1、LISA symp 19-24 July 02, PSU,1,Technologies for the Future of interferometric detectors,C. Nary MAN UMR 6162, Observatoire Cote dAzur, BP 4229, 06304 Nice Cedex 4, France,Introduction : fundamental limits of ground-based detectors Possible solutions in the MF range: High power lasers new materials f
2、or optics controls of optics behaviour A lot of ideas to extract better signals with sophisticated configurations of signal recycling. Other optical configurations ,LISA symp 19-24 July 02, PSU,2,Sensitivity curve and fundamental limitations,LISA symp 19-24 July 02, PSU,3,Issues in MF range,LISA sym
3、p 19-24 July 02, PSU,4,High power single-frequency laser,Stringent demands on frequency stability 10-6 Hz/Hz (of ground-based detectors):,LISA symp 19-24 July 02, PSU,5,Rod Laser systems,LISA symp 19-24 July 02, PSU,6,Realized (02): 4 diode boxes have been set up (1200 W of pump power) temperature s
4、tabilization pump light homogenization has been demonstrated 45 W single mode and 75 W multi mode laser has been demonstrated (single rod, no compensation),LZH: Power scaling of End Pumped rod to 100W,Modeling :100 W of output power will be achieveable aberrations , to be compensated for aberrations
5、 comparable in end pumped and transversally pumped rod,LISA symp 19-24 July 02, PSU,7,Adelaide 100 W slab laser configuration,Nd:YAG slab pumped by 520 W fibre-coupled diode lasers Resonator stable in the zig-zag H direction, unstable in V direction,LISA symp 19-24 July 02, PSU,8,Stanford MOPA desig
6、n,LISA symp 19-24 July 02, PSU,9,High power lasers: ceramic lasers,Ceramic laser : any size (23 cm long max for YAG xtals, twice this length for ceramic), any shape, high Nd doping, mass production,first Nd:YAG ceramic laser gives 300 mW output (Ikesue et al. in 1995),Quality of the beam has to be w
7、orked out Wavefront quality, distributions of Nd ions to be compared vs xtals Possibility of having Nd:Y2O3 ceramic where thermal conductivity twice of YAG with similar thermal expansion coef.,LISA symp 19-24 July 02, PSU,10,High power lasers: Fiber lasers,Erbium doped Silica Ytterbium doped all gla
8、ss (eff 80%) Ytterbium doped Silica (eff 85%),Used as power amplifier with NPRO, emits 20 W on single-frequency output (Jena, 2001) Possibility of scaling up to 100 W with 9m fiber.,Fiber lasers based on rare-earth doped silica: very high output powers up to 2 kW cw operation in June 02 (IPG Photoni
9、cs).,LISA symp 19-24 July 02, PSU,11,Substrate for future mirrors,low absorption material with good conductivity, high Q, good optical quality .Fused Silica (today substrate): Absorption: best quality has 0.7 ppm/cm Numata et al (Amaldi 01): measured Q of 13 kinds of FS, Q = 7.105 to 4.107 : no simp
10、le correlation with known specs, seems to increase with annealing process Homogeneity and roughness of polishing: meet specs,Sapphire: Absorption : around 20 ppm/cm, vary following samples Q = 6.5x 107 at room temperature and low temperatures behavior studied extensively, but direct measurement of t
11、hermal noise necessary Homogeneity: need to be improved by factor 5 to 10 (Caltech, CSIRO),Silicon: Used in reflection only (suitable for all-reflective interferometers) Q around 2x108 confirmed for a variety of samples, thermal noise improves at low T,LISA symp 19-24 July 02, PSU,12,New Candidate M
12、aterials for mirrors: CaF2,(VIRGO, Elba 2002 ),Low absorption, high resistance to thermal & mech shocks, high Q, good candidate for cryogenic solution (Silicate bonding not working ),LISA symp 19-24 July 02, PSU,13,Coatings: optical performances (1),Optical performances achieved today in Virgo-SMA:,
13、LISA symp 19-24 July 02, PSU,14,Coatings : optical performances (2),LISA symp 19-24 July 02, PSU,15,Coatings : mechanical loss,LISA symp 19-24 July 02, PSU,16,Thermal effects,LISA symp 19-24 July 02, PSU,17,Compensation of wavefront deformations,Mirror heating with outer ring and scanned beam heatin
14、g (MIT),M.Zucker LSC meeting 02,Ottaway PAC 12,LISA symp 19-24 July 02, PSU,18,Laser cooling of solids,1929: anti-Stokes fluorescence is basis of optical refrigeration cycle.,60 s: GaAs, Nd:YAG, 90 s; Yb doped ZBLAN: up to 48C (Los Alamos),Applications to GW detectors: Identify materials also with h
15、igh Q, high homegeneity Recycle the anti-Stokes fluorescence to remove its th.effects out of the solid,LISA symp 19-24 July 02, PSU,19,All-reflective interferometers,Advantages: Higher light power because no bulk absorption Use of test mass materials giving lower thermal noise such as xtal silicon,D
16、rawbacks come from use of gratings: Conversion of laser frequency noise to pointing noise: retroreflecting compensator Laser center frequency drift max deviation Distort spatial profile of diffracted beam Scattered light Improvement needed,Experimental demonstration in 98 by Sun & Byer in a Sagnac c
17、onfiguration,LISA symp 19-24 July 02, PSU,20,+ signal recycling configurations,Future detector: with thermal correction/compensation,LISA symp 19-24 July 02, PSU,21,LISA symp 19-24 July 02, PSU,22,Intelligent digital controls,Digital electronics to monitor and control the complex seismic isolation (
18、gain and phase re-adjusted automatically with the drift /ageing of mechanics due to environment) Low noise digital electronics for all position controls (test-mass, laser beam, beam shape, beam pointing, etc),Fast digital electronics to lock the laser parameters (frequency, amplitude),Neural networks to manage all the controls , from the locks sequence, the automatic relocks of each servo, the electronic gain/phase adjustments due to the ageing of mechanical actuators, etc,also the kind of signal extraction ?,
