WO2016152274A1 - Élément laser à longueur d'onde variable et module laser - Google Patents

Élément laser à longueur d'onde variable et module laser Download PDF

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Publication number
WO2016152274A1
WO2016152274A1 PCT/JP2016/053463 JP2016053463W WO2016152274A1 WO 2016152274 A1 WO2016152274 A1 WO 2016152274A1 JP 2016053463 W JP2016053463 W JP 2016053463W WO 2016152274 A1 WO2016152274 A1 WO 2016152274A1
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Prior art keywords
waveguide
comb
wavelength
tunable laser
reflection spectrum
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PCT/JP2016/053463
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English (en)
Japanese (ja)
Inventor
泰雅 川北
康貴 比嘉
岩井　則広
黒部　立郎
Original Assignee
古河電気工業株式会社
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Priority claimed from JP2016008579A external-priority patent/JP6684094B2/ja
Application filed by 古河電気工業株式会社 filed Critical 古河電気工業株式会社
Priority to CN201680012598.3A priority Critical patent/CN107431331B/zh
Publication of WO2016152274A1 publication Critical patent/WO2016152274A1/fr
Priority to US15/708,994 priority patent/US10193305B2/en

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    • 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
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region

Definitions

  • the present invention relates to a wavelength tunable laser device and a laser module using the same.
  • Non-Patent Document 1 The configuration and operation principle of the wavelength tunable laser element are described in detail, for example, in Non-Patent Document 1.
  • DBR distributed Bragg reflector
  • Sampled Grating sampled diffraction grating
  • the reflection spectra of the two DBR mirrors have a comb-like shape with a slightly different period. Further, by causing a change in refractive index to the DBR mirror by current injection or heating, it is possible to make its reflection wavelength characteristic variable. By multiplying the reflection characteristics of the two DBR mirrors, the reflectance of a specific wavelength region can be increased to form a resonator. At this time, if the resonator length is properly designed, the distance between the longitudinal modes, which are resonator modes, becomes approximately the same as the reflection band by two DBR mirrors, only one resonator mode is selected, and single mode oscillation is To be realized.
  • the resonator is made long enough to obtain a laser beam with a narrow line width required for coherent communication, the longitudinal mode spacing becomes narrow, and the reflection band of the resonator Since it is difficult to select only one resonator mode, it is in principle difficult to obtain single mode oscillation.
  • the resonator is configured using two ring resonators
  • the reflectance fluctuation of the overlapping portion is large. Therefore, in order to realize stable laser oscillation, it is necessary to ensure that the peaks of the two sharp reflection wavelength characteristics overlap with each other, but such control is difficult.
  • the present invention has been made in view of the above, and it is an object of the present invention to provide a wavelength tunable laser device which can realize narrowing of the width of laser light and stable single mode oscillation, and a laser module using the same. Do.
  • a wavelength tunable laser device includes a diffraction grating and a reflection mirror including a ring resonator filter optically coupled to the diffraction grating.
  • a tunable laser device comprising: a configured laser resonator; a gain unit disposed in the laser resonator; and a phase adjusting unit disposed in the laser resonator, wherein the diffraction grating is A first comb-like reflection spectrum is generated, and the ring resonator filter is optically coupled to the ring waveguide, each of which is optically coupled to the ring waveguide, and one end thereof is integrated to form the optical grating and the optical grating.
  • a second comb-like reflection spectrum having a wavelength interval between the first and second comb-like reflection spectra, and the diffraction grating and the ring resonator produce one of the peaks of the first comb-like reflection spectrum and one of the peaks of the second comb-like reflection spectrum.
  • the laser resonators are configured such that the spacing between the modes of the resonator modes is narrower than the full width at half maximum of the peak of the first comb-like reflection spectrum. ing.
  • a laser module according to an aspect of the present invention includes the wavelength tunable laser element according to the aspect of the present invention.
  • FIG. 1 is a schematic perspective view of the wavelength tunable laser device according to the first embodiment.
  • FIG. 2A is a schematic cross-sectional view of the wavelength tunable laser device shown in FIG.
  • FIG. 2B is a schematic cross-sectional view of the wavelength tunable laser device shown in FIG.
  • FIG. 2C is a schematic cross-sectional view of the wavelength tunable laser device shown in FIG.
  • FIG. 3A is a diagram showing a first comb-like reflection spectrum and a second comb-like reflection spectrum.
  • FIG. 3B is a diagram showing a first comb reflection spectrum, a second comb reflection spectrum, and a resonator mode.
  • FIG. 4 is a diagram showing a first comb-like reflection spectrum, a second comb-like reflection spectrum and an overlap thereof.
  • FIG. 5 is a diagram for explaining the optical feedback in the wavelength tunable laser device shown in FIG.
  • FIG. 6 is a diagram for explaining a method of selecting a laser oscillation wavelength in the wavelength tunable laser device shown in FIG.
  • FIG. 7AA is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7AB is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7AC is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7AA is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7AB is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown
  • FIG. 7BA is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7BB is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7BC is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7CA is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7CB is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7CC is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG.
  • FIG. 7CC is a cross-sectional view showing an example of a method of manufacturing the wavelength tunable laser shown in FIG. FIG.
  • FIG. 8 is a view for explaining a waveguide portion which optically couples the ring waveguide and the two arm portions in the wavelength tunable laser device shown in FIG.
  • FIG. 9A is a view for explaining the structure of the waveguide section.
  • FIG. 9B is a view for explaining the structure of the waveguide section.
  • FIG. 10 is a diagram for explaining an example of the first waveguide section having a ridge waveguide structure.
  • FIG. 11 is a schematic perspective view of the wavelength tunable laser device according to the second embodiment.
  • FIG. 12A is a schematic perspective view of a wavelength tunable laser device according to a third embodiment. 12B is a schematic cross-sectional view of the wavelength tunable laser device according to Embodiment 3.
  • FIG. FIG. 13 is a schematic perspective view of the wavelength tunable laser device according to the fourth embodiment.
  • FIG. 14 is a schematic view of a laser module according to the fifth embodiment.
  • FIG. 15 is a schematic view of a laser module according to the sixth
  • the tunable laser device is a tunable laser device using the vernier effect, wherein the peak of the first comb-like reflection spectrum is narrower than the full width at half maximum of the peak of the first comb-like reflection spectrum. Having a second comb-like reflection spectrum having a wavelength spacing different from the wavelength spacing, and the spacing between the modes of the resonator modes being narrower than the full width at half maximum of the first comb-like reflection spectrum By being configured, narrowing of the line width of laser light and stable single mode oscillation can be realized.
  • FIG. 1 is a schematic perspective view of the wavelength tunable laser device according to the first embodiment.
  • the wavelength tunable laser device 100 is configured to emit a laser beam by performing laser oscillation in a 1.55 ⁇ m band.
  • the wavelength tunable laser device 100 includes a first waveguide section 10 and a second waveguide section 20 formed on a common base B.
  • the base B is made of, for example, n-type InP.
  • An n-side electrode 30 is formed on the back surface of the base B.
  • the n-side electrode 30 includes, for example, AuGeNi, and makes ohmic contact with the base B.
  • the first waveguide unit 10 includes a waveguide unit 11, a semiconductor multilayer unit 12, a p-side electrode 13, and microheaters 14 and 15 made of Ti.
  • the waveguide portion 11 is formed to extend in the z direction in the semiconductor multilayer portion 12.
  • a diffraction grating loading type gain unit 11a and a phase adjustment unit 11b are disposed.
