PhD Physics Dissertation Defense: Fluid-enhanced tunable diffraction with elastomer grating by Caironesa Pada

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The Department of Physics of Ateneo de Manila University cordially invites you to a Physics Dissertation Defense:

  • Student name: Caironesa Pada
  • Dissertation title: FLUID-ENHANCED TUNABLE DIFFRACTION WITH AN ELASTOMER GRATING
  • Schedule and venue: 10 May 2017, 4 PM, F-106

DISSERTATION PANEL

  • Dr. Raphael A. Guerrero (Physics), Dissertation Adviser
  • Dr. Percival F. Almoro (UPD), Dissertation Examiner
  • Dr. James Bernard Simpas (Physics), Dissertation Examiner
  • Dr. Maria Obiminda Cambaliza (Physics), Dissertation Reader
  • Dr. Christian Lorenz Mahinay (Physics), Dissertation Reader

ABSTRACT

A tunable diffraction grating shows promise in applications from beam steering to spectroscopy due to the versatility of its design. A diffraction grating made of polydimethylsiloxane (PDMS) is replicated using simple soft lithography. Tunable diffraction is accomplished by modifying groove spacing through the application of strain on the elastomeric grating replica. The range of strain-variable diffraction angles is extended by adding a refracting liquid layer to the grating. The scanning of the 1st-order diffraction angles as the grating pitch is tuned is demonstrated when the grating operates in transmission and reflection mode. In transmission mode, using a water layer, the diffraction angle is tuned from 38o to 33.4o with an applied strain of 17.7%. With an equal amount of strain, adding a glycerol layer results in the diffraction angle varying from 38.8o to 34.4o. When the grating operates in reflection mode, with a water layer, effective diffraction angle is 24.85o with 8.86% strain. This is equivalent to the output at an applied mechanical strain of 12.8% of an unmodified grating. The addition of glycerol as a refracting element to the tunable grating yields 27.8o with an applied strain of 8.86%. Without glycerol, this angle can be achieved at a strain level of approximately 14.76%. The addition of liquid layer proves an efficient way to extend the range of the 1st-order diffraction output. The experimental results are accurately described by the combined effects of diffraction by a deformable grating and refraction by a fluid with a curved surface.