An optical instrument is provided for simultaneously illuminating two or more spaced-apart reaction regions with excitation beams generated by a light source. The light source can include an area light array of light emitting diodes, one or more solid state lasers, one or more micro-wire lasers, or a combination thereof. According to various embodiments, a Fresnel lens can be disposed along a beam bath between the light source and the reaction regions. Methods of analysis using the optical instrument are also provided.