Laser frequency stabilization based on an universal sub-Doppler NICE-OHMS instrumentation for the potential application in atmospheric Lidar

Abstract

Abstract. Lidar is an effective tool for high altitude atmospheric measurement in which a weak absorption line for the target gas is selected to ensure a large optical depth. The laser frequency stabilization to the line center is required and a sub-Doppler (sD) spectroscopy of the target line is preferred as a frequency reference. In this paper, a novel universal sD NICE-OHMS instrumentation based on a fiber coupled optical single-sideband electro-optic-modulator (f-SSM) for the potential application in atmospheric Lidar is reported. The f-SSM can replace all frequency actuators in the system, so as to eliminate the individual design of feedback servos that often are tailored for each laser. The universality of the instrumentation was demonstrated by the alternative use of either an Er-doped fiber laser or a whispering gallery mode laser. Then the instruments based on both lasers were used to produce the sD signals of acetylene which worked as a frequency reference to stabilize the laser. By performing the lockings, relative frequency stabilizations of 8.3 × 10−13 and 7.5 × 10−13 at integration time of 240 s were demonstrated.

Absolute frequency metrology of buffer-gas-cooled molecular spectra at 1 kHz accuracy level

“…At the same time, our novel approach still has ample room for improvement, laying the groundwork for approaching the 10 −13 accuracy range. Relevant upgrades could include the prestabilization of the probe laser against an ultra-low-expansion (ULE) reference cavity, as well as the implementation of even more sophisticated spectroscopic techniques, such as 2-photon cavity-ring-down spectroscopy 54 or noise-immune cavity-enhanced opticalheterodyne molecular spectroscopy (NICE-OHMS) 2,55,56 . Accordingly, the Rb-GPS standard should be replaced with the clock laser delivered from Istituto Nazionale di Ricerca Metrologica (INRIM) through the National Optical Fiber Link (already fully operational in our lab and routinely referenced to the primary Cs fountain 57 ).…”