Optical design of split-beam photonic crystal nanocavities

We design high quality factor photonic crystal nanobeam cavities formed by two mechanically isolated cantilevers. These "split-beam" cavities have a physical gap at the center, allowing mechanical excitations of one or both of the cavity halves. They are designed by analyzing the optical band structures and mode profiles of waveguides perforated by elliptical holes and rectangular gaps, and are predicted to support optical resonances with quality factors exceeding 1E6 at wavelengths of ~ 1.6 um.Comment: To appear in Optics Letter

Cavity optomechanics in gallium phosphide microdisks

We demonstrate gallium phosphide (GaP) microdisk optical cavities with intrinsic quality factors $> 2.8\times10^{5}$ and mode volumes $< 10 (\lambda/n)^3$, and study their nonlinear and optomechanical properties. For optical intensities up to $8.0\times10^4$ intracavity photons, we observe optical loss in the microcavity to decrease with increasing intensity, indicating that saturable absorption sites are present in the GaP material, and that two-photon absorption is not significant. We observe optomechanical coupling between optical modes of the microdisk around 1.5 $\mu$m and several mechanical resonances, and measure an optical spring effect consistent with a theoretically predicted optomechanical coupling rate $g_0/2\pi \sim 30$ kHz for the fundamental mechanical radial breathing mode at 488 MHz.Comment: Published Versio

Origen y variabilidad del recurso hídrico de los principales oasis de la provincia de San Juan

Este trabajo se encuadra en la hidroclimatología aplicada, teniendo como propósito conocer el origen y variabilidad del recurso hídrico que hace posible la existencia de los oasis sanjuaninos. El trabajo tuvo como motivación la última sequía registrada en los Andes Áridos, que repercutió negativamente en la producción agropecuaria y otras actividades socioeconómicas. Se analizan los ríos, con régimen nival de alta montaña, asociados a los oasis de Jáchal-Huaco, Tulum-Ullum-Zonda y secundariamente de Iglesia y Calingasta; la hipótesis es que dicha variabilidad repercute fuertemente en la población por lo que se deben instrumentar políticas que aseguren la regularidad y sustentabilidad de los mismos en el tiempo. Se emplearon métodos estadísticos de correlación lineal, no lineal y de estimación de la tendencia que permitieron detectar y cuantificar la gran variabilidad interanual de los ríos, justificando la construcción de embalses para el óptimo aprovechamiento hídrico y de esa manera instrumentar previsiones sobre su futuro comportamiento. Además se muestra la aplicabilidad de metodologías objetivas para la investigación geográfica.The goal of this study is to know the origin and variability of hidric resources in the main oasis San Juan, having as a frame the applied hydroclimatology. The work was motivated by the recent drought in the Arid Andes and its negative impact on agricultural production and other socioeconomic activities. Rivers with high mountain nival regime, associated with the oasis of Jáchal-Huaco, Ullum-Zonda-Tulum and secondarily of Iglesia and Calingasta are analyzed. The hypothesis is that variability strongly affects the population and, because of this, policies to ensure regularity and sustainability should be implemented. In order to detect and quantify the variability of rivers among years, statistical methods including linear and non-linear correlations and estimation of trends were used. Our results suggest the construction of dams for optimal water use and thereby the forecast implementation forecasts about their future behavior. Furthermore, this study shows the applicability of objective methods for geographical research.Fil: Poblete, Arnobio G.. Universidad Nacional de San JuanFil: Hryciw, Mariela. Universidad Nacional de San Jua

Seismic Downhole, CPT, and DMT Correlations in Sand

Results from seismic cone penetration and dilatometer tests performed in a cohesionless soil are presented and compared with previously published correlations for estimating the elastic shear modulus. Poor correlations were obtained between the elastic shear modulus, the dilatometer modulus and the cone tip resistance; however, somewhat better estimates of the elastic shear modulus were obtained using the coefficient of lateral stress and total unit weight empirically determined from the dilatometer

Nonlinear optomechanical paddle nanocavities

Nonlinear optomechanical coupling is the basis for many potential future experiments in quantum optomechanics (e.g., quantum non-demolition measurements, preparation of non-classical states), which to date have been difficult to realize due to small non-linearity in typical optomechanical devices. Here we introduce an optomechanical system combining strong nonlinear optomechanical coupling, low mass and large optical mode spacing. This nanoscale "paddle nanocavity" supports mechanical resonances with hundreds of fg mass which couple nonlinearly to optical modes with a quadratic optomechanical coupling coefficient $g^{(2)} > 2\pi\times400$ MHz/nm$^2$, and a two phonon to single photon optomechanical coupling rate $\Delta \omega_0 > 2\pi\times 16$ Hz. This coupling relies on strong phonon-photon interactions in a structure whose optical mode spectrum is highly non--degenerate. Nonlinear optomechanical readout of thermally driven motion in these devices should be observable for T $> 50$ mK, and measurement of phonon shot noise is achievable. This shows that strong nonlinear effects can be realized without relying on coupling between nearly degenerate optical modes, thus avoiding parasitic linear coupling present in two mode systems.Comment: 8 pages, 5 figure

