Optical frequency metrology in the bending modes region

The lack of widely tunable single-mode lasers in the long-wavelength part of the mid-infrared region has hindered optical metrology of bending vibrational modes. Here, a continuous-wave nonlinear laser source with tunability from 12.1 to 14.8 mu m, coupled with a frequency comb, is used to measure bending modes frequencies of carbon dioxide and benzene with accuracy down to 30 kHz.