THz Physik: Grundlagen und Anwendungen

Transkript

1 TH Physi: Grunlagen un Anwenungen Inhalt: 1. Einleitung. Wechselwirung von TH-Strahlung it Materie 3. Ereugung von TH-Strahlung 3.1 Eletronische Ereugung 3. Photonische Ereugung 3.3 Nachweis von TH-Strahlung 3.4 Nichtlineare Methoen 4. Ereugung ultraurer Pulse (Grunlagen) 5. TH-Opti 6. TH-Zeitbereichs-Spetrosopie 6.1 Kopleer Brechungsine 6. Fouriertransforation 7. Anwenungen

2 Typische Koponenten Spiegel Linsen Polarisatoren Anti-Refle-Beschichtungen Wellenplatten Wellenleiter

3 TH wave guie sensor Transverse resonance conition for TE-oes: t c TH t cos upper lower upper lower TH t TH TH t t GH µ Phase shift at bounary: Sensitive to - type of bining to surface - surface asorbate interaction - polariibility of asorbates - ipole-ipole interactions

4 TH wave guie sensor Wave guie oes: Spectral aplitue [b. E.] ,5 1,0 1,5,0,5 3,0 Frequency [TH] Spectral aplitue [b. E.] ,5 1,0 1,5,0, ,0 Frequency [TH] 1 GaAs 80µ 40µ Wave guie thicness t Angle frequency frequency Intensity [a.u.] Intensity [a.u.] 0 Distance coupling strength Frequency [TH]

5 Parallel-Plate Waveguies quasi-optic approach layout PPWG TH TH out in Si lens gap icro crystals polishe etal plates (aluinu, copper, ) silicon lenses for coupling sub-wavelength gap for copression (< 50 µ) aplitue transission high (> 0%) easureent of thin fils enhanceent factor TH fiel is presse into the saple, stronger interaction but saple ount too cople R. Menis an D. Grischowsy, Opt. Lett., Vol. 6, (001)

6 Waveguie TH-TDS Eperiental apparatus Microwave approach TH tie-oain spectroscopy syste bea waist between two parabolic irrors TH spot sie appro. 9 µ in the center R. Menis an D. Grischowsy, Opt. Lett., Vol. 6, (001)

7 Waveguie TH-TDS Eperiental apparatus Microwave approach TH for tie-oain funnel using spectroscopy coercial etal syste shi bea ajust waist opening between an curvature two parabolic to optiie irrorscoupling TH aiabatic spot sie copression appro. 9 of µ the in TH the wave center M. Theuer, D. R. Grischowsy, an R. Beigang, t- Technisches Messen, Vol. 78, No. 5, pp (011)

8 Coupling using Metal Flares Coupling Ratio Opening [] gap sie Aplitue Transission PPWG flare coupling PPWG Si optics Frequency [TH] flares show coupling ratio of 39% at 50 µ gap etal shi perfors even better than Si optics no transission optics or echo pulses Broaban coupling without isturbing oulations M. Theuer, D. R. Grischowsy, an R. Beigang, t- Technisches Messen, Vol. 78, No. 5, pp (011)

9 Flare couple parallel-plate waveguie (PPWG) Layout thin fil TH in flare gap 3 c length PPWG icro crystals TH out Tiny Easy single-crystalline to anufacture fil is fore on the shi Microgra No transission saple optics ass sufficient Technique Cheap, available is highly coponents sensitive Stanar surface quality sufficient Appropriate saple ount Goo theral contact Microscope iage (TCNQ) M. Theuer, D. R. Grischowsy, an R. Beigang, t- Technisches Messen, Vol. 78, No. 5, pp (011)

10 High-resolution spectroscopic results Flare couple PPWG at 77 K 1 10 salicylic aci TCNQ 1,-DCB 8 Absorbance Frequency [TH] Absorption features as narrow as 30 GH easure Fingerprint signatures ientical to Si-lens PPWG M. Theuer an J. S. Melinger, Journal of Infrare, Millieter an Terahert Waves, Springer New Yor, Vo. 3, No. 11, pp (011)

11 Surface Plason Polaritons SPP Surface plason polaritons: Funaental interest: Applications: eciation an propagation of SPPs, transission through sub wavelength holes, propagation in perioic an rano eia, Anerson localiation, nano optics,... plason base sensors, propagation along wires, superfocusing, iaging, enhance TH eission, filter, active plasonic coponents,...

12 Plasonen Festörper Oberfläche Nanopartiel (loalisierte Plasonen)

13 Surface plason polariton: EM wave at etal-ielectric interface EM Welle oppelt an ie Plasa-Osillationen er Oberflächenlaungen t i e E t E,0,, t i e E t E,0 ),, ( Für propagierene gebunene Wellen - real - iaginär

14 Wellengleichung: SP-Welle un Ranbeingungen: Dispersions-Relation: 1/ " ' c i,, 0, 0, t E E (Ausbreitungsrichtung) c Norale Dieletria: SPP-Dispersions-Relation: ()

15 1/ " ' c i -irection: Gebunene SP-Moen: iaginär: + < 0, real: < 0 also: < - 1/,,, " ' c i -irection: c SPP-Dispersions-Relation: ()

16 Dielectric constant of etals Drue Moel: Leitungseletronen it Däpfung (eine Rücstellräfte) Bewegungsgleichung: t t ee 0 e it P Ne Ne p E E i i it inverser Stoßeit un Plasafrequen: ( << p ) p p ' 1, " 3 p Ne 0

17 SPP-Dispersion: c Raiative oes c ' > 0) 1/ real real p 1 p Quasi-boun oes < ' < 0) iaginary real Dielectric: Metal: = ' + " Boun oes (' < ) real iaginary Re

18 Anregung von SPPs

19 Anregung von SPPs (Kretschann)

20 Anregung von SPPs (perioische Strutur) Gittereinopplung Woo s anoaly

21 Terahert un Plasoni TH spectral range: 100 GH < < 10 TH 3 < < 30 µ TH plasonics Sub wavelength holes Propagation on surfaces an wires Structure eia perioic/rano T. W. Ebbesen et al.,nature 391, 667 (1998) Agrawal et al., New Journal of Physics 7 49 (005) G. Torosyan et al., APL 85, 337 (004) Abul K. Aa et al., Appl. Phys. Lett. 86, (005) Wang & Mittlean, NATURE, VOL 43, 376 (004) K. J. Chau et al., PRL 94, (005)