Hannover 2013 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 8: Precision measurements and metrology II (with Q)

A 8.6: Vortrag

Montag, 18. März 2013, 15:30–15:45, F 128

Broadband femtosecond filtering cavities for quantum limited projective metrology — •Roman Schmeissner, Valerian Thiel, Jonathan Roslund, Claude Fabre, and Nicolas Treps — Laboratoire Kastler Brossel, 4 Place Jussieu, 75252 Paris cedex 05, France

We have shown theoretically that balanced homodyne detection with a temporally shaped local oscillator extracts timing information and any other parameter of femtosecond(fs)-pulses with ultimate sensitivity [1]. To reach limits predicted by information theory, the scheme requires a laser beam that is quantum-limited in amplitude and phase. We propose to use optical cavities: they are intrinsic, passive low-pass filters that address frequency scales difficult to reach with active feedback mechanisms. Similar systems are used for broadband spectroscopy [2,3]. We construct and characterize a readily implementable filtering cavity that is simultaneously resonant over 100nm. This exceptional broadband property enables a wide range of applications from parameter estimation to ultra-precise spectroscopy. When seeded with a 25fs frequency comb, intensity and phase noise are reduced by up to 10dB at and below the relaxation oscillation band at 1MHz. Furthermore, noise quadrature interconversion enables qualitative identification of phase noise at sidebands above 100kHz. In conclusion, a frequency comb that is quantum limited in amplitude and phase for frequencies larger than 500kHz is obtained from a commercial Ti:Sa laser system.

[1] B. Lamine et al., Phys. Rev. Lett. 101, 2008, 123601, 1-4 [2] Ch. Gohle et al., Phys. Rev. Lett. 100, 2008, 1-4 [3] M.J. Thorpe et al., Optics Express 16, 2008, 2387-2397