  • the semiconductor multilayer portion 12 is configured by laminating semiconductor layers, and has a function of a cladding portion and the like with respect to the waveguide portion 11. The configurations of the waveguide portion 11 and the semiconductor laminated portion 12 will be described in detail later.
  • the p-side electrode 13 is disposed on the semiconductor laminated portion 12 along the diffraction grating loaded gain portion 11 a.
  • the SiN protective film mentioned later is formed in the semiconductor lamination part 12, and the p side electrode 13 is in contact with the semiconductor lamination part 12 via the opening part formed in the SiN protection film.
  • the micro heater 14 is disposed on the SiN protective film of the semiconductor lamination portion 12 so as to be along the phase adjustment portion 11 b.
  • the microheater 15 as a first refractive index changer is disposed along the p-side electrode 13 on the SiN protective film of the semiconductor multilayer portion 12.
  • FIG. 2A is a cross-sectional view taken along the line AA of a portion of the first waveguide section 10 including the diffraction grating loaded gain section 11a, which is cut along a plane parallel to the xy plane of FIG.
  • the diffraction grating loading type gain portion 11a is composed of an active core layer 11aa and a sampling grating provided along the active core layer 11aa in the vicinity of and directly on the active core layer 11aa. And 11ab.
  • Active core layer 11aa has a multiple quantum well structure including a plurality of well layers and a plurality of barrier layers alternately stacked, and a multiple quantum well structure from the top to the bottom and the upper light confinement layer It emits light by current injection.
  • the well layer and the barrier layer constituting the multiple quantum well structure of the active core layer 11aa are made of InGaAsP different in composition from each other, and the emission wavelength band from the active core layer 11aa is 1.55 ⁇ m band in the first embodiment.
  • the lower optical confinement layer is made of n-type InGaAsP.
  • the upper optical confinement layer is made of p-type InGaAsP.
  • the band gap wavelengths of the lower and upper optical confinement layers are set to be shorter than the band gap wavelength of the active core layer 11aa.
  • a sampling diffraction grating is formed in the p-type InGaAsP layer along the z direction, and the groove of the diffraction grating has a configuration embedded in InP.
  • the grating interval of the diffraction grating is constant but sampled, thereby exhibiting a reflection response that is substantially periodic with respect to the wavelength.
  • the band gap wavelength of the p-type InGaAsP layer of the diffraction grating layer 11ab is preferably shorter than the band gap wavelength of the active core layer 11aa, and is, for example, 1.2 ⁇ m.
  • the semiconductor laminated portion 12 in the portion including the diffraction grating loaded gain portion 11a has, for example, the following configuration.
  • the semiconductor multilayer portion 12 has an n-type semiconductor layer 12a of n-type InP formed of a buffer layer having a function of a lower cladding layer on an n-type InP substrate forming the base B.
  • Active core layer 11aa is stacked on n-type semiconductor layer 12a.
  • a spacer layer 12b made of p-type InP is stacked on the active core layer 11aa.
  • the diffraction grating layer 11ab is stacked on the spacer layer 12b.
  • Active core layer 11aa, spacer layer 12b and diffraction grating layer 11ab have a stripe mesa structure having a width (for example, 1.8 .mu.m) suitable for single-mode optical waveguide of 1.55 .mu.m band by etching or the like. It is done. Both sides of the stripe mesa structure (in the left-right direction in the drawing) have a buried structure having a current blocking structure including a p-type InP buried layer 12c and an n-type InP current blocking layer 12d.
  • the p-type semiconductor layer 12e is provided at least from immediately above the active core layer 11aa to a part of the embedded structure on both sides thereof.
  • a SiN protective film 16 is formed on the semiconductor laminated portion 12 so as to cover the semiconductor laminated portion 12.
  • the p-side electrode 13 contains AuZn, is formed on the contact layer 12eb, and is in ohmic contact with the contact layer 12eb via the opening 16a of the SiN protective film 16. With the above configuration, current injection from the n-side electrode 30 and the p-side electrode 13 to the active core layer 11aa is possible. Furthermore, the microheater 15 is disposed along the p-side electrode 13 on the SiN protective film 17 provided in the semiconductor laminated portion 12 in order to insulate the p-side electrode 13 from the microheater 15.
  • FIG. 2B is a cross-sectional view taken along the line BB taken along a plane parallel to the xy plane in FIG. 1, of a portion of the first waveguide 10 including the phase adjustment portion 11b.
  • the sectional structure of the first waveguide section 10 including the phase adjustment section 11b replaces the active core layer 11aa in the structure shown in FIG. 2A with the phase adjustment section 11b which is an optical waveguide layer made of InGaAsP.
  • the diffraction grating layer 11ab and the spacer layer 12b are replaced by the p-type InP layer 12f, and the contact layer 12eb is eliminated.
  • the band gap wavelength of the phase adjustment part 11b is preferably shorter than the band gap wavelength of the active core layer 11aa, for example, 1.3 ⁇ m or less is there.
  • the first waveguide section 10 has the embedded waveguide structure as the first waveguide structure.
  • the second waveguide portion 20 includes a bifurcated portion 21, two arm portions 22 and 23, a ring-shaped waveguide 24, and a micro heater 25 made of Ti.
  • the bifurcated portion 21 is composed of a 1 ⁇ 2 type branched waveguide including a 1 ⁇ 2 type multimode interference (MMI) waveguide 21 a, and the two port side is connected to each of the two arm portions 22 and 23. At the same time, one port side is connected to the first waveguide section 10 side. One end of the two arm portions 22 and 23 is integrated by the bifurcated portion 21 and optically coupled to the diffraction grating layer 11ab.
  • MMI multimode interference
  • Each of the arm portions 22 and 23 extends in the z direction, and is disposed so as to sandwich the ring waveguide 24.
  • the arm portions 22 and 23 are in close proximity to the ring waveguide 24 and both are optically coupled to the ring waveguide 24 with the same coupling coefficient ⁇ .
  • the value of ⁇ is, for example, 0.2.
  • the arm portions 22 and 23 and the ring waveguide 24 constitute a ring resonator filter RF1. Further, the ring resonator filter RF1 and the bifurcated portion 21 constitute a reflection mirror M1.
  • the microheater 25 as a second refractive index changer is ring-shaped, and is disposed on a SiN protective film formed to cover the ring-shaped waveguide 24.
  • FIG. 2C is a cross-sectional view of the arm portion 22 of the second waveguide portion 20 taken along line CC cut along a plane parallel to the xy plane of FIG.
  • a lower cladding layer 22a of n-type InP, an optical waveguide layer 22b of InGaAsP, and an upper cladding layer 22c of p-type InP are stacked in this order on the base B.
  • the high mesa waveguide structure is configured.
  • the SiN protective film 22 d is formed to cover the arm portion 22.
  • the other components of the second waveguide portion 20, such as the bifurcated portion 21, the arm portion 23, and the ring waveguide 24 also have a high mesa waveguide structure, and are covered with a SiN protective film. There is. That is, the second waveguide section 20 has a second waveguide structure different from the first waveguide structure of the first waveguide section 10.
  • the first waveguide unit 10 and the second waveguide unit 20 are configured of a laser resonator C1 configured of the diffraction grating layer 11ab of the diffraction grating loading type gain unit 11a optically connected to each other and the reflection mirror M1. Configured.
  • the active core layer 11aa as the gain portion of the diffraction grating loading type gain portion 11a and the phase adjustment portion 11b are disposed in the laser resonator C1.
  • FIGS. 3A and 3B the vertical axis indicates reflectivity.
  • the diffraction grating layer 11ab generates a first comb-like reflection spectrum having substantially periodic reflection characteristics at substantially predetermined wavelength intervals, as shown by a curve in a legend “SG” in FIG. 3A.
