Tunable lasers in optical communications
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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

By

James Harper

Instructor: P. Lui

Department of Electrical Engineering

University at Buffalo State University of New York

Course Requirement for EE 566


Outline

Outline

  • 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


Introduction

Introduction

  • 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

[1]


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

Intel


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

Honeywell


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


Vertical cavity surface emitting lasers

Vertical Cavity Surface Emitting Lasers

Linnik 2002


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


References

REFERENCES

  • [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


Tunable vcsel cantilever

Tunable VCSEL Cantilever

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