Laser spot position dependent photothermal mode cooling of a micro-cantilever

We explore the laser spot position (LSP) dependent photothermal mode cooling of a micro-cantilever in a Fabry-P\'erot (FP) cavity. Depending on the LSP along the lever, photothermal coupling to the first two mechanical modes can be either parallel or anti-parallel. This LSP dependent behavior is analyzed theoretically by a simple model, which is in quantitatively agreement with our experimental observation. From simulation, the parallel and anti-parallel coupling region is identified along the lever. We conclude that a more efficient mode cooling may be achieved in the parallel coupling region.Comment: 4 pages, 4 figure

The Maunakea Spectroscopic Explorer Book 2018

(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is intended as a concise reference guide to all aspects of the scientific and technical design of MSE, for the international astronomy and engineering communities, and related agencies. The current version is a status report of MSE's science goals and their practical implementation, following the System Conceptual Design Review, held in January 2018. MSE is a planned 10-m class, wide-field, optical and near-infrared facility, designed to enable transformative science, while filling a critical missing gap in the emerging international network of large-scale astronomical facilities. MSE is completely dedicated to multi-object spectroscopy of samples of between thousands and millions of astrophysical objects. It will lead the world in this arena, due to its unique design capabilities: it will boast a large (11.25 m) aperture and wide (1.52 sq. degree) field of view; it will have the capabilities to observe at a wide range of spectral resolutions, from R2500 to R40,000, with massive multiplexing (4332 spectra per exposure, with all spectral resolutions available at all times), and an on-target observing efficiency of more than 80%. MSE will unveil the composition and dynamics of the faint Universe and is designed to excel at precision studies of faint astrophysical phenomena. It will also provide critical follow-up for multi-wavelength imaging surveys, such as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation Very Large Array.Comment: 5 chapters, 160 pages, 107 figure

Material discrimination and mixture ratio estimation in nanocomposites via harmonic atomic force microscopy

Harmonic atomic force microscopy (AFM) was employed to discriminate between different materials and to estimate the mixture ratio of the constituent components in nanocomposites. The major influencing factors, namely amplitude feedback set-point, drive frequency and laser spot position along the cantilever beam, were systematically investigated. Employing different set-points induces alternation of tip–sample interaction forces and thus different harmonic responses. The numerical simulations of the cantilever dynamics were well-correlated with the experimental observations. Owing to the deviation of the drive frequency from the fundamental resonance, harmonic amplitude contrast reversal may occur. It was also found that the laser spot position affects the harmonic signal strengths as expected. Based on these investigations, harmonic AFM was employed to identify material components and estimate the mixture ratio in multicomponent materials. The composite samples are composed of different kinds of nanoparticles with almost the same shape and size. Higher harmonic imaging offers better information on the distribution and mixture of different nanoparticles as compared to other techniques, including topography and conventional tapping phase. Therefore, harmonic AFM has potential applications in various fields of nanoscience and nanotechnology

Plasmonic Multibowtie Aperture Antenna with Fano Resonance for Nanoscale Spectral Sorting

In this work we report a new type of nanostructure, the plasmonic multibowtie aperture antenna with Fano resonance for spectral sorting at the nanoscale. Redistribution of surface current in our device plays a critical role in mode coupling to generate Fano resonance, which has never been carefully discussed before. Numerical analyses show that interactions of the electric field, the surface current, and the resulting magnetic field are all important for achieving the desired spectral sorting. Depending on the constructive or destructive interference between the broadband dipole mode and the narrow band multipole mode, electric near-field amplitude and phase distributions switch dramatically across the Fano resonance, which are observed in real space using transmission-type s-SNOM. Based on the Fano interference, photons ranging from visible to infrared spectrum can be sorted through different channels at the nanoscale according to their wavelengths, which shows apparent advantages over other existing nanoscale spectral sorters. Moreover, the narrow gap plasmonic bowtie aperture provides enhanced field of the sorted photons, thus, offers a new approach for multicolor photodetection, optical filtering, and advanced biosensing

Maskless Surface Modification of Polyurethane Films by an Atmospheric Pressure He/O2 Plasma Microjet for Gelatin Immobilization

A localized maskless modification method of polyurethane (PU) films through an atmospheric pressure He/O2 plasma microjet (APPμJ) was proposed. The APPμJ system combines an atmospheric pressure plasma jet (APPJ) with a microfabricated silicon micronozzle with dimension of 30 μm, which has advantages of simple structure and low cost. The possibility of APPμJ in functionalizing PU films with hydroxyl (–OH) groups and covalent grafting of gelatin for improving its biocompatibility was demonstrated. The morphologies and chemical compositions of the modified surface were analyzed by scanning electronic microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The fluorescent images show the modified surface can be divided into four areas with different fluorescence intensity from the center to the outside domain. The distribution of the rings could be controlled by plasma process parameters, such as the treatment time and the flow rate of O2. When the treatment time is 4 to 5 min with the oxygen percentage of 0.6%, the PU film can be effectively local functionalized with the diameter of 170 μm. In addition, the modification mechanism of PU films by the APPμJ is investigated. The localized polymer modified by APPμJ has potential applications in the field of tissue engineering

Numerical and Experimental Study of the Structural Color by Widening the Pore Size of Nanoporous Anodic Alumina

The structural color originated from the nanoporous anodic alumina (NAA) film is related to the structural characteristics. This paper aimed to obtain different structural colors which can cover the whole visible range by widening the pore size of metal-coated NAA. First, we used the Finite Difference Time Domain (FDTD) method to analyze the relationship between the physical structure and optical properties. Then, we fabricated different colors and expected color pattern by widening the pore diameter of NAA. Numerical and experimental study shows that the colors can cover the whole visible range by widening the pore diameter. This work can not only lead to better understanding of the mechanism of tuning color on NAA film, but also help us to fabricate expected color in the whole light range

Separated Type Atmospheric Pressure Plasma Microjets Array for Maskless Microscale Etching

Maskless etching approaches such as microdischarges and atmospheric pressure plasma jets (APPJs) have been studied recently. Nonetheless, a simple, long lifetime, and efficient maskless etching method is still a challenge. In this work, a separated type maskless etching system based on atmospheric pressure He/O2 plasma jet and microfabricated Micro Electro Mechanical Systems (MEMS) nozzle have been developed with advantages of simple-structure, flexibility, and parallel processing capacity. The plasma was generated in the glass tube, forming the micron level plasma jet between the nozzle and the surface of polymer. The plasma microjet was capable of removing photoresist without masks since it contains oxygen reactive species verified by spectra measurement. The experimental results illustrated that different features of microholes etched by plasma microjet could be achieved by controlling the distance between the nozzle and the substrate, additive oxygen ratio, and etch time, the result of which is consistent with the analysis result of plasma spectra. In addition, a parallel etching process was also realized by plasma microjets array

Bridged Bowtie Aperture Antenna for Producing an Electromagnetic Hot Spot

In this work we report a new type of nanostructure, the bridged bowtie aperture (BBA) antenna, for producing a simultaneously enhanced and confined electric and magnetic near field. The optical nanocircuit theory is employed to reveal its underlying mechanism. The electric near-field distribution of the nanostructure is observed using transmission-type s-SNOM at the nanoscale, and the magnetic near-field distribution is then derived from the electric near field of a complementary BBA structure using Babinet’s principle. To our knowledge, the generation of such an electromagnetic hot spot has never been experimentally demonstrated. Relative to the existing nanostructures that can produce an electromagnetic hot spot, the BBA antenna has apparent advantages, which offers a new approach for nonlinear optics, surface-enhanced spectroscopy, biosensing, and metamaterials