WO2003087898A1 - Filtre de longueur d'onde et appareil de suivi de longueur d'onde - Google Patents

Filtre de longueur d'onde et appareil de suivi de longueur d'onde Download PDF

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Publication number
WO2003087898A1
WO2003087898A1 PCT/JP2002/009173 JP0209173W WO03087898A1 WO 2003087898 A1 WO2003087898 A1 WO 2003087898A1 JP 0209173 W JP0209173 W JP 0209173W WO 03087898 A1 WO03087898 A1 WO 03087898A1
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WIPO (PCT)
Prior art keywords
optical axis
wavelength
birefringent material
angle
light
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PCT/JP2002/009173
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English (en)
Japanese (ja)
Inventor
Masao Imaki
Yoshihito Hirano
Yohei Mikami
Makoto Satoh
Akihiro Adachi
Yasunori Nisimura
Original Assignee
Mitsubishi Denki Kabushiki Kaisha
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Publication of WO2003087898A1 publication Critical patent/WO2003087898A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/28—Interference filters
    • G02B5/284—Interference filters of etalon type comprising a resonant cavity other than a thin solid film, e.g. gas, air, solid plates
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J2009/0257—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods multiple, e.g. Fabry Perot interferometer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/001—Optical devices or arrangements for the control of light using movable or deformable optical elements based on interference in an adjustable optical cavity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/0687—Stabilising the frequency of the laser

Definitions

  • the present invention relates to a wavelength finolator for selecting a wavelength of a laser beam used in a wavelength division multiplexing transmission (WDM) system and the like, and a wavelength monitor device for measuring an oscillation wavelength of the laser beam using the wavelength filter.
  • WDM wavelength division multiplexing transmission
  • FIG. 1 is a configuration diagram showing a conventional wavelength monitor device disclosed in Japanese Patent Application Laid-Open No. H03-160774.
  • a semiconductor laser 101 can control the wavelength of an emitted optical signal.
  • Light emitted from the semiconductor laser 101 is converted into parallel light by an optical lens 1.05, and the parallel light is further condensed on a photodetector 108, for example, a photodiode.
  • the other light is incident on the Fabry-Perot resonator.
  • the Fabry-Perot resonator 111 is branched in two directions by a reflection film 109 and a beam splitter 106.
  • One of the branched lights passes through a lens 107, has 110, and is formed of two types of optical materials.
  • the light transmitted through the Fabry-Perot resonator 111 is focused on the photodetector 113 via the lens 112.
  • FIG. 2 is a configuration diagram of the Fabry-Perot resonator 111 in FIG.
  • the temperature coefficient ⁇ of a Fabry-Perot resonator made of one type of optical material is expressed by equation (1).
  • ⁇ is the refractive index of the optical material
  • ⁇ is the net tension coefficient in the optical axis direction.
  • a generally known Fabry-Perot resonator uses a glass material. In that case, the temperature coefficient (thermo-optical coefficient) of the linear expansion coefficient ⁇ and the refractive index n was fixed. Therefore, the temperature coefficient ⁇ is uniquely determined.
  • the cavity length of the Fabry-Perot resonator 111 does not change in accordance with the temperature, but is emitted from the semiconductor laser 101 and transmitted through the Fabry-Perot resonator 111. Since the wavelength dependence of the light intensity does not change, the wavelength can be accurately monitored irrespective of the temperature of the resonator 111.
  • the Fabry-Perot resonator 111 is composed of two types of optical materials having different signs of the temperature coefficient ⁇ . Equation (2) must be satisfied in order to make the temperature coefficient of the entire Fabry-Perot resonator 1 1 1 zero.
  • n 0 and 101 are the refractive index and physical length of the first optical material, respectively, and r x is the first optical material. This is the temperature coefficient according to equation (1). Also n. 2, 1 02 the refractive index and physical length of the second optical material, respectively it, r 2 is Ru temperature coefficient der of the second optical material.
  • quartz was used as the optical material with a positive temperature coefficient
  • rutile was used as the optical material with a negative temperature coefficient.
  • ⁇ 01 , 101 are the refractive index and physical length of quartz, ⁇ .
  • Two , one. 2 is the refractive index and physical length of Lutheran.
  • a Fabry-Perot resonator in which the resonator length does not change with temperature is configured by using two optical materials having different signs of the temperature coefficient.
  • the present invention has been made in view of the above, and comprises a Fabry-Perot resonator (wavelength filter) whose resonator length does not change in response to a temperature change using a birefringent crystal, whereby the configuration is simplified, It is an object of the present invention to obtain a wavelength filter capable of realizing mass production and a wavelength monitor provided with the wavelength filter.
  • Fabry-Perot resonator wavelength filter
  • the present invention includes a wavelength filter capable of freely setting a temperature characteristic of a wavelength filter, and selecting an arbitrary wavelength characteristic by changing a temperature of the wavelength filter, and the wavelength filter. The purpose is to obtain a wavelength monitor.
  • a wavelength filter according to the present invention resonates light between a solid material that transmits light, a substantially parallel opposing plane formed on the solid material, and the substantially parallel opposing plane.
  • the solid material is a birefringent material, and an optical axis thereof has a predetermined angle with a normal to a plane substantially parallel to the birefringent material. I do.
  • a birefringent material having a predetermined angle with respect to a normal to a plane whose optical axes are substantially parallel to each other is used, and by changing the angle, the temperature characteristic of the wavelength filter is changed.
  • the temperature coefficient of the optical path length between the planes has a predetermined value, wherein the predetermined angle between the normal line of the substantially parallel opposing plane and the optical axis has a predetermined value.
  • the temperature coefficient of the optical path length between the planes is set to have a predetermined value, it is possible to easily and accurately adjust the wavelength characteristics by changing the temperature, Adjustment to the grid is also facilitated.
  • the birefringent materials face each other substantially in parallel so that the absolute value of the sum of the product of the refractive index and the linear expansion coefficient in the optical axis direction and the thermo-optic coefficient is minimized.
  • the angle between the optical axis and the normal to the plane to be set is set.
  • the temperature characteristic can be suppressed to a sufficiently low value, and a wavelength filter having a temperature compensation function can be provided. Therefore, the configuration of the wavelength filter is simplified, the reliability of the wavelength filter is improved, and a troublesome adjustment operation is not required at the time of production, so that mass production can be realized.
  • the birefringent material comprises a product of a product of a linear expansion coefficient in a direction parallel to the optical axis and a refractive index of light propagating parallel to the optical axis, and light propagating parallel to the optical axis.
  • the product of the linear expansion coefficient in the direction perpendicular to the optical axis and the refractive index of light propagating in the direction perpendicular to the optical axis, and the thermo-optics of light propagating in the direction perpendicular to the optical axis The sum of the coefficients is different from each other.
  • the present invention while the angle formed by the optical axis with the normal to the plane is changed by 0 to 90 degrees, there is a predetermined angle at which the temperature characteristic becomes zero, and the angle has a characteristic of zero.
  • a wavelength filter having a temperature compensation function can be provided. Therefore, the configuration of the wavelength filter is simplified, the reliability as the wavelength filter is improved, and troublesome adjustment work is not required at the time of production, so that mass production can be realized.
  • the birefringent material is alpha-BBO crystal,] 3 - wherein beta beta Omicron crystal, L i I 0 3 crystals, that is either C a C 0 3 crystals And
  • c one ⁇ ⁇ ⁇ , - BBO, L i I 0 3, C a CO in the case of using any of 3, a wavelength having a temperature compensation function of the precision A filter can be realized.
  • light incident on the birefringent material uses polarized light aligned with the extraordinary optical axis, and when the birefringent material is an ⁇ -BBO crystal, an angle of the optical axis with respect to the optical axis.
  • the angle of the optic axis to the optical axis is about 65 degrees
  • the angle to the optical axis is The angle is about 23 degrees.
