Development of hybrid tip-enhanced IR-Raman microscopy for the study of molecular optomechanical upconversion

Optical control of mechanical oscillators of widely different dimensions are all described by the same cavity optomechanics interaction between phonons and photons inside a cavity.

In the previous decades, various research groups leveraged on this interaction to cool the mechanical oscillators to its ground-state and to produce and detect quantum states of light.The applicant wants to take advantage of mechanical modes that are deeply in their ground state at room temperature, namely vibrational modes of molecules with resonance frequencies in the IR to THz frequency range (between 1-100 THz) to explore the novel molecular optomechanical frequency conversion process (m-OMC).

The key idea of the process consists in upconverting a weak IR signal into the visible domain via molecules (with modes both Raman and IR active) placed onto metallic nanoantennas, opening the whole toolbox of visible field manipulation and detection to electromagnetic fields in the IR range.

The goal of TERRaMoOn is to study the m-OMC process with a hybrid near-field microscope, where the near-field probe (metallic atomic force microscopy (AFM) tip) takes over the role of one of the antennas.

In the near-field microscopy approach, the tip-antenna configuration can be tuned in-situ offering unprecedented versatility to the m-OMC process and enabling to access fundamental insights that would be inaccessible to typically studied on-chip devices. m-OMC could also lead to a new modality of near-field microscopy, where IR modes could be imaged with nanoscale spatial resolution and with exceptional sensitivity by making use of the frequency conversion process.

The molecular layers studied during the project will finally enable the first unambiguous measurements of vibrational strong coupling via a Raman experiment.

As such, TERRaMoOn promises to open novel enticing fundamental and technological research directions and to have a long-standing impact in the field.