Pump-probe experiments with ultra-short temporal resolution

Transcription

1 Pump-probe experiments with ultra-short temporal resolution PhD candidate: Ferrante Carino Advisor:Tullio Scopigno Università di Roma ƒla Sapienza 22 February 2012

2 1 Pump-probe experiments: generalities 2 3

3 Pump-probe experiments Schematic of typical pump-probe layout. Pulsed Source delay line Beam splitter Pump F/2 Sample Detector Probe SHG F

4 Pump-probe experiments Schematic of typical pump-probe layout. Pulsed Source delay line Beam splitter Pump F/2 Sample Detector Sub-picosecond pulse Probe SHG F

5 Pump-probe experiments Broadband pump-probe layout with single shot detection. Simultaneous detection of different wavelengths Pulsed Source delay line Beam splitter Pump F/2 Sample Fast ELN CCD Probe F WLG

6 Pump-probe experiments Broadband pump-probe layout with single shot detection. Simultaneous detection of different wavelengths Pulsed Source delay line Beam splitter Pump F/2 Sample Fast ELN CCD Probe F WLG

7 1 Pump-probe experiments: generalities 2 3 APPLIED PHYSICS LETTERS Articles published week of 3 JANUARY 2011 Volume 98 Number 1 E. Pontecorvo, C. Ferrante, M. Ferretti, M. Ortolani, D. Polli, G. Ruocco, G. Cerullo, and T. Scopigno APL 98, (2011)

8 Impulsive heating process An ultrashort IR pulse induces a propagating strain wave. An optically delayed visible pulse probes the acoustic properties.

9 Phase matching condition ω = 2V s q = 2 2πnVs λ 263 GHz, ν = 42 Ghz (n =1.47 v =6000 m/s)

10 Phase matching condition ω = 2V s q = 2 2πnVs λ 1375 GHz, ν = 219 Ghz (n =5.32 v =8500 m/s) Frequency enhancement by appropriate substrate choice

11 Interesting region for mesoscopic dynamics in disordered systems Phase matching condition ω = 2V s q = 2 2πnVs λ 1375 GHz, ν = 219 Ghz (n =5.32 v =8500 m/s) Frequency enhancement by appropriate substrate choice

12 1 Pump-probe experiments: generalities 2 3

13 Femtosecond stimulated raman scattering leads to different advantages over traditional time resolved raman scattering: Collinear signal generation (fluorescence rejection); Non linear gain; coherence movie

14 Femtosecond stimulated raman scattering leads to different advantages over traditional time resolved raman scattering: Collinear signal generation (fluorescence rejection); Non linear gain; BUT... coherence movie

15 Temporal resolution Spectral and temporal resolution are limited by Heisenberg uncertainly principle. Movie ν τ 15 ps cm 1

16 Temporal resolution Spectral and temporal resolution are limited by Heisenberg uncertainly principle. Movie ν τ 15 ps cm 1 Group of Jean-Louis Martin, May 2007

17 SRS τ L τ S Vibrational coherence impulsively generated by simultaneous presence of a broadband (ultra-short) white light pulse and a narrow band raman pump. Vibrational coherence exp (i(ω L ω S )t)

18 τ A τ L Vibrational coherence exp (i(ω L ω S )t) τ S An additional ultra-short pump pulse generating a photochemical process of interest introduces time resolution, with unrestricted time X energy resolution product: circumventing Heisenberg principle in an elegant manner.

19 experimental setup CPA Ti:Sa Laser 800 nm, 30 fs, 1 khz, 4 mj nm 540 nm

20 at work: Ultrafast ligand dynamics in heme-proteins

21 heme-proteins excitation pathways relevant time scales below 3 ps

22 results

23 results

24 Conclusion Summary of personal contribution during the first year: 1 hands on experience with ultrafast pulse generation/characterization, pump-probe layouts and theory of coherent vibrational spectroscopy; 2 active participation in setting up a low temperature broadband picosecond acoustic experiment in vitreous silica and germania (Appl. Phys. Lett. 98, (2011)); 3 started planning an experiment on heme-proteins: preliminary data on photolysed MbCO.