In vivo stimulation on rabbit retina using CMOS LSI-based multi-chip flexible stimulator for retinal prosthesis.

We have performed in vivo electric stimulation experiments on rabbit retina to demonstrate feasibility of CMOS LSI-based multi-chip flexible neural stimulator for retinal prosthesis. We have developed new packaging structure with an improved flexibility and device control system which totally controls the LSI-based multi-chip stimulator, counter electrode, and stimulation generator. We have implanted the fabricated multi-chip stimulator into sclera pocket for STS (Suprachoroidal Transretinal Stimulation) configuration. We successfully obtained EEP (Electrically Evoked Potential) on visual cortex evoked by the multi-chip stimulator.

A multi-chip-architecture based flexible stimulation device for retinal prosthesis with a flip-chip packaging technique.

In the present work, we designed a multi-chip-architecture based flexible neural stimulation device for retinal prosthesis. Based on the multi-chip architecture, a novel CMOS stimulation device was successfully designed and characterized. A packaging technique for thin, flexible neural stimulation device was also proposed and demonstrated. Flip-chip bonding technology plays an essential role in the fabrication of the present thin and flexible neural stimulation device.

Laser Doppler velocimeter with a novel optical fiber probe.

A practical laser Doppler velocimeter with optical fibers in the whole system was developed. The novel optical probe designed for this LDV is constructed of a graded-index rod lens attached to the end of an optical fiber. Since the laser beam from the probe is well collimated, the velocity accuracy and sensitivity are significantly improved. Mechanical vibration measurements were also carried out with this LDV; vibration amplitude down to 1.0 microm p-p can be measured at a frequency of 120 Hz with high accuracy.

Optical bypass switch for fiber-optic data bus systems.

A new type of optical bypass switch, installed in multimode-fiber data bus systems, was constructed of graded-index rod lenses and movable mirrors. This four-port component is operated mechanically by a small electromagnet and a spring. It has an insertion loss as low as 1.2 dB and a cross talk <-45 dB. Results of endurance, temperature, humidity, and vibration tests for this switch are reported.

Mode control of Ti-diffused LiNbO(3) slab optical waveguide.

The investigations were carried out on optical waveguides obtained by thermal diffusion of Ti into LiNbO(3) single crystals. In the Ti-diffused LiNbO(3) slab waveguides, the relationships of the refractive index profile (index change at the surface, diffusion depth) to various diffusion conditions were examined. Conditions were found to fabricate the waveguides of the required number of modes (TE modes) and effective indices for the wavelength of a He-Ne laser (0.6328 microm) and a GaAs-GaAIAs double heterostructure laser (DH laser) (0.8730 microm). The slab waveguides of the required number of modes and effective indices could be obtained by adjusting only the thickness of evaporated Ti film.

Efficiency of thin-film acoustooptic light deflectors for a Gaussian guided optical beam.

We have investigated deflection efficiency of thin-film acoustooptic light deflectors for a narrow guided optical beam (GOB). Dependences of the maximum deflection efficiency eta(max) on spreading angle (deltatheta) of such a GOB and that (deltaPhi) of a surface acoustic wave were revealed experimentally and theoretically for He-Ne and GaAlAs double heterostructure (DH) lasers. eta(max) is drastically reduced when deltatheta increases to deltaPhi; and eta(max) increases with increasing deltaPhi for fixed deltatheta. Even for a DH laser having a spectral halfwidth of about 63 A, the spectral distribution scarcely affects eta(max) in this deflector. Some restrictions are pointed out in designing the deflector with higher eta(max) for a narrow GOB.