prof. alzetta work in cagliari (2006-2008) g. pegna, physics dept., university of cagliari...
TRANSCRIPT
PROF. ALZETTA WORK
IN CAGLIARI (2006-2008)
G. Pegna, Physics Dept., University of Cagliari
Chapter 1: Rubidium
The Physics Dept.
THE CAGLIARI PHYSICS DEPT. (in a very rare misty day!)
The birth of our collaboration:
my presentation at the S.I.F. 2006 Congress of a tabletop apparatus
for the determinationof c in free propagation
The working principle
The apparatus: the measuring base is only 60 cm.
Prof. Alzetta proposed using the same principle to detect the extreme refraction index changes in the neighbours of the “dark line” of Rubidium at
3 GHz
So a completely new quantum optics
laboratory was quickly set up.
and the laboratory in Jan. 2008
The historic 1976 set-up by which the“dark line” was discovered. Note the same Helmoltz coils
A test apparatus working at 3 GHz: here and n are measured
Bal. MixerAmplifier
Bias teePhotodiode
Laser
Phase Regulat.
d.c. out
July 2007: technical achievements:
•Laser diode temperature stability better than 1 mK: /T1225
MHz/mK
•Injection current stabilized at nA level
•Effective protection of the Laser against destruction causes
In normal work: Laser diode wavelength not locked to an
atomic transition.
Laser diode mount
3 GHz coupling transformer
Heathing resistors
Thermocoupleand thermistorleads
Modul. signal cables
Thermalinsulator
LASER MODULATION AT 3.5 GHz
Photo of the display of the spectrum analyzer HP 141.
3.5 GHz signal from the fast photodiode (tr=35 ps)
The Laser head circuit.
The whole circuit is thermosta-tized
The PID controller schematicsIt was designed for minimum d.c.
path between input and output
Laser stability check: optical beats
between two beams at =3036 MHz
•Spectrum analyzer scan: 200 MHz/div
•Scan speed: 1 ms•Photographic camera shutter speed: 125
ms
The “Dark Line”on the D1 line of 85Rb and the corresponding refractive index
variation by the technique at 3036 MHz(G. Alzetta and G. Pegna, Nov. 2007)
Transparence signal FWHM 30 KHz
signal 0.8 < n < 2.4
The ramp signal is the 0,8 MHz sweep around the 3036 MHzlaser modulation
Some observed phenomena:
In a dual frequency magnetic resonance experiment in an inomogeneous M.F. (Alzetta-Gozzini-Moi-Orriolis technique, 1976), the bright spot becomes dark by
changing the laser tuning towards the extreme long wavelengths. Why?
VBright spot
VDark spot
Fluorescence
traceinto the cell
Fluorescence signals, mean of 64 acquisitions
KHz CPT in non degenerate Zeeman sublevels of ground
state?• Laser beam in the z direction• Magnetic field in the x direction, swept at 5 Hz• Laser injection current modulated at 500 KHz• Amplitude of injection signal regulated for maximum of fluorescence: strongly enhanced• Laser tuned on either of the two peaks of
fluorescence
And also experiments that failed!
Prof. Alzetta proposed to prepare the CPT by means of two Lasers,
tuned respectively to the F=2 and F=3 transitions of the gound state
of the D1 line of 85Rb.
The failure was probably due to the inadequate stability of the Lasers.
Chapter 2: Tartini
Antique problem: the Tartini sound has real physical existence, or is an artifact
of our perceptive sistem?
Prof Ascoli has spoken on his work carried out with Prof. Alzetta
in Pisa on this question
The original idea introduced by Prof. Alzetta was to create the Tartini sound using ultrasounds. In this way its aural perception would
be neat and its instrumental capture unaffected by the strong
superimposed signals
Here is the work carried out in Cagliari: the “Tartini” set-up
8 powerfultweeters
The sistem working at 13 KHz
Tartini-Third sound Music 1
Tartini-Third sound Music 2
Tartini-Third sound
Happy birthday, Prof. Alzetta!
And hearty wishes of many more years of good ideas
and of valuable work
The end
When two strong sounds of different heights are played, our brain perceives
a third note whose frequency is the difference between the frequencies
of the two sounds. This is the THIRD SOUND, or the
TARTINI SOUND.
Old problem: the Tartini sound has real physical existence, or is an artifact
of our perceptive sistem?