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Ultrafast THz Spectroscopy and Nonlinear Optical Properties of Semiconductor Nanostructures Zhen-Yu ZHAO 17 July 2008 Laboratoire Pierre Aigrain - Ecole.

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Presentation on theme: "Ultrafast THz Spectroscopy and Nonlinear Optical Properties of Semiconductor Nanostructures Zhen-Yu ZHAO 17 July 2008 Laboratoire Pierre Aigrain - Ecole."— Presentation transcript:

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 1

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

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

4 THz Radiation Section 1 1THz300μm1picosecond4.1meV10K Application THz spectroscopy : Semiconductor nanostructures 4

5 THz Time domain Spectroscopy Section 1 Ti : sapphire laser τ BS M2M5 M1 M3M4 Emitter Electro-Optic Sampling S ZnTe λ/4 WP Balanced photodiodes Probe beam Pump beam Free Space Electro-Optic Sampling THz emitter: Optical Rectification Optical Rectification Photoconductive antenna Photoconductive antenna 5 Δτ

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

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

8 8 Optical Rectification Section 1 1. Optical Rectification 2. Second Harmonic Generation 3. Two Photon Absorption4. Free Carrier Absorption ħωħω2ħω ħωħω ħωħω Nonlinear Crystals high state low state Conduction band Valence band 2ħω β: TPA coefficient Nonlinear Optical Processes

9 9 Optical Rectification Section 1 θ [001] Laser polarization 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 Lens :f=4cm ZnTe Rotation Laser beam THz radiation 15mm BBO Two Color Experiments Section 1 10

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

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

13 Interdigitated photoconductive emitter Section 1 Bias dependence 13

14 Interdigitated photoconductive emitter Section 1 ΓL 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) 14

15 Interdigitated photoconductive emitter Optimization by change the exciting intensity Section 1 15

16 Interdigitated photoconductive emitter Space Charge Screenings Effect Bias Field Coulomb Field Section High Optical FluxLow Optical Flux ++

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

18 Section 1 Comparison of 2 THz emitters ZnTe CrystalsInterdigitated Photoconductive antenna THz Amplitude10V/cm100V/cm Central Frequency2THz1THz~~1.4THz Bandwidth0.5~~2.7THz0~~3.5THz S/N500~ ~~

19 THz Quantum Cascade Laser Concept ħωħω Interband transitionInter-subband transition Semiconductor LaserQuantum Cascade Laser Section First Idea First Bell LabsTHz QCL Years Milestone 2.9 THz QCL 77k THz QCL 95k 1971

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

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

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

23 THz Gain Measurement Ti : sapphire laser τ BS M2M5 M1 M3M4 E THz FSEOS S ABC D Probe beam Pump beam Zone Active Section 1 23

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

25 THz Gain Measurement Section 1 Gain Clamping 25

26 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 27

28 Introduction Section 2 28 GlassΧ (3) ~ esu SiO PbO–42Bi 2 O 3 –12Ga 2 O Nb 2 O 5 –80TeO J. Lin et al. J. Non-Cryst. Solids 336 : 189–194 (2004) Photonic Glasses Y.Q. LI et al. J. Rare Earth 25 : 412 – 415 (2007) Er + Doped TeO 2 -Nb 2 O 5 - ZnO Glass Optical Switching Optical limiting Nanocrystals doped Tellurite Glasses Tellurite Glasses

29 Fabrication Melting: 80TeO 2 :20Nb 2 O 5 & 1%wt AgCl powder 800°C / 15minutes. Quenching: Annealed at 300°C Thermal treatment: At 360°C 30min, 60min, 90min, 120min Section 2 29

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

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

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

33 Characterization Cl - Ag + Jahn-Teller effect : Lattice deformation Cl - colour center Reaction: 2Cl - Cl 2 + 2e - & 2Ag + +2e-2Ag Section 2 33 H. Vogelsang, Phys. Rev. B 61: (2000)

34 Characterization EgEg Urbach law: Samples E g (eV) undoped min min min min min 1.7 Bandgap of glass matrix Bandgap redshift of treated glass EgEg Trapped state Section 2 34

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

36 Nonlinear Optical Properties Lock -In PC Ti :sapphire Laser M1M1 M2M2 LLLSD Z Open Aperture Z-scan Section 2 β: 1GW/cm ~~ 1.8 GW/cm 36

37 Nonlinear Optical Properties Section 2 Lock-In M1M2 M3 M4 M5BS Δτ PC LS K1K1 K2K2 2K 2 -K 1 2K 1 -K 2 D Ti :sap phire Laser Samples E g (eV) n0n0 χ (3) ( esu)n 2 ( esu) undoped min min min min min DFWM experiment 37

38 38 Section 2 Summary 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 39 Section 2: Nonlinear Optical Properties of AgCl Nanocrystals doped Tellurite Glasses Nonlinear Optical Properties of AgCl Nanocrystals doped Tellurite Glasses Fabrication Optical limiting performance and Two-photon absorption Enhancement of χ(3) Section 1: Development of THz Time Domain Spectroscopy (THz-TDS) Development of THz Time Domain Spectroscopy (THz-TDS) Competition OR TPA FCA, Azimuthal dependence Intervally scattering, Space charging screening, Electron mobility Application of THz – TDS Application of THz – TDS Gain Measurement of 2.9THz QCL

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


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