| All-optical modulation and switching are important for optical communication and quantum information processing. Conventional techniques of non-linear optics typically require relatively high power, and are not well suited for these applications. Using a tapered nano fiber (TNF) embedded in Rb vapor we developed a modulator at few nW of power. Design and experimental issues related to the fabrication and deployment of TNF are discussed. High-speed operation in another requirement of all-optical networks. It is well-known that the presence of buffer gas (such as Helium or Ethane) in atomic vapor causes rapid spin-relaxation between the J=3/2 and J=1/2 states and increased absorption cross-section. In this work, we employ cascade transitions in Rubidium to take advantage of this to develop high-speed all-optical modulators. Under similar conditions, a 100-fold increase in the bandwidth was observed with the possibility of increasing it further by using a higher optical field strength. Combined with the TNF technology, it can used for ultra-low power, high-speed all-optical modulators.;Polarimetric or Stokesmetric Imaging (SI) technique allows us to distinguish objects with similar reflectivity but different polarimetric features. A conventional SI system consists of a quarter wave plate (QWP) and a linear polarizer (LP), periodically removed and oriented at different angles. Consequently, the speed of the system is greatly limited, which hinders it from being integrated into a real-time system. In this work, we investigated the suitability of cascade transitions in Rubidium for developing optically controlled waveplates and polarizers, which would be capable of functioning at speeds up to a few MHz, for use in a high-speed SI system. These effects are based on selection rules and quantum interference phenomenon between various Zeeman sub-levels in Rb. Both theoretical and experimental results are presented.;Finally, we also developed a novel algorithm for the numerical evaluation of the steady-state solution and the time-dependent evolution of an arbitrarily large quantum system, where symbolic computations may be too slow or memory intensive and consequently, impractical. Use of parallel computing techniques to implement this algorithm enabled extremely efficient and high-speed computation. The algorithm was extensively employed in simulations of the systems investigated in this work. |
