1. GW related research activities in Hannover UNI/AEI
High power Laser development/ Laser stabilization
Diffractive optics
Alternative IFO layouts (multiple mirror cavities in the IFO arms)
Thermal noise experiments
LISA

2. Nd:YVO4 - Virgo Laser (20W)
End Pumped Rods
Nd:YAG - GEO600 Laser (14W)
Nd:YVO4 - Virgo Laser (20W)
Laser Zentrum Hannover

3. Injection Locked Oscillators - Hannoverf 2f QR
YAG / Nd:YAG / YAG
3x 7x40x7 FI
EOM
NPRO
20 W Master BP
High Power Slave
modemaching
optics
YAG / Nd:YAG
3x2x6
output
key elements:
undoped bonded end-caps
birefringence compensation
pumplight homogenization

4. high power stage status Feb 2004
linear polarized with birefringence compensation
Not injection locked yet

5. Grating development Two different options:
Phase grating on substrate overcoated with a HR layer stack
> Low eff. gratings
Phase grating atop
of a HR layer stack
> Highly eff. gratings

10. Grating research summary
Low efficiency grating can substitute transparent BS
phase relations for gratings understood
Losses of 1st test grating < 400ppm
Will further investigate theoretically and experimentally new IFO topologies
Investigate influence of grating on test mass Q
produce gratings on silicon test masses and measure performance
increase size of gratings
Test low efficiency low angle coupler

11. Alternative IFO topologies
Photodetektor
Spiegel 11
Spiegel 21
Strahlteiler
Spiegel 12
Spiegel 22
Spiegel 13
Spiegel 23
Spiegel 24
Spiegel 14
EOM 2
EOM 1
EOM 3

12. Thermally adaptive optics
Correction of ROC of a GEO600 mirror
Investigations of compensation of thermal lensing in the BS at high light powers
Variation of the reflectivity of the signal recycling mirror
Status

13. Avoiding astigmatism with a segmented heater
2 heatin elements
for vertical ROC
2 heating elements
control horizontal ROC
Heater with separately controlled heating elements allows inhomogeneous bending of the mirror.

14. Controlling the SR bandwidth
Bandwidth  Finesse of the SR cavity  Reflektivity of MSR
Temp. controlled Signalrecycling-Etalon (r=150mm, d=75mm)
Reflektivity is controlled by temperature

15. Test set-up suspended SR-Etalon in Vacuum set-up
thermal environment identical to GEO600
Rediation shield:
Galvanized copper, 0.4 µm Gold

16. Adjustable SR-gain (Garching prototype)
Nach Re-Lock identische SR-Verstärkung

17. Squeezed Light
Table top experiment for squeezed light generation and GW frequencies
Applications for GW detectors
Application of Kerr media for GW detectors

18. LISA activities Laser frequency stabilization
Optical layout for LISA pathfinder mission