Waveguide optical pick-up head using mach-zehnder interferometer

Details Waveguide optical pick-up head using mach-zehnder interferometer Waveguide optical pick-up head using mach-zehnder interferometer

1992-07-15

1995-02-14

Psitos, Aristotelis

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369112, 385 14, G11B 7135

Patent

active

053901576

ABSTRACT:
An integrated optic head contains a planar and a channel waveguide, a waveguide condensing lens, and integrated waveguide photodetectors. The main portion of the beam returning from the disk is focused by the lens onto an integrated waveguide photodetector to provide the data signal. A smaller portion of the beam is sampled by channel waveguide Mach-Zehnder (MZ) interferometers that measure the beam wavefront curvature to provide the focus error signal (FES). Additional channel waveguides provide reference signals for the interferometers and provide a means of measuring the tracking error signal (TES). The TES method includes subtracting light detected by one channel waveguide detector from light detected by another, which difference is the tracking error. The FES method includes obtaining the difference in the ratios of the light emanating from two interferometers divided by the light emanating from their respective channel waveguides, which difference in ratios is the focus error.

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