S. Shoji - Academia.edu (original) (raw)
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Papers by S. Shoji
Optics Letters, 2009
A remarkable recent progress in two-photon photopolymerization is the achievement of fabrication ... more A remarkable recent progress in two-photon photopolymerization is the achievement of fabrication resolution around tens of nanometers, establishing a femtosecond laser as a nanofabrication tool. However, how the superresolution has been made possible is still under arguement. We propose a concept of polymer network permeability to solvents, meaning a structure-loosened nanopolymer state that allows free penetration of small molecules to interpret the mechanism. Experimentally, we found proof showing existence of the state, including an unusually large volume shrinkage rate ͑Ͼ60% ͒, shape-memory effect, a giant softness of nanospring, and the mechanical stability of rinsed two-photon written polymer nanowires.
Advanced materials (Deerfield Beach, Fla.), Jan 27, 2014
Direct laser writing through two-photon polymerization lithography is used to fabricate 3D nanost... more Direct laser writing through two-photon polymerization lithography is used to fabricate 3D nanostructures containing aligned single-wall carbon nanotubes (SWCNTs). SWCNTs are aligned in the laser scanning directions while they are embedded in the structure. The alignment is induced by spatial confinement, volume shrinkage, and the optical gradient force. This method is expected to lead to new applications based on aligned SWCNTs.
Optics express, Jan 15, 2008
The probability to realize a full photonic band gap in two-dimensional birefringent photonic crys... more The probability to realize a full photonic band gap in two-dimensional birefringent photonic crystals can be readily manipulated by introducing symmetry reduction or air holes in the crystal elements. The results lie in either creation of new band gaps or enlargement of existing band gaps. In particular, a combination of the two processes produces an effect much stronger than a simple summation of their individual contributions. Materials with both relatively low refractive index (rutile) and high refractive index (tellurium) were considered. The combined effect of introduction of symmetry reduction and air holes resulted in a maximum enlargement of the band gaps by 8.4% and 20.2%, respectively, for the two materials.
Optics Express, 2008
The probability to realize a full photonic band gap in twodimensional birefringent photonic cryst... more The probability to realize a full photonic band gap in twodimensional birefringent photonic crystals can be readily manipulated by introducing symmetry reduction or air holes in the crystal elements. The results lie in either creation of new band gaps or enlargement of existing band gaps. In particular, a combination of the two processes produces an effect much stronger than a simple summation of their individual contributions. Materials with both relatively low refractive index (rutile) and high refractive index (tellurium) were considered. The combined effect of introduction of symmetry reduction and air holes resulted in a maximum enlargement of the band gaps by 8.4% and 20.2%, respectively, for the two materials.
ACS Photonics, 2014
Nonlinear optical interaction is crucial to alloptical signal processing. In metallic nanostructu... more Nonlinear optical interaction is crucial to alloptical signal processing. In metallic nanostructures, both linear and nonlinear optical interactions can be greatly enhanced by surface plasmon resonance (SPR). In the last few decades, saturation and reverse saturation of absorption in plasmonic materials have been unraveled. It is known that scattering is one of the fundamental light−matter interactions and is particularly strong in metallic nanoparticles due to SPR. However, previous methods measure response from ensemble of nanoparticles and did not characterize scattering on a single particle basis. Here we report that backscattering from an isolated gold nanoparticle exhibits not only saturation, but also reverse saturation. Wavelength-dependent and intensitydependent studies reveal that nonlinear scattering is dominated by SPR and shares a similar physical origin with nonlinear absorption. The reversibility and repeatability of saturable scattering (SS) and reverse saturable scattering (RSS) are validated via repetitive excitation on the same set of particles. Compared to fluorescence, our novel discovery of single-particle-based SS and RSS does not suffer from bleaching and can be used as a more robust contrast agent for optical microscopy. Under a reflection confocal microscope, interesting point-spread functions are observed, with full-width-of-half-maximum of central and side lobes reduced to λ/5 and λ/13, showing great potential for superresolution microscopy.
