Field Propagation in Atomic Media

Javier Rivera-Dean, Deeksha Kanti, Philipp Stammer +5 more

Recent developments in quantum light engineering have enabled the use of infrared bright squeezed vacuum (BSV) femtosecond pulses in nonlinear optics, including strong-field physics and high-harmonic generation. However, theory has focused on single-atom interactions, neglecting the crucial macroscopic aspect of light propagation through media. This raises a key question: How does BSV propagate in nonlinear media, and how this affects the nonlinear signals and the radiation’s quantumness? We address this with a fully quantized framework for propagation in gas media undergoing high-harmonic generation. We find that ionization and the associated photon losses cause decoherence, which limits the propagation length, degrades radiation’s quantumness, and reduces the emitted harmonics. However, these effects are not detrimental. We identify conditions that minimize propagation-induced decoherence while preserving detectable harmonics with super-Poissonian photon statistics. Our results establish fully quantized basis for exploring BSV in nonlinear optics, strong-field-quantum optics, and ultrafast science in all states of matter. Recent developments in strong-field quantum optics are usually modelled with approaches neglecting the propagation dynamics inside the medium. Here, the authors introduce a fully quantized framework for bright squeezed vacuum states propagating inside atomic media undergoing high-harmonic generation, unveiling the role of decoherence effects.

Igor I Sobel'man

B Ya Dubetskiĭ, A. P. Kazantsev, V. P. Chebotaev +1 more

C. M. Bowden, R. Inguva, Aharon Postan

Analytical solutions for the slowly varying phase as well as the field amplitude are obtained for invariant pulse propagation in resonant absorbing media consisting of interacting two-level atoms. Such media, having many atoms within a cubic wavelength, have been shown to exhibit large frequency chirps in pulse propagation owing to near-dipole–dipole interactions. Departures from hyperbolic-secant pulse envelopes and pulse areas other than 2π have been shown to occur in invariant pulse propagation. We show that self-phase modulation results from the near-dipole–dipole interactions and can cause strong modification of pulse shapes, including temporal narrowing and multipulse behavior.

Robert S. Afzal, W. P. Lin, N. M. Lawandy

Nonlinear beam propagation in absorbing media was originally examined by numerical simulations of the propagation of an electric field interacting with homogeneously broadened two-level atoms.1,2 Two significant predictions of the theory were cw on-resonance enhancement (CORE) and Fresnel ring encoding on the propagating beam. CORE has been observed in sodium vapor experiments3 where the center intensity of a beam traveling through an absorbing media increased by 69%. Fresnel ring encoding of an Ar-ion laser beam propagating through a sample of pink ruby has also been demonstrated.4 We further the work by discussing the experimental study of the effect of an absorbing birefringent media on a propagating laser beam.