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Manuel Forcales

Manuel Forcales. ___________________________________________ Group meeting, Feb. 2003 _____________________________________________. OPTICAL MEMORY EFFECT IN Si:Er. _____________________ Van der Waals-Zeeman Institute, University of Amsterdam ________________. &.

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Manuel Forcales

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  1. Manuel Forcales ___________________________________________Group meeting, Feb. 2003_____________________________________________

  2. OPTICAL MEMORY EFFECT IN Si:Er _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ & Free Electron Laser facility for Infrared eXperiments (FELIX) ___________________________________________Group meeting, Feb. 2003_____________________________________________

  3. Acknowledgements _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ Group members from the Van der Waals–Zeeman Institute (WZI): M. A. J. Klik , N.Q. Vinh, Dr. M. Wojdak and Dr. T. Gregorkiewicz FOM Institute “Rijnhuizen” (FEL Facility) staff members: Dr. I. Bradley, Dr. J-P.R. Wells Samples kindly provided by: Dr. A. Polman, AMOLF, The Netherlands Dr. Widdershoven, PRL, The Netherlands Dr. F. Priolo, IMETEM, Italy Dr. W. Jantsch, University of Linz, Austria Dr. J. Michel, MIT, USA Financial support (thank$): ARL-ERO, NWO, FOM ___________________________________________Group meeting, Feb. 2003_____________________________________________

  4. Outline _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________  Motivations  Introduction: data storage/Er3+ excitation  Photoluminescence (PL) experiments  Results  Conclusions ___________________________________________Group meeting, Feb. 2003_____________________________________________

  5. Intro I: Optical data storage _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ Need for all-optical data storage  writing, reading and erasing by photons write electronics CD Process of writing  Thermal in nature (melt, cool down) ... All optical process  FAST  Approaches: - Holographic optical storage (IBM, Lucent) - Hole burning read Optical memory effect observed in III-V semicond., but never in Si ___________________________________________Group meeting, Feb. 2003_____________________________________________

  6. Motivation for using Si Why Si? _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________  King of electronics  Environmentally friendly  Total control of dopants  potential for photonics? (Integration of electronics and photonics, on-chip) ___________________________________________Group meeting, Feb. 2003_____________________________________________

  7. Motivation for using erbium (Er) Why Er? _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________  Inner 4f-electron shell transitions  Sharp transitions in wavelength  Almost independent of host material Emission at 1.54 mm (telecommunications)   Are there other rare earth (RE) elements available? ___________________________________________Group meeting, Feb. 2003_____________________________________________

  8. Silicon doped with rare earths Si bandgap RE ground state Ce3+ Pr3+ Nd3+ Pm3+ Sm3+ Eu3+ Gd3+ Tb3+ Dy3+ Ho3+ Er3+ Tm3+ Yb3+ _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ ___________________________________________Group meeting, Feb. 2003_____________________________________________

  9. Er3+ excitation in an insulator (SiO2) ELECTRICALLY Patent by STM Electron impact excitation s 10-14 cm-2 LED with quantum efficiencies  10 % (similar to III-V semicond.) STMicroelectronics “New York Times, Oct. 2002 ” _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ OPTICALLY Er3+ ion Er PL @ 1.54 mm Er  12 ms EDFA Direct Er3+ excitation s 10-21 cm-2 All erbium can be excited We need laser to pump Er. We need resonant energies. BAD ! Solution ? Use sensitizers like nc-Si ___________________________________________Group meeting, Feb. 2003_____________________________________________

  10. Optical Er3+ excitation sensitized with nc-Si _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ nc-Si nc-Si Er Er • Current investigations are based on: • Excitation spectroscopy (power and wavelength dependence)  CW or pulsed • Kinetics (rise time, decay time), temperature dependence… How many optically active Er? , Excitation cross section?, Excitation/ Energy transfer mechanism?, Possibility to obtain GAIN? Dr. Wojdak ;-) ___________________________________________Group meeting, Feb. 2003_____________________________________________

  11. Optical Er3+ excitation in crystalline Si Nd:YAG Role of shallow traps excitation / de-excitation?  Mid infrared radiation Source  FREE ELECTRON LASER Er  1 ms CB CB VB _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ Er3+ ion Er-related Indirect excitation  s 10-15 cm-2  increased 6 orders of magnitude ! Generation of carriers optically  band-to-band excitation E > Egap (1170 meV) (also possible electrically) Er-related allows recombination level (electron and hole)  Er3+ excitation ___________________________________________Group meeting, Feb. 2003_____________________________________________

