Femtosecond spectral electric field reconstruction using coherent transients

We have implemented a new approach for measuring the time-dependent intensity and phase of ultrashort optical pulses. It is based on the interaction between shaped pulses and atoms, leading to coherent transients.Comment: 4 pages Accepted in Optics Letter

Time-dependent photoionization of azulene: Optically induced anisotropy on the femtosecond scale

We measure the photoionization cross-section of vibrationally excited levels in the S2 state of azulene by femtosecond pump-probe spectroscopy. At the wavelengths studied (349-265 nm in the pump) the transient signals exhibit two distinct and well-defined behaviours: (i) Short-term (on the order of a picosecond) polarization dependent transients and (ii) longer (10 ps - 1 ns) time-scale decays. This letter focuses on the short time transient. In contrast to an earlier study by Diau et al.22 [J. Chem. Phys. 110 (1999) 9785.] we unambiguously assign the fast initial decay signal to rotational dephasing of the initial alignment created by the pump transition.Comment: Chemical Physics Letters (2008

Real time Quantum state holography using coherent transients

In a two level atom, real-time quantum state holography is performed through interferences between quantum states created by a reference pulse and a chirped pulse resulting in coherent transients. A sequence of several measurements allows one to measure the real and imaginary parts of the excited state wave function. These measurements are performed during the interaction with the ultrashort laser pulse. The extreme sensitivity of this method to the pulse shape provides a tool for electric field measurement

Bose-Einstein condensate source on a optical grating-based atom chip for quantum sensor applications

We report the preparation of Bose-Einstein condensates (BECs) by integrating laser cooling with a grating magneto-optical trap (GMOT) and forced evaporation in a magnetic trap on a single chip. This new approach allowed us to produce a $6 \times 10^4$ atom Bose-Einstein condensate of rubidium-87 atoms with a single laser cooling beam. Our results represent a significant advance in the robustness and reliability of cold atom-based inertial sensors, especially for applications in demanding field environments

Mesoscopic self-collimation and slow light in all-positive index layered photonic crystals

We demonstrate a mesoscopic self-collimation effect in photonic crystal superlattices consisting of a periodic set of all-positive index 2D photonic crystal and homogeneous layers. We develop an electromagnetic theory showing that diffraction-free beams are observed when the curvature of the optical dispersion relation is properly compensated for. This approach allows to combine slow light regime together with self-collimation in photonic crystal superlattices presenting an extremely low filling ratio in air.Comment: 4 pages, 4 figure

Ionization effects on spectral signatures of quantum-path interference in high-harmonic generation

The interference between the emission originating from the short and long electron quantum paths is intrinsic to the high harmonic generation process. We investigate the universal properties of these quantum-path interferences in various generation media and discuss how ionization effects influence the observed interference structures. Our comparison of quantum-path interferences observed in xenon, argon, and neon demonstrates that our experimental tools are generally applicable and should also allow investigating more complex systems such as molecules or clusters

High frequency operation of an integrated electro-absorption modulator onto a vertical-cavity surface-emitting laser

We present in this paper the vertical integration of an electro-absorption modulator (EAM) onto a vertical-cavity surface-emitting laser (VCSEL). We discuss the design, fabrication, and measured characteristics of the combined VCSEL and EAM. We previously demonstrated a standalone EAM with an optical bandwidth around 30 GHz. In this paper we present for the first time an optical bandwidth of 30 GHz for an EAM integrated onto a VCSEL. This device exhibits single-mode operation and a very low chirp, below 0.1 nm, even with a modulation depth of 70% which makes this device very competitive for high-speed communications in data centers

Lumière façonnée et matière structurée (et vice versa)

National audienceThis document presents the research and teaching in both coherent control and ultrashort laser pulse shaping and in sub-wavelength structuring for photonics integration.Ce document retrace les activités de recherche et d'enseignements menées dans le domaine du contrôle cohérent et du façonnage d'impulsions laser, ainsi que dans le domaine des structures sub-longueur d'onde pour l'intégration photonique