Solid-state laser refrigeration of a semiconductor optomechanical resonator

Photothermal heating represents a major constraint that limits the performance of many nanoscale optoelectronic and optomechanical devices including nanolasers, quantum optomechanical resonators, and integrated photonic circuits. Although radiation-pressure damping has been reported to cool an individual vibrational mode of an optomechanical resonator to its quantum ground state, to date the internal material temperature within an optomechanical resonator has not been reported to cool via laser excitation. Here we demonstrate the direct laser refrigeration of a semiconductor optomechanical resonator >20K below room temperature based on the emission of upconverted, anti-Stokes photoluminescence of trivalent ytterbium ions doped within a yttrium-lithium-fluoride (YLF) host crystal. Optically-refrigerating the lattice of a dielectric resonator has the potential to impact several fields including scanning probe microscopy, the sensing of weak forces, the measurement of atomic masses, and the development of radiation-balanced solid-state lasers. In addition, optically refrigerated resonators may be used in the future as a promising starting point to perform motional cooling for exploration of quantum effects at mesoscopic length scales,temperature control within integrated photonic devices, and solid-state laser refrigeration of quantum material

Levitated optomechanics: A tutorial and perspective

Optomechanics, the study of the mechanical interaction of light with matter, has proven to be a fruitful area of research that has yielded many notable achievements, including the direct detection of gravitational waves in kilometer-scale optical interferometers. Light has been used to cool and demonstrate quantum control over the mechanical degrees of freedom of individual ions and atoms, and more recently has facilitated the observation of quantum ``mechanics'' in objects of larger mass, even at the kg-scale. Levitated optomechanics, where an object can be suspended by radiation pressure and largely decoupled from its environment, has recently established itself as a rich field of study, with many notable results relevant for precision measurement, quantum information science, and foundational tests of quantum mechanics and fundamental physics. This article provides a survey of several current activities in field along with a tutorial describing associated key concepts and methods, both from an experimental and theoretical approach. It is intended as a resource for junior researchers who are new to this growing field as well as beginning graduate students. The tutorial is concluded with a perspective on both promising emerging experimental platforms and anticipated future theoretical developments.Comment: 50 pages, 19 figures, submitted to Advances in Optics and Photonic

Optical assembly of nanostructures mediated by surface roughness

Rigorous understanding of the self-assembly of colloidal nanocrystals is crucial to the development of tailored nanostructured materials. Despite extensive studies, a mechanistic understanding of self-assembly under non-equilibrium driven by an external field remains an ongoing challenge. We demonstrate self-assembly by optical tweezers imposing an external attractive field for cubic-phase sodium yttrium fluoride nanocrystals. We show that surface roughness of the nanocrystals is a decisive factor for contact leading to assembly between the nanocrystals, manifested by the roughness-dependent hydrodynamic resistivity. This provides direct evidence that dynamics are equally important to energetics in understanding self-assembly. These results have implications in a wide variety of different fields, such as in understanding the factors that mediate oriented attachment-based crystal growth or in interpreting the structure of binding sites on viruses.Comment: 21 pages, 3 main figures, 8 supplemental figures, 2 supplemental videos. Submitted to Physical Review Letter

Epitaxial growth of aligned semiconductor nanowire metamaterials for photonic applications

A novel class of optical metamaterials is presented consisting of high densities of aligned gallium phosphide (GaP) nanowires fabricated using metal-organic vapor phase-epitaxy. Starting from a gold island film as a catalyst for nanowire growth, a sequential combination of vapor-liquid-solid and lateral growth modes is employed to obtain a continuous tunability of the nanowire volume fraction from 7% to over 35%. By choosing different crystallographic orientations of the GaP substrate, metamaterials are designed with different nanowire orientations. The anisotropy of the nanowire building blocks results in strong optical birefringence. Polarization interferometry demonstrates a very large polarization extinction contrast of 4 × 103 combined with a sharp angular resonance which holds promise for optical sensing. Nanowire metamaterials may find applications in photonics, optoelectronics, non-linear and quantum optics, microfluidics, bio-, and gas sensing

Nanowire assembly, e.g. for optical probes, comprises optically trapping high aspect ratio semiconductor nanowire with infrared single-beam optical trap and attaching nanowire to organic or inorganic structure

NOVELTY - A nanowire assembly method comprises optically trapping a semiconductor nanowire with an infrared single-beam optical trap and attaching the nanowire to an organic or inorganic structure by laser fusing. The nanowire is further trapped in a fluid environment. The optical trap has a beam wavelength of 1064 nm. The nanowire has an aspect ratio greater than 100 and a diameter less than 100 (preferably less than 80) nm. The nanowire and the organic or inorganic structure form a heterostructure. USE - For fabricating a nanowire assembly for use as e.g. active photonic devices, passive photonic devices, optical probes, subwavelength microscopy. ADVANTAGE - Nanowires with diameters as small as 20 nm and aspect ratios of above one hundred can be trapped and transported in three dimensions, enabling the construction of nanowire architectures which may function in various capacities. Nanowire structures can now be assembled in physiological environments, offering new forms of chemical, mechanical and optical stimulation of living cells. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a nanowire assembly comprising a nanowire and an organic or inorganic structure or an arbitrary structure. DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of an optical tweezers instrument for nanowire trapping

Influence of the sonication temperature on the debundling kinetics of carbon nanotubes in Propan-2-ol

The effect of sonication temperature on the debundling of carbon nanotube (CNT) macro-bundles is reported and demonstrated by analysis with different particle sizing methods. The change of bundle size over time and after several comparatively gentle sonication cycles of suspensions at various temperatures is reported. A novel technique is presented that produces a more homogeneous nanotube dispersion by lowering the temperature during sonication. We produce evidence that temperature influences the suspension stability, and that low temperatures are preferable to obtain better dispersion without increasing damage to the CNT walls