Finer features for functional microdevices

Kawata, Satoshi; Sun, Hong–Bo; Tanaka, Tomonari; Takada, Kenji

doi:10.1038/35089130

Cited by 2,622 publications

(1,558 citation statements)

References 11 publications

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“…Depending on the nature of this coupling, the ground state or the excited state may be either localized or delocalized, and specific optical properties may be either enhanced or suppressed. 44 Among the many NLO effects, two-photon absorption (TPA) has become very popular during the past decade owing to its wide-ranging applications such as two-photon laser scanning microscopy, [45][46][47] photodynamic therapy, 48 optical power limitation, 4,5 microfabrication, [49][50][51][52] or 3D optical data storage. [53][54][55][56] Depending on the applications, two-photon chromophores have to satisfy different kinds of requirements.…”

Section: Introductionmentioning

confidence: 99%

Effects of (Multi)branching of Dipolar Chromophores on Photophysical Properties and Two-Photon Absorption

et al. 2005

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To investigate the effect of branching on linear and nonlinear optical properties, a specific series of chromophores, epitome of (multi)branched dipoles, has been thoroughly explored by a combined theoretical and experimental approach. Excited-state structure calculations based on quantum-chemical techniques (timedependent density functional theory) as well as a Frenkel exciton model nicely complement experimental photoluminescence and one-and two-photon absorption findings and contribute to their interpretation. This allowed us to get a deep insight into the nature of fundamental excited-state dynamics and the nonlinear optical (NLO) response involved. Both experiment and theory reveal that a multidimensional intramolecular charge transfer takes place from the donating moiety to the periphery of the branched molecules upon excitation, while fluorescence stems from an excited state localized on one of the dipolar branches. Branching is also observed to lead to cooperative enhancement of two-photon absorption (TPA) while maintaining high fluorescence quantum yield, thanks to localization of the emitting state. The comparison between results obtained in the Frenkel exciton scheme and ab initio results suggests the coherent coupling between branches as one of the possible mechanisms for the observed enhancement. New strategies for the rational design of NLO molecular assemblies are thus inferred on the basis of the acquired insights.

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Section: Introductionmentioning

confidence: 99%

Effects of (Multi)branching of Dipolar Chromophores on Photophysical Properties and Two-Photon Absorption

et al. 2005

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“…With the adoption of multi-photon imaging and microfabrication as standard techniques, 20,21 interest in designing 55 chromophores with large two-photon cross-sections has expanded rapidly. [22][23][24][25][26] Recently, focus has turned to compounds for two-photon excited PDT, although only a few of these have shown in vitro activity and few in vivo studies have been published.…”

Section: Introductionmentioning

confidence: 99%

One- and two-photon activated phototoxicity of conjugated porphyrin dimers with high two-photon absorption cross sections

et al. 2009

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“…[11] In this report, we fabricate high-quality polymeric 3D spiral photonic crystals via direct laser writing. [12][13][14] The measured transmittance spectra of these low-index-contrast structures reveal spectral regions where the transmittance is below 5 % for one circular incident polarization and above 95 % for the other-for just eight lattice constants along the propagation direction. The experimental data are compared with scattering-matrix calculations [15,16] for the actual finite structures, leading to good agreement.…”

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confidence: 95%

Polarization Stop Bands in Chiral Polymeric Three‐Dimensional Photonic Crystals

et al. 2007

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Chiral 3D photonic crystals are an interesting subclass of 3D photonic crystals. For example, large complete 3D photonic bandgaps have been predicted for high-index-contrast silicon square-spiral structures; [1,2] corresponding experiments using glancing-incidence deposition, [3,4] interference lithography, [5] or direct laser writing [6,7] have been published. In addition to complete gaps or stop bands, theory [8] also predicts polarization stop bands, i.e., stop bands for just one of the two circular polarizations. Such polarization stop bands can give rise to strong circular dichroism, [4,9,10] which can potentially be used for constructing compact "thin-film" optical diodes. [11] In this report, we fabricate high-quality polymeric 3D spiral photonic crystals via direct laser writing. [12][13][14] The measured transmittance spectra of these low-index-contrast structures reveal spectral regions where the transmittance is below 5 % for one circular incident polarization and above 95 % for the other-for just eight lattice constants along the propagation direction. The experimental data are compared with scattering-matrix calculations [15,16] for the actual finite structures, leading to good agreement.For what conditions do we expect strong circular dichroism? For circular polarization of light, the tip of the electricfield vector simply follows a spiral. The pitch of this spiral is just the material wavelength k. Thus, intuitively, we expect a chiral resonance from spiral photonic crystals if the pitch of circularly polarized light matches the pitch of the dielectric spirals, i.e., the lattice constant a z . This condition, k/a z = 1, corresponds to the edge of the second Brillouin zone, i.e., to a wave number k z = 2p/k = 2p/a z . Recall that the edge of the first Brillouin zone is at k z = p/a z . Thus, one does not anticipate a strong chiral response around and below the fundamental stop band (or bandgap), but rather at higher frequencies. Theory [8] for high-index silicon-based structures confirms this intuitive reasoning. We have repeated similar calculations for low-index-contrast polymeric structures, revealing essentially the same trends. The parameters of the 3D spiral photonic crystals to be discussed below are the result of an optimization with respect to circular dichroism.The samples in our experiments are made by direct laser writing, which essentially allows for the fabrication of almost arbitrarily shaped 3D photoresist structures. [12][13][14] Details of our process based on the commercial thick-film resist SU-8 can be found in the Experimental section and in earlier work. [13] Our structures are mechanically supported by a 2D network of bars at, or close to, the top of the 3D crystal. As the spirals are not at all mechanically connected to their neighbors, very unstable low-quality structures would result without this grid. Furthermore, all the structures for optical experiments are surrounded by a thick massive wall (see Fig. 1a), which aims at reducing the effects of strain on the 2D grid cau...

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Finer features for functional microdevices

Cited by 2,622 publications

References 11 publications

Effects of (Multi)branching of Dipolar Chromophores on Photophysical Properties and Two-Photon Absorption

Effects of (Multi)branching of Dipolar Chromophores on Photophysical Properties and Two-Photon Absorption

One- and two-photon activated phototoxicity of conjugated porphyrin dimers with high two-photon absorption cross sections

Polarization Stop Bands in Chiral Polymeric Three‐Dimensional Photonic Crystals

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