Bernard W. Bell

Recent Advancements in DataPlay's Small Form-Factor Optical Disc and Drive

A small form-factor 0.85NA red laser system with 1 GB capacity per 32 mm cartridge will be reviewed. Test results from write once media and newly developed first surface rewritable media will be shown. Modifications to the micro optical pickup (OPU) to use a high power laser diode to support rewritable media will be described, and results of thermal analysis of the complete drive system will be presented.

Performance characteristics of a 32 mm small form-factor optical disc and drive

Experimental data obtained from testing the DataPlay 32 mm disc and drive are presented. Of particular interest, due to the unique rotary tilt arm actuator and front surface head/media architecture is the data concerning shock, vibration, and temperature and humidity stress environments. Results demonstrate that the DataPlay optical drive and media are sufficiently robust for use in portable consumer electronics devices.

Demonstration of Holographic Read-Only-Memory Mastering, Replication, and Playback with a Compact Reader

Development prototype systems for holographic read-only-memory (ROM) are demonstrated, capable of high density recording at 406.7 nm wavelength with 0.71 numerical aperture optics. A phase-conjugate Fourier transform lens is developed for improved capacity and tolerances and incorporated into a fully functional compact reader about 1 cm in height. The capacity target for the first generation is 4 Gbytes in a 42×35 mm2 media card. Two-step mastering, replication, and playback are demonstrated for digital audio stored in 125 holograms.

Fabrication and Testing of a GaP SIL with NA=2.64

A solid immersion lens (SIL) is described with NA = 2.64 that is fabricated from a two-step process using a large BK7 glass hemisphere and a small GaP hemisphere. The Gallium Phosphide (GaP) hemisphere has a radius 114μm, and is cemented in the center of BK7 SIL with index-matching epoxy. The BK7 SIL thickness is accommodated to have both BK7 SIL and GaP SIL in an image centric configuration. The two-step GaP SIL is tested on an induced polarization imaging system. Induced polarization pupil images, the native polarization image and induced polarization image of a DVD RW sample are given in this paper.

Recent Advances in Near-Field-Based Small Form Factor Optical Storage

A review of small form factor optical storage (media diameters less than 50 mm) is presented with emphasis on the development of near-field technology. The current efforts are summarized together with the commercially desired attributes. The results of the examination of gallium phosphide (GaP) and diamond solid immersion lenses in conjunction with evanescent coupling are presented. A polarization-based gap error signal (GES) technique for air-gap servocontrol is described. Results indicate that the method is relatively insensitive to contamination on the surface and can resolve 100-nm surface features. A 50-GB 120-mm read-only memory (ROM) disc was successfully read and the results indicate that a 10-GB 32-mm diameter RW/ROM optical disc based on 650-nm lasers should be feasible

An increased capacity DataPlay optical disc and drive

Based on new market opportunities for consumer electronics devices DataPlay has designed a new version small form-factor optical disc and drive featuring a capacity of 750MB per disc as compared to 500MB per disc of the original product. The NA of the optical pickup has been increased from 0.60 to 0.72. The track pitch of the media has been reduced from 0.74um to 0.60um, and the smallest mark size has been decreased from 435nm to 358nm. Details of the new design are presented as well as test results that show the higher capacity design is sufficiently robust to be used in consumer devices.

Front Surface Recording Reliability Studies

The data reliability of a front surface optical recording system using a 32 mm disk is demonstrated. The system has approximately the same areal density as the digital versatile disk (DVD) system but utilizes an enhanced error correction coding (ECC) architecture. Theoretical statistical error analysis of the ECC subsystem shows a significantly reduced mis-correction probability. Experimental results from laboratory smoke and dust contamination studies as well as real world experiments performed in an office, a smoky bar, and a greasy kitchen environment are discussed and confirm the robust performance of the system predicted by the theory.

Feedback Light Coherence Issues in Micro Optical Pick-Ups

The conditions for optimizing laser feedback in small optical pick-ups using 660 nm strained quantum well laser diodes are discussed. Peaks in the coherence function occurring as a periodic function of the feedback path length are found to diminish rapidly once high frequency drive current modulation is applied. However, feedback path lengths less than 25 mm still show large values. This coherent feedback makes the laser sensitive to variations in the phase of the feedback light. The choice of the feedback path length is critical to eliminating these effects.