| dc.description.abstract | Due to nonlinear excitation, multi-photon microscopy could provide well performance at axial and lateral resolution. In addition, the wavelength of excitation light is longer than the wavelength of single-photon microscopy relatively. Hence, it has better penetration depth. Take harmonic generation for an instance, during the excitation process, there is no transition of real energy state. Complying with the conservation of momentum. Accordingly, cause less optical bleaching or damage to the interacted tissues.
Harmonic generation is different from fluorescence signal. There is no transition of real energy state. As a result, the super resolution microscopy of fluorescence is not
suitable for harmonic generation. Ground state depletion microscopy was published by S. W. Hell at 1994. By decreasing the number of electron of ground, affect the absorption of the sample. As a consequence, modulate the intensity of fluorescence. This essay apply a characteristic of harmonic generation: if there is real energy state of multi-photon absorption, it will enhance the intensity of harmonic generation. Therefore, we can decade the enhancement of harmonic generation by applying GSD. Finally, we can modulate the enhance the signal of harmonic generation.
Owing to the high intensity requirement of multi-photon. This essay will apply 2-D point scanning system to obtain THG image. Furthermore, involving the depletion light make the sample GSD。THG comply with the momentum of the insert photon. The system will set up as a forward system. THG will be detected by a photomultiplier tube, which is mounted with a UV filter.
This research consider melanin and hemoglobin as sample for GSD testing. Our system take 1064 nm femto-second laser as excitation laser. According to the absorption spectrum of sample, use 532 nm continuous wave laser as depletion light. In order to generate a structured illumination depletion light. Use Spatial Light Modulator (SLM) to diffract the light. Make use of the +1 and 1 order diffraction light to interfere at the focal plane of the sample. Consequently, generate the sinusoidal structured illumination. In this way, we can modulate the THG at different intensity of depletion light. | en_US |