P. Saari

Picosecond time- and space-domain holography by photochemical hole burning

We demonstrate persistent storage, recall, and conjugation of picosecond light signals from various model objects, including a coin, by making use of coherent optical responses in photochemically active media. A simple linear theory of holographic storage and playback of both the spatial and the temporal behavior of the signal field is shown to describe well the experimental results obtained by utilizing octaethylporphin-doped polystyrene at 1.8 K as a spectrally selective recording material.

Photochemical time-domain holography of weak picosecond pulses

Abstract We show that weak picosecond optical pulse propagation through an absorbing medium with a photochemically burnedin persistent spectral hologram of a picosecond pulse train makes the sample emit coherently a replica of the pulse train applied in the burning-in cycle.

Elimination of excess pulse broadening at high spectral resolution of picosecond duration light emission

Abstract Monochromator pulse response broadening, far exceeding its uncertainty-principle-determined limit, arises from residual aberrations always existing in a real spectrometer. This serious handicap in high-resolution spectrochronography is shown to be overcome by the use of subtractive dispersion. In an experimental verification of the solution proposed, for the first time transform-limited temporal response has been achieved for a Raman-quality spectrometer.

Optical pulse shaping by filters based on spectral hole burning

Abstract A possibility of shaping the temporal profiles of picosecond light pulses by filtration through photochemically-burned spectral holes is demonstrated experimentally. The output pulse profiles calculated via the Fourier and Hilbert transformations from transparency spectra coincide with the ones measured directly.

Temporally multiplexed Fourier holography and pattern recognition of femtosecond-duration images

Abstract Image frames of femtosecond duration have been recorded and successively played back by (1 + 2)-dimensional Fourier holograms in a spectral hole burning medium. The duration and timing of frames are encoded into modulation of the distribution of dye molecules over their absorption frequencies, while images are encoded (in 2-D spatial-frequency representation) into modulation of dye density over the hologram plate. It is shown that separately recorded frames are recalled successively by the read-out pulse. Streak-camera measurements on model signals ascertain that despite the circumstance that molecules of the same absorption frequency and spatial location carry simultaneously information about the different frames recorded, there is no crosstalk between the frames, i.e. they are distinctly separated in time in accordance with values of delays set relative to the reference pulse in the recording procedure. A possibility to perform pattern recognition by a single hologram plate containing two 2-D filters matched to different text fragments on a microfilm slide, is demonstrated.

Storage and reproduction of an ultrafast optical signal with arbitrarily time dependent wavefront and polarization

Abstract Making use of photochemically accumulated stimulated photon echo the storage and reconstruction of time- and space-domain variations of light fields with arbitrarily variable polarization states and their full phase conjugation were accomplished.

Interference of accumulated stimulated photon echoes and storage of temporal segments in time-and-space-domain holography

Abstract Controlled picosecond time-domain interference of photochemically accumulated stimulated photon echoes excited by different laser pulses have been analyzed theoretically and observed experimentally in octhaethylporphin-doped polystyrene at 2 K. The method of segmentwise storage and reconstruction of light signals in a selected time interval have also been demonstrated and some other potential applications for optical information processing have been discussed.

Pico- and femtosecond photon echoes in doped low-temperature organic polymers and applications in time-space optical data processing

Abstract The phenomenon of burning of persistent photochemical holes in inhomogeneously broadened spectra of molecular impurities allows doped low-temperature organic polymers to be used as a recording medium of spectrally selective holograms. Ultimate temporal resolution of time domain holographic storage, Fourier-related to the inhomogeneous band width of the storage media was investigated by using femtosecond pulses generated by a colliding pulse mode locked dye laser. Recall of photochemically accumulated stimulated photon echo (PASPE) with pulse duration shorter than 100 fs was demonstrated in polystyrene doped with protoporphyrine at 1.8 K. Experiments presenting evidence of spectral diffusion in low temperature polystyrene as probed by PASPE and two-pulse photon echo are also reported.

Picosecond Time- And Space-Domain Holography By Photochemical Hole Burning

In this paper, the concept of holographic storage and reproduction of optical signals is generalized for the case of a spectrally highly selective recording medium, which in addition to fixing the spatial intensity distribution of the incident light is also able to memorize its intensity spectrum. We demonstrate persistent storage, recall and conjugation of picosecond light signals from various model objects by making use of coherent optical responses in photochemically active media. A simple linear theory of holographic storage and playback of both the spatial and the temporal behaviour of the signal is shown to well describe the experimental results obtained by utilizing octaethylporphin-doped polystyrene at 1.8 K as a spectrally selective recording material. The proposed method of time- and space-domain holographic recording provides the storage and reproduction of time-dependent optical signals with a duration of 10-8 to 10-13 sec. This presents unique possibilities for ultrahigh-speed data-storage and optical signal-processing.

Frequency-selective time-domain data storage and processing by the interference of stimulated photon echoes

Controlled picosecond time-domain interference of photochemically accumulated stimulated photon echoes excited by different laser pulses have been analyzed theoretically and observed experimentally in octhaethylporphin-doped polystyrene at 2K. The methods of segment wise storage and reconstruction of light signals in a selected time interval and performing operations of addition and subtraction have also been demonstrated. Potential applications of observed time-domain interference of different type coherent responses in spectral hole-burning media have been discussed