Apparatus and methods for analyzing single molecule and performing nucleic acid sequencing. An integrated device includes multiple pixels with sample wells configured to receive a sample, which, when excited, emits radiation; at least one element for directing the emission radiation in a particular direction; and a light path along which the emission radiation travels from the sample well toward a sensor. The apparatus also includes an instrument that interfaces with the integrated device. Each sensor may detect emission radiation from a sample in a respective sample well. The instrument includes an excitation light source for exciting the sample in each sample well.