Figure-8 laser

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Fiber laser with figure-8 ring resonator. In: pumping. Out: emitting light. 1: active fiber. 2: polarizer. 3: optical insulator. 4 WDM splitter. 50:50 splitter 50/50.

A figure-8 laser is a fiber laser with a figure-8-shaped ring resonator. It is used for making pico- and femtosecond soliton pulses. The typical spectrum of such a laser consists of a wide central peak and a few narrow lateral peaks that are placed symmetrically around it. The amplitudes of the narrow peaks are the same as or less than that of the central peak.[1]

Both loops of the resonator work as Sagnac loops. The active medium of the laser is optical fiber with its core doped with rare-earth ions. It is placed asymmetrically with respect to the resonator loops to make a nonlinear difference in phase between opposite waves, ensuring mode locking.[2] In 1992 a figure-8 laser was built with a smaller loop length of 1.6 m and a larger loop length of 60.8 m for generation of 315 fs pulses with repetition rate 125 MHz.[3]

See also[edit]


  1. ^ Fermann et al. 2002, pp. 102—103.
  2. ^ Agrawal 2008, pp. 181—182.
  3. ^ Agrawal 2008, p. 215.


  • Agrawal G. P. (2008). Applications of nonlinear fiber optics. Optics and Photonis Series. 10 (2nd ed.). Academic Press. p. 508. ISBN 978-0-12-374302-2. 
  • M. E. Fermann; A. Galvanauskas; G. Sucha, eds. (2002). Ultrafast Lasers: Technology and Applications. CRC Press. p. 800. ISBN 978-0-8247-4349-9. 

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