Achromatic nulling beam combiner for the detection of extrasolar planets

Persistent Link:
http://hdl.handle.net/10150/279844
Title:
Achromatic nulling beam combiner for the detection of extrasolar planets
Author:
Morgan, Rhonda Michelle
Issue Date:
2001
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Nulling stellar interferometry may enable the discovery of earth-like planets around other stars. In nulling mode, the zero order fringe is destructive and on axis, thus canceling light from a bright source and detecting dimer off-axis features. To create deep on-axis nulls, the phase must be shifted half a wave achromatically over a broad band. The phase shift is created by adding optical path thickness with dielectric plates. Plates of different materials can balance dispersion. The nulling solutions found for TPF (infrared) and for SIM (visible) are promising. This dissertation describes the implementation of a nulling beam combiner test bed and presents data characterizing its performance. Although the implementation was limited so that a broad band null of 10E-4 was not attained, the test bed revealed the extreme challenges of this technique and provided very valuable lessons that will enable future implementations to be successful and more precise. The nulling beam combiner testbed was implemented in the laboratory as a Michelson interferometer with the goal of achieving a stabilized, l0E-4 null over a spectral region from 600 nm to 800 nm. The beam combiner system has three tiers of control. Tier 1 controls phase achromaticity by tilting optical plates and is a static control loop. Tier 2 sweeps through the white light fringe and then searches for the null as the air path drifts over minutes. Tier 3 stabilizes the null with a 300 hertz servo loop. A scheme for active control of the optical thicknesses was developed. The phase as a function of wavelength was measured by performing PSI on a spectrally dispersed fringe. The phase was fit to a model to solve for the optical thicknesses. The optical thicknesses were then adjusted to match the ideal thicknesses of an optimized solution. This process of measuring and adjusting the optical thicknesses is performed iteratively to achromatize the phase. The stabilizing servo loop sensed on a grey fringe at a short wavelength. At the shorter wavelength, the fringe was 90 degrees out of phase with the main pass band resulting in a grey fringe. The grey fringe intensity is more sensitive to OPD changes.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Physics, Astronomy and Astrophysics.; Physics, Optics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Optical Sciences
Degree Grantor:
University of Arizona
Advisor:
Burge, James H.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleAchromatic nulling beam combiner for the detection of extrasolar planetsen_US
dc.creatorMorgan, Rhonda Michelleen_US
dc.contributor.authorMorgan, Rhonda Michelleen_US
dc.date.issued2001en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractNulling stellar interferometry may enable the discovery of earth-like planets around other stars. In nulling mode, the zero order fringe is destructive and on axis, thus canceling light from a bright source and detecting dimer off-axis features. To create deep on-axis nulls, the phase must be shifted half a wave achromatically over a broad band. The phase shift is created by adding optical path thickness with dielectric plates. Plates of different materials can balance dispersion. The nulling solutions found for TPF (infrared) and for SIM (visible) are promising. This dissertation describes the implementation of a nulling beam combiner test bed and presents data characterizing its performance. Although the implementation was limited so that a broad band null of 10E-4 was not attained, the test bed revealed the extreme challenges of this technique and provided very valuable lessons that will enable future implementations to be successful and more precise. The nulling beam combiner testbed was implemented in the laboratory as a Michelson interferometer with the goal of achieving a stabilized, l0E-4 null over a spectral region from 600 nm to 800 nm. The beam combiner system has three tiers of control. Tier 1 controls phase achromaticity by tilting optical plates and is a static control loop. Tier 2 sweeps through the white light fringe and then searches for the null as the air path drifts over minutes. Tier 3 stabilizes the null with a 300 hertz servo loop. A scheme for active control of the optical thicknesses was developed. The phase as a function of wavelength was measured by performing PSI on a spectrally dispersed fringe. The phase was fit to a model to solve for the optical thicknesses. The optical thicknesses were then adjusted to match the ideal thicknesses of an optimized solution. This process of measuring and adjusting the optical thicknesses is performed iteratively to achromatize the phase. The stabilizing servo loop sensed on a grey fringe at a short wavelength. At the shorter wavelength, the fringe was 90 degrees out of phase with the main pass band resulting in a grey fringe. The grey fringe intensity is more sensitive to OPD changes.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectPhysics, Astronomy and Astrophysics.en_US
dc.subjectPhysics, Optics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineOptical Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBurge, James H.en_US
dc.identifier.proquest3031349en_US
dc.identifier.bibrecord.b42283103en_US
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