  12. Er3+ de-excitation in crystalline Si Up-conversion Er3+ ion Er3+ ion Energy migration Er3+ ion Er3+ ion > Egap _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ CB Er3+ ion Er-related +DE VB Back-transfer  Provided by DE (thermally or by FEL ) Ionization of traps may induce excitation or Auger de-excitation  Thermal effects quench completely RT emission at 1.54 mm ___________________________________________Group meeting, Feb. 2003_____________________________________________

  13. Free Electron Laser (FEL) facility _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ The magnetic field generates periodically curved electron trajectory The induced oscillating dipole moment leads to emission of radiation High brilliance and precise energy tuning: (70-170) meV ___________________________________________Group meeting, Feb. 2003_____________________________________________

  14. Photoluminescence experimental set-up Nd:YAG (532 nm) Dt FEL (10 mm ) emission @ 1.54 mm Tunable delay time (Dt) and variable power Ge / PMT _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ T = 4.2 K sample Spectrometer • Follow changes in: • Spectrum • Amplitude • Kinetics ___________________________________________Group meeting, Feb. 2003_____________________________________________

  15. Experimental set-up (real one) _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ ___________________________________________Group meeting, Feb. 2003_____________________________________________

  16. Photoluminescence of Si:Er   1 ms Intensity at 1.5 m Time (ms) _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ Er ions implanted: energy: 300 keV dose: 3*1012 cm-2 Er-concentration: 5*1017cm-3 Oxygen ions co-implanted: energy: 40 keV dose: 3*1013 cm-2 annealing: 900 oC (N2 atmosphere) time: 30 minutes.   1.5 m Intensity Wavelength (nm) ___________________________________________Group meeting, Feb. 2003_____________________________________________

  17. Afterglow and Er PL enhancement _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ Nd:YAG FEL Er PL 4.2 K tafterglow 100-150 ms No effect when FEL is fired before Nd:YAG ___________________________________________Group meeting, Feb. 2003_____________________________________________

  18. Dynamics of the enhancement effect _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ tafterglow tenhancement M. Forcales et al., Phys. Rev. B 65, 195208 (2002) ___________________________________________Group meeting, Feb. 2003_____________________________________________

  19. Model _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ matrix CB Er-related level Er3+ Nd:YAG, Ar+ Er PL FEL VB ___________________________________________Group meeting, Feb. 2003_____________________________________________

  20. Temperature dependence _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ ___________________________________________Group meeting, Feb. 2003_____________________________________________

  21. Single carrier excitation IFEL CB CB Er3+ ion Er-related VB Incorrect Model _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ Enhancement effect does not follow (IFEL)2, quadratic dependence M. Forcales et al., Phys. Rev. B 67, 0853xx (2003) ___________________________________________Group meeting, Feb. 2003_____________________________________________

  22. Ionization of traps fits the trap-ionization dependence: p = (-II+sqrt(I2I2+4I cINtr))/2c _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ Dependence on flux Enhancement amplitude FEL = 14 m MIR photon flux Enhancement has a  dependence related to one carrier excitation ___________________________________________Group meeting, Feb. 2003_____________________________________________

  23. Concept of a Si-based optical storage element _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ Writing beam λ1 (band-to-band) Storage array Storage element Reading beam λ2 (below band gap) Recovered signal at 1.54 mm M. Forcales et al., Solid State Electronics, vol. 47, 165 (2003) ___________________________________________Group meeting, Feb. 2003_____________________________________________

  24. Futures perspectives CB CB Er-related Atr VB _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________ • -Need to improve thermal stability! • How? Using deeper acceptor traps (Zn, Mg). • -No need to use free electron laser! • How? Table-top OPO, CO2 or cascade lasers… • Creation of electrons and holes separated in time! • How? Prepare the system by proper injection of carriers. Si-based optical elements could find applications in: - Telecommunication networks at 1.54 mm - Optical storage devices for use in all-photonic technology - Quantum computing ?… ___________________________________________Group meeting, Feb. 2003_____________________________________________

  25. Conclusions Observation of afterglow and optical memory effect in Si:Er system at temperatures T < 50 K The effect is a fundamental property of silicon (revealed by the optical dopant Er) Proper engineering, will allow long time storage and thermal stability _____________________Van der Waals-Zeeman Institute, University of Amsterdam________________  ___________________________________________Group meeting, Feb. 2003_____________________________________________

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