REVTeX will automatically number sections, equations, figure captions, and tables. In order to reference them in text, use the label and ref commands.
The label command appears following a section heading or within a equation, figure caption, or table; the ref command appears in text where citation is to occur. We will refer to the first figure (Fig. 1) here. We can refer to the ``late figure'' also (Fig. 2).
References to figures: Fig. 1, Fig. 2 and Fig. 3.
References to tables: Table 1, Table 2, Table 3, and Table 4. OSA style requires that the initial citation of figures or tables be in numerical order in text, so don't cite Fig. 3 until you've cited Fig. 2. See Style and Notation Guide.