Laser linewidth measurement using beat-note technique

Abstract

Lasers play a crucial role in quantum and atomic physics experiments. To prepare atoms in a desired quantum state, these lasers must possess specific properties, including tunability and a narrow spectral linewidth. In this study, we construct and employ an external cavity diode laser to prepare cold rubidium atoms. We control the laser’s stability using an electronic system and evaluate its performance by measuring the spectral linewidth through the beat signal technique. The measurement indicates a linewidth narrower than 1 MHz, which makes the laser suitable for subsequent experiments. Finally, we adjust the laser frequency to match the rubidium transition frequency between states 5S 1/2, F = 2 ↔ 5P 3/2, F′ = 2, and successfully utilizing the laser to prepare cold rubidium atoms in a magneto-optical trap.