  • the ring resonator filter RF1 generates a second comb-like reflection spectrum having periodic reflection characteristics at predetermined wavelength intervals, as shown by a curve in a legend “Ring” in FIG. 3A.
  • the legend "Mode” indicates the resonator mode of the laser resonator C1.
  • the resonator modes exist over at least the wavelength range of 1530 nm to 1570 nm shown in FIG. 3A.
  • the second comb reflection spectrum has a peak SC2 of full width at half maximum narrower than the full width at half maximum of the spectral component SC1 of the first comb reflection spectrum, and the first comb reflection is It has substantially periodic reflection characteristics at wavelength intervals different from the wavelength intervals of the spectrum.
  • the spectral components are not strictly equal wavelength intervals in consideration of the wavelength dispersion of the refractive index.
  • the wavelength interval between the peaks of the first comb-like reflection spectrum (free spectral range: FSR) is 373 GHz in terms of light frequency, and the full width at half maximum of each peak is light The frequency is 43 GHz.
  • the wavelength interval (FSR) between the peaks of the second comb-like reflection spectrum is 400 GHz in terms of the light frequency, and the full width at half maximum of each peak is 25 GHz in terms of the light frequency. That is, the full width at half maximum (25 GHz) of the peak of the second comb reflection spectrum is narrower than the full width at half maximum (43 GHz) of the peak of the first comb reflection spectrum.
  • the peak of the second comb-like reflection spectrum has a shape that changes sharply with respect to the wavelength, and the second derivative of the reflectance with respect to the wavelength takes positive values on the short wavelength side and long wavelength side from the peak There is a wavelength range.
  • the peak of the second comb reflection spectrum is, for example, in the form of a double exponential distribution (Laplace distribution) type.
  • the peak of the first comb-like reflection spectrum has a shape that changes gently with respect to the wavelength, compared to the peak of the second comb-like reflection spectrum, and the second derivative of the reflectance with respect to wavelength
  • the peak of the first comb-like reflection spectrum is, for example, a Gaussian shape.
  • FIG. 4 is a diagram showing a first comb-like reflection spectrum, a second comb-like reflection spectrum and an overlap thereof.
  • the curve indicated by the legend "Overlap” indicates spectral overlap. In the example shown in FIG. 4, the overlap is largest at a wavelength of 1550 nm.
  • thermo-optical effect is performed by heating the diffraction grating layer 11ab by the microheater 15 using at least one of the microheater 15 and the microheater 25 to change its refractive index by the thermo-optical effect.
  • One comb-like reflection spectrum is moved entirely on the wavelength axis, and the ring-shaped waveguide 24 is heated by the microheater 25 to change its refractive index to make the second comb-like reflection spectrum on the wavelength axis
  • This can be realized by performing at least one of moving the whole in
  • the resonator length of the laser resonator C1 is set such that the distance between the resonator modes (longitudinal mode distance) is 25 GHz or less. In this setting, the resonator length of the laser resonator C1 is 1800 ⁇ m or more, and narrowing of the line width of the oscillated laser light can be expected.
  • the wavelength tunable laser device 100 injects a current from the n-side electrode 30 and the p-side electrode 13 to the active core layer 11aa to cause the active core layer 11aa to emit light
  • the peak of the spectral component of the first comb reflection spectrum, The peak of the spectral component of the second comb-like reflection spectrum, and one of the resonator modes of the laser resonator are configured to emit a laser at a coincident wavelength, ie 1550 nm, and to output the laser light L1 (see FIG. 1) ing.
  • the wavelength of the resonator mode of the laser resonator C1 heats the phase adjustment unit 11b using the microheater 14 to change its refractive index, and the wavelength of the resonator mode is moved entirely on the wavelength axis. Fine adjustment can be done by That is, the phase adjustment unit 11b is a portion for actively controlling the optical path length of the laser resonator C1.
  • the second comb reflection spectrum by the ring resonator filter RF1 has a full width at half maximum narrower than the full width at half maximum of the peak of the first comb reflection spectrum by the diffraction grating layer 11ab.
  • the peak of the second comb-like reflection spectrum narrower in full width at half maximum is present in the peaks of the first comb-like reflection spectrum wide in half width, the laser oscillation is generated. It becomes easy to control the wavelength.
  • the distance between the resonator modes of the laser resonator C1 is 25 GHz or less, which is narrower than the full width at half maximum (43 GHz) of the spectral component of the first comb reflection spectrum It is configured to be
  • the distance between the resonator modes is narrowed, but in particular, a plurality of resonators within the full width at half maximum of the first comb-like reflection spectrum If the distance between the modes of the resonator modes becomes narrower as the modes exist, selection of a resonator mode for laser oscillation becomes difficult in the normal case.
  • the laser resonator C1 is a long resonator in which the spacing between the modes of the resonator modes is such that two or more resonator modes are included in the peak of the first comb-like reflection spectrum. Even if it is configured to be long, control to select the resonator mode is facilitated. Furthermore, as shown in FIGS.
  • the peak of the second comb reflection spectrum protrudes higher than the height of the peak of the first comb reflection spectrum, and the reflectance of the peak of the second comb reflection spectrum becomes the first comb shape. It can easily be higher than the reflectance of the peak of the reflection spectrum. Therefore, stable single mode oscillation can be realized more easily.
  • the optical feedback in the laser resonator C1 is obtained from the diffraction grating layer 11ab by the two-branch portion 21 and the ring resonator filter RF1. It is performed in a path that is returned to the diffraction grating layer 11ab via the one of the arm portions 22 and 23, the other of the ring waveguide 24 and the other of the arm portions 22 and 23, and the bifurcated portion 21 one time, and one time Of the ring-shaped waveguide 24 during the optical feedback.
  • the arrowhead of the optical path OP indicates the traveling direction of light, and the optical path OP represents both a clockwise optical path and a counterclockwise optical path.
  • the laser oscillation wavelength is selected using the vernier effect.
  • the FSRs of the first comb reflection spectrum and the second comb reflection spectrum are designed to be slightly different. Note that, by increasing the FSR of the second comb-like reflection spectrum where the peak is sharper, the height of the peak of the overlap (for example, the overlap near 1547 nm) adjacent to 1550 nm where the peak of the spectrum overlap is highest It becomes relatively small. As a result, since the laser oscillation at the wavelength of the overlap peak adjacent to the highest wavelength of the overlap of the spectrum is suppressed, the side mode suppression ratio can be increased.
  • the variable wavelength range in the wavelength tunable laser device 100 is determined by the vernier effect at the least common multiple of FSR.
  • One of the peaks of the first comb-like reflection spectrum and one of the peaks of the second comb-like reflection spectrum are superimposed, and the reflectance becomes maximum at a wavelength where the peaks coincide, and laser oscillation occurs. That is, the rough laser oscillation wavelength is determined by the vernier effect of the diffraction grating layer 11ab and the ring resonator filter RF1 (super mode).
  • the laser oscillation wavelength is from the diffraction grating layer 11ab, the bifurcated portion 21, one of the arm portions 22 and 23 of the ring resonator filter RF1, the ring-shaped waveguide 24, Determined by the overlap of the wavelength of the resonator mode and the super mode defined by the path (resonator length) that is fed back to the diffraction grating layer 11ab via the other of the arm portions 22 and 23 and the 2-branch portion 21 in order Ru.
