Slow optical solitons via intersubband transitions in a semiconductor quantum well

We show the formation of bright and dark slow optical solitons based on intersubband transitions in a semiconductor quantum well (SQW). Using the coupled Schrodinger-Maxwell approach, we provide both analytical and numerical results. Such a nonlinear optical process may be used for the control technology of optical delay lines and optical buffers in the SQW solid-state system. With appropriate parameters, we also show the generation of a large cross-phase modulation (XPM). Since the the intersubband energy level can be easily tuned by an external bias voltage, the present investigation may open the possibility for electrically controlled phase modulator in the solid-state system

Constraining f(R) gravity in solar system, cosmology and binary pulsar systems

The $f(R)$ gravity can be cast into the form of a scalar-tensor theory, and scalar degree of freedom can be suppressed in high-density regions by the chameleon mechanism. In this article, for the general $f(R)$ gravity, using a scalar-tensor representation with the chameleon mechanism, we calculate the parameterized post-Newtonian parameters $\gamma$ and $\beta$, the effective gravitational constant $G_{\rm eff}$, and the effective cosmological constant $\Lambda_{\rm eff}$. In addition, for the general $f(R)$ gravity, we also calculate the rate of orbital period decay of the binary system due to gravitational radiation. Then we apply these results to specific $f(R)$ models (Hu-Sawicki model, Tsujikawa model and Starobinsky model) and derive the constraints on the model parameters by combining the observations in solar system, cosmological scales and the binary systems.Comment: LaTex, 19 pages,1 figure, typo corrected. To appear in Physics Letters