Quantum threshold of the sensitivity of an intracavity traveling-wave laser spectrometer

An experimental investigation was made of fluctuations of the spectral distribution of the intensity in the wide-band spectrum of a ring cw traveling-wave dye laser. Allowance for the averaging within the limits of the instrumental function of a spectrometer was made by analyzing the noise power spectra obtained for the recorded intensity distributions. A good agreement with the theory was observed. The threshold of detection of an intracavity spectrometer, denned in terms of the absorption coefficient, was found to be governed by the quantum nature of the radiation used in the spectrometer and amounted to ~ 3 X 10 ^– 17 cm ^– 1 when the accumulation time was 20 s.