7 March 2014 Generation of high-purity microwave signals from a dual-frequency OP-VECSEL
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Coherent population trapping (CPT) is an interesting technique for the development of compact atomic frequency references. We describe an innovating laser source for the production of the two cross-polarized coherent laser fields which are necessary in CPT-based atomic clocks. It relies on the dual-frequency and dual-polarization operation of an optically-pumped vertical external-cavity semiconductor laser. This particular laser emission is induced by intracavity birefringent components which produce a controllable phase anisotropy within the laser cavity and force emission on two cross-polarized longitudinal modes. The laser emission is tuned at the Cs D2 line (λ = 852.14 nm), and the frequency difference Δν between the two laser modes is tunable in the microwave range. The laser line wavelength is stabilized onto an atomic hyperfine transition, and concurrently the frequency difference is locked to an ultra-low noise RF oscillator at 9.2 GHz. The high spectral purity of the optically-carried microwave signal resulting from the beatnote of the two cross-polarized laser lines is assessed through its narrow spectral linewidth (<30 Hz) as well as its low phase noise (≤ -100 dBrad2/Hz). The performance of this laser source is already adequate for the interrogation of atoms in a CPT atomic clock, and should result in an estimated relative stability of 3.10-13τ-1/2 – one order of magnitude better than commercial atomic clocks.
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Fabiola Camargo, Fabiola Camargo, Gaëlle Lucas-Leclin, Gaëlle Lucas-Leclin, Paul Dumont, Paul Dumont, Patrick Georges, Patrick Georges, Jean-Marie Danet, Jean-Marie Danet, David Holleville, David Holleville, Stéphane Guerandel, Stéphane Guerandel, Gregoire Pillet, Gregoire Pillet, Ghaya Baili, Ghaya Baili, Loic Morvan, Loic Morvan, Daniel Dolfi, Daniel Dolfi, Iryna Gozhyk, Iryna Gozhyk, Grégoire Beaudoin, Grégoire Beaudoin, Isabelle Sagnes, Isabelle Sagnes, } "Generation of high-purity microwave signals from a dual-frequency OP-VECSEL", Proc. SPIE 8966, Vertical External Cavity Surface Emitting Lasers (VECSELs) IV, 89660L (7 March 2014); doi: 10.1117/12.2041669; https://doi.org/10.1117/12.2041669


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