Gert Wrigge

Efficient coupling of photons to a single molecule and the observation of its resonance fluorescence

Single dye molecules at cryogenic temperatures exhibit many spectroscopic phenomena known from the study of free atoms and are thus promising candidates for experiments in fundamental quantum optics. However, the existing techniques for their detection have either sacrificed information on the coherence of the excited state or have been inefficient. Here, we show that these problems can be addressed by focusing the excitation light near to the extinction cross-section of a molecule. Our detection scheme enables us to explore resonance fluorescence over nine orders of magnitude of excitation intensity and to separate its coherent and incoherent parts. In the strong excitation regime, we demonstrate the first direct observation of the Mollow fluorescence triplet from a single solid-state emitter. Under weak excitation, we report the detection of a single molecule with an incident power as faint as 600 aW, paving the way for studying nonlinear effects with only a few photons.

Strong extinction of a laser beam by a single molecule

We present an experiment where a single molecule strongly affects the amplitude and phase of a laser field emerging from a subwavelength aperture. We achieve a visibility of -6% in direct and +10% in cross-polarized detection schemes. Our analysis shows that a close to full extinction should be possible using near-field excitation.

Scanning near-field optical coherent spectroscopy of single molecules at 1.4 K.

We present scanning near-field extinction spectra of single molecules embedded in a solid matrix. By varying the tip-molecule separation, we modify the line shape of the spectra, demonstrating the coherent nature of the interaction between the incident laser light and the excited state of the molecule. We compare the measured data with the outcome of numerical calculations and find a very good agreement.

Exploring the limits of single emitter detection in fluorescence and extinction

We show experimentally that the signal-to-noise ratio of extinction detection can be advantageous to fluorescence measurements of a single molecule. We discuss the prospects of detecting weak emitters such as rare earth ions.

Control and imaging of single-molecule spectral dynamics using a nano-electrode

We study the influence of a scanning nano-electrode on the fluorescence excitation spectra of single terrylene molecules embedded in thin p-terphenyl films at cryogenic temperatures. We show that applied voltages of less than 10 V can result in reversible Stark shifts of up to 100 times and a linewidth increase greater than 10 times the natural linewidth. We discuss the potential of our experimental scheme for the direct imaging of individual two-level systems in the nanometer vicinity of single molecules.

Efficient coupling of light to a single molecule, observation of its fluorescence Mollow triplet, and more

Efficient coupling of laser to single quantum emitters is achieved via near- and far-field techniques. Direct detection of 11.5% extinction and the first direct measurement of the Mollow triplet in solid state system are demonstrated.

Strong light extinction by a single molecule

We present cryogenic experiments where the direct signature of a single molecule on an incident laser beam is demonstrated. Strong extinction larger than 10% is achieved in near and farfield geometries.

Quantum Optical Experiments with Single Molecules

We introduce a cryogenic experiment where the direct signature of a single molecule on an incident laser beam becomes evident We use both near-field and far-field optics to achieve strong extinction effects larger than 10%.

Strong Light Extinction by a Single Molecule

In this paper direct measurements of light extinction by single molecules are reported. We use both near-field aperture tips and confocal microscopy at cryogenic temperature to tightly confine the excitation light to an area comparable to the absorption cross section of a single molecule, which results in directly observable 10% extinction of the laser beam. It is concluded that the access to both the incoherent and coherent emission of single molecules opens up a broad range of studies on the light-matter interaction of single solid state emitters.