Physics Program Presents
Summer Research Presentations
Wednesday, September 10, 2014
Hegeman 107
Quantum and Fractional Quantum Hall Effects in Hybrid Graphene
Bard Nanolab, Bard College
By: Andrés Martinez de Velasco, Daniel Waldo, Maya Weingrod Sandor
Bard Nanolab, Bard College
By: Andrés Martinez de Velasco, Daniel Waldo, Maya Weingrod Sandor
Graphene is a two-dimensional allotrope in which the classical Hall Effect exhibits a quantization of available electronic states in the material which produces ballistic--zero resistance--conduction. This can be seen in Hall voltage measurements at high magnetic fields where dips to zero in the transverse resistance and plateaus in the longitudinal resistance appear. This phenomenon is known as the Quantum Hall Effect and requires strong magnetic fields and very low temperatures for its observation. In order to study this phenomenon, samples of graphene on Boron Nitride were fabricated using a variety of techniques and procedures, ultimately yielding samples with various four terminal measurement options available.
Transportation of Ultra-Stable Light via Optical Fiber Laser Interferometer Gravitational-Wave Observatory (LIGO)
California Institute of Technology
By: Emily Conant
California Institute of Technology
By: Emily Conant
It has been demonstrated that polarization-maintaining single mode optical fiber can be used to transport frequency-stable light. It is desired to transport stable light to other labs in the building to serve as a frequency reference for various experiments investigating different sources of noise in gravitational-wave detectors. Stable light has been obtained from ultra-stable Fabry-P'{e}rot cavities by use of the Pound-Drever-Hall locking technique. We have mode matched stable light into the fiber and are using a double-pass acousto-optic modulator (AOM) configuration to cancel fiber phase noise. We use a beamsplitter to interfere the stable light and double passed light onto a photodiode as a homodyne detection, which is connected to a phase-locked loop (PLL) to measure the beat frequency. From there, we analyze the noise in the system by measuring the power spectral density of the PLL control signal with a spectrum analyzer. We have measured the expected dominant sources of noise in the system by using a similar PLL set-up and suppressed them. We cancel the fiber phase noise by locking the optical beat to the signal generator in the PLL.
Characterization of Nanowires for Red LASER on {001} Silicon
Center for Photonics and Multiscale Nanomaterials
University of Michigan
By: Trevor LaMountain
Center for Photonics and Multiscale Nanomaterials
University of Michigan
By: Trevor LaMountain
As technology decreases in size, electronic systems, like those found on a microchip, encounter a scaling problem. The resistance of a current carrying wire is inversely proportional to its cross-sectional area. This large resistance in microelectronic systems leads to slower, less efficient devices. Fortunately, photonics systems, using photons to carry information instead of electrons, do not encounter such scaling problems. It is therefore desirable to replace certain components of microelectronic systems with photonics. However, in order to create such an integrated system, we require a coherent light source (LASER) that can be constructed on the same {001} silicon substrate that modern microchips use. In this talk I discuss the novel methods used to create a red-emitting laser structure on {001} silicon, and in particular highlight the material characterization methods used to measure the composition of alloys used in this device.
For more information, call 845-758-7302, or e-mail [email protected].
Location: Hegeman 107