1. High Power Cladding-pumped Fiber Laser Speaker: Shiuan-Li Lin Advisor : Sheng-Lung Huang Solid-State Laser Crystal and Device Laboratory

2. Page 2 Outline  Compare fiber lasers with bulk glass lasers  High power fiber laser:difficulities  Cladding fiber structure : Basic, Cladding shape & Resonators  Core doping elements ( Yb/Er co-doped fiber)  Conclusion & Discussion Solid-State Laser Crystal and Device Laboratory

3. Page 3 Compare fiber lasers with bulk glass lasers  More compact, lighter and more efficient  Better beam quality (mode control)  Increase the surface-to-volume ratio (thermal managements)  Operate over a long time span with high reliability, alignment free Solid-State Laser Crystal and Device Laboratory

4. Page 4 High power fiber laser:difficulities How to get enough pump power  High coupling efficiency & NA  Using high power laser diode arrays Optical damages of fibers  Induced by the large amount of power density into fiber core  Brillouin backscattering & Raman scattering Solid-State Laser Crystal and Device Laboratory Nonlinear effects  Silica damage threshold : 10 W/ (CW)  Thermal effects

5. Page 5 Cladding fiber structure : Basic Solid-State Laser Crystal and Device Laboratory  small single-mode core hard to obtain high power output  Cladding-pumped: single-mode output signals with multimode pump lasers  The doped core gradually absorbs the cladding light as it propagates, driving the amplification process © Wikipedia

6. Page 6 Cladding fiber structure : Cladding shape Solid-State Laser Crystal and Device Laboratory  non-circular : more pump power to enter fiber core  Increase pump modes, ex: 28% improved with offset shape © Optics Communications 132 (1996) 511-518 Spiral shape

7. Page 7 Cladding fiber structure : Resonators Solid-State Laser Crystal and Device Laboratory  Single-end co-propagating pump  Single-end counter-propagating pump  Dual end pumps Electronics Letters, Vol. 35, No. 14, 8th, July 1999.

8. Page 8 Core doping elements Solid-State Laser Crystal and Device Laboratory © Y.W. Lee Why using Erbium? 1. emitting at eye-safe wavelengths 2. 1.5μm radiation for optical communications (EDFA)

9. Page 9 Er/Yb co-doped fiber Solid-State Laser Crystal and Device Laboratory  Erbium usually co-doped with Ytterbium : 1.Erbium is not particularly soluble in the silica core 2.Erbium doped fiber’s pump absorption is only several tens of dB/m 3.Co-doped : dramatic increase in pump absorption enables typical amplifier gain lengths of 10 meters or more Fibercore

10. Page 10 Er/Yb co-doped fiber Solid-State Laser Crystal and Device Laboratory  Er-doped silica fibers: in the 1.5–1.6 μm wavelength region corresponding the transition  Pump light is absorbed by Yb3+, and the Er3+ ions are excited indirectly by energy transfer from the Yb3+ ions Er,Yb co-doped energy level diagram The power spectrum of the Yb : Er codoped fiber © IEEE PHOTONICS, VOL. 13, NO. 3, 2001

11. Page 11 Conclusion & Discussion Solid-State Laser Crystal and Device Laboratory  Applications of Cladding-pumped fiber technology are widely varied (medical surgery, high power laser, WDM system…..etc)  In our system: 1.Benefits & Advantages in crystal fiber 2.How to increase fiber length (gain medium) 3.Slightly mutlimode mode to single mode

12. Page 12 Solid-State Laser Crystal and Device Laboratory bee6565 Thanks for your listening!