Observing Fast Molecular Dynamics with a Coherent Raman Oscillator

Transcription

1 FRISNO 13 - March 19, 2015 Observing Fas Molecular Dynamics wih a Coheren Raman Oscillaor Igal Aharonovich, Avi Pe er Physics Dep. and BINA cener for nanoechnology, Bar Ilan Universiy ISF

2 Unlocking he Bandwidh Resource of Ulra-Broadband Bi-phoons wih an Opical Homodyne Scheme Rafi Vered, Yaakov Shaked, Faina Shikerman, Michael Rosenbluh, Avi Pe er Physics Dep. and BINA cener for nanoechnology, Bar Ilan Universiy, EU-IRG, ISF

3 Ulrafas Measuremen of Time-Energy enangled Bi-phoons 7 milliseconds! Ampliude Phase Puriy Sum frequency Correlaion New J. Phys. 16, ~10 8 phoons/deecion-ime

4 Classical o Quanum Transiion The conras as a funcion of he aenuaion. 8 orders of magniude! Quanum regime Classical regime Phys. Rev. Le. 114,

5 Squeezed ligh Generaion vs Deecion Generaion non linear medium 2 Homodyne Deecion p dc Frequency Mixer IF LO How Things are Done in RF? RF Amplifier Sq. Same device! Coupler Sq. Frequency Mixer RF IF LO Specrum Analyzer LO

6 Opical Homodyne Bi-phoon Inerference Pump Specral Crysal #1 phase Crysal #2 DC Pump PRL 72, Herzog Zeilinger BS 1 BS 2 0 DC BANDWIDTH Lifs all limiaions of deecorbased homodyne!

7 Ulra-Broadband bi-phoons Zero Dispersion! Pump 880nm PPKTP 8 DC Specrum Specral Inensiy [a.u] Single cycle bi-phoons Angular Frequency THz

8 Inensiy [Arb] Quanum wo-phoon inerference Pump laser 880nm CCD camera 300 Crysal 1 Crysal 2 Pump power meer % 60% Freq. [THz] SFG efficiency = 60% 7ms inegraion ime on a simple CCD! New J. Phys. 16,

9 Wha is non-classical? Pump laser 880nm A B CCD camera Crysal 1 Crysal 2 A Pump power meer Measure of he wo-phoon puriy B SPEED! Full flux deeced

10 And wih FWM An equivalen Mach-Zehnder inerferomeer for Bi-phoons: Two Phoon BS Two Phoon BS

11 Classical-o-quanum ransiion Quanum regime Classical regime PRL 114,

12 Bi-phoon Generaion wih Imaginary Gain PRL 114,

13 Ouline Laser Oscillaion as he ideal opimizaion How can i help o measure fas vibraional dynamics: A coheren frequency comb amplifier of he Raman signal Simulaion concep Crossing hreshold simulaion resuls Coheren gain dynamics No a normal laser Ideal soluion for a gold problem in coheren conrol Can we do i? Oulook

14 Laser Oscillaion = Opimizaion In space Find he opimal spaial mode o focus hrough a urbid medium Naure Phoonics 7, In ime? Find he opimal field ha can dump a given arbirary wave-packe o a single predefined arge sae

15 Molecular poenial [cm -1 ] Vibraion Scheme Turning poin A Vibraional dynamics Turning poin B Excied - A 1 Σ u 5000 Pump Emission 0 Ground - X 1 Σ g v=38 v= Iner-nuclear disance R [A]

16 Measuring vibraion Sandard Pump-Probe Emission Tomography Ionizaion Probe Excied poenial Excied poenial Pump Pump Emission Ground poenial Ground poenial One elecron per molecule S/N limi! One Phoon per molecule

17 Coheren Raman Oscillaor Pump Emission Difference from CARS, SRS : 1. Excied sae real, no virual 2. Final sae unspecified OC Pump HR Mol. emission Mol. medium Pump comb Coheren Memory in he caviy ligh

18 Possible Realisic Configuraion Deecor Rel. Delay Mol. Cell Alkali hea pipe DFG Corr. OC ` Sa. Abs. HR Pump comb

19 Ieraive Calculaion of Caviy Field Caviy Field n Pump pulse Solve Schrödinger Eq. Microscopic emied field Macroscopic emied field Caviy Field n Sponaneous noise Loss, Decoherence, Dispersion

20 Calculaing he Emied Field / 4 1 =, c z P z c z E cc e e P eg v v i = e g R R R U T R U T R R i v v e N g N v v,, =,, e g * e g..,,,,, 4 =, 2 g 2 e e 2 g 2 0 h c e R R R dr U R R U T R U R z c z E i v v v N v Emission of a vibraing dipole: The dipole: dipole emission populaion inversion

21 Ieraive Calculaion of Caviy Field Caviy Field n Solve Schrödinger Eq. Microscopic emied field Pump pulse Micro o Macro: 1. Far field on-axis = Coheren sum 2. Spaial mode emission = Spaial mode pump 3. Number of molecules in focal volume 4. Back-propagaion o focus Macroscopic emied field Caviy Field n Sponaneous noise Loss, Decoherence, Dispersion

22 Simulaion Resuls I L i 2 am plificaion phase Near hreshold L i 2 seady sae K 2 seady sae High above hreshold K 2 seady sae Accum ula ed in ensi y [ Arb.] 41 Tim e 41.5 [ ps] a 23 Tim e 23.5 [ ps] d 25 Tim e 26.5 [ ps] g 8 Tim e 9.5 [ ps] j 1.0 excied excied arge excied arge exci ed ar ge Popula ions 0.5 arge b e h k 1.0 Targe Puri y 0.5 = 8 = 8 = 23 = 23 c f i l Tim e [ ps] Tim e [ ps] Tim e [ ps] Tim e [ ps]

23 Simulaion Resuls II Inra-Caviy Field Targe sae specrum Puriy! Mode compeiion!

24 Coheren Gain Dynamics 8 7 Gain Gain [%] Targe Excied Populaions Pulse No. Gain decreases well before sauraion?? Gain non-local in ime Coheren Emission!

25 Can we do i? Small signal gain Densiy=10 12 cm -3, 10nj pump Pump can be reused

26 Available coherence ime? T = o C Aom densiy = cm -3 Pressure < 1 Torr Primary decoherence Collisions wih background aoms Resonan collision broadening a-a = 2 GHz/Torr Non-resonan broadening m-a = MHz/Torr Coherence window > 100ps! Wha abou inhomogeneous broadening? Nearly cancels for Raman ransiions

27 Conclusions + Oulook Measuring vibraional dynamics is imporan Coheren amplificaion of sponaneous Raman in a caviy wih synchronous pumping Caviy = Coheren Memory New ype of oscillaor Coheren gain and coheren dynamics Auomaic soluion for coheren-conrol asks in ime Experimenal realizaion appears wihin reach We are building i now