High resolution and high sensitivity near-field optical microscope

We have built a multi-purpose optical microscope by integrating a conventio nal confocal laser microscope (CLM) and a state of the art scanning near-fi eld optical microscope (SNOM) with a conventional inverted optical microsco pe. The setup is designed for fluorescence imaging of delicate samples at v ery low signal levels as found in applications in the Life Sciences. An act ive-feedback closed-loop x-y-scanner with a scan range of 100 x 100 mu m en ables the instrument to rapidly record large area scans using confocal micr oscopy. Interesting areas of the samples identified by such a scan can subs equently be investigated with sub-diffraction limited resolution. The near- field part of the instrument is based on standard optical fibre probes and a non-optical, tuning fork shear-force technique for maintaining the probe- sample distance. An extremely sensitive feedback working on the phase rathe r than the amplitude of the tuning fork response is used in order not to da mage delicate biological samples. First results on mu-contact printed rabbi t IgG and single molecule fluorescence are reported.