High power fiber laser research, with Advanced Virgo and ET applications Ali Hreibi & Walid CHAIBI , ARTEMIS, Observatoire de la Côte d’Azur 18/04/2018 20/06/2018 1
Advanced Virgo Pre-Stabilized Laser 140 W 50 mW 100 W 190 W >190 W 100 W Wei et al. Optics Letters 41 , 5817 (2016) Advanced Virgo requirements : with parametric instabilities : < 50W - Input power : 125W - Gaussian mode content : >90% - RIN : Relative intensity noise - Phase noise added by the amplification process : 7 orders of magnitude with respect to NPRO (G. Santarelli LP2N) - Beam pointing noise : into intensity noise by the PMC 18/06/2018 2 - Long term operation : peak to peak fluctuations +/- 2% for months
100W single unit : All fibered design (ALS + Alphanov) NKT : DC-200/40-PZ-Yb Pump LD Active core Pump LD (4 x 60 W) Pump 40 µm core Air clad Nufern PM fiber : Mode Field PLMA-YDF-10/125-VIII adaptor Free space (MFA) NPRO isolator 4 W 110 W combiner Fibered combiner Fibered 25 mW isolator isolator 100 W 𝜇 𝜇 preamplifier HP amplifier 2 4 dichroic - Custom design MFA (Alphanov) - NKT High power polarizing fiber - Large mode area 760 µm² : Stimulated Brillouin Scattering (SBS) limits the power >300 W. 18/06/2018 3
All fibered design (ALS + Alphanov) Datas : pumps current, seeder power, Combiner T° MFA T° pre-amplifier power Combiner + MFA (27.5 °C) Pre-amplifier 30cm Chiller 2 HP fiber coiled signal 18°C : stabilizing the Pump LDs fiber T° + controlling the (2 independent combiner + MFA T° modules) 𝜇 /4 pumps 𝜇 /2 Slow (50%) and fast (few %) control of Chiller 1 the power Heat extraction isolator 18/06/2018 4
System characterization : RIN and Beam Pointing Noise 18/06/2018 5
System characterization : Beam quality and long term operation Coupling into a reference cavity. Beam shape, radius @ waist ~ 600 µm Finesse = 900 Overall functioning time > 2500 h, 3W peak to peak Zhao et al. , App.Phys. B 124 , 114 (2018) 18/06/2018 6
Coherent beam combination CBC Triangular cavity as a mode reference cavity on which the two beams are adapted 18/06/2018 7
Towards ET… Einstein Telescope high power ~ 1kW input, 3MW intracavity interferometer NKT : DC-200/40-PZ-Yb Pump LD Pump LD (4 x 60 W) Nufern PM fiber : Mode Field PLMA-YDF-10/125-VIII adaptor Free space (MFA) NPRO isolator 4 W 110 W combiner Fibered combiner Fibered 25 mW isolator isolator 100 W 𝜇 𝜇 preamplifier HP amplifier 2 4 dichroic Critical points : - Signal and pumps combination and coupling into the High power fiber - Photodarkening - Transverse mode instability (TMI) 18/06/2018 8
All fibered design (ALS + Alphanov) Photodarkening : generation of color centers - Highly non linear 6 to 7 Yb 3+ in - Depends on the pump & excited level signal spatial distribution Koponen et al. , Proc of SPIE 5990 , 599008 (2005) 19/06/2018 9
Transverse Mode Instability (TMI) Eidam et al. , OPTICS EXPRESS 19 , 13218 (2011) High power Temperature transverse gradient = Modification of Transverse mode index gradient mode the guiding instability structure Irreversible grating inscription @1.5 µm, less phtodarkening, but higher quantum defect… Jauregui et al., OPTICS EXPRESS 23, 20204(2015) 19/06/2018 10
200W amplifier based tapered fiber (Alphanov) Phospho-silicate, a Alumino-silicate better dilution of Yb : less photodarkening Free space counter- propagating pumping Pierre et al. , Proc of SPIE 10512 , 105122A-1 (2018) 18/06/2018 11
Conclusion 100 W fiber laser fulfills the Advanced Virgo specifications as a single unit for coherent summation. Fiber technology is evolving fast enough. CBC as a back up 18/06/2018 12
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