Abstract:In this paper, after briefly reviewing the theory of vectorial vortices, we describe our technological approach to generating the necessary phase helix, and report results obtained with the first optical vectorial vortex coronagraph (OVVC) in the laboratory. To implement the geometrical phase ramp, we make use of Liquid Crystal Polymers (LCP), which we believe to be the most efficient technological path to quickly synthesize optical vectorial vortices of virtually any topological charge. With the first prototype device of topological charge 2, a maximum peak-to-peak attenuation of 1.4 × 10 −2 and a residual light level of 3 × 10 −5 at an angular separation of 3.5 λ /d (at which point our current noise floor is reached) have been obtained at a wavelength of 1.55 μm. These results demonstrate the validity of using space-variant birefringence distributions to generate a new family of coronagraphs usable in natural unpolarized light, opening a path to high performance coronagraphs that are achromatic and have low-sensitivity to low-order wavefront aberrations.
Although miniaturisation of vibrational spectrometers began approximately a decade ago, only within the last couple of years have real hand-held Raman, infrared and near infrared (NIR) scanning spectrometers became commercially available. On the customer end the development of portable instrumentation was driven by the request for more flexibility of on-site measurements and on the manufacturer side it was supported by the potential and advantages of micro-electromechanical systems (MEMS) production and the implementation of new technologies. With reference to NIR spectroscopy the expectations for a real hand-held system (<100 g) have been recently realised by a pocket-sized spectrometer with a linear variable filter technology (LVF) as monochromator principle and the additional benefit of significantly reduced costs compared to other portable systems. For a real breakthrough and impact of this instrument, however, it had to be demonstrated that competitive analytical results can be achieved. In this respect, the present communication has put to test the performance of this micro-NIR system with reference to selected qualitative and quantitative pharmaceutical applications.
We wrapped 150 nm period aluminum wire grid polarizer (WGP) with AlSiOx by using atomic layer deposition at 250 degrees C. The nanometer precision coating defined the spacer to double the spatial frequency of the 100 mm diameter grating fabricated by using a legacy immersion holography setup at 351 nm wavelength. Half-pitch grating of approximately 38 nm was demonstrated with good pattern uniformity, excellent repeatability, and a wide processing window. We believe 10 nm half-pitch grating over even larger areas are viable, overcoming one major hurdle to commercialize nanoimprint.
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