Frequency Comb

A frequency comb is a special type of laser source whose spectrum consists of a large number of evenly spaced, discrete frequencies, resembling the teeth of a comb.
It coherently links the radio-frequency domain (below ~100 GHz) with the optical frequency domain (above ~200 THz).
Unlike ordinary lasers that emit a single frequency, frequency combs emit many precisely spaced frequencies with extreme regularity.
They offer very high stability and precision, making them powerful measurement tools.
Used to compare unknown light frequencies with a stable reference with extraordinary accuracy.
Essential for calibrating atomic clocks and for measuring gravitational redshift (shifts in light due to gravity).
Applied in exoplanet detection by measuring tiny Doppler shifts in starlight.
Also used in high-speed and high-precision spectroscopy for studying matter and light interactions.