RESUMO
The spontaneous emission rate of a fluorophore provides a direct probe of the photonic local density of states at the fluorophore position. Here we exploit this capability to map the plasmonic modes of gold nanoparticles by imaging the fluorescence intensity in combined regular arrays of identical gold and fluorophore-doped polymer nanoparticles. By varying the distance between gold and polymer particles across the array, the fluorophore emission generates an optical Moiré pattern corresponding to a magnified spatial map of the plasmonic mode, which can be directly imaged with an optical microscope. Our results are corroborated by supplementary theoretical model calculations.
RESUMO
We demonstrate a two-window heterodyne method for measuring the x-p cross correlation, ??(*)(x)? (p)?, of an optical field ? for transverse position x and transverse momentum p. This scheme permits independent control of the x and p resolution. A simple linear transform of the x-p correlation function yields the Wigner phase-space distribution. This technique is useful for both coherent and low-coherence light sources and may permit new biological imaging techniques based on transverse coherence measurement with time gating. We point out an interesting analogy between x-p correlation measurements for classical-wave and quantum fields.
