Frequency comb spectroscopy

In the late 1990s and early 2000s, optical frequency combs revolutionized frequency and time metrology, providing linkages that allowed accurate measurement of microwave and optical frequencies. It was for their contributions to optical frequency comb development that John Hall and Theodor Hänsch earned their share of the Nobel Prize in Physics in 2005. An optical frequency comb is a laser source generating a series of thousands/millions of evenly spaced narrow spectral lines exhibiting a perfect phase coherence. As the technology around frequency comb generation has matured, numerous other applications have been discovered.

This research activity focuses on the application of frequency combs to broadband and precision molecular spectroscopy following two complimentary experimental approaches: i) direct frequency comb spectroscopy, or broadband comb spectroscopy, where the optical frequency comb is used to directly excite or interrogate the spectroscopic sample; ii) comb-assisted precision spectroscopy where the comb is used as a frequency ruler and the spectroscopic interrogation is performed by a CW tunable probe laser.

Main research lines

  • Broadband direct-optical-frequency-comb spectroscopy and hyperspectral imaging for gas sensing
  • Comb-assisted precision molecular spectroscopy for fundamental physics and frequency metrology
  • Synthesis of novel frequency combs in the visible and infrared (near and middle) spectral regions for broadband spectroscopy and long-term calibration of high-resolution astronomical spectrographs

The above lines are also part of the research activity of the Physics Department of Politecnico di Milano.

Research Projects


Comb-assisted spectroscopy and fundamental constants. Absolute frequency metrology of the CHF3 at 8.6-μm ro-vibrational spectrum at 10-11 level

Experimental setup for CHF3 saturated absorption spectroscopy and absolute frequency measurements. A: optical attenuator; BS: beam splitter; D: diffuser; DAQ: data acquisition system; G: diffraction grating; L: lens; M: gold mirror; SM: spherical mirror; OI: optical isolator; P: polarizer; PD: photodetector; PID: proportional-integrative- derivative servo; PLL: phase-locked-loop servo; QWP: quarter waveplate.


People involved:

Gianluca Galzerano (group leader)

Paolo Laporta

Nicola Coluccelli

Alessio Gambetta

Dario Giannotti

Francesco Canella

Antonio Caruso (PhD)


Research units: