Research topics

Our group focuses on the novel laser technology and laser measuring technique, and develops ultrashort pulse fiber laser sources with the wavelengths from visible to mid-infrared region. Based on the novel fiber laser sources, optical frequency combs, ultrabroad band supercontinuum sources, and bioimaging/sensing techniques are being developed.

Ultrashort pulse fiber laser source

With single-wall carbon nanotubes and nonlinear optical effects in fibers, we are developing the ultrashort pulse laser sources. Part of the achievements to date are listed below.

Nishizawa et al., Opt. Express 11, 325 (2009)
Senoo et al., Opt. Express 18, 20673 (2010)
Nishizawa et al., Opt. Express. 19, 21874 (2011)
Nishizawa et al., Photonics 2, 808 (2015)

Fiber laser based optical frequency comb

The pulses from mode-locked laser, have a series of discrete, equally spaced frequency lines (longitudinal modes) in the spectral space. The appearance just likes the comb for hair, thus we call it as optical frequency comb. Optical frequency combs are working as the clocks with the highest accuracy, and applied in various field of optical metrology.
Our group focus on the realization of metrology with ultrahigh accuracy and creation of novel optical application technology. Novel fiber laser based optical frequency combs from near-infrared to mid-infrared are under developing.

Tsuzuki et al., Photon. Res.4, 313 (2016)
Jin et al., Appl. Phys. Express.accepted (2016)

Ultrabroad band supercontinuum soures

Supercontinuum is a laser source with ultrabroad wavelength band. Based on the nonlinear optical effects in the fiber, our group developed ultrabroad band sources with flat spectra over the wavelengths of 0.4 – 1.4 um and 1 -2 um. With the ultrabroad band and flatness of the spectra, the techniques of high accurate spectroscopy and ultrashort pulse generation are under developing.

Nishizawa et al., Jpn. J. Appl. Phys. 40, L365 (2001)
Hori et al., Opt. Express. 12, 317 (2004)
Takayanagi et al., Jpn. J. Appl. Phys. 45, L441 (2006)
Nishizawa et al., J. Opt. Soc. Am. B. 26, 426 (2009)
Nozaki et al., Jpn. J. Appl. Phys. 53, 020301 (2014)

Wavelength tunable ultrashort fiber laser sources

With the high peak power of ultrashort pulses and fiber nonlinearities, conventional unavailable light can be generated. Our group successfully developed the sources with ultrabroad band and high wavelength shifting speed during the wavelength ranges of 1.0 – 1.7 um and 1.5 -2.0 um.

Nishizawa et al., IEEE PTL. 11, 325 (1999)
Takayanagi et al., IEEE PTL. 18, 2284 (2006)
Nishizawa et al., Opt. Express. 24, 23403 (2016)

High-resolution optical coherence tomography

Optical coherence tomography (OCT) is a non-invasive optical imaging technique, which enables micrometer-scale cross-sectionalimaging of biological tissues and materials. With our ultrabroad band supercontinuum sources in 0.8 um, 1.1 um, 1.3 um. and 1.7 um spectral bands, our group developed varieties of OCT systems with axial resolution of sub um - a few um.

Nishizawa et al., Opt. Lett. 29, 2846 (2004)
Ishida et al., Biomed. Opt. Express 3, 282 (2012)
Hattori et al., Appl. Phys. Express 8, 082501 (2012)
Yamanaka et al., Appl. Phys. Express 9, 022701 (2016)

Optical coherence tomography and microscopy in optical window Ⅲ (λ:1600-1870 nm) for high-resolution deep-tissue imaging

Our group are developing optical coherence microscopy (OCM) in 1700-nm wavelength region (optical window Ⅲ) for deep-tissue 3D high-resolution imaging. In this study, we utilized our fiber laser based supercontinuum source in 1700-nm as light source for OCM. With the 1700-nm OCM we developed, we successfully visualized deep part of mouse brain with high spatial resolution.

Ishida et al., Appl. Phys. Express.4, 052501 (2011)
Kawagoe et al., Biomed. Opt. Express 5, 932 (2014)
Yamanaka et al., Sci. Rep. Express 6, 3175 (2016)
Kawagoe et al., Appl. Phys. Express 9, 127002 (2016)

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Nishizawa laboratory, Department of Electronics
Nagoya University

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