Signature of strong atom-cavity interaction on critical coupling

We study a critically coupled cavity doped with resonant atoms with metamaterial slabs as mirrors. We show how resonant atom-cavity interaction can lead to a splitting of the critical coupling dip. The results are explained in terms of the frequency and lifetime splitting of the coupled system.Comment: 8 pages, 5 figure

Phosphodiesterase-4 Inhibition Alters Gene Expression and Improves Isoniazid – Mediated Clearance of Mycobacterium tuberculosis in Rabbit Lungs

Tuberculosis (TB) treatment is hampered by the long duration of antibiotic therapy required to achieve cure. This indolent response has been partly attributed to the ability of subpopulations of less metabolically active Mycobacterium tuberculosis (Mtb) to withstand killing by current anti-TB drugs. We have used immune modulation with a phosphodiesterase-4 (PDE4) inhibitor, CC-3052, that reduces tumor necrosis factor alpha (TNF-α) production by increasing intracellular cAMP in macrophages, to examine the crosstalk between host and pathogen in rabbits with pulmonary TB during treatment with isoniazid (INH). Based on DNA microarray, changes in host gene expression during CC-3052 treatment of Mtb infected rabbits support a link between PDE4 inhibition and specific down-regulation of the innate immune response. The overall pattern of host gene expression in the lungs of infected rabbits treated with CC-3052, compared to untreated rabbits, was similar to that described in vitro in resting Mtb infected macrophages, suggesting suboptimal macrophage activation. These alterations in host immunity were associated with corresponding down-regulation of a number of Mtb genes that have been associated with a metabolic shift towards dormancy. Moreover, treatment with CC-3052 and INH resulted in reduced expression of those genes associated with the bacterial response to INH. Importantly, CC-3052 treatment of infected rabbits was associated with reduced ability of Mtb to withstand INH killing, shown by improved bacillary clearance, from the lungs of co-treated animals compared to rabbits treated with INH alone. The results of our study suggest that changes in Mtb gene expression, in response to changes in the host immune response, can alter the responsiveness of the bacteria to antimicrobial agents. These findings provide a basis for exploring the potential use of adjunctive immune modulation with PDE4 inhibitors to enhance the efficacy of existing anti-TB treatment

The role of absorption and dispersion in resonant tunnelling through a negative index medium

We study resonant tunneling through a layered medium with a passive negative index medium (NIM) slab as a constituent layer. Using a causal model for susceptibilities with the parameters of a recently reported metamaterial [G. Dolling, C. Enkrich, M. Wegener, C.M. Soukoulis, S. Linden, Opt. Lett. 31, 1800 (2006)] we show that resonant tunnelling and the associated delay are mostly suppressed. This is in sharp contrast with the naive approach of retaining phase velocity dispersion with arbitrary low losses, predicting sharp resonances with large associated delays. This is shown to be a nontrivial issue because of the necessity of losses for NIM behaviour, while their presence spoils the quality factor of the resonant devices

Solitonlike structures and their self-similarity in nonlinear Fibonacci multilayered media

Switching from low to total transmission in a nonlinear Fibonacci multilayered medium is examined. It is found that this switching is due to the formation of solitonlike structures characterized by a sech2 intensity distribution, which results from a delicate interplay between dispersion and nonlinearity in the medium. These are shown to possess the remarkable properties of scaling and self-similarity

Localization problem in optics: nonlinear quasiperiodic media

We have presented a detailed numerical study of the localization problem in a nonlinear quasiperiodic structure for normal incidence of plane-polarized light. The main conclusions are as follows. Strong surface localization, which is observed for forbidden states (transmission coefficient T≃0) in the linear theory, is strongly affected even by weak nonlinearity, resulting in inhibition of localization, while the extended states corresponding to allowed regions (T≃1) in the linear theory retain their distribution pattern. Depending on nonlinearity, forbidden regions may exhibit critical-state behavior. The evidence of bulk localization is apparent from the nature of solitonlike field distributions for allowed regions. The bulk localization, which is a result of a delicate interplay between dispersion and nonlinearity, persists for a very large number of layers in contrast to linear theory. The bulk localized states have been shown to be self-similar