Optical Spectroscopy Using a Solid As a Single-Molecule Trap

As was recently demonstrated 1 by using highly efficient fluorescence excitation spcctroscopy with N.A. = 0.98 collection optics, single impurity molecules in both crystals and polymers may now be detected with single-to-noiseratios (SNRs) as high as 30 in a 1 Hz bandwidth at low temperatures. In essence, the solid may be regarded as a trap for the single molecule, which effectively quenches rotation. Our measurements include precise determination of the lifetime limited linewidth and the temperature dependence of the optical dephasing, as well as spectral diffusion (wandering in frequency space due to perturbations by lattice degrees of freedom). For the polymeric host, light-induced changes in resonant frequency of a single molecule can be produced, a process that is normally termed spectral hole-burning when large ensembles of molecules are probed. In recent studies, nonclassical light emission from a single molecule (photon antibunching) has been observed in a fashion analogous to that reported earlier for a single atom in a trap.