Nanooptics and photonics
1D polaritons in macroporous silicon with nano-coatings
L. Karachevtseva, O. Lytvynenko, O. Sapelnikova

Laboratory of Photonic Semiconductor Structures, V. Lashkaryov Institute of Semiconductor Physics, NASU, Prsp. Nauki, 41, Kiev-03028, Ukraine. 
E-mail: lakar@isp.kiev.ua

We investigated high-resolution IR absorption, 1D exciton-polaritons in periodical 2D macroporous silicon structures with nano-coatings of SiO2 and CdS nanoparticles. In 2D macroporous silicon with nano-coatings the generated photoelectrons link heavily with holes in the macropore potential pits forming interference 2D polaritons [1]. In addition, high-resolution IR absorption resulted in generation of dipole-active TO vibrations and measurement giant two-polar absorption oscillations with amplitudes of ±107arb.un. As a result, the dispersion law in yz surfaces of cylindrical macropores change to z direction along macropores. Thus, 2D polariton transforms to 1D polariton with the giant two-polar oscillations according to the secand law in spectral area of TO-vibrations of Si-Si-bonds and Pb centers.
Surface polaritons interact with photons strongly due to resonances of dipole-active vibrations and surface modes on boundaries Si-SiO2 and SiO2+"РЕІ-ncCdS" on macropores. Shape of oscillations corresponds to the interference of polaritons as own states of system "nanocoating - silicon matrix - waveguide modes". In our case, the vertically polarized light along macropores (z direction) and horizontally polarized light (x direction) permit the explanation of results as two-photon interference (the Hong-Ou-Mandel effect) [2]. In this case, the macropore surface is a beam splitter (BS) with maximum and minimum coincidences for measurements with parallel and perpendicularly polarizations, respectively. Beam splitter includes input ports A and B, and output ports labelled C and D. The four ways of the two photons can exit from the beam splitter through the same port or different ports. We observed “constructive” interference of the two-photon states corresponding to photons exiting through the same output ports (bozonic behavior) for 2D polaritons. We measured “destructive” interference of the two-photon states corresponding to photons exiting through the input and output ports (fermionic behavior) for 1D polaritons. 

1.	Karachevtseva, L., Kuchmii, S., Lytvynenko, O., et .al. Oscillations of Light Absorption in 2D Macroporous Silicon Structures with Surface Nanocoatings. // Appl. Sur. Sci.–2011.–257.–P. 3331-3335.
2.	Ou, Z., Hong, C. & Mandel, L. Relation between input and output states for a beam splitter // Optics Communications.–1987.–63, N 2.–P. 118-122.