Holographic laser module with dual wavelength for digital versatile disc optical heads

Backward compatibility with CD'-R necessitates having two laser sources in the digital versatile disc (DVD) pickup head. The dual-wavelength optical h ead complicates pickup design and enlarges the volume of the head. Moreover , it increases the number of components and assembly cost. In this paper, w e present a new design for a dual-wavelength holographic pickup-head module . Packaged together in the module are two laser diodes, photodiodes and a h olographic optical element (HOE) for diffracting reflected light from the d isk onto the corresponding photodetectors. This module can be used as the c ore of an optical head capable of reading DVD, CD and CD-R.