A team of Pitt physicists recently published a design that would surpass a theoretical limit on the effectiveness of lasers that’s barely changed in more than 60 years, opening new potential applications and maybe even necessitating a name change for the technology.
Ideally, a laser would maintain a pure color no matter how long it shines, a property that physicists refer to as coherence. “If a laser is coherent, that’s like a really good clock,” explained Department of Physics & Astronomy Assistant Professor David Pekker in the Kenneth P. Dietrich College of Arts & Sciences. “But in real life, that’s not how lasers work.”
Instead, they drift. The frequency of light waves they emit, which influences how pure the beam’s color is, changes slightly over time. That’s because the amount of light bouncing around inside of a laser alters the color that the laser ultimately produces. The process is called stimulated emission, a phrase that makes up the S and E in the acronym LASER — and which the Pitt team’s design bypasses entirely.
What their design calls for is replacing components of a traditional laser to better control the flow of light, making use of the building blocks of quantum computers that have been developed over the last decade. “In quantum computers, you have qubits, these are basically like atoms in the laser, and you have cavities,” Pekker said. “So why not just try to build the laser out of quantum computer components?”
Their calculations show that the resulting microwave laser design would have a coherence far higher than the previously proposed limit, which has budged only once since 1958. The team, including researchers from the labs of Department of Physics & Astronomy faculty members Gurudev Dutt and Michael Hatridge, published their design in the journal Nature Communications last month.