| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 104 === We successfully fabricated an all-optical switch using a Si nanocrystal microdisk resonator and we used the tapered fiber coupling method for measurement. The transmission spectrum is measured with a Super Luminescent Diode whose center wavelength is 1541nm. This diode can be used to verify the perfection of microdisk resonators fabrication and show the characteristic modal structure of whispering-gallery modes. Furthermore, we combined a pulse generator and a blue laser as a 405nm pulse laser whose pulse width and frequency can be adjusted. Then we used it in the pump-probe measurement and observed the refractive index variation that caused by the pumped carriers under short-time scale. The refractive index variation causes the wavelength shift of WGMs. In the summary, we discussed the appropriateness of this material based on our measured results.
First we deposited Si-rich oxide by plasma enhanced chemical vapor deposition (PECVD). Then we used the 1200ᵒC post-annealing process to form the Si nanocrystals thin film. Subsequently, we used standard lithography to transform our patterns onto the nanocrystals thin film and dry etched the underlying Si substrate by SF6 . Finally, we successfully fabricated a 20μm microdisk resonator. From the transmission spectrum, we can observe first and second order radial modes. The quality factors are 2500 and 2100, respectively.
The switching time of Si nanocrystal microdisk resonators is ten times better than the carrier lifetime of nanocrystal. It indicates that the fabrication of microdisk devices is helpful for improving the switching speed.
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