New type of high-resolution spectroscopy with a diode laser

A phenomenon observed in a simple experiment with a diode laser is found to be a basis for powerful spectroscopy. In this spectroscopy, the laser frequency is neither scanned nor modulated. High-resolution spectra in a wide ratio-frequency range, such as Zeeman and hyperfine spectra in both of the ground and the excited states, are observed simultaneously by frequency analyzing the intensity fluctuation of the light transmitted through a sample cell. Demonstrating experiments are carried out with respect to the ${\mathit{D}}_1$ and ${\mathit{D}}_2$ lines of Cs and Rb atoms.