Classifications

• • 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
  • H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
• • 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
  • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
  • H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
• • 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
  • H01S2301/00—Functional characteristics
  • H01S2301/14—Semiconductor lasers with special structural design for lasing in a specific polarisation mode
• • 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
  • H01S2301/00—Functional characteristics
  • H01S2301/17—Semiconductor lasers comprising special layers
  • H01S2301/176—Specific passivation layers on surfaces other than the emission facet
• • 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
  • H01S5/02—Structural details or components not essential to laser action
• • 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
  • H01S5/0607—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature
• • 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
  • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
  • H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
  • H01S5/227—Buried mesa structure ; Striped active layer
  • H01S5/2275—Buried mesa structure ; Striped active layer mesa created by etching

Definitions

• the present invention relates to the amplification of optical signals. It typically finds application in fiber optic telecommunications networks.
• the signals transmitted by these networks consist of pulses carrying in binary form information to be transmitted. ' These pulses must be amplified to compensate for losses of power which they undergo during their propagation in these networks.
• Semiconductor amplifiers constitute a space-saving and integrable means to achieve this amplification. However, in the absence of special provisions, their gain is sensitive to the state of polarization of the light they receive, which will be more simply indicated below by mentioning the sensitivity of an amplifier " to polarization.
• the sensitivity must be limited or suppressed is frequent and appears, on the one hand when the distance traveled by the optical pulses to be amplified is such that the polarization state of these pulses has been affected in a significant and random manner during their spread and on the other hand when it is preferable that the amplified pulses have one or more predetermined power levels.
• this invention finds an application whenever the sensitivity of an optical amplifier to polarization must be zero or limited.
• buried ribbon amplifiers known under the term of BRS (for Burried Ridge Structure in English).
• BRS Burried Ridge Structure in English
• a semiconductor optical amplifier comprises a wafer 2 made up of layers of semiconductor materials having respective refractive indices and forming a common crystal lattice.
• networks formed respectively by these materials have characteristic dimensions constituting respective meshes of these materials.
• These layers follow one another in a vertical direction DV forming a trirectangle trihedron with two horizontal directions constituting a direction. longitudinal DL and a transverse direction DT, these directions being defined with respect to this plate 2.
• This plate 2 comprises at minus the following layers or groups of layers or part of a layer:
• a substrate 8 consisting mainly of a semiconductor base material having a first type of conductivity. This substrate has a sufficient thickness to impose the dimensions of the mesh of the base material on the entire crystal lattice of the wafer 2.
• An active layer 10 including an active material capable of amplifying light by stimulated recombination of charge carriers of the two types injected into this material.
• a buried guiding active structure 12 produced in the active layer 10 and having a refractive index greater than that of the surrounding materials 14, 16.
• This active structure 12 extends in the longitudinal direction DL to guide said light in this direction. It has a width 1 and a thickness e respectively transverse and vertical.
• an upper confinement layer 18 made of a material having a second type of conductivity opposite to the first.
• This amplifier further comprises a lower electrode 20 and an upper electrode 22 respectively formed on the lower face 4 and the upper face 6 of the wafer 2 to allow an electric current to pass between these faces injecting said charge carriers of the two types into the active material 10.
• the basic materials of known semiconductor optical amplifiers are of the III-V type. These are typically indium phosphide and gallium arsenide. Their active material is typically a ternary or quaternary material formed with the same chemical elements. It is generally desired that the width 1 of the active guiding structure 12 which guides the lights be close to a micrometer to facilitate its formation by etching and above all to facilitate the integration of the amplifier with other optical components on the same semiconductor wafer.
• the thickness e must then be much less than this width 1 to ensure mononodal light guidance, the wavelength of which is typically 1310 or 1550 nm. In the absence of special provisions, it is this rectangular shape of the section of the active guiding structure 12 which tends to cause the polarization sensitivity previously mentioned.
• the active material 10 constituting the active structure 12 guiding the light is surrounded on all sides by a binary semiconductor material. The latter has the advantage of conducting heat well, but its refractive index is only slightly lower than that of the active material. We also consider the case where the active material is homogeneous and is then said to be mass.
• the section of the buried active guiding structure 12 is strongly rectangular. Given the small difference in index between this guiding structure 12 and the binary material surrounding the confinement of a horizontally polarized wave is greater than that of a vertically polarized wave, the difference between these two confinements being all the greater as the ratio of the width 1 to the thickness e of the guide structure 12 is large.
• the confinement mentioned here in connection with a wave is considered in a transverse plane. It is equal to the ratio of the power of this wave passing through the area occupied by the guiding structure 12 to the total power of this wave.
• the confinement is defined for each polarization and for each wavelength by the shape and the dimensions of the section of the guiding active structure 12 and by the refractive indices of the material of this structure 12 and of the surrounding materials 14, 16, 8 and 18.
• a rectangular section it can be considered to be the product of a directional confinement in the horizontal direction by a directional confinement in the vertical direction, each of these two directional confinements depending on the polarization.
• the gain of the amplifier for a wave the greater the confinement of this wave.
• the gain of the amplifier would be greater for the waves at horizontal polarization and only for those with vertical polarization.
• Such an amplifier has a low sensitivity to polarization.
• a modification of this constraint ( ⁇ a / a) from -0.015 to -0.014 or -0.016 induces a shift in the gain ⁇ G of 0.8dB towards a respective sensitivity of TE mode or TM mode.
