15min:
SUB-DOPPLER RESOLUTION SPECTROSCOPY OF THE FUNDAMENTAL BAND OF HCl WITH AN OPTICAL FREQUENCY COMB.

K. IWAKUNI AND M. ABE AND H. SASADA, Department of Physics, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.

We have demonstrated wavelength modulation spectroscopy of HCl using a difference-frequency-generation (DFG) source and an enhanced-cavity absorption cell. The frequency axis of the spectrum is calibrated by a fiber-based optical frequency comb which is locked to a Rb clock linked with TAI. The pump and signal sources of DFG are a 1.06-µm Nd:YAG laser and a 1.55-µm ECLD, and the idler wave is generated in a waveguide-type PPLN. The hyperfine structure caused by the Cl nucleus with the spin 3/2 is resolved for the R(0), R(1), and R(2) transitions in the fundamental vibration band. The hyperfine components of Delta F = +1, 0, -1, and the cross-over resonances are observed with a typical line width of about 220 kHz, and the transition frequencies are measured with an uncertainty of less than 10 kHz. The pressure- and power-dependences of the transition frequency and the spectral intensity of the cross-over resonances are also investigated.