kHz Linewidth Laser Characterization using Low Frequency and Excess Noise Measurements

Abstract

Low frequency noise (LFN) of highly coherent laser (linewidth below 10 kHz) is analyzed using an unbalanced Mach-Zehnder interferometer (UMZI) with adjustable long arm span. Furthermore, the Laser Relative Excess Noise (LREN) is introduced here to set a comparison of the laser coherence in relation to its emission power. The LREN is obtained using the addition of laser high and low frequency noises that appear in excess to the ideal power spectral density (PSD) Lorentzian distribution. Using this approach, it is possible to compare the tested laser in relation to an ideal laser with the same linewidth.