Akitomo Ohba

Holographic Optical Element with Analyzer Function for Magneto-Optical Disk Head

A new holographic optical element, made of a birefringent LiNbO3 substrate, has been developed for magneto-optical, disk heads. The element includes the analyzer function required for magneto-optical signal detection, in addition to focusing and tracking error signal detection functions. The analyzer function was realized by introducing a birefringent grating structure, using proton exchange method. More than 15dB extinction ratios were obtained for the fabricated element.

Reflection polarizing holographic optical element for compact magnetooptical disk heads

A reflection polarizing holographic optical element with sinusoidal surface-relief has been developed for compact magnetooptical (MO) disk heads. The element has the polarizing beam splitter function as well as the focusing and tracking error signal detection functions. To produce the sinusoidal surface-relief structure with photolithography, a new fabrication process, which includes procedures for converting a rectangular profile into a sinusoidal profile, is introduced. Replicas were also fabricated with high replication fidelity using the photopolymerization method. The developed element was used in an MO disk head. A 57-dB C/N ratio, which is sufficient value for practical use was achieved for a 1-MHz readout signal.

Compact magneto-optical disk head using a holographic optical element with analyzer function

A compact magneto-optical disk head was constructed using a newly developed holographic optical element. The element has an analyzer function with more than 5dB extinction ratios for data signal detection1 in addition to focusing and tracking error signal detection functions . The element was fabricated in a birefringent LiNb03 substrate using the proton exchange method. which is a well known waveguide fabrication technique. In Read/Write experiments using the head, sufficient carrier-to-noise ratio values for practical use were obtained. As a typical result, a 47dB carrier-to-noise ratio was obtained for 3.7MHz pulse recorded signal.

Compact Magneto-Optical Disk Head Using Reflection Polarizing Holographic Optical Element

A compact magneto-optical disk head using a reflection polarizing holographic optical element has been developed, which has polarizing beam splitter function and error detection optics functions. As a result of introducing the element into an magneto-optical disk head, a high carrier to noise ratio has been achieved, while simple optics has been used.

Compact optical head module integrated with chip elements for magneto-optical disks

A compact optical head module for magneto-optical disks, combining a hybrid chip integration technology and a polarizing holographic optical element, has been developed. The module size is (phi) 10 mm X t11 mm. The validity of this optical head module has been demonstrated, by successful readout operation for a magneto-optical disk.