Low-frequency FM-noise-induced lineshape: a theoretical and experimental approach

Linewidth determination by self-heterodyne or self-homodyne methods may lead to mistaken interpretation, because these measurements often include significant broadening due to low-frequency FM noise. The effects of FM noise on these linewidth measurement schemes are investigated. An analytical formulation of the photocurrent autocorrelation function is given for different frequency noise signatures, the lineshape being extracted from numerical implementation. We apply these results to linewidth prediction for 850-nm commercial vertical-cavity surface-emitting lasers and get almost perfect agreement between the theoretical and the experimental approaches.