248 research outputs found
Analog Hawking radiation from an acoustic black hole in a flowing polariton superfluid
No full textWe theoretically study the analog Hawking radiation processes from an analog acoustic black hole in a flowing superfluid of exciton-polaritons in a one-dimensional semiconductor microcavity. Polaritons are coherently injected into the microcavity by a laser pump with a suitably tailored spot profile. An event horizon with a large analog surface gravity is created by inserting a defect in the polariton flow along the cavity plane. Experimentally observable signatures of the analog Hawking radiation are identified in the scattering of phonon wave packets off the horizon, as well as in the spatial correlation pattern of quantum fluctuations of the polariton density. The potential of these tabletop optical systems as analog models of gravitational physics is quantitatively confirmed by numerical calculations using realistic parameters for state-of-the-art devices
Pumping and dissipation as an asset for topological photonics
No full textIn this talk I will review some general aspects about the different ways of injecting light into a topological photonics system and of extracting information about its dynamics from the emitted light. Rather than just a hindrance, the intrinsically non-equilibrium nature of optical systems can in fact be seen as a promising asset in view of exploring new physics beyond what is normally done in condensed-matter and ultracold atom systems.
In the first part, I will review the basic features of the principal pumping schemes used in experi- ments on quantum fluids of light [1] and topological photonics. In particular, I will illustrate how these features have been exploited in recent experiments to highlight different aspects of topological physics.
In the second part, I will present some theoretical proposals of new effects that can be studied in state-of-the-art systems of current interest for topological photonics. Our long term goal is to push further the research on topological photonics in the direction of generating strongly correlated states of light in strongly nonlinear systems [2, 3] and observe novel phase transitions in a driven-dissipative context [4].
References
[1] I. Carusotto and C. Ciuri, Quantum fluids of light, Rev. Mod. Phys. 85, 299 (2013)
[2] E. Macaluso and I. Carusotto, Hard-wall confinement of a fractional quantum Hall liquid, arXiv:1706.00353.
[3] R. O. Umucallar and I. Carusotto, Spectroscopic signatures of a Laughlin state in an incoher- ently pumped cavity, to be submitted.
[4] J.Lebreuillyetal.,Stabilizingstronglycorrelatedphotonfluidswithnon-Markovianreservoirs, arXiv:1704.01106.Non UBCUnreviewedAuthor affiliation: INO-CNR BEC CenterFacult
"Light-force induced fluorescence line-center shifts in high-precision optical spectroscopy"
No full textWe calculate the effect of light-induced forces on the fluorescence line shape of a two-level atom crossing at right angles two counterpropagating light beams of parallel linear polarizations (lin parallel to lin) in a common configuration for ultrahigh-precision optical spectroscopy. For an incident atomic beam with a narrow spread of transverse velocities the dipole force induces a redshift of the fluorescence maximum, while in the reverse case of a wide spread of transverse velocities the radiation-pressure force induces a blueshift of the saturation dip minimum. We then use our theory to explain the blueshift of the saturation line-center dip occurring for the closed transition 2 S-3(1)--> 2 P-3(2) of a He-4 beam. The observed shift, which is in quite good agreement with the theory, can be of the order of 1/10 of the transition natural linewidth and hence quite important for ultrahigh-precision spectroscop
"Atom laser coherence length and atomic standing waves"
No full textWe consider the dynamical Bragg reflection of an atomic matter wave from a finite optical lattice; the resulting energy dependence of the transmittivity allows us to filter out the velocities of the incident atoms. In particular, we show how the coherence length of the incident beam can be inferred from the sharpness of the transmittivity as a function of the lattice intensity. For incident frequencies well inside the reflecting window, the interference of incident and reflected matter waves gives rise to an oscillatory density profile in front of the lattice which can be observed by means of light diffraction. The angular width of the diffracted peaks also provides information on the coherence length of the incident atomic beam
Density correlations and analog dynamical Casimir emission of Bogoliubov phonons in modulated atomic Bose-Einstein condensates
No full textWe present a theory of the density correlations that appear in an atomic Bose-Einstein condensate as a consequence of the emission of correlated pairs of Bogoliubov phonons by a time-dependent atom-atom scattering length. This effect can be considered as a condensed matter analog of the dynamical Casimir effect of quantum field theory. Different regimes as a function of the temporal shape of the modulation are identified and a simple physical picture of the phenomenon is discussed. Analytical expressions for the density correlation function are provided for the most significant limiting cases. This theory is able to explain some unexpected features recently observed in numerical studies of analog Hawking radiation from acoustic black holes.We are grateful to C. Tozzo, F. Dalfovo, E. Cornell,
and P. Calabrese for stimulating exchanges and discussions.
