Development of optical pickup for digital versatile disc using two-wavelength-integrated laser diode

A digital versatile disc (DVD)-and compact disc (CD)-compatible optical pickup using a two-wavelength-integrated laser diode (TWIN-LD) has been developed. The TWIN-LD has two emission points in one chip, one for the red laser beam to read out signals from DVDs and the other for the IR laser beam to read out signals from CDs that are arranged along the active layer. With the application of a TWIN-LD to the optical pickup, the necessity for four optical components, namely, a laser diode, photodetector, holographic optical element and dichroic prism, is avoided in comparison with conventional optical pickups. This paper discusses some key points for designing an optical system using a TWIN-LD, and the results of the experiments appling the optical system to an optical pickup 7.3 mm in height.