Over the report period, an optical laboratory for characterization materials for frequency domain optical storage was upgraded. Spectral and spectral hole burning properties were studied for several free-based and metallo-naphthalocyanine derivatives in polymer hosts. These materials exhibit a strong 0-0 absorption band and persistent hole burning in the region 800 nm. Hole burning parameters were determined for eight materials; in particular, the hole burning kinetics was analyzed and the quantum efficiencies were determined to be between 0.1% and 1%. Holograms (data pages) in the transmission geometry were successfully recorded in the materials studied using single frequency laser diodes. A photoluminescence of five natural diamonds (type Ia) implanted with Xe ions with dose range 1x10(exp 13) - 5x10(exp 14) /sq cm was investigated as a function of thermal annealing at temperatures between 300 and 1400 C.
Over the report period, an optical laboratory for characterization materials for frequency domain optical storage was upgraded. Spectral and spectral hole burning properties were studied for several free-based and metallo-naphthalocyanine derivatives in polymer hosts. These materials exhibit a strong 0-0 absorption band and persistent hole burning in the region 800 nm. Hole burning parameters were determined for eight materials; in particular, the hole burning kinetics was analyzed and the quantum efficiencies were determined to be between 0.1% and 1%. Holograms (data pages) in the transmission geometry were successfully recorded in the materials studied using single frequency laser diodes. A photoluminescence of five natural diamonds (type Ia) implanted with Xe ions with dose range 1x10(exp 13) - 5x10(exp 14) /sq cm was investigated as a function of thermal annealing at temperatures between 300 and 1400 C.
Abstract : Optical materials for spectral hole burning and coherent transient applications were designed and evaluated, emphasizing relevance to devices including high performance memory, signal processing, high speed holographic recording and analysis, and optical switches, routers, and buffers. The ultimate limits on material performance set by atomic mechanisms were determined. The developed materials contained Eu3+, Pr3+, Tm3+, Tb3+, or Er3+ active ions in various oxide hosts. The first report was made of an Er3+ material for hole burning applications in 1.5 micron optical communications bands. Eight Er3+ materials for applications at 1.5 microns in optical routers and buffer memories were designed and characterized. A correlator' signal processing capability was demonstrated, and the first report was made of operation of a 1.5 micron packet header decoder for all-optimized optical packet switching in optical communications along optical fibers at 1531 nm. Eu3+:Y2SiO5 was optimized for use in 100 GByte ODRAM optical memory devices, considering Eu3+ concentration and temperature. Eight Tm3+ compounds for signal processing applications, such as true time delays for phased-array radar, at diode laser wavelengths near 795 nm were designed and characterized. Eight Tb3+ compounds for photon gated spectral hole burning were designed and characterized, and gated hole burning was observed in Tb3+:YAIO3.
To determine the complete set of required materials properties for a viable frequency-domain optical-storage system based on persistent spectral hole burning, we have performed analytic and computer simulations of the writing performance, signal-to-noise ratio, and number of reads that can be obtained from single-photon or monophotonic (no threshold) hole-burning mechanisms with realistic spot sizes and reading and writing times. We find that acceptable reading performance occurs only for materials with high quantum efficiencies, low absorption cross sections, and high solubilities. This work for the first time clearly defines the parameter space of single-photon materials that can be utilized in a frequency-domain optical-storage system.
The persistent spectral hole-burning (PSHB) phenomenon has been known since 1974. It is still an important research area for the study of the intimacy of complex molecular systems in the solid state, revealing high-resolution spectra, photophysics, photochemistry, and dynamics of molecular doped amorphous media, organic as well as inorganic. From another point of view, PSHB allows the engraving of any spectral structures in the inhomogeneous absorption band profile of molecular doped amorphous hosts or ion doped crystals cooled down to liquid helium temperatures. Therefore, a PSHB material is programmable in the spectral domain and consequently it can be transformed in an optical processor capable of achieving user-defined optical functions. Some aspects of both fields are illustrated in the present paper. Concerning the search for efficient PSHB materials, the hole-burning performances and the photophysics of polymer and xerogel based systems are compared. The problem of high-temperature persistent spectral hole-burning materials and the search for new frequency selective photosensitive systems for fast optical pulse processing at 800nm are considered. Regarding the points treated, inorganic hosts based on silicate xerogels or porous glasses have shown the best results. Moreover, by combining inorganic and organic capabilities or by grafting organic species to the host, hybrid xerogels have not yet revealed all possibilities. Also, the interest of two-photon materials for engraving spectral features with near-infrared or infrared light is developed. As an introduction to possible applications of PSHB material, the basics of spectro-temporal holography are remembered and a demonstrative experiment using a naphthalocyanine-doped polymer film is described, proving that the temporal aberration free recompression of ultrashort light pulses is feasible, therefore opening a way for applications in ultrashort light pulse shaping. Aspects for a comparison between cw hole-burning and femtosecond spectro-temporal experiments are considered, and prospects for coherent control of light fields or photochemical processes are also evoked.
Persistent spectral hole-burning (PHB) is a phenomenon that allows an additional dimension, the frequency at which spectral holes are written, to be used to encode digital data. PHB can be used to store a large number of bits of information in the volume irradiated by a focused laser beam, leading to a possible future storage technology, frequency domain optical storage. A large number of photochemical and photophysical mechanisms have led to the production of spectral holes; a wealth of information has been learned about host-guest interactions, dephasing, and solid-state photochemistry at low temperatures. The general structure of a frequency domain optical store places a set of constraints on the engineering of such a system as well as on the materials used as recording media. The dynamics of the hole-burning process are crucial; for monophotonic mechanisms in particular, a set of stringent constraints can be derived that limit the applicability of this class of materials. Recent discoveries of two-color, photon-gated hole-burning offer special promise for nondestructive reading and improved performance.
Persistent spectral hole-burning (PHB, also called photochemical hole-burning) permits use of the optical frequency for encoding digital information through the presence and absence of spectral holes that are burned in inhomogeneously broadened absorption lines at low (liquid helium) temperatures. The optical frequency or wavelength at which a given hole is burned acts as an additional dimension for data storage, hence this optical recording scheme has been called Frequency Domain Optical Storage (FDOS). The combination of spectral and spatial data-recording can make storage densities in excess of 1010 bits/cm2 possible; furthermore, since rotation of the recording medium is not necessary, shorter random access times will result. The future success of the FDOS concept will rely on progress in several technological and engineering areas as well as on advances in several critical materials areas1.
Persistent spectral hole burning (PSHB) in organic molecules doped in a polymer matrix at low temperatures allows optical recording of information in the dimensions of frequency and time, as well as in space and externally applied electric field. We use this special property to demonstrate new types of holograms, which extend conventional spatial-domain optical data storage into the new dimensions. Basic aspects of recording and playback of holograms by persistent spectral hole burning, including relation between frequency- and time-domain response function, is discussed. This paper is elucidating inherent relations between the time- and frequency-domain versions of PSHB holography. We show that by multiplexing holograms in the frequency dimension, we can store a large number (up to 12 000) of image holograms using a single spectral hole burning sample. In the time domain, we show storage and reproduction of ultrashort time-space images on the scale of 10 -12 −10 -13 s. Experiments demonstrating unusual hologram properties, such as causality-related asymmetry of diffraction, inversion of time coordinate, and ultrafast processing, are presented.