High-speed Scanning Near-field Optical Microscopy

The rSNOM was a result of our previous experiences with designing and developing conventional scanning near-field optical microscopes and was the first of our systems to collect multiple images per second [1].

The novel experimental arrangement of the rSNOM, shown in figure 1, is capable of capturing in excess of 100 images per second (10 to 100 thousand times faster than conventional SNOM) mainly thanks to the use of a quartz crystal resonator (a 32 kHz watch tuning fork) rather than the more common piezo-tube to provide the fast scan axis. The probe is attached to this tuning fork, which is then oscillated at its resonant frequency; this produces many thousands of scan lines per second which can be divided up between multiple consecutive images. The stability, amplitude and resonant frequency of these actuators make them ideally suited to high-speed imaging, creating very stable scan lines with oscillation amplitudes of several microns - sufficient for most imaging purposes.

rSNOM enjoys all of the benefits of conventional SNOM (since the contrast mechanism is the same) as well as being substantially faster. The results shown below have therefore generally followed on from previous work, improving the temporal resolution with which the systems have been imaged.

Figure 1. Schematic of the rSNOM instrument.

Sample movie: Standard SNOM time-lapse image of spherulite growth.

Sample movie: rSNOM images of collagen (67 nm D-banding is clearly visible).