  • the polarization of light incident on the extraordinary optical axis is made uniform, and when any of ⁇ - ⁇ ,] 3-BBO, and Li IO 3 is used as a birefringent material, high accuracy is achieved.
  • a wavelength filter having a temperature compensation function can be realized.
  • the light incident on the birefringent material uses polarized light aligned with the ordinary optical axis, and when the birefringent material is an ⁇ -BBO crystal, the angle of the optical axis with respect to the optical axis is changed.
  • the birefringent material is a 3 / 3- ⁇ crystal
  • the angle of the optic axis to the optical axis is about 57 degrees.
  • the optical axis is the optic axis. angle of about 19 degrees with respect to the birefringent material in the case of C a C0 3 crystal, characterized by an angle of about 66 degrees with respect to the optical axis of the optical axes.
  • a wavelength monitoring device is a wavelength monitoring device that monitors the wavelength of laser light output from a semiconductor laser, comprising: a solid material that transmits laser light; and a substantially parallel opposed flat surface formed on the solid material.
  • a wavelength filter that resonates laser light between the substantially parallel opposing planes, and periodically selects a wavelength determined by an optical path length between the opposing planes; and
  • the solid-state material is a birefringent material, and an optical axis thereof has a predetermined angle with a normal line of the substantially parallel opposing plane.
  • the wavelength filter is formed using a birefringent material having a predetermined angle with respect to a normal to a plane whose optical axes are substantially parallel to each other.
  • the laser light output from the semiconductor laser is polarized in one direction
  • the birefringent material forming the wavelength filter is:
  • the optical axis is in a plane parallel to a plane formed by the directions, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
  • the present invention it is possible to realize a wavelength monitor having a wavelength filter in which the polarization of light incident on the extraordinary optical axis is uniform and which can select an arbitrary wavelength characteristic by changing the temperature. it can.
  • the laser light output from the semiconductor laser is polarized in one direction
  • the birefringent material forming the wavelength filter is:
  • the optical axis lies in a plane perpendicular to the plane formed by the directions, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
  • a wavelength monitor having a wavelength filter capable of selecting an arbitrary wavelength characteristic by changing the temperature by aligning the polarization of light incident on the ordinary optical axis. it can.
  • the birefringent material constituting the wavelength filter is configured such that an angle of the optical axis with respect to the optical axis is set based on a refractive index of a crystal, a linear expansion coefficient in an optical axis direction, and a thermo-optic coefficient. It is characterized by having.
  • the birefringent crystal in which the angle of the optical axis with respect to the optical axis is set based on the refractive index, the coefficient of linear expansion in the optical axis direction, and the thermo-optic coefficient, the birefringent crystal is used.
  • a highly reliable wavelength monitor having a wavelength filter having a temperature compensation function can be realized.
  • the next invention is the above-mentioned invention, wherein the normal and the optical axis of the plane substantially parallel
  • the predetermined angle with the axis is set such that the temperature coefficient of the optical path length between the planes has a predetermined value.
  • the temperature coefficient of the optical path length between the planes is set to have a predetermined value, it is possible to easily and accurately adjust the wavelength characteristics by changing the temperature, Adjustment to the grid is also easy.
  • the birefringent materials face each other substantially in parallel so that the absolute value of the sum of the product of the refractive index and the linear expansion coefficient in the optical axis direction and the thermo-optic coefficient is minimized.
  • the angle between the optical axis and the normal to the plane to be set is set.
  • the temperature characteristic of the wavelength filter can be suppressed to a sufficiently low value, so that the configuration is simplified, the reliability as a wavelength monitor is improved, and a troublesome adjustment operation is not performed during production. And mass production can be realized.
  • the birefringent material comprises a product of a product of a linear expansion coefficient in a direction parallel to the optical axis and a refractive index of light propagating parallel to the optical axis, and light propagating parallel to the optical axis.
  • the product of the tension coefficient in the direction perpendicular to the optical axis and the refractive index of the light propagating in the direction perpendicular to the optical axis are different from each other.
  • the wavelength filter has a temperature compensation function, which simplifies the configuration and improves the reliability as a wavelength monitor. At the same time, there is no need for troublesome adjustment work during production, and mass production can be realized.
  • the birefringent material in the above invention, the birefringent material, and wherein the alpha-BBO crystal, beta one beta beta Omicron crystal, L i I 0 3 crystals are either C a C 0 3 crystals I do.
  • the light incident on the birefringent material uses polarized light aligned with the extraordinary optical axis
  • the angle of the optical axis with respect to the optical axis is about and 64 degrees, in the case of the birefringent material is 3- ⁇ crystals, and an angle of about 65 degrees with respect to the optical axis of the optical axis, if the birefringent material is a L i I 0 3, the angle with respect to the optical axis of the optical axis It is characterized by about 23 degrees.
  • the polarization of light incident on the extraordinary optical axis is made uniform, and when any of a-BBO,] 3-BBO, and Li IO 3 is used as a birefringent material, high-precision A wavelength monitor having a wavelength filter having a temperature compensation function can be realized.
  • the light incident on the birefringent material uses polarized light aligned with the ordinary optical axis, and when the birefringent material is an ⁇ -BBO crystal, the angle of the optical axis with respect to the optical axis is changed.
  • the birefringent material is / 3- BBO crystal, and the angle of about 57 degrees against the optical axis of the optical axis, if the birefringent material is a L i I 0 3 crystal, the light of the optical axis an angle relative to the axis of about 19 degrees, the birefringent material in the case of C a C0 3 crystal, characterized by an angle of about 66 degrees with respect to the optical axis of the optical axes.
  • the birefringent material constituting the wavelength filter is optically controlled so that a sum of a product of a refractive index and a linear expansion coefficient in an optical axis direction and a thermo-optic coefficient are equal to zero.
  • the angle of the axis with respect to the optical axis is set.
  • the optical product when the polarization of the laser beam is aligned with the extraordinary optical axis, the optical product is set so that the sum of the product of the refractive index and the linear expansion coefficient in the direction of the optical axis and the thermo-optic coefficient is equal to zero. Since a uniaxial birefringent crystal whose angle is set with respect to the optical axis is used, high-precision temperature A wavelength monitor having a wavelength filter having a degree compensation function can be realized.
  • the birefringent material constituting the wavelength filter is any one of ⁇ - ⁇ ,] 3—BBO and L i IO 3.
  • the birefringent material is ⁇ —BBO
  • the angle of the optical axis with respect to the optical axis is 63.35 degrees
  • the birefringent material is] 3—In the case of BBO, the angle of the optical axis with respect to the optical axis is 64.75 degrees
  • the birefringent material is L i I 0 3 In this case, the angle of the optical axis with respect to the optical axis is 22.70 degrees.
  • the birefringent material forming the wavelength filter alpha-BBO, one BBO, either as L i L0 3, C a C0 3, the birefringent material is alpha-BBO of
  • the angle of the optical axis with respect to the optical axis is 76.95 degrees
  • the birefringent material is 0— ⁇
  • the angle of the optical axis with respect to the optical axis is 57.05 degrees
  • the birefringent material is L i L0 3 for the angle with respect to the optical axis of the optical axis is 18.65 degrees
  • a wavelength monitor having a wavelength filter having a high-precision temperature compensation function can be realized.
  • the birefringent material constituting the wavelength filter in the above invention satisfies the temperature compensation condition by changing the thickness in the optical axis direction while maintaining the set angle with respect to the optical axis. And the wavelength discrimination region can be adjusted.
  • the temperature compensation condition does not depend on the thickness of the birefringent crystal. It is possible to obtain a wavelength filter having an arbitrary wavelength discrimination region satisfying the adjustment condition.
  • the next invention is characterized in that, in the above invention, there is provided a lens for adjusting a beam size of laser light emitted from the semiconductor laser, and outputting the adjusted laser light to the wavelength filter.
  • the present invention it is possible to adjust the beam size of the laser light and make it incident on the wavelength filter.
