Showing papers by "Norihiko Nishizawa published in 2014"

Development of a high power supercontinuum source in the 1.7 μm wavelength region for highly penetrative ultrahigh-resolution optical coherence tomography

Abstract: We developed a high power supercontinuum source at a center wavelength of 1.7 μm to demonstrate highly penetrative ultrahigh-resolution optical coherence tomography (UHR-OCT). A single-wall carbon nanotube dispersed in polyimide film was used as a transparent saturable absorber in the cavity configuration and a high-repetition-rate ultrashort-pulse fiber laser was realized. The developed SC source had an output power of 60 mW, a bandwidth of 242 nm full-width at half maximum, and a repetition rate of 110 MHz. The average power and repetition rate were approximately twice as large as those of our previous SC source [20]. Using the developed SC source, UHR-OCT imaging was demonstrated. A sensitivity of 105 dB and an axial resolution of 3.2 μm in biological tissue were achieved. We compared the UHR-OCT images of some biological tissue samples measured with the developed SC source, the previous one, and one operating in the 1.3 μm wavelength region. We confirmed that the developed SC source had improved sensitivity and penetration depth for low-water-absorption samples.

Ultrashort pulse fiber lasers and their applications

Abstract: Fiber lasers, which consist of ideal waveguides of optical fibers, work as stable, practical, and maintenance-free lasers. A passively mode-locked ultrashort pulse fiber laser using the intensity-dependent absorption element has made great progress using a new type of saturable absorber with a nanocarbon material. The techniques of ultrashort pulse amplification and pulse compression were also developed. Using a combination of specialty fibers, ultrawideband pulse sources, such as wavelength tunable ultrashort pulses and supercontinuum, can be demonstrated. These new light sources are useful for laser applications, especially for optical metrology. In this paper, the progress of highly functional ultrashort pulse fiber laser sources and their applications are reviewed mainly on the basis of the works of this author.

Octave spanning coherent supercontinuum generation using 51 fs high-power ultrashort pulse from Er-doped similariton amplifier

Abstract: A 51 fs, 4.4 nJ, almost-pedestal-free, high-power ultrashort pulse was generated using an Er-doped similariton amplifier. Using the generated ultrashort pulse, high-power, octave-spanning coherent supercontinua broadened from 1.05 to 2.15 and 0.95 to 2.3 µm were generated in highly nonlinear fibers. The characteristics of the similariton amplifier were investigated experimentally.

Supercontinuum generation for ultrahigh-resolution optical coherence tomography at wavelength of 0.8 µm using carbon nanotube fiber laser and similariton amplifier

Abstract: We demonstrated supercontinuum (SC) generation for ultrahigh-resolution optical coherence tomography (UHR-OCT) in the 0.8 µm wavelength region using an ultrashort-pulse fiber laser system. An Er-doped ultrashort-pulse fiber laser with single-wall carbon nanotubes was developed as the seed pulse source. A 46 fs, highest quality, pedestal-free, clean, ultrashort pulse was generated with a similariton amplifier. Then, a 60 fs ideal ultrashort pulse was generated at a wavelength of 0.8 µm with a second-harmonic generation (SHG) crystal, and a Gaussian-like SC was generated in a photonic crystal fiber. UHR-OCT was demonstrated using the generated SC, and precise images of a biological sample were observed.

Ultrashort pulse generation using supercontinuum generated by Er-doped fiber laser with carbon nanotube

Abstract: Ultrashort pulse generation was demonstrated by dispersion compensation of coherent high quality supercontinuum generated by ultrashort pulse fiber laser with carbon nanotube and fiber amplifier system. A 22 fs ultrashort pulse was observed by X-FROG.

Ultrabroadband spontaneous parametric fluorescence in 800 nm region toward ultrahigh-resolution quantum optical coherence tomography

Abstract: Quantum optical coherence tomography can realize high-resolution imaging with dispersion tolerance by virtue of quantum entanglement. We generate ultrabroadband spontaneous parametric fluorescence from chirped quasi-phase matching devices to achieve the ultrahigh-resolution imaging.

Advance of Wideband Ultra-Short Pulse Fiber Lasers and Sensing Applications

Abstract: We demonstrated wideband wavelength tunable narrow linewidth pulses and high quality super continuum using fiber lasers with carbon nanotube. Ultrahigh resolution optical coherence tomography and spectroscopic measurement were demonstrated.

Ultrahigh-resolution optical coherence tomography using supercontinuum source in 1.9 μm wavelength region

Abstract: Ultrahigh-resolution OCT in 1.9 mm wavelength region was demonstrated using fiber laser supercontinuum. The wavelength dependence of imaging was investigated, and the decrement in attenuation coefficient in longer-wavelength was confirmed for tooth sample.

Carbon-Nanotube Mode-Locked Fiber Lasers and Their Applications to OCT

Abstract: Authors have been investigating highly functional ultrahoshort pulse fiber laser using single wall carbon nanotube. High power supercontinuum was generated at 1.7 μm wavelength region, and highly sensitive and penetrative ultrahigh resolution OCT was demonstrated.

Octave spanning coherent supercontinuum generation by 46 fs pedestal free ultrashort pulse using similariton amplifier and Er-doped fiber laser with carbon nanotube

Abstract: 46 fs, 4.0 nJ pedestal free high power ultrashort pulse was generated using Er-doped similariton amplifier seeded by nanotube fiber laser. An octave spanning coherent supercontinuum was generated in highly nonlinear normal dispersion fiber.