Nanometrically stabilized tight focusing and its applications to ultrafast tip-enhanced spectroscopy

Abstract

We have successfully stabilized the tight focus onto the sample surface within ± 1.0 nm for unlimited time scale. Time-dependent thermal drift of the tight focus and the mechanical tilt of the sample surface were non- optically sensed and were compensated in real-time. The focus stabilization is crucial for both microscopic and nanoscopic measurement. The stabilization of the tight focus enables us to perform long-term and robust measurement without any degradation of optical signal, resulting in the capability of true nanometric optical imaging with high reproducibility and high precision. The technique presented is a simple add-on for any kind of optical microscope.