The essential element for the generation of a light sheet is a cylindrical lens.
For small beam diameter and divergence lasers like as argon-ion lasers – one cylindrical lens can be sufficient to generate a light sheet of appropriate shape. For other light sources – like for example Nd:YAG lasers – a combination of different lenses is usually required in order to generate thin light sheets.
The both answers consider light sheet , parallel to the direction of light propagation. If you are interesting in a light sheet, which is normal to propagation direction, then short light pulse is a good case. For example, 100 fs light pulse is a sheet with thickness 0.03 mm.