TUNABLE CARBON-MONOXIDE OVERTONE LASER SIDE-BAND SYSTEM FOR PRECISIONSPECTROSCOPY FROM 2.6 TO 4.1 MU-M

We report a source of tunable laser radiation for high-precision molec ular spectroscopy in the 2.6-4.1-mu m spectral region. Laser Light fro m a CO overtone laser is mixed with microwaves, generating tunable sid ebands of similar to 1 mW of power. We achieve very high absolute freq uency accuracy by frequency-offset locking the CO laser to a CO2 laser secondary frequency standard. The uncertainty of the laser frequency is less than 30 kHz (Delta nu/nu = 3 X 10(-10)), and the laser linewid th is of the order of 100 kHz. This tunable and ultrastable laser syst em is suitable for very accurate molecular spectroscopy and metrology in a most interesting wavelength region. We demonstrate an application of the system to saturated-absorption spectroscopy of a rovibrational transition of carbonyl sulfide. (C) 1998 Optical Society of America.