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Lund reports on atomic physics

Photon Echo Optical Processing.

Ulf Elman

Published Jan 1, 1992• 0 citations
OpenAlex

Abstract

This diploma paper gives a survey of the possibilities to do optical processing and data storage with the photon echo concept, and results from experiments and numerical calculations performed within this area of research.Bitwise logical 'and' operations of two eight-bit words has been performed experimentally.Optical pulse sequences have been reemitted from a sample unchanged, reversed, compressed and expanded, and pulse sequences have been convoluted and correlated with each other experimentally by means of the photon echo process.

Related papers

Photon-echo-based logical processing

Stefan Kröll, Ulf Elman

Word-by-word logical AND and OR operation with photon-echo processing is demonstrated for what is to our knowledge the first time. The photon-echo process can store sequences of optical data before processing. The present logical operations on 8- and 4-bit words are performed by using single-shot frequency-chirped photon echoes. Data rates of approximately 1 MHz, input energies of 1-10 nJ/bit, and output energies in the picojouleper-bit range are demonstrated by using a transition with a transition probability of only 20 s(-1).

Optics Letters•Nov 1, 1993•30 citations

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

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.

Lund reports on atomic physics•Jan 1, 1998•2 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

Photon-echo-based Optical Data Compression Using an External Cavity Diode Laser

Xiangjun Wang

Single pulse compression and multi-bit pulse compression using the photon echo process was investigated.A single pulse could be compressed by a factor of 454 from 10 microseconds to 22 nanoseconds.A 1 O-bits pulse train was compressed by a factor of 92 from 20 microseconds in total length to 212 nanoseconds.The compression factors obtained during this work were an order of magnitude better than those published previously both for single pulse and multi-bit pulse train compression.Observation of the side-band under the envelope of the photon echo signal in multi-bit pulse compression indicates that the bit information is retained in the compression.Some improvements were achieved by optimising the experimental setup during the work.The experimental results were discussed theoretically and were good in agreement with theoretical calculations.The space-time duality of photon echo compression was also analysed in this thesis.The storage material used in the experiment is a Y AG crystal doped with the trivalent rare earth thulium ion with a concentration at 0.1-at.%.The crystal was kept at 4K during the experiment.The absorption, an important characteristic of the crystal was initially measured.The maximum absorption was about 40%, in the range between 7931.50A and 7931.60A with a full width ofhalfmaximum of3.5 A, which corresponds to 19 GHz.A homemade external cavity diode laser equipped with an intra-high coherency and ultrahigh-speed frequency chirping properties was used in the experiments.This system with an intra-cavity electro-optic crystal (EOC) was employed for the optical data compression because of its advantages of simplicity, high quantum efficiency, low cost, and compact size, which is necessary for practical applications in the future.Some critical properties for this laser were investigated.The laser line-width was measured to be 350 KHz over a 200 microseconds duration using the spectral hole burning method and a voltage-chirping rate of about 7 MHz/V was determined by calculations and experimental measurements.

Lund reports on atomic physics•Jan 1, 1999•3 citations

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

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.

CRC Press eBooks•Feb 24, 2004•0 citations

Stimulated Photon Echo \& Photon Echo Relaxation Measurements.

S. Andrae

The first part of this diploma paper gives a survey of a concept for fast high-density optical information storage and processing using the so-called stimulated photon echo.The second part describes photon echo relaxation measurements made on the 3 H -1 D transition in 0. 1% Pr 3 +: YAlO in external magnetic fields. 2 3These measurements were performed at the Department of Atomic Physics, Lund Institute of Technology during the first part of 1991 in order to investigate the magnetic field dependence of the photon echo decay in the crystal at liquid helium temperatures.

Lund reports on atomic physics•Jan 1, 1991•0 citations
This diploma paper gives a survey of the possibilities to do optical processing and data storage with the photon echo concept, and results from experiments and numerical calculations performed within this area of research.Bitwise logical 'and' operations of two eight-bit words has been performed experimentally.Optical pulse sequences have been reemitted from a sample unchanged, reversed, compressed and expanded, and pulse sequences have been convoluted and correlated with each other experimentally by means of the photon echo process.
Word-by-word logical AND and OR operation with photon-echo processing is demonstrated for what is to our knowledge the first time. The photon-echo process can store sequences of optical data before processing. The present logical operations on 8- and 4-bit words are performed by using single-shot frequency-chirped photon echoes. Data rates of approximately 1 MHz, input energies of 1-10 nJ/bit, and output energies in the picojouleper-bit range are demonstrated by using a transition with a transition probability of only 20 s(-1).
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.
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.
Single pulse compression and multi-bit pulse compression using the photon echo process was investigated.A single pulse could be compressed by a factor of 454 from 10 microseconds to 22 nanoseconds.A 1 O-bits pulse train was compressed by a factor of 92 from 20 microseconds in total length to 212 nanoseconds.The compression factors obtained during this work were an order of magnitude better than those published previously both for single pulse and multi-bit pulse train compression.Observation of the side-band under the envelope of the photon echo signal in multi-bit pulse compression indicates that the bit information is retained in the compression.Some improvements were achieved by optimising the experimental setup during the work.The experimental results were discussed theoretically and were good in agreement with theoretical calculations.The space-time duality of photon echo compression was also analysed in this thesis.The storage material used in the experiment is a Y AG crystal doped with the trivalent rare earth thulium ion with a concentration at 0.1-at.%.The crystal was kept at 4K during the experiment.The absorption, an important characteristic of the crystal was initially measured.The maximum absorption was about 40%, in the range between 7931.50A and 7931.60A with a full width ofhalfmaximum of3.5 A, which corresponds to 19 GHz.A homemade external cavity diode laser equipped with an intra-high coherency and ultrahigh-speed frequency chirping properties was used in the experiments.This system with an intra-cavity electro-optic crystal (EOC) was employed for the optical data compression because of its advantages of simplicity, high quantum efficiency, low cost, and compact size, which is necessary for practical applications in the future.Some critical properties for this laser were investigated.The laser line-width was measured to be 350 KHz over a 200 microseconds duration using the spectral hole burning method and a voltage-chirping rate of about 7 MHz/V was determined by calculations and experimental measurements.
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.
The first part of this diploma paper gives a survey of a concept for fast high-density optical information storage and processing using the so-called stimulated photon echo.The second part describes photon echo relaxation measurements made on the 3 H -1 D transition in 0. 1% Pr 3 +: YAlO in external magnetic fields. 2 3These measurements were performed at the Department of Atomic Physics, Lund Institute of Technology during the first part of 1991 in order to investigate the magnetic field dependence of the photon echo decay in the crystal at liquid helium temperatures.