Browsing by Author "Wang, Nan"

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Biological imaging with nonlinear photothermal microscopy using a compact supercontinuum fiber laser source
(2015-04-20)
He, Jinping
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Miyazaki, Jun
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Wang, Nan
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Tsurui, Hiromichi
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Kobayashi, Takayoshi
Nonlinear photothermal microscopy is applied in the imaging of biological tissues stained with chlorophyll and hematoxylin. Experimental results show that this type of organic molecules, which absorb light but transform dominant part of the absorbed energy into heat, may be ideal probes for photothermal imaging without photochemical toxicity. Picosecond pump and probe pulses, with central wavelengths of 488 and 632 nm, respectively, are spectrally filtered from a compact supercontinuum fiber laser source. Based on the light source, a compact and sensitive super-resolution imaging system is constructed. Further more, the imaging system is much less affected by thermal blurring than photothermal microscopes with continuous-wave light sources. The spatial resolution of nonlinear photothermal microscopy is similar to 188 nm. It is similar to 23% higher than commonly utilized linear photothermal microscopy experimentally and similar to 43% than conventional optical microscopy theoretically. The nonlinear photothermal imaging technology can be used in the evaluation of biological tissues with high-resolution and contrast. (C) 2015 Optical Society of America
Generation of stable two-color laser pulses in photonic crystal fiber for microscopy
(2014-09-01)
He, Jinping
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Wang, Nan
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Kobayashi, Takayoshi
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電子物理學系
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Department of Electrophysics
We have generated two-color laser pulses in the visible range from a photonic crystal fiber pumped with a femtosecond Ti:sapphire oscillator. The central wavelengths of the two peaks are 564 and 644 nm with the tunable range of about 10 nm by adjusting the pump intensity. The average power of each peak is higher than 1 mW and the rms stability is 1.3%, which is nearly the same as the pump laser. The most probable mechanism of the formation of the two-color pulses is high-order soliton fission. The two-color femtosecond pulses are useful in microscopy. (C) 2014 The Japan Society of Applied Physics
Label-free imaging of biological tissues with nonlinear photothermal microscopy
(2015)
He, Jinping
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Miyazaki, Jun
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Wang, Nan
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Kobayashi, Takayoshi
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電子物理學系
Nonlinear photothermal microscopy has been applied in imaging of mouse melanoma and spinal cord without any staining. The resolution is higher compared with linear mechanism.
Label-free imaging of melanoma with nonlinear photothermal microscopy
(2015-04-01)
He, Jinping
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Miyazaki, Jun
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Wang, Nan
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Tsurui, Hiromichi
;
Kobayashi, Takayoshi
Nonlinear photothermal microscopy, in which the intensity of the pump heating beam is modulated at f and the photothermal signal is extracted from the probe beam with a lock-in amplifier referred to 2f, is applied to the imaging of mouse melanoma without any staining. The pump and probe pulses, with central wavelengths of 488 and 632 nm, and a pulse duration of similar to 100 ps, are filtered from a compact commercial supercontinuum fiber laser source. An auto-balanced detector is applied to accumulate the signal and remove the laser noise of the probe. The spatial resolution of the nonlinear photothermal imaging is enhanced by similar to 18% in both theoretical calculations and experiments, compared with a linear photothermal mechanism, and the resolution enhancement is theoretically similar to 42% compared with conventional optical microscopy. This imaging technique shows possibilities for the clinical evaluation of melanoma with a high contrast and spatial resolution. (C) 2015 Optical Society of America
Multi-color optical microscopy using modulated excitation lasers and single-frequency demux
(2020-02-01)
Wang, Nan
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Kobayashi, Takayoshi
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Ruan, Shuangchen
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電機學院
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College of Electrical and Computer Engineering
Multi-color microscopy has been a powerful tool for industrial and biomedical applications. Traditionally, image acquisition through different color channels has to be carried out separately using a single detector for sequential detection or multi-detectors for simultaneous detection. This costly and complex process may introduce colocalization errors due to the alignment. This paper describes a compact multi-color microscope using modulated excitation lasers and a single electronic frequency demux for signal detection. To mark fluorescence from different labels in the sample separately, the excitation lasers are intensity modulated with different frequencies. After fluorescence is detected, the electronic signals are demultiplexed with a single spectrum analyzer. This method allows the realization of multi-color imaging with minimal amount of detection elements. Multi-color imaging of fluorescent spheres, gold nanoparticles, and biological tissues are carried out. A fiber-coupling system has also been used to simplify the optical alignments, while its focal chromatic aberration has been characterized.
Noninvasive, label-free, three-dimensional imaging of melanoma with confocal photothermal microscopy: Differentiate malignant melanoma from benign tumor tissue
(2016-07-22)
He, Jinping
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Wang, Nan
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Tsurui, Hiromichi
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Kato, Masashi
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Iida, Machiko
Skin cancer is one of the most common cancers. Melanoma accounts for less than 2% of skin cancer cases but causes a large majority of skin cancer deaths. Early detection of malignant melanoma remains the key factor in saving lives. However, the melanoma diagnosis is still clinically challenging. Here, we developed a confocal photothermal microscope for noninvasive, label-free, three-dimensional imaging of melanoma. The axial resolution of confocal photothermal microscope is similar to 3 times higher than that of commonly used photothermal microscope. Three-dimensional microscopic distribution of melanin in pigmented lesions of mouse skin is obtained directly with this setup. Classic morphometric and fractal analysis of sixteen 3D images (eight for benign melanoma and eight for malignant) showed a capability of pathology of melanoma: melanin density and size become larger during the melanoma growth, and the melanin distribution also becomes more chaotic and unregulated. The results suggested new options for monitoring the melanoma growth and also for the melanoma diagnosis.
