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A novel proximal spectral-reflectance-based plant discrimination sensor for use in selective herbicide spraying systems is developed and its dynamic outdoor performance is experimentally assessed for two plants. For plant illumination, the sensor uses a new stabilized three-wavelength laser diode module that sequentially emits identically polarized laser light beams through a common aperture, along one optical path. Each laser beam enters a multi-spot beam generator, which produces 15 parallel, collimated laser beams spaced over a 230-mm span. The intensity of the reflected light from each beam is detected by a high-speed line scan image sensor. Plant discrimination is based on calculating two different normalised difference vegetation indices, and experimental results show that by improving the stability of the laser diodes, a plant discrimination rate greater than 90% can be achieved with a travelling speed of 7.5 km/h for canola and wild radish, which is a dominant weed in the canola crop field. [ABSTRACT FROM PUBLISHER]

An Opto-VLSI based dynamic RF signal combiner structure is proposed and experimentally demonstrated. The structure utilizes an Opto-VLSI processor in conjunction with an optical fiber array, a photo-detector, and a 4-f imaging lens system to dynamically combine multiple analog RF signals into a single output RF port with a user-defined combination ratio. A proof-of-concept $2\times 1$ analogue RF signal combiner is experimentally demonstrated, and experimental results show that RF signal combination with arbitrary ratio can be achieved by uploading different optimized phase holograms onto the Opto-VLSI processor. [ABSTRACT FROM PUBLISHER]

We theoretically investigate a widely-used plasmonic structure composed of a nano-slit aperture surrounded by surface corrugations. A systematical semi-analytical theory in form of two nested coupled-mode models is developed to provide intuitive physical pictures. Based on the theory, figures of merit (FoMs) of the structures designed for normal and for oblique incidence/beaming are defined for the first time to incorporate the interlinks among key structural parameters, making global optimization simple and efficient. Both the theory and the FoMs are quantitatively validated with exhaustive calculations and shown to be highly accurate on performance prediction and structural optimization. With the theory and the FoMs, an efficient, effective and standard recipe is introduced for optimal structure design. We believe this work will help to understand the mechanisms of and to facilitate the design of such a structure in various configurations used in various applications. [ABSTRACT FROM PUBLISHER]

We have investigated the magnetooptical properties of one-dimensional magnetic photonic crystals for the case of oblique light incidence. We developed a theoretical model based on the transfer matrix approach. We found several new effects such as transmittance resonance peak shift versus external magnetic field and the Faraday effect dependence on the incidence angle. We discuss several possible one-dimensional magnetic photonic crystals applications for the optical devices. [ABSTRACT FROM AUTHOR]