Design and experimental demonstration of optomechanical paddle nanocavities

We present the design, fabrication and initial characterization of a paddle nanocavity consisting of a suspended sub-picogram nanomechanical resonator optomechanically coupled to a photonic crystal nanocavity. The optical and mechanical properties of the paddle nanocavity can be systematically designed and optimized, and key characteristics including mechanical frequency easily tailored. Measurements under ambient conditions of a silicon paddle nanocavity demonstrate an optical mode with quality factor $Q_o$ ~ 6000 near 1550 nm, and optomechanical coupling to several mechanical resonances with frequencies $\omega_m/2\pi$ ~ 12-64 MHz, effective masses $m_\text{eff}$ ~ 350-650 fg, and mechanical quality factors $Q_m$ ~ 44-327. Paddle nanocavities are promising for optomechanical sensing and nonlinear optomechanics experiments.Comment: 5 pages, 4 figure

ChatGPT: Force for good in assessment: AI benefits in a large first year human biology assessment task

PROBLEM The advent of open-access AI has created a complex challenge to assessment strategies used in higher education. Concerns associated with academic integrity and potential student use (Crawford et al., 2023; Sullivan et al., 2023) provided an urgent imperative to re-imagine assessment for a large and diverse, first-year Australian Human Biology course. PLAN Redesigned an assessment item to achieve the following: (i) To use AI to develop digital proficiencies but maintain academic integrity (ii) Low stakes early assessment task (iii) Engaging and interesting topic options (iv) Provide flexibility for personal buy-in (v) Incorporate an artistic component (vi) Develop oral and written communication skills (vii) Provide educational support to students that included content concepts, academic integrity and transition-to-university support mechanisms. ACTION The assignment was developed to meet the design brief made of two components. Part 1: Preparation for Interactive Oral Discussion - Students were required to: (i) select an interesting human body fact (ii) use an open-access AI art creation program of their choice to create an artwork that represented their interesting fact and (iii) create a dialogue with ChatGPT to develop a 300-word paragraph. This paragraph needed to clearly articulate the anatomy and physiology of the interesting fact, discuss how the artwork represented the interesting fact, be written to communicate with a general audience and to provide content citation. Students were then provided with a variety of validation methodologies they were required to implement. Part 2: Interactive Oral Discussion - Students engaged in a one-on-one conversation with an academic staff member to provide evidence using examples from their Part 1 submission of how they validated a variety of information. Critical reflection on the positive, negative, and ethical considerations of using open-access AI for university assignments was also required. REFLECTION Students developed a wide skill-base through assessment completion that supported content knowledge, communication capabilities, self-efficacy, adult learner strategies, support resource awareness, academic integrity requirements and digital proficiencies. The opportunity to provide a one-on-one conversation with a university staff member early in their academic journey had surprising benefits from an academic perspective. These included a reduction in the marking time, opportunity to correct misconceptions about how university works and what support resources are available, develop a sense of connection and belonging through normative conversations. REFERENCES Crawford, J., Cowling, M., &amp; Allen, K. (2023). Leadership is needed for ethical ChatGPT: Character, assessment, and learning using artificial intelligence (AI). Journal of University Teaching &amp; Learning Practice, 20(3). https://doi.org/10.53761/1.20.3.02 Sullivan, M., Kelly, A., &amp; McLaughlan, P. (2023). ChatGPT in higher education: Considerations for academic integrity and student learning. Journal of Applied Learning &amp; Teaching, 6(1). https://doi.org/10.37074/jalt.2023.6.1.1

Single crystal diamond nanobeam waveguide optomechanics

Optomechanical devices sensitively transduce and actuate motion of nanomechanical structures using light. Single--crystal diamond promises to improve the performance of optomechanical devices, while also providing opportunities to interface nanomechanics with diamond color center spins and related quantum technologies. Here we demonstrate dissipative waveguide--optomechanical coupling exceeding 35 GHz/nm to diamond nanobeams supporting both optical waveguide modes and mechanical resonances, and use this optomechanical coupling to measure nanobeam displacement with a sensitivity of $9.5$ fm/$\sqrt{\text{Hz}}$ and optical bandwidth $>150$nm. The nanobeams are fabricated from bulk optical grade single--crystal diamond using a scalable undercut etching process, and support mechanical resonances with quality factor $2.5 \times 10^5$ at room temperature, and $7.2 \times 10^5$ in cryogenic conditions (5K). Mechanical self--oscillations, resulting from interplay between photothermal and optomechanical effects, are observed with amplitude exceeding 200 nm for sub-$\mu$W absorbed optical power, demonstrating the potential for optomechanical excitation and manipulation of diamond nanomechanical structures.Comment: Minor changes. Corrected error in units of applied stress in Fig. 1

Generation and Use of Cultured Human Primary Myotubes

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