1. 1 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

2. 2Outline Introduction Introduction Tuning Mechanisms Tuning Mechanisms Distributed Bragg Reflector Lasers Distributed Bragg Reflector Lasers External Cavity Tunable Lasers External Cavity Tunable Lasers Vertical Cavity Surface Emitting Lasers Vertical Cavity Surface Emitting Lasers Types of Vertical Cavity Surface Emitting Lasers Types of Vertical Cavity Surface Emitting Lasers Future Applications Future Applications Economical Impact Economical Impact

3. 3 Introduction Most tunable lasers consist of a longitudinal integration of sections 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 The problem of Metro Area Networks

4. 4 Tuning Mechanisms Electric field-induce index change Electric field-induce index change –An electrical field is applied that changes the refractive index of the waveguide Thermally-induced index change Thermally-induced index change –Heat is applied by a resistive method to the tuning section of the laser

5. 5 Distributed Bragg Reflector Laser First proposed tunable DBR laser was in 1977 for only the active section and the reflector First proposed tunable DBR laser was in 1977 for only the active section and the reflector Consist of three integrated sections 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]

6. 6 External Cavity Tunable Laser Consist of a laser chip and external reflector 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 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 is one company that is working on external cavity tunable lasers Intel

7. 7 Vertical Cavity Surface Emitting Lasers (VCSEL) VCSEL first proposed in 1977 and demonstrated in 1979 VCSEL first proposed in 1977 and demonstrated in 1979 In 1988 first continuous wave laser using GaAs material was demonstrated in 1988 In 1988 first continuous wave laser using GaAs material was demonstrated in 1988 In 1999 production and extension of applications for VCSEL technology In 1999 production and extension of applications for VCSEL technology Honeywell

8. 8 Vertical Cavity Surface Emitting laser Wavelength division multiplexing Wavelength division multiplexing Device fabrication Device fabrication –molecular beam epitaxy Materials – GaAs has a natural wavelength emission of 873 nm, while InP emits a wavelength of 918nm. Materials – GaAs has a natural wavelength emission of 873 nm, while InP emits a wavelength of 918nm.

9. 9 Vertical Cavity Surface Emitting laser Key Advantages Key Advantages – low cost – no noise – no frequency interruptions – less power consumption – higher performance of transceivers for metro area networks area networks – high modulation bandwidth Beam Characteristics – The emitted laser can be controlled by selecting the number and thickness of mirror layers Beam Characteristics – The emitted laser can be controlled by selecting the number and thickness of mirror layers

10. 10 Vertical Cavity Surface Emitting Lasers Vertical Cavity Surface Emitting Lasers Linnik 2002

11. 11 Tunable Vertical Cavity Surface Emitting Lasers Tuning mechanisms 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 Drawbacks

12. 12 Tunable VCSELs Cantilevers How the cantilever works How the cantilever works Wavelength range is between 1530nm and 1610nm Wavelength range is between 1530nm and 1610nm The coupling efficiency of over 90% The coupling efficiency of over 90% Chang-Hasnain 2001

13. 13 Tunable VCSELs Half Symmetric Type Chang-Hasnain 2000

14. 14 Tunable VCSELs Membrane Type Tunable VCSELs Membrane Type Chang-Hasnian 2001

15. 15 Future Applications Optical Cross Connects (OXCs) Optical Cross Connects (OXCs) – used to switch wavelengths in Metro area networks, it regulates traffic throughout the network. Computer Optics Computer Optics – Computer links, optical interconnects Optical Sensing Optical Sensing –Optical fiber sensing, Bar code readers, Encoders Displays Displays –Array light sources, Multi-beam search lights

16. 16 Economical Impact Current Market Trends Current Market Trends –Today as opto electronics become more commercial, this market generate about $ 15 billion a year Future Market Projection Future Market Projection – the world market for tunable lasers by 2007 should be about $ 2.4 billion a year

17. 17 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 [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 [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 [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 [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 [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 [6]WDM Technologies: Active Optical Components, Achyut Dutta, Niloy Dutta, Masahiko Fujiwara, Academic Press, pp. 116-150, pp. 167-205,2002

18. 18 Back Tunable VCSEL Cantilever