Photodiode Packaging Technique Using Ball Lens and Offset Parabolic Mirror

In this paper, we demonstrated the use of a photodiode (PD) packaging technique that employs a catadioptric system. This optical system consisted of two components: a BK7 ball lens with a diameter of 1.5 mm that was soldered with glass on a hermetic cap and a plastic-molded offset parabolic mirror with a radius of 550 mu m and an offset of 550 mu m. The offset parabolic mirror was mounted above a surface-illuminated InGaAs pin PD with a detective area of diameter 20 mum. When an incident pencil of rays were passed through the ball lens and then perpendicularly reflected by the mirror and impinged upon the PD, compact planar assembling became possible for numerous electrical parts on a can-type header for minimizing parasitic impedance due to wire bonds. The optical system provided a high coupling efficiency of 98% between a single-mode fiber and the PD.