Photothermal Microscopy and
Spectroscopy Webinar

In our group at TU Wien, we explore photothermal spectroscopy utilizing nanomechanical resonators. Traditional photothermal spectroscopy involves illuminating a sample with heating radiation and detecting photothermal heating via the thermo-optical response. In our approach, known as nanomechanical photothermal spectroscopy, we directly measure the photothermal sample heating using a temperature-sensitive nanoelectromechanical drumhead that oscillates at its resonance frequency. This photothermal heating induces a thermal expansion in the drumhead, leading to a discernible detuning in the drum’s frequency. Remarkably, the extent of this frequency detuning directly corresponds to the intensity of the photothermal heating power. Our experiments, conducted with a 50 nm thick silicon nitride drum, enabled us to record the photothermal absorption spectrum of individual nanoparticles, showcasing a large signal-to-noise ratio [1]. These findings set the stage for potential photothermal absorption spectroscopy of single molecules.

1. K. Kanellopulos, R. G. West, S. Schmid, Nanomechanical Photothermal Near Infrared Spectromicroscopy of Individual Nanorods, ACS Photonics, accepted (preprint: arXiv:2305.05287).