Micromachined double-side 45° silicon reflectors for dual-wavelength DVD optical pickup heads

This paper presents hybrid integration of a dual-wavelength laser module using silicon optical benches with double-side 45° micro reflectors fabricated by bulk micromachining technology for DVD optical pickup head applications. The reflector angles are precisely controlled within 45±1°, and the surface roughness of the micro reflectors are less than 20 nm. Two bare chips of edge-emitting laser diodes (LDs), having wavelengths of 650 nm and 780 nm, with their monitor photo diodes were integrated face-to-face using the local-heating method. These two edge-emitting beams are bent vertically by the double-side micro reflectors, and the effective beam separation can be reduced to 75 μm readily. The reflection efficiency of the micro reflectors was higher than 95%, and the effective numerical aperture of the reflector is 0.3. The patterns of focused spots show that the surfaces of the micro reflectors are optically flat planes, which are suitable for optical recording applications.