One-dimensional Optical Superlattice Research Articles

Response of Bose gases in time-dependent optical superlattices

The dynamic response of ultracold Bose gases in one-dimensional optical lattices and superlattices is investigated based on exact numerical time evolutions in the framework of the Bose–Hubbard model. The system is excited by a temporal amplitude modulation of the lattice potential, as it was done in recent experiments. For regular lattice potentials, the dynamic signatures of the superfluid to Mott-insulator transition are studied and the position and the fine-structure of the resonances is explained by a linear response analysis. Using direct simulations and the perturbative analysis it is shown that in the presence of a two-colour superlattice the excitation spectrum changes significantly when going from the homogeneous Mott-insulator to the quasi-Bose-glass phase. A characteristic and experimentally accessible signature for the quasi-Bose-glass is the appearance of low-lying resonances and a suppression of the dominant resonance of the Mott-insulator phase.

Wide-band transmission of nondistorted slow waves in one-dimensional optical superlattices

Few micron-thick one-dimensional optical superlattices were designed and grown, in which an optimized choice of external dielectric layers allows the formation of a wide and high transmission miniband of coupled cavity states. In such structures a reduction in light group velocity and minimal line shape distortion of propagating optical signal was observed. Group velocity reduction by a factor of 5, obtained both from phase (white-light interferometry) and from time-resolved measurements, is in reasonably good agreement with those calculated through a transfer matrix approach. Time-resolved experiments confirm the minimal line shape distortion for optical pulses of 1.8THz bandwidth at λ=1.5μm wavelength.

Oscillations of Bose-Einstein condensates in a one-dimensional optical superlattice

Oscillations of atomic Bose-Einstein condensates in a 1D optical lattice with a two-point basis is investigated. In the low-frequency regime, four branches of modes are resolved, that correspond to the transverse in-phase and out-of-phase breathing modes, and the longitudinal acoustic and optical phonon modes of the condensates. Dispersions of these modes depend intimately on the values of two intersite Josephson tunneling strengths, $J_1$ and $J_2$, and the on-site repulsion $U$ between the atoms. Observation of these mode dispersions is thus a direct way to access them.

Emission and absorption spectra of dark optical superlattices

We calculate the spectrum of resonance fluorescence and the weak-field absorption spectrum obtained from atoms cooled and trapped in a one-dimensional dark optical superlattice, which is formed by a bichromatic laser field in double-Λ configuration. These spectra provide an experimentally accessible tool to gain important information about the trapping mechanism and the steady-state density matrix. A rate-equation approach is used to discuss the dependence of the spectra on various model parameters.

Optical Bistability in Incident-Dependent Two-Dimensional Nonlinear Optical Superlattices

It is shown that, when two coherent waves are obliquely incident to a one-dimensional nonlinear optical superlattice containing Kerr-form dielectric nonlinearity, an incident-dependent two-dimensional nonlinear optical superlattice can be constructed. This structure can be bistable. There exist two types of optical bistable mechanism, i.e., the index-modulation mechanism and distributed feedback mechanism. Owing to the index-modulation mechanism, the threshold for the bistability is lower than that of a more traditional one-dimensional distributed feedback structure.