[en] Initiation of superfluorescence in a medium consisting of three-level atoms is studied. Strong influence of the pump pulse evolution on the superfluorescence radiation is pointed out. The explicit formulas for the average superfluorescence intensity and the delay time are presented and their dependence on the length of the sample is discussed. (author)

No abstract available

[en] We show that, in their unstable regime of operation, the 'Maxwell-Bloch' equations that describe light-matter interactions inside a bad-cavity-configured laser carry the same resonance properties as any externally driven mechanic or electric oscillator. This finding demonstrates that the nonlinearly coupled laser equations belong to the same universal family of forced oscillatory systems. The primary difference is that while mechanical or electrical systems are put into resonance with an external sinusoidal force with constant amplitude, the resonance curve of the laser equations is described exclusively in terms of linear pump scans, for fixed cavity and material decay rates. In both cases, however, the damping factors play the same fundamental role

No abstract available

[en] It is well known that the Dirac equation on a discrete hyper-cubic lattice in D dimension has 2^D degenerate solutions. The usual method of removing these spurious solutions encounters difficulties with chiral symmetry when the lattice spacing l ≠ 0, as exemplified by the persistent problem of the pion mass. On the other hand, we recall that in any crystal in nature, all the electrons do move in a lattice and satisfy the Dirac equation; yet there is not a single physical result that has ever been entangled with a spurious fermion solution. Therefore it should not be difficult to eliminate these unphysical elements. On a discrete lattice, particle hop from point to point, whereas in a real crystal the lattice structure in embedded in a continuum and electrons move continuously from lattice cell to lattice cell. In a discrete system, the lattice functions are defined only on individual points (or links as in the case of gauge fields). However, in a crystal the electron state vector is represented by the Bloch wave functions which are continuous functions in rvec γ, and herein lies one of the essential differences

[en] Optical Sommerfeld-Brillouin precursors significantly ahead of a main field of comparable amplitude have been recently observed in an opaque medium with an electromagnetically induced transparency window [Wei et al., Phys. Rev. Lett. 103, 093602 (2009)]. We theoretically analyze in this article the somewhat similar results obtained when the transparency is induced by the propagating field itself and we establish an approximate analytic expression of the time delay of the main-field arrival, which fits fairly well the result obtained by numerically solving the Maxwell-Bloch equations.

[en] We present a complete analytic solution of the quasi-Bloch equations encountered in low gain Free Electron Laser Systems. (orig.)

[en] We show that polarization-gradient cooling occurs simultaneously with velocity selective coherent population trapping (VSCPT), when a folded three level (Λ) system is excited by a pair of standing waves with a phase difference of π/4. This process may continuously and efficiently transfer atoms from a Doppler temperature sample to near-recoil velocities capturable by VSCPT, which would then provide continuous cooling below the recoil limit. This pre-cooling should enhance the VSCPT pumping rate by nearly three orders of magnitude compared to the rate achievable from Doppler pre-cooling alone. We present a Sisyphus model, and find the results to be in resonable agreement with numerical solutions of the optical Bloch equations. We also discuss generalization to three dimensions

No abstract available

[en] Short communication