M. Selim Shahriar

Two-dimensional holographic nonspatial filtering for laser beams

In this paper, we discuss our most recent work in 2D nonspatial filtering. A brief introduction describes nonspatial filtering and its relationship to conventional spatial filtering. We then show result from our initial experiments in 2D nonspatial filtering and briefly describe a more advanced design. A variation on the more advanced design demonstrates wavelength-independent operation. We then review our initial findings on adhesives appropriate for implementation of the advanced design and comment on the surface quality requirements of the recording material, a polymer with diffusion amplification. Finally, we compare the robustness and efficiency of nonspatial filters with conventional spatial filters.

Two-dimensional holographic nonspatial filters

Holographic nonspatial filters designed to clean up the output of a laser have been shown to be a great improvement over conventional spatial filters. This paper successfully addresses several major problems or shortcomings of the nonspatial filter. The problems were in the use of two filters together for cleaning up a laser beam in both dimensions. Polarization and orientation effects made the system complicated an inconvenient. A simple compound element consisting of a sandwich of two identical holograms is shown to solve these problems.

Multi-Spectral Raman Gain in Atomic Rubidium Vapor

Optically off-resonant stimulated Raman scattering of 85-Rb is studied experimentally to implement a scheme that eliminates the key sources of fidelity loss in macroscopic entanglement and quantum information storage using atomic vapor or trapped atoms.

Demonstration of a Multiwave Coherent Holographic Beam Combiner in a Polymeric Substrate

We demonstrate an efficient coherent holographic beam combiner using angle multiplexing of gratings. Our experimental results compare well with the theoretical model based on the coupled wave theory of multi-wave mixing in a passive medium.

Efficient generation of Raman echo and time-domain optical data storage by electromagnetically induced transparency

We have observed excitation of spin echoes and spin free induction decay (FID) by electromagnetically induced transparency (EIT) in an optically dense solid sample. The experiments are done in a double-lambda system of 605.7 nm 3H4 - 1D2 transition of Pr3+:Y2SiO5, where the 10.2 MHz ground state spin coherence is excited by low-power resonant Raman pulses. It has been shown that the spin coherence, including spin echo, is equivalent to the transparent state of EIT, and therefore a high efficiency is expected for such resonant Raman-excited spin echo. The observed efficiency of spin echo is as high as 75% of the FID signal at 5K. A background-free detection scheme is used based on EIT and enhanced nondegenerate four-wave mixing. The technique is applied in the frequency-selective time-domain optical data storage, that utilizes the spin as well as the optical inhomogeneous spectral widths. The data storage scheme is analogous to the stimulated spin echo with resonant Raman excitation of the spin coherence. We verify that the write window is determined by the spin T2 which is much longer than the optical T2, especially at higher temperature. We find that the spin dephasing time T2 is almost constant at approximately 500 microseconds in the range of 2 to approximately 6 K, whereas the optical T2 decreases rapidly, by a factor of approximately 50, above 4 K. These results will be useful in the development of high capacity time-domain optical data storage operating at higher temperature.