Nanometer-precision measurements of geometric fluctuations via momentum-filtered spectroscopy

In this work, we report ultra-sensitive detection of geometric fluctuations of semiconductor nanostructures using momentum-filtered spectroscopy. Our strategy is developed based on angle-resolved photoluminescence / absorption spectroscopic imaging technique. By filtering out signals with non-zero in-plane momentum using a confocal pinhole, ultra-sensitive detection of tiny geometric fluctuations with nanometer precision was made possible. In this way, we could optically detect geometric fluctuations of semiconductor nanostructures in real time with a spatial resolution as high as ~ 0.2 nm. Moreover, this technique is widely applicable to nanostructures where optical resonance can be formed.