"In this thesis we describe an optical, non-interferometric technique that allows characterizing high quality optical samples by measuring their main parameters: the refractive index and the geometrical thickness. Our technique is based on characterizing a probe Gaussian beam transmitted through the sample under test. As the results of the measurements rely on tracking the referred parameters, we have devised a homodyne knifeedge detector to perform the measurements with the required accuracy. In this manner we characterize a thin pellicle consisting of a commercially available stretch film, obtaining a good agreement with the reported values of the manufacturer. The relevance of our measurements relies on the difficulty to determine the refractive index and the geometrical thickness simultaneously by means of other techniques as it will be described in the introduction section. This is because the pellicle under test is very thin and it can easily suffer mechanical deformation or heating damage. As a consequence, a non-invasive low power technique is required. Besides, the center of the pellicle is vibrating constantly and if interferometric techniques are used, erroneous measurements would be obtained. Once we accurately characterized the thin pellicle, we realized that a similar approach could be applied for characterizing optical plates. Even when there are a variety of techniques used to determine the refractive index and geometrical thickness of these plates, typically it is necessary to combine two techniques to determine them. In addition, focusing techniques which are commonly used are based on focusing a probe beam on the front and back surfaces of the plate. This is suitable for samples around one millimeter or more. However, when the plate is thinner than 200 microns it becomes difficult to discern the focusing at the surfaces thus obtaining misleading readings. To alleviate the difficulties mentioned above, our proposal performs the measurements in a non-interferometric way and does not need to be combined with any other technique which makes it suitable for the intended characterization. In this manner it was possible to characterize a high quality optical plate consisting of a cover glass."