Selim M. Shahriar

Very thick holographic nonspatial filtering of laser beams

Philip Hemmer, MEMBER SPIE Rome Laboratory RL/EROP, 63 Scott Road Hanscom Air Force Base, Massachusetts 01731 Abstract. A novel device, the nonspatial filter, is described for laser beam cleanup. It is based on the Bragg selectivity of thick holograms. Unlike pinhole and fiber spatial filters, which employ lenses and apertures in the transform plane, nonspatial filters operate directly on the laser beam. This eliminates the need for laser beam focusing, which is the source of many of the material and alignment instabilities and laser power limitations of spatial filters. Standard holographic materials are not suitable for this application because differential shrinkage during processing limits the maximum Bragg angle selectivity attainable, and because they are generally too thin. New technologies that eliminate the problem of differential shrinkage are described. These technologies are based either on the use of a rigid porous substrate material, such as porous glass, filled with a light-sensitive material, such as holographic photopolymers or dichromated gelatin, or on the use of a thick photopolymer with diffusion amplification (PDA). We report results of holographic nonspatial filtering of a laser beam in one dimension, with an angular selectivity of better than 1 mrad.

Electromagnetically induced transparency over spectral hole-burning temperature in a rare-earth–doped solid

We have observed electromagnetically induced transparency (EIT) in rare-earth Pr3+-doped Y2SiO5 over the spectral hole-burning temperature. The transmission of the probe laser beam is increased by a factor of exp(1.4) at 12 K when a coupling laser of 1.2 kW/cm2 is applied to the system. The observation of EIT over the spectral hole-burning temperature in a rare-earth–doped solid represents important progress toward high-density echo-based optical memories at higher temperatures.

Holographic Optical Memories

The potential applications of Bragg-selective holographic optical memories have been discussed. In particular, important applications were identified that rely on the unique properties of these memories, namely, their combined high storage density and capability for massively parallel input/output. These include image identification based on massively parallel optical correlations, which has application to military target recognition and commercial robotic vision, and high-density page-oriented storage, which has applications to secure databases and satellite information storage. To make the discussions of these applications concrete, we included details of our planned Bragg- selective holographic memory demonstration unit.

Front Matter: Volume 6904

This PDF file contains the front matter associated with SPIE Proceedings Volume 6904, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Raman excited spin coherences in N-V diamond

Summary form only given. The use of optical Raman interactions to excite spin coherences in solids has numerous potential applications, ranging from low-power nonlinear optics to high-temperature spectral hole burning memories to solid-state quantum computing. The interest in Raman excitation lies in the fact that the spin coherences can be efficiently excited and manipulated using optical laser fields yet are weakly coupled to the environment and hence have the long coherence lifetimes needed for optical memories and quantum computing. The interest in nitrogen-vacancy (N-V) color centers in diamond is its large optical oscillator strength. For memory, a large oscillator strength is important for high temperature operation. For quantum computing, the high optical transition rate enables the higher gate speed and the larger number of quantum logic operations that can be performed within the spin coherence lifetime.

Electromagnetically induced transparency over spectral hole-burning temperature in an inhomogeneously broadened solid

Summary form only given. When a resonant Raman laser field interacts with a three-level energy system, the system can undergo changes of linear and nonlinear optical properties. Especially in an optically thick medium, a strong resonant electromagnetic field can dress the energy states so that another resonant probe field may not be absorbed. This is due to destructive quantum interference between two absorption paths from the ground state to the dressed states. This phenomenon is called electromagnetically induced transparency. Our recently demonstrated Raman excited spin echo technique uses optically induced spin coherence. In general, the spin coherence decay time is much longer and more temperature insensitive than the optical coherence, so that the temperature limitation of the photon echoes can be overcome. The spin echoes are read by another optical field via enhanced four-wave mixing. Here, the nonlinearity in the optical transition is enhanced by EIT. In this paper we report the EIT observation at temperatures higher than that needed for the (optical) spectral hole-burning.

Efficient phase conjugation using Raman dark resonances in an optically dense crystal

Summary form only given. In a three-level system, optical refractive indices can be changed due to the atom-field interactions. Especially in a short time scale (t/spl Lt/ /spl gamma/), a resonant strong electromagnetic field can change the absorption coefficient strongly so that another resonant electromagnetic field which has a different frequency can pass through without experiencing any absorption in an optically dense medium. This phenomenon is called electromagnetically induced transparency (EIT). There have been many studies of EIT in atomic vapors and solids for potential applications to nonlinear optical processes such as enhanced four-wave mixing, lasers without inversion, frequency up-conversion lasers, and optical memory. We report efficient phase conjugation based on EIT in an in homogeneously broadened solid system of Pr/sup 3+/ doped yttrium silicate.