Spectral hole burning (SHB) allows to extend conventional spatial-domain optical data storage and coherent processing into the dimensions of frequency and time. To achieve ultrafast performance, on the time scale of 10-12 - 10-13s, we use organic dye-doped polymer materials at liquid-helium temperature. These materials enable SHB recording and coherent transient responses with a broad optical band width of 5 - 10 THz. We discuss applications of organic SHB systems for associative recall of time-and-space domain events, spectral programming of pulse trains, Stark switching of holograms, THz-bit-rate multiplication, cross- spectral processing and photon gated recording of erasure resistant coherent transients.
Spectral hole burning (SHB) allows to extend conventional spatial-domain optical data storage and coherent processing into the dimensions of frequency and time. To achieve ultrafast performance, on the time scale of 10-12 - 10-13s, we use organic dye-doped polymer materials at liquid-helium temperature. These materials enable SHB recording and coherent transient responses with a broad optical band width of 5 - 10 THz. We discuss applications of organic SHB systems for associative recall of time-and-space domain events, spectral programming of pulse trains, Stark switching of holograms, THz-bit-rate multiplication, cross- spectral processing and photon gated recording of erasure resistant coherent transients.
Time-and-space-domain holography [1,2] can be regarded as an extension of a conventional holographic process, where, in addition to the spatial image, the hologram plays back the time dependence of an event. The play-back of events is possible because we are using highly frequency-selective inhomogeneously broadened absorbers as recording material. This technique has a variety of potential applications in optical data storage and processing. In the present paper we consider the basic physical principle of time-and-space-domain storage in frequency-selective materials which exploit the effect of spectral hole burning [3]. In particular we will show that organic dye-doped spectral hole burning materials allow recording and playback of pi- co- and femtosecond time-scale events.
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.
Summary form only given. Spectral hole burning (SHB) is a promising technique for optical recording of information with a potential to store in excess of 10/sup 4/-10/sup 5/ bits per /spl lambda//sup 3/ volume (Moerner, 1988). Highest storage capacity is achieved when frequency- or time-domain addressing is combined with addressing in three spatial dimensions by using a bulk SHB medium. However, so far both bit-by-bit and holographic SHB storage experiments were restricted to two spatial dimensions. This is because focusing a laser beam to a small volume inside the SHB medium is hindered by one-photon absorption in SHB material layers. We propose that this problem may be overcome by burning holes via two-photon absorption (TPA) (Demtro/spl uml/der, 1982; Takeda et al, 2000). TPA has been used earlier for conventional spectrally nonselective recording in photo-chromic materials by focusing two perpendicularly directed laser beams (with photon energies /spl planck//spl omega//sub 1/ and /spl planck//spl omega//sub 2/) on to one spot (Parthenopoulos and Rentzepis, Science, vol. 245, pp. 843-845, 1989). Since the sample is transparent for each beam separately, TPA occurs only at the beam intersection point. In this paper, we investigate frequency-selective SHB by TPA in organic dye-doped polymers at low temperature. In our experiments, the SHB medium is essentially transparent for the writing beams, which allows unrestricted penetration and focusing in the depth of the sample.
Summary form only given.Frequency-selective materials, based on spectral hole-burning allow recording holograms and interferograms of spectrally broad-band, temporally incoherent light signals. An important task for information technology as well as spectroscopic applications is simultaneous recording of the temporal, spectral, and spatial characteristics of ultrashort optical signals. Single-shot recording with a spectral hole-burning material will allow us to measure individual time-varying optical amplitudes without involving any temporal or spatial averaging, thus maintaining complete information about an optical signal. We have performed experiments on recording and playback of time- and space-domain holograms using single femtosecond pulses. We have studied the dependence of the hologram recording and playback on both the energy and the number of the applied pulses as well as on photon gating mechanism by an additional laser pulse at a different frequency.
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.
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.