1. High power fibered optical components for gravitational waves detector Matthieu Gosselin, PhD Student at EGO ELiTES : 3 rd general meeting February 10 th, 2015 University of Tokyo GraWIToN GW Initial Training Network 1

2. Summary GraWIToN project – PhD overview Electro-Optic Modulator and Faraday Isolator review – Improvements Thesis development GraWIToN GW Initial Training Network 2

3. Summary GraWIToN project – PhD overview Electro-Optic Modulator and Faraday Isolator review – Improvements Thesis development GraWIToN GW Initial Training Network 3

4. GraWIToN GW Initial Training Network 13 PhD students in different fields :  High power optical components  Materials (Silicon Carbide, Adhesive- Free Bond...)  Computer simulations  Data Analysis 4

5. Details on my Phd position GraWIToN GW Initial Training Network Input optics components for the upgrade of the 2 nd and 3 rd generations of gravitational waves detector  1 st year : fibered Electro-Optic Modulator for ≤10W  2 nd year : fibered Electro-Optic Modulator for ≥ 100W  3 rd year : fibered Faraday isolator for ≥ 100W To help me to face those high power issues :  Experience of the EGO optics group in HP free space components  Handling of HP fibered components at LZH (3 months)  Use of silicon carbide as high power beam dump at Boostec (1 month) November 2014 – November 2017 5

6. Summary GraWIToN project – PhD overview Electro-Optic Modulator and Faraday Isolator review – Improvements Thesis development GraWIToN GW Initial Training Network 6

7. EOM and FI uses Use of the properties of electro/magneto optics crystals Sidebands generation Error signal to be minimized GraWIToN GW Initial Training Network To modulate the phase and generate side bands used to lock cavities (Pound Drever Hall technique) EOM FI To have different polarization between input and reflected beam to avoid damages into the laser Polarizer Faraday rotator Input beam Rejected output beam 7 "Faraday-effect". Licensed under CC BY-SA 3.0 via Wikimedia Commons

8. Injection into vacuum GraWIToN GW Initial Training Network Critical part  Free space propagation : noise  Already been improved by covering the beam path (purple lines)  Should be even better with a fiber 2 nd generation design 8

9. Injection into vacuum with a fiber GraWIToN GW Initial Training Network Fibered EOM  Injection into a HP fiber  All transmission are then fibered 9 Fibered FI and Power Control

10. Existing EOMs GraWIToN GW Initial Training Network  High Power or fully fibered  Many others criteria : number of modulations, modulation depth, noises…  Modulation can be done before amplification Power CW>200W~150W~5W Transmission>95%>98%~70% PropagationFree space Fully fibered AdVirgo 10

11. Existing FIs GraWIToN GW Initial Training Network  Market not adapted to our very specific needs but fully fibered propagation is possible  Better properties reachable if less integrated Power CW>200W~30W> 50W Isolation>30dB~25 dB~21dB Transmission>95%~75%~95% PropagationFree space Fully fibered  Huge differences between the one that has been designed for GW detector and  such good specs are hard to reach, almost a prototype… developed for GW detector on the market developed for medium power, compact but specs… AdVirgo 11

12. Summary GraWIToN project – PhD overview Electro-Optic Modulator and Faraday Isolator review – Improvements Thesis development GraWIToN GW Initial Training Network 12

13. Expected specifications GraWIToN GW Initial Training Network FI : Input power : 200W Transmission : >95% (Depolarisation, Verdet constant, absorption, reflections) Isolation : >30db EOM : Input power : 200W Transmission : >95% Number of frequencies : 4 (5?) Noises : depend on the frequency 13  See Advanced Virgo and Einstein Telescope Technical Design Reports

14. Details of the components GraWIToN GW Initial Training Network Collimators - Focusable - High Power - Beam output diameter up to 2.5mm - Tilt adjustment Crystal fiber - High Power - Core diameter 15 μm - Single mode - Large Mode-Area - Polarization Maintaining Connectors - SMA-905 - Power > 100W - Cladding Mode Stripper Alignment Stage - 5 axis - translation ~1μm - angle ~5Arcsec 14

15. Fibered EOM proceedings GraWIToN GW Initial Training Network >95% Coupling on a low power bench (<500mW)  Use of the same collimator symmetrically positioned  Settings easier without tilt  Moves eased by the breadboard Beam shifted but not tilted Top view of the crystals 1) Without crystals 2) With crystals Breadboard Rotation stage 15

16. Fibered EOM proceedings GraWIToN GW Initial Training Network Coupling on a high power bench (from 500mW to 200W) 1) Coupling of the fiber laser into the high power fiber High power Laser 2) Switch the breadboard from LP bench to HP bench 3) Increase the power step by step to observe the side effects 4) Solve the side effects to be able to reach our specifications 16

17. Difficulties expected GraWIToN GW Initial Training Network Beam diameter 1-2mm to avoid heating in the crystals Core of the fiber diameter 15 μm to have a good beam quality  Power density ~10 6 W/mm2 Coupling difficulties : VS Collimators or connectors heating :  Cooling  Fiber with a larger core (LMA-PM-25) Lower beam quality but lower power density  Shutter reacting to a rise of the scattered light and/or the temperature Worst with FI since the absorption is 50 times greater 17

18. Summary Avoid noises due to free space propagation  Fibered as much as possible  Confined as much as possible Main issues  Keep a good coupling efficiency  Avoid damages due to the high power density GraWIToN GW Initial Training Network 18

19. Back up slides GraWIToN GW Initial Training Network 19

20. Components GraWIToN GW Initial Training Network 20

21. EOM GraWIToN GW Initial Training Network Une seule slide plus rapide pour EOM et FI et details en back up ? Ou tout en back up? 21

22. PDH technique "PDHBasicLayout" by Andrew Wade - Andrew Wade.Wikimedia Commons Error signal Sidebands generation GraWIToN GW Initial Training Network 22

23. Faraday Isolator Avoid the power to come back into the laser  Avoid uncertainties  Avoid damages laser "Faraday-effect". Licensed under CC BY-SA 3.0 via Wikimedia Commons Polarizer 1 Polarizer 2 Faraday rotator Input beam Rejected output beam ? ? GraWIToN GW Initial Training Network Back up ? 23

24. Faraday Isolator GraWIToN GW Initial Training Network 24

25. AdV Phase noises GraWIToN GW Initial Training Network 25

26. GraWIToN GW Initial Training Network 26

27. GraWIToN GW Initial Training Network 27 EIB SIB1 SIB2

28. Crystal GraWIToN GW Initial Training Network 28