Up-conversion of infrared (IR) to visible light is demonstrated via an unconventional two-step process combining second harmonic generation with photoluminescence. This is achieved in a composite material formed by single crystals of KH2PO4 (KDP), in which CdTe/CdS quantum dots (QDs) are embedded during a crystal growth. The second harmonic generation from the IR laser frequency in KDP takes place, and then, generated light is absorbed by QDs and luminescence is emitted. Compared to the most common up-converting materials based on lanthanide ions, our novel composites use only abundant elements and have several other properties with application potential: the excitation and emission can cover a broader spectral range, and the response is much faster (ns compared to ms) and is strongly dependent on the direction of the incident beam.
Until recently, science has held the view that the body's activities are managed in two fundamentally different ways - the nervous system, where the central nervous system plays the main coordinating role, and the chemical system.
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