  • one of the resonator modes of the laser resonator C1 is made to coincide with the overlapping region of the peaks of the first comb-like reflection spectrum and the second comb-like reflection spectrum superimposed, and the corresponding cavity modes are made
  • the laser is oscillated at the wavelength of Therefore, in the tunable laser device 100, the first comb-like reflection spectrum and the second comb-like reflection spectrum are respectively tuned by the microheater 15 for the diffraction grating layer 11ab and the microheater 25 for the ring resonator filter RF1.
  • the microheater 14 By tuning the resonator length by the microheater 14 with respect to the coarse adjustment and the phase adjustment unit 11b, a wavelength variable operation to perform fine adjustment is realized.
  • the first comb reflection spectrum and the second comb reflection spectrum have the largest overlap at a wavelength of 1550 nm (super mode).
  • the laser oscillation wavelength is roughly adjusted to around 1550 nm.
  • the diffraction grating layer 11ab is heated by the microheater 15 with the tuning of the ring resonator filter RF1 fixed. Then, the refractive index of the diffraction grating layer 11ab is increased due to the thermo-optical effect, and the reflection spectrum (first comb-like reflection spectrum) of the diffraction grating layer 11ab is generally shifted to the long wave side as shown by the arrows in FIG. Do.
  • the tuning of the diffraction grating layer 11ab is fixed, only the ring resonator filter RF1 is heated by the microheater 25, and the comb reflection spectrum of the ring resonator filter RF1 is entirely It may be shifted to the long wave side.
  • thermo-optical effect by the micro heater is used to realize the wavelength tunable operation, but the carrier plasma effect by current injection is implemented to realize the wavelength tunable operation. May also be available.
  • the refractive index is lowered by current injection, the comb reflection spectrum is entirely shifted to the short wave side, and an overlap occurs in another spectral component existing on the short wave side from the wavelength at which the super mode was formed. , It is possible to form a new super mode.
  • the reflectance is maximum at a wavelength at which the peaks of the comb reflection spectra generated by the diffraction grating layer 11ab and the ring resonator filter RF1 coincide with each other, and laser oscillation occurs as shown in FIG.
  • the first full comb reflection spectrum of full width at half maximum is shifted, and one of its peaks is matched with one of the peaks of the first comb reflection spectrum of narrow full width half maximum.
  • the tuning of the diffraction grating layer 11ab is fixed, only the ring resonator filter RF1 is heated by the microheater 25, and the comb reflection spectrum of the ring resonator filter RF1 is overall
  • the full width at half maximum of the peak due to the diffraction grating layer 11ab is wide, so the peak of the narrow ring resonator filter RF1 with full width at half maximum is tuned to shift to match the supermode It is easy to realize the transition of
  • the phase adjustment unit 11 b is tuned to perform fine adjustment of the resonator mode.
  • the distance between the resonator modes is narrow and narrower than the full width at half maximum of the peak of the comb-like reflection spectrum of the diffraction grating layer 11ab, a plurality of resonator modes exist among the peaks of the diffraction grating layer 11ab. It is also possible to do.
  • the full width at half maximum of the comb reflection spectrum of the ring resonator filter RF1 is narrower than the full width at half maximum of the comb reflection spectrum of the diffraction grating layer 11ab. Therefore, it is unlikely that a plurality of resonator modes compete with the peak of the comb-like reflection spectrum of the ring resonator filter RF1 so that only one resonator mode matches the peak of the ring resonator filter RF1. It is easy to tune the phase adjustment unit 11b to finely adjust the resonator mode.
  • the wavelength tunable laser device 100 As described above, according to the wavelength tunable laser device 100 according to the first embodiment, it is possible to realize narrowing of the line width of the laser light and stable single mode oscillation.
  • an n-type semiconductor layer 12a (lower cladding layer 22a), an active core layer 11aa, and a spacer are formed on the n-type InP substrate constituting the base B by using metal organic chemical vapor deposition (MOCVD).
  • MOCVD metal organic chemical vapor deposition
  • a layer 12b, a p-type InGaAsP layer to be the diffraction grating layer 11ab, and a p-type InP layer to be a part of the spacer layer 12ea (upper cladding layer 22c) are sequentially deposited.
  • a SiN film is newly deposited to form a pattern corresponding to the optical waveguide layer in the waveguide 11 and the second waveguide 20 in the first waveguide 10. Apply patterning as you like. Then, etching is performed using this SiN film as a mask to form a mesa structure in the first waveguide portion 10 and the second waveguide portion 20, and expose the n-type semiconductor layer 12a (lower cladding layer 22a). At this time, the region corresponding to the bifurcated portion 21, the arm portions 22 and 23, and the ring waveguide 24 is etched in the form of a wide region including them.
  • FIGS. 7AA to 7AC are a sectional view taken along a line AA (a gain portion) cut along a plane parallel to the xy plane of FIG. B line sectional view (phase adjustment unit) and FIG. 7AC respectively show CC sectional view (optical waveguide of the arm unit)
  • FIGS. 7BA to 7BC and FIGS. 7CA to 7CC show CC sectional view (optical waveguide of the arm unit)
  • the mask of the SiN film is removed, and a p-type InP layer and a contact layer 12eb to be the remaining portion of the spacer layer 12ea (upper cladding layer 22c) are sequentially deposited on the entire surface by MOCVD (see FIG. 7AA to 7AC).
  • the step of removing the contact layer 12eb of the optical waveguides of the phase adjustment portion and the arm portion is performed (see FIGS. 7BB and 7BC).
  • a SiN film is deposited on the entire surface, and then a pattern corresponding to a trench for element isolation and a waveguide corresponding to the bifurcated portion 21, the arm portions 22 and 23, and the ring waveguide 24 are patterned.
  • etching is performed using this SiN film as a mask to form a trench structure and a high mesa waveguide in the second waveguide portion 20 (see FIG. 7BC).
  • the depth is reached to the base B.
  • a SiN film is deposited again on the entire surface (see FIGS. 7CA to 7CC), and an opening is formed in a portion corresponding to the diffraction grating loading type gain portion 11a to protect the SiN film.
  • the conductive film is patterned to form the p-side electrode 13 (see FIG. 7CA).
  • an n-side electrode 30 containing AuGeNi is formed on the back surface of the substrate. Furthermore, after the SiN protective film 17 is formed, micro-heaters 14, 15, 25 made of, for example, Ti for changing the refractive index are formed. Finally, the substrate is cleaved into a bar shape in which a plurality of variable wavelength laser elements 100 are arranged, and the end face of the first waveguide 10 on the side of the diffraction grating loaded gain 11a and the end of the arm 22 and 23 where the through port is located. After coating the anti-reflection film, the wavelength tunable laser device 100 is separated to complete the wavelength tunable laser device 100.
  • the arm portions 22 and 23 are optically coupled to the ring waveguide 24 by coming close to the ring waveguide 24. As shown, the arm portions 22 and 23 and the ring waveguide 24 may be optically coupled by the waveguide portions 26 and 27.
  • FIG. 9A is a view for explaining the structure of the waveguide section.
  • FIG. 9A is a view showing a part of a cross section along line AA of FIG.
  • the lower cladding layer 22a made of n-type InP, the optical waveguide layer 22b made of InGaAsP, and the upper cladding layer 22c made of p-type InP are stacked in this order on the base B. It has the high mesa waveguide structure comprised.
  • the arm portion 23 is configured by laminating a lower cladding layer 23a of n-type InP, an optical waveguide layer 23b of InGaAsP, and an upper cladding layer 23c of p-type InP in this order on the base B.
  • the waveguide section 26 is configured by laminating a lower cladding layer 26a of n-type InP, an optical waveguide layer 26b of InGaAsP, and an upper cladding layer 26c of p-type InP in this order on the base B. It is a multi-mode interference (MMI) waveguide of high mesa waveguide structure.
