1.1 INTRODUCTION1.2 LAGUERRE–GAUSSIAN BEAMS AND ORBITAL ANGULAR MOMENTUM1.3 BESSEL AND MATHIEU BEAMS1.4 GENERAL SOLUTION OF THE WAVE EQUATION1.5 CLASSICAL OR QUANTUM?1.6 CREATING LAGUERRE–GAUSSIAN BEAMS WITH LENSES AND HOLOGRAMS1.7 COHERENCE: SPATIAL AND TEMPORAL1.8 TRANSFORMATIONS BETWEEN BASIS SETS1.9 CONCLUSION