Dual-frequency VECSELs for Cs clocks (Conference Presentation)

The generation of optically carried radio frequency (RF) is an important issue in the area of microwave photonics (MWP), which has gained tremendous developments and has a bright future [1]. Dual-frequency vertical-external-cavity surface-emitting laser (DF-VECSEL) [2], sustaining two cross-polarized laser in a same optical cavity, is an attractive solution to generate such an optically carried RF signal. With class-A dynamics, DF-VECSEL can exhibit a low intensity noise and be free of relaxation oscillation (RO), due to the fact that the lifetime of the photons inside the external cavity can be longer than the lifetime of the semiconductor gain media carriers. Additionally, DF-VECSEL is also interesting for atomic clocks. Indeed, coherent population trapping (CPT) atomic clock [3] is promising to realize miniaturized atomic clocks, but requires a trade-off between performance and size. Recently, a report gives out a solution using two pulses and a double lambda atomic system to obtain high contrast Ramsey fringes [4]. It is expected that the trade-off can be improved by the combination of DF-VESCEL and the double lambda atomic system configuration of CPT atomic clocks [5]. One key parameter of the DF-VECSEL for such applications is its noise. We report in this paper our efforts to understand the origin of the amplitude and phase noises of the laser and to reduce these noises by optimizing the laser cavity design and the pumping architecture. 1. J. Capmany, Jose and D. Novak. Nature Photonics 1, 319 (2007). 2. G. Baili, L. Morvan, M. Alouini, D. Dolfi, F. Bretenaker, I. Sagnes, and A. Garnache. Opt Lett. 34, 3421 (2009). 3. J. Vanier, Appl. Phys. B 81, 421 (2005). 4. T. Zanon et al., Phys. Rev. Lett. 94, 193002 (2005). 5. P. Dumont et al. J. Lightwave Technol. 32, 3817 (2014.