1. CNMFrascati 12/01/061 High Power Laser System for Advanced Virgo C.N.Man Design goals Present technology Other activities in the world Virgo+ and Laser System - possible planning Advanced Virgo HP laser HP related photonics (fibers as MC, modulators,…) All-fibered laser system Conclusion

2. CNMFrascati 12/01/062 Laser power: 200W Wavelength : 1  m to 1.6  m, linked to SiO 2 or Si, laser material, optical technology,… Input Beam propagation: free space, fibre ? Beam cleaning: resonant MC or fibre MC? Modulation: –Bulk, or fibre components ? Which frequency(ies) ? Design goals

3. CNMFrascati 12/01/063 Present technology : laser designs High power  cooling problem (birefringence induced by thermal loading, …)  large surface/volume ratio and material conductivity  high efficiency Solutions : new crystals, or ceramics disk amplifiers or fibres Today, kW single mode lasers are available with both disks and fibre amplifiers

4. CNMFrascati 12/01/064 Other activites in the world -Laser systems (< kW) -GW groups activities: mainly Germany and Australia -Scientific and telecom lasers (> 100 W) -Disks and fibre lasers, many European small companies Yb and Er doped Fiber lasers: 1,06 and 1,3  m -Nb: telecom lasers  MTBF > 100 000 h  Fibre integrated isolators, modulators, etc  1.3- 1.5  m wavelength -Very high power lasers ( up to MW CW) -Disk lasers for military and industry : Boeing, … -Fibre lasers for welding, cutting (kW`s)

5. CNMFrascati 12/01/065 Virgo + : First Step in the Studies Virgo+: as master laser, Fiber laser or SSL HP Solid State laser/amplifier (LZH) To start : 1 - investigations on the FL as a potential new Master laser 2 - development of a 50 W laser/amplifier in SS technology Deliverables in 07-08: A Single-Frequency Fiber laser of 2W A laser amplifier to scale up the 20W to 50W

6. CNMFrascati 12/01/066 Laser System for Virgo + injection locking 20W laser Master Laser 50W Amplifier PMC Fiber laser

7. CNMFrascati 12/01/067 Fiber Master Laser for Virgo + 100 mW Oscillator amplified to 2 W at 1.06  m

8. CNMFrascati 12/01/068 Virgo + : Nd:YVO4 50WAmplifier (LZH) Four-stage end-pumped Nd:YVO4 Each stage pumped by 45 W laser diode Each diode indiv temp controlled Each 2diodes connected in series to 1 current driver Diodes current controlled

9. CNMFrascati 12/01/069 Possible Planning for Virgo + Laser System

10. CNMFrascati 12/01/0610 Adv. Virgo: HP single-mode fiber lasers

11. CNMFrascati 12/01/0611 HP related photonics Modulation: Bulk, or fibre modulators ? (Which frequency(ies) ?) Beam propagation: free space or through fibre ? Fiber laser : no MC needed SSL: resonant cavity MC or fibre MC?

12. CNMFrascati 12/01/0612 Requirements for mode cleaning Spatial filtering of modes Resonant mode close to a gaussian beam Output beam independent of input beam or ouput phase noise independent of input beam jitter No addition of any extra noise Power standing required Why using a fiber: simplicity of the system, its control and its maintenance

13. CNMFrascati 12/01/0613 PCF as Input Mode Cleaner Photonic Crystal Fiber offers this possibility of power handling Use of monomode fibers not realistic up to now, due to power handling capabilities What is a PCF ?

14. CNMFrascati 12/01/0614 High Index Guiding Fiber Light is guided in the core by total internal reflection: the airholes in the cladding make its effective index lower than that of the core NA = 0.8

15. CNMFrascati 12/01/0615 Low Index Guiding Fiber: Photonic bandgap fiber Light is guided in the core by Bragg reflection caused by the spatial periodicity of the holes in the cladding B

16. CNMFrascati 12/01/0616 Fabrication of PCF

17. CNMFrascati 12/01/0617 PCF R&D financed by EGO Started in 11/04 - Goals: test of a commercial PCF hollow-core fiber in terms of : ** Handling, Coupling efficiency, loss measurements * Output Beam analysis, comparison with numerical modeling (coll with IRCOM-Limoges, Blaze Photonics) ** Measurement of phase noise introduced by the fiber in a normal environment *** Power standing of 20W, Induced amplitude noise, Polarisation noise (this fiber is not polar.maintaining fiber now), dependency of input/output noise

18. CNMFrascati 12/01/0618 Results on hollow-core HC-1060-02 HC-1060-02 Blaze Photonics Core 10  m, pitch 2.75  m, holey region diam 50  m Attenuation < 0.1 dB/m Mode field diameter 6.5  m Fresnel reflection at end faces <10 -4 No bend loss at 3 mm radius Quasi-gaussian monomode >90%

19. CNMFrascati 12/01/0619 Experimental results (2005) Coupling and handling like standard fibers; Attenuation loss measured 0.05 dB/m coupling of 90% obtained: further improvements with a phase plate or an adaptive mirror Transmission : output/input of 45% loss of 4.5% with a bending of 0.8 cm Residual coupling between core and cladding modes due to imperfections Measured near-field intensity Input face of the PCF

20. CNMFrascati 12/01/0620 Extra Noise measurement The ouput of the PCF is sent into a high finesse Fabry-Perot as discriminant => no evidence of extra frequency noise No fast polarization & amplitude noises Power handling of 20W To be done: Choice between hollow core PCF and large silica core PCF (30 µm)

21. CNMFrascati 12/01/0621 Available fiber components (for power <1W) Faraday isolators (> 55 dB isolation) Polarization controllers (20 kHz bandwidth) Phase and amplitude modulators (GHz bandwidth, low voltage drive) 55 mm 35 mm

22. CNMFrascati 12/01/0622 All-fibered Laser System Amplifier Beam monitoring Oscillator (Nd-YAG or fibre Frequency control Amplitude control Polarization control Vacuum Vacuum (optional) Faraday isolator 100W to interferometer 100 mW Monomode fibre (PM?)

23. CNMFrascati 12/01/0623 Conclusion: Proposed main steps -2006 Acquisition and test 1-2 W fibre laser (Yb @ 1064 nm) -Evaluation and control in Nice -2007 Test as a master laser in Cascina Acquisition of a high power Yb-doped fiber amplifier -2009 ? Test of a HP Yb-doped fiber amplifier -2006-2008 Development and tests of a fibre mode-cleaner -After the choice of advanced mirrors material: -Definition and acquisition of the advanced laser system prototype ( 3 years ahead of installation)