Lattice-Resonance Metalenses for Fully Reconfigurable Imaging

Metalenses are compact lensing components based on rationally designed nanoscale building blocks. These planar devices are crucial for miniaturized imaging systems that can be integrated into portable electronic and optical devices. However, existing metalenses have fixed structures of hard materials that cannot be reshaped once fabricated and cannot adjust their focal spots adaptively based on […]

Stretchable nanolasers from hybrid quadrupole plasmons

We achieved mechanical control of the lasing color by exploiting a lasing cavity based on periodic arrays of nanoparticles in a stretchable, polymer matrix. This materials system could achieve reversibly tunable lasing as well as superior sensitivity to applied strain. Large metal nanoparticles arranged in a lattice produce high-quality hybrid quadrupole plasmon modes that are […]

Detecting and Visualizing Reaction Intermediates of Anisotropic Nanoparticle Growth

Understanding the underlying mechanism for the synthesis of metallic nanoparticles is crucial for strategic creation of desirable particles. We have recently designed a correlative approach to detect, visualize, and characterize intermediate species during a seedless, anisotropic nanoparticle synthesis. We showed how EPR radical signals of intermediates during a nanoparticle reaction can be combined with optical […]

Band-Edge Engineering for Controlled Multi-Modal Nanolasing in Plasmonic Superlattices

Miniaturized lasers enable applications in on-chip optical communication, medical imaging, and nanoscale optical displays. Compared to traditional lasers, plasmonic nanolasers can break the diffraction limit and support ultrasmall mode volumes, but unwanted multi-modal nanolasing exhibits both uncontrolled mode spacing and output behavior. Single band-edge states can trap slow light and function as high-quality optical feedback […]

Evolutionary Design and Prototyping of Single Crystalline Titanium Nitride Lattice Optics

Plasmonic metasurfaces—structured materials with subwavelength units—are of interest for applications ranging from high resolution imaging to 3D holography. Integrated devices, however, are challenging to achieve because traditional plasmonic materials such as Ag or Au are not compatible with semiconductor processing. Recently, TiN has received attention as an unconventional plasmonic material because of its potential CMOS […]

Multiscale, Hierarchical Patterning of Graphene by Conformal Wrinkling

Patterning three-dimensional (3D) structure into two-dimensional (2D) graphene is important for applications in flexible electrodes, stretchable electronics and energy storage devices. We have demonstrated a conformal wrinkling process that can generate hierarchical graphene architectures. Multi-scale graphene patterning is achieved by sandwiching a soft fluoropolymer skin layer between as-synthesized graphene and pre-strained polystyrene substrates. Because the […]

Stretchable superhydrophobicity from monolithic, three-dimensional hierarchical wrinkles

Superhydrophobic surfaces that can also withstand mechanical deformation such as bending and stretching are important for applications such as robust self-cleaning, water-resistant electronics, and flexible microfluidics. We developed monolithic, multi-scale poly(dimethylsiloxane) (PDMS) nanowrinkles that can exhibit stretchable superhydrophobicity using high fidelity pattern transfer. The droplet impact dynamics revealed that droplet rebound depended strongly on the […]

Screening New Plasmonic Materials

Surface plasmon polaritons (SPPs) are responsible for exotic optical phenomena including negative refraction, surface enhanced Raman scattering, and nanoscale focusing of light. Although many materials support SPPs, the choice of metal for most applications has been based on traditional plasmonic materials (Ag, Au) because there have been no side-by-side comparisons of the different materials on […]

The Dark Side of Surface Plasmons

Plasmonic nanostructures concentrate optical fields into nanoscale volumes, which is useful for plasmonic nanolasers, surface enhanced Raman spectroscopy, and white-light generation. However, the short lifetimes of the emissive plasmons correspond to a rapid depletion of the plasmon energy, preventing further enhancement of local optical fields. Dark (subradiant) plasmons have longer lifetimes, but their resonant wavelengths […]

Superlatice Plasmons in Hierarchical Au Nanoparticle Arrays

Periodic metal nanoparticle (NP) arrays support narrow lattice plasmon resonances that can be tuned by changing the localized surface plasmons of the individual NPs in the array, NP periodicity, and dielectric environment. The high quality factors (100-200) of lattice plasmon resonances enabled NP arrays to function as nanocavities for surface-emitting lasers. We have developed optical […]