Currently used half-height pickups employ semiconductor laser devices with a 5.6-mm-diameter stem. For slim pickups, packages with a D-shaped stem, obtained by cutting off a portion of a 5.6-mm-diameter stem, an I-shaped stem, obtained by cutting off opposite portions of a 5.6-mm-diameter stem, or the like have been proposed. Also proposed are packages with a 3.5- or 3.3-mm-diameter stem (see an exterior view shown in FIG. 13). However, packages with these 3.5- and 3.3-mm-diameter stems are, as will be understood from the external view thereof shown in FIG. 13, simply down-scaled versions of a package with a 5.6-mm-diameter stem, and thus have, inconveniently, accordingly smaller heat sinks on which to place laser devices. Constructions with increased heat sink volumes are also known, for example in Patent Publication 1. However, even these constructions, with semicircular heat sinks, do not offer sufficient volumes.
High-output semiconductor laser devices for CD-Rs and DVD-Rs require larger currents and higher voltages, and thus generate accordingly larger amounts of heat. This makes it difficult to guarantee normal operation at high temperatures of 70° and above by the use of a stem with a small heat-dissipation volume such as a 3.3-mm-diameter stem. Thus, it is important to devise how to maximize the heat-dissipation volume.