Two-color lasing in cold atoms

Wu, Jin-Hui; Artoni, M.; Rocca, G. C. La

doi:10.1103/physreva.88.043823

Cited by 11 publications

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“…(1), can be achieved and made completely reversible in two opposite directions. The underlying physical mechanism is illustrated by considering a lattice of driven cold atoms [25][26][27][28][29] whose probe susceptibility is such that χ p ðzÞ ¼ −χ Ã p ð−zÞ with loss and no gain, which is clearly not a PT-symmetric case [30,31]. We engineer a far-detuned dressing field so as to induce a spatially modulated frequency shift along the lattice axis in quadrature with respect to the atomic density (see Fig.…”

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Non-Hermitian Degeneracies and Unidirectional Reflectionless Atomic Lattices

2014

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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. DOI: 10.1103/PhysRevLett.113.123004 PACS numbers: 37.10.Jk, 11.30.Er, 42.25.Bs, 42.50.Gy Much attention has been devoted to the development of artificial metamaterials for achieving optical functionalities not available in nature. Photonic crystals [1] and lefthanded materials [2] are prominent instances tailored to stretch the rules of light propagation and interaction. Such metamaterials have seeded new paradigms in optical, optoelectronic, and optomechanical devices [3][4][5][6]. Nevertheless, some tasks are more difficult than others with unidirectional light transport being a most pronounced example. Significant progress has been made in recent years by developing optical materials with parity-time (PT) symmetry to attain unidirectional light invisibility [7][8][9][10][11][12][13][14][15][16]. PT-symmetric metamaterials require a delicate balance of gain and loss whereby the complex refraction index satisfies nðzÞ ¼ n Ã ð−zÞ and are typically made of periodic solid microstructures. Homogeneous atomic vapors driven into three-level [17,18] or four-level [19] configurations have also been proposed to realize PT-symmetric optical potentials via rather complicated spatial modulations of two driving fields. Such proposals have obvious advantages of real-time all-optical reconfigurable capabilities and implicit disadvantages of intractable field modulations and considerable symmetry errors. Large optical nonreciprocities may also be achieved by exploiting the asymmetric Doppler shift in moving atomic Bragg mirrors [20], and proofof-principle experiments have been carried out [21].The great interest in PT-symmetric complex media stemmed, however, from the non-Hermitian extensions of quantum mechanics and quantum field theories [22,23], and it is perhaps worth going back to the essential nonHermitian behavior of light transport to get a broader picture on reciprocity violations and unidirectional reflectionlessness. Take, e.g., a typical one-dimensional (1D) light scattering process as shown in Fig. 1(a) where the outgoing field amplitudes fE − L ; E þ R g are related to the incoming field amplitudes fE − R ; E þ L g by a scattering matrix S [24], the eigenvectors of which are defined byThe complex amplitudes t, r L , and r R of the (S) matrix in Eq.(1) denote, as usual, the reciprocal transmission and the reflection for incidence from the left and from the right. In general, the matrix S is non-Hermitian, its eigenvalues λ AE s ¼ t AE ffiffiffiffiffiffiffiffiffi ffi r L r R p are complex, and its eigenvectors ðAE ffiffiffiffiff...

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Non-Hermitian Degeneracies and Unidirectional Reflectionless Atomic Lattices

2014

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“…At variance with standard solid photonic crystal structures, atomic photonic crystal setups [32,33,[38][39][40][41] enable alloptical control of variant disorders [29,69,70]. Here we have addressed the issue of how robust are URL and CPA against uncorrelated and self-correlated disorders of familiar structural and geometric parameters, in a realistic photonic crystal structure obtained by driving cold atoms in an optical lattice to a multilevel EIT configuration [30][31][32][33][35][36][37][38][39][40][41][42].…”

Section: Discussionmentioning

confidence: 99%

“…Here we have addressed the issue of how robust are URL and CPA against uncorrelated and self-correlated disorders of familiar structural and geometric parameters, in a realistic photonic crystal structure obtained by driving cold atoms in an optical lattice to a multilevel EIT configuration [30][31][32][33][35][36][37][38][39][40][41][42]. We find that both URL and CPA are generally robust against structural disorder, though they appear rather sensitive against geometric disorder, mainly due to a concomitant variation in the phase mismatch between the cold-atomic density distributions and the dressing field spatial profiles.…”

Section: Discussionmentioning

confidence: 99%

“…Thus it is essential to assess how robust these two phenomena are in the presence of variant types of disorder. Exploiting the fact that coherently driven multilevel atoms have the uncommon advantages of real-time all-optical tunable and reconfigurable capabilities [23][24][25][26][27][28][29], we focus here on a realistic atomic photonic crystal structure [30][31][32][33][34][35][36][37][38][39][40][41][42] where the effect of disorder on URL and CPA phenomena could be simultaneously assessed.…”

Section: Introductionmentioning

confidence: 99%

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Perfect absorption and no reflection in disordered photonic crystals

Artoni

Rocca

2017

Phys. Rev. A

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Understanding the effects of disorder on the light propagation in photonic devices is of major importance from both fundamental and applied points of view. Unidirectional reflectionless and coherent perfect absorption of optical signals are unusual yet fascinating phenomena that have recently sparked an extensive research effort in photonics. These two phenomena, which arise from topological deformations of the scattering matrix S parameters space, behave differently in the presence of different types of disorder, as we show here for a lossy photonic crystal prototype with a parity-time antisymmetric susceptibility or a more general non-Hermitian one.

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“…Driven atomic lattices have aroused great interest of research for achieving controlled photonic band gaps, radiation damping enhancement, and two-color lasing oscillation [31][32][33][34]. Here we assume that all trapped atoms-the density modulation of which is dominated by a cosine term-are driven into the four-level N configuration with a far-detuned dressing field applied to induce the dynamic shift of one empty ground level.…”

Section: Introductionmentioning

confidence: 99%

Parity-time-antisymmetric atomic lattices without gain

Artoni

Rocca

2015

Phys. Rev. A

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Lossy atomic photonic crystals can be suitably tailored so that the real and imaginary parts of the susceptibility are, respectively, an odd and an even function of position. Such a parity-time (P T ) space antisymmetry in the susceptibility requires neither optical gain nor negative refraction, but is rather attained by a combined control of the spatial modulation of both the atomic density and their dynamic level shift. These passive photonic crystals made of dressed atoms are characterized by a tunable unidirectional reflectionlessness accompanied by an appreciable degree of transmission. Interestingly, such peculiar properties are associated with non-Hermitian degeneracies of the crystal scattering matrix, which can then be directly observed through reflectivity measurements via a straightforward phase modulation of the atomic dynamic level shift and even off resonance.

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Two-color lasing in cold atoms

Cited by 11 publications

References 66 publications

Non-Hermitian Degeneracies and Unidirectional Reflectionless Atomic Lattices

Non-Hermitian Degeneracies and Unidirectional Reflectionless Atomic Lattices

Perfect absorption and no reflection in disordered photonic crystals

Parity-time-antisymmetric atomic lattices without gain

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