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Lund reports on atomic physics

Investigations of Issues Relevant to the Application of Photon Echoes in Information Technology

Ulf Elman

Published Jan 1, 1998• 2 citations
OpenAlex

Abstract

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.

Related papers

Influence of laser phase and frequency fluctuations on photon-echo data erasure

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.

Journal of the Optical Society of America B•Sep 1, 1996•18 citations

The effect of laser frequency and phase fluctuations on coherent addition and erasure of photon echoes

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].

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jan 1, 1996•0 citations

Theoretical Modelling of Temporal Compression of Optical Pulses and Pulse Sequences Using Photon Echoes

Mikael Afzelius

In recent years possible applications of the photon echo process in optical processing, data storage systems, bit-rate conversion of optical pulses, time compression of optical pulses etc. have been investigated.Much of this research aim at replacing electrical components in the framework of today's information networks with components that are entirely based on optics.It is likely that we in the future will see more and more of the electrical components linked to a fibre network being replaced by all optical components, e.g.routers and bit-rate converters.The concept of temporal compression of optical pulses, which is the subject of this thesis, could be used to increase the transmission rate through optical fibres and thereby use the full capacity of today's fibres.It should also be mentioned that more basic components, e.g.XOR gates, are studied in this research field and these components could possibly be used in future concepts of a "light-computer".In this thesis a theoretical model of time compression of both single optical pulses and optical pulse sequences using photon echoes is presented.A full analytical treatment was done for gaussian shaped pulses as a first step of building a numerical model.An analytic approximate approach was also used for both square pulses and pulse sequences.A theoretical understanding of the duration, the intensity spectrum and peak intensity of the compressed signals was reached.It is shown that the intensity spectrum of a compressed pulse sequence containing N bits is completely analogous to the pattern observed in the well-known Fraunhofer diffraction experiment with N slits.A numerical model was built and used to evaluate how non-linearities and noise affect the degree of compression.In addition theoretical models were developed to explain the effects of non-linearities and noise and the hope is that these might be used as guidelines on how to design future experiments in order to achieve highest possible degree of compression.Some of the results presented in this thesis is compared with experimental data obtained in the research group during the time this work was going on.

Lund reports on atomic physics•Jan 1, 2000•2 citations

Statistical Modeling and Theoretical Analysis of the Influence of Laser Phase Fluctuations on Photon Echo Data Erasure and Stimulated Photon Echoes

Ulf Elman, Stefan Kröll

The effect of random laser phase fluctuations on stimulated photon echoes (SPEs) and on coherently added SPEs was studied and evaluated both experimentally and analytically with statistical methods. The general concept of describing laser frequency fluctuations as a stationary stochastic process is presented and applied to three specific SPE configurations. The effect of phase fluctuations on erasing an SPE by coherently adding another SPE, phase-shifted by 180 degrees relative to the first, is presented.

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Multi-Bit Data Storage Using Photon Echoes

Mattias Nilsson

The diffraction-limited spot size of a focused laser beam puts an upper boundary on the storage densities in conventional optical data storage. This can be overcome by storing multiple bits of data in each spatial location. In materials with an inhomogeneously broadened absorption line, such as crystals doped with rare-earth ions, frequency can be used as an additional addressing dimension. In some materials the number of spectral channels can be as high as 107. Spectral data storage can be done using coherent transient interactions between light and atoms and can be described in terms of photon echo processes. In this Master's Project the swept-carrier time-domain (SCTD) approach, a hybrid between frequency- and time-domain approaches, is used. An overview of the theory is given, followed by a description ofthe set-up and equipment. A maximum of 330 bits of data have been stored in one spatial location. The necessary conditions for successful storage and retrieval of data have been examined and suggestions are given on how to extend the results further.

Lund reports on atomic physics•Jan 1, 2000•2 citations

Optical Memories and Processing in Time- and Frequency Domain

Baozhu Luo

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.

Lund reports on atomic physics•Jan 1, 1998•0 citations
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.
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.
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].
In recent years possible applications of the photon echo process in optical processing, data storage systems, bit-rate conversion of optical pulses, time compression of optical pulses etc. have been investigated.Much of this research aim at replacing electrical components in the framework of today's information networks with components that are entirely based on optics.It is likely that we in the future will see more and more of the electrical components linked to a fibre network being replaced by all optical components, e.g.routers and bit-rate converters.The concept of temporal compression of optical pulses, which is the subject of this thesis, could be used to increase the transmission rate through optical fibres and thereby use the full capacity of today's fibres.It should also be mentioned that more basic components, e.g.XOR gates, are studied in this research field and these components could possibly be used in future concepts of a "light-computer".In this thesis a theoretical model of time compression of both single optical pulses and optical pulse sequences using photon echoes is presented.A full analytical treatment was done for gaussian shaped pulses as a first step of building a numerical model.An analytic approximate approach was also used for both square pulses and pulse sequences.A theoretical understanding of the duration, the intensity spectrum and peak intensity of the compressed signals was reached.It is shown that the intensity spectrum of a compressed pulse sequence containing N bits is completely analogous to the pattern observed in the well-known Fraunhofer diffraction experiment with N slits.A numerical model was built and used to evaluate how non-linearities and noise affect the degree of compression.In addition theoretical models were developed to explain the effects of non-linearities and noise and the hope is that these might be used as guidelines on how to design future experiments in order to achieve highest possible degree of compression.Some of the results presented in this thesis is compared with experimental data obtained in the research group during the time this work was going on.
The effect of random laser phase fluctuations on stimulated photon echoes (SPEs) and on coherently added SPEs was studied and evaluated both experimentally and analytically with statistical methods. The general concept of describing laser frequency fluctuations as a stationary stochastic process is presented and applied to three specific SPE configurations. The effect of phase fluctuations on erasing an SPE by coherently adding another SPE, phase-shifted by 180 degrees relative to the first, is presented.
The diffraction-limited spot size of a focused laser beam puts an upper boundary on the storage densities in conventional optical data storage. This can be overcome by storing multiple bits of data in each spatial location. In materials with an inhomogeneously broadened absorption line, such as crystals doped with rare-earth ions, frequency can be used as an additional addressing dimension. In some materials the number of spectral channels can be as high as 107. Spectral data storage can be done using coherent transient interactions between light and atoms and can be described in terms of photon echo processes. In this Master's Project the swept-carrier time-domain (SCTD) approach, a hybrid between frequency- and time-domain approaches, is used. An overview of the theory is given, followed by a description ofthe set-up and equipment. A maximum of 330 bits of data have been stored in one spatial location. The necessary conditions for successful storage and retrieval of data have been examined and suggestions are given on how to extend the results further.
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.