Nonlinear spectroscopy with a vertical-cavity surface-emitting laser (VCSEL)

We have evaluated the suitability of a vertical-cavity surface-emitting las er diode (VCSEL) for spectroscopic applications. Despite its low output pow er it is possible to observe narrow resonances in a saturated absorption sp ectroscopy experiment on the cesium D-2 transition at 852 nm, limited in wi dth by the laser linewidth of several tens of MHz. High modulation efficien cy of the VCSEL allows us to create modulation sidebands at 9.2 GHz frequen cy via direct modulation of the laser injection current. Using the carrier and either one of the sidebands coherent population trapping (CPT) resonanc es in a buffered cesium Vapor can be prepared with linewidths below 130 Hz. With this very compact setup we have studied the dependence of CPT resonan ce position and linewidth as a function of optical detuning and find eviden ce of the influence of the excited state hyperfine structure.