Scientists have just set a new record for building the sharpest laser in the world, with a linewidth of just 10 millihertz.
Linewidth is a measurement of how much of the optical spectrum the laser covers. We haven¡¯t yet reached the ideal measure, that of a laser on just one wavelength, but this milestone is a step in the right direction toward a single-frequency laser.
Researchers from the National Metrology Institute in Germany (PTB) say the sharper laser has many practical applications, one of which is more accurate clocks.
¡°The smaller the linewidth of the laser, the more accurate the measurement of the atom's frequency in an optical clock,¡± explains physicist Thomas Legero, one of the research team members. ¡°This new laser will enable us to decisively improve the quality of our clocks.¡±
After close to a decade of work, the scientists made the breakthrough thanks to what¡¯s called a Fabry-P¨¦rot silicon resonator, a device that uses two fixed mirrors placed opposite each other and inside a double cone to control the light¡¯s wavelength.
The researchers say the world¡¯s sharpest laser is stable for about 11 seconds at a time before becoming asynchronous; enough time for it to travel to the Moon and back five times. In order for it to be applicable for deep space radio transmissions, that distance travelled needs to be much further, which means the team needs to make the laser even sharper, possibly down to 1 millihertz.
In the future, these lasers could also be used to test Einstein¡¯s Theory of Relativity.