New Approach to 3d Optical Memory pra-0079

Full Title A New Approach to 3D Optical Memory Tech Area / Field

• PHY-OPL: Physics / Optics and Lasers

• INF-ELE: Information and Communications / Microelectronics and Optoelectronics

Brief Description of Technology The project objective is to develop a new approach to the problem of 3D information storage. Three-dimensional optical data storage offers the potential for large recording capacities of up to 10¹⁰ bits/cm³. Nonlinear material response to the impact of ultra-short laser pulses is used for this purpose. Our proposal comprises the main trend of [1] when using materials of the types that are common in such an approach [2,3]. Our method consists of creating submicrometer-sized holes that have a large contrast in index of refraction and can be read out by transmitted, or even scattered light. We apply for this purpose a much less expensive femtosecond laser with a pulse energy of about 2 nJ and a repetition rate of 10⁸ Hz — in contrast to [1] when an expensive 100 fs powerful laser system, with a regenerative amplifier of a pulse energy up to 1 J, and repetition rate about 10 Hz, is used. As a recording media we use the specially created polymer-photochromic composition that exhibits the essential two-photon absorption at the wavelength of irradiation, followed by photochemical transformations.

The research will be focused upon the following trends: — Investigations into physical processes involved in the formation of structurally altered sites for information recording. These processes have not been yet fully understood. — Research and development of new polymer compositions as recording media with high performance. — Investigations into possibilities of creation of readout systems based on the registration of the backscattered light.

References

1. E.N.Gleser, M.Milosaljevic, L.Huang, R.J.Finlay, T.H. Her, J.P.Callan, and E.Mazur, Optics Letters, v.21, p.2023 (December 1996).

2. A.S.Dvornikov, J.Malkin, P.M.Rentzepis, J.Phys.Chem., v.98, p.6746 (1994).

3. A.Toriumi, J.M.Herrmann, S.Kawata, Optics Letters, v.22, p.555 (April 1997).

Legal Aspects None.

Generation of Subnanosecond Millimeter-Wave Pulse Based on Superradiance pra-0080

Full Title Generation of Subnanosecond Millimeter-Wave Pulse Based on Superradiance Tech Area / Field

• PHY-RAW: Physics / Radiofrequency Waves

Brief Description of Technology Novel physical phenomena, namely superradiance from single electron bunches, was suggested for use in the generation of intense microwave pulses of ultrashort duration. Different types of superradiance were studied experimentally and in association with several different types of emission — including Cherenkov, cyclotron and bremstrahlung mechanisms — when the electron bunches were passed through slow wave structures, rotated in a magnetic field or oscillated in wiggler fields. Megawatt power level millimeter-wave pulses of uniquely short duration (0.3-0.5 ns) have been generated.

Superradiance occurs in a specific situation when the electron pulse duration significantly exceeds the operating wavelength (otherwise the radiation is effectively spontaneous), but is less than the interaction length (in contrast with traditional mechanisms of stimulated emission of quasi-continuous electron beams that are used extensively in microwave electronics). Coherent emission from the entire electron pulse can only take place when a self-bunching mechanism typical for stimulated emission develops.

Legal Aspects None in this research.

Special Facilities in Use and Their Specifications The unique table-top RADAN 303 accelerator with a subnanosecond slicer was used to inject typically 0.3-0.5 ns, 0.2-1 kA, 250 keV electron pulses. These electron pulses were generated from a magnetically insulated coaxial diode which utilized a cold explosive emission cathode. The accelerator is capable of repetitive operation, up to a 100 pps regime.

Scientific Papers N.S.Ginzburg, I.V.Zotova and A.S.Sergeev, "Cyclotron Superradiance of a moving electron swarm under group synchronisation conditions,” Sov. JETP Lett, Vol. 60, No.7, pp. 513-515 (1994).

N.S.Ginzburg, I.V.Zotova, I.V.Konoplev, A.S.Sergeev, V.G.Shpak, S.A.Shunailov, M.R.Ul'maskulov, and M.I.Yalandin, "Experimental observation of cyclotron superradiance," Sov. JETP Lett., Vol. 63, No.5, pp. 331-335 (1996).

N.S.Ginzburg, I.V.Zotova, I.V.Konoplev, A.S.Sergeev, A.D.R.Phelps, A.W.Cross, S.J.Cooke, V.G.Shpak, S.A.Shunailov, M.R.Ul'maskulov, and M.I.Yalandin, "Experimental observation of cyclotron superradiance under group synchronism conditions," Phys.Rev.Lett, Vol.78, No.12, pp.2365-2368 (1997).

N.S.Ginzburg, A.S.Sergeev, I.V.Zotova, Yu.N.Novozilova, N.Yu. Peskov, I.V.Konoplev, A.D.R.Phelps, A.W.Cross, S.J.Cooke, P.Aitken, V.G.Shpak, M.I.YalandinS.A.Shunailov, M.R.Ul'maskulov, and M.I.Yalandin, "Experimental observation of superradiance in millimeter-wave band," Nucl.Inst. and Meth. in Phys.Res.A, in press (1997).