  • the wavelength detecting means comprises: a first photodetector for detecting light transmitted through the wavelength filter; and a second light for directly detecting laser light output from the semiconductor laser. It is characterized by comprising a detector and a wavelength detector for detecting the oscillation wavelength of the laser light using the ratio of the detection signals of the first and second photodetectors.
  • the oscillation wavelength of the laser light is detected using the ratio of the detection signals of the first and second photodetectors, the laser light is not affected by a change in the output intensity of the semiconductor laser.
  • the oscillation wavelength can be accurately detected.
  • the semiconductor laser and the wavelength filter are mounted, and the first and second optical detectors are arranged such that the second photodetector is located above the first photodetector.
  • a base scanner for installing a photodetector is further provided, wherein the height of the wavelength filter is adjusted so that the laser light transmitted through the wavelength filter mounted on the base carrier is not received by the second photodetector. It is characterized by
  • the laser light transmitted through the wavelength filter is not received by the second photodetector, and the oscillation wavelength can be accurately detected.
  • the semiconductor laser and the wavelength filter are mounted, and the first and second optical detectors are arranged such that the second photodetector is located above the first photodetector.
  • the second photodetector is arranged closer to the wavelength filter side than the first photodetector so as not to be received by the detector.
  • the laser light transmitted through the wavelength filter is not received by the second photodetector, and the oscillation wavelength can be accurately detected.
  • the following invention is the wavelength monitoring device for monitoring the wavelength of the laser light output from the semiconductor laser in the above invention, wherein the first solid material transmitting the laser light; and the first solid material formed on the first solid material.
  • a laser beam is resonated between a substantially parallel opposing plane and the substantially parallel opposing plane to periodically select a wavelength determined by an optical path length between the opposing planes, and the solid material is a birefringent material.
  • the laser light is resonated between a substantially parallel opposed plane formed on the substrate and the substantially parallel opposed plane, and a wavelength determined by an optical path length between the opposed planes is periodically selected, and the solid material is birefringent.
  • a wavelength detecting means for measuring is
  • the configuration is simplified, the reliability as a wavelength monitor is improved, and troublesome adjustment work does not have to be performed during production, and mass production can be realized.
  • the oscillation wavelength of the laser beam is monitored using two wavelength filters for the narrow band and the broad band, so that the oscillation wavelength can be detected very accurately.
  • the laser light output from the semiconductor laser is polarized in one direction
  • the birefringent material constituting the first and second wavelength filters is An optical axis is in a plane parallel to a plane formed by the optical axis and the polarization direction of the laser light, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser light. I do.
  • the laser light output from the semiconductor laser is polarized in one direction
  • the birefringent material forming the wavelength filter is:
  • the optical axis lies in a plane perpendicular to the plane formed by the directions, and the optical axis is inclined at a predetermined angle with respect to the optical axis of the laser beam.
  • the present invention it is possible to realize a wavelength monitor having two wavelength filters having a temperature compensation function by using a birefringent crystal in which the polarization of laser light is aligned with the ordinary optical axis.
  • the wavelength discrimination region of the second wavelength filter for the wide band is larger than the wavelength variable region of the semiconductor laser, and the wavelength discrimination region of the first wavelength filter for the narrow band is the second wavelength filter.
  • the thickness of the birefringent material constituting the first and second wavelength filters in the optical axis direction is set so as to be sufficiently smaller than the wavelength variable region of the first wavelength filter.
  • the two wavelength filters for the narrow band and the wide band are configured by setting the thickness of the birefringent crystal in the optical axis direction, and the two wavelength filters for the narrow band and the wide band are simply provided. Can be realized.
  • the wavelength detecting means directly detects laser light output from the semiconductor laser, and a first photodetector for detecting transmitted light of the first wavelength filter.
  • the oscillation wavelength of the laser light is detected using the ratio of the detection signals of the first and second photodetectors and the ratio of the detection signals of the third and second photodetectors.
  • the oscillation wavelength can be extremely accurately detected without being affected by a change in the output intensity of the semiconductor laser.
  • the semiconductor laser and the wavelength filter are mounted, and the first to third light detectors are arranged such that the second and third photodetectors are located above the first photodetector.
  • the third photodetector is disposed closer to the wavelength filter than the first photodetector. According to the present invention, the laser light transmitted through the wavelength filter is not received by the second and third optical detectors, and the oscillation wavelength can be accurately detected.
  • FIG. 1 is a configuration diagram of a conventional wavelength monitoring device
  • FIG. 2 is a perspective view showing a conventional Fabry-Perot resonator
  • FIG. 3 is a configuration diagram of a wavelength monitoring device in the first embodiment.
  • Fig. 4 is a graph showing the change in the transmittance of a Fabry-Perot resonator (wavelength filter) with respect to the wavelength.
  • Fig. 5 shows a Fabry-Perot resonator (wavelength filter) using a uniaxial birefringent crystal.
  • FIG. 6 is a diagram showing the physical property values of the - ⁇ crystal
  • FIG. 6 is a diagram showing the physical property values of the - ⁇ crystal
  • FIG. 7 is a graph showing the dependence of the dn / d ⁇ + ⁇ of the 3-3- ⁇ crystal on the temperature ⁇ .
  • Fig. 8 is a graph showing the dependence of the linear expansion coefficient ⁇ of the / 3- ⁇ ⁇ ⁇ crystal on the C-axis-to-optical axis angle ⁇ i> c.
  • FIG. 10 is a graph showing the dependence of the extraordinary refractive index n on the angle ⁇ between the C axis and the optical axis.
  • FIG. 10 shows the temperature of the extraordinary refractive index of the] 3-BBO crystal.
  • FIG. 11 is a graph showing temperature characteristics of i3-— crystal with respect to ⁇ c
  • FIG. 12 is a graph showing temperature characteristics of C a ⁇ 3 crystal with respect to ⁇ c
  • the FIG. 13 is a diagram showing a temperature characteristic with respect to phi c of L i I 0 3 crystal
  • Fig. 14 shed - is a view to view the temperature characteristics for phi c of the BBO crystal
  • FIG. 16 is a configuration diagram illustrating a wavelength control device according to the first embodiment
  • FIG. 17 is a configuration diagram illustrating a modification of the wavelength monitor device according to the first embodiment.
  • FIG. 16 is a configuration diagram illustrating a wavelength control device according to the first embodiment
  • FIG. 17 is a configuration diagram illustrating a modification of the wavelength monitor device according to the first embodiment.
  • FIG. 18 is a configuration diagram of a wavelength monitor device according to the second embodiment
  • FIG. 19 is a configuration diagram of a wavelength control device according to the second embodiment
  • FIG. 20 is a Fabry-Perot for a narrow band.
  • FIG. 21 is a graph showing the wavelength transmission characteristics of a resonator (wavelength filter) and a Fabry-Perot resonator (wavelength filter) for a wide band.
  • FIG. 21 is a configuration diagram showing a modification of the wavelength monitor device according to the second embodiment. It is. BEST MODE FOR CARRYING OUT THE INVENTION
  • FIG. 3 is a configuration diagram showing a wavelength monitoring device (a certain wavelength is a wavelength stabilized light source) according to Embodiment 1 of the present invention.
  • the semiconductor laser 1 emits laser light (hereinafter referred to as an optical signal) polarized in one direction.
  • Examples of the semiconductor laser 1 include a distributed feedback (DFB) laser having a diffraction grating in an active layer, a tunable laser diode whose wavelength can be changed by injection current or temperature, or an electroabsorption element and a laser diode.
  • a compound type (EA / LD) module in which the components are arranged in series.
  • the injection current or the temperature of the semiconductor laser 1 is controlled by the control signal T1 input from the wavelength control device shown in FIG. 16 to control the wavelength.
  • An optical signal emitted from the semiconductor laser 1 is condensed by the lens 2 and output as parallel light.
  • the beam size of the optical signal is adjusted by the lens 2 and the light signal is incident on a Fabry-Perot resonator 3 as a wavelength filter.
