High power VBG Yb-fiber laser

1. High power VBG Yb-fiber laser Slope eff. ~75 % Δλ = 0.4 nm M2~5.5 • Yb-fiber Core: 30 m, NA 0.056 • D-shaped cladding :  400 m, NA 0.49 • Fiber length : ~8 m (abs. ~2 dB/m at 975 nm) • Launch efficiency : ~90 % VBG 1.5mm 3mm 5mm Δλ = 0.22 nm, λcentre = 1066.0 nm, R= 99 % AR coated surface normal polished ~2o to the grating vector P. Jelger, P. Wang, J. K. Sahu, F. Laurell, and W. A. Clarkson, Opt. Expr. 16, 9507 (2008)

2. Transversally chirped VBG Yb laser • > 100 W output • > 78 % slope efficiency • Tunable from 1064-1073 nm • <0.5 % power fluctuation over tuning range • Narrowband signal < 50 pm • Temporal stability <0.2 % rms • M2 = 1.2 • Single-polarization >18 dB PER SBS threshold approx. 5 kW

3. Tunable, high-power, 2 wavelength Yb laser Dual-line lasing 78 W wavelength separation 0.03 - 2 THz, Power fluctuation<1 %.

4. Ultra-fast lasers Kerr-Lens ML Ti:sapphire laser D.E. Spence, P.K. Kean, and W. Sibbet Opt. Lett. 16, 42 (1991) M. Piché, Opt. Commun. 86, 156 (1991) Patent for the Aperture (Coherent)

5. The Frequency Comb T  = phase offset between carrier wave and wave envelope fm = mfrep + foffset frep= 1/T foffset = ( /2) frep Therefore if  = 0  foffset= 0  fm = mfrep The idea has revolutionized the art of frequency measurements Theodor W. Hänsch e John L. Hall, Nobel Prize for Physics (2005)

6.  10-3 – 10-5 up to 105 amplifier compressor  103 - 105 oscillator stretcher High Peak Intensities Lasers Chirped Pulse Amplification (CPA) D. Strickland and G. Mourou (1985) Ti:Al2O3 : 1-10 mJ; f = 1-10 kHz TTT [Terawatt Table Top] Lasers : 100 TW (5 J, 50 fs) Petawatt-class Lasers (1,5 PW, i.e. 580 J and 460 fs)

7. Historical Evolution of Pulse Duration From Femtoseconds to Attoseconds 4 fs 80 as: E. Goulielmakis et. al., Science 320, 1614 (2008)

9. Everything...

10. In Science Laser cooling Na-atom molasses 6 laser beams with frequency slightly shorter than the transition frequency. Reduced the energy of a cloud of atoms to form an optical molasses. Temperatures down to micro-Kelvin. Nobel prize in 1997 for Chu, Cohen-Tannoudji and Phillips

11. The world's largest and highest-energy laser the National Ignition Facility at Lawrence Livermore In the NIF experiments 192 giant laser beams are focused on a cm-sized target filled with hydrogen fuel. NIF's goal is to fuse the hydrogen atoms' nuclei and produce net energy gain (Eout = 100 Ein) The beams compress the target to 100 billion times the atmosphere to a temperature of 100 million °C

12. Imaging and displays – large, small or 3D

14. Conclusions Acknowledgments Friends and laser family References can be found on www.laserphysics.kth.se Solid-state lasers • efficient • Reliable • tailored fun And….

15. That´s all folks!

16. Hollow fiber dye and Q-dots sources Scematic layout Photograph of Rodamine 6G filled fiber Green pumped hollow fibre in wich dye is pumped

17. Functional optical materials and structures • Chemically and photostructured glasses • Domain engineered ferroelectrics • Quantum dots • Silicone elastomers • Microstructured silicon

18. Acknowledgments Laser physics group National and international colleagues www.laserfest.org

19. Limitations related to thermal loading 2 mm FEM simulation 1 kW 3 mm 5 mm Absorption 0.2%/cm Δ λ ~ 0.5 nm Significant problem for lowgain lasers and high circulatingpowers Temperature distribution Width of VBG [mm] • Chirp reduces reflectivity! • VBG would transmit more power! Distance into VBG [mm]

20. > 30 W Single Frequency CW VBG OPO P. Zeil, et al. Optics Express, 22, 29907-29913 (2014).