In the laser museum where physics tells its story

Let us explore this evocative place through the account of Rinaldo Cubeddu, Head of the Department of Physics twice, from 1993 to 1998 and from 2006 to 2012, and today Professor Emeritus. Founder of the research line “Photonics for Health, Agrifood and Cultural Heritage”, his activity focused on Biophotonics, where he was among the first to propose and use innovative laser systems operating in the time domain in the picosecond and femtosecond regime.

The history of the Historical Museum of the Department of Physics begins in the 1980s, when scientific instruments dating back to the first half of the 20th century were found in the basement under the Department’s stepped lecture hall. Those instruments were collected and moved to the Department’s cellars.

The recovery of this heritage took shape in the 1990s, precisely during Cubeddu’s tenure as Head of Department.

These are laboratory and teaching instruments, made mostly of brass, spanning various fields of physics: from mechanics to acoustics, from electromagnetism to optics.

The discovery of the Department’s inventory book made it possible to trace the name of each instrument through its inventory number. At that point, several fourth- and fifth-year students from the degree programmes in Electrical Engineering and Nuclear Engineering, then the ones closest to physics subjects, took care of cleaning the artefacts and drafting a brief historical-functional note for each of them.

To display them, three large period wooden cabinets with glass fronts were recovered and restored; inside them, the instruments are arranged by discipline and accompanied by an explanatory note. The larger ones, on the other hand, are presented individually.

Also in the 1990s, on the initiative of Orazio Svelto, who at the Politecnico had founded one of the first laser research groups in Italy in the 1960s, the Laser Museum was also established, dedicated to the memory of Carlo Alberto Sacchi.

Along a corridor on the Department’s ground floor, some display cases house the first prototypes of solid-state, picosecond and nitrogen lasers made in Italy by the Department of Physics.

Then, thanks to collaboration with researchers from the C.I.S.E. Laboratories in Milan, the C.S.E.L.T. Research Laboratories in Turin and Italtel in Milan, the exhibition route expanded further: the first prototypes of gas and semiconductor lasers made in Italy were also located and displayed, with the aim of offering a broader overview of the early development of lasers in our country.

The informational panels in the museum recount both the current applications of the different types of lasers and the first pioneering applications developed at the Politecnico, particularly in the field of short femtosecond laser pulses and the use of lasers in biomedicine.

More recently, the museum was also at the centre of the thesis “Experiment. Stories of Engineering Physics from Politecnico di Milano”, prepared by Gabriele Valenzani and Giulia Valle. Supervised in the Department by Professor Cubeddu, the two students patiently catalogued the instruments in the Historical Museum and produced a volume with images, descriptive sheets and features, organised by categories to make consultation easier.

In recent years, the museum has also been enriched with a new exhibition area, located near the laboratories where ultrashort laser pulses are produced, with durations ranging from a few femtoseconds (10⁻¹⁵ s) to some tens of attoseconds (10⁻¹⁸ s).

At the heart of this section is the first commercial prototype of an amplified titanium-sapphire laser system, capable of generating high-energy pulses lasting a few tens of femtoseconds. The system is based on the chirped pulse amplification (CPA) technique, invented in 1985 by Gerard Mourou and Donna Strickland, a breakthrough that revolutionised ultrafast optics and earned the two scholars the Nobel Prize in 2018.

Today, CPA makes it possible to obtain laser pulses with peak powers on the order of several petawatts (10¹⁵ watts). Above all, however, it opened the way to attosecond science, which studies the ultrafast motions of electrons. A field awarded the Nobel Prize in Physics in 2023, given to Pierre Agostini, Ferenc Krausz and Anne L’Huillier.