Fluorescence enhancement and nonreciprocal transmission of light waves by nanomaterial interfaces

Abstract

In an optically absorbing or amplifying linear medium, the energy flow density of interfering optical waves is in general periodically modulated in space. This makes the wave transmission through a material boundary, as described by the Fresnel transmission coefficients, nonreciprocal and apparently violating the energy conservation law. The modulation has been previously described in connection to ordinary homogeneous nonmagnetic materials. In this work, we extend the description to nanomaterials with designed structural units that can be magnetic at optical frequencies. We find that in such a "metamaterial" the modulation in energy flow can be used to enhance optical far-field emission in spite of the fact that the material is highly absorbing. We also demonstrate a nanomaterial design that absorbs light, but simultaneously eliminates the power flow modulation and returns the reciprocity, which is impossible to achieve with a nonmagnetic material. We anticipate that these unusual optical effects can be used to increase the efficiency of nanostructured light emitters and absorbers, such as light-emitting diodes and solar cells.

Near-field spatial coherence of structured incoherent optical sources

“…The reciprocity is valid also for each plane-wave component of the field at Q, as a consequence of the same two-point reciprocity, but with the second point, Q', located at infinity in the direction of the plane-wave propagation (Q' is shown in Fig. 3(b) schematically) [21,22,25]. Hence, in our numerical calculations, we can send each radiated plane-wave component (with an amplitude E Q (k x , k y ) and given k x and k y ) back to the source and evaluate the field amplitude E 0 (r 1 ) at each point P [see Fig.…”

“…The model enables effective estimation of the transverse coherence function and coherence length of an arbitrary periodically structured source and offers the possibility to tailor the structure to obtain the desired coherence properties. The calculation method is based on the optical reciprocity theorem [21][22][23][24][25] that allows us to study the radiation properties and spatial coherence of the source in terms of coupling of external plane waves to the structure. We describe the method in detail in the next section and then demonstrate its application by calculating the coherence length for radiation from several light sources.…”