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Tunable Lasers in Optical Communications. By James Harper Instructor: P. Lui Department of Electrical Engineering University at Buffalo State University of New York Course Requirement for EE 566. Outline. Introduction Tuning Mechanisms Distributed Bragg Reflector Lasers

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Tunable lasers in optical communications

Tunable Lasers in OpticalCommunications


James Harper

Instructor: P. Lui

Department of Electrical Engineering

University at Buffalo State University of New York

Course Requirement for EE 566


  • Introduction

  • Tuning Mechanisms

  • Distributed Bragg Reflector Lasers

  • External Cavity Tunable Lasers

  • Vertical Cavity Surface Emitting Lasers

  • Types of Vertical Cavity Surface Emitting Lasers

  • Future Applications

  • Economical Impact


  • Most tunable lasers consist of a longitudinal integration of sections

    • Active section provides optical gain

    • Filter section provides a tunable frequency

    • Phase shifter section is for fine-tuning of the cavity resonance frequency

  • The problem of Metro Area Networks

Tuning mechanisms
Tuning Mechanisms

  • Electric field-induce index change

    • An electrical field is applied that changes the refractive index of the waveguide

  • Thermally-induced index change

    • Heat is applied by a resistive method to the tuning section of the laser

Distributed bragg reflector laser
Distributed Bragg Reflector Laser

  • First proposed tunable DBR laser was in 1977 for only the active section and the reflector

  • Consist of three integrated sections

    • The active section has a matching bandgap for the desired emission frequency which provides the optical gain

    • The reflector has a higher bandgap, such that the material is transparent for laser light

    • The phase section can be adjusted electronically through current injection. Using this a cavity mode can be tuned to the Bragg frequency


External cavity tunable laser
External Cavity Tunable Laser

  • Consist of a laser chip and external reflector

  • By using a grating as the external reflector, turning of the grating will lead to a tuning of the lasers wavelength

  • Intel is one company that is working on external cavity tunable lasers


Vertical cavity surface emitting lasers vcsel
Vertical Cavity Surface Emitting Lasers (VCSEL)

  • VCSEL first proposed in 1977 and demonstrated in 1979

  • In 1988 first continuous wave laser using GaAs material was demonstrated in 1988

  • In 1999 production and extension of applications for VCSEL technology


Vertical cavity surface emitting laser
Vertical Cavity Surface Emitting laser

  • Wavelength division multiplexing

  • Device fabrication

    • molecular beam epitaxy

  • Materials – GaAs has a natural wavelength emission of 873 nm, while InP emits a wavelength of 918nm.

Vertical cavity surface emitting laser1
Vertical Cavity Surface Emitting laser

  • Key Advantages

    • low cost

    • no noise

    • no frequency interruptions

    • less power consumption

    • higher performance of transceivers for metro

      area networks

    • high modulation bandwidth

  • Beam Characteristics – The emitted laser can be controlled by selecting the number and thickness of mirror layers

Tunable vertical cavity surface emitting lasers
Tunable Vertical Cavity Surface Emitting Lasers

  • Tuning mechanisms

    • Temperature: Increasing or decreasing the temperature of the material changes the wavelength transmission of the laser

    • Current: Multiple current injections are used in the device to change the wavelengths of the laser

    • Mechanical: most recent technique, uses micro-electro mechanical systems to adjust the wavelengths of the laser

  • Drawbacks

Tunable vcsel s cantilevers
Tunable VCSEL’s Cantilevers

  • How the cantilever works

  • Wavelength range is between 1530nm and 1610nm

  • The coupling efficiency of over 90%

Chang-Hasnain 2001

Tunable vcsel s half symmetric type
Tunable VCSEL’s Half Symmetric Type

Chang-Hasnain 2000

Tunable vcsel s membrane type
Tunable VCSEL’s Membrane Type

Chang-Hasnian 2001

Future applications
Future Applications

  • Optical Cross Connects (OXCs)

    • used to switch wavelengths in Metro area networks, it regulates traffic throughout the network.

  • Computer Optics

    • Computer links, optical interconnects

  • Optical Sensing

    • Optical fiber sensing, Bar code readers, Encoders

  • Displays

    • Array light sources, Multi-beam search lights

Economical impact
Economical Impact

  • Current Market Trends

    • Today as opto electronics become more commercial, this market generate about $ 15 billion a year

  • Future Market Projection

    • the world market for tunable lasers by 2007 should be about $ 2.4 billion a year


  • [1] Karim, A., Abraham, P., Lofgreen, D., Chiu, J., Bowers, Piprek, “Wafer Bonded 1.55μm Vertical Cavity Laser Arrays for wavelength Division Multiplexing”, IEEE Journal Electronics, Vol. 7, No. 2, Mar/Apr 2001, pp. 178-183

  • [2] Shinagawa, Tatsuyuki, Iwai, Norihrio, Yokouchi, Noriyuki, “Vertical Cavity Surface Emitting Semiconductor Laser Device”, United States Patent Application, Mar 2003, pp.1-11

  • [3] Chung-Hasnain, Connie, J., “Tunable VCSEL”, IEEE Journal on Selected Topics in Quantum Electronics, Vol. 6, No. 6, Dec 2000, pp. 979-985

  • [4] Derbyshire, Katherine, “Prospects Bright for Optoelectronics”, Semiconductor magazine, Vol. 3, No.3, Mar 2002, pp 1-5

  • [5] Chang-Hasnain, Connie, J., “Tunable VCSELs: enabling wavelength-on-demand in metro networks”, Compound Semiconductor, June 2001, pp. 1-3Selected Topics in Quantum

  • [6] WDM Technologies: Active Optical Components, Achyut Dutta, Niloy Dutta, Masahiko Fujiwara, Academic Press, pp. 116-150, pp. 167-205,2002