PROF. ALZETTA WORK IN CAGLIARI (2006-2008) G. Pegna, Physics Dept., University of Cagliari [email protected].

PROF. ALZETTA WORK

IN CAGLIARI (2006-2008)

G. Pegna, Physics Dept., University of Cagliari

[email protected]

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?