Browsing by Author "He, Jinping"

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18.7-fs DUV pulses generated by using chirped-pulse four-wave mixing in bulk material
(2014)
He, Jinping
;
Kobayashi, Takayoshi
;
電子物理學系
;
Department of Electrophysics
Sub-20fs, wavelength tunable, uJ-level DUV pulses were generated by using nondegenerate, chirped-pulse four-wave mixing in CaF2 crystal. The DUV spectrum can be tuned from 257nm to 277nm with widest spectral width of 16.8nm. The compact DUV laser system is useful in pump-probe experiment for investigating ultrafast dynamics in biological molecules.
Biological imaging with nonlinear photothermal microscopy using a compact supercontinuum fiber laser source
(2015-04-20)
He, Jinping
;
Miyazaki, Jun
;
Wang, Nan
;
Tsurui, Hiromichi
;
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
;
Wang, Nan
;
Kobayashi, Takayoshi
;
電子物理學系
;
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
Generation of sub-20-fs deep-ultraviolet pulses by using chirped-pulse four-wave mixing in CaF2 plate
(2013-08-15)
He, Jinping
;
Kobayashi, Takayoshi
;
電子物理學系
;
Department of Electrophysics
Sub-20-fs deep ultraviolet (DUV) pulses are generated by using nondegenerate, chirped-pulse four-wave mixing of the fundamental and second-harmonic pulses from a commercial Ti:sapphire amplifier in a CaF2 plate. The energy of the DUV pulses is 3.8 mu J, with a conversion efficiency from total pump energy to DUV of similar to 3.8%. The DUV pulse is compressed using a pre-chirp, introduced via a fused silica window in the fundamental beam. The central wavelength of the DUV spectrum can be tuned from 257 to 277 nm by adjusting the cross angle between the two pump beams. The spectrum can reach a width of 16.8 nm, which can support a pulse duration of 8.7 fs. (C) 2013 Optical Society of America
Label-free imaging of biological tissues with nonlinear photothermal microscopy
(2015)
He, Jinping
;
Miyazaki, Jun
;
Wang, Nan
;
Kobayashi, Takayoshi
;
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
;
Miyazaki, Jun
;
Wang, Nan
;
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
Low-threshold and compact multicolored femtosecond laser generated by using cascaded four-wave mixing in a diamond plate
(2013-03-01)
He, Jinping
;
Du, Juan
;
Kobayashi, Takayoshi
;
電子物理學系
;
Department of Electrophysics
Low-threshold and compact multicolored laser generated by cascaded four-wave mixing in a diamond plate is demonstrated. The spectra and output energy of the generated sidebands up to 2nd order on the Stokes side and > 12th on the anti-Stokes side covering from near infrared to UV, are shown. The 2-D multicolor arrays were also observed in diamond plate with low threshold and explained briefly. The compact wavelength-tunable multicolored laser setup is promising to be used in spectroscopy experiments, for example multicolor pump-probe experiments. (C) 2012 Elsevier B.V. All rights reserved.
Mechanism study of 2-D laser array generation in a YAG crystal plate
(2015-07-27)
Zeng, Tao
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He, Jinping
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Kobayashi, Takayoshi
;
Liu, Weiwei
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電子物理學系
We have reproduced the process of two-dimensional array generation by using two crossing laser beams in a YAG crystal plate based on numerical simulation considering cross-phase modulation (XPM) and self-focusing. Furthermore, we come to the conclusion that both XPM and the cylindrical symmetry breaking in the initial beam profile contributes to the generation of two-dimensional array. In addition, we have studied the threshold input laser beam power for the two crossing beams splitting in a YAG crystal plate. Our study could be valuable in various applications, such as 2-D all-optical switching devices or multicolor pump-probe experiments. (C) 2015 Optical Society of America
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
;
Kato, Masashi
;
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 study of super-resolved optical microscopy with partly staggered beams
(2016-12)
He, Jinping
;
Wang, Nan
;
Kobayashi, Takayoshi
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電機學院
;
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.
Sub-diffraction-limit imaging using mode multiplexing
(2015-05-15)
Wang, Nan
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Miyazaki, Jun
;
He, Jinping
;
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
;
He, Jinping
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Miyazaki, Jun
;
Tsurui, Hiromichi
;
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.
Tunable Multicolored Femtosecond Pulse Generation Using Cascaded Four-Wave Mixing in Bulk Materials
(2014-09-01)
He, Jinping
;
Liu, Jun
;
Kobayashi, Takayoshi
;
電子物理學系
;
Department of Electrophysics
This paper introduces and discusses the main aspects of multicolored femtosecond pulse generation using cascaded four-wave mixing (CFWM) in transparent bulk materials. Theoretical analysis and semi-quantitative calculations, based on the phase-matching condition of the four-wave mixing process, explain the phenomena well. Experimental studies, based on our experiments, have shown the main characteristics of the multicolored pulses, namely, broadband spectra with wide tunability, high stability, short pulse duration and relatively high pulse energy. Two-dimensional multicolored array generation in various materials are also introduced and discussed.