Ultrafast optical imaging

All the powerful methods of magnetic resonance, from solid-state nuclear magnetic resonance (NMR) to medical magnetic resonance imaging, depend on measuring the time evolution of a spin system following the application of one or more radio frequency pulses. In the visible and ultraviolet, ultrafast optical pulse sequences have been used for many years to measure both population dynamics and coherence phenomena. At low... 

Charge transfer NLO polymers offer the promise of truly unique properties properties that mimic the performance of photorefractive materials, but on ultrafast (picosecond) time scales. Such materials would enable ultrafast photonic applications (e.g. ultrafast optical switching and ultrafast image processing) that are impossible today with any known class of materials. 

Grant, D. M., Elson, D. S., Schimpf, D., Dunsby, C., Requejo-Isidro, J., Auksorius, E., Munro, I., Neil, M. A. A., French, P. M. W. Nye, E., Stamp, G. and Courtney, P. (2005). Optically sectioned fluorescence lifetime imaging using a Nipkow disk microscope and a tunable ultrafast continuum excitation source. Opt. Lett. 30, 3353-5. 

Brighter, tunable ultrafast light sources would benefit many of the areas discussed in the report, particularly infrared-terahertz (between visible light and radio waves) vibrational and dynamical imaging, near-field scanning optical microscopy (NSOM), and X-ray imaging. 

The development of the ultrafast streak camera (8) in the early 1970 s provided a continuous time base for the detection of transient photon signals within the picosecond timescale. Almost immediately the usefulness of image detectors became apparent. Instead of recording streak camera events on film, coupling of the streak camera through an image intensifier to an optical... 

Fig. 18. (a) Ultrafast electron diffraction apparatus consisting of an electron gun chamber, a diffraction chamber, and a detector chamber. Two fs laser pulses are used, one to initiate the chemical change and the second to generate the electron pulse, (b) Detector system incident electrons either directly bombard a small CCD or strike a phosphor-coated fused fiber-optic window. Light emitted from the phosphor is amplified by an image intensifies and brought to a scientific-grade CCD. Both CCDs are thermo-electrically cooled [reproduced with permission from (96), p. 1601. 

Another important aspect about the optical properties of QDs is the multiphoton process which has been widely applied in recent years in biological and medical imaging after the pioneer work of Goeppert-Mayer (1931), Lami et al. (1996), Helmchen et al. (1996), Yokoyama et al. (2006). The multiphoton process has largely been treated theoretically by steady-state perturbation approaches, for example, the scaling rules of multiphoton absorption by Wherrett (1984) and the analysis of two-photon excitation spectroscopy of CdSe QDs by Schmidt et al. (1996). Non-perturbation time-dependent Schrodinger equation was solved to analyze the ultrafast (fs) and ultra-intense (in many experiments the optical power of laser pulse peak can reach... 

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