| 研究実績の概要 |
Our research goal is to modulate light (signal) using light (control) in an integrated on-chip device with reduced footprint and energy consumption. In order to achieve this high-speed modulation of an optical signal by optical means, we have built an optical setup (pump-probe) that can record the response of a material to a light pulse with a resolution of approximately 100 femtoseconds, fabricated samples made of highly correlated metal-oxide materials such as VO2 in the forms of thin films, nanostructures, and plasmonic nanostructures, and characterized the samples using the developed optical setup. We have found a large and fast modulation in the light signal when the samples were exposed to a pulse of light. The fast modulation is of the order of several hundreds of femtoseconds, but it is unfortunately followed by a slower recovery of the order of hundreds of picoseconds. To clarify the origin of these different time responses, the response of the samples was investigated as a function of the power of the light pulse and the optical setup was modified to allow for a re-pump of the samples. We found that the standard mechanism reported in the literature involving an optically induced insulator-metal transition cannot explain our results. Finally, different strategies to reduce the slow recovery component have been tested. These recent results have been submitted, and our publication is under review.
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