Time filter

Source Type

Borri S.,National Research Council Italy | Borri S.,European Laboratory for Nonlinear Spectroscopy | Bartalini S.,National Research Council Italy | Bartalini S.,European Laboratory for Nonlinear Spectroscopy | And 11 more authors.
IEEE Journal of Quantum Electronics | Year: 2011

By measuring the frequency-noise power spectral density of a cryogenically-cooled mid-infrared quantum cascade laser, we investigate the different contributions to the noise spectrum and identify the main differences with respect to standard bipolar semiconductor devices. In particular, the existence of a thermal cut-off on the 1/f noise allows to identify the current fluctuations through the heterostructure as the physical mechanism, intrinsic to the device, at the basis of the measured flicker noise. This result, marking the difference with bipolar semiconductor devices, is confirmed analyzing the laser frequency response to a modulation of the driving current. © 2011 IEEE.


Wu J.-H.,Jilin University | Horsley S.A.R.,University of Exeter | Artoni M.,European Laboratory for Nonlinear Spectroscopy | Artoni M.,CNR Institute of Acoustics and Sensors Orso Mario Corbino | La Rocca G.C.,Normal School of Pisa
Light: Science and Applications | Year: 2013

The typically tiny effect of radiation damping on a moving body can be amplified to a favorable extent by exploiting the sharp reflectivity slope at one edge of an optically induced stop-band in atoms loaded into an optical lattice. In this paper, this phenomenon is demonstrated for the periodically trapped and coherently driven cold 87Rb atoms, where radiation damping might be much larger than that anticipated in previous proposals and become comparable with radiation pressure. Such an enhancement could be observed even at speeds of only a few meters per second with less than 1.0% absorption, making radiation damping experimentally accessible. © 2013 CIOMP. All rights reserved.


Horsley S.A.R.,University of Exeter | Wu J.-H.,Jilin University | Artoni M.,European Laboratory for Nonlinear Spectroscopy | Artoni M.,CNR Institute of Acoustics and Sensors Orso Mario Corbino | La Rocca G.C.,Normal School of Pisa
American Journal of Physics | Year: 2014

A series of thin layers of alternating refractive index are known to make a good optical mirror over certain bands of frequency. Such a device, often termed the Bragg reflector, is usually introduced to students in isolation from other parts of the curriculum. Here, we show that the basic physics of wave propagation through a stratified medium can be used to illustrate some more modern developments in optics and quantum physics, from transfer matrix techniques to the optical properties of cold trapped atoms and optomechanical cooling. We also show a simple example of how such systems exhibit an appreciable level of optical nonreciprocity. © 2014 American Association of Physics Teachers.


Wu J.-H.,Jilin University | Artoni M.,European Laboratory for Nonlinear Spectroscopy | Artoni M.,University of Brescia | La Rocca G.C.,Normal School of Pisa
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Elaborating versatile strategies for new lasing schemes is important for both fundamental research and realistic applications. By using atomic photonic crystals, two-color distributed feedback lasing can be shown to occur in a nonlinear regime of balanced optical gain. Within the context of a simple model based on coupled-wave theory and applied to alkali-metal-atom crystals, we find that the two-color lasing threshold in cold atoms is within state-of-the-art experimental reach. © 2013 American Physical Society.


Wu J.-H.,Jilin University | Artoni M.,CNR Institute of Acoustics and Sensors Orso Mario Corbino | Artoni M.,European Laboratory for Nonlinear Spectroscopy | La Rocca G.C.,Normal School of Pisa
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

Fourier-expanded Maxwell-Liouville equations are employed to study the light pulse dynamics in atomic samples coherently driven by a standing-wave light field. Solutions are obtained by a suitable truncation of the Maxwell-Liouville equations that contain the number of spin and optical Fourier coherence components appropriate to the sample temperature. This approach is examined here for cold but thermal atoms where the Doppler broadening is still not negligible and familiar secular approximations no longer hold. In this temperature regime higher-order momentum Fourier coherence components are shown to be important for achieving excellent agreement with a recent experiment done in cold Rb87 clouds at several hundred microkelvins. © 2010 The American Physical Society.


