Séminaire : ‘Optical Frequency Combs for Ultra-Low Phase-Noise Microwave Signal Generation and Laser Activities at LP2N ‘

Speaker : Giorgio Santarelli (LP2N-Bordeaux)
Date : 31 January at 11h00
Location :  Amphiteather IEMN-LCI

Low-phase-noise and frequency stable microwave signals are crucial for a wide variety of scientific and technological applications including atomic frequency standards, phased-array radars, arbitrary waveform generation, photonic processing and very long baseline interferometry. One challenging aim for researchers has been the development of a single device that exhibits the ultimate performance in multiple aspects of signal purity for instance to have low phase fluctuations across the spectrum from low Fourier frequencies (1Hz) out to the highest (1MHz) frequencies of interest. One promising route is the low-noise optical frequency division of a laser that has been stabilized to a mode of a vibration-insensitive reference cavity. In these circumstances the divided signal carries the frequency stability of the original signal while delivering an improved signal-to-noise ratio by the division of the phase fluctuations. The photonic shot noise in optical to electrical pulse conversion in a photodiode which was believed to impair the ultra-low phase noise generation has been greatly improved by combining pulse interleavers for increased effective repetition rates and apparent sub-shot-noise photodetection ([1]). With this last technique, it was shown that the shot-noise limit is greatly improved over that of cw lasers in the short (<1ps) optical pulses limit. There have been several developments in the field of photonic microwave synthesis showing very low absolute or residual phase noise using femtosecond frequency combs based on either modelocked Ti:Sapphire and Erbium fiber lasers [2,3]. Fibre systems are morecompact, robust and power efficient than Ti:Sapphire, very recently we have demonstrated the lowest phase noise by of -106(<-173) dBc/Hz@1Hz(10kHz) offset carrier. I will present a review the recent advances in this domain and the latest results [4]. In addition, I will shortly present laser developments at LP2N [5].

[1]F. Quinlan et al. “Exploiting shot noise correlations in the photodetection of ultrashort optical pulse trains”, Nature Photonics, 7, p. 290 (2013). [2]T. M. Fortier, F. Quinlan, A. Hati, C. Nelson, J. A. Taylor, Y. Fu, J. Campbell, and S. A. Diddams, « Photonic microwave generation with high-power photodiodes, » Opt. Lett. 38, 1712-1714 (2013) [3]F. Quinlan, F. N. Baynes, T. M. Fortier, Q. Zhou, A. Cross, J. C. Campbell, and S. A. Diddams, « Optical amplification and pulse interleaving for low-noise photonic microwave generation, » Opt. Lett. 39, 1581-1584 (2014). [4]X.Xieet al., G. Santarelli, and Y. Le Coq, « ) Photonic microwave signals with zeptosecond-level absolute timing noise » Nat. Phot.(2016). [5]G. Guiraud, N. Traynor, G. Santarelli, « High-power and low-intensity noise laser at 1064nm, » Opt. Lett. 41, 4040-4043