• a slight modification of a few percent of the thickness of the guiding active structure directly induces a shift in the gain ⁇ G of the amplifier.
• the sensitivity to light polarization of the amplifier depends on its structure and cannot be easily controlled.
• the object of the present invention is to solve the drawbacks of the technology proposed in the aforementioned patent US 5,982,531.
• the invention starts from the theoretical and experimental observation that the sensitivity of an optical semiconductor amplifier to the polarization of the light to be amplified does not depend solely on the geometry of the active guiding structure and the internal constraints to which it can be subjected (such as a mesh mismatch), but also external constraints applied to this active guiding structure, for example during the implementation or the use of the optical component.
• the invention proposes to apply to the amplifier component an induced external stress close to the guiding active structure, alone or in combination with the effects of an internal tension stress depending on the epitaxial structure of the active layer as this has been developed in the prior art.
• the external stress can be configured so as to obtain an overall stress of the guiding active structure which makes the gain of the optical amplifier insensitive to the polarization of the light to be amplified.
• the invention relates more particularly to a semiconductor optical amplifier comprising a buried active guiding structure, characterized in that an external stress is applied to said active guiding structure so that it is subjected to an overall stress which makes the gain of said amplifier insensitive to the polarization of the light to be amplified, said external stress coming from a force induced by a deposit of a material against a tape framing said active guiding structure.
• the tape framing the active guiding structure has a depth of between 1 and 4 ⁇ m. According to another characteristic, the tape framing the active guiding structure has a width of between 4 and 6 ⁇ m.
• the material deposited on the ribbon framing the active structure is an oxide.
• the material deposited is Si0 2 for an external compressive stress. According to another embodiment, the material deposited is Si 3 N 4 for an external stress in tension.
• the thickness of the material deposited against the tape framing the active structure is between 0.1 and 0.5 ⁇ m.
• the active guiding structure is subjected to an internal stress due to a mesh mismatch of the semiconductor material, the external stress being an additional stress to this internal stress.
• the invention also relates to a method for manufacturing an optical amplifier in semiconductor, characterized in that it comprises the following steps: - production of an optical amplifier in semiconductor with buried active guiding structure, etching of a ribbon surrounding said active guiding structure, - deposit of an oxide on the contours of the engraved ribbon, realization of an electrode.
• the optical amplifier according to the invention achieves a sensitivity to the polarization of light less than or equal to 1 dB.
• the process of etching the ribbon framing the guiding active structure can be carried out at the end of the process for manufacturing the optical amplifier, according to known techniques which are easy to implement.
• FIG. 1, already described, is a diagram of an optical amplifier in buried ribbon semiconductor according to the prior art.
• - Figure 2 is a diagram of an optical amplifier in semiconductor subjected to external stress according to one invention.
• FIGS. 3a to 3d schematically illustrate the steps for producing the optical amplifier according to the invention.
• the optical amplifier according to the invention has a structure similar to that described with reference to the prior art and in Figure 1.
• the same references will be used to designate the same elements.
• the method of manufacturing such an amplifier therefore comprises the same steps consisting in producing an amplifier with a guiding active structure 12 buried.
• the active guiding structure 12 can be subjected to an internal stress due to a mesh mismatch of the semiconductor material, as has been described with reference to US Pat. No. 5,982,531.
• the invention then consists in supplementing or to compensate for this internal stress by an external stress applied to the active guiding structure 12 so that it is subjected to an overall stress which makes the gain of the amplifier insensitive to the polarization of the light to be amplified.
• the invention then consists in applying an external stress to the active guiding structure 12 so as to that it is subjected to an overall constraint which makes the gain of the amplifier insensitive to the polarization of the light to be amplified.
• the external stress comes from a force induced by a deposit of a material 50 against a strip 15 framing the active guiding structure 12.
• the ribbon 15 framing the active guiding structure 12 is engraved according to any technique known from the prior art. For example, by dry etching through a mask 17, in SiO 2 for example, deposited on the confinement layer 18 of the amplifier.
• the ribbon 15 has a depth between 1 and 4 ⁇ m and a width between 4 and 6 ⁇ m.
• the active guiding structure 12 buried has a width of approximately 2 ⁇ m and is located at a depth of the upper face 6 of the component of between 2 and 4 ⁇ m (for a component of approximately 100 ⁇ m in thickness including the substrate 8).
• the ribbon 15 therefore effectively frames the guiding active structure 12 and the forces exerted on this ribbon 15 will be reflected on the active structure 12 to induce an effect on the overall gain and the sensitivity of the amplifier to the polarization of the light to be amplified.
• the material 50 deposited against the ribbon 15 framing the active structure 12 is an oxide.
• Si0 2 for an external stress in compression (dotted lines in Figure 3c) or Si 3 N 4 for an external stress in tension (solid lines in Figure 3c).
• the thickness of this material 50 is advantageously between 0.1 and 0.5 ⁇ m.
• the parameters making it possible to adjust the external stress on the ribbon 15 framing the active guiding structure 12 of the amplifier are essentially the width and depth of the etching of the ribbon 15, the nature of the material deposited 50 and its thickness.
• An electrode 22 is then produced on the upper face 6 of the optical component, for example by opening the oxide deposit 50 on top of the active structure 12 to deposit a metallization there.
• the metallization can be deposited on the opening of the electrode 22 and over the material 50 of external stress.

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• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Optics & Photonics (AREA)
• Geometry (AREA)
• Semiconductor Lasers (AREA)

Applications Claiming Priority (3)

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• 2000
  • 2000-08-22 FR FR0010820A patent/FR2813450B1/fr not_active Expired - Fee Related
• 2001
  • 2001-08-20 JP JP2002522038A patent/JP2004507893A/ja not_active Withdrawn
  • 2001-08-20 US US10/110,131 patent/US6894833B2/en not_active Expired - Fee Related
  • 2001-08-20 EP EP01963109A patent/EP1314231A1/de not_active Withdrawn
  • 2001-08-20 WO PCT/FR2001/002631 patent/WO2002017453A1/fr not_active Application Discontinuation

Non-Patent Citations (1)

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