We measure the quantum efficiency (QE) of individual dibenzoterrylene (DBT)<br>molecules embedded in para-dichlorobenzene at cryogenic temperatures. To achieve<br>this, we apply two distinct methods based on the maximal photon emission and on<br>the power required to saturate the zero-phonon line. We find that the outcome of<br>the two approaches are in good agreement, reporting a large fraction of molecules<br>with QE values above 50 %, with some exceeding 70 %. Furthermore, we observe<br>no correlation between the observed lower bound on the QE and the lifetime of the<br>molecule, suggesting that most of the molecules have a QE exceeding the established<br>lower bound. This confirms the suitability of DBT for quantum optics experiments.<br>In light of previous reports of low QE values at ambient conditions, our results hint at<br>the possibility of a strong temperature dependence of the QE.
Stimulated Raman transition in a single molecule
Johannes Zirkelbach, Burak Gürlek, Masoud Mirzaei, Alexey Shkarin, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
The small cross section of Raman scattering has hampered the direct study of this eect at the<br>single molecule level. By exploiting the high Franck-Condon factor of a common-mode resonance,<br>choosing a large vibrational frequency dierence in electronic ground and excited states, and operation<br>at T < 2K, we succeed at driving a coherent stimulated Raman transition in a single molecule.<br>We observe and model a spectral splitting that serves as a characteristic signature of the coherent<br>phenomenon at hand. Our study sets the ground for exploiting the intrinsically ecient coupling<br>of the vibrational and electronic degrees of freedom in molecules for quantum optical operations in<br>the solid state.
On-chip interference of scattering from two individual molecules in plastic
Dominik Rattenbacher, Alexey Shkarin, Jan Renger, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
Integrated photonic circuits offer a promising route for studying coherent cooperative effects of a controlled collection of quantum emitters. However, spectral inhomogeneities, decoherence and material incompatibilities in the solid state make this a nontrivial task. Here, we demonstrate efficient coupling of a pair of organic molecules embedded in a plastic film to a TiO2 microdisc resonator on a glass chip. Moreover, we tune the resonance frequencies of the molecules with respect to that of the microresonator by employing nanofabricated electrodes. For two molecules separated by a distance of about 8μm and an optical phase difference of about π/2, we report on a large collective extinction of the incident light in the forward direction and the destructive interference of its scattering in the backward direction. Our work sets the ground for the coherent coupling of several molecules via a common mode and the realization of polymer-based hybrid quantum photonic circuits.
High-resolution vibronic spectroscopy of a single molecule embedded in a
crystal
Johannes Zirkelbach, Masoud Mirzaei, Irena Deperasińska, Boleslaw Kozankiewicz, Burak Gürlek, Alexey Shkarin, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
The Journal of Chemical Physics
156
104301
(2022)
|
Journal
Vibrational levels of the electronic ground states in dye molecules have not been previously explored at high resolution<br>in solid matrices. We present new spectroscopic measurements on single polycyclic aromatic molecules of dibenzoter-<br>rylene embedded in an organic crystal made of para-dichlorobenzene. To do this, we use narrow-band continuous-wave<br>lasers and combine spectroscopy methods based on fluorescence excitation and stimulated emission depletion (STED)<br>to select individual vibronic transitions at a resolution of ∼30 MHz dictated by the linewidth of the electronic ex-<br>cited state. In this fashion, we identify several exceptionally narrow vibronic levels in the electronic ground state with<br>linewidths down to values around 2 GHz. Additionally, we sample the distribution of vibronic wavenumbers, relax-<br>ation rates, and Franck-Condon factors, both in the electronic ground and excited states for a handful of individual<br>molecules. We discuss various noteworthy experimental findings and compare them with the outcome of DFT cal-<br>culations. The highly detailed vibronic spectra obtained in our work pave the way for studying the nanoscopic local<br>environment of single molecules. The approach also provides an improved understanding of the vibrational relaxation<br>mechanisms in the electronic ground state, which may help to create long-lived vibrational states for applications in<br>quantum technology.
