High-speed Broadband Third Harmonic Generation Microscopy System

• Main Authors: Yu-Hsiang Cheng, 鄭宇翔
• Other Authors: 孫啟光
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/38404796842050706317

碩士 === 國立臺灣大學 === 光電工程學研究所 === 101 === Using a Cr:forsterite mode-locked laser (centered at 1260 nm) as the excitation source, I set up a high-speed nonlinear microscope with sub-micron lateral resolution for biomedical imaging applications. Contrast can come from two-photon excitation fluorescence, second harmonic generation, or third harmonic generation. 4 channel images (512 pixels x 512 pixels) could be recorded at a frame rate of 28 fps and shown with pseudo colors on screen in realtime. This microscopy system was successfully applied to human skin imaging and human oral mucosa imaging in vivo. In order to enhance nonlinear signals and excite broadband harmonic responses, the laser pulses were spectrally broadened by a single-mode fiber and then temporally compressed by a prism pair before entering the microscope. The compressed pulse width was 24 fs and the spectrum bandwidth was 82 nm. The broadband third harmonic signals, excited by the compressed pulses, were divided into 3 channels based on different wavelength sections. By analyzing 3 color images pixel by pixel, the frequency response of the nonlinear susceptibility of the specimen can be studied.