Light can have a special property called orbital angular momentum (OAM), which gives beams a twisted shape of the wavefront. Twisted beams carry a specific amount of angular momentum in the direction of propagation. This property opens possibilities for increasing amount of information we can send in both optical and quantum communication. It could also help us improve and expand the capabilities of some types of quantum technology. By changing a regular beam of light in a particular way, we can create beams with some unique features. In this work, emphasis is given on Laguerre-Gaussian (LG) modes, and their generation and detection. LG modes carry non-zero OAM and are characterized by two numbers: the radial mode index 𝑝 and the azimuthal mode index 𝑙, known as topological charge (TC). This thesis delves into exploring the use of spatial light modulators (SLM) for the modal detection of Laguerre-Gaussian (LG) beams. A critical challenge in utilizing LG beams is to accurately determine indices of the unknown LG beam, which constitutes the main topic of this thesis. As a major contribution, a new type of diffraction grating was designed, which offers effective modal detection of LG beams. Our approach showcases a robust method capable of simultaneously determining both mode indices of an LG mode. Theoretical and experimental results show a clear correlation of the radial and azimuthal mode indices with the intensity distribution in the far-field diffraction pattern.