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Spatially formed two-photon interference fringes with fringe periods smaller than the diffraction limit are demonstrated. In the experiment, a fringe formed by two-photon NOON states with wavelength λ=702.2 nm is observed using a specially developed near-field scanning optical microscope probe and two-photon detection setup. The observed fringe period of 328.2 nm is well below the diffraction limit (351 nm = λ/2). Another experiment with a path-length difference larger than the coherent length of photons confirms that the observed fringe is due to two-photon interference. ©2007 Optical Society of America

Numerical simulation of stimulated emission and lasing in dye doped cholesteric liquid crystal films J. Appl. Phys. 113, 063106 (2013) Influence of the excitation area on the thresholds of organic second-order distributed feedback lasers APL: Org. Electron. Photonics 5, 256 (2012) Influence of the excitation area on the thresholds of organic second-order distributed feedback lasers

The enhancement of multiphoton emission from a single colloidal nanocrystal quantum dot (NQD) interacting with a plasmonic nanostructure was investigated using a silver-coated atomic force microscopy tip (AgTip) as the plasmonic nanostructure. Using the AgTip, which exhibited a well-defined localized surface plasmon (LSP) resonance band, we controlled the spectral overlap and the distance between the single NQD and the AgTip. The emission behavior of the single NQD when approaching the AgTip at the nanometer scale was measured using off-resonance (405 nm) and resonance (465 nm) excitation of the LSP. We directly observed the conversion of the single-photon emission from a single NQD to multiphoton emission with reduction of the emission lifetime at both excitation wavelengths as the NQD-AgTip distance decreased, whereas a decrease and increase in the emission intensity were observed at 405 and 465 nm excitation, respectively. By combining theoretical analysis and the numerical simulation of the AgTip, we deduced that the enhancement of the multiphoton emission was caused by the quenching of the single-exciton state due to the energy transfer from the NQD to the AgTip and that the emission intensity was increased by enhancement of the excitation rate due to the electric field of the LSP on the AgTip. These results provide evidence that the photon statistics and the photon flux from the single NQD can be manipulated by the plasmonic nanostructure through control of the spectral overlap and the distance.

Surface enhanced Raman scattering (SERS) was measured on periodic and randomly arranged patterns of Au nano-bricks (rectangular parallelepipeds). Resonant SERS conditions were investigated of a near-IR dye deposited on nanoparticles. Random mixtures of Au nano-bricks with different aspect ratio R showed stronger SERS enhancement as compared to periodic patterns with constant aspect ratio (R varies from 1 to 4). SERS mapping revealed up to ∼ 4 times signal increase at the hot-spots. Experimental observation is verified by numerical modeling and is qualitatively consistent with generic scaling arguments of interaction between plasmonic nanoparticles. The effect of randomization on the polarization selectivity for the transverse and longitudinal modes of nano-bricks is shown. , 1998). 33. For example, consider a one-dimensional intensity distribution I 1 (x), having constant value 1 for 0 < x < 10, and a second distribution I 2 (x) having value 0.8 for 0 < x < 8 and 1.8 for 8 < x < 10. While the two distributions have the same average I 1 = I 2 = 1, I 2 (x) is clearly less uniform than I 1 (x). This is reflected in the greater value of the variance estimator I 2 2 / I 2 2 =1.16 with respect to I 2 1 / I 1 2 =1. In order to maximize its value the distribution should have a high degree of non-uniformity, which can be slightly increased by mixing nano-bricks with high aspect ratio, while it is the greatest (thus high enhancement) for a random distribution. When R is increased, for the T-mode the non-uniformity is increased and the wavelength decreased, both of which favor an increase in Raman scattering relative to extinction (as the Raman scattering cross-section is proportional to 1/λ 4 ). For the L-mode, both non-uniformity and wavelength increase, thus the two factors compensate each other, reducing the growth of Raman intensity with R. 34. G. Sun, J. B. Khurgin, and A. Bratkovsky, "Coupled-mode theory of field enhancement in complex metal nanostructures," Phys. Rev. B 84, 045415 (2011).

Fano resonance in a tapered optical fiber in contact with a high-Q microsphere is demonstrated. Multimode waves propagating in a 2.3 m diameter taper were coupled with a single whispering gallery mode of a 220 m sphere, and their coherent interaction resulted in Fano resonance. The asymmetric line shapes of the transmission spectra changed periodically with scanning of the coupling position along the taper. The observed 24 m period was due to modal dispersion in the tapered fiber.

Poly(N-isopropylacrylamide) (PNIPA) gel has attracted considerable attention, from both the academic and technological viewpoints. [1][2][3][4][5][6] PNIPA gel undergoes an abrupt volume change at the phase-transition temperature (ca. 34 8C), [1] which can be utilized in several promising applications such as drug delivery systems and actuators. [4,5] For better performance of these applications, several strategies have been reported to exploit the rapid volume change of PNIPA gels. [7][8][9] However, PNIPA gel also exhibits salt-tolerant water absorbency through the incorporation of surfactants such as sodium dodecyl sulfate (SDS).[2] The behavior of the PNIPA gel in surfactant solutions has been extensively studied, [10] but little research has been reported on PNIPA gels containing polymeric surfactants. In our studies, poly(2-(methacryloyloxy)decyl phosphate) (PMDP) was chosen as the polymeric surfactant, which was expected to afford a superabsorbent PMDP-containing PNIPA (PNIPA-PMDP) gel in the presence of salts. The PNIPA-PMDP gel did not exhibit superabsorbency in sodium chloride solutions, but interestingly showed a rapid volume change above its phase transition temperature when compared to conventional PNIPA gels. Herein, we report the rapid volume change of PNIPA-PMDP gels as a function of temperature as well as by laser-beam irradiation. Our results clearly demonstrate the PMDPinduced enhancement of the response dynamics for the polymeric network of PNIPA gels.The PNIPA gels were synthesized by free-radical polymerization under the reaction conditions shown in Table 1 (see Experimental Section). PMDP was readily prepared from 2-(methacryloyloxy)decyl phosphate by free-radical polymerization at about 25 8C (Scheme 1). To determine the phase-transition temperature of the gels, the value of V/V c was measured, in which V and V c are the gel volumes at the target and at the highest temperatures of the measurements, respectively. Notably, V c does not represent the volume of the completely collapsed structure, especially for the PNIPA gel,[*] Dr.

Erratum: "Optical patterning and photochemical fixation of polymer nanoparticles on glass substrates" [Appl.