Metal-Optic Nanophotonic Modulators in Standard CMOS Technology

Integrating nanophotonics with electronics promises revolutionary applications, from LiDAR to holographic displays. Although silicon photonics is maturing, realizing active nanophotonics in the ubiquitous bulk CMOS processes remains challenging. We introduce a fabless approach to embed active nanophotonics in bulk CMOS by co-designing the back-end-of-line metal layers for optical functionality. Using a 65nm CMOS process, we create plasmonic liquid crystal modulators with switching speeds 100x faster than commercial technologies. This zero-change nanophotonics method could equip mass-produced chips with optical communications, sensing and imaging. Embedding nanophotonics in the dominant electronics platform democratizes nanofabrication, spawning technologies from chip-scale LiDAR to holographic light-field displays

Ultrafast transient optical loss dynamics in exciton-plasmon nano-assemblies

We study the exciton-plasmon dynamics that lead to optical loss mitigation via ultrafast transient absorption spectroscopy (UTAS) on hybrid aggregates of core-shell quantum dots (QDs) and Au nanoparticles (NPs). We highlight that generating hot electrons in plasmonic NPs contributes to the transient differential absorption spectrum under optical excitation. The results suggest modifying the method of analyzing the transient absorption spectra of loss mitigated systems. Additionally, we investigate the effect of Electron Oscillation frequency-Phonon Resonance Detuning (EOPRD) on loss mitigation efficiency. Moreover, power dependent UTAS reveal a frequency pulling like effect in the transient bleach maximum towards the gain emission. We show that the appropriate choice of the pump wavelength and by changing the pump power we can conclusively prove the existence of loss mitigation using UTAS. Finally, we study the transient kinetics of hybrid gain-plasmon systems and report interesting hybrid transient kinetics. © 2017 The Royal Society of Chemistry

Structural Analysis of a 2-D Micron-Scale Particle Array

General diffraction theory is commonly applied in analyzing crystal structures through x-ray diffraction. However, by using polystyrene spheres with diameters in the micron range, we can observe diffraction directly with visible light. By putting a monolayer of spheres in solution on a glass slide and passing a laser though onto a screen, we observe the distinct diffraction pattern as surface tension draws the spheres into a two-dimensional array. Then, with the help of image processing software, we can take intensity measurements of different regions of the diffraction pattern, calculate lattice spacing of the spheres\u27 lattice in real space, calculate the radial distribution function, and measure the diameter of the spheres to compare with their expected value

Plasmonic analogue of geometric diodes realizing asymmetric optical transmission

Geometric diodes represent a relatively new class of diodes used in rectennas that rely on the asymmetry of a conducting thin film. Here, we numerically investigate a plasmonic analogue of geometric diodes to realize nanoscale optical asymmetric transmission. The device operates based on spatial symmetry breaking that relies on a unique property of surface plasmon polaritons (SPPs), namely, adiabatic nanofocusing. We show that the structure can realize onchip asymmetric electromagnetic transmission with a total dimension of ∼2 µm × 6 µm. We demonstrate a signal contrast of 0.7 and an asymmetric optical transmission ratio of 4.77 dB. We investigate the origin of the asymmetric transmission and show that it is due mainly to asymmetric out-coupling of SPPs to far-field photons. We highlight the role of evanescent field coupling of SPPs in undermining the asymmetric transmission efficiency and show that by adjusting the plasmonic waveguide dimensions, a signal contrast of 0.94 and an asymmetric optical transmission ratio of 5.18 dB can be obtained. Our work presents a new paradigm for on-chip nanoscale asymmetric optical transmission utilizing the unique properties of SPPsK. C. Wong Education Foundation (GJTD2018-08); National Natural Science Foundation of China (11774340, 91750205); National Science Foundatio

Spatial Wavefunction Characterization of Femtosecond Pulses at Single-Photon Level

Reading quantum information of single photons is commonly realized by quantum tomography or the direct (weak) measurement approach. However, these methods are time-consuming and face enormous challenges in characterizing single photons from an ultrafast light source due to the stringent temporal mode matching requirements. Here, we retrieve the spatial wavefunction of indistinguishable single photons from both a continuous wave source and a femtosecond light source using a self-referencing interferometer. Our method only requires nine ensemble-averaged measurements. This technique simplifies the measurement procedure of single-photon wavefunction and automatically mode matches each self-interfering single photon temporally, which enables the measurement of the spatial wavefunction of single photons from an ultrafast light source