Abstract : The optical properties of four Tm(3+) ion - organic ligand chelate complexes in a poly(methyl methacrylate) matrix were studied. These materials are interesting for potential applications of optical hole-burning frequency and time-domain storage and processing. Optical absorption, steady state and time-resolved photoluminescence, and spectral hole-burning at the transition between 3-H6 (1) and 3-H4 (1) crystal-field levels were studied at temperatures between 1.4 and 300 K. The heterodyne grating-generated scan interferometric technique has been demonstrated for the real time detection of the femtosecond data signal.
Abstract : The optical properties of four Tm(3+) ion - organic ligand chelate complexes in a poly(methyl methacrylate) matrix were studied. These materials are interesting for potential applications of optical hole-burning frequency and time-domain storage and processing. Optical absorption, steady state and time-resolved photoluminescence, and spectral hole-burning at the transition between 3-H6 (1) and 3-H4 (1) crystal-field levels were studied at temperatures between 1.4 and 300 K. The heterodyne grating-generated scan interferometric technique has been demonstrated for the real time detection of the femtosecond data signal.
The optical properties of four Tm3+ chelates, specifically (beta) -diketone tris chelates of thulium, in a poly(methyl methacrylate) matrix are presented. Samples under investigation were the Tm3+ complexes formed using thulium chloride (TmCl3 (DOT) 6H2O) with thenoyltrifluoroacetylacetone (TTFA), 1,1,1-trifluoro-2,4- pentanedione (TFD), 1-phenyl-1,3-butanedione (PBD), and 1,3- diphenyl-1,3-propanedione (DBM) ligands. These materials are interesting from the point of view of potential applications for optical hole-burning frequency and time-domain storage and processing. Optical absorption, steady state and time-resolved photoluminescence, and spectral hole-burning at the transition between 3H6(1) and 3H4(1) crystal-field levels were studied at temperatures between 1.4 and 300 K.
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.
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.
Persistent spectral hole-burning and photon echoes can provide insight into the dynamics of amorphous and crystalline materials on the molecular/atomic level. Part of the current interest in these methods, however, is also caused by the existence of potential applications in optical data storage and processing. At present it may be difficult to specify exactly at what applications these techniques should try to target but, based on current research efforts and results, it appears that persistent spectral hole burning is a possible candidate for high density, possibly long time, volumetric storage, while photon echoes have properties more attractive for short time storage or storage connected to processing applications.
Spectral hole burning and photon echoes are the techniques for frequency-selective optical memories, which have the potential to increase areal data storage density by a factor 10**7. They also have the capability to perform in-memory data processing. In this thesis, several materials and techniques for optical memories in the frequency- and time domain have been investigated. In the frequency domain, ways to increase the storage density and the working temperature were studied using photon-gated spectral hole burning materials of the metal-tetrabenzoporphyrin derivatives. A selection rule for the electron acceptors in the donor-acceptor electron transfer systems was deduced. By doping the material with two different donors a maximum inhomogeneous line width of more than 30 THz was achieved. A polarization holographic technique was established for the formation and detection of spectral holes. Our results indicate that this technique can provide a better signal-to-noise ratio than that achieved by a conventional holographic technique, in particular for samples of poor optical quality. In the time domain, magnetic field-induced and the intensity-induced dephasing processes were studied in Pr3+ doped in a YAlO3 crystal and a Y2SiO5 crystal, respectively. As a step along the route to make photon echo based optical processing possible, the amplification of photon echo signals by the use of a fiber amplifier (Pr3+-doped ZBLAN) was demonstrated. A gain of 45 was achieved. The erasure of stored data using photon echoes has also been investigated. A technique to diagnose the phase and frequency stability of a light source by the photon echo erasure process was proposed and illustrated. An approach to bit-selective data erasure, that is free from laser phase and frequency fluctuations, is also suggested. A concept for an arbitrary shape pulse generator based on photon echoes and hole-burning was experimentally and theoretically studied. Finally, a comparison between the properties and capabilities of spectral hole burning and photon echoes was made.
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.