perspective 265
  31. Hyperbolic dispersion metasurfaces for molecular biosensing 301
  32. Part V: Fundamentals of Optics
  33. A Tutorial on the Classical Theories of Electromagnetic Scattering and Diffraction 323
  34. Reflectionless excitation of arbitrary photonic structures: a general theory 351
  35. Part VI: Optimization Methods
  36. Multiobjective and categorical global optimization of photonic structures based on ResNet generative neural networks 371
  37. Machine learning–assisted global optimization of photonic devices 381
  38. Artificial neural networks for inverse design of resonant nanophotonic components with oscillatory loss landscapes 395
  39. Adjoint-optimized nanoscale light extractor for nitrogen-vacancy centers in diamond 403
  40. Part VII: Topological Photonics
  41. Non-Hermitian and topological photonics: optics at an exceptional point 415
  42. Topological photonics: Where do we go from here? 437
  43. Topological nanophotonics for photoluminescence control 447
  44. Anomalous Anderson localization behavior in gain-loss balanced non-Hermitian systems 455
  45. Part VIII: Quantum Computing, Quantum Optics, and QED
  46. Quantum computing and simulation 467
  47. NIST-certified secure key generation via deep learning of physical unclonable functions in silica aerogels 471
  48. Thomas–Reiche–Kuhn (TRK) sum rule for interacting photons 479
  49. Macroscopic QED for quantum nanophotonics: emitter-centered modes as a minimal basis for multiemitter problems 491
  50. Generation and dynamics of entangled fermion–photon–phonon states in nanocavities 505
  51. Polaritonic Tamm states induced by cavity photons 527
  52. Recent progress in engineering the Casimir effect – applications to nanophotonics, nanomechanics, and chemistry 537
  53. Enhancement of rotational vacuum friction by surface photon tunneling 551
  54. Part IX: Plasmonics and Polaritonics
  55. Shrinking the surface plasmon 561
  56. Polariton panorama 565
  57. Scattering of a single plasmon polariton by multiple atoms for in-plane control of light 595
  58. A metasurface-based diamond frequency converter using plasmonic nanogap resonators 605
  59. Selective excitation of individual nanoantennas by pure spectral phase control in the ultrafast coherent regime 613
  60. Semiconductor quantum plasmons for high frequency thermal emission 623
  61. Origin of dispersive line shapes in plasmon-enhanced stimulated Raman scattering microscopy 633
  62. Epitaxial aluminum plasmonics covering full visible spectrum 643
  63. Part X: Metaoptics
  64. Metamaterials with high degrees of freedom: space, time, and more 657
  65. The road to atomically thin metasurface optics 661
  66. Active nonlocal metasurfaces 673
  67. Giant midinfrared nonlinearity based on multiple quantum well polaritonic metasurfaces 685
  68. Near-field plates and the near zone of metasurfaces 697
  69. High-efficiency metadevices for bifunctional generations of vectorial optical fields 703
  70. Printing polarization and phase at the optical diffraction limit: near- and far-field optical encryption 715
  71. Optical response of jammed rectangular nanostructures 723
  72. Dynamic phase-change metafilm absorber for strong designer modulation of visible light 731
  73. Arbitrary polarization conversion for pure vortex generation with a single metasurface 745
  74. Enhanced harmonic generation in gases using an all-dielectric metasurface 751
  75. Monolithic metasurface spatial differentiator enabled by asymmetric photonic spin-orbit interactions 759
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