Three-dimensional (3D) photonic crystal structures can be fabricated into photopolymerizable resins by using laser beam interference with high precision. Three laser beams interfere into a glass cell filled with a liquid photopolymerizable resin to form a hexagonal periodic structure. Rods are formed in a hexagonal arrangement after being photopolymerzed according to the 3D periodic light distribution which results from the laser’s interference. Two beams of another laser also interfere to form layers which cross perpendicular to the rod array. After photofabrication, the nonsolidified resin is removed by ethanol. The lattice constant can be selected by tuning the angles of the incident beams and the laser wavelength. We have fabricated a 500 μm×500 μm×150 μm photonic crystal structure, the lattice constant of which is 1 μm and contains 150 lateral layers.
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.
We demonstrate the selective aggregation of single-walled carbon nanotubes by photon forces, using the large optical field gradient of a laser focused through a high numerical aperture objective lens. The nanotubes, dispersed in an aqueous solution with a surfactant, are detected via Raman scattering from the confocal volume of the optical trap. By using a visible-light laser for both trapping and detection, the dynamics of the radial breathing mode signal taken at short intervals shows an increase of a single breathing mode over time, indicating the increase in the density of only one species of tube in the focal volume. This result represents a significant step toward the development of techniques for the arbitrary manipulation and sorting of nanotubes by optical fields.
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.
Please cite this article as: Ushiba, S., Shoji, S., Masui, K., Kuray, P., Kono, J., Kawata, S., 3D microfabrication of single-wall carbon nanotube/polymer composites by two-photon polymerization lithography, Carbon (2013), doi: http://dx.doi.org/10. 1016/j.carbon.2013.03.020 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractWe present a method to develop single-wall carbon nanotube (SWCNT)/polymer composites into arbitrary three-dimensional micro/nano structures. Our approach, based on two-photon polymerization lithography, allows one to fabricate three-dimensional SWCNT/polymer composites with a minimum spatial resolution of a few hundreds nm. A near-infrared femtosecond pulsed laser beam was focused onto a SWCNT-dispersed photo resin, and the laser light solidified a nanometric volume of the resin. The focus spot was three-dimensionally scanned, resulting in the fabrication of arbitrary shapes of SWCNT/polymer composites.SWCNTs were uniformly distributed throughout the whole structures, even in a few hundreds nm thick nanowires. Furthermore, we also found an intriguing phenomenon that SWCNTs were self-aligned in polymer nanostructures, promising improvements in mechanical and electrical properties. Our method has great potential to open up a wide range of applications such as micro-and nanoelectromechanical systems, micro/nano actuators, sensors, and photonics devices based on CNTs. Main Text
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