Ando Electric Company

Keisuke Asami

Akishige Ito

Fumio Akikuni

Naoto Satoh

Akishige Itoh

There is provided a wavelength tunable light sourcein which one end surfaceof a semiconductor laseris applied anti-reflection film, a lenscollimates a light beam emitted from the one end surfaceof the semiconductor laseronto which the anti-reflection film is applied, and a wavelength selection portion constituted by a combination of a diffraction gratingand a mirrorselects a light beam having a desired wavelength to return the selected light to the semiconductor laserto make laser oscillation. A center of rotation of the mirroris provided in a position Pwhere mode hopping can be suppressed when the wavelength is tuned and rotation of the mirroris driven by a direct drive system by using a motorhaving a rotation shaftin the center of rotation of the mirror

Wavelength tunable light source

A light source for an external cavity laser comprises a semiconductor laser having a first facet to which is applied an antireflection coating A and a second facet to which is applied a increased reflection coating B defining a predetermined reflectivity, lenses a diffraction grating and a mirror wherein a light emitted from the first facet is converted into a parallel light by the lens and the parallel light passes through the diffraction grating to select a wavelength and is reflected to the diffraction grating by the mirror to select a wavelength via the diffraction grating again, and the parallel light is converged by the lens to be fed back to the semiconductor laser , and a light emitted from the second facets is converged by the lens to be output to an optical fiber

Light source for an external cavity laser

A wavelength-variable light source equipped with a semiconductor laser , one end of which is provided with an antireflection coating A, is equipped with a power correction filter which permits transmission of the light output from the semiconductor laser , thereby rendering the characteristics of the output light substantially flat. The wavelength-variable light source is an external-resonator-type laser light source which converts the light output from the end face covered with the antireflection coating A of the semiconductor laser into collimated light, subjects the light to wavelength selection by a wavelength selection optical element , returns the light to the wavelength selection optical element by means of a mirror , to thereby subject the light again to wavelength selection by the wavelength selection optical element , feeds the light back to the semiconductor laser , and converges and outputs light output from the other end face of the semiconductor laser on and to an optical fiber . The power correction filter is interposed between the semiconductor laser and the optical fiber

Wavelength-variable light source, and optical component loss measuring device

An external resonator type wavelength variable light source comprises a semiconductor laser formed on one end face with a antireflection coating , a lens for converting emitted light from the end face of the semiconductor laser formed with the antireflection coating into collimated light, a diffraction grating for selecting a wavelength of the collimated light provided through the lens and diffracting the light, and a mirror for reflecting the light diffracted through the diffraction grating and feeding back the light again diffracted through the diffraction grating into the semiconductor laser through the lens . A V-groove grating mirror having reflecting faces with an arrangement like a grating, of a plurality of V grooves each shaped like V at right angles in cross section in a base material with a reflection coating formed on the surface of each V groove is used as the mirror.

V-groove grating mirror and external resonator type wavelength variable light source using the mirror

An external cavity laser type light source including a light emitting element, a wavelength selection element for selecting a wavelength of light emitted from the light emitting element and for returning light to the light emitting element, and an optical branch element arranged between the light emitting element and the wavelength selection element. In the external cavity laser type light source, selected light sent from the wavelength selection element is branched by the optical branch element, and one branched component is taken out as output light.

External cavity laser type light source

In an optical interferometer, incident light is divided into reflected light and transmitted light which travel along respective optical paths, which are orthogonal to each other. The reflected light is subjected to total reflection by means of a first reflector , and the transmitted light is subjected to total reflection by means of a second reflector . The light reflected by the first reflector and the light reflected by the second reflector are again merged by means of the beam splitter into a single ray, and the thus-merged ray falls on a photodetector . The optical interferometer is equipped with a third reflector which reflects the incident light at right angles so as to fall on the beam splitter , and a fourth reflector which reflects the light, having been transmitted through the beam splitter , at right angles so as to fall on the second reflector . The beam splitter and the third and fourth reflectors and are mounted on a moving member which can be moved along an optical path extending between the first reflector and the photodetector

Optical interferometer

An external cavity type light source which has a semiconductor laser ( ) coated on one end ( ) with a reflection prevention film ( A), wherein emitted light from the end face of the semiconductor laser 1 on the reflection prevention film side is converted into collimated light and the collimated light having a wavelength selected through a diffraction grating ( ) is fed back into the semiconductor laser ( ), and wherein emitted light from an opposite end ( ) of the semiconductor laser ( ) is converted into collimated light and the collimated light is gathered and output to an optical fiber ( ). An unpolarized light splitter (light branch element) ( ) is placed between the diffraction grating ( ) and the semiconductor laser ( ), and the diffracted light fed back into the semiconductor laser from the diffraction grating is made to branch through the unpolarized light splitter ( ) and one branch light is taken out as output light through an optical fiber ( ).

External cavity type light source

A semiconductor laser light source tunable in wavelength comprising: a semiconductor laser which has one facet having an antireflection coating; a tunable bandpass filter for transmitting a light having a specific wavelength from wavelength components of output light out of the one facet having the antireflection coating of the semiconductor laser; and a fiber grating member for receiving the transmitted light from the tunable band pass filter and for reflecting a light of the specific wavelength. Preferably, as the fiber grating member, a compound fiber bragg grating which comprises a plurality of fiber gratings connected in series, each of which receives transmitted light from the tunable band pass filter and reflects only an individual wavelength different from one another, is used.

Tunable semiconductor laser light source

The invention provides an optocoupler having excellent characteristics whereby both polarization dependency and optical coupling loss can be minimized. A first optical fiber is formed such that an end face thereof is at a predetermined angle with the axis thereof. A first refraction index distribution lens converts light beams sent out from the first optical fiber into collimated light beams, and sends out the collimated light beams in a direction of directional cosine of the end face of the first optical fiber. A second refraction index distribution lens condenses the collimated light beams sent out from the first refraction index distribution lens. A second optical fiber is formed such that an end face thereof is at the predetermined angle with the axis thereof, and optically couples the light beams condensed by the second refraction index distribution lens on the end face thereof. Non-reflective coating is applied to the end face of the first optical fiber and the second optical fiber, respectively, and the optical fibers are disposed such that the directional cosine of the end face of first optical fiber intersects same of the second optical fiber at an angle of 180.degree..

Optocoupler

In a light receiving module of a first aspect of the invention, a transparent plate is provided therein in such a way as to be tilted so that polarized light dependency generated thereby is equal to that generated by tilting a light receiving element and moreover in a positional relationship of being perpendicular to the latter in tilting direction. As a result, even if incident light is varied in polarized state, polarized light dependencies generated by the transparent plate and the light receiving element cancel each other to restrain the polarized light dependency of the incident light as a whole. In a light receiving module according of a second aspect of the invention, the light-emitting end surface of an optical fiber is formed in the same positional relationship relative to the light receiving surface of the light receiving element as that of the transparent plate of the first aspect of the invention. As a result, it is possible to provide a light receiving module which is reduced in polarized light dependency generated by tilting the light receiving element to be less influenced by the variation of polarized state of incident light.

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Tokyo, Japan

Keisuke Asami