Application of the Photon Echo in a Gas Medium for Data Writing, Storage, and Processing

R Krishna Mohan, Ulf Elman, Ming Tian +2 more

Stefan Kröll, E. Y. Xu, Ravinder Kachru +1 more

Igor V. Yevseyev, Valery M. Yermachenko, Самарцев Виталий Владимирович

As it was emphasized several times above, the phenomenon of the photon echo is an optical analog of the spin echo that has been discovered [ 1 ] about a decade earlier. That is why many ideas from the theory of the spin echo has been transferred to the theory of the photon echo and appeared to be fruitful there. One of these ideas put forward by Fernbach and Proctor [ 2 ] is the idea of the possibility of the use of the phenomenon of the spin echo for writing, storage, and processing of the data. The authors [ 2 ] determined the conditions under which the signals of the spin and stimulated spin echo can reproduce (direct or time-reversed) shape of one of the exciting pulses. The theoretical analysis was proved by the corresponding experiments.

Masaharu Mitsunaga

Stefan Kröll, Per Tidlund

The first analysis to our knowledge of the optical data storage density of photon-echo storage is presented. Mainly considering signal-to-noise ratio performance, we calculate the obtainable storage density for data storage and processing using photon echoes to be approximately 100 times the theoretical limit for conventional optical data storage. This limit is similar to that theoretically calculated for data storage by use of persistent spectral hole burning. For storage times longer than the upper-state lifetime the highest densities can, however, be obtained only if all the excited atoms decay, or are transferred, to a different state than that from which they were originally excited. The analysis is restricted to samples with low optical density, and it also assumes that for every data sequence, writing is performed only once. It is therefore not directly applicable to accumulated photon echoes. A significant feature of photon-echo storage and processing is its speed; e.g., addressing 1 kbyte/(spatialpoint) permits terahertzread and write speeds for transitions with transition probabilities as low as 1000 s(-1).

D. Manganaris, M. K. Kim

The phase conjugation property of backward-stimulated photon echo (BSE) has numerous potential applications in optical data storage and processing. We demonstrate mixed binary multiplication of spatially encoded bit patterns, by taking advantage of the fact that the geometry of BSE is analogous to that of conventional holography or four-wave mixing of nonlinear optics, where an object (data) and a reference (write) beams interfere to create a grating inside the medium, and another reference (read) beam is diffracted from that grating. When all three input beams contain structures, the output pattern is the convolution and correlation of the input patterns, which, with certain arrangements and interpretation, can be used for multiplication of binary numbers. The experiments were done by using a 477.8 nm transition of praseodymium ion-doped in single-crystal lanthanum trifluoride.