Horsley S.A.R.,University of Exeter | Artoni M.,University of Brescia | Artoni M.,European Laboratory for Nonlinear Spectroscopy | La Rocca G.C.,Normal School of Pisa
Nature Photonics | Year: 2015

When a planar dielectric medium has a permittivity profile that is an analytic function in the upper or lower half of the complex position plane x=x'+ix'' then the real and imaginary parts of its permittivity are related by the spatial Kramers-Kronig relations. We find that such a medium will not reflect radiation incident from one side, whatever the angle of incidence. Using the spatial Kramers-Kronig relations, one can derive a real part of a permittivity profile from some given imaginary part (or vice versa) such that the reflection is guaranteed to be zero. This result is valid for both scalar and vector wave theories and may have relevance for designing materials that efficiently absorb radiation or for the creation of a new type of anti-reflection surface. © 2015 Macmillan Publishers Limited.


Horsley S.A.R.,University of St. Andrews | Horsley S.A.R.,University of York | Artoni M.,European Laboratory for Nonlinear Spectroscopy | Artoni M.,University of Brescia | La Rocca G.C.,Normal School of Pisa
Physical Review Letters | Year: 2011

The force exerted on a material by an incident beam of light is dependent upon the material's velocity in the laboratory frame of reference. This velocity dependence is known to be difficult to measure, as it is proportional to the incident optical power multiplied by the ratio of the material velocity to the speed of light. Here we show that this typically tiny effect is greatly amplified in multilayer systems composed of resonantly absorbing atoms exhibiting ultranarrow photonic band gaps. The amplification effect for optically trapped Rb87 is shown to be as much as 3 orders of magnitude greater than for conventional photonic-band-gap materials. For a specific pulsed regime, damping remains observable without destroying the system and significant for material velocities of a few ms⊃-1. © 2011 American Physical Society.


Horsley S.A.R.,University of Exeter | Horsley S.A.R.,European Laboratory for Nonlinear Spectroscopy | Artoni M.,European Laboratory for Nonlinear Spectroscopy | Artoni M.,CNR Institute of Acoustics and Sensors Orso Mario Corbino | La Rocca G.C.,Normal School of Pisa
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

A general theory of optical forces on moving bodies is here developed in terms of generalized 4×4 transfer and scattering matrices. Results are presented for a planar dielectric of arbitrary refractive index placed in an otherwise empty space and moving parallel and perpendicular to the slab-vacuum interface. In both regimes of motion the resulting force comprises lateral and normal velocity-dependent components, which may depend in a subtle way on the Doppler effect and s-p-polarization mixing. For lateral displacements in particular, polarization mixing, which is here interpreted as an effective magnetoelectric effect due to the reduced symmetry induced by the motion of the slab, gives rise to a velocity-dependent force contribution that is sensitive to the phase difference between the two polarization amplitudes. This term gives rise to a rather peculiar optical response on the moving body, and specific cases are illustrated for incident radiation of arbitrarily directed linear polarization. The additional force due to polarization mixing may cancel to first order in V/c with the first order Doppler contribution yielding an overall vanishing of the velocity-dependent component of the force on the body. The above findings bear some relevance to modern developments of nano-optomechanics and to the problem of the frictional component of the Casimir force. © 2012 American Physical Society.


Horsley S.A.R.,University of St. Andrews | Artoni M.,European Laboratory for Nonlinear Spectroscopy | Artoni M.,CNR Institute of Acoustics and Sensors Orso Mario Corbino | La Rocca G.C.,Normal School of Pisa
Journal of the Optical Society of America B: Optical Physics | Year: 2012

The dependence of macroscopic radiation pressure on the velocity of the object being pushed is commonly attributed to the Doppler effect. This need not be the case, and here we highlight velocity-dependent radiation pressure terms that have their origins in the mixing of s and p polarizations brought about by the Lorentz transformation between the lab and the material rest frame, rather than in the corresponding transformation of frequency and wavevector. The theory we develop may be relevant to the nano-optomechanics of moving bodies. © 2012 Optical Society of America.


Wu J.-H.,Northeast Normal University | Artoni M.,European Laboratory for Nonlinear Spectroscopy | Artoni M.,University of Brescia | La Rocca G.C.,Normal School of Pisa
Physical Review Letters | Year: 2014

Light propagation in optical lattices of driven cold atoms exhibits non-Hermitian degeneracies when the first-order modulation amplitudes of real and imaginary parts of the probe susceptibility are manipulated to be balanced. At these degeneracies, one may observe complete unidirectional reflectionless light propagation. This strictly occurs with no gain and can be easily tuned and fully reversed as supported by the transfer-matrix calculations and explained via a coupled-mode analysis. © 2014 American Physical Society.

Loading European Laboratory for Nonlinear Spectroscopy collaborators
Loading European Laboratory for Nonlinear Spectroscopy collaborators