Coherent erasure of photon-echo data

Ulf Elman, Stefan Kröll

Ulf Elman, B. Luo, Stefan Kröll

Ulf Elman, B. Luo, Stefan Kröll

One important possible application of photon echoes is all-optical data storage. Photon echoes have a number of advantageous properties that make diem very good candidates for such applications, such as high areal density (1 Tb/cm2 has been projected [1], which should be compared with approximately 1 Mb/cm2 for commercially available CMOS memories today) and readout speeds >THz have been experimentally demonstrated [2]. We have addressed the problem of how to selectively erase data bits stored using photon echoes. One solution to this problem is to coherently add a new echo, phase shifted 180 degrees relative to the original echo, and thus achieve selective erasure of data [3].

Ulf Elman, Baozhu Luo, Stefan Kröll

Erasure of data stored by use of photon echoes has been investigated as a function of data writing time and data storage time. The results clarify the requirements on laser phase and frequency stability for performing photon-echo data erasure. The analysis of phase and frequency stability of a light source by the photon-echo erasure process is illustrated. A theoretical analysis emphasizing the physical processes that affect the erasure efficiency as well as an extensive discussion of possible error sources are given. Finally, an approach to bit-selective photon-echo data erasure that is insensitive to laser phase and frequency fluctuations is suggested.

Vitali V. Samartsev

Ulf Elman

Photon echoes have been studied both experimentally and theoretically, with the main part of the work centred around the concept of using photon echoes for all-optical data storage and processing. The four basic Boolean operators, AND, OR, NOT and XOR have been experimentally demonstrated using photon echoes. These constitute a complete set of Boolean operators. Selective erasure of digital data bits stored using photon echoes have been performed experimentally using three different laser systems with increasing frequency stabilities spanning three orders of magnitude, and the demands put on laser phase- and frequency stability using the suggested erasure method, have been studied. The effects of laser phase- and frequency fluctuations on both ordinary stimulated echoes and on coherently added echoes, have been analysed theoretically using the theory of stochastic processes. The resulting bit error rates in digital optical data processing systems due to such fluctuations have been considered. It has been shown possible experimentally to amplify photon echoes using fibre amplifiers, and to regenerate echoes from echoes amplified with this method. The advantages and limitations of this method for regeneration of photon echoes have been studied.