Multispectral Imaging with Tunable Plasmonic Filters

We present an angle-insensitive, miniaturized and integratable filtering system based on plasmonic substrates for multispectral imaging. Active tunability of the plasmonic filter allows color recording, estimation of unknown spectra, and determination of spectral singularities, for example, laser lines, while exploiting the full spatial resolution of a B/W conventional camera. Compared to other multispectral imaging systems, the plasmonic filtering system can be placed in front of an existing imaging system, for example, including lenses, supporting a cost-efficient fabrication and integration. Additionally, it is characterized by high angular acceptance, which we demonstrate by imaging with a field-of-view of ∼50°. Further, the number of nonpixelated broadband filters could be varied in situ for faster imaging or higher quality, compared to systems with a fixed number of channels

Four-Fold Color Filter Based on Plasmonic Phase Retarder

We present a plasmonic color filter based on periodic subwavelength silver nanowires, capable of changing the output color by simple rotation of a polarizer. The effect is enabled by a wavelength-dependent phase shift near the plasmon resonance, giving rise to a wavelength-dependent rotation of the incident polarization. Subsequent rotation of an analyzing polarizer leads to an output of four distinct colors (e.g., yellow, blue, purple, and red) and combinations thereof. The plasmon resonance itself can be tuned throughout the visible spectral region by proper choice of fabrication parameters

Color Rendering Plasmonic Aluminum Substrates with Angular Symmetry Breaking

We fabricate and characterize large-area plasmonic substrates that feature asymmetric periodic nanostructures made of aluminum. Strong coupling between localized and propagating plasmon resonances leads to characteristic Fano line shapes with tunable spectral positions and widths. Distinctive colors spanning the entire visible spectrum are generated by tuning the system parameters, such as the period and the length of the aluminum structures. Moreover, the asymmetry of the aluminum structures gives rise to a strong symmetry broken color rendering effect, for which colors are observed only from one side of the surface normal. Using a combination of immersed laser interference lithography and nanoimprint lithography, our color rendering structures can be fabricated on areas many inches in size. We foresee applications in anticounterfeiting, photovoltaics, sensing, displays, and optical security

Direct On-Chip Optical Plasmon Detection with an Atomically Thin Semiconductor

The determination to develop fast, efficient devices has led to vast studies on photonic circuits but it is difficult to shrink these circuits below the diffraction limit of light. However, the coupling between surface plasmon polaritons and nanostructures in the near-field shows promise in developing next-generation integrated circuitry. In this work, we demonstrate the potential for integrating nanoplasmonic-based light guides with atomically thin materials for on-chip near-field plasmon detection. Specifically, we show near-field electrical detection of silver nanowire plasmons with the atomically thin semiconductor molybdenum disulfide. Unlike graphene, atomically thin semiconductors such as molybdenum disulfide exhibit a bandgap that lends itself for the excitation and detection of plasmons. Our fully integrated plasmon detector exhibits plasmon responsivities of ∼255 mA/W that corresponds to highly efficient plasmon detection (∼0.5 electrons per plasmon)

Nanochannel-Based Single Molecule Recycling

We present a method for measuring the fluorescence from a single molecule hundreds of times without surface immobilization. The approach is based on the use of electroosmosis to repeatedly drive a single target molecule in a fused silica nanochannel through a stationary laser focus. Single molecule fluorescence detected during the transit time through the laser focus is used to repeatedly reverse the electrical potential controlling the flow direction. Our method does not rely on continuous observation and therefore is less susceptible to fluorescence blinking than existing fluorescence-based trapping schemes. The variation in the turnaround times can be used to measure the diffusion coefficient on a single molecule level. We demonstrate the ability to recycle both proteins and DNA in nanochannels and show that the procedure can be combined with single-pair Förster energy transfer. Nanochannel-based single molecule recycling holds promise for studying conformational dynamics on the same single molecule in solution and without surface tethering

Spinning a levitated mechanical oscillator far into the deep-strong coupling regime

