Single Mode Frequency Combs

Single Mode Frequency Combs
Single Mode Frequency Combs

Metrology has revolutionized frequency combs, which are collections of distinct, evenly spaced spectral lines. In particular, extremely precise measurements of time and distance are made possible.

According to conventional thinking, it is necessary to link at least two wave modes of a system to create a frequency comb. However, Jana Ochs of the University of Konstanz in Germany and her colleagues have recently developed a comb that only needs one mode. This feature offers advantages such as a structure that is easy to modify and requires less electricity.

Light is often used to do this, although mechanical vibrations can also be used to create frequency combs. In this case, each spectral line corresponds to a separate vibrational frequency. These combs, called phononic combs, can be adjusted in place, unlike optical combs. So far they have been produced with a non-linear connection of two or more vibrational modes.

The nanomechanical resonator is a small vibrating device that Ochs and his colleagues use for their research. The only vibration mode available in this device is stimulated by an external driving force provided cyclically. This drive mode exhibits extremely non-linear low frequency oscillations in both amplitude and phase. When these oscillations change the vibration of the device, a phononic comb is formed.

The scientists discovered that they could change the number and spacing of the comb's spectral lines by varying the frequency and strength of the repulsive force. According to them, their research reveals a new technique for creating frequency combs and sheds light on their nature. The team emphasizes that more research is needed to fully understand how this process works.

Source: physics.aps.org/articles/v15/s159

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