RESUMEN
We report the experimental observation of the UV-visible upconverted luminescence of bulk silicon under pulsed infrared excitation. We demonstrate that non-stationary distribution of excited carriers leads to the emission at spectral bands never to our knowledge observed before. We show that the doping type and concentration alter the shape of luminescence spectra. Silicon nanoparticles have a size between quantum-confined and Mie-type limits (10-100 nm) yet show increased luminescence intensity when placed atop a silicon wafer. The findings demonstrate that upconversion luminescence can become a powerful tool for nearest future silicon wafer inspection systems as a multimodal technique of measuring the several parameters of the wafer simultaneously.
RESUMEN
People with low vision have limited residual vision that can be greatly enhanced through high levels of magnification. Current assistive technologies are tailored for far field or near field magnification but not both. In collaboration with L.V. Prasad Eye Institute (LVPEI), a wearable, optical-digital assistive device was developed to meet the near and far field magnification needs of students. The critical requirements, system architecture and design decisions for each module were analyzed and quantified. A proof-of-concept prototype was fabricated that can achieve magnification up to 8x and a battery life of up to 8 hours. Potential user evaluation with a Snellen chart showed identification of characters not previously discernible. Further feedback suggested that the system could be used as a general accessibility aid.