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Sum frequency generation microscopy is a label-free optical imaging technique with intrinsic molecular vibrational contrast for surface studies. Recent developments of compressive sensing broad-band hyperspectral SFG microscopy have demonstrated the potential application for imaging monolayer at metal surfaces with micrometer spatial resolution. Here is presented the capability of chemical imaging of spatially patterned monolayers of 1-octadecanethiol (ODT) and 16-methoxy-1-hexadecanethiol (MeOHT) molecules assembled on a copper surface. The spatial distributions of the monolayer with vibrational-spectral contrast are well-demonstrated at different frequency regions through reconstruction of the hypercube using a 3-dimensional total variation regularization algorithm (3DTV). Spatial-chemical distributions of each component are also reconstructed directly from the compressive measurements by endmember unmixing (CEU) scheme. Compared to 3DTV algorithm, the reconstruction from CEU shows spatial distribution of each component on the surfaces, and demonstrates the ability to characterize the domains of mixed-molecules on surfaces.

A low-cost 3-D hyperspectral projector was built employing a digital micromirror device for spectral and spatial modulated structured light and we demonstrate its utility in recovering multicolor inhomogeneous participating media based on compressive sensing theory.

We propose a silicon-compatible plasmonic electro-optic modulator employing a silicon racetrack ring resonator coupled to a bus waveguide. A silicon-plasmonic hybrid phase shifter clad with electro-optic polymer is introduced to achieve high-speed performance and low energy consumption. Simulations show that the proposed modulator can achieve an extinction ratio of more than 15 dB at 1550-nm wavelength under a 1.2-V bias voltage. The misalignment tolerance and fabrication feasibility of the modulator are also discussed.

A broad-band sum frequency generation microscope has been developed for the study of molecular monolayers on surfaces. Because sum frequency generation is a vibrational spectroscopy based on a second-order optical process, it is uniquely sensitive to detecting a molecule's vibrational fingerprints specifically at interfaces. In this microscope, a structured illumination beam generated by a spatial light modulator is used to irradiate the sample with a series of sparsifying pseudorandom patterns. The spectra associated with each pattern are then input into a reconstruction algorithm to compressively recover the full hyperspectral image cube. As a proof-of-principle, this system performed molecule-specific imaging of a microcontact-printed self-assembled monolayer of alkanethiolate on copper. This hyperspectral compressive imaging effectively recovered both spatial and spectral surface features with compression greater than 80%, meaning more than a 5-fold decrease in acquisition time compared to traditional methods.

We propose and numerically demonstrate an ultrafast real-time ordinary differential equation (ODE) computing unit in optical field based on a silicon microring resonator, operating in the critical coupling region as an optical temporal differentiator. As basic building blocks of a signal processing system, a subtractor and a splitter are included in the proposed structure. This scheme is featured with high speed, compact size and integration on a silicon-on-insulator (SOI) wafer. The size of this computing unit is only 35 μm × 45 μm. In this paper, the performance of the proposed structure is theoretically studied and analyzed by numerical simulations.

A mode-selective grating reflector based on a hybrid plasmonic waveguide, together with a two-to-one coupling structure, is proposed and analyzed. The grating structure is designed to reflect only the fundamental even mode existing in the hybrid plasmonic waveguide, and to pass through the fundamental odd mode at a 1550-nm wavelength with an extinction ratio of ~16.7 dB. The simulated transmission spectra verify our analysis and the expected features of the mode-selective hybrid plasmonic Bragg grating.