Nanomechanical oscillators are at the heart of ultrasensitive detectors of force, mass and motion. As these detectors progress to even better sensitivity, they will encounter measurement limits imposed by the laws of quantum mechanics. If the imprecision of a measurement of the displacement of an oscillator is pushed below a scale set by the standard quantum limit, the measurement must perturb the motion of the oscillator by an amount larger than that scale. Here we show a displacement measurement with an imprecision below the standard quantum limit scale. We achieve this imprecision by measuring the motion of a nanomechanical oscillator with a nearly shot-noise limited microwave interferometer. As the interferometer is naturally operated at cryogenic temperatures, the thermal motion of the oscillator is minimized, yielding an excellent force detector with a sensitivity of 0.51 aN Hz(-1/2). This measurement is a critical step towards observing quantum behaviour in a mechanical object.

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Nanomechanical motion measured with an imprecision below the standard quantum limit

Silicon photonics has experienced phenomenal transformations over the last decade. In this paper, we present some of the notable advances in silicon-based passive and active optical interconnect components, and highlight some of our key contributions. Light is also cast on few other parallel technologies that are working in tandem with silicon-based structures, and providing unique functions not achievable with any single system acting alone. With an increasing utilization of CMOS foundries for silicon photonics fabrication, a viable path for realizing extremely low-cost integrated optoelectronics has been paved. These advances are expected to benefit several application domains in the years to come, including communication networks, sensing, and nonlinear systems.

Recent advances in silicon-based passive and active optical interconnects

Light-emitting electrospun (ES) nanofibers with diameters of 250−750 nm were successfully prepared through the binary blends of polyfluorene derivative/poly(methyl methacrylate) (PMMA) using a single-capillary spinneret. The studied poly(fluorene)s included poly(9,9-dioctylfluoreny-2,7-diyl) (PFO), poly[2,7-(9,9-dihexylfluorene)-alt-5,8-quinoxaline] (PFQ), poly[2,7-(9,9-dihexylfluorene)-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT), and poly[2,7-(9,9-dihexylfluorene)-alt-5,7-(thieno[3,4-b]pyrazine)] (PFTP). The transmission electron microscopy (TEM) studies showed that uncontinuous fiberlike structure was obtained at the low PFO/PMMA blend ratio but became a core−shell structure at a high PFO blend ratio. The poorer solubility of PFO in chloroform than that of PMMA probably forced it to be solidified first as the fiber core. Besides, a porous surface structure on the PFO/PMMA blend fibers was observed due to the rapid evaporation of the chloroform solvent. The PFO aggregation domain in the ES fibers was much s...

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Morphology and Photophysical Properties of Light-Emitting Electrospun Nanofibers Prepared from Poly(fluorene) Derivative/PMMA Blends

Light‐Emitting Electrospun Nanofibers for Nanophotonics and Optoelectronics

Traditional electrospun nanofibers have a myriad of applications ranging from scaffolds for tissue engineering to components of biosensors and energy harvesting devices. The generally smooth one-dimensional structure of the fibers has stood as a limitation to several interesting novel applications. Control of fiber diameter, porosity and collector geometry will be briefly discussed, as will more traditional methods for controlling fiber morphology and fiber mat architecture. The remainder of the review will focus on new techniques to prepare hierarchically structured fibers. Fibers with hierarchical primary structures—including helical, buckled, and beads-on-a-string fibers, as well as fibers with secondary structures, such as nanopores, nanopillars, nanorods, and internally structured fibers and their applications—will be discussed. These new materials with helical/buckled morphology are expected to possess unique optical and mechanical properties with possible applications for negative refractive index materials, highly stretchable/high-tensile-strength materials, and components in microelectromechanical devices. Core-shell type fibers enable a much wider variety of materials to be electrospun and are expected to be widely applied in the sensing, drug delivery/controlled release fields, and in the encapsulation of live cells for biological applications. Materials with a hierarchical secondary structure are expected to provide new superhydrophobic and self-cleaning materials.

https://www.mdpi.com/2073-4360/5/1/19/pdf

Hierarchically Structured Electrospun Fibers

Highly fluorescent nanofibers were prepared by electrospinning the solutions containing poly(p-phenylene vinylene) (PPV) precursor and poly(vinyl pyrrolidone), followed by thermal conversion. Different morphologies from uniform helical to ultrathin straight ones were controllably prepared by adjusting the amount of PPV precursor in electrospinning solutions. The experimental data suggest that the viscosity and conductivity of electrospinning solution and the operating voltage are the main factors that affect the formation of the helical structures. These different nanofiber morphologies may be advantageous depending on the applications.

