Vol. 112 (2007) ACTA PHYSICA POLONICA A No. 5 Proceedings of the International School and Conference on Optics and Optical Materials, ISCOM07, Belgrade, Serbia, September 3–7, 2007 High Resolution Spectroscopy of Cold, Trapped Atoms T.M. Brzozowski, M. Brzozowska, J. Zachorowski and W. Gawlik Marian Smoluchowski Institute of Physics, Jagiellonian University Reymonta 4, 30-059 Cracow, Poland Pump-probe spectroscopy of cold, trapped atoms is discussed with par- ticular attention to mechanisms specific for cold atoms and potential diag- nostics applications. The discussion is illustrated with experimental results obtained with 85 Rb atoms trapped in a magneto-optical trap. Most impor- tant applications are non-destructive, real-time velocimetry (thermometry) and analysis of optical lattice dynamics. PACS numbers: 32.80.Pj, 42.50.Vk, 42.65.–k 1. Introduction Cold atoms in atomic traps are attractive samples for many important ex- periments. One of few available methods for their diagnostics is laser spectroscopy. In this paper we present typical spectra obtained by nonlinear Raman pump-probe spectroscopy and discuss their main features and applications. In our experiment we use a standard vapor-loaded magneto-optical trap (MOT). In order to perform high resolution Raman spectroscopy one of the lasers serves as the master for injection seeding into the trapping, pump and probe lasers. Their frequency shifts are controlled by acousto-optic modulators (AOMs). The probe beam enters the cloud of cold atoms making a small angle θ with one of the trapping beams. After traversing the cloud, the probe beam is directed onto a pho- todiode which records the absorption spectrum as a function of the pump-probe detuning, δ = ω pr − ω. The example of the probe absorption is presented in Fig. 1a. The spectrum consists of a narrow, central resonance for pump-probe detuning δ ≈ 0 and two side-band resonances. Such a shape can be qualitatively understood in terms of a two-level dressed atom model [1] extended to include multilevel structure of rubidium states and inhomogeneities of the net optical field in the trap. The results of such modeling [2] are in a good agreement with the experimental signals. (783)