  • the axis connecting the center of the emitting surface of the semiconductor laser 1 and the center of the lens 2 is the optical axis.
  • the traveling direction (optical axis direction) of an optical signal is defined as the Z-axis direction in space coordinates, and the upward direction in space is defined as the Y-axis direction.
  • the direction perpendicular to the Y-axis (the direction perpendicular to the page in Fig. 3 and facing the front) is defined as the X-axis.
  • Semiconduct The optical signal emitted from the body laser 1 has a polarization component that vibrates in the X-axis direction.
  • the Fabry-Perot resonator (wavelength filter) 3 has reflection films 7 and 8 that reflect light on an incident surface on which an optical signal from the semiconductor laser 1 is incident and an exit surface on which the optical signal is emitted, and one kind of material is used.
  • first material e.g., / 3 - BBO crystal, alpha - BBO crystal, L i IO 3 crystal, any such C a CO 3 crystals
  • first material e.g., / 3 - BBO crystal, alpha - BBO crystal, L i IO 3 crystal, any such C a CO 3 crystals
  • the crystal cut surface of the uniaxial birefringent crystal used as the material of the Fabry-Perot resonator 3 is arranged so as to be parallel to the XY plane orthogonal to the optical axis, and the optical axis of the uniaxial birefringent crystal (hereinafter referred to as the C axis) ) Is inclined at a predetermined angle with respect to the XY plane perpendicular to the optical axis of the laser beam.
  • the first photodiode (main photodetector) 4 receives the optical signal transmitted through the Fabry-Perot resonator 3, detects its intensity (photocurrent value), and outputs a light intensity monitor signal S1.
  • the second photodiode (sub-photodetector) 5 is disposed above the first photodiode 4 and directly receives an optical signal emitted from the semiconductor laser 1 without passing through the Fabry-Perot cavity 3 and receiving the light signal. Detects light intensity (photocurrent value) and outputs light intensity monitor signal S2.
  • These semiconductor laser 1, lens 2, Fabry-Perot cavity 3, first photodiode 4, and second photodiode 5 are mounted on base carrier 6.
  • the height of the Fabry-Perot resonator 3 or the height of the second photodiode 5 is set so that the optical signal transmitted through the Fabry-Perot resonator 3 is not received by the second photodiode 5. Has been adjusted.
  • the transmission characteristics with respect to the wavelength of the optical signal transmitted through the Fabry-Perot resonator 3 are kept constant irrespective of the temperature change. That is, the Fabry-Perot resonator 3 has a temperature compensation function. Next, the temperature compensation condition of the Fabry-Perot resonator 3 will be described.
  • an optical signal is vertically incident on the incident surface of the rectangular Fabry-Perot resonator 3.
  • the Fabry-Bore-One resonator 3 Assuming that the emission surfaces have reflection films 7 and 8 and their intensity reflectivity is R, the dependence of the intensity of the optical signal transmitted through the Fabry-Bore-One resonator 3 on the wavelength is expressed by Equation (3) and FIG. Is done.
  • TR (E) is the transmittance.
  • the intensity of the optical signal transmitted through the Fabry-Perot resonator 3 changes periodically with respect to the frequency of the optical signal.
  • the frequency interval corresponding to one cycle is called a free spectrum range (hereinafter, referred to as FSR, free spectral interval) with respect to the wavelength of the optical signal transmitted through the Fabry-Perot resonator 3.
  • FSR free spectrum range
  • the FSR depends on the resonator length in the direction of the optical axis, in the case of FIG. 3, the length L in the Z-axis direction of the uniaxial birefringent crystal 3 and the refractive index n, and is expressed by the following equation (4).
  • . c is the speed of light.
  • the compensation condition for the Fabry-Perot single resonator is that the dependence of the intensity of the optical signal transmitted through the 2nL Fabry-Perot resonator 3 on the wavelength does not change with temperature. Therefore, in order to enable temperature compensation, it is necessary that F SR represented by equation (4) does not depend on temperature. In order for F SR to be constant with respect to temperature T, it is necessary that the resonator length n L has a constant value with respect to temperature T in equation (4). Equation (5) expresses this relationship.
  • the temperature compensation condition can be satisfied even when the polarization direction of the laser beam (in this case, the X direction) is aligned with the extraordinary optical axis or the ordinary optical axis of the uniaxial birefringent crystal.
  • the polarization direction of the light is aligned with the extraordinary optical axis of the uniaxial birefringent crystal.
  • the C axis of the uniaxial birefringent crystal which is the material of the Fabry-Perot resonator, is in the XZ plane, the optical axis is parallel to the Z axis, and the C axis is at a constant angle to the optical axis.
  • ⁇ c is inclined.
  • the polarization of the optical signal incident on the Fabry-Perot resonator 3 is p-polarized with respect to the Fabry-Perot resonator 3, and corresponds to the X direction in FIG.
  • the extraordinary ray Since the extraordinary ray has the same vibration plane as the plane created by the C axis and the optical axis direction, in this case, the incident optical signal propagates inside the Fabry-Perot resonator 3 as an extraordinary ray.
  • the refractive index n for an extraordinary ray depends on the angle between the optical axis and the C axis. Since ne and no depend on the temperature T, they can be expressed as n (0c, T), as shown in equation (8). .
  • ne is the refractive index for the polarized light component in the direction parallel to the C axis (the extraordinary light refractive index), and no is the refractive index for the polarized light component in the direction perpendicular to the C axis (the ordinary light refractive index).
  • ⁇ ( ⁇ ) is the refractive index for an optical signal incident on a Fabry-Bore-single resonator made of a uniaxial birefringent crystal.
  • the linear expansion coefficient ⁇ in the optical axis direction of a uniaxial birefringent crystal is expressed as in equation (9).
  • ac is the coefficient of linear expansion in the direction parallel to the C axis
  • aa is the coefficient of linear expansion in the direction perpendicular to the C axis.
  • the temperature characteristic of the wavelength characteristic shown in FIG. 4 can be expressed by the formula (1) for the extraordinary optical axis direction and the ordinary optical axis direction. 0), and is expressed by equation (11).
  • the inventors of the present application have made it possible for the uniaxial birefringent crystal studied as a material of the Fabry-Perot resonator to change the value of the inclination ⁇ c of the C axis with respect to the optical axis.
  • the uniaxial birefringent crystal satisfying the equation (7) and the value of ⁇ c in that case were examined.
  • 13-B BO (B a B 2 0 4) crystals, such as alpha-BBO crystal, L i I 0 3, C a C0 3 was found to satisfy the equation (7). These crystals are used as wavelength conversion elements for laser light.
  • Fig. 6 shows the characteristics of] 3-BBO crystal. That is,]] — BBO has an extraordinary refractive index ne of 1.53 11 1, an ordinary refractive index no of 1.6467, and a thermo-optic coefficient d no / dT of — 16.8 X 10 0 6 / in K, thermo-optical coefficient d ne / d T - 8. 8 X 1 0 one 6 / a, coefficient of linear expansion etc is 3 3. 3 X 1 0- K, the linear expansion coefficient ca is 0. 5 X 1
  • Fig. 7 shows that 3 ⁇ / 3 shown in equation (7) when a uniaxial birefringent crystal composed of BBO is used as the Fabry-Perot resonator 3 and the polarization direction of the laser beam is aligned with the extraordinary optical axis.
  • T + eta alpha a graph showing the relationship between the optical axis and the C axis and the angle phi c.
  • Fig. 8 is a graph showing the dependence of the coefficient of linear expansion ⁇ on the angle ⁇ c in a ⁇ crystal
  • Fig. 9 is a graph showing the dependence of the refractive index ⁇ on the angle ⁇ c in a ⁇ crystal.
