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Ultrafast THz Spectroscopy and Nonlinear Optical Properties of Semiconductor Nanostructures

Ultrafast THz Spectroscopy and Nonlinear Optical Properties of Semiconductor Nanostructures. Zhen-Yu ZHAO 17 July 2008 Laboratoire Pierre Aigrain - Ecole Normale Supérieure, Paris State Laboratory of Precise Spectroscopy - East China Normal University, Shanghai. Outline. Section 1:

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Ultrafast THz Spectroscopy and Nonlinear Optical Properties of Semiconductor Nanostructures

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  1. Ultrafast THz Spectroscopy and Nonlinear Optical Properties of Semiconductor Nanostructures Zhen-Yu ZHAO 17 July 2008 Laboratoire Pierre Aigrain - Ecole Normale Supérieure, Paris State Laboratory of Precise Spectroscopy - East China Normal University, Shanghai

  2. Outline • Section 1: • Development of THz Time Domain Spectroscopy (THz-TDS) • Optical Rectification • Micro-PhotoconductiveEmitter • Application of THz - TDS • Gain Measurement of Quantum Cascade Laser (QCL) • Section 2: • Nonlinear Optical Properties of AgCl Nanocrystals doped Tellurite Glasses • Fabrication • Characterization • Nonlinear Optical Measurement

  3. Section 1 Development & Application of THz Time Domain Spectroscopy

  4. THz Radiation • Section 1 1THz↔300μm↔1picosecond↔4.1meV↔10K Application THz spectroscopy : Semiconductor nanostructures http://www.thznetwork.org

  5. THz Time domain Spectroscopy M1 Ti : sapphire laser Balanced photodiodes S ZnTe WP Pump beam BS Emitter λ/4 τ Electro-Optic Sampling Probe beam M2 M3 M4 M5 • Section 1 Δτ Free SpaceElectro-OpticSampling • THzemitter: • Optical Rectification • Photoconductiveantenna

  6. Optical Rectification THz radiation Lens Laser pulse, Δτ :100fs, λ :800nm Z ZnTe crystals SHG & Transmitted beam • Section 1 FFT

  7. Optical Rectification • Section 1 Picarin Lens Z Teflon Bolometer Z Filter Lens PMT Z Lens Photodiode

  8. Section 1 Optical Rectification Nonlinear Optical Processes 1. Optical Rectification 2. Second HarmonicGeneration ħω 2ħω Nonlinear Crystals Nonlinear Crystals 3. Two Photon Absorption 4. Free Carrier Absorption high state Conduction band ħω 2ħω ħω β: TPA coefficient low state Valence band

  9. Section 1 Optical Rectification [001] Laser polarization θ ZnTe X.-C. Zhang et al. J. Opt. Soc. Am. B 18 : 823 (2001) D.C. Hutchings and B.S. Wherrett, J. Opt. Mod.41: 1141 (1994)

  10. Optical Rectification 15mm Lens :f=4cm ZnTe BBO Laser beam THz radiation Rotation • Section 1 TwoColorExperiments

  11. Interdigitated photoconductive antenna • Section 1 + Laser pulse, Δτ :100fs, λ :800nm Hemisphere Si lens Conventional Photoconductive antenna —

  12. - + Interdigitated photoconductive antenna stripline gap1.5µm Electrods 500µm Opaques A. Dreyhaupt et al. Appl. Phys. Lett. 86 :121114 (2005) A. Dreyhaupt et al. Opt. Lett. 31 :1546 (2006) Nathan Jukam, UCSB

  13. Interdigitated photoconductive emitter • Section 1 Bias dependence

  14. Interdigitatedphotoconductiveemitter • Section 1 Γ→L Intervalley scattering C. Ludwig and J. Kuhl, Appl. Phys. Lett. 69 (9), 1194 (1996) J.-H. Son, T. B. Norris, and J. F. Whitaker, J. Opt. Soc. Am. B 11, 2519 (1994)

  15. Interdigitatedphotoconductiveemitter • Section 1 Optimization by change the exciting intensity

  16. Interdigitatedphotoconductiveemitter • Section 1 Space Charge Screenings Effect Low Optical Flux High Optical Flux - - + — + — Bias Field Coulomb Field

  17. Interdigitatedphotoconductiveemitter • Section 1 Temperature Dependence of THz emitter J. S.Blakemore, J. Appl. Phys.53: R123-R181 (1982)

  18. Comparison of 2 THzemitters • Section 1

  19. THz Quantum Cascade Laser • Section 1 Concept Semiconductor Laser Quantum Cascade Laser ħω Interband transition Inter-subband transition Milestone 1970 1980 1990 2000 1994 2002 2004 2006 1971 Years First QCL @ Bell Labs THz QCL 2.9 THz QCL 77k 1.9 THz QCL 95k First Idea

