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

Abstract

A laser-detector-hologram (LDH) unit having the size of 4.8 x 8.2 x 4.3 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" 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 plasticmolded 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.

Optical reflectivity of micromachined {111}-oriented silicon mirrors for optical input - output couplers

“…Recently, the reflectivity as well as the tilting angle of the silicon mirrors have been major concerns in realizing silicon micromachined optical I-O couplers. Several silicon micromirrors have already been reported, showing that the {111} plane of silicon makes an excellent reflecting surface [10,11]. Unlike this work, however, these previous research efforts have concentrated on the development of a 45 • mirror with an extremely smooth surface.…”

“…Standard anisotropic etching techniques can be used to expose {111} planes since they etch so much more slowly than any other crystal plane in etchants such as KOH. For this reason, {111} planes have been widely investigated as reflecting surfaces [7][8][9][10]. Although a 45 • mirror would seem the logical choice for an optical I-O coupler, a nonstandard wafer whose polished surface is 9.7 • out of the (100) plane is required as the substrate if one wishes to use {111} planes as the 45 • reflecting surfaces.…”

Development of Microlens for High-Density Small-Form-Factor Optical Pickup

“…7) Tanaka et al developed a NA 0.65 molded single-glass miniaturized lens having very precisely controlled aspheric surfaces. 12) Mori developed a plastic molded miniaturized lens of NA 0.85,which has a temperature compensation element. 13) In previous research studies, it has been shown that for a singleelement lens, the surfaces need to be fabricated more precisely than those of a two-element lens, and the decenter, tilt and thickness errors between the two surfaces can cause serious coma and spherical aberration in the case of a twoelement objective lens.…”