arXiv subjects

Julien Claudon

Publications and source records attributed to Julien Claudon.

25 records · Page 2Linked to original sources

arXiv2011

Observation of a stronger-than-adiabatic change of light trapped in an ultrafast switched GaAs-AlAs microcavity

We study the time-resolved reflectivity spectrum of a switched planar GaAs-AlAs microcavity. Between 5 and 40 ps after the switching (pump) pulse we observe a strong excess probe reflectivity and a change of the frequency of light trapped in the cavity up to 5 linewidths away from the cavity resonance. This frequency change does not adiabatically follow the fast-changing cavity resonance. The frequency change is attributed to an accumulated phase change due to the time-dependent refractive index. An analytical model predicts dynamics in qualitative agreement with the experiments, and points to crucial parameters that control future applications.

physics.optics↗

arXiv2011

Surface effects in a semiconductor photonic nanowire and spectral stability of an embedded single quantum dot

We evidence the influence of surface effects for InAs quantum dots embedded into GaAs photonic nanowires used as efficient single photon sources. We observe a continuous temporal drift of the emission energy that is an obstacle to resonant quantum optics experiments at the single photon level. We attribute the drift to the sticking of oxygen molecules onto the wire, which modifies the surface charge and hence the electric field seen by the quantum dot. The influence of temperature and excitation laser power on this phenomenon is studied. Most importantly, we demonstrate a proper treatment of the nanowire surface to suppress the drift.

cond-mat.mes-hall↗

arXiv2011

Non-linear coupling between the two oscillation modes of a dc-SQUID

We make a detailed theoretical description of the two-dimensional nature of a dc-SQUID, analyzing the coupling between its two orthogonal phase oscillation modes. While it has been shown that the mode defined as "longitudinal" can be initialized, manipulated and measured, so as to encode a quantum bit of information, the mode defined as "transverse" is usually repelled at high frequency and does not interfere in the dynamics. We show that, using typical parameters of existing devices, the transverse mode energy can be made of the order of the longitudinal one. In this regime, we can observe a strong coupling between these modes, described by an Hamiltonian providing a wide range of interesting effects, such as conditional quantum operations and entanglement. This coupling also creates an atomic-like structure for the combined two mode states, with a V-like scheme.

cond-mat.mes-hall↗

arXiv2011

Ultimate fast optical switching of a planar microcavity in the telecom wavelength range

We have studied a GaAs-AlAs planar microcavity with a resonance near 1300 nm in the telecom range by ultrafast pump-probe reflectivity. By the judicious choice of pump frequency, we observe a ultimate fast and reversible decrease of the resonance frequency by more than half a linewidth due to the instantaneous electronic Kerr effect. The switch-on and switch-off? of the cavity is only limited by the cavity storage time of ?tcav = 0.3ps and not by intrinsic material parameters. Our results pave the way to supra-THz switching rates for on-chip data modulation and real-time cavity quantum electrodynamics.

physics.optics↗

arXiv2010

Optical characterization and selective addressing of the resonant modes of a micropillar cavity with a white light beam

We have performed white-light reflectivity measurements on GaAs/AlAs micropillar cavities with diameters ranging from 1 μm up to 20 μm. We are able to resolve the spatial field distribution of each cavity mode in real space by scanning a small-sized beam across the top facet of each micropillar. We spectrally resolve distinct transverse optical cavity modes in reflectivity. Using this procedure we can selectively address a single mode in the multimode micropillar cavity. Calculations for the coupling efficiency of a small-diameter beam to each mode are in very good agreement with our reflectivity measurements.

physics.optics↗

arXiv2009

Measuring the true quality factor of an ultrafast photonic microcavity: homogeneous versus inhomogeneous broadening

We have measured time-resolved the photon storage time and the quality factor of an ultrafast photonic cavity using an autocorrelator. The cavity consists of a $λ$-thick GaAs layer sandwiched between GaAs/AlAs distributed Bragg reflectors and resonates at 985 nm wavelength. The inverse relative linewidth measured with white light reflectivity is 830, while the quality factor obtained from the time resolved measurements is 1500. The photon storage time in the cavity is 0.78 ps. We show that the difference between the quality factor and the inverse relative linewidth results from inhomogeneous broadening of the microcavity resonance due to a spatial gradient in the cavity layer.

physics.optics↗

arXiv2008

Rabi-like oscillations of an anharmonic oscillator: classical versus quantum interpretation

We have observed Rabi-like oscillations in a current-biased dc SQUID presenting enhanced coherence times compared to our previous realization \cite{Claudon_PRL04}. This Josephson device behaves as an anharmonic oscillator which can be driven into a coherent superposition of quantum states by resonant microwave flux pulses. Increasing the microwave amplitude, we study the evolution of the Rabi frequency from the 2-level regime to the regime of multilevel dynamics. When up to 3 levels are involved, the Rabi frequency is a clear signature of quantum behavior. At higher excitation amplitude, classical and quantum predictions for the Rabi frequency converge. This result is discussed in the light of a calculation of the Wigner function. In particular, our analysis shows that pronounced quantum interferences always appear in the course of the Rabi-like oscillations.

cond-mat.mes-hall↗