We have demonstrated a nano-particle rotation above a plasmon-resonant gold multimer nano-structures with a nano-gap and a circularly polarized laser. We have confirmed that the rotational direction depends on the number of triangle nano-structure. And the multiple position trapping has been realized with a control of triangle nano-structure.
KEYWORDS: Deposition processes, Nanoantennas, Molecules, Scanning electron microscopy, Gold, Luminescence, Near field optics, Nanoparticles, Plasmonics
In this work, we demonstrate an original single-nanoparticle deposition process based on near-field optical forces
arising from much localized plasmonic resonant gap-mode. At first, nanoparticles exclusively made of fluorescent dye
molecules are fabricated in aqueous colloidal suspension. Near-field optical forces are then used to attract and deposit
single nanoparticles in the nanogap of plasmonic nanoantennas. This one-step deposition process allows targeted
deposition of nanoscale materials directly from a colloidal dispersion to a few-nanometer large area of interest.
In this paper, we have demonstrated a nano-particle rotation above a plasmonic gold trimer nano-structure with a nanogap.
We designed the plasmonic trimer nano-structure which has a resonant frequency matched to excitation and made it
with electron beam lithography with metal lift-off process. At first, with an actively rotating linearly polarized beam
excitation, we have realized a rotational motion of a trapped nano-particle synchronized to a polarization of beam. Next,
we observed a nano-particle rotation using a circularly polarized beam. From the auto-correlation of position time trace
with sinusoidal fitting, we confirmed a faster rotation of nano-particle than that of an actively rotating linearly polarized
beam.
We investigate the wavelength dependence of localized plasmonic field distributions in a gold nanodimer structure
under total internal reflection condition. Although a gold dimer structure is well known to induce strong localized mode at
a nanogap, we find that the higher-order plasmonic modes are excited by the oblique light incidence and their interference
effect enables us to observe the modification of localized filed distributions at the nano-scale even in a simple gold
nanodimer structure depending on the detection wavelength. This change in the plasmonic field distribution would
provide important knowledge for their potential applications such as plasmonic trapping, spectroscopy, and sensing.
Protein crystals are required for X-ray crystallography to determine three-dimensional structures of proteins at atomic resolution. The conventional microscopy is currently used for observation and screening of protein crystals. However, the three-dimensional imaging, which is important for automated treatment of protein crystals, is generally difficult by light microscopy. In addition, the protein crystals in the media are frequently difficult to identify by conventional light microscopy owing to the appearance of salt crystals or amorphous materials. In this work, we successfully demonstrated micro-scale, non-invasive, three-dimensional cross-sectional imaging of protein crystals using ultrahigh resolution optical coherence tomography (UHR-OCT). A low noise, Gaussian like, high power supercontinuum at wavelength of 800 nm was used as the light source. The axial resolution of 2 um in sample and the sensitivity of 95 dB were achieved. Since the protein crystal has homogeneous nano-structure, the optical scattering is negligibly small. Therefore, we used gel-inclusion technique to enhance the intensity of scattered signals, and clear, sharp 3D cross-sectional images of protein crystals were successfully observed. As the gel concentration was increased, the OCT signal intensity was increased. Using this method, the protein crystals surrounded by substantial amount of precipitates could be visualized, which is difficult by conventional light microscopy. The discrimination of protein and salt crystals was also demonstrated by the OCT signal intensity. The wavelength dependence of OCT imaging for protein crystal was examined at wavelength of 800-1700 nm regions. It was confirmed that the finest images were observed using 800 nm wavelength system.
Optical coherence tomography (OCT) is a non-invasive optical imaging technology for micron-scale cross-sectional imaging of biological tissue and materials. We have been investigating ultrahigh resolution optical coherence tomography (UHR-OCT) using fiber based supercontinuum (SC) source. Although UHR-OCT has many advantages in medical equipments, low penetration depth is a serious limitation for wider applications. Recently, we have demonstrated high penetration depth UHR-OCT by use of fiber based Gaussian shaped SC source at 1.7 μm center wavelength. However, the penetration depth has been limited by the low power of SC source. In this paper, to realize deeper penetration imaging, we have developed the high power Gaussian shaped SC source at 1.7 μm wavelength region based on the custom-made Er-doped ultrashort pulse fiber laser with single-wall carbon nanotube and nonlinear phenomena in fibers. This SC source has 43.3 mW output power, 242 nm full-width at half maximum bandwidth, and 109 MHz repetition rate. The repetition rate and average power were almost twice as large as those of previous SC source. Using this light source, 105 dB sensitivity and ultrahigh resolution of 4.3 μm in tissue were achieved simultaneously. We have demonstrated the UHR-OCT imaging of pig thyroid gland and hamster’s cheek pouch with this developed SC source and compared the images with those measured by the previous SC source. We have observed the fine structures such as round or oval follicles, epithelium, connective tissue band, and muscular layer. From the comparison of the UHR-OCT images and signals, we confirmed the improvement of imaging contrast and penetration depth with the developed SC source.
