WO2002063731A2 - Laser a reflecteur reparti a reseaux echantillonnes - Google Patents

Laser a reflecteur reparti a reseaux echantillonnes Download PDF

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Publication number
WO2002063731A2
WO2002063731A2 PCT/GB2002/000388 GB0200388W WO02063731A2 WO 2002063731 A2 WO2002063731 A2 WO 2002063731A2 GB 0200388 W GB0200388 W GB 0200388W WO 02063731 A2 WO02063731 A2 WO 02063731A2
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WO
WIPO (PCT)
Prior art keywords
grating
section
laser
laser according
burst
Prior art date
Application number
PCT/GB2002/000388
Other languages
English (en)
Other versions
WO2002063731A3 (fr
Inventor
Peter John Williams
David James Robbins
Original Assignee
Bookham Technology Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bookham Technology Plc filed Critical Bookham Technology Plc
Publication of WO2002063731A2 publication Critical patent/WO2002063731A2/fr
Publication of WO2002063731A3 publication Critical patent/WO2002063731A3/fr

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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
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
    • H01S5/0625—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in multi-section lasers
    • H01S5/06255—Controlling the frequency of the radiation
    • H01S5/06256—Controlling the frequency of the radiation with DBR-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
    • 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
    • H01S5/12—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 the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
    • H01S5/1206—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 the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers having a non constant or multiplicity of periods
    • H01S5/1209—Sampled grating