Numerical calibration of the spatial overlap for subtraction microscopy
(2015-05-18)
Wang, Nan
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Kobayashi, Takayoshi
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電機學院
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College of Electrical and Computer Engineering
Recently proposed subtraction microscopy provides a simple and compact approach to enhance the spatial resolution. However, inevitable imperfect overlap of the Gaussian and donut spots could deteriorate the quality of the subtracted images, while this effect is rarely investigated quantitatively. Based on vector diffraction theory, the effects of spatial displacements on the image resolution, signal intensity, and subtraction threshold are studied with several microscope parameters here. The peakposition shift is found to be a useful and convenient parameter to inspect and calibrate the spatial overlap of excitation spots in such microscopes. (C) 2015 Optical Society of America
Numerical study of super-resolved optical microscopy with partly staggered beams
(2016-12)
He, Jinping
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Wang, Nan
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Kobayashi, Takayoshi
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電機學院
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College of Electrical and Computer Engineering
The resolving power of optical microscopy involving two or even more beams, such as pump-probe microscopy and nonlinear optical microscopy, can be enhanced both laterally and longitudinally with partly staggered beams. A numerical study of the new super-resolution imaging technology is performed with vector diffraction theory. The influence of polarization is discussed. A resolving power of sub-100 nm and sub-300 nm in the lateral and longitudinal directions, respectively, is achievable.
Numerical study of the subtraction threshold for fluorescence difference microscopy
(2014-11-17)
Wang, Nan
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Kobayashi, Takayoshi
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電子物理學系
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Department of Electrophysics
Subtraction microscopy has recently been promoted for its compactness and simplicity of enhancing spatial resolution. However, until now, the subtraction factors used in such microscopes to process raw images have been chosen experientially, and it has been impossible to determine whether the resolved structures after subtraction are appropriate or over-processed. Based on vector diffraction theory and two-dimensional convolution, this paper presents numerical investigations of the parameters that may offer the selection criterion of subtraction factors used in subtraction microscopy. It proposes two essential parameters for appropriately evaluating the subtraction factor: the fluorescence peak intensity after subtraction and resolution derivative. (C) 2014 Optical Society of America
Polarization modulation for fluorescence emission difference microscopy
(2015-05-18)
Wang, Nan
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Kobayashi, Takayoshi
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先進超快雷射研究中心
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Adv Ultrafast Laser Ctr
Effects of the polarization on subtracted images in fluorescence emission difference microscopy are numerically investigated based on vector beam diffraction theory and alteration of Jones matrices. Parameters of resolution, signal loss, and amplitude of negative sidebands after subtraction are discussed along with the polarization of excitation beams and sample sizes. The effects of polarization on the ellipticity and subtraction threshold are also given. (C) 2015 Optical Society of America
Sub-diffraction-limit imaging using mode multiplexing
(2015-05-15)
Wang, Nan
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Miyazaki, Jun
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He, Jinping
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Seto, Keisuke
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Kobayashi, Takayoshi
Pixel-by-pixel processed fluorescence difference microscopy is experimentally demonstrated by multiplexing excitation laser beams with Gaussian and donut spot shapes and then demultiplexing the fluorescent signals using lock-in amplifiers. With this scheme, a fixed sample of fluorescent spheres and a slice of mouse brain tissue are imaged with resolutions that exceed the diffraction limit. Compared to previously reported subtraction imaging techniques, this pixel-by-pixel scan can be applied to improve the resolution of a moving sample without introducing subtraction errors. The synchronized signal detection feature makes this method extendible to various applications. (C) 2014 Elsevier B.V. All rights reserved.
Sub-diffraction-limit imaging using mode multiplexing
(2015-01-01)
Wang, Nan
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He, Jinping
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Miyazaki, Jun
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Tsurui, Hiromichi
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Kobayashi, Takayoshi
Simultaneous two-color subtraction microscopy using mode multiplexing is realized experimentally. The samples are irradiated with single laser diode at wavelength of 445 nm. Then the beam split laser spots generate separate solid and donut spatial modes and are multiplexed with modulators for simultaneous excitation. The produced fluorescence signals are back collected and further divided into two color bands with dichroic mirrors. Then they are detected with two photomultipliers and demultiplexed in four lock-in amplifiers. Four fluorescence images are recorded in every scan and resolution enhanced images are obtained in two color channels after applying the subtraction strategy. With this method, imaging results of microspheres stained with organic dyes and mesenteric lymph nodes of a mouse labeled with quantum dots (Q525/650) are realized. Improvement of 20% similar to 30% in resolving power of the two color channels compared with confocal microscopy is achieved in with corresponding subtraction factor of about 0.3.
Subtraction threshold for an isotropic fluorescence emission difference microscope
(2015-12-01)
Wang, Nan
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Kobayashi, Takayoshi
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電機學院
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College of Electrical and Computer Engineering
Isotropic fluorescence emission difference microscopy proposed recently provides a simple method to enhance the spatial resolution in three-dimensions (3D) for fluorescence imaging. However, the subtraction threshold to achieve the condition for appropriately resolving the sample in 3D have not been studied. Then the subtraction factors used in this type of microscopes are still experientially chosen. Based on vector diffraction theory and a 3D numerical model developed here, the subtraction threshold is numerically investigated for the isotropic fluorescence subtraction microscopy. The subtraction factors and peak intensities at the threshold are obtained and comparied both in lateral and axial planes for achieving most appropriate subtraction and inspecting the isotropic characteristic. The effects of radius ratios of implemented 0-pi annular phase plate for generating three dimensional donut spot on the subtracted resolution, peak intensity and negative sidebands are also discussed.