Controlling poly(p-phenylene vinylene)/poly(vinyl pyrrolidone) composite nanofibers in different morphologies by electrospinning

An optomechanical crystal nanobeam cavity, only by increasing the radius of air holes in the defect region, is proposed and optimized for a high optomechanical coupling rate. In our proposed cavity, the photonic and phononic defect modes are simultaneously confined by each corresponding bandgap, and the overlap of the optical and mechanical modes can be improved simply by adjusting the radius of the air holes. Accordingly, an optomechanical coupling rate (g) as high as 1.16 MHz is obtained, which is the highest coupling rate among the reported optomechanical crystal cavities. What’s more, the proposed cavity also exhibits a high mechanical frequency of 4.01 GHz and a small effective mass of 85 fg for the fundamental mechanical mode.

http://iopscience.iop.org/article/10.1088/2040-8978/17/4/045001/pdf

Optomechanical crystal nanobeam cavity with high optomechanical coupling rate

Nanobeam cavities based on hetero optomechanical crystals are proposed. With optical and mechanical modes separately confined by two types of periodic structures, the mechanical frequency is designed as high as 5.88 GHz. Due to the optical field and the strain field concentrated in the optomechanical cavity and resembling each other with an enhanced overlap, a high optomechanical coupling rate of 1.31 MHz is predicted.

/pdf/strong-optomechanical-coupling-in-nanobeam-cavities-based-on-3yoih087ok.pdf

Strong Optomechanical Coupling in Nanobeam Cavities based on Hetero Optomechanical Crystals.

A compact thermo-optic switch based on the cutoff effect of slow-light mode of a tapered W1 photonic crystal waveguide (PCW) is demonstrated with an integrated microheater. Due to the low-group-index taper, the coupling loss of the slow-light PCW is reduced, and a high switching extinction ratio (ER) is attained. Moreover, three types of microheaters are evaluated for the power consumptions, heating transfer efficiency, and temperature uniformities, and an optimized slab microheater is utilized. As a result, low switching power of 8.9 mW and high ER of 23.5 dB are achieved experimentally, while the length of W1 PCW is only 16.8 μm.

Compact Thermo-Optic Switch Based on Tapered W1 Photonic Crystal Waveguide

Optomechanical crystals have attracted great attention recently for their ability to realize strong photon-phonon interaction in cavity optomechanical systems. By far, the operation of cavity optomechanical systems with high mechanical frequency has to employ tapered fibres or one-sided waveguides with circulators to couple the light into and out of the cavities, which hinders their on-chip applications. Here, we demonstrate larger-centre-hole nanobeam structures with on-chip transmission-coupling waveguide. The measured mechanical frequency is up to 4.47 GHz, with a high mechanical Q-factor of 1.4 × 103 in the ambient environment. The corresponding optomechanical coupling rate is calculated and measured to be 836 kHz and 1.2 MHz, respectively, while the effective mass is estimated to be 136 fg. With the transmission waveguide coupled structure and a small footprint of 3.4 μm2, this simple cavity can be directly used as functional components or integrated with other on-chip devices in future practical applications.

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Zhilei Huang

Papers

Controlling poly(p-phenylene vinylene)/poly(vinyl pyrrolidone) composite nanofibers in different morphologies by electrospinning

Optomechanical crystal nanobeam cavity with high optomechanical coupling rate

Strong Optomechanical Coupling in Nanobeam Cavities based on Hetero Optomechanical Crystals.

Compact Thermo-Optic Switch Based on Tapered W1 Photonic Crystal Waveguide

High-mechanical-frequency characteristics of optomechanical crystal cavity with coupling waveguide.