**1. Introduction**

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156 Quantum Optics and Laser Experiments

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Following a number of initial experiments in a magneto optical trap published by us in the period 2008-2009 (Olivares et al, 2008, 2009), there has been an increase in activity in the field. A brief review of the experimental methods can be found in (Olivares, 2007, 2008; Milonni, 2010). The physical details needed to obtain a cloud of cold atoms were described by Metcalf (1999). We will survey the literature and make a thorough discussion of the conditions that permit a stable cloud. We will outline our approach to the construction of the magneto optical trap. Our experiments are based on the construction described by Wieman et al. (1998) and Rapol et al. (2001). We followed the guidelines given in these articles but used state of the art equipment to obtain reliable results in our initial attempts to obtain a cloud of cold atoms. The only initial exception was a self made optical glass cell that was considered inexpensive. Subsequently, it was replaced by a more technically advanced cell that permitted us to improve the observational capability of the system. We will describe an experiment that proved the stability of the cloud and the optical method to vary the laser intensity of the pump and trap beams. We will study the influence of laser intensity imbalance on cloud formation and give values for the threshold intensity of each laser that supports cloud formation.
