©LZH ZA GEO 600 Laser System as in the optics lab of Callinstraße 38 at LIGO-G D
©LZH ZA New Features of GEO 600 Slave Laser Resonator spacer and base plate made of Invar (FeNi36 / ) –low thermal expansion 8x10 -7 / K (average 20-50°C) (thermal change of optical path length in air at const. pressure - 9x10 -7 / K) Diode laser power monitor
©LZH ZA GEO 600 Slave Laser
©LZH ZA GEO 600 Slave Laser
©LZH ZA GEO 600 Slave Laser
©LZH ZA “Long Term” Stability Maximum power after two mirrors and an adjustable attenuator consisting of a polarizer a half wave plate and a 2nd polarizer. Laser left untouched, attenuator varied for different purposes 2 % / 1.5 % pump power drop observed over full 21 day period
©LZH ZA “Long Term” stability II (20 h preliminary) All other acquired data stable to measurement resolution –room temperature: 1 K –pump power: 0.2 % –output power : 1%
©LZH ZA Slave Intensity Noise Suppression
©LZH ZA Slave Intensity Noise Suppression Transfer of Pump Current Modulation to Amplitude Modulation
©LZH ZA Slave Intensity Noise Suppression Full Open Loop Transferfunction of AM Servo (preliminary setup)
©LZH ZA Slave Intensity Noise Suppression First Results (of preliminary setup)
©LZH ZA Power Scaling of End Pumped Nd:YAG
©LZH ZA Power Scaling of End Pumped Nd:YVO 4 Advantages of Nd:YVO 4 1) amplifies 1064 nm emission of Nd:YAG (? at what temperature difference ?) birerefingence n a = 1.96 / n c = 2.17 no depolarization emission || = 25x cm -2 = 7x cm -2 polarized emission large product of || sp ( sp 90 s) loss insensitive high gain lasers 8 nm broad 808 nm low requirements on pump diodes Disadvantage of Nd:YVO 4 1) low pump intensity damage threshold 58 W / mm 0.5 % doping 29 W / mm 1.0 % doping increased by 50 % by undoped endcaps 1) Data from Y.-F. Chen, IEEE J. Q. E. 35(2), 234 (1999) / Tsunekane et. al. Elt. Lett. 32(1), 41 (1996) / VLOC, Casix, Castech web pages
©LZH ZA Problems of the slave Atmospheric pressure changes – p dl/(l dp) 2.8x10 -7 / hPa –50 hPa and 0.5 m 7 m Mirrors on single long range piezos tilt – 10 rad / m Long range piezos have large low frequency resonances
©LZH ZA Possible Solutions Sophisticated piezo mount pre tension / damping / thick mirrors multiple piezos Thermal length actuator 30 mm Al/FeNi36 0.5 m / K pessimistic assumption: f 10 6 Hz / Hz 1/2, f x-over 0.01 Hz piezo: l RMS 10 nm Hermetically airproof resonator constant density of air nearly constant optical path length expansion dependent on spacer material only Suprainvar / Zerodur / ULE