Waveguide-based total internal reflection fluorescence microscope enabling cellular imaging under cryogenic conditions.

Total internal reflection fluorescence (TIRF) microscopy is an important imaging tool for the investigation of biological structures, especially the study on cellular events near the plasma membrane. Imaging at cryogenic temperatures not only enables observing structures in a near-native and fixed state but also suppresses irreversible photo-bleaching rates, resulting in increased photo-stability of fluorophores. Traditional TIRF microscopes produce an evanescent field based on high numerical aperture immersion objective lenses with high magnification, which results in a limited field of view and is incompatible with cryogenic conditions.

Fluorescence Polarization Control for On-Off Switching of Single Molecules at Cryogenic Temperatures.

Light microscopy, allowing sub-diffraction-limited resolution, has been among the fastest developing techniques at the interface of biology, chemistry, and physics. Intriguingly no theoretical limit exists on how far the underlying measurement uncertainty can be lowered. In particular data fusion of large amounts of images can reduce the measurement error to match the resolution of structural methods like cryo-electron microscopy.

Nanoscale Imaging of Light-Matter Coupling Inside Metal-Coated Cavities with a Pulsed Electron Beam.

Many applications in (quantum) nanophotonics rely on controlling light-matter interaction through strong, nanoscale modification of the local density of states (LDOS). All-optical techniques probing emission dynamics in active media are commonly used to measure the LDOS and benchmark experimental performance against theoretical predictions. However, metal coatings needed to obtain strong LDOS modifications in, for instance, nanocavities, are incompatible with all-optical characterization.

Nanoparticle discrimination based on wavelength and lifetime-multiplexed cathodoluminescence microscopy.

Nanomaterials can be identified in high-resolution electron microscopy images using spectrally-selective cathodoluminescence. Capabilities for multiplex detection can however be limited, e.g.

Time-resolved cathodoluminescence microscopy with sub-nanosecond beam blanking for direct evaluation of the local density of states.

We show cathodoluminescence-based time-resolved electron beam spectroscopy in order to directly probe the spontaneous emission decay rate that is modified by the local density of states in a nanoscale environment. In contrast to dedicated laser-triggered electron-microscopy setups, we use commercial hardware in a standard SEM, which allows us to easily switch from pulsed to continuous operation of the SEM. Electron pulses of 80-90 ps duration are generated by conjugate blanking of a high-brightness electron beam, which allows probing emitters within a large range of decay rates.

Self-assembled silver nanoparticles in a bow-tie antenna configuration.

The self-assembly of silver nanoparticles into a bow-tie antenna configuration is achieved with the DNA origami method. Instead of complicated particle geometries, spherical silver nanoparticles are used. Formation of the structures in high yields is verified with transmission electron microscopy and agarose gel electrophoresis.

Cathodoluminescence Microscopy of nanostructures on glass substrates.

Cathodoluminescence (CL) microscopy is an emerging analysis technique in the fields of biology and photonics, where it is used for the characterization of nanometer sized structures. For these applications, the use of transparent substrates might be highly preferred, but the detection of CL from nanostructures on glass is challenging because of the strong background generated in these substrates and the relatively weak CL signal from the nanostructures. We present an imaging system for highly efficient CL detection through the substrate using a high numerical aperture objective lens.

Shaping single emitter emission with metallic hole arrays: strong focusing of dipolar radiation.

Nanoscale plasmonic structures allow for control of the emission of single emitters, such as fluorescent molecules and quantum dots, enabling phenomena such as lifetime reduction, emission redirection and color sorting of photons. We present single emitter emission tailored with arrays of holes of heterogeneous size, perforated in a gold film. With spatial control of the local amplitude and phase of the electromagnetic field radiated by the emitter, a desired near- or far-field distribution of the electromagnetic waves can be obtained.

Reversible polarization control of single photon emission.

We present reversible and a-priori control of the polarization of a photon emitted by a single molecule by introducing a nanoscale metal object in its near field. It is experimentally shown that, with the metal close to the emitter, the polarization ratio of the emission can be varied by a factor of 2. The tunability of polarization decays, when the metal is displaced by typically 30 nm.

Lambda/4 resonance of an optical monopole antenna probed by single molecule fluorescence.

We present a resonant optical nanoantenna positioned at the end of a metal-coated glass fiber near-field probe. Antenna resonances, excitation conditions, and field localization are directly probed in the near field by single fluorescent molecules and compared to finite integration technique simulations. It is shown that the antenna is equivalent to its radio frequency analogue, the monopole antenna.

Probing the negative permittivity perfect lens at optical frequencies using near-field optics and single molecule detection.

Recently, the existence of a perfect lens has been predicted, made of an artificial material that has a negative electric permittivity and a negative magnetic permeability. For optical frequencies a poormans version is predicted to exist in the sub-wavelength limit. Then, only the permittivity has to be negative, a demand that metals fulfill at optical frequencies.