Researchers have created a method for turning a regular optical substance into a frequency doubler using light. The method could be used to investigate quantum-mechanical tunneling and build all-optical information processing devices.
An optical phenomenon known as frequency doubling occurs in radially asymmetric materials with a second-order nonlinear susceptibility. One photon with a frequency twice that of the initial photons can be created by the interaction of two photons with the same frequency with the material. It can occur at surfaces and interfaces even though the mass of most crystalline materials lacks the necessary asymmetry. However, there are better options for designing useful devices than depending on these incredibly thin regions.
Researchers have produced bulk materials with the proper asymmetries by applying mechanical strain or electrical signals to usually symmetric materials. Using laser light, they have developed a technique for temporarily introducing imbalance into titanium dioxide.Harnessing such frequency double reffects could help maximize the potential of optoelectronics.
They placed a collection of thin gold triangles on a piece of titanium dioxide and used a red laser pulse to highlight them. The light stimulated electrons at the gold’s surface, some moving from the triangles’ ends to the titanium dioxide. Using a different laser, the crew rapidly fired pulses while measuring the frequency of the reflected light.
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