| Summary: | 碩士 === 國立中央大學 === 光電科學與工程學系 === 104 === This thesis aims to suppress third harmonic generation (THG) signals through ground state depletion (GSD) based on the concept of stimulated emission depletion in STED microscopy. The STED microscopy is based on fluorescent signals. By depleting the fluorescence signals, it modulates the point spread function (PSF) of fluorescence signals to reach super resolution. However, the applications of STED are limited by the using of fluorescence signals. To overcome this limitation, we propose a new concept to modulate the PSF of THG signals through GSD to improve the resolution of THG microscopy.
To prove this idea, we illustrate that the material absorption can enhance the THG signals and can be suppressed through ground state depletion. Proper sample of is made and its nonlinear coefficient is measured by both Z-scan technique and interface THG signals measurement. Combined with depletion light, the two-photon absorption coefficient is proved to be suppress through GSD, while the THG at interface is shown to decline with increasing depletion light intensity. Finally, applying the measured nonlinear coefficients to resolution simulation, the results indicate the resolution of THG microscopy can reach 69 nm or smaller based on GSD.
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