C-band operating plasmonic sensor with a high Q-factor/figure of merit based on a silicon nano-ring.

In this paper, we take advantage of the high refractive index property of silicon to design a practical and sensitive plasmonic sensor on a photonic integrated circuit (PIC) platform. It has been demonstrated that a label-free refractive index sensor with sensitivity up to 1124 nm/RIU can be obtained using a simple design of a silicon nano-ring with a concentric hexagonal plasmonic cavity. It has also been shown that, with optimum structural parameters, a quality factor (Q-factor) of 307 and a figure of merit (FOM) of 234 can be achieved, which are approximately 8 times and 5 times higher than the proposed sensors counterparts, respectively.

Microresonator frequency comb based high-speed transmission of intensity modulated direct detection data.

Globally, the long-haul transmission of ultra-high bandwidth data is enabled through coherent communications. Driven by the rapid pace of growth in interconnectivity over the last decade, long-haul data transmission has reached capacities on the order of tens to hundreds of terabits per second, over fiber reaches which may span thousands of kilometers. Data center communications operate in regimes featuring shorter reaches and higher cost sensitivity.

High spectro-temporal compression on a nonlinear CMOS-chip.

Optical pulses are fundamentally defined by their temporal and spectral properties. The ability to control pulse properties allows practitioners to efficiently leverage them for advanced metrology, high speed optical communications and attosecond science. Here, we report 11× temporal compression of 5.

Inverse design of photonic meta-structure for beam collimation in on-chip sensing.

Designed or patterned structured surfaces, metasurfaces, enable the miniaturization of complex arrangements of optical elements on a plane. Most of the existing literature focuses on miniaturizing the optical detection; little attention is directed to on-chip optical excitation. In this work, we design a metasurface to create a planar integrated photonic source beam collimator for use in on-chip optofluidic sensing applications.

Single-Element Diffraction-Limited Fisheye Metalens.

Wide field-of-view (FOV) optical functionality is crucial for implementation of advanced imaging and image projection devices. Conventionally, wide FOV operation is attained with complicated assembly of multiple optical elements known as "fisheye lenses". Here we present a novel metalens design capable of performing diffraction-limited focusing and imaging over an unprecedented near 180° angular FOV.

Chemical Characterization of Aerosol Particles Using On-Chip Photonic Cavity Enhanced Spectroscopy.

We demonstrate the chemical characterization of aerosol particles with on-chip spectroscopy using a photonic cavity enhanced silicon nitride (SiN) racetrack resonator-based sensor. The sensor operates over a broad and continuous wavelength range, showing cavity enhanced sensitivity at specific resonant wavelengths. Analysis of the relative change in the quality factor of the cavity resonances successfully yields the absorption spectrum of the aerosol particles deposited on the resonators.

Loss reduction of silicon-on-insulator waveguides for deep mid-infrared applications.

We report that propagation loss of optical waveguides based on a silicon-on-insulator (SOI) material platform can be greatly reduced. Our simulations show that the loss, including SiO absorption and substrate leakage, but no scattering loss, is 0.024 and 0.

Mid-IR supercontinuum generated in low-dispersion Ge-on-Si waveguides pumped by sub-ps pulses.

Ge-on-Si is an attractive material platform for mid-IR broadband sources on a chip because of its wide transparency window, high Kerr nonlinearity and CMOS compatibility. We present a low-loss Ge-on-Si waveguide with flat and low dispersion from 3 to 11 µm, which enables a coherent supercontinuum from 2 to 12 µm, generated using a sub-ps pulsed pump. We show that 700-fs pump pulses with a low peak power of 400 W are needed to generate such a wide supercontinuum, and the waveguide length is around 5.

Controlling propagation and coupling of waveguide modes using phase-gradient metasurfaces.

Research on two-dimensional designer optical structures, or metasurfaces, has mainly focused on controlling the wavefronts of light propagating in free space. Here, we show that gradient metasurface structures consisting of phased arrays of plasmonic or dielectric nanoantennas can be used to control guided waves via strong optical scattering at subwavelength intervals. Based on this design principle, we experimentally demonstrate waveguide mode converters, polarization rotators and waveguide devices supporting asymmetric optical power transmission.

Gamma radiation effects in amorphous silicon and silicon nitride photonic devices.

Understanding radiation damage is of significant importance for devices operating in radiation-harsh environments. In this Letter, we present a systematic study on gamma radiation effects in amorphous silicon and silicon nitride guided wave devices. It is found that gamma radiation increases the waveguide modal effective indices by as much as 4×10 in amorphous silicon and 5×10 in silicon nitride at 10 Mrad dose.

Nonlinear characterization of GeSbS chalcogenide glass waveguides.

GeSbS ridge waveguides have recently been demonstrated as a promising mid - infrared platform for integrated waveguide - based chemical sensing and photodetection. To date, their nonlinear optical properties remain relatively unexplored. In this paper, we characterize the nonlinear optical properties of GeSbS glasses, and show negligible nonlinear losses at 1.

Gradient Polymer Nanofoams for Encrypted Recording of Chemical Events.

We have fabricated gradient-grafted nanofoam films that are able to record the presence of volatile chemical compounds in an offline regime. In essence, the nanofoam film (100-300 nm thick) is anchored to a surface cross-linked polymer network in a metastable extended configuration that can relax back to a certain degree upon exposure to a chemical vapor. The level of the chain relaxation is associated with thermodynamic affinity between the polymer chains and the volatile compounds.

Nonlinear conversion efficiency in Kerr frequency comb generation.

We analytically and numerically investigate the nonlinear conversion efficiency in ring microresonator-based mode-locked frequency combs under different dispersion conditions. Efficiency is defined as the ratio of the average round trip energy values for the generated pulse(s) to the input pump light. We find that the efficiency degrades with growth of the comb spectral width and is inversely proportional to the number of comb lines.