Cluster model of polarization upon reflection from metallic surfaces.

78 Pages·1 MB·en_US

by  Baldwin, Craig Wesley.;Biblarz, Oscar.

NAVAL POSTGRADUATE SCHOOL
Monterey, California
THESIS
CLUSTER MODEL OF
POLARIZATION UPON REFLECTION
FROM METALLIC SURFACES
by
CraigWesley Baldwin
December, 1991
Thesis Advisor: Oscar Biblarz
Approved for public release; distribution is unlimited
T257812

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11 TITLE(IncludeSecurityClassification)
CLUSTERMODELOFPOLARIZATION UPONREFLECTIONFROM METALLICSURFACES(UNCLASSIFIED)
12.PERSONALAUTHOR(S) CraigW.Baldwin,LCDR,USN
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Master'sThesis From To December,1991 69
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17.COSATICODES 18 SUBJECTTERMS(continueonreverseifnecessaryandidentifybyblocknumber)
FIELD GROUP SUBGROUP MetallicClusters MetallicReflectors MicroParticles FiniteSystems
Polarization
19 ABSTRACT(continueonreverseifnecessaryandidentifybyblocknumber)
POLARIZATIONOFLIGHTISAT BESTONLYPARTIALLYEXPLAINEDBYCURRENT MODELS. ANEWMODELISPROPOSEDTO
ACCOUNTFORTHISPHENOMONENINVOLVING"NATIVECLUSTERS".THESECLUSTERSAREASSUMEDTOBEAN INTEGRAL
PARTOFSOMEBULKSURFACESANDTOMANIFESTTHEIRDIELECTRICPROPERTIESINTHEVISIBLEREGION. AN INDEXOF
REFRACTION MAYBECOMPUTEDBASEDON APSEUDO-BREWSTERANGLE,THATANGLEOFINCIDENCEWHERETHE
MINIMUMPERPENDICULARREFLECTANCEOCCURS. NEXTTHEMODELIDENTIFIESTHECLUSTER-TO-BULKSURFACEAREA
RATIOOFTHEMATERIALANDFORMULATESTHECONTRIBUTIONOFREFLECTIONFROMTHESEAREASBYUTILIZINGTHE
FRESNELEQUATIONS. REFLECTANCEFROMTHEREMAINDER,THEBULK SURFACEAREA,ISCOMPUTEDBYAPPLYING
CONVENTIONALMETALLICREFLECTIONTECHNIQUES. BYCOMBININGTHETWOCONTRIBUTIONSOFREFLECTANCEFOR
ANGLESOFINCIDENCEFROM TO90DEGREES,REFLECTANCECURVESAREGENERATEDFORGOLD,SILVER,NICKELAND
ALUNIMUM. THESECALCULATIONSASSUMEAWIDE-BANDRADIATINGSOURCEOFLIGHT. ALTHOUGHTHE MAGNITUDEOF
REFLECTANCEFORTHE MODELSHOWEDSOMEVARIANCEOVERTHERANGEOFANGLESOFINCIDENCE(1WITHIN 10%),THE
CURVESARESILMILARINSHAPE. THE MINIMUM PERPENDICULARREFLECTANCEANDGRAZINGANGLESOFINCIDENCEARE
CONSISTENTWITHEXPERIMENTALFINDINGS. THECOMPUTEDSURFACERATIOFOREACH METALVARIESINDIRECTLYWITH
THEMETAL'SNORMALREFLECTANCEVALUE,ASEXPECTEDFROMTHE MODEL. SPECTRALINFORMATIONONTHECOMPLEX
INDEXOFREFRACTIONISINCLUDEDTOINFERPROBABLECLUSTERSIZE.
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Approved for public release; distribution is unlimited.
Cluster Model of
Polarization Upon Reflection
From Metallic Surfaces
by
CraigWesley Baldwin
LieutenantCommander, United States Navy
B.S., Purdue University 1979
Submitted in partial fulfillment
ofthe requirements for the degree of
MASTER OF SCIENCE IN ASTRONAUTICALENGINEERING
from the
NAVAL POSTGRADUATE SCHOOL
December, 1991
n
ABSTRACT
Polarization of light due to metallic reflection is at best only partially explained by current
models. A new model is proposed to account for this phenomenon involving "native clusters".
These clusters are assumed to be an integral part of metallic bulk surfaces and to manifest their
dielectric properties in the visible region. An index of refraction may be computed based on a
pseudo-Brewster angle, that angle of incidence where the minimum perpendicular reflectance
occurs. Next the model identifies the cluster-to-bulk surface area ratio of the material and
formulates the contribution of reflection from these areas by utilizing the Fresnel equations.
Reflectance from the remainder, the bulk-surface area, is computed by applying conventional
metallic reflection techniques. By combining the two contributions of reflectance for angles of
incidence from to 90 degrees, reflectance curves are generated for gold, silver, nickel and
aluminum. These calculations assume a wide-band radiating source of light. Although the
magnitude of reflectance for the model showed some variance over the range of angles of
incidence (within 10%), the curves are similar in shape. The minimum perpendicular reflectance
and grazing angles ofincidence are consistent with experimental findings. The computed surface
ratio for each metal varies indirectly with the metals' normal reflectance value, as expected from
the model. Spectral information on the complex index ofrefraction is included to infer probable
cluster size.
in
.
TABLE OF CONTENTS
DESCRIPTION OF MECHANISMS FOR METALLIC REFLECTION ....
I. 1
INTRODUCTION
A.
1
PRESENT SCOPE OF RESEARCH
B. 1
MECHANISMS OF POLARIZATION
C. 2
1 Free Electron Theory 3
2. Quantum Mechanics 3
3. Polarization Due To "Native Clusters" 4
BACKGROUND ON ELECTROMAGNETIC WAVE BEHAVIOR
II. 6
A. INDEX OF REFRACTION 6
B. FRESNEL EQUATIONS FOR DIELECTRICS 8
C. BREWSTER'S LAW FOR DIELECTRICS 9
D. REFLECTION AND REFRACTION PROPERTIES OF A
CONDUCTOR
10
1. Complex Index Of Refraction 10
FREE ELECTRON AND QUANTUM MODELS
III. 14
A. THE FREE ELECTRON MODEL OF METALLIC REFLECTION 14
.
IV