  • FIG. 10 is a graph showing the dependence of dn / dT on the angle ⁇ c in a / 3--3 crystal. That is, the relationship between the linear expansion coefficient ⁇ and the angle ⁇ f> c in FIG. 8, the relationship between the refractive index n and the angle ⁇ c in FIG. 9, and the relationship between dn / dT and the angle ( ⁇ > Using the relationship with c, the relationship between 3 ⁇ / 3 ⁇ + ⁇ ⁇ and the angle ⁇ c shown in FIG. 7 is obtained.
  • Fig. 11 shows the relationship between ⁇ c and temperature characteristics in the direction of the extraordinary optical axis and the direction of the ordinary optical axis when / 3-BBO is used as the uniaxial birefringent crystal. 1 This is a graph using 1).
  • the extraordinary optical axis direction is from 18 pmZ ° C to +36 pm / ° C
  • the ordinary optical axis direction is from 15 pmZ ° C by changing c.
  • Temperature characteristics can be freely set up to +36 pmZ ° C.
  • the temperature characteristic becomes zero when ⁇ c is between 0 and 90 degrees because of the relationship of (1 11/3 cho + hi ( : 11) 0 bracket (111 01 cho + « ! 1 11 ⁇ 0 ⁇
  • ⁇ c should be about 63 It may be set to any value between ⁇ 67 degrees. If the temperature characteristic is to be set to ⁇ 1 pm or less using the direction of the extraordinary optical axis, c may be set to any value of about 55 to 59 degrees.
  • the wavelength characteristics can be adjusted using the temperature characteristics.
  • the wavelength characteristics are usually changed by tilting the filter, but the temperature of the filter (uniaxial birefringent crystal) is changed using the above characteristics. By doing so, it is possible to match the wavelength control point.
  • temperature characteristic is 10 pm.
  • any lock point can be used with a maximum filter temperature change of 20 ° C.
  • the ITU grid is a set of closely spaced wavelengths in a specific wavelength region specified by the International Telecommunication Union, for example, a window of 1550 nm. Corresponds to a wavelength interval of about 0.8 nm.
  • the coefficient of linear expansion c is 2.44 X 10-6 / ⁇ .
  • the extraordinary optical axis direction is from +4 pm / ° C to +40 pmZ ° C
  • the ordinary optical axis direction is from 17 pm / ° C to +40 pmZ ° C.
  • Temperature characteristics can be freely set up to this point.
  • ⁇ c may be set to any value of about 65 to 70 degrees.
  • ⁇ c 90 degrees may be set.
  • the wavelength characteristics can be adjusted using the temperature characteristics. I TU grid wave
  • the wavelength characteristic is usually changed by tilting the filter.
  • the temperature coefficient d ⁇ eZdT of the refractive index in the direction of the extraordinary optical axis is — 6.92 X 10 — 5 / K
  • the linear expansion coefficient aa is 2.80 X 10 — 5 Z
  • the linear expansion coefficient ac Is 4.80 X 10-1 5 ZK.
  • the direction of the extraordinary optical axis is from 20 pmZ ° C to +3 pmZ ° C
  • the direction of the ordinary optical axis is ⁇ 28 pmZ ° C to +3 pm, °.
  • Temperature characteristics can be freely set up to C.
  • ⁇ c In both the normal optical axis and the extraordinary optical axis, there is a relationship of dn / dT + a e n> 0 and d nZdT + a n a 0, so that the temperature characteristic becomes zero when 0 c is between 0 and 90 degrees. c exists. For example, if you want the temperature characteristics to be less than 1 pm_ ° C in soil using the direction of the ordinary optical axis, you can set ⁇ c to any value from about 15 to 22 degrees. If the temperature characteristic is to be 1 pm / ° C or less using the direction of the abnormal optical axis, ⁇ c should be set to any value of about 18 to 27 degrees. The wavelength characteristics can be adjusted using the temperature characteristics.
  • the wavelength characteristic is usually changed by tilting the filter, but by changing the temperature of the filter using the above characteristics, the wavelength control point can be adjusted.
  • Fig. 14 shows the relationship between ⁇ c and temperature characteristics in the extraordinary optical axis direction and the ordinary optical axis direction when ⁇ -BBO is used as the uniaxial birefringent crystal, using equations (10) and (11). It is graphed using.
  • the physical constants used were: extraordinary refractive index ne was 1.530, ordinary refractive index no was 1.6502, and temperature coefficient of refractive index in the ordinary optical axis direction was dn oZd T was 9.30 x in 1 0- 5 / K, abnormal temperature coefficient of the optical axis of the refractive index dne / d T one 1 6. 6 X 1 0- 5 / K, the linear expansion coefficient aa 4. 0 X 1 0- 5 / in K, the linear expansion coefficient ac is 3 6. 0 X 1 0 one 5. According to FIG.
  • ⁇ c may be set to any value of about 74 to 80 degrees.
  • ⁇ c may be set to any value of about 63 to 66 degrees.
  • the wavelength characteristics can be adjusted using the temperature characteristics.
  • the wavelength characteristics are usually changed by tilting the filter.However, the temperature is adjusted to the wavelength control point by changing the temperature of the filter using the above characteristics. .
  • the temperature compensation condition equation (7) is satisfied.
  • the FSR 100 GHz (1.0 X 10 X 1 Hz) corresponding to a wavelength fluctuation width of 0.8 nm of laser light.
  • the temperature compensation condition equation (7) does not depend on the length L of the uniaxial birefringent crystal in the ⁇ -axis direction when the uniaxial birefringent crystal is used as the Fabry-Perot resonator 3, so that from equation (4) A Fabry-Perot resonator with any FSR that satisfies the temperature compensation conditions can be made.
  • An optical signal emitted from the semiconductor laser 1 is collected by the lens 2.
  • the upper part of the collected optical signal is directly received by the second photodiode 5.
  • the second photodiode 5 detects and monitors the intensity of the received optical signal.
  • An output control circuit (not shown) controls the optical output of the semiconductor laser 1 to be constant based on the difference between the intensity monitor signal S2 and a preset optical signal intensity.
  • the intensity of the optical signal emitted from the Fabry-Perot resonator 3 has a wavelength discrimination characteristic as shown in equation (3), and the characteristic is kept constant regardless of the crystal temperature change. Has temperature compensation function.
  • ⁇ 64.75 is set, but the temperature characteristics can be sufficiently suppressed if the angle is around this.
  • the temperature characteristic is 1 pm / ° C for soil, which is sufficiently smaller than the temperature characteristic of a conventional solid ethanol port (up to 10 pm / ° C).
  • the temperature coefficient can be arbitrarily set as long as the extraordinary optical axis direction is between 18 pmZ ° C and +36 pmZ ° C, and the normal optical axis direction is between 15 pmZ ° C and +36 pm. You can choose. This makes it possible to adjust the wavelength characteristics by changing the temperature, which facilitates adjustment to the ITU grid.
  • FSR 25 GHz
  • ⁇ c is set so that the temperature characteristic is 8 pmZ ° C.
  • the temperature of the uniaxial birefringent crystal 3 is changed by 1 ° C. Therefore, when trying to match the ITU grid with 25 GHz spacing to the wavelength control point specified in advance, the temperature of the base carrier 6 on which the semiconductor laser 1 is mounted is changed by up to 25 degrees and the semiconductor laser is changed.
  • the oscillation wavelength by adjusting the injection current to 1, it is possible to adjust to the desired wavelength control point.
  • the first photodiode 4 detects the intensity of an optical signal that has passed through the Fabry-Perot resonator 3, and outputs an optical intensity monitor signal S1.
  • the second photodiode 5 directly detects the optical signal intensity emitted from the semiconductor laser 1 and outputs the optical intensity monitor signal S2, as described above.
  • These light intensity monitor signals S 1 and S 2 are It is sent to the wavelength controller 50 shown in the figure.
  • the wavelength controller 50 detects the wavelength of the optical signal, and controls the semiconductor laser 1 so that the detected wavelength matches a preset wavelength (for example, the reference wavelength; I 0 in FIG. 4).