Definitions

  • This invention relates to a sampled grating distributed reflector laser and more especially, although not exclusively, to such a laser for use in optical wavelength division multiplex (WDM) communications.
  • WDM wavelength division multiplex
  • WDM optical communications require laser sources which are capable of selectably producing light of wavelengths corresponding to the WDM channels.
  • early WDM systems having only a few channels, typically eight, it was known to use a separate single wavelength lasers for each channel and to selectively switch between lasers. Each laser was operated continuously to ensure temperature and hence wavelength stability. Although such an arrangement provides an adequate performance for a limited number of channels the demand for ever higher communications capacity has lead to an increase in the number of channels with a consequential decrease in the wavelength spacing of channels making the use of a dedicated single wavelength laser for each wavelength channel impractical.
  • Wavelength tuneable lasers such as sampled grating distributed reflector lasers
  • Figure 1 is a schematic longitudinal sectional representation of a known a sampled Bragg grating distributed reflector laser.
  • the laser 1 comprises four sections: an active section 2 in which light is generated; front and rear sample grating reflector sections 4, 6 bounding the active section 2 and a phase section 8 located between the active section 2 and the rear reflector section 6.
  • Light is generated within the active section and is guided within an optical guiding layer 10.
  • the phase section 8 is used to tune the effective optical cavity length of the laser by the application of an electrical current i PhaS e to an associated electrode 11 to inject carriers into the underlying optical guiding layer and thereby change its refractive index.
  • the front and rear reflector sections 4, 6, each comprise a sampled Bragg grating, that is a plurality of grating bursts 4a-4d, 6a-6d, of constant period that are spaced along the section with a constant period L F , L R respectively.
  • each grating section acts a reflector having a comb of equally wavelength spaced reflection peaks or maxima. The spacing of reflection peaks is determined by the period of the grating bursts and the period L F , L R of the sampled grating.
  • Respective electrodes 12, 16 are provided on a upper surface off the laser and overlay the length of the associated reflector section.
  • the application of an electrical current i F , i R to the electrodes 12, 16 changes the carrier concentration within the guiding layer of the section and thereby changes the refractive index of the reflector section.
  • the change in refractive index displaces the entire comb of reflection peaks in terms of wavelength and is used in combination with the phase section 8 to tune the laser to a selected wavelength of operation.
  • the periods L F , L R of the sample gratings are selected such that the combs have different wavelength spacing of their reflection peaks and are such that only one reflection peak from each comb can coincide at a given time.
  • the wavelength of operation of the laser corresponds to the wavelength at which the reflection peaks coincide.
  • injection currents ip, - R ip h ase are applied to the grating and phase sections.
  • a course wavelength tuning is obtained by displacing one comb relative to the other such that a different pair of peaks coincide and fine wavelength tuning achieved by displacing the two combs by an equal amount.
  • a sampled grating distributed reflector laser comprises: an active section, a phase section and at least one sampled grating section which comprises a plurality of grating bursts distributed along the optical axis of the section such that the section exhibits a comb of reflection maxima and wherein application of electrical current to the at least one grating section and phase section respectively shifts the wavelength of the comb and changes the effective cavity length of the laser thereby enabling tuning of the laser; characterised in that the phase section is spatially separate from the grating section and the at least one grating section is provided with an electrode which comprises a plurality of electrical contacts which overly a respective grating burst and wherein the contacts are configured such that electrical current is substantially localised to the grating bursts.
  • each grating burst is a Bragg grating of constant period.
  • each grating burst is chirped.
  • the laser comprises two sampled grating sections bounding the active and phase sections in which each grating section has comb of reflection maxima whose spacing is selected to be different and wherein the laser is tuned by applying a respective electrical current to each grating section.
  • the laser is fabricated as a surface ridge structure. Alternatively it can be fabricated as a buried ridge structure.
  • the laser is fabricated in a III-N semiconductor material such as an indium phosphide based material or a gallium arsenide based material.
  • Figure 1 is a schematic longitudinal sectional representation of a known sampled grating distributed reflector laser, which has already been described;
  • Figure 2 is a schematic longitudinal sectional representation of a sampled grating distributed reflector laser in accordance with the invention.
  • Figure 3a to 3f illustrate the steps involved in the manufacture of a laser in accordance with the invention.
  • FIG. 2 there is shown a schematic representation of a sampled grating distributed Bragg reflector laser in accordance with the invention.
  • the electrodes for injecting electrical carriers into the front and rear grating sections 4, 6 are discontinuous (segmented) and do not extend over the entire length of the section.
  • a respective electrode segment 20a-20d and 22a-22d is provided for each grating burst which is configured to overlay only the length of the grating bursts to which it is associated. It is to be noted that the electrode segments 20a-20d, 22a-22d for each grating section 4, 6 are electrically connected to together.
  • a respective tuning current i F , i R is applied to the electrode segments of the front and rear grating sections in a known manner to tune the laser's wavelength of operation. Due to the segmented electrode arrangement the injection of carriers within the grating sections is substantially confined to the region of the grating bursts. As a result the current ip, i R required to attain a required carrier density within the grating bursts and is reduced. The inventors have appreciated that it is primarily the current density within the grating bursts that determines the tuning capability of the laser. As a result of the reduction in current this reduces heating and the free carrier absorption loss within the guiding layer 10. Furthermore since in general the optical output power of a sampled grating laser reduces with increasing tuning current, the laser of the present invention provides a higher optical output for a given tuning current and is further found to have a reduced output optical power variation with tuning current.
  • the lengths of the electrode segments 20a-20d, 22a-22d, in a direction along the optical axis of the optical guiding layer, are selected such as to attain a substantially uniform carrier injection within its associated grating burst and will in general therefore be of a length which substantially corresponds to the length of the grating bursts.
  • the electrodes can for optimum performance be shorter or longer than the grating burst.
  • the electrode segments 20a-20d, 22a-22d can be fabricated by selective metahsation or etching, in a preferred embodiment the electrode segments are fabricated by selectively etching windows within a dielectric or other isolation layer on an upper surface of the device and then metalising the entire section.
  • FIGS 3 a- 3 f these illustrate schematically the steps involved in the fabrication of a surface ridge wavelength tuneable sampled grating reflector laser in accordance with a preferred embodiment of the invention.
  • the tuneable laser is preferably fabricated in indium phosphide (InP)/indium gallium arsenide phosphide (InGaAsP).
  • InP indium phosphide
  • InGaAsP indium gallium arsenide phosphide
  • C band operation
  • L L band operation
  • friGaAs/friGaAsP 52 is grown on the substrate to form a quantum well or bulk structure as known in the art.
  • a layer of dielectric material 54 typically silicon dioxide (SiO 2 ), is deposited on top of the layer 52 and is used as an etch stop layer for selectively removing regions of the InGaAs/InGaAsP layers.
  • the InGaAs/hiGaAsP layers 52 are selectively etched to leave an island 56 of remaining material which will comprise the active region 2 of the laser.
  • the regions around the island of material are infilled with InGaAsP 58, 60 by selective area epitaxy ( Figure 3c).
  • the laser can alternatively be fabricated by a non-selective area growth process in which epitaxial layers for both the tuning (grating/reflector and phase) sections are created in a single epitaxial step.
  • These regions 58, 60 respectively comprise the optical guiding layer of the laser with the front grating section 4 being subsequently formed in the region 58 and the rear grating section 6 and phase section 8 being formed in the region 60.
  • a layer of dielectric 62 is deposited over the InGaAsP regions 58, 60 and is used to form the grating bursts 64 of the front and rear grating sections ( Figure 3d).
  • An upper optical confinement layer 66 of InP is then overgrown over the surface of the device followed by a contact layer 68 of p+ InGaAs ( Figure 3e).
  • the contact and confinement layers 66, 68 are etched to form a surface ridge structure to provide lateral (ie in and out of the plane of the paper) confinement of light within the optical guiding layer 10.
  • the contact layer 68 is further selectively etched to leave respective contact areas 68a, 68b, 68c, 68d overlying the front grating, active, phase and rear grating sections.
  • Layer 68 is preferentially also etched to form contact regions substantially overlying only the grating bursts.
  • a further dielectric layer 70 is then deposited and selectively etched to form windows through to the contact layer 68.
  • a respective window is defined for each grating burst 64.
  • the windows overly and are substantially the same length as the associated the grating burst.
  • the respective window extends over substantially the entire length of the section.
  • the front and rear grating, active and phase sections are selectively metalised to form the respective electrodes 12, 16, 14, 11.
  • the laser of the present invention is not restricted to the specific embodiments described and that modifications can be made which are within the scope of the invention.
  • a surface ridge structure can be used to provide lateral confinement of light within the optical guiding layer
  • the invention is suited to other laser structures such as for example a buried ridge structure.
  • the invention is further suited to lasers fabricated in other material systems such as other III- N semiconductor material systems such as gallium arsenide/gallium aluminium arsenide.
  • the use of a sampled grating having grating bursts of a constant period is preferred other forms of sampled grating can be used such as those having grating bursts whose period is chirped.
  • the invention has been described in relation to a laser having two sampled grating reflectors it is envisaged to use segmented electrodes for a laser having a single sampled grating reflector.

