PDF《of 220 W》

Appl Phys B (2011) 102: 529C538 DOI 10.

1007/s00340-011-4411-9 Injection-locked single-frequency laser with an output power of

220 W L. Winkelmann ・ O. Puncken ・ R. Kluzik ・ C. Veltkamp ・ P. Kwee ・ J. Poeld ・ C. Bogan ・ B. Willke ・ M. Frede ・ J. Neumann ・ P. Wessels ・ D. Kracht Received:

9 July

2010 / Revised version:

1 October

2010 / Published online:

11 February

2011 ? Springer-Verlag

2011 Abstract A solid-state laser system for the next genera- tion of gravitational wave detectors with an output power of

220 W at the wavelength of

1064 nm is presented. Single- frequency operation of the laser was achieved by injection- locking of a high-power ring oscillator to an ampli?ed non- planar ring oscillator (NPRO) following the PoundCDreverC Hall scheme. The high-power stage which features four lon- gitudinally pumped Nd:YAG laser crystals as active media in a ring resonator con?guration was designed for reliable long term operation. Using a non-confocal ring cavity to ?l- ter the output beam, a pure TEM00 mode with

168 W output power was obtained.

1 Introduction The most promising approach to detect gravitational waves on Earth is based on large scale Michelson interferometers, which perform high precision differential length measure- ments. The largest detectors of this kind are the Laser In- terferometer Gravitational Wave Observatories (LIGO) in the USA [1]. Two of these detectors (with

4 and

2 km L. Winkelmann ( ) ・ O. Puncken ・ R. Kluzik ・ C. Veltkamp ・ M. Frede ・ J. Neumann ・ P. Wessels ・ D. Kracht Laser Zentrum Hannover e.V., Hollerithallee 8,

30419 Hannover, Germany e-mail: [email protected] P. Kwee ・ J. Poeld ・ C. Bogan ・ B. Willke Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) und Leibniz Universit?t Hannover, Callinstr. 38,

30167 Hannover, Germany B. Willke ・ J. Neumann ・ P. Wessels ・ D. Kracht Centre for Quantum-Engineering and Space-Time Research―QUEST, Welfengarten 1,

30167 Hannover, Germany arm length) are merged in one observatory located at Han- ford, Washington. The third observatory was built near Liv- ingston, Louisiana, and contains a

4 km Michelson interfer- ometer. Both observatories inherit the highest sensitivity of today'

s gravitational wave detectors and can achieve a de- tection range of more than

30 Mpc for inspiral neutron stars [2]. A key factor for improvement of the sensitivity is to reduce noise sources, which directly couple into the detec- tion signal. One limitation for today'

s LIGO detectors is the shot noise. As the shot noise limited sensitivity scales pro- portionally with the inverse square root of the optical power inside the interferometer, the sensitivity would strongly ben- e?t from a power increase of the laser light source [1]. Be- sides the need of a high output power, the light source has to ful?ll stringent requirements for beam pro?le, pointing, am- plitude and frequency noise not to induce additional noise into the gravitational wave channel [3]. Currently, two

35 W ampli?er systems, developed by Frede et al. [4], are installed at the LIGO sites for the

4 km interferometer and have proven to be well suited as a light source for an interferometric gravitational wave de- tector. For the next major upgrade of the LIGO detectors― advanced LIGO―an output power increase to a level of more than

165 W in a pure Gaussian beam is desired [5]. To ful?ll this requirement, a high-power oscillator, which can be injection-locked to the existing