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Lund reports on atomic physics

Optical Memories and Processing in Time- and Frequency Domain

Baozhu Luo

Published Jan 1, 1998• 0 citations
OpenAlex

Abstract

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.

Related papers

Towards Efficient Quantum Memories in Rare-Earth-Ion-Doped Solids

A. Amari

This thesis describes experiments aimed at developing a key component in applications such as quantum networks and long-distance quantum communication systems: quantum memories. Quantum memories for light using photon-echo and coherent rephrasing techniques have been developed. The work is carried out on rare-earth-ion-doped inorganic crystals. Several properties are associated with these crystals such as long coherence times and long-lived ground state sublevels that are particularly interesting in connection applications in the area of quantum information science. It is demonstrated the preparation of optical inhomogeneous absorption profiles such that the light only interacts with a specific transition at a selected frequency. Narrow absorbing structures with widths of <100 kHz have been prepared with no absorption in the surrounding spectral interval. Most of the experiments were carried out using Pr3+:Y2SiO5. However, in our search for suitable a Λ-system in the material under consideration, we also performed spectral hole-burning spectroscopy in Nd:Y2SiVO4. As part of the search for host materials for Pr, Pr:La2(WO4)3 crystal was characterized using a variety of methods, such as, hole burning and photon-echoes. Electromagnetically induced transparency was also observed in this crystal. The most important criteria for evaluating quantum memory performance and the most important physical requirements are discussed. After investigating the standard photon echo techniques and controlled reversible inhomogeneous broadening (CRIB) for quantum state storage, we considered an efficient multimode quantum memory protocol; the atomic frequency comb (AFC) protocol. Combs with peaks of widths 100-300 kHz and an optical depth of~ 10 were created by optical pumping inside an emptied region of the inhomogeneous profile of Pr3+:Y2SiO5, allowing us to improve the efficiency of light storage. Light storage combining a photon-echo technique based on an AFC and spin-wave storage have been demonstrated, and an experimental AFC scheme for the storage of weak coherent light pulses in Pr3+:Y2SiO5 is presented. Finally, we have investigated superradiance and slow light effects. Both these effects occur in the high optical depth regime and can influence the memory performance. Under certain conditions superradiance results in the immediate re-emission of the stored light in a single burst of coherent radiation, and inside spectrally structured materials, slow light effects may result when storage is performed.

Lund reports on atomic physics•Jan 1, 2010•0 citations

On Some Problems of Time Domain Data Storage by Spectral Hole Burning

Rein K. Kaarli

Time-and-space-domain holography [1,2] by stimulated photon echoes [3] provides a means of storing temporal and spatial properties of an ultrafast-varying light signal and recalling its authentic replica at any later moment. The possibility of recording complex time shapes of light pulses, which also means time-domain optical data storage, is based on the ability of frequency-selective absorbers to store with high accuracy the temporal Fourier components of the incident light [1-3]. The time-domain frequency-selective optical storage of binary or analog data is an alternative approach to the concept of frequency-selective high-density data storage that provides a parallel ultrafast data storage and processing in the frequency domain. The shortest detail of the signal to be stored is limited by the reverse inhomogeneous bandwidth of the storing media which reaches 10-100 fs for frequency-selective materials while the duration of the signal is limited by phase relaxation time T2 (usually 10-3-10-6s).

Spectral Hole-Burning and Related Spectroscopies: Science and Applications•Jan 1, 1992•0 citations

Time-domain optical data storage using Eu3+ ions in crystals

Masaharu Mitsunaga

The photon-echo memory[1], or the time-domain optical data storage, resembles the hole-burning memory [2] in that the inhomogeneous absorption line of a material is employed as a storage medium and the information is stored in it as a frequency-dependent absorption change with the resolution determined by the homogeneous width. Having the common memory capacity N given by the inhomogeneous-to-homogeneous width ratio, both types of memories share common problems like low-temperature operation, spectral diffusion and so on. Although a storage medium is common, storage techniques are definitely different for the two memories. The photon-echo memory utilizes the temporal interference effect between a reference pulse and a data pulse and their interference pattern is stored as a population grating in the frequency domain. In this sense this is a time-domain analog of holography where the spatial interference pattern between a reference beam and a data beam is stored in a medium as a population grating in the real space. Like the spatially diffracted beam from the read beam gives the information stored in the hologram, the “temporally diffracted pulse", or the photon echo, after the read pulse can give the information stored in the inhomogeneous distribution.