  • the waveguide 27 is also an MMI waveguide having a high mesa waveguide structure having the same structure as the waveguide 26.
  • optical coupling between the arm portions 22 and 23 and the ring waveguide 24 is facilitated by optically coupling the arm portions 22 and 23 and the ring waveguide 24 by the waveguide portions 26 and 27.
  • the coupling coefficient ⁇ can be adjusted more easily.
  • the waveguide section for optically coupling the arm sections 22 and 23 and the ring waveguide 24 is not limited to the MMI waveguide, and may be, for example, a directional coupling type waveguide section 26A as shown in FIG. 9B.
  • the waveguide portion 26A is a high mesa formed by laminating a lower cladding layer 26Aa of n-type InP, an optical waveguide layer 26Ab of InGaAsP, and an upper cladding layer 26Ac of p-type InP in this order on the base B.
  • the upper cladding layer 26Ac is thinner than the upper cladding layer 26c in the waveguide portion 26, it functions as a directional coupling waveguide.
  • the change in the coupling coefficient between the arm and the ring-shaped waveguide due to the change in the width of the waveguide along the arm is a directional coupling waveguide. Is smaller than that of the MMI waveguide. Therefore, when the waveguide portion is formed of the MMI waveguide, the coupling coefficient can be changed more largely by changing the width of the waveguide along the arm portion.
  • the first waveguide unit 10 has the embedded waveguide structure as the first waveguide structure, but the first waveguide unit is the first waveguide structure. It may have a ridge waveguide structure as a waveguide structure.
  • FIG. 10 is a diagram for explaining an example of the first waveguide section having a ridge waveguide structure.
  • FIG. 10 is a cross-sectional view of a portion of the first waveguide unit 10A including the phase adjustment unit 11Ab cut along the xy plane of FIG.
  • the first waveguide portion 10A is a portion including the phase adjustment portion 11Ab, the lower cladding layer 12Aa made of p-type InP, the phase adjustment portion 11Ab being an optical waveguide layer made of InGaAsP, and the upper portion made of n-type InP It has a structure in which the ridge cladding layer 12Ab is sequentially stacked.
  • the first waveguide portion may have a ridge waveguide structure.
  • FIG. 11 is a schematic perspective view of the wavelength tunable laser device according to the second embodiment.
  • the tunable laser device 100A according to the second embodiment includes the tunable laser device 100 according to the first embodiment shown in FIG. 1 and a semiconductor amplifier (SOA) formed on a base B. And 101.
  • the SOA 101 has a buried waveguide structure including an active core layer made of the same material and structure as the first waveguide portion. However, no diffraction grating layer is provided.
  • the tunable laser element 100 and the SOA 101 are optically coupled by a space coupling optical system (not shown).
  • the laser beam L1 output from the wavelength tunable laser device 100 is input to the SOA 101.
  • the SOA 101 optically amplifies the laser beam L1 and outputs it as a laser beam L2.
  • the wavelength tunable laser device 100A according to the second embodiment realizes narrowing of the width of the laser beam and stable single mode oscillation, and further, Since the SOA 101 is provided, laser light can be output at higher power.
  • the tunable laser device 100A In the tunable laser device 100A according to the second embodiment, the tunable laser device 100 and the SOA 101 are optically coupled by a space coupling optical system (not shown). However, the tunable laser device 100 and the SOA 101 May be monolithically formed on the common base B.
  • the third embodiment is different from the first and second embodiments in that the second waveguide portion is formed of a silicon (Si) photonic waveguide.
  • FIG. 12A and 12B are schematic views of a wavelength tunable laser device according to a third embodiment.
  • 12A is a perspective view
  • FIG. 12B is a cross-sectional view to be described later.
  • the wavelength tunable laser device 200 is configured to emit a laser beam by performing laser oscillation in a 1.55 ⁇ m band.
  • the wavelength tunable laser device 200 includes a first waveguide section 210 and a second waveguide section 220.
  • the first waveguide unit 210 includes a waveguide unit 211, a semiconductor laminated unit 212, an n-side electrode 213, and a micro heater 215.
  • the waveguide portion 211 is formed to extend in the z direction in the semiconductor laminated portion 212.
  • a gain portion 211a and a DBR diffraction grating layer 211b are disposed in the first waveguide portion 210.
  • the semiconductor laminated portion 212 is configured by laminating semiconductor layers, and has a function of a cladding portion and the like with respect to the waveguide portion 211.
  • the gain portion 211a has a multiple quantum well structure made of the same material as that of the active core layer 11aa in the first embodiment, and a light confinement layer.
  • the diffraction grating layer 211 b is configured by a sampling diffraction grating made of the same material as the diffraction grating layer 11 ab in the first embodiment.
  • the semiconductor multilayer portion 212 is made of the same material and structure as the portion including the diffraction grating loaded type gain portion 11a of the semiconductor multilayer portion 12 in the first embodiment.
  • the lattice layer 11ab is replaced by a p-type InP layer, and that it has a laminated structure in which the positions of the p-type semiconductor layer and the n-type semiconductor layer are reversed with the gain portion 211a in the y direction.
  • the semiconductor multilayer portion 212 is made of the same material and structure as the portion including the phase adjustment portion 11b of the semiconductor multilayer portion 12 in the first embodiment. It differs in that it has a laminated structure in which the positions of the p-type semiconductor layer and the n-type semiconductor layer are reversed with the phase adjustment portion 11 b interposed therebetween.
  • the first waveguide portion 210 has a buried waveguide structure as a first waveguide structure.
  • the n-side electrode 213 is disposed on the semiconductor multilayer portion 212 along the gain portion 211 a.
  • a SiN protective film is formed on the semiconductor laminated portion 212, and the n-side electrode 213 is in contact with the semiconductor laminated portion 212 through an opening formed in the SiN protective film.
  • the microheater 215 as the first refractive index changer is disposed on the SiN protective film of the semiconductor multilayer portion 212 so as to be along the diffraction grating layer 211b.
  • a p-side electrode (not shown) is formed on the surface of the semiconductor laminate portion 212 opposite to the surface on which the n-side electrode 213 is formed.
  • the second waveguide unit 220 is configured of an SOI (Silicon On Insulator) substrate S.
  • the second waveguide portion 220 includes a bifurcated portion 221, arm portions 222 and 223, a ring-shaped waveguide 224, microheaters 225 and 229, a phase adjusting portion 228, and an overcladding layer 230 made of SiO 2. And have.
  • the bifurcated portion 221 is composed of a 1 ⁇ 2 type branched waveguide including a 1 ⁇ 2 type MMI waveguide 221a, and the 2 port side is connected to each of the two arm portions 222 and 223 and the 1 port side is It is connected to the side of the first waveguide unit 210 via the phase adjustment unit 228.
  • One end of the two arm portions 222 and 223 is integrated by the bifurcated portion 221, and is optically coupled to the diffraction grating layer 211b.
  • a tapered section whose width is narrowed toward the first waveguide section 210 is formed.
  • An overcladding layer having a refractive index higher than that of SiO 2 , for example, made of SiN is formed on the outer periphery of the tapered portion, forming a spot size converter structure.
  • Each of the arm portions 222 and 223 extends in the z direction and is disposed so as to sandwich the ring waveguide 224.
  • the arm portions 222 and 223 are in close proximity to the ring waveguide 224 and both are optically coupled to the ring waveguide 224 with the same coupling coefficient ⁇ .
  • the arm units 222 and 223 and the ring waveguide 224 constitute a ring resonator filter RF2.
  • the ring resonator filter RF2 and the bifurcated portion 221 constitute a reflection mirror M2.
