Time-dependent optical force theory for optomechanics of dispersive 3D photonic materials and devices.

We present a position- and time-dependent optical force theory for optomechanics of dispersive 3D photonic materials and devices. The theory applies to media including material interfaces, waveguides, and general photonic crystal structures. The theory enables calculation of the dynamical state of the coupled field-material system and the interference of this state with other excitations of the material, such as surface acoustic waves or phonons. As an example, we present computer simulations of energy and momentum flows through a silicon crystal with anti-reflective structured interfaces. Using commercially available simulation tools, the theory can be applied to analyze optical forces in complex photonic materials and devices.

Negative radiation pressure in metamaterials explained by light-driven atomic mass density rarefication waves.

The momentum and radiation pressure of light in negative-index metamaterials (NIMs) are commonly expected to reverse their direction from what is observed for normal materials. The negative refraction and inverse Doppler effect of light in NIMs have been experimentally observed, but the equally surprising phenomenon, the negative radiation pressure of light, still lacks experimental verification. We show by simulating the exact position- and time-dependent field-material dynamics in NIMs that the momentum and radiation pressure of light in NIMs can be either positive or negative depending on their subwavelength structure. In NIMs exhibiting negative radiation pressure, the negative total momentum of light is caused by the sum of the positive momentum of the electromagnetic field and the negative momentum of the material. The negative momentum of the material results from the optical force density, which drives atoms backward and reduces the local density of atoms at the site of the light field. In contrast to earlier works, light in NIMs exhibiting negative radiation pressure has both negative total momentum and energy. For the experimental discovery of the negative radiation pressure, one must carefully design the NIM structure and record the joint total pressure of the field and material momentum components.

Light-driven mass density wave dynamics in optical fibers.

We have recently developed the mass-polariton (MP) theory of light to describe the light propagation in transparent bulk materials [Phys. Rev. A 95, 063850 (2017)]. The MP theory is general as it is based on the covariance principle and the fundamental conservation laws of nature. Therefore, it can be applied also to nonhomogeneous and dispersive materials. In this work, we apply the MP theory of light to describe propagation of light in step-index circular waveguides. We study the eigenmodes of the electric and magnetic fields in a waveguide and use these modes to calculate the optical force density, which is used in the optoelastic continuum dynamics (OCD) to simulate the dynamics of medium atoms in the waveguide. We show that the total momentum and angular momentum in the waveguide are carried by a coupled state of the field and the medium. In particular, we focus in the dynamics of atoms, which has not been covered in previous theories that consider only field dynamics in waveguides. We also study the elastic waves generated in the waveguide during the relaxation following from atomic displacements in the waveguide.

Location of novel benzanthrone dyes in model membranes as revealed by resonance energy transfer.

Förster resonance energy transfer (FRET) between anthrylvinyl-labeled phosphatidylcholine (AV-PC) as a donor and newly synthesized benzanthrones (referred to here as A8, A6, AM12, AM15 and AM18) as acceptors has been examined to gain insight into molecular level details of the interactions between benzanthrone dyes and model lipid membranes composed of zwitterionic lipid phosphatidylcholine and its mixtures with anionic lipids cardiolipin (CL) and phosphatidylglycerol (PG). FRET data were quantitatively analyzed in terms of the model of energy transfer in two-dimensional systems taking into account the distance dependence of orientation factor. Evidence for A8 location in phospholipid headgroup region has been obtained. Inclusion of CL and PG into PC bilayer has been found to induce substantial relocation of A6, AM12, AM15 and AM18 from hydrophobic membrane core to lipid-water interface.