  • FIG. 16 is a configuration diagram of the wavelength control device 50.
  • the wavelength controller 50 includes a wavelength detector 51 and a laser controller 52.
  • the wavelength detector 51 receives the light intensity monitor signals S1, S2 from the first and second photodiodes and a preset reference wavelength 0.
  • the wavelength detector 51 obtains the oscillation wavelength of the optical signal emitted from the semiconductor laser 1 based on the light intensity monitor signals S1 and S2, and obtains the difference between the oscillation wavelength and the reference wavelength I0.
  • the difference between the reference wavelength ⁇ 0 from the wavelength detector 51 and the oscillation wavelength emitted from the semiconductor laser 1 is input to the laser controller 52.
  • the laser control unit 52 obtains a control signal ⁇ 1 for controlling the temperature, injection current, and the like of the semiconductor laser 1 so that the oscillation wavelength coincides with the reference wavelength 0 according to the difference. 1 is output to the semiconductor laser 1.
  • FIG. 4 A case where the oscillation wavelength is adjusted to the reference wavelength ⁇ 0 in FIG. 4 will be described.
  • the value of the light intensity monitor signal S 1 detected by the first photodiode 4 is such that the wavelength of the optical signal is longer than the wavelength. It can be seen that it becomes smaller when it shifts to, and increases when it shifts to the shorter wavelength side.
  • the change in the light intensity monitor signal S1 accompanying the change in the wavelength is monitored, and the deviation from the reference wavelength; L0 is calculated.
  • the light intensity monitor signal S 2 that directly detects the optical signal emitted from the semiconductor laser 1 and the light intensity monitor signal S 1 that detects the optical signal transmitted through the Fabry-Perot resonator 3 are the semiconductor laser 1 It changes in proportion to the intensity of the emitted optical signal.
  • the wavelength of the optical signal emitted from the semiconductor laser 1 includes ⁇ 0 If it is within the slope, the value of the signal intensity ratio S1 / S2 will represent the wavelength of the optical signal.
  • the stored signal intensity ratio S 1 / S 2 at the reference wavelength ⁇ 0 and the light intensity monitor signals S 1, S 2 from the first and second photodiodes 4 and 5 are output.
  • the difference (deviation) between the oscillation wavelength and the reference wavelength; L0 is calculated by calculating the difference between the signal intensity ratio S1 / S2 obtained based on the above.
  • the calculated deviation signal is input to the laser control unit 52.
  • the laser controller 52 uses the deviation signal input from the wavelength detector 51 to output a control signal ⁇ 1 for changing the value of the temperature or the injection current to the semiconductor laser 1.
  • the wavelength of light is the wavelength of light.
  • the oscillation wavelength of the semiconductor laser 1 becomes longer.
  • the laser control unit 52 receives the deviation signal from the wavelength detection unit 51 and the oscillation wavelength is shifted to a longer wavelength side than the reference wavelength, the injection current into the semiconductor laser 1 is increased. If the oscillation wavelength is shifted to a shorter wavelength side than the reference wavelength, a control signal ⁇ 1 for increasing the injection current to the semiconductor laser 1 is sent to the semiconductor laser 1.
  • the oscillation wavelength of the semiconductor laser 1 becomes longer.
  • the laser controller 52 receives the deviation signal from the wavelength detector 51, the oscillation wavelength becomes the reference wavelength. If the oscillation wavelength is shifted to a longer wavelength side, the temperature of the semiconductor laser 1 is increased. If the oscillation wavelength is shifted to a shorter wavelength side than the reference wavelength, the control signal T is set to lower the temperature of the semiconductor laser 1. Send 1 to semiconductor laser 1.
  • the polarization direction of the laser light is p-polarization.
  • s-polarization laser light that is, laser light having a polarization direction perpendicular to the plane formed by the C axis and the optical axis Is incident on the uniaxial birefringent crystal
  • the temperature compensation condition of Equation (7) can be satisfied. That is, the above equation (7) is satisfied for both the ordinary optical axis and the extraordinary optical axis.
  • the C axis is set in a plane perpendicular to the plane formed by the optical axis and the polarization direction of the laser light.
  • the angle ⁇ c between the optical axis and the C axis is 57.05 degrees.
  • the refractive index n and d n / d t when the ordinary optical axis is used do not depend on the angle ⁇ c and always take a constant value. In this case, only the linear expansion coefficient ⁇ in the equation (7) changes depending on the angle ⁇ c.
  • uniaxial birefringent crystal constituting the Fuaburipero resonator 3 (such as 0- BBO (B a ⁇ 2 0 4)), C -axis of the laser beam Since the C-axis of the parenthesis is located in a plane formed by the optical axis and the polarization direction or in a plane perpendicular to the plane, and the C-axis of the parenthesis is arranged to have a constant inclination with respect to the optical axis,
  • This Fabry-Perot resonator 3 can have a temperature compensation function (a function in which the intensity of the signal light emitted from the Fabry-Perot resonator 3 does not depend on its temperature), and the light intensity monitor signal S 1 depends only on the wavelength of the optical signal.
  • the wavelength of the optical signal emitted from the semiconductor laser 1 can be controlled to a desired reference wavelength based on the detected light intensity monitor signal S1. Further, since only a uniaxial birefringent crystal of one material is used, the configuration of the semiconductor laser device can be simplified.Since the configuration is simplified, the reliability as a wavelength monitor can be improved. .
  • the material of the Fabry-Bore-single resonator 3 is a 3— ⁇ ⁇ ⁇ crystal.
  • a—BBO BaB 2 OJ crystal
  • the physical constants of ⁇ -BBO are as follows: extraordinary refractive index ne is 1.53003, ordinary refractive index no is 1.6502, and thermo-optic coefficient d no / d T is -9.3 X 1 0 one 6 / K, a thermal optical coefficient d ne / dT is 1 6. 6 X 10- 6 / K , in the linear expansion coefficient ratio c is 36. 0 X 10- 6 / K, the linear expansion coefficient aa 4 . is a 0X 10- 6 / K.
  • ⁇ c 64.35 degrees when the polarization of the laser beam was aligned with the extraordinary optical axis
  • ⁇ > c 76.95 degrees when the polarization of the laser beam was aligned with the ordinary optical axis.
  • the temperature characteristic is about 1 pm / ° C in the range of about 74 to 80 degrees, which is sufficiently smaller than the temperature characteristic of a conventional solid ethanol port (up to 10 pm / 'C).
  • the extraordinary optical axis direction is from 11 pm, ° C to +47 pm / ° C, and the ordinary optical axis direction is from ⁇ 3 pmZ ° C to +47 pmZ ° C.
  • Any temperature coefficient can be selected. This makes it possible to adjust the wavelength characteristics by changing the temperature, and it is easy to adjust to the ITU grid.
  • the 1 GHz wavelength characteristic can be shifted by changing the temperature of the uniaxial birefringent crystal 3 by 1 ° C.
  • the angle phi c satisfying the temperature compensation condition dn / dT + ⁇ - ⁇ is 18.65 degrees.
  • ⁇ c 22.70 degrees when the polarization of the laser light is aligned with the extraordinary optical axis
  • ⁇ c 18.65 degrees when the polarization of the laser light is aligned with the ordinary optical axis. If the angle is in the vicinity of this, the temperature characteristics can be sufficiently suppressed.
  • the temperature characteristic is 1 pmZ ° C in the range of about 15 to 22 degrees, which is much smaller than the temperature characteristic of a conventional solid etalon (up to 10 pmZ ° C).
  • the direction of the extraordinary optical axis is from -20 pmZ ° C to +3 pm / ° C
  • the direction of the ordinary optical axis is any temperature from ⁇ 28 pm, ° C to +3 pmZ ° C.
  • Coefficient can be selected. This makes it possible to adjust the wavelength characteristics by changing the temperature, and it is easy to adjust to the ITU grid.
