Coherent multiwave heterodyne frequency measurement of a far-infared laser by means of a femtosecond laser comb.
We demonstrate the possibility of using a femtosecond laser to measure with high accuracy the frequency of a far-infrared (FIR) monochromatic source, such as an optically pumped molecular laser, by generating in a suitable mixer a signal in the radio-frequency region at the frequency difference between n steps of a femtosecond comb and the FIR source. All the couples of modes lying a distance of n steps from one another contribute coherently to the heterodyne signal. The technique has been tested up to 670 GHz.
Beverini
N
N
Dipartimento di Fisica Enrico Fermi dell'Università di Pisa and Istituto Nazionale per la Fisica della Materia, Via F. Buonarroti 2, 56127 Pisa, Italy.
Carelli
G
G
De Michele
A
A
Maccioni
E
E
Nyushkov
B
B
Sorrentino
F
F
Moretti
A
A