Nanoscopic charge fluctuations in a gallium phosphide waveguide measured by single molecules
Alexey Shkarin, Dominik Rattenbacher, Jan Renger, Simon Hönl, Tobias Utikal, Paul Seidler, Stephan Götzinger, Vahid Sandoghdar
We present efficient coupling of single organic molecules to a gallium phosphide subwavelengthwaveguide (nanoguide). By examining and correlating the temporal dynamics of various single-molecule resonances at different locations along the nanoguide, we reveal light-induced fluctuationsof their Stark shifts. Our observations are consistent with the predictions of a simple model basedon the optical activation of a small number of charges in the GaP nanostructure.
Precision single-particle localization using radial variance transform
Anna Kashkanova, Alexey Shkarin, Reza Gholami Mahmoodabadi, Martin Blessing, Yazgan Tuna, André Gemeinhardt, Vahid Sandoghdar
We introduce an image transform designed to highlight features with high degree of radial symmetry for identification and subpixel localization of particles in microscopy images. The transform is based on analyzing pixel value variations in radial and angular directions. We compare the subpixel localization performance of this algorithm to other common methods based on radial or mirror symmetry (such as fast radial symmetry transform, orientation alignment transform, XCorr, and quadrant interpolation), using both synthetic and experimentally obtained data. We find that in all cases it achieves the same or lower localization error, frequently reaching the theoretical limit.
Ultrahigh-speed imaging of rotational diffusion on a lipid bilayer
Mahdi Mazaheri, Jens Ehrig, Alexey Shkarin, Vasily Zaburdaev, Vahid Sandoghdar
We studied the rotational and translational diffusion of a single gold nanorod linked to a supported lipid bilayer with ultrahigh temporal resolution of two microseconds. By using a home-built polarization-sensitive dark-field microscope, we recorded particle trajectories with lateral precision of three nanometers and rotational precision of four degrees. The large number of trajectory points in our measurements allows us to characterize the statistics of rotational diffusion with unprecedented detail. Our data show apparent signatures of anomalous diffusion such as sublinear scaling of the mean-squared angular displacement and negative values of angular correlation function at small lag times. However, a careful analysis reveals that these effect stem from the residual noise contributions and confirms normal diffusion. Our experimental approach and observations can be extended to investigate diffusive processes of anisotropic nanoparticles in other fundamental systems such as cellular membranes or other two-dimensional fluids.
Coherent coupling of single molecules to on-chip ring resonators
Dominik Rattenbacher, Alexey Shkarin, Jan Renger, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
We report on cryogenic coupling of organic molecules to ring microresonators obtained by looping subwavelength waveguides (nanoguides). We discuss fabrication and characterization of the chip-based nanophotonic elements which yield a resonator finesse in the order of 20 when covered by molecular crystals. Our observed extinction dips from single molecules reach 22%, consistent with an expected enhancement factor of up to 11 for the molecular emission into the nanoguide. Future efforts will aim at efficient coupling of a handful of molecules via their interaction with a ring microresonator mode, setting the ground for the realization of quantum optical cooperative effects.
Turning a molecule into a coherent two-level quantum system
Daqing Wang, Hrishikesh Kelkar, Diego-Martin Cano, Dominik Rattenbacher, Alexey Shkarin, Tobias Utikal, Stephan Götzinger, Vahid Sandoghdar
The use of molecules in quantum optical applications has been hampered by incoherent internal vibrations and other phononic interactions with their environment. Here we show that an organic molecule placed into an optical microcavity behaves as a coherent two-level quantum system. This allows the observation of 99% extinction of a laser beam by a single molecule, saturation with less than 0.5 photons and non-classical generation of few-photons super-bunched light. Furthermore, we demonstrate efficient interaction of the molecule–microcavity system with single photons generated by a second molecule in a distant laboratory. Our achievements represent an important step towards linear and nonlinear quantum photonic circuits based on organic platforms.
