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 pic kup using a two-wavelength-integrated laser diode (TWIN-LD) has been develo ped. 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 th e application of a TWIN-LD to the optical pickup, the necessity for four op tical components, namely, a laser diode, photodetector, holographic optical element and dichroic prism, is avoided in comparison with conventional opt ical pickups. This paper discusses some key points for designing an optical system using a TWIN-LD, and the results of the experiments appling the opt ical system to an optical pickup 7.3 mm in height.