PROF. ALZETTA WORK IN CAGLIARI ( ) G. Pegna, Physics Dept., University of Cagliari
Chapter 1: Rubidium
The Physics Dept.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 Congress of a tabletop apparatus for the determination of 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. Mixer Amplifier Bias tee Photodiode Laser Phase Regulat. d.c. out
July 2007: technical achievements: Laser diode temperature stability better than 1 mK: / T 12 25 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 Thermocouple and thermistor leads Modul. signal cables Thermal insulator
LASER MODULATION AT 3.5 GHz Photo of the display of the spectrum analyzer HP GHz signal from the fast photodiode (t r =35 ps)
The Laser head circuit. The whole circuit is thermosta- tized
The PID controller schematics It 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 85 Rb 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 MHz laser 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? V Bright spot V Dark spot Fluorescence trace into 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 85 Rb. 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 powerful tweeters
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?