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Scientific Report 2007-2009
Laboratories and Facilities of the Department of Physics
L14. Laboratory for Ultrafast Spectroscopy
The laboratory for Ultrafast Spectroscopy, inaugurated in March 2009, is a newcomer among the experimental facilities
of the Physics Department. Built up from scratch thanks to an ERC-IDEAS Starting Grant project, the lab is powered by
an ultrafast 80 Mhz Ti:Sa oscillator (Coherent MICRA) and a regenerative amplifier able to deliver 800nm, 1Khz pulses
with dual option for 35 fs and 120 fs duration (Coherent LEGEND). The lab is currently involved in two main experimental
activities based on Pump&Probe protocol applied in different time domains:
Femtosecond Stimulated Raman Scattering We study photoinduced
effects in molecular and supra molecular structures such as
isomerization reactions, ligand dynamics in proteins, vibrational
energy redistribution. The system is pumped in an out of equilibrium
state by an ultrashort tunable laser pulse produced with an
Optical Parametric Amplifier (pump), and the wavepacket evolution
is probed at variable time delays tracking ultrafast dynamics
by means of Stimulated Raman Scattering. A combination of a
narrowband, highly tunable (330 ÷ 520 nm and 790÷810 nm)
pulse and a ultrashort white light continuum allows broadband
stimulated Raman scattering resulting in a probe with sub ps
time resolution and few wavenumbers frequency resolution.
Picosecond acoustics We study acoustic properties (sound
propagation) in disordered materials in the 10 ÷ 100 picosecond
time domain (corresponding to 50-500 Ghz range), which is unaccessible
ordinary frequency domain techniques such as light and
neutrons/xrays scattering. The sample needs to be prepared as
a film ( 100 ÷ 1000 nm thickness) with a 10nm metallic coating
on a surface. An ultrashort 800nm pulse impinges in the metallic
Figure 1: Ultrafast Spectroscopy Laboratory
surface producing an impulsive thermal expansion launching a strain wave. A second broadband pulse (white light continuum)
is reflected by the metallic surface and by the moving acoustic wave, resulting into a time dependent modulated signal
with periodicity and damping related to sound velocity and attenuation.
http://femtoscopy.phys.uniroma1.it/
Related research activities: C28.
L15. Macroscopic Quantum Coherence Lab
The The Macroscopic Quantum Coherence (MQC) group aims to study the behaviour
of macroscopic systems at very low temperatures, where the thermal effects
are negligible, being dominated by quantum effects. In particular we study superconducting
non linear systems realized with Jopsephson junctions in various configurations
and topology. These systems are studied also in view of the realization of a Quantum
Computer made of superconducting qubits. The laboratory is equipped with a Leiden
Cryogenics He3-He4 dilution refrigerator, having a base temperature of 10mK and
200microW of power dissipation capability at 120 mK. The system is equipped with
36 low frequency filtered lines (dc-1 MHz) and very high frequency rigid coaxial lines
(30 GHz).
For the high frequency signals we use two CW signal generators Anritsu Mg3694A
10 MHz-40 GHz and HP 8673G 2-26GHZ. For low frequency signal generators
and the detection system we use low noise commercial equipments driven by lab
View custom designed virtual instruments. Devices pre-test are performed using
standard liquid helium immersion dewars and a Heliox He3 system with operating
temperature of 0,3K (at IFN- CNR lab in Rome). The devices are designed by the
low temperature group collaborating with the experiment (IFN-CNR) and realized in
the CNR nano-micro fabrication facility, or by external factories.
Figure 2: Picture of the lower part
of the dilution refrigerator.
http://www.roma1.infn.it/exp/webmqc/home.htm/
Related research activities: P33.
Sapienza Università di Roma 187 Dipartimento di Fisica