Laser-detector-hologram unit for thin optical pick-up head of a CD player

A laser-detector-hologram (LDH) unit having the size of 4.8/spl times/8.2/spl times/1.3 mm for use as a thin optical pick-up head of a CD player has been successfully developed. The technology to make the LDH unit thin and small is based upon the following techniques: 1) an efficient optical combination of a low operating current laser diode and a 45/spl deg/ built-in micromirror which is formed on a Si photodetector substrate, 2) a thin plastic-molded flat package with good thermal dissipation, and 3) a plastic-molded holographic optical element (HOE) as a cap. The pick-up head with the LDH unit has shown good optical performance, which is sufficient for the application to CD players.