Agriculture is one of the most important and possibly the oldest economic activity developed by humans and it is becoming increasingly dependent on development of technologies (Alexandre, 2009). Agriculture in Africa is a subsistent, low technology and low-performing one which requires reduced drudgery and increased commercialization. For crop production, farmlands are cleared using cutlass and...

We propose a two step method which enables us to obtain transmission Holographic Optical Elements ofhigh diffraction eftirciency as well as a good signal-to-noise relation. By means of a devicc using partially coherent light, LL master Holographic Opticill Element can be copied in a sccond photosensitive material. Thc results which are obtained in dichromiltcd gelatin and photoresist are compar...

This paper simulates the photonic band structure in face-centered-orthorhombic and face-centered-tetragonal woodpile-type photonic crystals and shows the fabrication feasibility of these crystals with phase mask based holographic lithography. The experimental demonstration on SU-8 photoresist indicates that a single optical element can replace a complex optical setup for the holographic fabrica...

Multiplexed volume Bragg gratings can be applied to many types of broad- and narrowband spectral systems. However, there are often deleterious side effects to combining several gratings into a single holographic optical element, including loss of efficiency in diffracted waves of interest and the introduction of spurious waves. Design of these spectral systems requires analysis methods that are...

We present a method of enhancing the diffraction efficiency of a hologram by placing it inside a resonant optical cavity. The diffraction efficiency improves on account of the multiple passes that the incident light undergoes inside the optical cavity. The resonance condition in this case turns out to involve both mirror reflectivity and the optical path length inside the cavity. Experimental r...

We report a new type of holographic interface, which is able to manipulate the three fundamental properties of light (phase, amplitude, and polarization) over a broad wavelength range. The design strategy relies on replacing the large openings of conventional holograms by arrays of subwavelength apertures, oriented to locally select a particular state of polarization. The resulting optical elem...

Current trends in computing and telecommunications point to a growing need for devices that are able to switch optical beams carrying information without having to convert them to electric signals. This would create a whole new generation of hybrid optoelectronic processors combining the computational strength of electronics with the very large information throughput density of optics. Holograp...

Hardpans (plough/hoe pans) are commonly believed to restrict plant root growth and crop yields under conventional small-scale agriculture in sub-Saharan Africa. This study questions the notion of widespread hardpans in Zambia and their remedy under conservation tillage. Soil penetration resistance was measured in 8x12 grids, covering 80 cm wide and 60 cm deep profiles in 32 soil pits. Large and...