Abstract

Selon cette invention, un laser à réflecteur réparti à réseaux échantillonnés comprend une section active (2), une section de phase (8) et au moins une section de réseau d'échantillonnage (4, 6). La section d'échantillonnage ou chaque section d'échantillonnage comprend une pluralité de réseaux partiels («grating bursts») répartis le long de l'axe optique de la section, de manière que la section présente un peigne de maxima de réflexion, et qu'elle soit telle que l'application d'un courant électrique respectif (iF, iR et iphase) à la section de réseau (4, 6) et à la section de phase (8) décale la longueur d'onde du peigne et change la longueur de cavité efficace du laser permettant ainsi l'accordage du laser. Ce laser est caractérisé en que qu'au moins une section de réseau (4, 6) possède une électrode (12, 16) comprenant une pluralité de contacts électriques (20a-20d, 22a-22d) qui recouvrent un réseau partiel respectif. Les dimensions des contacts (20a-20d, 22a-22d) sont choisies de manière que le courant électrique soit sensiblement localisé au niveau des réseaux partiels.
PCT/GB2002/000388 2001-02-02 2002-01-29 Laser a reflecteur reparti a reseaux echantillonnes WO2002063731A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0102611.1 2001-02-02
GB0102611A GB2371920A (en) 2001-02-02 2001-02-02 Sampled Gating Distribiuted Reflector Laser

Publications (2)

Publication Number Publication Date
WO2002063731A2 true WO2002063731A2 (fr) 2002-08-15
WO2002063731A3 WO2002063731A3 (fr) 2003-10-30

