1,250 research outputs found
Compact cavity-dumped Q-switched Er: YAG laser
Published 13 September 2016Abstract not availableLachlan Harris, Myles Clark, Peter Veitch, and David Ottawa
Measurement of radiation-pressure-induced optomechanical dynamics in a suspended Fabry-Perot cavity
We report on experimental observation of radiation-pressure induced effects
in a high-power optical cavity. These effects play an important role in next
generation gravitational wave (GW) detectors, as well as in quantum
non-demolition (QND) interferometers. We measure the properties of an optical
spring, created by coupling of an intense laser field to the pendulum mode of a
suspended mirror; and also the parametric instability (PI) that arises from the
nonlinear coupling between acoustic modes of the cavity mirrors and the cavity
optical mode. Specifically, we measure an optical rigidity of N/m, and PI value .Comment: 4 pages, 3 figure
A squeezed state source using radiation pressure induced rigidity
We propose an experiment to extract ponderomotive squeezing from an
interferometer with high circulating power and low mass mirrors. In this
interferometer, optical resonances of the arm cavities are detuned from the
laser frequency, creating a mechanical rigidity that dramatically suppresses
displacement noise. After taking into account imperfection of optical elements,
laser noise, and other technical noise consistent with existing laser and
optical technologies and typical laboratory environments, we expect the output
light from the interferometer to have measurable squeezing of ~5 dB, with a
frequency-independent squeeze angle for frequencies below 1 kHz. This squeeze
source is well suited for injection into a gravitational-wave interferometer,
leading to improved sensitivity from reduction in the quantum noise.
Furthermore, this design provides an experimental test of quantum-limited
radiation pressure effects, which have not previously been tested.Comment: 15 pages, 6 figures, submitted to Phys. Rev.
The Melanocortin-4 Receptor Integrates Circadian Light Cues and Metabolism
The melanocortin system directs diverse physiological functions from coat color to body weight homoeostasis. A commonality among melanocortin-mediated processes is that many animals modulate similar processes on a circannual basis in response to longer, summer days, suggesting an underlying link between circadian biology and the melanocortin system. Despite key neuroanatomical substrates shared by both circadian and melanocortin-signaling pathways, little is known about the relationship between the two. Here we identify a link between circadian disruption and the control of glucose homeostasis mediated through the melanocortin-4 receptor (Mc4r). Mc4r-deficient mice exhibit exaggerated circadian fluctuations in baseline blood glucose and glucose tolerance. Interestingly, exposure to lighting conditions that disrupt circadian rhythms improve their glucose tolerance. This improvement occurs through an increase in glucose clearance by skeletal muscle and is food intake and body weight independent. Restoring Mc4r expression to the paraventricular nucleus prevents the improvement in glucose tolerance, supporting a role for the paraventricular nucleus in the integration of circadian light cues and metabolism. Altogether these data suggest that Mc4r signaling plays a protective role in minimizing glucose fluctuations due to circadian rhythms and environmental light cues and demonstrate a previously undiscovered connection between circadian biology and glucose metabolism mediated through the melanocortin system
Power scalable TEM(oo) CW Nd: YAG laser with thermal lens compensation
We present finite-element analyzes and experimental results to validate our approach for building high-power single-mode Nd:YAG lasers. We show that the thermooptical and thermomechanical properties of a slab laser can be controlled. This is essential for the use of the proposed unstable resonator. We include demonstration of an efficient subscale laser operating at 20 W TEM00.D. Mudge, M. Ostermeyer, P. J. Veitch, J. Munch, B. Middlemiss, D. J. Ottaway and M. W. Hamilto
Stabilization of injection-locked lasers using spatial mode interference
We report the use of spatial-mode-interference, or tilt-locking, for the active stabilization of injection-locking of a Nd:YAG laser. We show that this control scheme is robust and adds negligible frequency noise to the injection-locked laserOttaway, D.J.; Gray, M.B.; Shaddock, D.A.; Hollitt, C.; Veitch, P.J.; Munch, J.; McClelland, David Ernes
Short-pulse actively Q-switched Er:YAG lasers
Published 28 Jun 2016Abstract not availableDavid J Ottaway, Lachlan Harris, and Peter J. Veitc
Investigating the Essential of Meaningful Automated Formative Feedback for Programming Assignments
This study investigated the essential of meaningful automated feedback for
programming assignments. Three different types of feedback were tested,
including (a) What's wrong - what test cases were testing and which failed, (b)
Gap - comparisons between expected and actual outputs, and (c) Hint - hints on
how to fix problems if test cases failed. 46 students taking a CS2 participated
in this study. They were divided into three groups, and the feedback
configurations for each group were different: (1) Group One - What's wrong, (2)
Group Two - What's wrong + Gap, (3) Group Three - What's wrong + Gap + Hint.
This study found that simply knowing what failed did not help students
sufficiently, and might stimulate system gaming behavior. Hints were not found
to be impactful on student performance or their usage of automated feedback.
Based on the findings, this study provides practical guidance on the design of
automated feedback
Cryogenic, conduction cooled, end pumped, zigzag slab laser, suitable for power scaling
Thermo mechanical and thermo optical properties of Yb:YAG improve significantly at cryogenic temperatures. We present the first end pumped, zigzag slab Yb:YAG geometry, which is cryogenically conduction cooled, robust, and power scalable. © OSA 2012.M. Ganija, D. Ottaway, P. Veitch, and J. Munc
Modeling thermoelastic distortion of optics using elastodynamic reciprocity
Thermoelastic distortion resulting from optical absorption by transmissive and reflective optics can cause unacceptable changes in optical systems that employ high-power beams. In advanced-generation laser-interferometric gravitational wave detectors, for example, optical absorption is expected to result in wavefront distortions that would compromise the sensitivity of the detector, thus necessitating the use of adaptive thermal compensation. Unfortunately, these systems have long thermal time constants, and so predictive feed-forward control systems could be required, but the finite-element analysis is computationally expensive. We describe here the use of the Betti-Maxwell elastodynamic reciprocity theorem to calculate the response of linear elastic bodies (optics) to heating that has arbitrary spatial distribution. We demonstrate, using a simple example, that it can yield accurate results in computational times that are significantly less than those required for finite-element analyses.Eleanor King, Yuri Levin, David Ottaway, and Peter Veitc
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