Rare-Earth-Doped Fiber Lasers www.rp-photonics.com Anneke Batenburg 0123137

Introduction Fiber Lasers : lasers having a doped fiber as gain medium or (sometimes) just lasers where most of the laser cavity consists of fibers. Dopants usually are rare-earth ions, like erbium, neodymium, ytterbium... Hier kan ook het plaatje uit het boek komen.

Erbium Energy Levels Transition between 4f-levels: actually forbidden (parity), but can occur through interaction with lattice electrons. 4f electrons are very well shielded from crystal: little collisional decay and long u. Transition at 1.53 μm: very useful for telecom Inhomogeneous broadening in glass. De I-I overgang is eigenlijk verboden, omdat er geen verandering in pariteit optreedt, maar ..... bestuderen

Pumping Scheme Possible pumping wavelengths: 0.98 and 1.48 μm. Usually pumped with laser diodes.

Parameters...

Advantages of Fibers Large surface-to active-volume ratio → good heat dissipation, less thermal effects Low losses in the fiber, permits construction of very long lasers and amplifiers, leading to very high single-pass gain and low pump treshold values Broad gain bandwidth (glass) Easily integrable in communication systems, compactness, stability

Output Fluctuations Spiking is common in three-level solid-state laser systems, and also in erbium-doped fiber lasers. Spiking can be suppressed by choosing suitable pumping wavelength (Loh et al) 980 nm 1510 nm

Double-Clad Fibers Ordinary single-mode fibers have to be pumped by single-mode diode lasers, typically limited in power (~W). Solution: double-clad fibers. Laser light propagates in core, pump light in highly multimode inner cladding. Allows for higher power laser diode pumping (and higher gain)

Photonic Crystal Fibers Nonlinear effects restrict ultimate power of fiber lasers. Desired: single mode fibers with large mode area (low power density) The renaissance and bright future of fibre lasers, Tünnermann et al.

Photonic Crystal Fibers 2 More missing air holes lead to larger mode-areas (but take care of bending losses).

Double-Clad PCF (Makes in-coupling of pump light easier by larger numerical apertures) 80 W output power, could be scaled up to 260 W, authors expect 4 kW in the future

Questions? www.erbium.nl/nanophotonics www.rp-photonics.com Laser Funadementals Optical Fiber Sensors: Principles and Components, edited by John Dakin and Brian Culshaw,Artech House The renaissance and bright future of fibre lasers, A Tünnermann, T.Schreiber, F. Röser, A. Liem, S. Höfer, H. Zellmer, S. Nolte and J. Limpert, Journal of Physics B Suppression of self-pulsing behaviour in erbium-doped fiber lasers with resonant pumping: experimental results, W.H. Loh and J.P. de Sandro, Optics Letters 1996