We have been investigating ultrahigh resolution optical coherence tomography (UHR-OCT) imaging of lung tissues
using fiber based super continuum (SC) sources. The high power, low-noise, Gaussian shaped SC generated with
ultrashort pulses and optical fibers at several wavelength regions were used as the broadband light sources for UHROCT. Since the lung consists of tiny alveoli which are separeted by thin wall, the UHR-OCT is supposed to be effective for lung imaging. The normal and diseased lung tissues were observed without invasive procedures to the lung itself. The clear images of alveoli were observed with index matching effect by saline. In this work, we investigated the three-dimensional UHR-OCT imaging of lung structure. The lungs of rats inflated with 10% formalin at 5 cmH2O, 15 cmH2O, and 20 cmH2O pressure were prepared as the sample for investigation of size and shape of the lung structure. These samples were fixed with 10% formalin. The interalveolar septa, thin walls separating the alveoli, were clearly observed. The difference of size and shape of alveoli and thier three-dimensional network was clearly observed from the UHR-OCT images. The clear images of alveoli were observed with index matching effect of 10% formalin. We investigated the wavelength dependence of 3D UHR-OCT image of lung structure at 800 nm, 1060 nm, and 1700 nm wavelength regions. The 3D UHR-OCT images of structure of rat lung were clearly observed in all wavelength regions and wavelength dependence of imaging was discussed.
We have been investigating ultrahigh resolution optical coherence tomography (UHR-OCT) imaging of lung tissues
using fiber super continuum sources. The high power, low-noise, Gaussian shaped supercontinuum generated with
ultrashort pulses and optical fibers at several wavelengths were used as the broadband light sources for UHR-OCT. For
the 800 nm wavelength region, the axial resolution was 3.0 um in air and 2.0 um in tissue. Since the lung consists of tiny
alveoli which are separated by thin wall, the UHR-OCT is supposed to be effective for lung imaging. The clear images of
alveoli of rat were observed with and without index matching effects by saline.
In this work, we investigated the UHR-OCT imaging of lung disease model. The lipopolysaccharide (LPS) induced acute
lung injury / acute respiratory distress syndrome (ALI/ARDS) model of rat was prepared as the sample with disease and
the UHR-OCT imaging of the disease part was demonstrated. The increment of signal intensity by pleural thickening
was observed. The accumulation of exudative fluid in alveoli was also observed for two samples. By the comparison
with normal lung images, we can obviously show the difference in the ALI/ARDS models.
Since the lung consists of alveolar surrounded by capillary vessels, the effect of red-blood cells (RBC) is considered to
be important. In this work, ex-vivo UHR-OCT imaging of RBC was demonstrated. Each RBC was able to be observed
individually using UHR-OCT. The effect of RBC was estimated with the rat lung perfused with PBS.
Optical coherence tomography (OCT) is a non invasive optical imaging technology for micron-scale cross-sectional
imaging of biological tissue and materials. We have been investigating ultrahigh resolution optical coherence
tomography (UHR-OCT) using fiber based supercontinuum sources. Although ultrahigh longitudinal resolution was
achieved in several center wavelength regions, its low penetration depth is a serious limitation for other applications. To
realize ultrahigh resolution and deep penetration depth simultaneously, it is necessary to choose the proper wavelength to
maximize the light penetration and enhance the image contrast at deeper depths. Recently, we have demonstrated the
wavelength dependence of penetration depth and imaging contrast for ultrahigh resolution OCT at 0.8 μm, 1.3 μm, and
1.7 μm wavelength ranges. In this paper, additionally we used SC sources at 1.06 μm and 1.55 μm, and we have
investigated the wavelength dependence of UHR-OCT at five wavelength regions. The image contrast and penetration
depth have been discussed in terms of the scattering coefficient and water absorption of samples. Almost the same
optical characteristics in longitudinal and lateral resolution, sensitivity, and incident optical power at all wavelength
regions were demonstrated. We confirmed the enhancement of image contrast and decreased ambiguity of deeper
epithelioid structure at longer wavelength region.
Optical coherence tomography (OCT) based on Michelson interferometer has widely been utilized in biology and
medicine as a type of optical biopsy and quantum optical coherence tomography (QOCT) based on Hong-Ou-Mandel
interferometer has recently been demonstrated. By use of quantum entangled photon pairs generated via spontaneous
parametric down conversion (SPDC) process, axial resolution of QOCT can be better than that of OCT in principle for a
source of same bandwidth and group velocity dispersion (GVD) effect for QOCT can be automatically cancelled thanks
to the frequency correlation of entangled photon pairs.