  • the microheater 225 as a second refractive index changer is ring-shaped, and is disposed on the over cladding layer 230 directly above the ring-shaped waveguide 224. Further, the microheater 229 is disposed on the over cladding layer 230 along the phase adjustment unit 228.
  • FIG. 12B is a cross-sectional view of the arm portion 222 of the second waveguide portion 220 taken along a plane parallel to the xy plane of FIG. 12A.
  • the arm portion 222 is composed of a support layer 222aa made of a Si support substrate of the SOI substrate S, and a BOX (Buried OXide) layer 222ab made of SiO 2 located on the support layer 222aa. It has a high mesa waveguide structure comprising a lower layer 222a and a device layer 222b made of Si located in the BOX layer 222ab.
  • the device layer 222 b functions as an optical waveguide layer, and the high mesa waveguide structure is covered with the over cladding layer 230.
  • the other components of the second waveguide 220 that is, the 2-branch 221, the arm 223, the ring waveguide 224, and the phase adjuster 228 also have a high mesa waveguide structure. That is, the second waveguide part 220 has a second waveguide structure different from the first waveguide structure of the first waveguide part 210.
  • the first waveguide section 210 is separately manufactured by a known method as a gain chip, and the device layer, the BOX layer, and part of the support substrate are removed in the SOI substrate S constituting the second waveguide section 220. Mounted in the concave portion CC formed by At this time, the gain portion 211 a of the first waveguide portion 210 and the phase adjustment portion 228 of the second waveguide portion 220 are butt-jointed.
  • the first waveguide section 210 and the second waveguide section 220 constitute a laser resonator C2 configured of a diffraction grating layer 211b optically connected to each other and a reflection mirror M2.
  • the gain unit 211a and the phase adjustment unit 228 are disposed in the laser resonator C2.
  • the diffraction grating layer 211b generates a first comb-like reflection spectrum having substantially periodic reflection characteristics at substantially predetermined wavelength intervals.
  • the ring resonator filter RF2 has a peak with a full width at half maximum narrower than the full width at half maximum of the spectral component of the first comb-like reflection spectrum, and has a substantially different wavelength interval from the wavelength interval of the first comb-like reflection spectrum.
  • a second comb-like reflection spectrum having periodic reflection characteristics is generated.
  • laser oscillation occurs at a wavelength at which the peak of the first comb reflection spectrum, the peak of the second comb reflection spectrum, and one of the resonator modes of the laser resonator C2 coincide with each other.
  • the spacing between the modes of the resonator modes of the laser resonator C2 is narrower than the full width at half maximum of the spectral component of the first comb reflection spectrum.
  • the optical feedback in the laser resonator C2 is from the diffraction grating layer 211b, one of the two branches 221, one of the arms 222 and 223 of the ring resonator filter RF2, the ring waveguide 224, the arm 222, The other of 223 is conducted in a path which is returned to the diffraction grating layer 211 b via the 2-branch portion 221 in order, and is circulated in the ring waveguide 224 during one optical feedback.
  • the optical feedback length becomes long, and therefore it is possible to effectively narrow the line width of the laser beam. Further, as in the first and second embodiments, stable single mode oscillation can be realized.
  • the laser oscillation wavelength is the same as in the first and second embodiments by the microheater 215 for the diffraction grating layer 211b and the microheater 225 for the ring resonator filter RF2. Tuning by adjusting the comb-like reflection spectrum and the second comb-like reflection spectrum by tuning the resonator length with the micro heater 229 for the coarse adjustment by the micro heater 229 for the phase adjustment unit 228. To be realized.
  • the wavelength tunable laser 200 of the third embodiment as in the first and second embodiments, the line width reduction of the laser light and the stable single mode oscillation can be realized. Furthermore, in the wavelength tunable laser device 200, the second waveguide portion 220 is configured of a Si photonics waveguide.
  • the Si photonics waveguide is resistant to bending because the waveguide confinement is strong. Therefore, the ring waveguide 224 with a small diameter can be easily realized. This means that a ring waveguide 224 with a large FSR can be realized, and the design freedom of the ring resonator filter RF2 is improved.
  • the wavelength tunable laser device 200 it is possible to output a laser beam having a small footprint and compact size, and a high side mode suppression ratio.
  • the Si waveguide pattern in the second waveguide portion 220 is transferred onto the SOI substrate using photolithography.
  • the device layer and the BOX layer are etched using, for example, HBr gas to obtain a channel waveguide structure.
  • thermal oxidation without using water vapor may be performed in order to reduce the side roughness of the waveguide generated by the etching.
  • a SiN layer is deposited on the entire surface, and an overcladding layer made of SiN is formed on the portion of the spot size conversion structure described above by photolithography and etching.
  • an SiO 2 layer to be an overcladding layer 230 is deposited on the entire surface.
  • the 1st waveguide part 210 which is a gain chip is not limited to what was mentioned above.
  • it may have a quantum well structure or a quantum dot structure on an InP or GaAs substrate.
  • III-V group compound semiconductors such as InGaAs, InGaAsN, AlInGaAs, InGaAs, etc. can be used.
  • InAs, InGaA, or other III-V compound semiconductor can be used as a compound semiconductor material forming the quantum dot structure.
  • Embodiment 4 Next, the fourth embodiment will be described.
  • the second waveguide portion is made of a silicon Si photonics waveguide, the point that a diffraction grating is provided in the second waveguide portion, and the first waveguide
  • the third embodiment differs from the third embodiment in that the section includes a U-shaped waveguide.
  • FIG. 13 is a schematic perspective view of the wavelength tunable laser device according to the fourth embodiment.
  • the tunable laser device 300 is configured to emit a laser beam by performing laser oscillation in a 1.55 ⁇ m band.
  • the wavelength tunable laser device 300 includes a first waveguide section 310 and a second waveguide section 320.
  • the first waveguide unit 310 includes a waveguide unit 311, a semiconductor multilayer unit 312, and an n-side electrode 313.
  • the waveguide portion 311 is formed in a U-shape in which a part thereof extends in the z direction in the semiconductor laminated portion 312.
  • a gain portion 311a and an optical waveguide layer 311b are disposed in the first waveguide portion 310.
  • the semiconductor laminated portion 312 is configured by laminating semiconductor layers, and has a function of a cladding portion and the like with respect to the waveguide portion 311.
  • Gain portion 311a extends in the z direction, and has a multiple quantum well structure made of the same material as active core layer 11aa in the first embodiment.
  • the optical waveguide layer 311 b is made of the same material as that of the phase adjustment unit 11 b in the first embodiment, and forms a U-shape together with the gain unit 311 a.
  • the semiconductor multilayer portion 312 is made of the same material and structure as the portion including the grating loading type gain portion 11a of the semiconductor multilayer portion 12 in the first embodiment.
  • the lattice layer 11ab is replaced with a p-type InP layer, and that the layer structure has a laminated structure in which the positions of the p-type semiconductor layer and the n-type semiconductor layer are reversed with the gain portion 311a in the y direction.
  • the semiconductor multilayer portion 312 is made of the same material and structure as the portion including the phase adjustment portion 11 b of the semiconductor multilayer portion 12 in the first embodiment. It differs in that it has a stacked structure in which the positions of the p-type semiconductor layer and the n-type semiconductor layer are reversed with the gain portion 311 a interposed therebetween.
  • the first waveguide portion 310 has a buried waveguide structure as a first waveguide structure.
  • the n-side electrode 313 is disposed on the semiconductor multilayer portion 312 along the gain portion 311 a.
