The transmission characteristics of synthesized optical single-pass and double-pass birefringent networks is obtained by measuring network transmission as a function of network temperature. This technique is most useful for testing those birefringent networks whose bandwidths and periods are very small

Ammann, E. O.

Yarborough, J. M.

English

NASA Technical Reports Server

August 1968	 Brief 68-10260 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Technique Developed for Measuring Transmittance of Optical 
Birefringent Networks 
Procedures have previously been developed for syn-
thesizing optical single-pass and double-pass bire-
fringent networks having arbitrary transmission vs 
frequency characteristics. This Tech Brief summarizes 
the results of experiments which were performed on 
these two types of optical networks. A three-stage 
network was tested in the single-pass experiments, 
while three-, five-, and seven-stage networks were 
used in the double-pass experiments. Each stage of 
these networks consisted of a calcite crystal (a natu-
rally occurring birefringent crystal) two centimeters in 
length followed by a quartz compensator. The general 
form of a single-pass network, with electro-optical 
crystals, rather than natural birefringent cyrstals, is 
illustrated in Tech Brief 68-10275. The transmission 
characteristics of the networks were obtained by meas-
uring network transmission (at a fixed optical fre-
quency) as a function of network temperature. 
Since the phase difference between "fast" and 
"slow" axis light components passing through a cal-
cite crystal has the same functional dependence upon 
temperature as upon optical frequency, the transmis-
sion vs temperature characteristic of a birefringent 
network will be the same as the transmission vs fre-
quency characteristic. This relationship gives a very 
convenient, high-resolution method of measuring the 
transmittance of birefringent networks. The excellent 
agreement obtained between the measured transmit- 
tances and the theoretical values serves both as a 
verification of the synthesis procedures, and as a 
demonstration of the utility of the measurement 
technique.
An important advantage of the temperature-tuning 
technique is that no spectrometer is needed. Further-
more, the technique is capable of extremely high reso-
lution, being limited only by the linewidth of the 
illuminating source. If a multi-mode 6328 A He—Ne 
laser is used, for example, a resolution of about 0.02 
A is theoretically possible. If a single-frequency, 
stabilized He—Ne laser were used, resolution would 
be improved by some three orders of magnitude. 
There are some instances, however, in which the tem-
perature-tuning technique may not be practical. It is 
necessary, for example, for the network to tune 
through at least one period of its transmittance while 
the temperature is changed by some reasonable 
amount. For the experiments with the 2-centimeter 
calcite crystals, the network tuned through one 
transmittance period with a temperature change of 
only 3°C. If a network were designed to have a sub-
stantially larger period (either by using shorter calcite 
crystals, or some less birefringent material such as 
quartz), an impractically large temperature change 
might be required to obtain one period of the trans-
mittance. Under these conditions, though, the net-
work bandwidth will probably be great enough to 
allow use of a conventional spectrometer. Finally, if 
a material is employed whose change in birefringence 
with temperature is much less than that of calcite, 
the temperature-tuning technique might also become 
impractical. This technique appears to be most useful 
for testing precisely those birefringent networks which 
are most difficult to test by conventional means; 
namely, those whose bandwidths and periods are very 
(continucd overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000260 2020-03-12T06:12:27+00:00Z
small. Larger (possibly impractical) temperature 
swings would be required by networks designed to 
have greater periods, or by networks employing crys-
tals whose birefringence is very insensitive to temper-
ature. 
Note: 
Complete details may be obtained from: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B68-10260
Patent status: 
No patent action is contemplated by NASA. 
Source: E. 0. Ammann and J. M. Yarborough 
of Sylvania Products, Inc. 
under contract to 
Marshall Space Flight Center 
(M FS-l4267)
. 
. 
. 
Brief 68-10260	 Category 02


Technique developed for measuring transmittance of optical birefringent networks

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