Abstract: In order to achieve a high brightness optical source with both spatial size and numeric aperture ideal for fiber coupling, an assembly of multiple individually collimated laser diode chips on submount (COS) are mounted onto a common flat surface and redirected through a series of optical components. This is done in such a manner which allows for active reduction of both overall spot size and numeric aperture. This optical stacking technique achieves a high brightness source which is also suitable for directly coupling into an optical fiber, or can achieve enhanced brightness through the use of existing polarization or wavelength combining schemes prior to fiber optic coupling.