Spectral Hole-Burning and Related Spectroscopies: Science and Applications•Jan 1, 1991•1 citation

Erasure of Data Stored by Pico- and Femtosecond Stimulated Photon Echoes in Frequency-Selective Materials

Rein K. Kaarli

Time-and-space-domain holography [1,2] by stimulated photon echoes [3] provides a means of storing temporal and spatial properties of an ultrafast-varying light signal and recalling its authentic replica at any later moment. The possibility of recording complex time shapes of light pulses, which also means time-domain optical data storage, is based on the ability of frequency-selective absorbers to store with high accuracy the temporal Fourier components of the incident light [1-3]. The time-domain frequency-selective optical storage of binary or analog data is an alternative approach to the concept of frequency-selective high-density data storage that provides a parallel ultrafast data storage and processing in the frequency domain. The shortest detail of the signal to be stored is limited by the reverse inhomogeneous bandwidth of the storing media which reaches 10-100 fs for frequency-selective materials while the duration of the signal is limited by phase relaxation time T2 (usually 10−9-10−6s).

International Conference on Ultrafast Phenomena•Jan 1, 1992•0 citations

High-speed, high-density, coherent time-domain optical memory. Final report, 1 September 1990-31 August 1993

Ravinder Kachru, Xiao A. Shen

The objective of this research was to quantitatively evaluate the concept of time-domain optical memory (TDOM) using the hole-burning mechanism. The TDOM concept offers both high speed and high memory density. The advantage of TDOM over traditional semiconductor memory is its inherent parallelism, which allows data to be stored and retrieved from the memory at much higher speed. The practical success of the proposed memory, therefore, depends critically on-among other issues-the storage, retrieval, and processing of images. In addition, new data storage techniques are needed to implement a practical memory. The last three years of this research program have focused on (1) development of new phase modulation techniques to enhance the storage, retrieval, and integrity of the stored information; (2) experimental studies of image storage and phase conjugate retrieval; (3) Image processing; and (4) practical holographic storage of images by using the hybrid time-frequency approach. Specifically, SRI demonstrated data encryption by phase modulating the read and write pulses. Image correlation and convolution was demonstrated and its implication for pattern recognition examined. Finally, this laboratory demonstrated high-fidelity random access and retrieval using holographic storage in Pr3+: YA103 with a single-frequency ring laser. These experiments have clearly demonstrated the practical viability ofmore » TDOM with existing technology. In the next stage of the research, the performance Issues such as bit-error-rates, signal-to-noise ratios, and laser stability need to be addressed. Stimulated photon echoes, Optical memory, Image processing, Pattern recognition, Phase conjugation.« less

•Nov 1, 1993•0 citations

Time-and-space-domain holography in frequency-selective spectral hole burning materials

Alexander Rebane

Time-and-space-domain holography [1,2] can be regarded as an extension of a conventional holographic process, where, in addition to the spatial image, the hologram plays back the time dependence of an event. The play-back of events is possible because we are using highly frequency-selective inhomogeneously broadened absorbers as recording material. This technique has a variety of potential applications in optical data storage and processing. In the present paper we consider the basic physical principle of time-and-space-domain storage in frequency-selective materials which exploit the effect of spectral hole burning [3]. In particular we will show that organic dye-doped spectral hole burning materials allow recording and playback of pi- co- and femtosecond time-scale events.

