Momentum considerations inside near-zero index materials

Abstract

Near-zero index (NZI) materials, i.e., materials having a phase refractive index close to zero, are known to enhance or inhibit light-matter interactions. Most theoretical derivations of fundamental radiative processes rely on energetic considerations and detailed balance equations, but not on momentum considerations. Because momentum exchange should also be incorporated into theoretical models, we investigate momentum inside the three categories of NZI materials, i.e., inside epsilon-and-mu-near-zero (EMNZ), epsilon-near-zero (ENZ) and mu-near-zero (MNZ) materials. In the context of Abraham–Minkowski debate in dispersive materials, we show that Minkowski-canonical momentum of light is zero inside all categories of NZI materials while Abraham-kinetic momentum of light is zero in ENZ and MNZ materials but nonzero inside EMNZ materials. We theoretically demonstrate that momentum recoil, transfer momentum from the field to the atom and Doppler shift are inhibited in NZI materials. Fundamental radiative processes inhibition is also explained due to those momentum considerations inside three-dimensional NZI materials. Absence of diffraction pattern in slits experiments is seen as a consequence of zero Minkowski momentum. Lastly, consequence on Heisenberg inequality, microscopy applications and on the canonical momentum as generator of translations are discussed. Those findings are appealing for a better understanding of fundamental light-matter interactions at the nanoscale as well as for lasing applications.

New Horizons in Near-Zero Refractive Index Photonics and Hyperbolic Metamaterials

“…However, as noted by Einstein in his seminal work, 55,56 momentum deserves equal theoretical attention due to its conservation property. Examining light−matter interactions inside NZI materials from a momentum perspective, 57 associated Minkowski's momentum to the canonical momentum, which is closely correlated to the wave-like nature of light and to the phase refractive index. 62 On the other hand, the Abraham momentum is connected to the kinetic momentum and a particle description of light, represented in equations by the group index.…”

Advances in Meta-Optics and Metasurfaces: Fundamentals and Applications

“…Previous efforts often focused on metallic metasurfaces [ 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 ], which can enhance light–matter interactions and introduce versatile control of incoming light by activating local plasmonic resonance, albeit with limited efficiency due to ohmic loss [ 78 , 79 , 80 , 81 , 82 , 83 ]. Dielectric metasurfaces overcome the limitation of metallic metasurfaces, which have provided a promising way to develop highly efficient and multi-functional meta-devices [ 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 ].…”

A tutorial on the conservation of momentum in photonic time-varying media

“…Nevertheless, certain aspects of the momentum of the electromagnetic field are still under question [32]. Moreover, the avenue of near-zero-index (NZI) media exacerbates the differences between the forms of the momentum [33][34][35] giving rise to zero Minkowski momentum but nonzero Abraham momentum inside epsilon-and-mu-near-zero (EMNZ) media where both permittivity and permeability approach zero.…”