Chip-integrated metasurface full-Stokes polarimetric imaging sensor

Polarimetric imaging has a wide range of applications for uncovering features invisible to human eyes and conventional imaging sensors.Chip-integrated,fast,cost-effective,and accurate full-Stokes polarimetric imaging sensors are highly desirable in many applications,which,however,remain elusive due to fundamental material limitations.Here we present a chip-integrated Metasurface-based Full-Stokes Polarimetric Imaging sensor(MetaPolarIm)realized by integrating an ultrathin(~600 nm)metasurface polarization filter array(MPFA)onto a visible imaging sensor with CMOS compatible fabrication processes.The MPFA is featured with broadband dielectric-metal hybrid chiral metasurfaces and double-layer nanograting polarizers.This chip-integrated polarimetric imaging sensor enables single-shot full-Stokes imaging(speed limited by the CMOS imager)with the most compact form factor,records high measurement accuracy,dual-color operation(green and red)and a field of view up to 40 degrees.MetaPolarIm holds great promise to enable transformative applications in autonomous vision,industry inspection,space exploration,medical imaging and diagnosis.

Chip-integrated plasmonic flat optics for mid-infrared full-Stokes polarization detection

Flat optics presents a new path to control the phase, amplitude, and polarization state of light with ultracompact devices. Here we demonstrate chip-integrated metasurface devices for polarization detection of mid-infrared light with arbitrary polarization states. Six high-performance microscale linear and circular polarization filters based on vertically stacked plasmonic metasurfaces(with total thickness <600 nm) are integrated on the same chip to obtain all four Stokes parameters of light with high accuracy. The device designs can be tailored to operate at any wavelength in the mid-infrared spectral region and are feasible for on-chip integration with mid-infrared(mid-IR) photodetectors and imager arrays. Our work will enable on-chip mid-IR polarimeters and polarimetric imaging systems, which are highly desirable for many applications, such as clinical diagnosis, target detection, and space exploration.

Nature-inspired chiral metasurfaces for circular polarization detection and full-Stokes polarimetric measurements

The manipulation and characterization of light polarization states are essential for many applications in quantum communication and computing,spectroscopy,bioinspired navigation,and imaging.Chiral metamaterials and metasurfaces facilitate ultracompact devices for circularly polarized light generation,manipulation,and detection.Herein,we report bioinspired chiral metasurfaces with both strong chiral optical effects and low insertion loss.We experimentally demonstrated submicron-thick circularly polarized light filters with peak extinction ratios up to 35 and maximum transmission efficiencies close to 80% at near-infrared wavelengths(the best operational wavelengths can be engineered in the range of 1.3-1.6μm).We also monolithically integrated the microscale circular polarization filters with linear polarization filters to perform full-Stokes polarimetric measurements of light with arbitrary polarization states.With the advantages of easy on-chip integration,ultracompact footprints,scalability,and broad wavelength coverage,our designs hold great promise for facilitating chip-integrated polarimeters and polarimetric imaging systems for quantum-based optical computing and information processing,circular dichroism spectroscopy,biomedical diagnosis,and remote sensing applications.

Ultrafast low-pump fluence all-optical modulation based on graphene-metal hybrid metasurfaces

Graphene is an attractive material for all-optical modulation because of its ultrafast optical response and broad spectral coverage.However,all-optical graphene modulators reported so far require high pump fluence due to the ultrashort photo-carrier lifetime and limited absorption in graphene.We present modulator designs based on graphene-metal hybrid plasmonic metasurfaces with highly enhanced light-graphene interaction in the nanoscale hot spots at pump and probe(signal)wavelengths.Based on this design concept,we have demonstrated high-speed all-optical modulators at near and mid-infrared wavelengths(1.56μm and above 6μm)with significantly reduced pump fluence(1–2 orders of magnitude)and enhanced optical modulation.Ultrafast near-infrared pump-probe measurement results suggest that the modulators’response times are ultimately determined by graphene’s ultrafast photocarrier relaxation times on the picosecond scale.The proposed designs hold the promise to address the challenges in the realization of ultrafast all-optical modulators for mid-and far-infrared wavelengths.

Deterministic assembly of single optical cavity formed by gold dimensional DNA origami

Controllable strong interactions between a nanocavity and a single emitter is important to manipulating optical emission in a nanophotonic system but challenging to achieve.Herein a three-dimensional DNA origami,named as DNA rack(DR)is proposed and demonstrated to deterministically and precisely assemble single emitters within ultra-small plasmonic nanocavities formed by closely coupled gold nanorods(AuNRs).Uniquely,the DR is in a saddle shape,with two tubular grooves that geometrically allow a snug fit and linearly align two AuNRs with a bending angle <10°.It also includes a spacer at the saddle point to maintain the gap between AuNRs as small as 2-3 nm,forming a nanocavity estimated to be 20 nm^(3) and an experimentally measured O factor of 7.3.A DNA docking strand is designed at the spacer to position a single fluorescent emitter at nanometer accuracy within the cavity.Using Cy5 as a model emitter,a -30-fold fluorescence enhancement and a significantly reduced emission lifetime(from 1.6 ns to 670 ps)were experimentally verified,confirming significant emitter-cavity interactions.This DR-templated assembly method is capable of fitting AuNRs of variable length-to-width aspect ratios to form anisotropic nanocavities and deterministically incorporate different single emitters,thus enabling flexible design of both cavity resonance and emission wavelengths to tailor light-matter interactions at nanometer scale.