The ac Stark effect in nitric oxide induced by rapidly swept continuous wave quantum cascade lasers

A large ac Stark effect has been observed when nitric oxide, at low pressure in a long optical path (100 m) Herriot cell, is subjected to infrared radiation from a rapidly swept, continuous wave infrared quantum cascade laser. As the frequency sweep rate of the laser is increased, an emission signal induced by rapid passage occurs after the laser frequency has passed through the resonance of 1-0 R(11.5)(3/2 /)molecular absorption line. At very high sweep rates a laser field-induced splitting of the absorptive part of the signal is observed, due to the ac Stark effect. This splitting is related to the Autler-Townes mixing of the e, f lambda doublet components of the 1-0 R(11.5)(3/2) transition, which lie under the Doppler broadened envelope.