1. Development of high-power and stable laser for gravitational wave detection Mio Laboratory Kohei Takeno

2. 2003-Feb-07The 3rd TAMA symposium2 Nd:YAG 30W TEM 00 Injection lock ？ × Aims of My Work Nd:YAG （ 1.064  m ） Output Power ＞ 100W Single Transverse Mode Single Longitudinal Mode Low Intensity Noise Low Frequency Noise Linearly Polarized Final Goal Current Status

3. 2003-Feb-07The 3rd TAMA symposium3 Mode / Thermal Effects Rd Laser Cavity Laser Medium OC HR Output Optimum Coupling Pump

4. 2003-Feb-07The 3rd TAMA symposium4 Mode Transverse Mode : Spatial Distribution Multi-mode oscillation depends on the mode of the laser cavity Longitudinal Mode : Frequency Difference The spatial hole burning causes multi-mode oscillation In progress now Succeeded in controlling!

5. 2003-Feb-07The 3rd TAMA symposium5 Transverse Mode Lowest Order TEM 00 Higher Order TEM 10 Higher order modes spread compared to the lowest

6. 2003-Feb-07The 3rd TAMA symposium6 Beam Quality ： M 2 M 2 =1 : Diffraction-Limited (TEM 00 ) M 2 = D 0  / d 0 

7. 2003-Feb-07The 3rd TAMA symposium7 Thermal Effects Energy which is stored in the laser medium causes … Thermal Lens Thermal Birefringence Thermal lens affects stability of the laser cavity

8. 2003-Feb-07The 3rd TAMA symposium8 Strategy for High Power Laser Two points: Give gain to the lowest-order mode Give loss to higher-order modes How to design the laser cavity? Clip higher-order modes with rod hard aperture → Long cavity Stable cavity by use of thermal lens → Flat mirrors

9. 2003-Feb-07The 3rd TAMA symposium9 Strong thermal lens/Too long cavity Long cavity Rd Flat mirrors + Thermal lens Cavity Modes Laser Medium OC HR unstable Rd Laser Medium OC HR

10. 2003-Feb-07The 3rd TAMA symposium10 My Experiment Design of Optimum Laser Cavity Transverse mode control Make use of thermal lens Laser module Specification ： 35W Output @ 25A LD Current （ Short cavity / Multi transverse mode oscillation ）

11. 2003-Feb-07The 3rd TAMA symposium11 Laser Module Cutting Edge Optronics Nd:YAG Rod (2mm diameter, 63mm length) 0.6% Nd 3+ doped LD pumped Water-cooled

12. 2003-Feb-07The 3rd TAMA symposium12 Thermal Lens Measurement of the Focal Length

13. 2003-Feb-07The 3rd TAMA symposium13 Linear Cavity (L １, L ２ ) Cavity and Mode Simulation

14. 2003-Feb-07The 3rd TAMA symposium14 Power vs OC Transmittance Laser Output→“Loss” of the cavity Optimum coupling

15. 2003-Feb-07The 3rd TAMA symposium15 Power vs OC Transmittance

16. 2003-Feb-07The 3rd TAMA symposium16 Power vs Cavity Length Short cavity→Multi transverse mode Long cavity→Causes loss for TEM 00

17. 2003-Feb-07The 3rd TAMA symposium17 Power vs Cavity Length

18. 2003-Feb-07The 3rd TAMA symposium18 M 2 ＝ 1.1 (Horizontal) M 2 ＝ 1.2 (Vertical) Flat mirrors Long cavity （ 71cm ） Output Power 30W Optimum Laser Cavity TEM 00

19. 2003-Feb-07The 3rd TAMA symposium19 TEM 00 ・ 30W Laser

20. 2003-Feb-07The 3rd TAMA symposium20 Ring Cavity Traveling-wave cavity Bi-directional output （３ W / path ）

21. 2003-Feb-07The 3rd TAMA symposium21 Summary Measure the thermal effects Succeeded in controlling transverse modes TEM 00 30W laser output with linear cavity Bi-directional lasing with ring cavity

22. 2003-Feb-07The 3rd TAMA symposium22 Further Work Thermal birefringence compensation Insert a QWP in the laser cavity Injection locking Control the laser cavity Measure the noise characteristics New laser head has arrived!!

23. 2003-Feb-07The 3rd TAMA symposium23 CIDER Close-coupled Internal Diffusive Exciting Reflector 60W ・ TEM 00 (M 2 = 1.07)

24. 2003-Feb-07The 3rd TAMA symposium24 Thermal Birefringence Image of the thermal birefringence 20.3A25.4A Pumping Power Image

25. 2003-Feb-07The 3rd TAMA symposium25 Further Work II Cascade Laser Cavity MOPA Coherent Addition Injection-locking Chain

26. 2003-Feb-07The 3rd TAMA symposium26 Laser Development My Work + Stable, High Quality M 2 <1.1 100W