Frequency Noise Characterization of Diode Lasers for Vapor-Cell Clock Applications

The knowledge of the frequency noise spectrum of a diode laser is of interest in several high-resolution experiments. Specifically, in laser-pumped vapor-cell clocks, it is well-established that the laser frequency noise plays a role in affecting clock performances. It is then relevant to characterize the frequency noise of a diode laser since such measurements are rarely found in the literature and hardly ever provided by vendors. In this article, we describe a technique based on a frequency-to-voltage (f/V) converter that transforms the laser frequency fluctuations into voltage fluctuations. In this way, it is possible to characterize the laser frequency noise power spectral density (PSD) in a wide range of Fourier frequencies, as required in cell clock applications.