Magnetoplasma reflection beam isolators for submillimeter wave use are discussed. The basic configuration used is that of the Kerr transverse magneto-optical effect. Theoretical and experimental data at 337 microns using InSb as a plasma are given

Kanda, M.

May, W. G.

English

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REFLECTION BEAM ISOLATOR
RE 0PRODUC mAl. di' U2 . FOR SUBMILLIMETER WAVELENGTHS
ORIGINAL PAGE IS POR M. Kandat and W.G. May
Abstract
Magnetoplasma reflection beam isolators for submillimeter wave use are discussed. The
basic configuration used is that of the Kerr transverse magneto-optical effect. Theoretical
and experimental data at 337 pm using InSb as a plasma medium are given.
Introduction Experimental Results
The purpose of this paper is to discuss Experiments were performed at 337 pm using
magnetoplasma reflection beam isolators for n-type InSb as the plasma. The dielectric
use at submillimeter wavelengths. The basic layer was a high density polyethylene film.
geometry chosen has the plane of polarization The block diagram of the experimental
of em waves in the plane of incidence, and apparatus for the measurement of the far-
the direction of propagation is perpendicular infrared non-reciprocal reflection is shown
to a dc magnetic field which is parallel to in Fig. 2.
the surface of the magnetoplasma (Kerr trans-
verse magneto-optical effect, as shown in The theoretical and experimental reflect-
Fig. 1). ion loss from the interface between free space
and dielectric coated InSb at 284
0 K are shown
General Discussion in Fig. 3 for the dc magnetic field of 15 kG
as a function of incident angle, and in
Various studies of this basic geometry Fig. 4 at a fixed angle of 650 as a function
have been made. Barber and Crombiel have of dc magnetic field. The general shapes of
calculated the reflection coefficient from a the curves for the theoretical and experi-
sharply bounded ionosphere and found that the mental r~sults agree fairly well except at
reflection coefficient for em waves propagat-- large incident angles. Errors are accounted
ing from west to east was numerically greater for by the experimental system used.
compared to east-west propagation. A physical
explanation of the non-reciprocity, expanding Conclusion
the ideas of Davies, 2 is based on changes in
the elliptical electron orbits in the plane The theoretical and experimental investi-
of.incidence. Non-reciprocal reflection of gations in this paper were performed to
em waves incident on a solid state magneto- develop a reflection beam isolator for sub-
plasma at 94 GHz was studied by Seaman,
3 but millimeter wavelengths using non-reciprocal
no choice of parameters was found which gave reflection of em waves incident on a semi-
a very large ratio of forward to reverse conductor. At wavelength of 337 pm the
reflection coefficient along with low forward experiments demonstrated 4.1 db isolation
loss, as required for an efficient isolator. with 2 db insertion loss, whereas the theory
predicts 16 db isolation with an insertion
One significant difference between the loss of less than 1 db. Narrowed beam angle
ionospheric case and a solid state mqgneto- should improve experimental performance.
plasma is the presence in the latter of the
large lattice permittivity (KL = 12 to 18 for References
many semiconductors). Two different struct-
ures using the same basic relations of IBarber, N.F. and Crombie, D.D., "V.L.F.
incident electric field, surface plane and Reflections from the Ionosphere in the
magnetic field were considered to improve Presence of a Transverse Magnetic Field",
efficiency: 1) free space replaced by a J. Atmosph. Terr. Phys., Vol. 16, Nos. 1/2,
medium of high dielectric constant, and 2) pp. 37-45 (Oct. 1959).
the surface plane covered with a relatively
thin dielectric. This latter geometry seemed. Davies, K., Ionospheric Radio Waves,
promising in performance and is the one Blaisdell Publishing Co., Waltham (1969).
analyzed here in some detail. Theoretical
results for the various structures will be Seaman, J.M., "Non-Reciprocal Reflection
presented as well as some experimental of Microwaves from a Solid State Magneto-
results at 337 pm. plasma", M.S. Thesis, University of Colorado
(Aug. 1969).
Calculation of Reflection CoefficientCalculation Of Ref ection efficient tNational Bureau of Standards,. Boulder,
The reflection coefficient R is derived Colorado 80302.
for the interface between free space and a ,U
dielectric coated magnetoplasma as shown in University of Colorado, Department of
Fig. 1 using a transmission line impedance Electrical Engineering, Bould o
method. If the plasma is lossless, there 80302. L
will be a change .of phase but no change in
the magnitude of R upon reversal of direction This work was suppor y NASA, ant
of propagation. However, with loss in the No. NGLO6-003-088.
magnetoplasma, the reflection coefficient R ;(0
is found to be non-recinroc al.
(NASA-CR-1407 6l1) REFLECTION BEAM. ISOLATOR N75-11741
FOR SUBMILLIMETER WAVELENGTHS (Colorado
Univ.) 2 p HC $3.25 CSCL 201
Unclas n
https://ntrs.nasa.gov/search.jsp?R=19750003669 2020-03-23T02:59:55+00:00Z
Y
i (CHOPPER (14 c/s)
SHCN LASER - - - ----- MIRROR
PLASMA• ,4 ,
LAMP
S DI CTRI X 0 PHOTO DETECTOR- I S L
Eln~ -0 POWERIn~b -SUPPLY
FIREESPACE
FrT LOCK-IN
AMPLIFIER AMPLIFIER
FIG. 1 Orientations of Field yector FIG. 2 Block Diagram for IR Experimental Set-up
E, Propagation Vector r and
dc Magnetic Field "
REPRODUC±.L
ORIGINAL PAGE IS POOR
20db
-4 EXPERIMENT
6 - THEORY 3 -EP MN
f---4 EXPERIMENT
5 REVERSE 
-- THEORY
_j 4  C 2 REVERSE
o0
2 . FORWARD / FOR
. - 0
Cn-
O t E R I i I M E T30 50 7O 90 0-4 • -8 1"2 I-6
INCIDENT ANGLE (degrees) MAGNETIC FIELD (wb/m')
FIG. 3Theoretical and Experimental FIG. 4 Theoretical and Experimental
33 7 dm as aFunction o f 337ec nm a L c un t on n b at
LMagnetic 
Field
LL ~ FORWARD I
cc _j FORW ARD
0
30 50 70. 90 0-4 0-8 1[2 1-6
INCIDENT ANGLE (degrees) MAGNETIC FI ELD (wb/m t )
FIG. 3 Theoretical and Experimental FIG. 4 Theoretical and Experimental
.Reflection Loss of InSb at Reflection oss for I S7 Pjm a of 337 im as a Function ofIncident Angle Magnetic Field


Reflection beam isolator for submillimeter wavelengths

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