Role of noise in diode-laser spectroscopy of a spectral line profile

摘要

Problems of precise measurements of spectral line parameters by the technique of diode laser spectroscopy are considered. The instrumental function of a diode laser with a distributed feedback (λ = 1.53 μm), which consists of the additive contribution from spontaneous emission noise and fluctuations of frequency and intensity is studied. The analytic expression is obtained for the lasing spectrum of a diode laser caused by frequency fluctuations. The spectral density of the diode laser frequency fluctuations g{sub}0, which determines the width of the central part of the diode laser emission line, was obtained by two independent methods (from Doppler-broadened absorption line fitting and from the intensity of residual radiation and the linewidth of the saturated absorption line). Parameters of the spectral density of the diode laser frequency fluctuations Ω and Γ, which are related to relaxation oscillations and govern the diode laser emission line wing, are determined experimentally. The spectral line profile was correctly reconstructed by the deconvolution of the instrumental function of the diode laser from the detected transmission line profile. The role of correlations between the intensity and the frequency noises of a diode laser is discussed.