  • a SiN protective film is formed on the semiconductor laminated portion 312 so as to cover the semiconductor laminated portion 312, and the n-side electrode 313 is in contact with the semiconductor laminated portion 312 through the opening formed in the SiN protective film.
  • a p-side electrode (not shown) is formed on the surface of the semiconductor lamination portion 312 opposite to the surface on which the n-side electrode 313 is formed.
  • the second waveguide section 320 is configured of an SOI substrate.
  • the second waveguide portion 320 is an overcladding made of a bifurcated portion 321, arm portions 322 and 323, a ring-shaped waveguide 324, microheaters 325, 329 and 333, a phase adjusting portion 328, and SiO 2.
  • a layer 330, a waveguide portion 331, and a diffraction grating portion 332 are provided.
  • the bifurcated portion 321 is composed of a 1 ⁇ 2 type branched waveguide including a 1 ⁇ 2 type MMI waveguide 321a, and the 2 port side is connected to each of the two arm portions 322 and 323 and the 1 port side is It is connected to the gain section 311 a side of the first waveguide section 310.
  • One end of the two arm portions 322 and 323 is integrated by the bifurcated portion 321, and is optically coupled to the diffraction grating portion 332.
  • a tapered portion whose width is narrowed toward the first waveguide portion 310 is formed.
  • An overcladding layer having a refractive index higher than that of SiO 2 , for example, made of SiN is formed on the outer periphery of the tapered portion, forming a spot size converter structure.
  • Each of the arm portions 322 and 323 extends in the z direction, and is disposed to sandwich the ring waveguide 324.
  • the arm portions 322 and 323 are in close proximity to the ring waveguide 324 and both are optically coupled to the ring waveguide 324 with the same coupling coefficient ⁇ .
  • the arm portions 322 and 323 and the ring waveguide 324 constitute a ring resonator filter RF3.
  • the ring resonator filter RF3 and the bifurcated portion 321 constitute a reflection mirror M3.
  • the microheater 325 as a second refractive index changer is ring-shaped, and is disposed on the over cladding layer 330 directly above the ring-shaped waveguide 324.
  • the waveguide portion 331 is a waveguide extending in the z direction, one end of which is connected to the optical waveguide layer 311b side of the first waveguide portion 310, and the other end of which is connected to the diffraction grating portion 332.
  • a phase adjustment unit 328 is provided in the middle of the waveguide unit 331.
  • the micro heater 329 is disposed on the over cladding layer 330 along the phase adjustment unit 328.
  • the microheater 333 as a first refractive index changer is disposed on the over cladding layer 330 along the diffraction grating portion 332.
  • the second waveguide section 320 has a second waveguide structure different from the first waveguide structure of the first waveguide section 310.
  • the diffraction grating section 332 has a configuration in which a sampling diffraction grating is formed along the z direction in a device layer functioning as an optical waveguide layer, and the grooves of the diffraction grating are embedded with SiO 2 of the over cladding layer 330.
  • the first waveguide section 310 is separately manufactured by a known method as a gain chip, and the device layer, the BOX layer, and part of the support substrate are removed in the SOI substrate constituting the second waveguide section 320.
  • the gain section 311 a of the first waveguide section 310 and one port side of the 2-branch section 321 of the second waveguide section 320 are butt-joint connected, and the optical waveguide layer of the first waveguide section 310
  • the butt joint connection 311 b and the waveguide part 331 of the second waveguide part 320 are connected.
  • one port side of the 2-branch portion 321 of the second waveguide portion 320 and the waveguide portion 331 of the second waveguide portion 320 are the first waveguide portion. It is preferable that a tapered portion whose width decreases toward 310 is formed, and an overcladding layer made of, for example, SiN is formed on the outer periphery thereof to form a spot size converter structure.
  • the first waveguide section 310 and the second waveguide section 320 constitute a laser resonator C3 constituted of a diffraction grating section 332 and a reflection mirror M3 optically connected to each other.
  • the gain unit 311a and the phase adjustment unit 328 are disposed in the laser resonator C3.
  • the diffraction grating section 332 generates a first comb-like reflection spectrum having substantially periodic reflection characteristics at substantially predetermined wavelength intervals.
  • the ring resonator filter RF3 has a peak with a full width at half maximum narrower than the full width at half maximum of the peak of the first comb reflection spectrum, and has a substantially periodicity at a wavelength interval different from the wavelength interval of the first comb reflection spectrum. Generating a second comb-like reflection spectrum having a characteristic reflection characteristic.
  • laser oscillation occurs at a wavelength at which the peak of the first comb reflection spectrum, the peak of the second comb reflection spectrum, and one of the resonator modes of the laser resonator C3 coincide.
  • the spacing between the modes of the resonator modes of the laser resonator C3 is narrower than the full width at half maximum of the spectral component of the first comb reflection spectrum.
  • the optical feedback in the laser resonator C3 is from the diffraction grating section 332, one of the two branches 321, one of the arms 322 and 323 of the ring resonator filter RF3, the ring waveguide 324, the arm 322, In the other of H.323, it is performed in the path which returns to the diffraction grating part 332 via the 2-branch part 321 in order, and goes around in the ring waveguide 324 during one optical feedback.
  • the wavelength tunable laser device 300 according to the fourth embodiment can realize narrowing of the line width of laser light and stable single mode oscillation.
  • the laser oscillation wavelength is the same as in the first and second embodiments by the micro heater 333 for the diffraction grating section 332 and the micro heater 325 for the ring resonator filter RF3. Can be tuned by tuning the comb-like reflection spectrum and the second comb-like reflection spectrum separately, and fine tuning by tuning the resonator length with the micro heater 329 for the phase adjustment unit 328. To be realized.
  • the tunable laser device 300 can also be manufactured in the same manner as the tunable laser device 200 according to the third embodiment. That is, a portion related to the second waveguide portion 320 is manufactured using the SOI substrate, and the separately manufactured first waveguide portion 310 is mounted on the concave portion CC by flip chip bonding. Thus, the wavelength tunable laser device 300 is completed.
  • the wavelength tunable laser device 300 as in the first and second embodiments, it is possible to realize narrowing of the line width of the laser light and stable single mode oscillation, and Similarly, it is possible to output a laser beam which has a small footprint and is compact and has a high side mode suppression ratio.
  • FIG. 14 is a schematic view of a laser module according to the fifth embodiment.
  • the laser module 1000 includes the wavelength tunable laser element 100A according to the second embodiment, a collimator lens 1001, an optical isolator 1002, a beam splitter 1003, a condenser lens 1005, an optical fiber 1006, and a power monitor as a light receiving element.
  • a PD (Photo Diode) power monitor PD 1009, an etalon filter 1010, and a power monitor PD 1011 are provided.
  • the wavelength tunable laser device 100A is mounted on an electronic cooling device (not shown) for adjusting the temperature of the wavelength tunable laser device 100A.
  • the wavelength tunable laser device 100A, the power monitors PD 1009 and 1011 and the electronic cooling device are connected to an external control unit.
  • the wavelength tunable laser device 100A is supplied with a drive current from the control unit, and the diffraction grating layer 11ab adjusted by controlling the micro heaters 14, 15, 25 by the control unit, the ring resonator filter RF1, the phase adjustment unit 11b, etc.
  • the laser light of the wavelength determined under the conditions of (1) is amplified to a desired output intensity by the SOA 101 and output as a laser light L2.
  • the collimator lens 1001 converts the laser beam L2 output from the wavelength tunable laser element 100A into a parallel beam.
  • the optical isolator 1002 transmits the laser beam L2 collimated by the collimator lens 1001 only in one direction.
  • the beam splitter 1003 branches a part to the power monitor PD 1009 side while transmitting most of the laser light L 2 transmitted through the optical isolator 1002.