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GB (1) GB2371920A (fr)
WO (1) WO2002063731A2 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107453202A (zh) * 2017-07-01 2017-12-08 武汉电信器件有限公司 一种热隔离的可调谐dbr激光器及其加工方法和使用方法
WO2021036856A1 (fr) * 2019-08-30 2021-03-04 华为技术有限公司 Laser à longueurs d'onde multiples et procédé de commande de longueurs d'onde

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2377545A (en) 2001-07-14 2003-01-15 Marconi Caswell Ltd Tuneable Laser
US8238388B2 (en) 2006-09-20 2012-08-07 The Provost, Fellows And Scholars Of The College Of The Holy And Undivided Trinity Of Queen Elizabeth Near Dublin Tunable laser device and a method for producing light of respective selectable wavelengths
EP2431775A1 (fr) * 2010-09-16 2012-03-21 Alcatel Lucent Réseaux entrelacés échantillonnés pour spectre de réflectivité multi-crêtes
US8861556B2 (en) * 2012-07-05 2014-10-14 Jds Uniphase Corporation Tunable Bragg grating and a tunable laser diode using same
US9997890B2 (en) 2015-10-28 2018-06-12 Rockley Photonics Limited Discrete wavelength tunable laser
US9627851B1 (en) 2015-10-28 2017-04-18 Rockley Photonics Limited Discrete wavelength tunable laser

Citations (3)

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Publication number Priority date Publication date Assignee Title
US4885753A (en) * 1987-10-09 1989-12-05 Hitachi, Ltd. Semiconductor laser device of variable wavelength type
EP0559192A2 (fr) * 1992-03-06 1993-09-08 Nippon Telegraph And Telephone Corporation Réflecteur distribué et laser à semi-conducteur à longeur d'onde accordable
GB2303739A (en) * 1995-07-25 1997-02-26 France Telecom Widely matchable sample grating distributed Bragg reflector laser

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2197531B (en) * 1986-11-08 1991-02-06 Stc Plc Distributed feedback laser

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4885753A (en) * 1987-10-09 1989-12-05 Hitachi, Ltd. Semiconductor laser device of variable wavelength type
EP0559192A2 (fr) * 1992-03-06 1993-09-08 Nippon Telegraph And Telephone Corporation Réflecteur distribué et laser à semi-conducteur à longeur d'onde accordable
GB2303739A (en) * 1995-07-25 1997-02-26 France Telecom Widely matchable sample grating distributed Bragg reflector laser

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BIERNACKI P D ET AL: "A HIGH-SPEED MIXED DIGITAL-TO-ANALOG CIRCUIT BOARD FOR ACCURATE CONTROL OF WAVELENGTH TUNALBLE LASERS FOR FIBER-OPTIC COMMUNICATIONS" JOURNAL OF LIGHTWAVE TECHNOLOGY, IEEE. NEW YORK, US, vol. 17, no. 7, July 1999 (1999-07), pages 1222-1228, XP000898385 ISSN: 0733-8724 *
KOTAKI Y ET AL: "WAVELENGTH TUNABLE DFB AND DBR LASERS FOR COHERENT OPTICAL FIBRE COMMUNICATIONS" IEE PROCEEDINGS J. OPTOELECTRONICS, INSTITUTION OF ELECTRICAL ENGINEERS. STEVENAGE, GB, vol. 138, no. 2, 1 April 1991 (1991-04-01), pages 171-177, XP000226521 ISSN: 0267-3932 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107453202A (zh) * 2017-07-01 2017-12-08 武汉电信器件有限公司 一种热隔离的可调谐dbr激光器及其加工方法和使用方法
CN107453202B (zh) * 2017-07-01 2019-06-04 武汉电信器件有限公司 一种热隔离的可调谐dbr激光器及其加工方法和使用方法
WO2021036856A1 (fr) * 2019-08-30 2021-03-04 华为技术有限公司 Laser à longueurs d'onde multiples et procédé de commande de longueurs d'onde

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Publication number Publication date
GB0102611D0 (en) 2001-03-21
GB2371920A (en) 2002-08-07
WO2002063731A3 (fr) 2003-10-30

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