Interaction of atoms and few cycle pulses in frequency and time domain SFB 407 network-meeting Les Houches Feb. 2009 Anne Harth, Mathias Hoffmann, Niels Meiser, Stefan Rausch, Thomas Binhammer, Uwe Morgner Institute of Quantum Optics, Leibniz University of Hannover, Germany Les Houches 02. 02. 2009
Motivation Well known light-matter interaction in two-level systems typical approximations: Rotating Wave approximation (RWA) Slowly varying envelope approximation (SVEA) Today sub 5 fs pulses are available Only few optical cycles of the carrier wave under the envelope New effects and can we measure them? harth@iqo.uni-hannover.de 2
Outline Coherent light-matter interaction Bloch-equations and Rabi-Flopping Interaction of two level atomic system with ultra short pulses Carrier-Wave Rabi-Flopping (CWRF) Carrier Envelope Effects in the multi-photon ionization regime Laser system with broadband spectrum for measurements of such effects harth@iqo.uni-hannover.de 3
Coherent light-matter interaction light matter approximations: semi classical description two level atom linear polarized and monochromatic light dipole approximation Rotating wave approximation (RWA) without dissipative elements (T 1, T 2 >> T P ) Schrödinger equation harth@iqo.uni-hannover.de 4
Rabi-Flopping & Bloch-equations amplitudes of the states: harth@iqo.uni-hannover.de 5
Rabi-Flopping & Bloch-equations amplitudes of the states: Density matrix: Optical Bloch equations: (polarization) (polarization) (inversion) harth@iqo.uni-hannover.de 6
Pulse area and SIT pulse area: Also presents the Bloch sphere angle, so multiple of 2π describes a complete Rabi-Flop self-induced transparency (SIT): the shape of the excitation pulse is maintained harth@iqo.uni-hannover.de 7
Interaction of matter with few cycle pulses Self-induced transparency with coupled Maxwell-Bloch system without using the RWA and SVEA time evolution of the electric field population probability consistent with results obtained from RWA [Ziolkowski Phys. Rev. A 52, 3082 (1995)] harth@iqo.uni-hannover.de 8
Interaction of matter with few cycle pulses Self-induced transparency with coupled Maxwell-Bloch system without using the RWA and SVEA but coupled Maxwell-Bloch system Without RWA and SVEA we see null-field time derivative features [Ziolkowski Phys. Rev. A 52, 3082 (1995)] harth@iqo.uni-hannover.de 9
Carrier-Wave Rabi-Flopping (CWRF) What happens when larger input areas are injected......large enough so that the area under the individual carrier may themselves cause RF Area theorem: [Hughes Phys. Rev. Lett. 81, 3363 (1998)] harth@iqo.uni-hannover.de 10
Carrier-Wave Rabi-Flopping (CWRF) What happens when larger input areas are injected... Area theorem: w w w w w [Hughes Phys. Rev. Lett. 81, 3363 (1998)] harth@iqo.uni-hannover.de 11
Carrier-Wave Rabi-Flopping (CWRF) What happens when larger input areas are injected... Area theorem: breakdown of the area theorem w w w w w incomplete Rabi flops local CWRF [Hughes Phys. Rev. Lett. 81, 3363 (1998)] harth@iqo.uni-hannover.de 12
Carrier-Wave Rabi-Flopping (CWRF): Bloch picture RF CWRF Oscillation of the polarization is not harmonically in the CWRF Nonlinear Effects occur Inversion symmetry -> third harmonic generation Double peak structure around the third harmonic [Mücke et. al. Phys. Rev. Lett. 87, 057401 (2001)] harth@iqo.uni-hannover.de 13
Carrier-Wave Rabi-Flopping (CWRF): experiment Measurement in semiconductor GaAs till now no verification of CW sensitive effects in atomic structures Change of nonlinear effect due to different injected pulse area Double peak structure around the third harmonic was observed In good agreement with theoretical simulation New field: extreme nonlinear optics Experiments directly sensitive to the electric field! [Mücke et. al. Phys. Rev. Lett. 87, 057401 (2001)] harth@iqo.uni-hannover.de 14
Carrier-Envelope Envelope-Offset Phase (CEO-Phase) Measurement of the relative position of the CEO-Phase of mode locked laser oscillators Stabilization of repetition frequency and CEO frequency to a reference standard: Frequency Comb (FC) applications in frequency domain applications in time domain Tuning of CEO-Phase by dispersive elements f CEO Frequency harth@iqo.uni-hannover.de 15
CEO-Phase effects in the multi-photon ionization regime Efforts to measure absolute CEO-phase in atoms Population probability Solution of the time dependent Schrödinger equation CEO-phase depends of bound states in atoms Intensities in the multiphoton ionization regime [Nakajima Phys. Rev. Lett 96, 213001 (2006)] CEO-phase harth@iqo.uni-hannover.de 16
CEO-Phase effects in the Mulitphoton ionization Regime to understand the underlying physics -three level system -Second order time dependent perturbation theory anti-resonant term cross terms resonant term with RWA without RWA [Nakajima Phys. Rev. Lett 96, 213001 (2006)] harth@iqo.uni-hannover.de 17
CEO-Phase effects in the Mulitphoton ionization Regime to understand the underlying physics -three level system -Second order time dependent perturbation theory anti-resonant term cross terms with RWA resonant term without RWA [Nakajima Phys. Rev. Lett 96, 213001 (2006)] harth@iqo.uni-hannover.de 18
Energy forbidden transitions full quantized description: anti-resonant term cross terms resonant term These are energy forbidden transitions! But the contribution beyond RWA will become more visible with decreasing pulse duration t P estimation: @780 nm laser system with ultra short pulse duration!! harth@iqo.uni-hannover.de 19
Oscillator with a ultra short pulses Ultra short pulses broadband spectrum Pulse duration: Fourier-limited: 3.7 fs Pulse repetition-rate: ~ 80 MHz Average output power: ~ 100 mw Pulse energy: ~ 1.25 nj Maximum pulse peak power: ~ 340 kw 1.5 cycles @ 780 nm I=10 11 W/cm 2 [Rausch et. al. Optics Express, Vol. 16 9739, (2008)] harth@iqo.uni-hannover.de 20
Oscillator with a ultra short pulses These are the shortest pulses ever measured from a laser oscillator but > contribution beyond RWA are hard to measure and the spectrum is more than octave-spanning. measure the absolute CEO-phase using Quantum interference is possible harth@iqo.uni-hannover.de 21
Conclusion Short reminder: Bloch-equations and Rabi-Flopping (RF) Physics without the RWA and SVEA (Null-field time derivative features) Breakdown of the area theorem CWRF Carrier envelope effects in the multi-photon ionization regime Laser system with broadband spectrum for measurements of the absolute CEO-phase harth@iqo.uni-hannover.de 22
Thank you very much for your attention! contact: Anne Harth harth@iqo.uni-hannover.de Institute of Quantum Optics Leibniz Universität Hannover Welfengarten 1, D-30167 Hannover Germany harth@iqo.uni-hannover.de 23
Fortschrittsbalken Hinzufügen Präsentation starten um Button drücken zu können Falls dies nicht funktioniert die Makrosicherheitseinstellungen auf Mittel heruntersetzen und Powerpoint neu starten. harth@iqo.uni-hannover.de 24