Optics Letters, 2009
A remarkable recent progress in two-photon photopolymerization is the achievement of fabrication ... more A remarkable recent progress in two-photon photopolymerization is the achievement of fabrication resolution around tens of nanometers, establishing a femtosecond laser as a nanofabrication tool. However, how the superresolution has been made possible is still under arguement. We propose a concept of polymer network permeability to solvents, meaning a structure-loosened nanopolymer state that allows free penetration of small molecules to interpret the mechanism. Experimentally, we found proof showing existence of the state, including an unusually large volume shrinkage rate ͑Ͼ60% ͒, shape-memory effect, a giant softness of nanospring, and the mechanical stability of rinsed two-photon written polymer nanowires.
Advanced materials (Deerfield Beach, Fla.), Jan 27, 2014
Direct laser writing through two-photon polymerization lithography is used to fabricate 3D nanost... more Direct laser writing through two-photon polymerization lithography is used to fabricate 3D nanostructures containing aligned single-wall carbon nanotubes (SWCNTs). SWCNTs are aligned in the laser scanning directions while they are embedded in the structure. The alignment is induced by spatial confinement, volume shrinkage, and the optical gradient force. This method is expected to lead to new applications based on aligned SWCNTs.
Optics express, Jan 15, 2008
The probability to realize a full photonic band gap in two-dimensional birefringent photonic crys... more The probability to realize a full photonic band gap in two-dimensional birefringent photonic crystals can be readily manipulated by introducing symmetry reduction or air holes in the crystal elements. The results lie in either creation of new band gaps or enlargement of existing band gaps. In particular, a combination of the two processes produces an effect much stronger than a simple summation of their individual contributions. Materials with both relatively low refractive index (rutile) and high refractive index (tellurium) were considered. The combined effect of introduction of symmetry reduction and air holes resulted in a maximum enlargement of the band gaps by 8.4% and 20.2%, respectively, for the two materials.
Optics Express, 2008
The probability to realize a full photonic band gap in twodimensional birefringent photonic cryst... more The probability to realize a full photonic band gap in twodimensional birefringent photonic crystals can be readily manipulated by introducing symmetry reduction or air holes in the crystal elements. The results lie in either creation of new band gaps or enlargement of existing band gaps. In particular, a combination of the two processes produces an effect much stronger than a simple summation of their individual contributions. Materials with both relatively low refractive index (rutile) and high refractive index (tellurium) were considered. The combined effect of introduction of symmetry reduction and air holes resulted in a maximum enlargement of the band gaps by 8.4% and 20.2%, respectively, for the two materials.
ACS Photonics, 2014
Nonlinear optical interaction is crucial to alloptical signal processing. In metallic nanostructu... more Nonlinear optical interaction is crucial to alloptical signal processing. In metallic nanostructures, both linear and nonlinear optical interactions can be greatly enhanced by surface plasmon resonance (SPR). In the last few decades, saturation and reverse saturation of absorption in plasmonic materials have been unraveled. It is known that scattering is one of the fundamental light−matter interactions and is particularly strong in metallic nanoparticles due to SPR. However, previous methods measure response from ensemble of nanoparticles and did not characterize scattering on a single particle basis. Here we report that backscattering from an isolated gold nanoparticle exhibits not only saturation, but also reverse saturation. Wavelength-dependent and intensitydependent studies reveal that nonlinear scattering is dominated by SPR and shares a similar physical origin with nonlinear absorption. The reversibility and repeatability of saturable scattering (SS) and reverse saturable scattering (RSS) are validated via repetitive excitation on the same set of particles. Compared to fluorescence, our novel discovery of single-particle-based SS and RSS does not suffer from bleaching and can be used as a more robust contrast agent for optical microscopy. Under a reflection confocal microscope, interesting point-spread functions are observed, with full-width-of-half-maximum of central and side lobes reduced to λ/5 and λ/13, showing great potential for superresolution microscopy.