Extraordinary momentum and spin in evanescent waves

By K. Bliokh, A. Bekshaev, Franco Nori. Nature Communications, 2013

711 citations recorded by the source corpus.

Momentum and spin represent fundamental dynamic properties of quantum particles and fields. In particular, propagating optical waves (photons) carry momentum and longitudinal spin determined by the wave vector and circular polarization, respectively. Here we show that exactly the opposite can be the case for evanescent optical waves. A single evanescent wave possesses a spin component, which is independent of the polarization and is orthogonal to the wave vector. Furthermore, such a wave carries a momentum component, which is determined by the circular polarization and is also orthogonal to the wave vector. We show that these extraordinary properties reveal a fundamental Belinfante’s spin momentum, known in field theory and unobservable in propagating fields. We demonstrate that the transverse momentum and spin push and twist a probe Mie particle in an evanescent field. This allows the observation of ‘impossible’ properties of light and of a fundamental field-theory quantity, which was previously considered as ‘virtual’. The momentum and spin of a propagating photon are given by its wave vector and circular polarization, respectively. Bliokh et al.here show that evanescent electromagnetic waves possess a polarization-dependent momentum component and a polarization-independent spin component, which are both orthogonal to the wave vector.

Subfields: Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/f309482bc0838b2c0697749077eb9db68557c87c

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In Atomic and Molecular Physics, and Optics

1. Franco Nori
2. Nathan Goldman
3. K. Bliokh
4. A. Bekshaev
5. A. Amo
6. T. Ozawa
7. H. Price
8. M. Rechtsman

Citations in the corpus

• Atoms in complex twisted light (2018, background): “Bliokh et al [219] explored the local momentum and spin distributions of evanescent”
• Optical tweezers and their applications (2018, background): “Note that the time-averaged Poynting vector can be decomposed into the sum of an orbital and spin momentum density [48] and hence the non-conservative optical forces are related to the orbital component of the field momentum directed as the local wavevector [40, 49].”
• Topological photonics (2018, background): “to the surface, the polarization acquires a circular component corresponding to a nonvanishing transverse spin component, whose sign changes with the propagation direction (Bliokh et al., 2014; Bliokh and Nori, 2012).”
• Universal spin-momentum locking of evanescent waves (2015, background): “A quantum field theoretic treatment has also recently shed light on the interesting spin properties of evanescent waves [10, 11].”
• Quantum spin Hall effect of light (2015, background): “ge modes with strong spin-momentum locking are wellknown evanescent waves, which appear at any interface supporting surface waves. We show that recently discovered transverse spin in evanescent waves [27,28] and several very recent experimental demonstrations of the strong transverse spin-directiona”
• Structured Light: Ideas and Concepts (2020, methodology): “This is in contrast with the spinning mechanical action exerted by fields with SAM: a dipole particle can feel the field-induced mechanical torque T = Te + Tm only if it absorbs a part of the incident radiation [50, 51],”
• Direct measurements of the extraordinary optical momentum and transverse spin-dependent force using a nano-cantilever (2015, methodology): “The generation of the evanescent field and its properties at such interface are described in detail in the Supplementary Materials of [7].”
• Transverse and longitudinal angular momenta of light (2015, background): “This question was recently examined by Bliokh and Nori [47], and it was concluded that such transverse intrinsic orbital AM can naturally occur in polychromatic fields with non-stationary intensity distributions.”
• Transverse spin and momentum in two-wave interference (2014, methodology): “(8)], which is analogous to the helicity-dependent transverse momentum in evanescent waves (first found by Fedorov and Imbert [14,15] and explained only very recently [10]).”