  • the 1 GHz wavelength characteristic can be shifted. Therefore, when trying to match the ITU grid with a spacing of 25 GHz to the wavelength control point specified in advance, the temperature of the base carrier 6 on which the semiconductor laser 1 is mounted is changed by up to 25 degrees and the semiconductor laser 1 By changing the oscillation wavelength by adjusting the injection current into the device, it is possible to match the desired wavelength control point.
  • a C a C O 3 crystal may be used as the uniaxial birefringent crystal.
  • the temperature characteristic is 1 pmZ ° C in the range of about 65 to 70 degrees. This is sufficiently smaller than the temperature characteristics ( ⁇ 10 pm / ° C) of the conventional solid nozzle.
  • the extraordinary optical axis direction is from +4 pmZT: to +40 pm /, and the ordinary optical axis direction is from -7 pmZ ° C to +40 pmZ ° C.
  • the temperature coefficient can be selected arbitrarily.
  • FSR 25 GHz
  • c is set so that the temperature characteristic is 8 pm / ° C.
  • the temperature of the uniaxial birefringent crystal 3 is changed by 1 ° C. Therefore, if an attempt is made to match the wavelength control point specified in advance with the ITU grid of 25 GHz spacing, the temperature of the base carrier 6 on which the semiconductor laser 1 is mounted is changed by a maximum of 25 degrees and the semiconductor laser is changed.
  • the oscillation wavelength by adjusting the injection current to 1, it is possible to match the desired wavelength control point.
  • any other uniaxial birefringent crystal may be used as long as the material satisfies the temperature compensation conditional expression (7) for the Fabry-Perot resonator.
  • the wavelength monitoring device shown in FIG. 3 with the wavelength monitoring device shown in FIG. 16, it is possible to construct a wavelength stable light source.
  • FIG. 17 is a configuration diagram showing a wavelength monitor according to a modification of the first embodiment of the present invention.
  • the second photodiode 5 located above the Fabry-Perot resonator 3 is arranged forward of the first photodiode 4 so as to reduce the distance from the lens 2. . That is, in this case, the location where the second photodiode 5 of the base carrier 6 is installed is protruded toward the semiconductor laser 1, and the location where the first photodiode 4 of the base carrier 6 is installed A step is formed between the base carrier 6 and the position where the second photodiode 5 is provided.
  • the second photodiode 5 is arranged ahead of the first photodiode 4, even if the optical signal is Even if the light is scattered on the bottom surface of the base carrier 6 after being incident on the Perot resonator 3, the scattered light is not received by the second photodiode 5 after passing through the Fabry-Perot resonator 3.
  • each photodiode monitors the wavelength and intensity of the optical signal.
  • three photodiodes are arranged, and two Fabry-Perot resonators (wavelength filters) are vertically arranged in parallel, so that the three photodiodes are arranged.
  • the two photodiodes are used to monitor the wavelength of an optical signal in a wide band and a narrow band, and the optical intensity signal is monitored using a single photodiode.
  • FIG. 18 is a configuration diagram showing a wavelength monitoring apparatus according to Embodiment 2 of the present invention.
  • the temperature and the injection current of the semiconductor laser 1 are controlled by the control signal T1 sent from the wavelength control device 60 shown in FIG. 19 to control the wavelength.
  • the Fabry-Perot resonator (wavelength filter) 21 is the same as the Fabry-Perot resonator (wavelength filter) 3, and is cut out so as to have the temperature compensation function shown in the first embodiment. BBO), and has reflection films 23 and 24 on its entrance and exit surfaces.
  • the thickness of the Fabry-Perot resonator 3 arranged on the lower side in the Z direction is made larger than the thickness of the Fabry-Perot resonator 21 arranged on the upper side.
  • the Fabry-Perot resonator 21 is used for broadband monitoring.
  • the third photodiode 22 detects the intensity of an optical signal transmitted through the Fabry-Perot resonator 21, and is arranged between the first photodiode 4 and the second photodiode 5.
  • the light signal is condensed by the lens 2 and converted into parallel light.
  • the intensity of the optical signal transmitted through the Fabry-Perot resonator (for narrow band) 3 is detected, and in the third photodiode 22, the optical signal transmitted through the Fabry-Perot resonator (for wide band) 21 The intensity is detected.
  • the light intensity monitor signal detected by the first photodiode 4 is S1
  • the light intensity monitor signal detected by the third photodiode 22 is S3
  • the light intensity monitor signal is detected by the second photodiode 5.
  • the light intensity monitor signal is S2.
  • the light intensity monitor signals S1, S2 and S3 are sent to the wavelength control device 60 shown in FIG.
  • the wavelength control device 60 detects the oscillation wavelength using these signals S1, S2, and S3, and controls the control signal T for controlling the wavelength of the optical signal emitted from the semiconductor laser 1 based on the detected wavelength.
  • the control signal T 1 is output to the semiconductor laser 1.
  • FIG. 20 shows the wavelength transmission characteristics of the Fabry-Perot resonator 3 for the narrow band and the Fabry-Perot resonator 21 for the wide band.
  • the FSR of the Fabry-Perot resonator 3 for the narrow band is set to be very small compared to the FSR of the Fabry-Perot resonator 21 for the wide band. I do. Further, half of the FSR of the Fabry-Perot resonator 21 for a wide band, that is, the wavelength discrimination region is larger than the wavelength variable range of the semiconductor laser 1, and the wavelength variable range of the semiconductor laser 1 is 1 in the FSR of the Fabry-Perot resonator 21. Suppose it is within one slope.
  • the Fabry-Perot resonator 3 for narrow band has an FSR of 20 THz
  • the intensity reflectance of the reflective film is 30%
  • the FSR of the Fabry-Perot resonator 21 for broadband is 10 OGHz
  • the intensity reflectance of the reflective film is Assume 30%.
  • the wavelength control device 60 includes a wavelength detection unit 61 and a laser control unit 52.
  • the light intensity monitor signals S 1, S 2, S 3 from the first to third photodiodes 4, 5, and 22 and the reference wavelength; 0 are input to the wavelength detector 61.
  • the wavelength detecting section 61 outputs an optical signal emitted from the semiconductor laser 1 by the light intensity monitor signals S1, S2, and S3.
  • the difference between this oscillation wavelength and the reference wavelength; 0 is found.
  • the difference between the reference wavelength ⁇ 0 from the wavelength detection unit 61 and the oscillation wavelength emitted from the semiconductor laser 1 is input to the laser control unit 52, and the laser control unit 52 determines the oscillation wavelength according to the difference.
  • a control signal ⁇ 1 for controlling the temperature, injection current, and the like of the semiconductor laser 1 is determined so that the control signal ⁇ coincides with the reference wavelength ⁇ 0, and the control signal ⁇ 1 is output to the semiconductor laser 1.
  • the wavelength detection unit 61 detects a shift from the reference wavelength; 0 using the light intensity monitor signal S3 transmitted through the Fabry-Perot resonator 21 for a wide band. That is, as described above, the wavelength detector 61 has a signal intensity ratio S 1 / S 2 at the reference wavelength ⁇ 0, which is obtained in advance using the wavelength transmission characteristics of the Fabry-Perot resonator 21 for a wide band.
  • the oscillation wavelength and the reference wavelength are obtained. Calculate the deviation (deviation) from ⁇ 0.
  • this deviation amount is larger than the slope width of the narrow-band fabric resonator 3, this value is sent to the laser control unit 52 as it is.
  • the deviation from the reference wavelength calculated from the light intensity monitor signals S 3 and S 2; I 0 is smaller than the slope width of the narrow-band Fabry-Perot resonator 3, the narrow-band Fabry-Perot resonance
  • the oscillation wavelength is detected with higher accuracy. That is, a reference wavelength previously calculated using the wavelength transmission characteristics of the Fabry-Perot resonator 3 for a narrow band; a signal intensity ratio S 1 / S 2 at 0; and light from the first and second photodiodes 4 and 5.
