Half a century after its birth, lasers are present in many life applications that are being reinvented by scientists.
In the 1950s, as physicists raced to invent the first laser, they discovered rules of quantum mechanics that limited the purity of the color of light. Since then, lasers have always been built with these limitations in mind.
However, new research from physicists Wiseman and Pekker shows that the true nature of lasers is very different from what was previously understood.
In essence, the laser is like a speaker that emits light. The “laser” itself was originally an acronym for “Light Amplification by Stimulated Emission of Radiation”.
Specifically, light photons will radiate in different directions from an atom and collide with other atoms, excite electrons in these atoms to fall further, generating more photons of the same frequency, same phase and same phase. direction of flight, creating a chain reaction that amplifies the flow of light.
Laser light is in contrast to most other light sources, such as reading lamps or the Sun, which emit randomly scattered photons.
In essence, the laser is like a speaker that emits light. (Photo: Gizmodo).
The longer the photons stay in sync, the more monochromatic the light. The color of the light source corresponds to the wavelength of the photons. For example, with green light, the wavelength ranges between 500-550 nanometers. In order for multiple photons to remain in sync for long periods of time, their wavelengths must be aligned, that is, the photons should be as close to a single color as possible.
Synchronization of photons in a laser has many benefits, one of which is for the manufacture of optical clocks.
But the photons gradually lose synchronization after leaving the laser beam. In 1958, physicists Arthur Schawlow and Charles Townes estimated the maximum time period for synchronization to be known as the Schawlow-Townes limit.
However, the new findings indicate that Schawlow-Townes is not the final limit. ” In principle, it is possible to make lasers with significantly more coherent photon beams,” said physicist David Pekker from the University of Pittsburgh.
This is because Schawlow and Townes treat the laser as an empty box in which photons multiply and leave at a speed proportional to light inside the box. In other words, the photon escaping from the laser beam, according to Schawlow and Townes, is like water flowing out of a hole in a barrel. Water flows faster when the bucket is full and vice versa.
Stimulated emission is the process by which an atom’s electrons in an excited state interact with electromagnetic waves of a certain frequency, which can release energy into the electromagnetic field and jump to a lower energy level. (Image: Wikipedia).
However, physicists Wiseman and Pekker discovered that if a valve that controls the photon flow rate is placed in the laser beam, it is possible to produce a laser with photons that stay attached for much longer than the Schawlow-Townes limit.
“In this way, we have found the ultimate limit, a real physical limit dictated by quantum mechanics. This work subverts 60 years of understanding the limits of lasers,” said physicist Howard Wiseman from Griffith University, Australia.
This discovery improves monochromatic lasers for applications such as quantum computing. However, the laser “rebirth” is expected to take years of work.
According to physicist Steven Touzard of the National University of Singapore, Pekker and Wiseman’s work may not directly generate commercial lasers, because laser manufacturers often don’t rely on the Schawlow-Townes limit. Overcoming this limitation is more theoretical than technical progress.
The new study also goes against conventional wisdom about lasers. It does not produce light through stimulated emission – the type of interaction between light and matter in which a photon strikes an atom emitting an identical photon.
Therefore, if based on the above laser naming, the new laser will no longer have the letters “s” and “e”.