To realize high-resolution QOCT, we need a broadband quantum entangled photon pair source. Then we proposed a
novel conventional method to generate broadband spontaneous parametric fluorescence via SPDC by using multiple
nonlinear crystals pumped by a CW laser. Our method has controllability to tune the center frequency of generated
photons and scalability to extend the number of crystals. This conventional method can enable us to achieve sub-micron
axial resolution of QOCT.
Optical coherence tomography (OCT) is an emerging technology for non-invasive cross-sectional imaging of
biological tissue and material with um resolution. Recently, non-invasive high resolution cross-sectional imaging is
desired for investigation of diseases in lung in the field of pulmonary medicine. So far, a few works have been reported
about OCT imaging of lung. Since the lung consists of alveoli separated by thin wall, ultrahigh resolution (UHR) OCT is
supposed to be effective for the imaging of fine structure in lung tissue.
In this work, ex vivo cross-sectional imaging of isolated rat lungs was demonstrated using UHR-OCT. A 120 nm-wide,
high-power, Gaussian-like supercontinuum (SC) was generated at wavelength of 0.8 um region and it was used as the
light source in time domain UHR-OCT. An ultrahigh resolution of 2.1 um in tissue was obtained and the achieved
sensitivity was 105 dB.
For the UHR-OCT imaging of trachea, the detailed structures of the tracheal cartilage and tracheal mucosa overlying
the cartilage were observed clearly. The epithelium and lamina propria were also distinguishable.
For the imaging of visceral pleura and alveoli, when saline was instilled into the lung, the penetration depth was
improved, and clear images of the fine structure of the lung, including alveoli, were observed owing to the index
matching effect. The clear images of up to about 4 alveoli were observed below the visceral pleura. The shape of the
alveolar septum was clearly observed, and the alveolar sac was clearly visible.
Optical coherence tomography (OCT) is a non invasive optical imaging technology for micron-scale cross-sectional
imaging of biological tissue and materials. Although OCT has many advantages in medical equipments, low penetration
depth is a serious limitation for other applications. To realize the ultrahigh resolution and the high penetration depth at
the same time, it is effective to choose the proper wavelength to maximize the light penetration and enhance the image
contrast at deeper depths. Recently, we have demonstrated ultrahigh resolution and high penetration depth OCT by use
of all-fiber based Gaussian shaped supercontinuum source at 1.7 μm center wavelength. Gaussian-like supercontinuum
with 360 nm bandwidth at center wavelength of 1.7 μm was generated by ultrashort pulse Er doped fiber laser based
system. In this paper, using 0.8 μm and 1.3 μm SC sources in addition to the 1.7 μm SC source, we have investigated the
wavelength dependence of ultrahigh resolution OCT in terms of penetration depth. Longitudinal resolutions at each
wavelength region are almost 4.6 μm in air. The obtained sensitivity was 95 dB for all wavelength regions. We
confirmed the difference of imaging contrast and penetration depth with hamster's cheek pouch and so on. As the
wavelength was increased, the magnitude of penetration depth was increased for these samples.
Optical coherence tomography (OCT) is an emerging technology for non-invasive cross-sectional imaging of
biological tissue and material with um resolution. In the field of pulmonary medicine, non-invasive high resolution
cross-sectional imaging is desired for investigation of diseases in lung. So far, a few works have been reported about
OCT imaging of lung. Since the lung consists of alveoli separated by thin wall, ultrahigh resolution (UHR) OCT is
supposed to be effective for the imaging of fine structure in lung tissue.
In this work, ex vivo cross-sectional imaging of isolated rat and hamster lungs was demonstrated using UHR-OCT. A
120 nm-wide, high-power, Gaussian-like supercontinuum (SC) was generated at wavelength of 0.8 um region. The
generated SC was used in a time-domain OCT system, and UHR-OCT imaging was demonstrated. An ultrahigh
resolution of 2.9 um in air and 2.1 um in tissue was obtained. The achieved sensitivity was 105 dB. Using this system,
ex vivo UHR-OCT imaging of isolated rat and hamster lungs was demonstrated for the first time. The structures of the
trachea, visceral pleura, and alveoli were observed clearly. When saline was instilled into the lung, the penetration depth
was improved, and clear images of the fine structure of the lung, including alveoli, were observed owing to the index
matching effect.
We have also demonstrated the UHR-OCT imaging of lung tissue using 1.3 um and 1.7 um SC sources. As the
results, owing to the precise structures of lung tissues and index matching by saline, the finest images were observed
with 0.8 um UHR-OCT system.
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