A long-lasting collaboration with C. Ciuti and S.
De Liberato on the Dynamical Casimir Effect is warmly
acknowledged.Peer reviewe
On the role of interactions in trans-sonically flowing atomic condensates
No full textWe provide a joint numerical-analytical study of the physics of a flowing atomic Bose-Einstein condensate in the combined presence of an external trap and a step potential which accelerates the atoms out of the condensate creating a pair of neighbouring black- and white-hole horizons. In particular, we focus on the rapidly growing density modulation pattern that appears in the supersonic region, an experimentally observed feature that was related to black-hole lasing phenomena. A direct assessment of the role of interactions in this process suggests an interpretation of the experimental data in terms of linear interference of atomic waves rather than collective effects. Our conclusions are further supported by an analytical solution of the Schrödinger equation in terms of Airy wave functions
Light-force-induced fluorescence line-center shifts in high-precision optical spectroscopy: simple model and experiment
No full textA simple model that enables to calculate the effects of dipole and radiation-pressure forces on the spectroscopic determination of energy separations was developed. The resulting model provides the means for recovering the redshift as well as for explaining a blueshift of the Lamb dipole line center for a closed transition in a beam of 4He atoms
Atomic recoil effects in slow light propagation
No full textWe theoretically investigate the effect of atomic recoil on the propagation of ultraslow light pulses through a coherently driven Bose-Einstein condensed gas. For a sample at rest, the group velocity of the light pulse is the sum of the group velocity that one would observe in the absence of mechanical effects (infinite mass limit) and the velocity of the recoiling atoms (light-dragging effect). We predict that atomic recoil may give rise to a lower bound for the observable group velocities, as well as to pulse propagation at negative group velocities without appreciable absorption
Two-photon Rabi splitting and optical Stark effect in semiconductor microcavities
No full textWe have studied two-photon nonlinear optical effects arising in a microcavity geometry from resonant two-photon absorption or second-harmonic generation. The transmission spectrum of the cavity is shown to depend on light intensity according to a simple two-level picture with an intensity-dependent coupling: at resonance the system exhibits a two-photon Rabi splitting. The absorption spectrum of a weak probe beam in a pumped cavity is found to strongly depend on pump intensity and detuning; the resulting effect is a sort of two-photon analogue of the usual optical Stark effect. For moderate pump intensities a two-level picture with a pump-dependent coupling can account for the main results, while at higher intensities new unexpected features show up; in particular, we predict the appearance of gain in well-determined spectral regions due to hyper-Raman processes. Finally, we have shown how the coupling coefficients appearing in our formalism can be obtained from a detailed knowledge of the material and geometrical properties of a specific system. For illustrative purposes, we have estimated the required light intensities using realistic data for a GaAs-based semiconductor microcavity. [S0163-1829(99)00932-7]
Nonlinear optics of coupled semiconductor microcavities
No full textIn a coupled microcavity configuration with Ken optical nonlinearities in the external as well as in the central distributed Bragg reflectors, the energies of the closely spaced doublet of delocalized photon eigenmodes change with increasing light intensity. One beam optical bistability as well as all optical switching in a pump and probe configuration can be realized. The nonlinearity can induce a novel kind of Rabi anticrossing between a photonic mode and a nearly resonating quantum well exciton. Realistic numerical simulations of such effects in AlGaAs based microstructures are presented. (C) 1998 Elsevier Science B.V
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