  • the difference (deviation) between the oscillation wavelength and the reference wavelength ⁇ 0 is calculated by calculating the difference between the signal intensity ratio S 3 / S 2 obtained based on the intensity monitor signals S 1 and S 2.
  • the deviation amount (deviation signal) thus obtained is sent to the laser control unit 52.
  • Laser control unit 52 operates in the same manner as in the first embodiment. That is, the laser control unit 52 uses the deviation signal input from the wavelength detection unit 61 to output a control signal ⁇ 1 for changing the value of the temperature or the injection current to the semiconductor laser 1. Thus, the wavelength of the semiconductor laser 1 is controlled.
  • the absolute wavelength can be monitored over a wide band.
  • the wavelength transmission characteristic of the Fabry-Perot resonator 21 for a wide band is more dependent on the wavelength change than the wavelength transmission characteristic of the resonator element 3 for a narrow band. Is small. That is, the light intensity monitor signal S3 has a smaller signal intensity change with respect to the wavelength change than the light intensity monitor signal S1.
  • the wavelength of the optical signal emitted from the semiconductor laser 1 can be fixed more accurately by using the optical signal intensity S1 transmitted through the Fabry-Perot resonator 3, which is a wavelength monitor for a narrow band.
  • the resonators of the resonators 3 and 21 are arranged such that the lower Fabry-Perot resonator 3 is used as a wavelength monitor for a wide band and the upper Fabry-Perot resonator 21 is used as a wavelength monitor for a narrow band.
  • the length may be adjusted.
  • the absolute wavelength of the optical signal emitted from the semiconductor laser 1 can be controlled with high accuracy over a wide band.
  • a wavelength stabilized light source can be configured by combining the wavelength monitoring device shown in FIG. 18 with the wavelength control device shown in FIG.
  • FIG. 21 is a configuration diagram showing a wavelength monitor according to a modification of the second embodiment of the present invention.
  • the second and third photodiodes 5, 22 located above the Fabry-Perot resonator 3 are connected to the first photodiode 4 so that the distance from the lens 2 is reduced.
  • the location where the second and third photodiodes 5, 22 of the base carrier 6 are installed is configured to protrude toward the semiconductor laser 1, and the first photodiode 4 of the base carrier 6 is mounted.
  • Location and location of base carrier 6 A step is formed between the third photodiode 5 and the place where the third photodiodes 22 are installed.
  • the second and third photodiodes 5, 22 are arranged in front of the first photodiode 4, so that the optical signal is Fabry. Even if the scattered light is transmitted through the Fabry-Perot resonator 3 and then scattered on the bottom surface of the base carrier 6 after being incident on the mouth resonator 3, it is received by the second and third photodiodes 5 and 22. Disappears. Industrial applicability
  • the present invention is suitable for use as a wavelength filter or a wavelength monitor of a semiconductor laser as a light source used in wavelength division multiplexing (WDM) communication and high-density wavelength division multiplexing (DWDM) communication using an optical fiber. .
  • WDM wavelength division multiplexing
  • DWDM high-density wavelength division multiplexing
  • it is required to select or monitor the wavelength of laser light with high accuracy without being affected by temperature fluctuations, and it is suitable for systems that require simplification of structure and assembly.

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Abstract

L'invention concerne un matériau solide transmetteur de lumière, des plans formés dans ce matériau solide, opposés et sensiblement parallèles les uns aux autres, et un filtre de longueur d'onde destiné à sélectionner périodiquement la longueur d'onde déterminée par la longueur du chemin optique entre les plans opposés par mise en oeuvre d'une résonance entre les plans opposés et sensiblement parallèles les uns aux autres. Le matériau solide est un matériau à réfraction double et son axe optique fait un angle déterminé par rapport à la normale aux plans opposés et sensiblement parallèles les uns aux autres. Il en résulte que la caractéristique de température du filtre de longueur d'onde peut être librement établie, et qu'une caractéristique arbitraire de longueur d'onde peut être sélectionnée par changement de la température du filtre de longueur d'onde.
PCT/JP2002/009173 2002-04-15 2002-09-09 Filtre de longueur d'onde et appareil de suivi de longueur d'onde WO2003087898A1 (fr)

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PCT/JP2002/003715 WO2003088436A1 (fr) 2002-04-15 2002-04-15 Appareil de controle de longueur d'onde
JPPCT/JP02/03715 2002-04-15

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007095936A (ja) * 2005-09-28 2007-04-12 Mitsubishi Electric Corp 炭酸ガスレーザ加工機及び炭酸ガスレーザ加工方法
US7283302B2 (en) 2003-03-19 2007-10-16 Mitsubishi Denki Kabushiki Kaisha Wavelength filter and wavelength monitor device
JP7036666B2 (ja) 2018-05-23 2022-03-15 三菱重工業株式会社 レーザ装置及び加工装置

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EP0939470A2 (fr) * 1998-02-27 1999-09-01 Nec Corporation Circuit de contrÔle de la longueur d'onde d'un signal laser
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US5982488A (en) * 1996-03-22 1999-11-09 Fujitsu Limited Compensator which experiences thermal expansion to compensate for changes in optical distance through a transparent material
EP1109276A2 (fr) * 1999-12-16 2001-06-20 Lucent Technologies Inc. Procédé et dispositif de stabilisation en longueur d'onde d'un laser
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EP1133034A2 (fr) * 2000-03-10 2001-09-12 Nec Corporation Dispositif laser à longueur d'onde stabilisé
EP1136848A2 (fr) * 2000-03-15 2001-09-26 Agere Systems Guardian Corporation Utilisation des matériaux cristallins afin de contrôler le comportement thermo-optique d'un chemin optique
EP1158630A1 (fr) * 2000-04-25 2001-11-28 Alcatel Dispositif de stabilisation en longueur d'onde et méthode de réglage de la longueur d'onde de travail du dispositif

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JPH03160774A (ja) * 1989-11-20 1991-07-10 Toshiba Corp 半導体レーザモジュール
US5982488A (en) * 1996-03-22 1999-11-09 Fujitsu Limited Compensator which experiences thermal expansion to compensate for changes in optical distance through a transparent material
EP0867989A1 (fr) * 1997-03-24 1998-09-30 Ando Electric Co., Ltd. Source de lumière à semi-conducteur à longueur d'onde accordable
JPH11242115A (ja) * 1998-02-26 1999-09-07 Fujitsu Ltd 温度依存性のない光素子
EP0939470A2 (fr) * 1998-02-27 1999-09-01 Nec Corporation Circuit de contrÔle de la longueur d'onde d'un signal laser
EP1109276A2 (fr) * 1999-12-16 2001-06-20 Lucent Technologies Inc. Procédé et dispositif de stabilisation en longueur d'onde d'un laser
JP2001244557A (ja) * 2000-02-29 2001-09-07 Mitsubishi Electric Corp 波長モニタ装置、およびその調整方法、並びに波長安定化光源
EP1133034A2 (fr) * 2000-03-10 2001-09-12 Nec Corporation Dispositif laser à longueur d'onde stabilisé
EP1136848A2 (fr) * 2000-03-15 2001-09-26 Agere Systems Guardian Corporation Utilisation des matériaux cristallins afin de contrôler le comportement thermo-optique d'un chemin optique
EP1158630A1 (fr) * 2000-04-25 2001-11-28 Alcatel Dispositif de stabilisation en longueur d'onde et méthode de réglage de la longueur d'onde de travail du dispositif

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7283302B2 (en) 2003-03-19 2007-10-16 Mitsubishi Denki Kabushiki Kaisha Wavelength filter and wavelength monitor device
JP2007095936A (ja) * 2005-09-28 2007-04-12 Mitsubishi Electric Corp 炭酸ガスレーザ加工機及び炭酸ガスレーザ加工方法
JP7036666B2 (ja) 2018-05-23 2022-03-15 三菱重工業株式会社 レーザ装置及び加工装置

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