Stepping out of the sci-fi realm, lasers today boast a variety of real-world applications in fields as diverse as medicine, military, space exploration and even nanotechnology. To ensure better performance as well as precision, scientists around the world are continually looking for ways to enhance the power and sharpness of lasers. As part of a new project, a team of researchers has just developed the world’s sharpest laser with a linewidth of only around 10 millihertz (mHz).
Before we proceed, linewidth of a laser is basically the range of the emission spectrum (also known as optical spectrum) it covers. In other words, it refers to the total width of the emanated radiation’s frequency band. Recently achieved by a group of scientists at the National Metrology Institute of Germany, the breakthrough could potentially improve the accuracy of modern timekeeping devices. Thomas Legero, a member of the research team, explained:
The smaller the linewidth of the laser, the more accurate the measurement of the atom’s frequency in an optical clock. This new laser will enable us to decisively improve the quality of our clocks.
The result of ten long years of research, the impressive feat was made possible with the help of a special contraption called Fabry-Pérot resonator. Invented back in 1899, the device features two mirrors situated parallel to one another inside a fixed double cone, and is commonly used to measure wavelengths of light. According to the team, a laser’s linewidth actually depends on the distance between the two reflecting surfaces as well as their stability.
To construct the world’s sharpest laser, the scientists had to ensure the mirrors were completely stable, despite changes in pressure and temperature and vibrations related to seismic waves and ambient sounds. In order to eliminate the effects of Brownian motion, the kind of involuntary movement that atoms exhibit in a fluid, the researchers rebuilt the resonator using single-crystal silicon and, then reduced its temperature to an optimal -150 degrees Celsius (approx. -238 degrees Fahrenheit).
Laboratory testing of the newly-created laser revealed light waves oscillating at staggering speeds of up to 200 trillion times per second for a total of 11 seconds, before losing their rhythm. The resultant wave train measured about 3.3 million kilometers, which is nearly ten times the distance separating the moon from the Earth. For the time being, the team is working to further decrease the laser’s linewidth to just under 1 mHz. If that happens, the technology could revolutionize radio-based communications in deep space. In addition to greatly improving the accuracy of measuring electromagnetic radiation, the breakthrough could pave the way for more efficient optical atomic clocks.
The findings of the research were recently published in the Physical Review Letters journal.