The field of levitodynamics has made substantial advancements in manipulating the translational and rotational degrees of freedom of levitated nanoparticles. Notably, rotational degrees of freedom can now be cooled to millikelvin temperatures and driven into GHz rotational speeds. However, in the case of cylindrically symmetric nanorotors, only the rotations around their short axes have been effectively manipulated, while the possibility to control rotation around the longer axis has remained a notable gap in the field. Here, we extend the rotational control toolbox by engineering an optically levitated nanodumbbell in vacuum into controlled spinning around its long axis with spinning rates exceeding 1 GHz. This fast spinning introduces deep-strong coupling between the nanodumbell's libration modes, such that the coupling rate $g$ exceeds the bare libration frequencies $\Omega_0$ by two orders of magnitude with $g/\Omega_0=724\pm 33$. Our control over the long-axis rotation opens the door to study the physics of deep-strong coupled mechanical oscillators and to observe macroscopic rotational quantum interference effects, thus laying a solid foundation for future applications in quantum technologies. Additionally, we find that our system offers great potential as a nanoscopic gyroscope with competitive sensitivity

Nanoscale Fluorescence Lifetime Imaging of an Optical Antenna with a Single Diamond NV Center

Solid-state quantum emitters, such as artificially engineered quantum dots or naturally occurring defects in solids, are being investigated for applications ranging from quantum information science and optoelectronics to biomedical imaging. Recently, these same systems have also been studied from the perspective of nanoscale metrology. In this letter, we study the near-field optical properties of a diamond nanocrystal hosting a single nitrogen vacancy center. We find that the nitrogen vacancy center is a sensitive probe of the surrounding electromagnetic mode structure. We exploit this sensitivity to demonstrate nanoscale fluorescence lifetime imaging microscopy (FLIM) with a single nitrogen vacancy center by imaging the local density of states of an optical antenna

Individual Template-Stripped Conductive Gold Pyramids for Tip-Enhanced Dielectrophoresis

Gradient fields of optical, magnetic, or electrical origin are widely used for the manipulation of micro- and nanoscale objects. Among various device geometries to generate gradient forces, sharp metallic tips are one of the most effective. Surface roughness and asperities present on traditionally produced tips reduce trapping efficiencies and limit plasmonic applications. Template-stripped, noble metal surfaces and structures have sub-nm roughness and can overcome these limits. We have developed a process using a mix of conductive and dielectric epoxies to mount template-stripped gold pyramids on tungsten wires that can be integrated with a movable stage. When coupled with a transparent indium tin oxide (ITO) electrode, the conductive pyramidal tip functions as a movable three-dimensional dielectrophoretic trap which can be used to manipulate submicrometer-scale particles. We experimentally demonstrate the electrically conductive functionality of the pyramidal tip by dielectrophoretic manipulation of fluorescent beads and concentration of single-walled carbon nanotubes, detected with fluorescent microscopy and Raman spectroscopy

Defect-Free Carbon Nanotube Coils

Carbon nanotubes are promising building blocks for various nanoelectronic components. A highly desirable geometry for such applications is a coil. However, coiled nanotube structures reported so far were inherently defective or had no free ends accessible for contacting. Here we demonstrate the spontaneous self-coiling of single-wall carbon nanotubes into defect-free coils of up to more than 70 turns with identical diameter and chirality, and free ends. We characterize the structure, formation mechanism, and electrical properties of these coils by different microscopies, molecular dynamics simulations, Raman spectroscopy, and electrical and magnetic measurements. The coils are highly conductive, as expected for defect-free carbon nanotubes, but adjacent nanotube segments in the coil are more highly coupled than in regular bundles of single-wall carbon nanotubes, owing to their perfect crystal momentum matching, which enables tunneling between the turns. Although this behavior does not yet enable the performance of these nanotube coils as inductive devices, it does point a clear path for their realization. Hence, this study represents a major step toward the production of many different nanotube coil devices, including inductors, electromagnets, transformers, and dynamos

Defect-Free Carbon Nanotube Coils

Carbon nanotubes are promising building blocks for various nanoelectronic components. A highly desirable geometry for such applications is a coil. However, coiled nanotube structures reported so far were inherently defective or had no free ends accessible for contacting. Here we demonstrate the spontaneous self-coiling of single-wall carbon nanotubes into defect-free coils of up to more than 70 turns with identical diameter and chirality, and free ends. We characterize the structure, formation mechanism, and electrical properties of these coils by different microscopies, molecular dynamics simulations, Raman spectroscopy, and electrical and magnetic measurements. The coils are highly conductive, as expected for defect-free carbon nanotubes, but adjacent nanotube segments in the coil are more highly coupled than in regular bundles of single-wall carbon nanotubes, owing to their perfect crystal momentum matching, which enables tunneling between the turns. Although this behavior does not yet enable the performance of these nanotube coils as inductive devices, it does point a clear path for their realization. Hence, this study represents a major step toward the production of many different nanotube coil devices, including inductors, electromagnets, transformers, and dynamos