Optical characterization at the nanoscale currently requires instruments such as NSOM/TERS, or hybrid AFM with specialized far-field optical microscopes that are quite complicated and do not provide any time-resolved data. We have demonstrated a novel class of probes for Scanning Probe Microscopy (SPM) - an Ultrafast Pulsed Atomic Force Microscopy Optical Probe (UFP AAOP) that will enhance characterization capabilities at the nanoscale and provide an exciting opportunity for obtaining both space- and time-resolved chemical information simultaneously. In the UFP AAOP design, a two-section quantum-dot mode-locked laser is monolithically integrated with an SPM probe fabricated from GaAs, with a nanoscale opening at the apex of the tip as the output aperture. With UFP AAOP, the light is supplied through the tip; hence, there is no scattered far-field light and thus significantly reduced background. Furthermore, the difficulties associated with laser alignment onto the tip and with imaging the signal onto a detector are avoided with the UFP AAOP. The UFP AAOP provides pulses with less than 4 ps duration and spatial resolution better than 300 nm at 1240 nm wavelength. It is potentially possible to reduce the pulse width to ~ 0.3 ps and to improve lateral resolution to ~ 1 nm. These unique optical probes will perform the functions of conventional AFM probes and simultaneously provide information about chemical properties of the sample at the nanoscale together with time-resolved spectroscopy. UFP AAOP will facilitate the creation of a new microscopy/spectroscopy instrument with combined single-molecule spatial resolution and ultrafast time-resolved capability.
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