"NANO-ACOUSTICS AND TERAHERTZ ACOUSTICS" UNIVERSITE Pierre & Marie CURIE La science à PARIS "NANO-ACOUSTICS AND TERAHERTZ ACOUSTICS" Bernard Perrin International Workshop on « Nanoscale Energy Conversion and Information Processing Devices » - September 24-26, 2006, Nice - France - 

Sound wave velocity in solids 5 – 10 nm/ps Probing vibrations at the nanoscale LA TA Fréquency n (THz) 10 1,0 10-3 10-4 10-2 10-1 10-5 piezo Brillouin Picosecond acoustics IXS Wavevector q/p (u.a.) nano-systems neutron Phonons : nm scale THz range Ballistic phonon heat transport Picosecond acoustics (H. Maris, 1985) What can be done with an optical pump probe technique to increase the frequency range of laser ultrasonics? Phonon engineering Phonon nanocavities

Nanometric sonar in thin films probe pump Lsubstrate > a few hundreds mm Lfilm > a few tens nm substrate reflectometry interferometry Nanometric sonar in thin films

Distorsion over large distance propagation ( > 0.1 mm) Lattice dispersion Lattice anharmonocity

Dispersion and nonlinearity : Solitons (MgO) Stable solution (soliton) 150 fs (1.4nm)

Multi-soliton formation Rectangular initial strain Area conservation

Acoustic Nonlinearity - Acoustic rectification - Harmonic distorsion - sound velocity = f() - Acoustic rectification GaAs pump probe Al-30 nm 356 m [100]

Expérience de réflectométrie en fonction de la puissance d'excitation

Expérience de réflectométrie en fonction de la puissance d'excitation

Expérience de réflectométrie en fonction de la puissance d'excitation

Expérience de réflectométrie en fonction de la puissance d'excitation

Expérience de réflectométrie en fonction de la puissance d'excitation

Expérience de réflectométrie en fonction de la puissance d'excitation

Expérience de réflectométrie en fonction de la puissance d'excitation

Ballistic propagation of heat pulses Q Black body radiation Spectrum up to a few THz Z-cut in Sapphire - T = 3.8 K time longitudinal phonons tranverse phonons

GaAs/AlAs

Can we do the same with a pump probe technique? First longitudinal coherent acoustic echo (one way trip) T = 15 K GaAs pump probe Al-30 nm 356 m [100] reflectometry One way + 6 round trips 2 round trips interferometry

Temperature dependence Q = 0.12 nJ

XY scan in the detection surface 12 K - Q=0.6 nJ m) m Position ( pump Al 30 nm probe at different locations XY scan in the detection surface 30 60 1 3 13 200 400 600 800 1000 1200 1400 Position ( m m) Delay (ps) 12 K - Q=0.6 nJ Heat pulse : moving acoustic source vph. vst. vstvph : building up of a large matter displacement

Phonon engineering and acoustic nanocavity

Acoustic mirror Acoustic nanocavity

Nanocavity used as a phonons generator GaAs 356 µm pump probe Nanocavity used as a phonons generator cavity

Selective excitation of the cavity mode

Nanocavity or mirror used as a phonon detector GaAs probe pump Nanocavity or mirror used as a phonon detector 356 µm Acoustic mirror

Laurent Belliard – INSP Alex Fainstein – Institut Balseiro (Bariloche) Phonon engineering in the subterahertz range is possible Semiconductor superlattices work as excellent acoustic Bragg mirrors Acoustic nanocavity has been evidenced A first step towards a SASER Laurent Belliard – INSP Alex Fainstein – Institut Balseiro (Bariloche) Agnès Huynh - INSP Bernard Jusserand - INSP Daniel Kimura- Lanzillotti (INSP/Institut Balseiro - Bariloche) Aristide Lemaitre (LPN – Marcoussis) Emmannuel Péronne - INSP Shuo Zhang - INSP

12th international conference Phonons in nanostructures and low-dimensional structures Ultrafast acoustics Coherent phonons Micro and nano acoustics MEMS and NEMS (micro and nano electromechanical systems) Phonons in devices for electronics, optoelectronics and spintronics Electron-phonon interaction Micro and nanoscale phonon heat transfer Nanoscale energy conversion and thermo-electricity Phonon transport Solitons and nonlinear phenomena Acoustic waves in anisotropic media and phonon imaging Phonons in superconductors and magnetic materials Phononic crystals Surface and Interface phonons Quantum fluids Lattice dynamics Phonons in glasses and disordered systems Phase transitions Light, neutron and X-ray inelastic scattering New techniques Particle detectors July 15–20, 2007 12th international conference on phonon scattering in condensed matter