TY - JOUR AU - Jun Ye AU - L.-S. Ma AU - John Hall AB - Using our cavity-enhanced frequency modulation technique, we obtained the saturated signal of the weakly absorbing gas C2HD for the P(5) line of the (ν2 + 3ν3) overtone band at 1.064 μm. An absorption sensitivity of 1.2 × 10−10 (1.8 × 10−12/cm) has been obtained. The absolute frequency of the line center is established (within ±2.6 kHz) with respect to a doubled Nd:YAG laser/I2 frequency reference. The short-term stability, limited by the available signal-to-noise ratio, currently is 1 × 10−11 at 1 s, improving to 5 × 10−13 at 1000 s. The measured pressure-broadening rate is 34.7(0.8) kHz/mTorr (260 ± 6.1 kHz/Pa). Selection of slow molecules gave a linewidth four times narrower than the room-temperature transit-time limit. © 1996 Optical Society of America BT - Optics Letters DA - 1996-07 DO - 10.1364/OL.21.001000 N2 - Using our cavity-enhanced frequency modulation technique, we obtained the saturated signal of the weakly absorbing gas C2HD for the P(5) line of the (ν2 + 3ν3) overtone band at 1.064 μm. An absorption sensitivity of 1.2 × 10−10 (1.8 × 10−12/cm) has been obtained. The absolute frequency of the line center is established (within ±2.6 kHz) with respect to a doubled Nd:YAG laser/I2 frequency reference. The short-term stability, limited by the available signal-to-noise ratio, currently is 1 × 10−11 at 1 s, improving to 5 × 10−13 at 1000 s. The measured pressure-broadening rate is 34.7(0.8) kHz/mTorr (260 ± 6.1 kHz/Pa). Selection of slow molecules gave a linewidth four times narrower than the room-temperature transit-time limit. © 1996 Optical Society of America PY - 1996 EP - 1000 T2 - Optics Letters TI - Sub-Doppler optical frequency reference at 1064 μm by means of ultrasensitive cavity-enhanced frequency modulation spectroscopy of a C_2HD overtone transition VL - 21 SN - 0146-9592 ER -