Self-pulsation of Nd3+-doped fluoride fiber laser is experimentally and theoretically demonstrated using a Tm3+-doped fluoride fiber pumped at 808 nm as a saturable absorber. Self-pulsation at finite pump power predicted by linear stability analysis is confirmed through experiments, achieving a pulse width and peak power of 4.5µs and 1.5mW when the Nd3+-doped fiber was pumped at 230mW.

On-chip neural interface devices based on CMOS image sensor technology are proposed and demonstrated. The devices were designed with target applications to optogenetics in bioscience. Multifunctional CMOS image sensors equipped with an addressable on-chip electrode array were integrated with a functional interface chip that contained embedded GaInN light emitting diodes (LEDs) and electrodes to create a neural interface. Detailed design information regarding the CMOS sensor chip and the functional interface chip including the packaging structure and fabrication processes are presented in this paper. The on-chip optical stimulation functionality was demonstrated in an in vitro experiment using neuron-like cells cultured on the proposed device.

This study focuses on the design of electrical stimulator for retinal prosthesis. The stimulator must be designed such that the occurrence of electrolysis or any irreversible process in the electrodes and flexible lead is prevented in order to achieve safe stimulation over long periods using the large number of electrodes. Some types of biphasic current pulse circuits, charge balance circuits, and AC power delivery circuits were developed to address this issue. Electronic circuitry must be introduced in the stimulator to achieve the large number of electrodes required to obtain high quality of vision. The concept of a smart electrode, in which a microchip is embedded inside an electrode, is presented for future retinal prostheses with over 1000 electrodes.

We review recently obtained results for CMOS (Complementary Metal Oxide Semiconductor) imaging devices used in biomedical applications. The topics include dish type image sensors, deep-brain implantation devices for small animals, and retinal prosthesis devices. Fundamental device structures and their characteristics are described, and the results of in vivo experiments are presented.