17th Congress of the International Commission for Optics: Optics for Science and New Technology•Sep 1, 1996•0 citations
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.
This thesis describes experiments aimed at developing a key component in applications such as quantum networks and long-distance quantum communication systems: quantum memories. Quantum memories for light using photon-echo and coherent rephrasing techniques have been developed. The work is carried out on rare-earth-ion-doped inorganic crystals. Several properties are associated with these crystals such as long coherence times and long-lived ground state sublevels that are particularly interesting in connection applications in the area of quantum information science. It is demonstrated the preparation of optical inhomogeneous absorption profiles such that the light only interacts with a specific transition at a selected frequency. Narrow absorbing structures with widths of <100 kHz have been prepared with no absorption in the surrounding spectral interval. Most of the experiments were carried out using Pr3+:Y2SiO5. However, in our search for suitable a Λ-system in the material under consideration, we also performed spectral hole-burning spectroscopy in Nd:Y2SiVO4. As part of the search for host materials for Pr, Pr:La2(WO4)3 crystal was characterized using a variety of methods, such as, hole burning and photon-echoes. Electromagnetically induced transparency was also observed in this crystal. The most important criteria for evaluating quantum memory performance and the most important physical requirements are discussed. After investigating the standard photon echo techniques and controlled reversible inhomogeneous broadening (CRIB) for quantum state storage, we considered an efficient multimode quantum memory protocol; the atomic frequency comb (AFC) protocol. Combs with peaks of widths 100-300 kHz and an optical depth of~ 10 were created by optical pumping inside an emptied region of the inhomogeneous profile of Pr3+:Y2SiO5, allowing us to improve the efficiency of light storage. Light storage combining a photon-echo technique based on an AFC and spin-wave storage have been demonstrated, and an experimental AFC scheme for the storage of weak coherent light pulses in Pr3+:Y2SiO5 is presented. Finally, we have investigated superradiance and slow light effects. Both these effects occur in the high optical depth regime and can influence the memory performance. Under certain conditions superradiance results in the immediate re-emission of the stored light in a single burst of coherent radiation, and inside spectrally structured materials, slow light effects may result when storage is performed.
Time-and-space-domain holography [1,2] by stimulated photon echoes [3] provides a means of storing temporal and spatial properties of an ultrafast-varying light signal and recalling its authentic replica at any later moment. The possibility of recording complex time shapes of light pulses, which also means time-domain optical data storage, is based on the ability of frequency-selective absorbers to store with high accuracy the temporal Fourier components of the incident light [1-3]. The time-domain frequency-selective optical storage of binary or analog data is an alternative approach to the concept of frequency-selective high-density data storage that provides a parallel ultrafast data storage and processing in the frequency domain. The shortest detail of the signal to be stored is limited by the reverse inhomogeneous bandwidth of the storing media which reaches 10-100 fs for frequency-selective materials while the duration of the signal is limited by phase relaxation time T2 (usually 10-3-10-6s).
The photon-echo memory[1], or the time-domain optical data storage, resembles the hole-burning memory [2] in that the inhomogeneous absorption line of a material is employed as a storage medium and the information is stored in it as a frequency-dependent absorption change with the resolution determined by the homogeneous width. Having the common memory capacity N given by the inhomogeneous-to-homogeneous width ratio, both types of memories share common problems like low-temperature operation, spectral diffusion and so on. Although a storage medium is common, storage techniques are definitely different for the two memories. The photon-echo memory utilizes the temporal interference effect between a reference pulse and a data pulse and their interference pattern is stored as a population grating in the frequency domain. In this sense this is a time-domain analog of holography where the spatial interference pattern between a reference beam and a data beam is stored in a medium as a population grating in the real space. Like the spatially diffracted beam from the read beam gives the information stored in the hologram, the “temporally diffracted pulse", or the photon echo, after the read pulse can give the information stored in the inhomogeneous distribution.
Time-and-space-domain holography [1,2] by stimulated photon echoes [3] provides a means of storing temporal and spatial properties of an ultrafast-varying light signal and recalling its authentic replica at any later moment. The possibility of recording complex time shapes of light pulses, which also means time-domain optical data storage, is based on the ability of frequency-selective absorbers to store with high accuracy the temporal Fourier components of the incident light [1-3]. The time-domain frequency-selective optical storage of binary or analog data is an alternative approach to the concept of frequency-selective high-density data storage that provides a parallel ultrafast data storage and processing in the frequency domain. The shortest detail of the signal to be stored is limited by the reverse inhomogeneous bandwidth of the storing media which reaches 10-100 fs for frequency-selective materials while the duration of the signal is limited by phase relaxation time T2 (usually 10−9-10−6s).
The objective of this research was to quantitatively evaluate the concept of time-domain optical memory (TDOM) using the hole-burning mechanism. The TDOM concept offers both high speed and high memory density. The advantage of TDOM over traditional semiconductor memory is its inherent parallelism, which allows data to be stored and retrieved from the memory at much higher speed. The practical success of the proposed memory, therefore, depends critically on-among other issues-the storage, retrieval, and processing of images. In addition, new data storage techniques are needed to implement a practical memory. The last three years of this research program have focused on (1) development of new phase modulation techniques to enhance the storage, retrieval, and integrity of the stored information; (2) experimental studies of image storage and phase conjugate retrieval; (3) Image processing; and (4) practical holographic storage of images by using the hybrid time-frequency approach. Specifically, SRI demonstrated data encryption by phase modulating the read and write pulses. Image correlation and convolution was demonstrated and its implication for pattern recognition examined. Finally, this laboratory demonstrated high-fidelity random access and retrieval using holographic storage in Pr3+: YA103 with a single-frequency ring laser. These experiments have clearly demonstrated the practical viability ofmore » TDOM with existing technology. In the next stage of the research, the performance Issues such as bit-error-rates, signal-to-noise ratios, and laser stability need to be addressed. Stimulated photon echoes, Optical memory, Image processing, Pattern recognition, Phase conjugation.« less
Time-and-space-domain holography [1,2] can be regarded as an extension of a conventional holographic process, where, in addition to the spatial image, the hologram plays back the time dependence of an event. The play-back of events is possible because we are using highly frequency-selective inhomogeneously broadened absorbers as recording material. This technique has a variety of potential applications in optical data storage and processing. In the present paper we consider the basic physical principle of time-and-space-domain storage in frequency-selective materials which exploit the effect of spectral hole burning [3]. In particular we will show that organic dye-doped spectral hole burning materials allow recording and playback of pi- co- and femtosecond time-scale events.