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Compact Optical Pickup with a Two-Wavelength Laser Diode

Optical pickups for digital versatile disk (DVD-ROM) need to be capable of reading compact disc (CD) and recordable compact disk (CD-R) disks. Therefore, two laser sources are needed. A compact optical pickup is presented which employs a dual-wavelength integrated (TWIN) laser diode and a diffractive optical element (DOE). The purpose of the DOE is to combine the two beams emitted by the TWIN laser diode. This substantially facilitates design and fabrication of two-wavelength optical pickups. The design of the DOE is discussed in detail. Experimental results on tolerance conditions and signal quality are shown.