We demonstrate how the resolution and imaging depth limitations of nonlinear optical microscopy can be overcome by modulating the spatial overlap between two-color pulses. We suppress out-of-focus signals, which limit the imaging depth, by a factor of 100, and enhance the lateral and axial resolution by factors of 1.6 and 1.4–1.8 respectively. Using spatial overlap modulation, we demonstrate background-free three-dimensional imaging of fixed mouse brain tissue at depths for which the signals of the conventional technique are swamped by background noise from out-of-focus regions.

We demonstrate super-resolution imaging with background fluorescence rejection by interferometric temporal focusing microscopy, in which temporal focusing is combined with structured illumination. The lateral resolution and the optical sectioning capability are simultaneously improved by factors of 1.6 and 1.4, respectively, compared to conventional temporal focusing microscopy. Fluorescent beads (200 nm diameter) that are difficult to distinguish from the background fluorescence in conventional temporal focusing microscopy, are clearly visualized by interferometric temporal focusing microscopy.

ABSTRACT:Our previous studies on the structure-property relation of dimer liquid crystals (LC), :x.w-bis(4-cyanobiphenyl-4' -yloxy)alkanes (CBA-11. n = 9. l 0). have been extended to include trimer compounds, 4.4' -bis[w-(4-cyanobiphcnyl-4' -yloxy)alkoxy]biphenyls (CBA-Tn. 11=9.10), comprising three mesogenic units jointed by two intervening spacers. These nematic-LC-forming compounds were chosen as a model for the mainchain-type polymer LCs on the assumption that the spatial configuration and thermodynamic roles of the flexible spacer arc nearly identical as long as the chemical structure of the repeating unit is similar. The 2 H NMR method was extensively used to elucidate the oricntational characteristics of these molecules in the mesophase. The analysis of binary mixtures with a low molar mass (monomer) LC gave an important information regarding the mesophase structure ofCBA-Tn as well as CBA-11. The pressure-volume-temperature (PVT) relation was determined to estimate the constant-volume transition entropies at the interphase such as crystal/nematic LC/isotropic melt. The results were found to be favorably compared with the conformational entropy changes derived on the basis of the rotational isomeric state analysis of the 2 H NMR data. Finally. an important role of the flexible spacer was emphasized in determining the molecular ordering as well as thermodynamic properties of mainchain-type LCs.

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