  • the power monitor PD 1009 receives part of the laser beam L2 branched by the beam splitter 1008, and outputs a current having a value according to the light reception intensity.
  • the etalon filter 1010 has a transmission wavelength characteristic having a periodically changing peak according to the order of multiple interference, and the laser light L2 transmitted through the beam splitter 1008 according to the transmission wavelength characteristic at the wavelength of the laser light L2 It penetrates with a high transmittance.
  • the period of the etalon filter 1010 is, for example, 50 GHz at the frequency of light.
  • the power monitor PD1011 receives the laser beam L2 transmitted through the etalon filter 1010, and outputs a current having a value according to the light reception intensity.
  • the condensing lens 1005 condenses the laser beam L2 transmitted through the beam splitter 1003 and couples it to the optical fiber 1006.
  • the optical fiber 1006 propagates the coupled laser light L2 to the outside.
  • the laser light L2 is used, for example, as signal light for optical fiber communication.
  • the etalon filter 1010 uses a bulk filter, a waveguide filter may be used instead.
  • the control unit controls the ratio of the intensity of the laser light monitored by the power monitor PD 1009 to the intensity of the laser light after transmission through the etalon filter 1010 monitored by the power monitor PD 1011 Control is performed to change the drive current and temperature of the wavelength tunable laser element 100A such that the ratio when the wavelength of the laser light L2 becomes a desired wavelength is obtained.
  • the wavelength of the laser beam L2 can be controlled to a desired wavelength (lock wavelength).
  • FIG. 15 is a schematic view of a laser module according to the sixth embodiment.
  • the laser module 1000A includes a wavelength tunable laser element 100B, a collimator lens 1001, an optical isolator 1002, a beam splitter 1003, a power monitor PD 1004, a condenser lens 1005, an optical fiber 1006, a collimator lens 1007, a beam splitter A power monitor PD 1009, an etalon filter 1010, and a power monitor PD 1011 are provided.
  • the wavelength tunable laser device 100B is mounted on an electronic cooling device (not shown) for adjusting the temperature of the wavelength tunable laser device 100B.
  • the wavelength tunable laser device 100B, the power monitors PD 1004, 1009, 1011 and the electronic cooling device are connected to an external control unit.
  • the functions of the collimator lens 1001, the optical isolator 1002, the beam splitter 1003, the power monitor PD 1004, the condenser lens 1005, and the optical fiber 1006 are the same as those of the laser module 1000, and therefore the description thereof is omitted.
  • the wavelength tunable laser device 100B has a coupling coefficient ⁇ 1 between the arm portion 22 and the ring waveguide 24 and a coupling coefficient between the arm portion 23 and the ring waveguide 24. It is designed such that ⁇ 2 has different values. As described above, by setting the coupling coefficients ⁇ 1 and ⁇ 2 to different values, the ring resonator filter RF1 becomes an asymmetric filter, and a part of the oscillated laser light is connected to the two branch parts 21 of the arm parts 22 and 23. It will be outputted from the end face opposite to the other side.
  • the collimator lens 1007 converts the laser beam L3 which is a part of the oscillated laser beam, which is output from the end face of the arm portion 22, into parallel rays.
  • the beam splitter 1008 transmits most of the laser beam L3 that has been made a parallel beam and branches a portion to the power monitor PD 1009 side.
  • the power monitor PD 1009 receives a part of the laser beam L3 branched by the beam splitter 1008, and outputs a current having a value according to the light reception intensity.
  • the etalon filter 1010 has a transmission wavelength characteristic having a periodically changing peak according to the order of multiple interference, and the laser light L3 transmitted through the beam splitter 1008 according to the transmission wavelength characteristic at the wavelength of the laser light L3.
  • the period of the etalon filter 1010 is, for example, 50 GHz at the frequency of light.
  • the power monitor PD1011 receives the laser beam L3 transmitted through the etalon filter 1010, and outputs a current of a value according to the light reception intensity.
  • the laser module 1000A by providing the wavelength tunable laser device 100B, it is possible to realize narrowing of the line width of the laser light L2 and stable single mode oscillation, and to output the laser light L2 with higher power. Furthermore, the received light intensity can be monitored by monitoring the current output from the power monitors PD 1009 and 1011, and wavelength lock control can be performed by the control unit. Furthermore, since the intensity of the laser beam L2 can be monitored by monitoring the current output from the power monitor PD 1004, power feedback control can be performed by the control unit.
  • the control unit controls the ratio of the intensity of the laser light monitored by the power monitor PD 1009 to the intensity of the laser light after transmission through the etalon filter 1010 monitored by the power monitor PD 1011 Control is performed to change the drive current and temperature of the wavelength tunable laser element 100B such that the ratio when the wavelength of the laser beam L2 becomes a desired wavelength is obtained.
  • the wavelength of the laser beam L2 can be controlled to a desired wavelength (lock wavelength).
  • the diffraction grating is a sampling diffraction grating, but the type of diffraction grating is not limited to this, and may be a superstructure diffraction grating or a superimposed diffraction grating.
  • the diffraction grating layer 11ab is provided along and immediately above the active core layer 11aa along the active core layer 11aa, but the present invention is not limited to this.
  • a diffraction grating layer may be provided in the vicinity of the active core layer and directly on the optical waveguide layer.
  • the present invention is not limited by the above embodiment.
  • the present invention also includes those configured by appropriately combining the above-described components. Further, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above embodiment, and various modifications are possible.

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Abstract

L'invention concerne un élément laser à longueur d'onde variable qui comporte : un résonateur laser constitué d'un réseau de diffraction et d'un miroir réfléchissant qui comprend un filtre de résonateur en anneau; une unité de gain; et une unité de réglage de phase. Le réseau de diffraction génère un premier spectre de réflexion en peigne. Le filtre de résonateur en anneau est pourvu d'un guide d'ondes annulaire et de deux parties bras, et génère un second spectre de réflexion en peigne qui diffère du premier spectre de réflexion en peigne en termes d'intervalle de longueur d'onde au niveau d'un pic plus étroit que la largeur à mi-hauteur du premier spectre de réflexion en peigne. Un pic du premier spectre de réflexion en peigne et un pic du second spectre de réflexion en peigne sont superposés sur l'axe de longueur d'onde. L'intervalle entre modes pour un mode de résonateur est une longueur d'onde plus étroite que la largeur à mi-hauteur du pic pour le premier spectre de réflexion en peigne.
PCT/JP2016/053463 2015-03-20 2016-02-05 Élément laser à longueur d'onde variable et module laser WO2016152274A1 (fr)

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CN201680012598.3A CN107431331B (zh) 2015-03-20 2016-02-05 波长可变激光元件以及激光模块
US15/708,994 US10193305B2 (en) 2015-03-20 2017-09-19 Wavelength tunable laser device and laser module

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US201562135991P 2015-03-20 2015-03-20
US62/135,991 2015-03-20
JP2016-008579 2016-01-20
JP2016008579A JP6684094B2 (ja) 2015-03-20 2016-01-20 波長可変レーザ素子およびレーザモジュール

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US11482838B2 (en) 2017-02-07 2022-10-25 Furukawa Electric Co., Ltd. Optical waveguide structure
WO2018146749A1 (fr) * 2017-02-08 2018-08-16 古河電気工業株式会社 Dispositif laser à longueur d'onde variable
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WO2020166615A1 (fr) * 2019-02-14 2020-08-20 古河電気工業株式会社 Dispositif de source de lumière à longueur d'onde variable et procédé de commande d'élément laser à longueur d'onde variable
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