The emitting facet of the single-mode laser diode is typically 1-micron high and 3-5 microns wide. Its output beam is highly divergent in a so-called "fast-axis" direction perpendicular to the emitter and less so along the facet or "slow-axis". The collimation of such an asymmetrically divergent beam with a combination of the fast- and slow-axis collimating lenses, or FAC and SAC lenses, yields a rectangular beam cross-section not convenient for all applications.
Alternatively, the Fast-Axis Reducer (FAR) lens collimates the fast-axis of a laser diode beam with its convex acylindrical surface. Then, its concave cylindrical surface re-introduces the fast axis beam divergence equal to that of the slow axis. The appropriate lens thickness takes care of beam astigmatism. Pairing the Fast Axis Reducer with a rotationally symmetric lens produces a collimated and round beam.
Code Description Glass Diode Aspect Ratio (F:S)
ZEMAX D142-0404 FAR_1:3_STIH53_520 S-TIH53 1 : 3
520 0.100 0.412 0.438 D142-0402 FAR_1:5_STIH53_780 S-TIH53 1 : 5 780 0.069 0.500 0.550
Dimension Tolerance +/- 0.02 mm
Length Tolerance +/- 0.05 mm AR Coating Specification R < 0.5%, AOI 0-30°
Fast Axis Reducer lens