title: A miniature photorefractive circuit for principal component extraction.
abstract: The optical feature extractor is a photorefractive ring oscillator that can identify the strongest spatiotemporal component of its input space. The theoretical sections discuss the design and performance limitations of the signal extractor. A simple model of the filter's nonlinear functioning enables the reader to go directly to the experimental section that describes the making of the filter and experimental results. The device, also called the auto-tuning filter, is 5 cm2 in size, has a 3 GHz processing bandwidth, and requires less than 5 mW of continuous optical power to operate.