Nippon Telegraph and Telephone Corporation

Nippon Telegraph and Telephone Communications

Shigeo Ishibashi

Kazunori Naganuma

Takashi Sakamoto

Masahiro Ueno

Tadayuki Imai

Seiji Toyoda

Shogo Yagi

Kazuto Noguchi

Yuichi Okabe

Jun Miyazu

Kazutoshi Kato

Itaru Yokohama

Yuzo Ishida

A light source employed in a coherent Raman scattering (CRS) spectroscopic apparatus or a CRS microscope includes a chromium forsterite laser (CrFL), a variable delay optical path configured to delay one optical pulse of branched optical pulses obtained by dividing an optical pulse from the CrFL according to a power, a highly nonlinear waveguide into which the other optical pulse of the branched optical pulses is input, a first wavelength filter connected to an output of the highly nonlinear waveguide, an ytterbium-doped glass fiber optical amplifier (YbFA) connected to an output of the wavelength filter, and a second wavelength filter connected to an output of the YbFA. The light source includes a one-optical path mode in which two wavelength bands corresponding to Raman scattering wavenumbers to be used for measurement are selected from an output of the variable delay optical path, and a two-optical path mode in which an output of the variable delay optical path and an output of the second wavelength filter are time-synchronized.

Light source

Provided is a method for producing a crystal fiber which can suppress the occurrence of stress birefringence even while distributing a light emission center so as to concentrate on a cross-sectional middle portion. The method for producing a crystal fiber comprises the steps of: using, as a preform, the crystal fiber comprising a light emission center that volatilizes from a melted portion upon the melting of a crystal, and heating a portion or a plurality of portions of the side of the preform, whereby the portion or the plurality of portions of the preform are melted such that only a given amount of the inside of the portion or the plurality of portions of the preform is not melted, to form the melted portion; and sequentially transferring the melted portion in the longitudinal direction of the preform, and cooling the melted portion, whereby the melted portion is continuously recrystallized to form a recrystallized region.

Crystal fiber manufacturing method

A wavelength swept light source includes a sawtooth waveform as a main waveform and an exponential component of the sawtooth waveform to the controlled voltage of the electro-optic deflector. The controlled voltage is controlled so that, as an oscillation wavelength to be swept is swept towards a longer wavelength side, a change rate of the oscillation wavelength is increased.

Wavelength swept light source

According to the process of the present invention for producing a garnet single crystal fiber, a crystal is grown while the direction of a seed crystal, corresponding to the direction of growth, is set in a direction having angles of at least 10.degree. from a direction equivalent to the &lt;100&gt; orientation, at least 20.degree. from a direction equivalent to the &lt;110&gt; orientation and at least 20.degree. from a direction equivalent from the &lt;211&gt; orientation. The resulting garnet single crystal fiber does not include a core, which is formed due to facet formation, and has an excellent optical homogeneity necessary for use in an optical device such as a laser device or an isolator.

Process for producing garnet single crystal

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Musashino, Japan

Shigeo Ishibashi