  20. THz Quantum Cascade Laser • Section 1 Bound to Continuum Active-injection Region of 2.9THz QCL

  21. (a) Metal Contact Metal 220µm 12µm Bottom n+ layer Active Region SI Substrate • Section 1 THz Quantum Cascade Laser Surface Plasmon Waveguide of 2.9 THz QCL 220µm MPQ-Paris VII

  22. THz Quantum Cascade Laser V THz QCL THz Collimation Pyroelectric Detector A • Section 1 Characterization of 2.9 THz QCL

  23. THz Gain Measurement M1 Ti : sapphire laser S D A B C Pump beam BS ETHz τ FSEOS Probe beam M2 M3 M4 M5 • Section 1 Zone Active

  24. THz Gain Measurement • Section 1 Amplified THz transmission by gain of quantum cascade laser 2.9THz THz Gain at different injection current THz Gain at different temperature

  25. THz Gain Measurement • Section 1 Gain Clamping

  26. Section 1 Summary 1 • Development of THz-TDS • THz performance of ZnTe crystal. • THz output of interdigitated photoconductive antenna • Application of THz-TDS • First measurement of Gain of 2.9 THz Quantum Cascade Laser

  27. Section 2 Nonlinear Optical Properties of AgCl NCs doped Tellurite Glasses

  28. Introduction • Section 2 Photonic Glasses Tellurite Glasses Optical Switching Optical limiting Er+ Doped TeO2-Nb2O5-ZnO Glass ------J. Lin et al. J. Non-Cryst. Solids336 : 189–194 (2004) ------Y.Q. LI et al. J. Rare Earth25 : 412 – 415 (2007) Nanocrystals doped Tellurite Glasses

  29. Fabrication • Section 2 • Melting: • 80TeO2:20Nb2O5 & 1%wt AgCl powder • 800°C / 15minutes. • Quenching: • Annealed at 300°C • Thermal treatment: • At 360°C • 30min, 60min, 90min, 120min

  30. Characterization • Section 2 Nanocrystals FESEM Image vs Termal treatment time (b) 60min thermal treated (a) 30min thermal treated

  31. Characterization • Section 2 Nanocrystals FESEM Image vs Termal treatment time (d) 120min thermal treated (c) 90min thermal treated

  32. Characterization • Section 2 Size distribution function vs thermal treatment time 12nm / 30 min 17nm / 60 min 26nm / 90 min 35nm / 120 min

  33. Characterization • Section 2 Jahn-Teller effect : Lattice deformation Cl- Ag+ Reaction: 2Cl- →Cl2 + 2e- & 2Ag++2e-→2Ag Cl- colour center H. Vogelsang, Phys. Rev. B61: 1847-1852 (2000)

  34. Characterization • Section 2 Urbach law: Trapped state Eg Eg Bandgap of glass matrix Bandgap redshift of treated glass

  35. Nonlinear Optical Properties • Section 2 lens lens Powermeter 50% BS Attenutation Sample Powermeter

  36. Nonlinear Optical Properties PC M1 Ti :sapphire Laser Z Lock-In M2 L S L L D • Section 2 Open Aperture Z-scan β: 1GW/cm ~~ 1.8 GW/cm

  37. Nonlinear Optical Properties Ti :sapphire Laser Δτ PC Lock-In BS M5 2K1-K2 D M4 K1 K2 M3 L S 2K2-K1 M1 M2 • Section 2 DFWM experiment

  38. Summary 2 • Section 2 • Nonlinear optical properties of AgCl NCs doped tellurite glass • Samples were Prepared by Melt-Quenching and Thermal Treatment Methods • Characterization with Microscopic and Spectroscopic Methods • Nonlinear Optical Properties were Measured by Z-scan, Optical Limiting and DFWM

  39. Conclusion • Section 1: • Development of THz Time Domain Spectroscopy (THz-TDS) • Competition OR TPA FCA, Azimuthaldependence • Intervallyscattering, Spacecharging screening, Electron mobility • Application of THz – TDS • Gain Measurement of 2.9THz QCL • Section 2: • Nonlinear Optical Properties of AgClNanocrystals doped Tellurite Glasses • Fabrication • Optical limiting performance and Two-photon absorption • Enhancement of χ(3)

  40. Acknowledgement • THz group (LPA-ENS) Advisor: Jérôme Tignon Staff members: Sophie Hameau, Sukhdeep Dhillon et al. Postdoc: Nathan Jukam; Ph.Dstudent: Dimitri Oustinov; Master student: Julien Amijo, GeogDürr; Techniciens: Pascal Morfin, Phillipe Pace et al. Collaborators: Carlo Sirtori et al. • Sun’s Group (East China Normal University) Co-Advisor: Zhenrong Sun, Staff members: TianqingJia, Xiaohua Yang et al. Collaborators: Jian Lin, et al.

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