The ability to control light propagation in photonic integrated circuits is at the foundation of modern light-based communication. However, the inherent crosstalk in densely packed waveguides and the lack of robust control of the coupling are a major roadblock toward ultra-high density photonic integrated circuits. As a result, the diffraction limit is often considered as the lower bound for ultra-dense silicon photonics circuits. Here we experimentally demonstrate an active control of the coupling between two closely packed waveguides via the interaction with a decoupled waveguide. This control scheme is analogous to the adiabatic elimination, a well-known procedure in atomic physics. This approach offers an attractive solution for ultra-dense integrated nanophotonics for light-based communications and integrated quantum computing.

We used SU-8 shrinkage to fabricate strained graphene resonators to produce a high quality factor in a graphene resonator. A-few-layer graphene resonators were fabricated on a trench of an SU-8 resist. These resonators were clamped with diamond-like carbon (DLC), which was deposited by using focused-ion-beam chemical vapor deposition (FIB-CVD), and trimmed by using FIB etching. Annealing was used to apply tensile strain to the graphene resonators because SU-8 shrinks drastically. We also observed an increase in resonant frequency and quality factor in these graphene resonators after annealing. At room temperature, the quality factor of the best sample exceeded 7,000 for a resonator length of 10 µm.

Mid-infrared light provides numerous unexpected opportunities in scientific discoveries because this wavelength region covers the fingerprints of various molecular vibrational resonances. However, the light generation efficiency and bandwidth have been a long-standing bottleneck which has limited the development so far. Moreover, the light source that can be integrated with other components such as wavelength filters, detectors, and electronics, will be the key factor toward the future practical applications. Here, we propose an all-air-cladding silicon-rib waveguide to experimentally reveal the nonlinear performance of supercontinuum generation. By tuning the waveguide dispersion parameters with simulation, a continuous broad spectrum of 1.32 octave (2-5 μm) was observed with a pump pulse wavelength of 4 μm. To further investigate our device characteristics, multiple conditions were set by varying the interaction length, pump power, and waveguide dimension, which revealed the nonlinear phenomenon in the waveguide.

We demonstrate a sensitive method for the nonlinear optical characterization of micrometer long waveguides, and apply it to typical silicon-on-insulator nanowires and to hybrid plasmonic waveguides. We demonstrate that our method can detect extremely small nonlinear phase shifts, as low as 7.5·10<(-4) rad. The high sensitivity achieved imparts an advantage when investigating the nonlinear behavior of metallic structures as their short propagation distances complicates the task for conventional methods. Our results constitute the first experimental observation of χ((3)) nonlinearities in the hybrid plasmonic platform and is important to test claims of hybrid plasmonic structures as candidates for efficient nonlinear optical devices.

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On-chip optical data processing and photonic quantum integrated circuits require the integration of densely packed directional couplers at the nanoscale. However, the inherent evanescent coupling at this length scale severely limits the compactness of such on-chip photonic circuits. Here, inspired by the adiabatic elimination in a N-level atomic system, we report an experimental realization of a pair of directional couplers that are effectively isolated from each other despite their subwavelength packing. This approach opens the way to ultradense arrays of waveguide couplers for integrated optical and quantum logic gates.

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An ultra-thin carbon nanomechanical resonator was fabricated from poly(methyl methacrylate) (PMMA) using focused-ion-beam (FIB) and electron-beam dual-beam lithography. A suspended PMMA structure was cured using an ion-beam modification technique using a 30-kV Ga+ FIB, and carbonized to a diamondlike carbon. In addition, we analyzed the vibrational properties of the cured PMMA nanowire to confirm that it functioned as a resonant structure.