For measuring incredibly fast optical phenomena, something more than a good stopwatch is necessary. The Okinawa Institute of Science and Technology Graduate University have come up with a device for this. It is called an optical frequency comb.
Normal lasers contain a single frequency of light. But frequency combs have many frequencies, spaced equally in the frequency domain. This makes it resemble the teeth of a comb.
These are used as optical rulers to measure the quickly varying signals by interfering the ‘teeth’ of the combs with the signal being measured. This accordingly converts those signals into more tractable radio frequency signals.
The researchers have published a paper in the Optics Letters describing how they came up with the frequency comb in the visible spectrum. They employed a phenomenon called four-wave mixing using a device called micro-bubble resonator.
Transferring the operating wavelength of these devices to the visible realm has numerous advantages one of which is usage in CT scans. Presently optical frequency combs are produced using huge space-consuming femtosecond laser systems. In contrast, the proposed model is only microns in size; and it needs only a low-power laser to pump the device.
Content Source: https://www.sciencedaily.com/releases/2017/01/170130083224.htm